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1
Gusenitsa, Yaroslav N., Aleksandr L. Snegirev, and Sergey A. Pokotilo. "Study of the characteristics of a radio photon device for determining the phase difference of a radar signals." Izmeritel`naya Tekhnika, no. 2 (2021): 38–42. http://dx.doi.org/10.32446/0368-1025it.2021-2-38-42.
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The paper considers the problem of accurate calculation of the phase of the radar signal in relation to the receiving phased antenna arrays. Methods for determining the phase difference based on a comparison of the received signal with the local oscillator signal are listed, as well as a method based on the use of a radio-photon analog-to-digital converter for the output signal of the receiving phased antenna array. Their disadvantages are indicated. A method and a radio photon device are proposed that are devoid of these disadvantages. The method allows you to calculate the phase difference of the radar signal at the output of the electro-optical modulator and the output signal of the photodetector, taking into account the known values of the amplitudes and phase difference of the microwave signals at the input of the receiving elements of the phased antenna array. The radio-photon device allows you to implement this method and, unlike the known analogues, is based on the use of two parallel-connected electro-optical modulators constructed according to the scheme of the Mach-Zehnder interferometer. It is shown that the proposed radio photon device provides a higher accuracy of determining the phase of the radar signal in comparison with existing analogues. At the end of the work, an analysis of the results of experimental studies using the proposed method and a radio photon device is presented. According to the results of the experiment, it was found that the phase and phase differences vary linearly, and their maximum reaches π. In addition, the square of the amplitude of the optical signal at the input of the photon-electronic unit is proportional to the phase difference and inversely proportional to the ratio of the amplitudes of the output signals of the adjacent receiving elements of the phased antenna arrays.
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Artyushenko, V. M., and V. I. Volovach. "Determination of the Probability Density Function of the Mixture Signal and Additive Noise under Influence of Multiplicative Noise." Journal of Physics: Conference Series 2096, no. 1 (November 1, 2021): 012154. http://dx.doi.org/10.1088/1742-6596/2096/1/012154.
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Abstract Issues related to effect of multiplicative (modulating) (otherwise amplitude distortions) and additive noises on processed signal are considered. Analysis of statistical characteristics of probability density function (PDF) of instantaneous signal values against background of modulating interference is carried out. Expressions of the joint PDF envelope, phase and instantaneous signal values are obtained, for the case of only phase distortions, as well as the case when fluctuations in amplitude and phase are independent of each other. It is noted that in the second case, with the independence of phase and amplitude distortions, the PDF of the signal, first of all, is determined by the PDF of its instantaneous values and practically does not depend on the PDF of the signal phase. Expressions are obtained for the PDF useful signal and the most common PDF envelope when affecting the signal with modulating noise for deep phase distortions and for its uniform distribution over the interval (0, 2π). In addition, for the case of some functional relationship of phase and amplitude fluctuations, the expression for PDF instantaneous signal values is defined. The presence of such a functional connection allows calculating the PDF of the signal through the statistical characteristics of its envelope. It is obtained that PDF of mixture of signal and additive noise contains arbitrary distribution of phase and amplitude, as well as arbitrary law of distribution of envelope of processed signal. It is obtained that weight coefficients are determined by derivative of characteristic function of amplitude distortion in case when PDFs of said mixture are distributed according to normal law and functional connection exists between amplitude and phase distortions.
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Chai, Meng Yu, Li Chan Li, Yong Quan Li, Wen Jie Bai, and Quan Duan. "Investigation on Acoustic Emission Characteristics from Q345R during Fatigue Crack Propagation." Applied Mechanics and Materials 331 (July 2013): 61–64. http://dx.doi.org/10.4028/www.scientific.net/amm.331.61.
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The fatigue crack propagation process of specimen made from Q345R was monitored by acoustic emission (AE) equipment. The AE characteristic of the specimen generated during the fatigue crack propagation was obtained by parameter analysis method and wavelet transform method .The results show that the fatigue crack growth curve comprises four phases of the crack generation phase, the low-speed crack propagation phase, the high-speed crack propagation phase and the fracture phase, and the variation of signal parameters presents the similar tendency to the fatigue crack growth rate. The values of signal parameters, such as count, energy, and amplitude, are stable and low in the crack generation phase and low-speed crack propagation phase, and relatively unstable and high in the high-speed crack propagation phase and fracture phase. The type of signals is burst emission and the frequency ranges from 100kHz to 180kHz. From these correlations, it may be possible to predict the remaining service life of a pressure vessel from the results of short-term AE monitoring of crack propagation.
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Xie, Jingsong, Wei Cheng, Yanyang Zi, and Mingquan Zhang. "Phase-based spectrum analysis method for identifying weak harmonics." Journal of Vibration and Control 24, no. 23 (March 16, 2018): 5585–96. http://dx.doi.org/10.1177/1077546318760904.
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Fault characteristic frequency extraction is an important means for the fault diagnosis of rotating machineries. Traditional signal processing methods commonly use the amplitude information of signals to detect damages. However, when the amplitudes of characteristic frequencies are weak, the recognition effects of traditional methods may be unsatisfactory. Therefore, this paper proposes the phase-based enhanced phase waterfall plot (EPWP) method and frequency equal ratio line (FERL) method for identifying weak harmonics. Taking a cracked rotor as an example, the characteristic frequency detection performances of the EPWP and FERL methods are compared with that of the traditional signal processing methods namely fast Fourier transform, short-time Fourier transform, discrete wavelet transform, continuous wavelet transform, ensemble empirical mode decomposition, and Hilbert–Huang transform. Research results demonstrate that the effects of EPWP and FERL for the recognitions of weak harmonics which are contained in steady signals and transient signals are better than that of the traditional signal processing methods. The accurate identification of weak characteristic frequencies in the vibration signals can provide an important reference for damage detections and improve the diagnostic accuracy.
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Akinin, K. P., V. G. Kireyev, I. S. Petukhov, A. A. Filomenko, and E. M. Mihailik. "FREQUENCY CHARACTERISTICS OF BRUSHLESS MAGNETOELECTRIC MOTORS OF RETURN-ROTARY MOTION." Praci elektrodinamiki Nacionalanoi akademii nauk Ukraini Institutu 2020, no. 57 (December 2, 2020): 73–80. http://dx.doi.org/10.15407/publishing2020.57.073.
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n this paper, the frequency characteristics of a special brushless magnetoelectric motor of return-rotary motion with sinusoidal and rectangular forms of the carrier signal are investigated. The method of generating a feedback signal on the amplitude of the rotor shaft oscillations angle has been improved by fixing the value of the signal at the moment of reaching its amplitude. The method of calculating the control system of the oscillations angle amplitude is investigated based on the frequency characteristics of the open-loop system by setting the phase stability margin. Examples of the calculation of transient processes of regulation of the oscillations angle amplitude and the effective value of the stator current when starting the motor and changing the mechanical load are given. References 9, figures 6, tables 2.
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Nguyen, Anh Hong, Michael Rath, Erik Leitinger, Khang Van Nguyen, and Klaus Witrisal. "Gaussian Process Modeling of Specular Multipath Components." Applied Sciences 10, no. 15 (July 29, 2020): 5216. http://dx.doi.org/10.3390/app10155216.
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The consideration of ultra-wideband (UWB) and mm-wave signals allows for a channel description decomposed into specular multipath components (SMCs) and dense/diffuse multipath. In this paper, the amplitude and phase of SMCs are studied. Gaussian Process regression (GPR) is used as a tool to analyze and predict the SMC amplitudes and phases based on a measured training data set. In this regard, the dependency of the amplitude (and phase) on the angle-of-arrival/angle-of-departure of a multipath component is analyzed, which accounts for the incident angle and incident position of the signal at a reflecting surface—and thus for the reflection characteristics of the building material—and for the antenna gain patterns. The GPR model describes the similarities between different data points. Based on its model parameters and the training data, the amplitudes of SMCs are predicted at receiver positions that have not been measured in the experiment. The method can be used to predict a UWB channel impulse response at an arbitrary position in the environment.
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Shi, Lei, Shurong Yuan, and Bo Yao. "Unconventionally Designed Tracking Loop Adaptable to Plasma Sheath Channel for Hypersonic Vehicles." Sensors 21, no. 1 (December 22, 2020): 21. http://dx.doi.org/10.3390/s21010021.
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An aircraft that moves through the atmosphere at hypersonic speed is covered by plasma sheath, which causes random and fast time-varying amplitude attenuation and phase fluctuation in received signals. This paper comprehensively analyzes the mechanism of the amplitude attenuation effects on a traditional phase-locked loop (PLL), which is always ignored in traditional scenarios (such as satellite telemetry and vehicle communication). Simulation results and theoretical analysis showed that traditional PLL does not work reliably for signal carrier tracking with the severe time-varying amplitude attenuation of the plasma sheath channel. In this paper, an unconventionally designed Kalman filter (KF) tracking loop that is aware of phase dynamics and amplitude attenuation fluctuation for hypersonic vehicles is proposed. To introduce time-varying amplitude attenuation into the proposed KF-based tracking loop, the amplitude attenuation is first modeled with an autoregressive model. The statistical characteristics of the amplitude and phase fluctuation are then incorporated into the state equation and observation equation. Simulation results indicate that the proposed tracking loop is stable when the signal-to-noise ratio is −10 dB with the Ka band, even in the most severe flight environment for hypersonic vehicles.
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Yu, Liang Jun, Li Hua Sun, and Cui Cui Huang. "Design of Comprehensive Test Instrument Based on FPGA and Cortex-M0." Applied Mechanics and Materials 312 (February 2013): 583–87. http://dx.doi.org/10.4028/www.scientific.net/amm.312.583.
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The design consists of three modules: the voltage amplitude measurement module, the level oscillator module and the amplitude-frequency characteristic test module. The voltage amplitude measurement module uses AD817 to consist three-stage amplifier. The magnification of each level can be adjusted for 1 times/10 times. At the same time, the author uses the Cortex-M0 for controlling the relay switch to achieve automatic range conversion. The principle of DDS is adopted in the level oscillator module. FPGA is used for realizing the phase accumulator, the phase modulator, the sine ROM look-up table. Digital signal is finally outputted by high-speed analog-to-digital conversion chip DAC900. Then, by controlling the 6-channel relay switch to make the magnification in the amplifying circuit,which can be adjusted step-by-step from-30dB to 20dB. Through outputting sine wave whose amplitude is fixed, but frequency is variable to the network under test, amplitude-frequency characteristic test module measures the relation betthe authoren the amplitude change of the output signal and the signal frequency to obtain the amplitude-frequency characteristics of the network under test..
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Kan, Valery, Michael E. Gorbunov, and Viktoria F. Sofieva. "Fluctuations of radio occultation signals in sounding the Earth's atmosphere." Atmospheric Measurement Techniques 11, no. 2 (February 6, 2018): 663–80. http://dx.doi.org/10.5194/amt-11-663-2018.
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Abstract. We discuss the relationships that link the observed fluctuation spectra of the amplitude and phase of signals used for the radio occultation sounding of the Earth's atmosphere, with the spectra of atmospheric inhomogeneities. Our analysis employs the approximation of the phase screen and of weak fluctuations. We make our estimates for the following characteristic inhomogeneity types: (1) the isotropic Kolmogorov turbulence and (2) the anisotropic saturated internal gravity waves. We obtain the expressions for the variances of the amplitude and phase fluctuations of radio occultation signals as well as their estimates for the typical parameters of inhomogeneity models. From the GPS/MET observations, we evaluate the spectra of the amplitude and phase fluctuations in the altitude interval from 4 to 25 km in the middle and polar latitudes. As indicated by theoretical and experimental estimates, the main contribution into the radio signal fluctuations comes from the internal gravity waves. The influence of the Kolmogorov turbulence is negligible. We derive simple relationships that link the parameters of internal gravity waves and the statistical characteristics of the radio signal fluctuations. These results may serve as the basis for the global monitoring of the wave activity in the stratosphere and upper troposphere.
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Lysenko, Iu Iu, Yu V. Kuts, V. M. Uchanin, and V. F. Petryk. "Research of oscillation mode in automated pulsed eddy current testing systems." Information extraction and processing 2021, no. 49 (December 17, 2021): 9–18. http://dx.doi.org/10.15407/vidbir2021.49.009.
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The formation and analysis of eddy current probe signals obtained in pulsed excitation mode is considered. The proposed method of implementing pulsed eddy current testing with the formation of attenuating harmonic oscillations is more resistant to the effects of noise and interference that accompany the process of inspected object parameters evaluation. The equivalent scheme of the system “test object–eddy current probe” is developed and analyzed. The obtained mathematical model of the eddy current probe signals allowed proposing the natural frequency and the attenuation as informative signals parameters, which are determined from signals phase and amplitude characteristics. Developed algorithm and the proposed methodology was implemented for evaluation of eddy current signals parameters and related characteristics of testing objects. This method was experimentally verified on a series of different test specimens. The obtained results confirm the possibility to apply the proposed informative signals to solve some problems concerned with automated eddy current testing. The formation and analysis of eddy current probe signals obtained in pulsed excitation mode are considered. The proposed method of implementing pulsed eddy current testing with the formation of attenuating harmonic oscillations is more resistant to the effects of noise and interference that accompany the process of automated eddy current testing. The equivalent scheme of the system “test object–eddy current probe” is developed and analyzed. The obtained mathematical model of the eddy current probe signals allows proposing the natural frequency and the attenuation as informative signals parameters, which are determined from signal phase and amplitude characteristics. Methods of increasing the accuracy of determining the eddy current probe signals attenuation and frequency using trends of signals phase and amplitude characteristics are considered. The proposed signal processing method was verified by modeling the process of determining the eddy current probe signals attenuation and the frequency from the signal with Gaussian noise. Algorithmic and software were developed based on the simulation results and the proposed improved methodology was implemented for determining signals parameters and related parameters and characteristics of testing objects.
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Zhang, Meng-Ke, Guo-Peng Fan, Wen-Fa Zhu, Shu-Bin Zheng, Xiao-Dong Chai, Wei-Lv, and Hui-Zhang. "Multi-defect detection based on ultrasonic Lamb wave sign phase coherence factor imaging method." Insight - Non-Destructive Testing and Condition Monitoring 63, no. 11 (November 1, 2021): 659–66. http://dx.doi.org/10.1784/insi.2021.63.11.659.
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The ultrasonic Lamb wave total focusing method (TFM) only uses the amplitude of the defective scattered signal for virtual focused imaging, while ignoring the phase information of the scattered signal and the dispersion characteristics of the Lamb wave, resulting in low imaging resolution and easily produced artefacts in imaging. To solve this problem, an ultrasonic Lamb wave imaging method based on phase coherence is proposed in this paper and the sign coherence factor (SCF) in the full matrix scattering signal is extracted. Moreover, the method uses the SCF to weight the amplitude of the full matrix scattering signal, suppresses the side lobes of the defect echo signal and the Lamb wave dispersion effect, improves the ultrasonic Lamb wave imaging resolution and weakens the artefacts. Finally, single- and multiplehole defects in aluminium plates are detected for experimental validation using an ultrasonic phased array. The array performance indicator and signal-to-noise ratio are used as indicators for quantitative assessment of imaging performance. The results show that compared with the TFM imaging, the SCF imaging can effectively suppress the noise and scattered signal side lobes, improve the array performance indicator (API) by 69.1% and improve the signal-to-noise ratio (SNR) by 73.9%. In addition, the SCF imaging can effectively weaken the interference of scattered signals between multiple through-hole defects, resulting in fewer artefacts in imaging.
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Kravcov, Alexander N., Adam Konvalinka, Vladimir A. Vinnikov, Elmira A. Ertuganova, Ivan A. Shibaev, and Pavel N. Ivanov. "On the Issue of Typical Grain Size Assessment by the Methods of Broadband Laser Opto-Acoustics." Key Engineering Materials 755 (September 2017): 212–18. http://dx.doi.org/10.4028/www.scientific.net/kem.755.212.
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It is shown that one of the express-methods for studying the internal structure and phase composition of geomaterial samples is broadband acoustic spectroscopy with laser sources of ultrasound. Theoretical assessment of time profiles and spectrums of opto-acoustic signals are presented. Numerical modelling of the spectrums and time profiles of ultrasound signals generated in opto-acoustic generators made of a different material is performed. The influence of diffraction and damping in rocks on the above characteristics is studied. The amplitude spectrum and time profiles of ultrasonic pulses transmitted through samples of marble of various thicknesses in which the most part of the characteristic grain sizes lies in the range of 500 μm - 1 mm are constructed. It has been established that, according to the amplitude spectrum of the original signal and the transmitted through the sample signal, it is possible to restore the characteristic dimensions of the grains.
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Sotelo-Castañón, Julián, José Alberto Gutiérrez-Robles, Brian Johnson, Pablo Moreno, and Armando Guzman. "Time domain parameter identification of transient electromechanical oscillations." COMPEL - The international journal for computation and mathematics in electrical and electronic engineering 38, no. 2 (March 4, 2019): 574–95. http://dx.doi.org/10.1108/compel-11-2017-0475.
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Purpose The power systems behavior is nonlinear, and this is reflected in that the measurement signals are composed by multi-components. Thus, this paper aims to present a method for analyzing multi-component signals that allow calculating signal parameters such as frequency, damping constant, amplitude and phase for each component, as well as determining the direct current component. Design/methodology/approach The method proposed is based in the Z-transform of a damped sinusoidal signal with direct current. Only the Z-transform poles are used to form equation systems which are used to obtain frequency and damping. Then, the amplitude, the phase and the direct current component are determined by the above results. Findings The method is able to determine frequencies, damping constants, phases and amplitudes of the different modal components of a signal using only a few measurements. Moreover, the method does not require filter banks tuned with some previous knowledge of signal’s characteristics. The presented test cases of field measured signals show the good performance of the proposed method, which is able to obtain the parameters of interest with a very short observation window. Originality/value One quality of this method is that it has a very short delay to reach the first solution and from there you get one result each sample; the delay time is equivalent to 2 + 4C samples where C is the number of components in the signal. Finally, it is concluded that because of the small number of samples that are needed and the low algorithmic complexity of the methodology, the method is apt to make applications in real time.
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Chen, Zai Xiu. "Research on Boundary of Active Cancellation Engineering Realization." Applied Mechanics and Materials 602-605 (August 2014): 3148–51. http://dx.doi.org/10.4028/www.scientific.net/amm.602-605.3148.
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The key of the active cancellation is obtaining correctly the amplitude and phase of the target echo, and also is controlling precisely the amplitude and phase of the jamming signal. This article analyzes the characteristics of all kinds of platform’s RCS and geometrical features, combining with the measured data of projects, to get the application boundary of active cancellation. It raises the following 4 points: use of the RCS model in cancellation should consider the time characteristics; trying to control processing time-delay and channel time-delay of the jamming signals; during operation of equipment’s temperature must be relatively stable; the installing platform is the smaller, the more favorable.
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Eremenko, Volodymyr, Artur Zaporozhets, Vitalii Babak, Volodymyr Isaienko, and Kateryna Babikova. "Using Hilbert Transform in Diagnostic of Composite Materials by Impedance Method." Periodica Polytechnica Electrical Engineering and Computer Science 64, no. 4 (August 13, 2020): 334–42. http://dx.doi.org/10.3311/ppee.15066.
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The article is devoted to the problem of the increasing of information quality for the impedance method of nondestructive testing. The purpose of this article is to get for the pulsed impedance method of nondestructive testing the additional informative parameters. Instantaneous values of the information signal's amplitude is a sensitive parameter to the effects of interference, in particular friction, which necessitates the use of additional informative features. It was experimentally measured signals from defective and defectless areas of the test pattern. Using of the Hilbert transform gave possibility to determine phase characteristics of these signals and realize demodulation to extract a low-frequency envelope for further analysis of its shape. It was received the informative features as a result of researches. Among them are instantaneous frequency of a signal, the integral of a phase characteristic on the selected interval and the integral of a difference signal phase characteristics. In order to compare quality of the defect detection using selected parameters it was carried out evaluation of the testing result reliability for a product fragment made of a composite material. Considering the influence of the change in the mechanical impedance of the researched area on the phase-frequency characteristics of the output signal of the converter, it is proposed to use as the diagnostic signs: the instantaneous frequency and the value of the phase characteristic of the current signal for certain points in time. The proposed informative features enable to increase general reliability of composite materials testing by the pulsed impedance method.
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Cui, An-Jing, Dao-Jing Li, Jiang Wu, Kai Zhou, and Jing-Han Gao. "Sparse sampling in frequency domain and laser imaging." Acta Physica Sinica 71, no. 5 (2022): 058705. http://dx.doi.org/10.7498/aps.71.20211408.
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The monochromaticity of the laser and the characteristics of the natural image’s spectrum, including sparsity and concentrating in the low frequency range, make it possible to sample the image spectrum sparsely. Based on small-scale laser detectors and the introduced laser reference signals, a method of laser imaging with sparse sampling in frequency domain is proposed in this paper. The principle of frequency sparse sampling laser imaging and the imaging system structure are introduced. The simulation results of spectrum and complex images reconstructed are given. Both the effects of the signals’ parameters, such as the ratio of the reference laser signal amplitude to the laser echo spectrum amplitude and the initial phase of the laser reference signal, on reconstruction results are investigated. The reconstruction results are evaluated by correlation coefficient, mean square error (MSE), and structural similarity index (SSIM). For the strong correlation between phase and amplitude of the laser echo complex image, the amplitude image and the phase image are both set to be 256 × 256 diagram. The sparse laser detector plane array consists of 5 64 × 64 frequency domain laser detector arrays, which form a cross and make a sparsity rate of 31.25%(5/16). The simulation results show that the correlation coefficient, MSE and SSIM of the spectrum reconstructed are 0.96, 22.14, 1.00 and those of the complex image reconstructed are 0.96, 1857.25 and 0.67 respectively. The simulation results indicate that the method proposed is effective. However, the method requires the laser reference signal amplitude to be about 30 times the mean value of the laser echo spectrum amplitude, which reduces the dynamic range of the detectors. The initial phase of the laser reference signal has no obvious effect on the reconstruction results.
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Dang, Xiaochao, Xiong Si, Zhanjun Hao, and Yaning Huang. "A Novel Passive Indoor Localization Method by Fusion CSI Amplitude and Phase Information." Sensors 19, no. 4 (February 20, 2019): 875. http://dx.doi.org/10.3390/s19040875.
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With the rapid development of wireless network technology, wireless passive indoor localization has become an increasingly important technique that is widely used in indoor location-based services. Channel state information (CSI) can provide more detailed and specific subcarrier information, which has gained the attention of researchers and has become an emphasis in indoor localization technology. However, existing research has generally adopted amplitude information for eigenvalue calculations. There are few research studies that have used phase information from CSI signals for localization purposes. To eliminate the signal interference existing in indoor environments, we present a passive human indoor localization method named FapFi, which fuses CSI amplitude and phase information to fully utilize richer signal characteristics to find location. In the offline stage, we filter out redundant values and outliers in the CSI amplitude information and then process the CSI phase information. A fusion method is utilized to store the processed amplitude and phase information as a fingerprint database. The experimental data from two typical laboratory and conference room environments were gathered and analyzed. The extensive experimental results demonstrate that the proposed algorithm is more efficient than other algorithms in data processing and achieves decimeter-level localization accuracy.
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Boronoev, V. V., V. N. Poplaukhin, and E. V. Storchun. "Amplitude-frequency and phase characteristics of pulse signal intensity transducers for multizone pulse diagnosis." Biomedical Engineering 32, no. 2 (March 1998): 96–100. http://dx.doi.org/10.1007/bf02369093.
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Kistanova, V. A., and V. I. Oganov. "Phase control algorithm for demodulation of binary phase-shift keying signals." Radio industry 28, no. 4 (November 27, 2018): 15–20. http://dx.doi.org/10.21778/2413-9599-2018-28-4-15-20.
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The purpose of this paper is to synthesize an algorithm for coherent digital demodulation of non-uniformly distributed radio signals with absolute two-position phase shift keying, which has a small computational complexity, and to develop a miniature low-power demodulator on its basis. The relevance of the study is determined by the absence of similar devices in the Russian radio electronic market. The algorithm is based on digital phase-locked-loop frequency control. Its basic idea is to retain the optimal amplitude ratio between the phase quadrature of the received signal using a proportional-integral- differential controller. A digital device with the stated technical characteristics was obtained as a result of the study.
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Sulic, D. M., and V. A. Sreckovic. "A comparative study of measured amplitude and phase perturbations of VLF and LF radio signals induced by solar flares." Serbian Astronomical Journal, no. 188 (2014): 45–54. http://dx.doi.org/10.2298/saj1488045s.
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Very Low Frequency (VLF) and Low Frequency (LF) signal perturbations were examined to study ionospheric disturbances induced by solar X-ray flares in order to understand processes involved in propagation of VLF/LF radio signals over short paths and to estimate specific characteristics of each short path. The receiver at the Belgrade station is constantly monitoring the amplitude and phase of a coherent and subionospherically propagating LF signal operated in Sicily NSC at 45.90 kHz, and a VLF signal operated in Isola di Tavolara ICV at 20.27 kHz, with the great circle distances of 953 km and 976 km, respectively. A significant number of similarities between these short paths is a direct result of both transmitters and the receiver?s geographic location. The main difference is in transmitter frequencies. From July 2008 to February 2014 there were about 200 events that were chosen for further examination. All selected examples showed that the amplitude and phase of VLF and LF signals were perturbed by solar X-ray flares occurrence. This six-year period covers both minimum and maximum of solar activity. Simultaneous measurement of amplitude and phase of the VLF/LF signals during a solar flare occurrence was applied to evaluate the electron density profile versus altitude, to carry out the function of time over the middle Europe.
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Bychkov, Anatoly V., Irina Yu Bychkova, Nadezhda N. Suslova, and Kurbangali K. Alimov. "NEURAL NET USING TO DETERMINE DEPTH AND FREQUENCY OF SIGNALS’ MODULATION FOR ELECTRICAL EQUIPMENT ULTRASONIC VIBROCONTROL." Vestnik Chuvashskogo universiteta, no. 3 (September 29, 2021): 21–30. http://dx.doi.org/10.47026/1810-1909-2021-3-21-30.
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The apparatus of artificial neural networks (ANN) is proposed to be used for signal processing in active ultrasonic (US) vibration control of electrical equipment. A feature of the applied neural network algorithm is that the required information about vibration parameters is embedded in the ultrasound signal’s phase change at its constant amplitude. Under these conditions, traditional spectral analysis of signals requires a high sampling rate and a significant recording duration. When using the direct propagation’s ANN with three hidden layers, it was shown that it is sufficient to use a sampling frequency of 5-6 points for the period of an ultrasonic wave and a recording duration of 4-5 periods to estimate the nonstationary frequency and amplitude of the vibration signal. Estimates of the error in determining the amplitude, frequency and phase of vibrations are obtained. The root-mean-square errors of the neural network algorithm do not exceed units of percent. The possibilities of using a trained neural network for signal processing in a «sliding window» are demonstrated. The accuracy characteristics of the proposed neural network algorithm of signal processing and the possibility of its optimization for electrical equipment’s vibration control are discussed.
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Arce-Guevara, Valdemar E., Alfonso Alba-Cadena, and Martín O. Mendez. "Study of quadrature FIR filters for extraction of low-frequency instantaneous information in biophysical signals." International Journal of Modern Physics C 28, no. 05 (March 20, 2017): 1750065. http://dx.doi.org/10.1142/s0129183117500656.
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Quadrature bandpass filters take a real-valued signal and output an analytic signal from which the instantaneous amplitude and phase can be computed. For this reason, they represent a useful tool to extract time-varying, narrow-band information from electrophysiological signals such as electroencephalogram (EEG) or electrocardiogram. One of the defining characteristics of quadrature filters is its null response to negative frequencies. However, when the frequency band of interest is close to 0 Hz, a careless filter design could let through negative frequencies, producing distortions in the amplitude and phase of the output. In this work, three types of quadrature filters (Ideal, Gabor and Sinusoidal) have been evaluated using both artificial and real EEG signals. For the artificial signals, the performance of each filter was measured in terms of the distortion in amplitude and phase, and sensitivity to noise and bandwidth selection. For the real EEG signals, a qualitative evaluation of the dynamics of the synchronization between two EEG channels was performed. The results suggest that, while all filters under study behave similarly under noise, they differ in terms of their sensitivity to bandwidth choice. In this study, the Sinusoidal filter showed clear advantages for the estimation of low-frequency EEG synchronization.
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Lysenko, Iuliia, Volodymyr Eremenko, Yurii Kuts, Anatoliy Protasov, and Valentin Uchanin. "Advanced Signal Processing Methods for Inspection of Aircraft Structural Materials." Transactions on Aerospace Research 2020, no. 2 (June 1, 2020): 27–35. http://dx.doi.org/10.2478/tar-2020-0008.
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AbstractAircraft, their assemblies, and units must provide high durability and reliability, and maintain mechanical and technological characteristics throughout the life span of the aircraft. Different elements of aircraft structures work under mechanical loads, over a wide temperature range, with varying degrees of exposure to corrosive environments. Aircraft structural materials have a variation in the characteristics values and require the various testing methods for their inspection.In many NDT methods applied in aviation materials testing, signals that could be represented by a narrowband processes model are used. Known methods of their processing are focused on determining and analyzing the signals amplitude characteristics, but the information resource contained in phase characteristics is not used.In the article, the methodology for signal processing and determining phase characteristics in the time domain are discussed. It is based on the combination of the discrete Hilbert transform and the deterministic and statistical methods of the phase measurement. There are given examples of the application of the methodology for pulsed eddy current testing of electrically conductive materials and products, ultrasonic thickness measurement of products made of materials have significant ultrasonic attenuation, the realization impulse variant of acoustic impedance flaw detection of products made of composite materials. The examples have shown that the proposed signal processing methodology enables to determine new information parameters and signal characteristics for the industry, and extend the scope of known NDT methods.
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Kumar, Vinay, and Sunil Bhooshan. "Design of One-Dimensional Linear Phase Digital IIR Filters Using Orthogonal Polynomials." ISRN Signal Processing 2012 (October 16, 2012): 1–7. http://dx.doi.org/10.5402/2012/870276.
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In the present paper, we discuss a method to design a linear phase 1-dimensional Infinite Impulse Response (IIR) filter using orthogonal polynomials. The filter is designed using a set of object functions. These object functions are realized using a set of orthogonal polynomials. The method includes placement of zeros and poles in such a way that the amplitude characteristics are not changed while we change the phase characteristics of the resulting IIR filter.
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Yang, Yang, Yi Qun Wang, and Zeng Wang Zhang. "Roll Eccentricity Phase Identification System." Advanced Materials Research 562-564 (August 2012): 987–92. http://dx.doi.org/10.4028/www.scientific.net/amr.562-564.987.
Full textAbstract:
Roll eccentricity is widespread in the strip mill, has cyclical impact on strip thickness, so disturbance compensation is required to improve the product quality. The key step of disturbance compensation is to obtain reliable roll eccentricity signal. Existing direct measurements of roll eccentricity signal method requires special equipments with high precision but not practical enough. There are few detection methods which including rolling velocity. Roll eccentricity signal is difficult to directly measured, should fuse many kinds of detectable signal to be extracted through the data analysis which includes rolling force, roll gap, incoming thickness of rolled piece, exit thickness, tension, and so on. This paper puts the four high mill as an object, according to the influence of the main factors of roll eccentricity ——backup-roll eccentricity for analysis, develops a Roll Eccentricity Phase Identification System. This system extracts from amplitude of eccentricity signal, combines eccentricity signal’s frequency with phase through roll segmentation marker integrating rolling speed, according to its cyclical change law to achieve the signal calibration by testing amplitude characteristics to determine the phase of roll eccentricity of the current rolling area. After determining the signal phase, detect the phase of eccentricity signal according to integration of rolling speed, and through phase detection to ensure the reliability of the detectable phase. This system is verified by the experiment in four high mill, the results show that the method of phase detection of eccentricity is effective, it provides a simple and effective new way for the phase extraction of roll eccentricity signal, and can used in similar condition.
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Xu, Xiaolong, Xilong Wang, Jingnan Liu, and Qile Zhao. "Characteristics of BD3 Global Service Satellites: POD, Open Service Signal and Atomic Clock Performance." Remote Sensing 11, no. 13 (July 1, 2019): 1559. http://dx.doi.org/10.3390/rs11131559.
Full textAbstract:
The Chinese BeiDou Navigation Satellite System has provided a global-coverage service since 27 December 2018. Eighteen BD3 MEO satellites have been launched into space during 2017 and 2018. The signal constitution has been redesigned and four open service signals are used for transmission, including B1I, B1C, B2a and B3I. This paper focuses on the signal performance, Precise Orbit Determination (POD) and the atomic clock’s frequency stability issues of the BD3 satellites. The satellite-induced code bias issue found in BD2 satellites multipath combination has been proven to be eliminated in BD3 satellites. However, the pseudorange code of B1C is much noisier than that of other three frequencies, which may be related to the signal constitution and power distribution, as the minimum received power levels on the ground of B1C is 3 dB lower than that of the B2a signal. Similar results were achieved by the Ionosphere-Free combination residuals in POD using four signals, B1I-B3I, B1I-B2a, B1C-B3I and B1C-B2a, and the phase residual of B1C-B2a combination performed best. Considering the noise amplitude and compatibility with other GNSS (Global Navigation Satellite System), the B1C-B2a combination is recommended in priority for precise GNSS data processing. GFIFP combinations were also implemented to evaluate the inter-frequency phase bias of the four signals. The experimental results showed that the systematic signal with an amplitude of about 2 cm could be found in the GFIFP series. In addition, multi-GNSS POD was performed and analyzed as well, using about a hundred global-distributed IGS and iGMAS stations. Furthermore, the atomic clock’s frequency stability was estimated using the parameters of clock bias calculated in POD and the Overlap Allan Deviations showed that the frequency stability of BD3 reached approximately 2.43 × 10−14 at intervals of 10,000 s and 2.51 × 10−15 at intervals of 86,400 s, which was better than that of the GPS BLOCK IIF satellites but worse than that of Galileo satellites.
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Zaitsev, Valery V., and Alexander V. Karlov. "The dynamics of synchronization of two-stage van der Pol generator." Physics of Wave Processes and Radio Systems 24, no. 3 (November 18, 2021): 56–62. http://dx.doi.org/10.18469/1810-3189.2021.24.3.56-62.
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Results of numerical simulation of self-oscillations synchronization process in two-cascade ring generator van der Pol by harmonic signal are presented. Studies were carried out within the framework of the DT- model of the dynamic system. The model was developed on the basis of the principle of compliance within the framework of the method of slowly changing amplitudes of characteristics of a discrete system with characteristics of an analog prototype. Shortened equations for complex oscillation amplitudes in generator stages are obtained. It was found that in an autonomous system there is an effect of bistability of amplitudes. In the synchronization mode with an external harmonic signal, solutions of shortened equations made it possible to calculate amplitude-frequency and phase-frequency characteristics of synchronous oscillations. It is shown that transitions between bistable states are observed in the synchronous oscillation holding band. Differences of frequency characteristics of synchronization of classical and two-stage oscillators van der Pol were analyzed.
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Yang, Yuan, Jian Gang Bi, Hong Jie Wang, and Nan Meng. "Study of the Ultrasonic Characteristics of Typical Partial Discharge on GIS." Advanced Materials Research 753-755 (August 2013): 2200–2207. http://dx.doi.org/10.4028/www.scientific.net/amr.753-755.2200.
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This Paper studied the typical PD in GIS by ultrasonic method. A GIS PD simulating and testing system is established, including a PD simulating system, an ultrasonic detecting system and a conventional pulse current method measurement system. The thesis focuses on four typical kinds of PD signals in GIS, including metal particles, bad contacts on high and grounding potential conductor, the protrusion on the high potential conductor. The statistics characteristics are obtained which include N-Φ spectrogram (relationship between discharge frequency and discharge phase Spectrogram) and Umax-Φ spectrogram (relationship between discharge amplitude and discharge phase Spectrogram). Experimental results show that low-frequency ultrasonic sensors can detect this four PD signals， signal spectra analysis shows that ultrasonic signals of different statistical model are with different characteristics. The results provide test data for the pattern recognition of Partial Discharge in GIS.
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Nina, Aleksandra, Pier Francesco Biagi, Srđan T. Mitrović, Sergey Pulinets, Giovanni Nico, Milan Radovanović, and Luka Č. Popović. "Reduction of the VLF Signal Phase Noise Before Earthquakes." Atmosphere 12, no. 4 (March 31, 2021): 444. http://dx.doi.org/10.3390/atmos12040444.
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In this paper we analyse temporal variations of the phase of a very low frequency (VLF) signal, used for the lower ionosphere monitoring, in periods around four earthquakes (EQs) with magnitude greater than 4. We provide two analyses in time and frequency domains. First, we analyse time evolution of the phase noise. And second, we examine variations of the frequency spectrum using Fast Fourier Transform (FFT) in order to detect hydrodynamic wave excitations and attenuations. This study follows a previous investigation which indicated the noise amplitude reduction, and excitations and attenuations of the hydrodynamic waves less than one hour before the considered EQ events as a new potential ionospheric precursors of earthquakes. We analyse the phase of the ICV VLF transmitter signal emitted in Italy recorded in Serbia in time periods around four earthquakes occurred on 3, 4 and 9 November 2010 which are the most intensive earthquakes analysed in the previous study. The obtained results indicate very similar changes in the noise of phase and amplitude, and show an agreement in recorded acoustic wave excitations. However, properties in the obtained wave attenuation characteristics are different for these two signal parameters.
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Qian, Yong, Xiaoxin Chen, Yiming Zang, Hui Wang, Gehao Sheng, and Xiuchen Jiang. "Amplitude Distribution of Partial Discharge Signals on Tunnel-Installed High-Voltage Cables." Applied Sciences 9, no. 21 (October 29, 2019): 4595. http://dx.doi.org/10.3390/app9214595.
Full textAbstract:
For 110 kV and above tunnel-installed high-voltage (HV) cross-linked poly-ethylene (XLPE) cable systems, it is a normal procedure to adopt a cross-bonding scheme. The high-frequency current method is frequently used in the cross-bonded cable systems for on-site or online partial discharge (PD) detection by monitoring the signals on the cross-bonding wires. To further study the amplitude distribution characteristics of the PD signals, a parametric characteristic admittance model of a three-phase cable system in a tunnel is established based on Tylavsky’s formulas. The model is used to calculate the amplitude distribution formula of the PD pulse current on the cross-bonding wires. In addition, the influence of cable laying and tunnel environment on the amplitude distribution is also studied. Finally, the correctness of the model and the conclusion are verified by simulation experiments and on-site tests. The results show that the signal amplitude distribution is determined by the ratio of the characteristic admittances. As the distance between the cables and the distance from the inner wall of the tunnel increase, the amplitude difference gradually decreases.
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BARAS, S., L. KRUPELNITSKYI, and O. ONYSCHUK. "MEASUREMENT OF NARROWBAND RESISTANCE FREQUENCY RADIO SIGNAL OF LIMITED DURATION." HERALD OF KHMELNYTSKYI NATIONAL UNIVERSITY 295, no. 2 (May 2021): 56–63. http://dx.doi.org/10.31891/2307-5732-2021-295-2-56-63.
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The work concerns analog-digital systems that work with radio signals emitted and received by the antenna, and these signals have a limited duration, ie are pulsed. The propagation conditions of such signals and the processes of formation of echo signals affect their amplitude, frequency and phase characteristics in such a way that they form classical narrowband signals. The operation of the system involves the determination of certain parameters of echo signals, and taking into account their pulse nature for such a definition is given a limited time interval. This means that the procedure for determining the parameters must meet the criterion of high speed, and therefore differ from the traditional, built on the use of phase-locked loop. The article is devoted to solving the problem of measuring the reference frequency of a pulsed narrowband radio signal. By analyzing the results of experimental studies, two types of errors in measuring the reference frequency of a narrowband radio signal were identified and the causes of their occurrence were established. These errors are provoked by the peculiarities of the structure of the narrowband signal. The reason for the error of the 1st type, the absolute value of which correlates with the duration of the half-cycle of the reference frequency, is the so-called phase jumps at the point of change of the sign of the bypass. The frequency of such errors within the duration of the echo signal is generally low, although it increases with increasing signal spectrum width. Type 2 errors occur due to the appearance of zones with almost completely suppressed signal amplitude, which may be the result of intrapulse interference and / or signal attenuation. Such errors also occur more often if the spectrum width is larger. A method for measuring the reference frequency of a narrowband pulsed radio signal is proposed, which is based on counting the number of half-cycles of the reference frequency on a time-limited measurement interval and removing from this procedure areas with completely suppressed signal amplitude. An auxiliary highly stable reference frequency is used to establish the numerical value of the reference frequency. The block diagram of the frequency meter and the algorithm of its operation are given, the implementation of which avoids these errors.
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Shao, Yang Zhou, Hai Zhang, and Yue He Ge. "Design of Signal Generator Based on DDS Technology." Advanced Materials Research 846-847 (November 2013): 488–92. http://dx.doi.org/10.4028/www.scientific.net/amr.846-847.488.
Full textAbstract:
Traditional signal generators use analog oscillator circuit as the source, which often involve multiplication, integral and differential circuit. As this method required high electrical parameters of the system, and its complex circuit structure is vulnerable to outside interference. In this paper, a new technology named Direct Digital Synthesizer, DDS technology, was applied on a FPGA chip to design a waveform generator. It can generate periodic waveform, and its frequency, phase and amplitude were adjustable. Simultaneously, DDS technology has the function of frequency and phase adjustment, so no additional circuit was needed. During the amplitude modulation design, the characteristics of reference voltage of the D/A Converter are used. The theoretical and experimental results show that the combination of DDS technology and FPGA can well generate the periodic signal waveforms, while the hardware system fabricated has strong capability of anti-jamming.
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Wang, Si Qi, Xi Wen Chen, Zi Juan Guo, and Xu Wang. "Research on Frequency Conversion ＆ Selective Measurement and Error Correction Algorithms in Grounding Characteristics Measuring System." Advanced Materials Research 605-607 (December 2012): 1068–73. http://dx.doi.org/10.4028/www.scientific.net/amr.605-607.1068.
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The paper concerns algorithms error and parameters correction technology of frequency conversion＆selective measurement in grounding characteristics measuring system. It analyzes estimation method of signal amplitude phase based on Fourier transform, calculates the sensitive degree of the method to frequency error, and also presents several major parameters for the algorithm, including sampling rate, data length and selection condition of frequency resolution in order to meet the high precision measurement requirements. Furthermore, the paper analyzes correction algorithm of amplitude and phase error caused by unknown nonlinearity of circuit during the practical measurement.
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Wang, Kui, Xue Li, Zheng Huang, and Mingjie Zhao. "Experimental Study on Acoustic Emission and Resistivity Response of Sandstone under Constant Amplitude Cyclic Loading." Advances in Materials Science and Engineering 2021 (March 8, 2021): 1–13. http://dx.doi.org/10.1155/2021/6637200.
Full textAbstract:
A lot of engineering practice shows that, during the construction and operation of rock mass projects, in addition to the static load, the rock is more subjected to cyclic load. Constant amplitude cyclic load is one of the simpler cyclic loading methods. The damage of rocks gradually accumulates under the action of periodic cyclic load, and finally, fatigue damage occurs, which affects the stability of the project. Therefore, it is necessary to study the mechanical properties of the rock under the action of constant amplitude cyclic load. Acoustic emission (AE) parameters and resistivity are both sensitive to the damage process of the rock and can well describe the damage evolution law of the rock. Under the action of constant amplitude cyclic loading, different loading conditions, different state specimens, and so on, factors will make a big difference to the AE signal and resistivity, such as the difference in stress amplitude, loading rate, and saturation. Therefore, in this paper, the typical sandstone in the Chongqing area is taken as the research object, the AE characteristics and resistivity characteristics of sandstone under different test conditions such as different stress amplitude, different loading frequency, and different saturation are tested, and the evolution of AE is found. It also has a three-stage rule: in the initial stage, the deformation is faster and the AE signal is strong; in the constant velocity stage, the deformation develops slowly and the AE signal is also stable; in the acceleration stage, the deformation develops sharply and the AE signal also becomes more intense. With the increase of cyclic loading stress amplitude, or the decrease of cyclic loading frequency, or the decrease of rock sample saturation, the acoustic emission signal generated in each cycle will be stronger. The resistivity as a whole shows a rapid decline in the loading phase and a rapid rebound in the unloading phase. The changes in resistivity at different stress amplitudes show differences in the first few cycles; the overall change trend of resistivity at different frequencies is consistent, but the rate of change increases with decreasing frequency, and the variation trend of resistivity is very different under different saturation.
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Tyshko, S., O. Lavrut, V. Smolar, O. Zabula, and Yu Chernichenko. "Application of spectral analysis for determine the phase shift of signals with equal amplitudes using full-wave transformation when measuring the characteristics of weapons." Military Technical Collection, no. 25 (December 8, 2021): 12–23. http://dx.doi.org/10.33577/2312-4458.25.2021.12-23.
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The article defines the list of technical characteristics of armaments and military equipment (ARM), the value of which is measured using phase methods. An analysis of known methods that have found wide application in measuring technology, which is designed to determine the technical characteristics associated with the measurement of phase shift during the development, manufacture and operation of weapons. Based on this analysis, it was determined that the measuring systems are designed to determine the phase shift of two harmonic signals in their composition have two channels of information transmission. This architecture of the implementation of measuring systems leads to the fact that a significant impact on the accuracy of the proposed measurement problem, makes a component of the error due to the phase symmetry of the signal transmission channels, as well as internal and external noise. As an alternative approach to solving the measurement problem of determining the phase shift of two harmonic signals, which will significantly reduce the error component due to phase asymmetry of information transmission channels, it is proposed to use the signal obtained by summing harmonic signals after full-wave transformation followed by spectral analysis. In order to implement the above approach, a measurement problem was set to determine the phase shift of two harmonic signals, using spectral analysis of the signal obtained by summing the harmonic signals after their full-wave transformation. A list of assumptions required for the synthesis of analytical relations that establish the relationship between the spectra of phases and amplitudes (power) of the signal obtained by summing harmonic signals after their full-wave transformation and phase shift of two harmonic signals. Analytical relationships are proposed that establish the relationship between the above characteristics. It is shown that the values of the spectrum of phases and amplitudes, which are calculated using the proposed expressions, differ from the values obtained in the calculations using the Fourier series coefficients, not more than 0.1%.
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Peterie, Shelby L., Richard D. Miller, Julian Ivanov, and Steven D. Sloan. "Shallow tunnel detection using SH-wave diffraction imaging." GEOPHYSICS 85, no. 2 (January 30, 2020): EN29—EN37. http://dx.doi.org/10.1190/geo2018-0731.1.
Full textAbstract:
Clandestine tunnels, used for drug or human trafficking and tactical operations, pose a security threat worldwide and remain elusive targets for detection with geophysical methods. P-wave diffraction imaging is an increasingly common technique for detecting subsurface discontinuities that are smaller than the seismic wavelength (such as faults, pinch outs, and small voids) and has been successfully used to detect shallow tunnels. P-wave diffractions from tunnels typically have very low signal-to-noise ratios and are therefore challenging wavefield components for imaging. Mode-specific amplitude characteristics of theoretical diffractions from a shallow tunnel were evaluated using 9C seismic modeling. Results indicate that SH-wave diffraction has the largest amplitude and coherent phase characteristics along the traveltime hyperbola, making it ideal for diffraction imaging. In real data acquired over a 9.2 m deep tunnel, amplitudes of SH-wave diffractions are 20 dB greater than P-wave diffractions. The tunnel signature on the P-wave diffraction section is of low amplitude relative to the background. The SH-wave diffraction section has a high-amplitude signal focused at the horizontal location and a traveltime consistent with the tunnel location, indicating that the SH-wave may be optimal for diffraction imaging to detect shallow tunnels.
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Chen, Xiang, Jingchao Li, Hui Han, and Yulong Ying. "Improving the signal subtle feature extraction performance based on dual improved fractal box dimension eigenvectors." Royal Society Open Science 5, no. 5 (May 2018): 180087. http://dx.doi.org/10.1098/rsos.180087.
Full textAbstract:
Because of the limitations of the traditional fractal box-counting dimension algorithm in subtle feature extraction of radiation source signals, a dual improved generalized fractal box-counting dimension eigenvector algorithm is proposed. First, the radiation source signal was preprocessed, and a Hilbert transform was performed to obtain the instantaneous amplitude of the signal. Then, the improved fractal box-counting dimension of the signal instantaneous amplitude was extracted as the first eigenvector. At the same time, the improved fractal box-counting dimension of the signal without the Hilbert transform was extracted as the second eigenvector. Finally, the dual improved fractal box-counting dimension eigenvectors formed the multi-dimensional eigenvectors as signal subtle features, which were used for radiation source signal recognition by the grey relation algorithm. The experimental results show that, compared with the traditional fractal box-counting dimension algorithm and the single improved fractal box-counting dimension algorithm, the proposed dual improved fractal box-counting dimension algorithm can better extract the signal subtle distribution characteristics under different reconstruction phase space, and has a better recognition effect with good real-time performance.
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Ziatdinov, S. I. "Influence of Mismatch of Parameters of Quadrature Channels on the Work of the Adaptive Selection System for Moving Targets." Journal of the Russian Universities. Radioelectronics 23, no. 3 (July 21, 2020): 25–31. http://dx.doi.org/10.32603/1993-8985-2020-23-3-25-31.
Full textAbstract:
Introduction. The paper considers the operation of an adaptive selection system for moving targets, represented by a one-time multi-period subtractor. The system of selection of moving targets is made in the form of two quadrature channels, in which high-frequency input radio signals are converted to video frequency. Goal. Investigation of the system of selection of moving targets in the conditions of amplitude and phase misalignment of quadrature channels. Aim. The study of the operation of the moving targets selection system in the conditions of amplitude and phase mismatches of quadrature channels. Materials and methods. The method of complex variable is used, in which the input and output signals of the adaptive selection system for moving targets are represented as a pair of complex-conjugate components. Results. An expression is obtained for the frequency transfer function of an adaptive passive noise suppression system with a variable cut-off zone relative to the average frequency of the spectrum of interference signals. The influence of almost unavoidable amplitude and phase mismatches in the characteristics of quadrature channels is studied. Expressions are obtained for the dispersion of output noise signals of the considered system of moving targets with amplitude and phase misalignment of quadrature channels. Analytical relations for the coefficients of passive interference suppression are presented. The dependences of the jamming signal suppression coefficients were calculated and constructed depending on the deviation of the transmission coefficients of quadrature channels and the phase misalignment of the reference voltages for different values of the average frequency of the passive noise spectrum. Conclusion. The essential dependence of the jamming signal suppression coefficient on their average frequency, as well as amplitude and phase misalignments of quadrature channels is shown. The proposed research method allows us to evaluate the effect of misalignment of quadrature channels on the operation of a moving target selection system using high-order cutting filters.
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Aleksic, Sanja, Dragana Markushev, Dragan Pantic, Mihajlo Rabasovic, Dragan Markushev, and Dragan Todorovic. "Electro-acustic influence of the measuring system on the photoacoustic signal amplitude and phase in frequency domain." Facta universitatis - series: Physics, Chemistry and Technology 14, no. 1 (2016): 9–20. http://dx.doi.org/10.2298/fupct1601009a.
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The paper discusses the most common impacts of the measuring system on the amplitude and phase of the photoacoustic signals in the frequency domain using the open-cell experimental set-up. The highest signal distortions are detected at the ends of the observed modulation frequency range from 20 Hz to 20 kHz. The attenuation of the signal is observed at lower frequencies, caused by the electronic filtering of the microphone and sound card, with characteristic frequencies of 15 Hz and 25 Hz. At higher frequencies, the dominant signal distortions are caused by the microphone acoustic filtering, having characteristic frequencies around 9 kHz and 15 kHz. It has been found that the microphone incoherent noise, the so called flicker noise, is negligibly small in comparison to the signal and does not affect the signal shape. However, a coherent noise originating from the power modulation system of the light source significantly affects the shape of the signal in the range greater than 10 kHz. The effects of the coherent noise and measuring system influence are eliminated completely using the relevant signal correction procedure targeting the photoacoustic signal generated by the sample.
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Dorofeev, N. V., A. V. Grecheneva, O. R. Kuzichkin, R. V. Romanov, and D. I. Surzhik. "The method of the phase control of the electrical installation during geodynamic monitoring." MATEC Web of Conferences 272 (2019): 01045. http://dx.doi.org/10.1051/matecconf/201927201045.
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The paper substantiates the application of the phase control of the multipolar equipotential electrical installation to improve the geodynamic sensitivity of the geoelectric control method in geodynamic and geotechnical monitoring systems. The principle of the control of the source of sounding signals and the detection of geodynamics of the geological environment is shown in article. In this work is proposed the device on base of the phase modulator to eliminate the shortcomings of existing devices of the controlling of the phase of sound geoelectrical signals. The developed device contains two amplitude limiters, the integrating unit, the adder, the master oscillator and the amplitude modulator. In practice the application of the proposed device allow to obtain the technical and the economic efficiency by simplifying of the circuit of the generation of the signal with the phase-modulation, by increasing the linearity of the modulation characteristic, and by generating of the signal with the phase-modulate on output of the device.
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Liu, Xuan Chao, and Pei Pei Li. "Weak Signal Detection Based on the Nonlinear Dynamic Model." Applied Mechanics and Materials 157-158 (February 2012): 887–91. http://dx.doi.org/10.4028/www.scientific.net/amm.157-158.887.
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In order to obtain new ways of weak signal detection, we analyzed the motion states of nonlinear dynamic model Duffing oscillator in the case of different amplitude of input signals by solving the Duffing equation and expounded the basic principles of weak signal detection based on Duffing oscillator phase-change characteristics, further illustrated the relationship between signal detection accuracy and detection time by the experimental, researched the impact on signal detection coming from Gaussian white noise and also pointed out how to use intermittent chaos state to implement weak signal detection. The results showed that Duffing oscillator can be effectively detect the slight changes of input signal in the strong noises background, so as to achieve the purpose of weak signal detection. Compared with existing methods, it could greatly improve the detection results.
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Kharisov, V. N., and A. V. Peltin. "Algorithm for estimating energy characteristics at the output of the correlator." Radioengineering 8 (2021): 24–28. http://dx.doi.org/10.18127/j00338486-202108-03.
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For the operation of the channels for tracking the carrier (phase and frequency) and the envelope of the signal of the primary processing of the navigation equipment, it is necessary to evaluate, in one way or another, the energy parameters at the output of the correlator: the amplitude of the signal component and the dispersion at the output of the correlator. In practice, to estimate the amplitude of the signal component, either the real part or the modulus of the complex correlator is used over the entire grouping interval. These approaches have a number of disadvantages. To estimate the variance of the correlator output, it is necessary to select separate channels in which there is obviously no useful signal, which takes away some part of the hardware resources. The article proposes an algorithm for estimating the energy parameters at the output of the correlator only from the data of the corresponding channel without the formation of special correlators, which is operable in both coherent and incoherent modes and is based on the use of correlation integrals over short and full intervals. Modeling and analysis of the accuracy characteristics of the proposed algorithm is carried out.
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Tang, Yu. "Simulation Research on how to Improve the Range Resolution of Pulse Compression Radar Based on Phase Coding." Applied Mechanics and Materials 143-144 (December 2011): 634–38. http://dx.doi.org/10.4028/www.scientific.net/amm.143-144.634.
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Phase coded radar signal is one of the pulse-pulse modulation signal in the radar system. Based on the characteristics of matched filtering, we theoretically analyze the basic principle of the phase coded compression radar system. In the Matlab platform, we set up a simulation model which is used for matching filter, when the radar transmitting signal is Barke code signal. The simulation results show that Echo signal can obtain certain pulse compression ratio. By the matched filter, the main lobe amplitude of 13 bits Barker code signal is 22 times the rate of side-lobe. 13 bits Barker codes by the matched filter have the maximum pulse compression ratio.
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Petrushak, V. S. "MEASUREMENT OF THE AMPLITUDE OF PERIODIC SIGNALS USING THE FIBONACCI METHOD." Devices and Methods of Measurements 9, no. 2 (June 15, 2018): 167–72. http://dx.doi.org/10.21122/2220-9506-2018-9-2-167-172.
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Development of new methods and high-rate means for converting the amplitude of high-frequency periodic signals into a binary code with high speed for solving problems of industrial tomography, radar, radio navigation, during measurements of amplitude-frequency characteristics, measurement of the amplitude of signal generators is relevant in scientific terms and useful in practical applications. The aim of the study was to create a new amplitude meter for high-frequency periodic signals based on the Fibonacci method without converting the AC voltage into an equivalent parameter.Based on the developed algorithm and the equation for converting the amplitude of periodic signals into code using the Fibonacci method, a functional scheme of the amplitude converter has been developed. This made it possible to realize an 8-bit amplitude converter in code on the FPGA Cyclone V series of the Altera company. Amplitude converter of periodic signals into the code based on the Fibonacci method consists of: two comparators, a phase detector, a short pulse shaper, a digital-to-analog converter, a Fibonacci register, an extender, a clock counter, a decoder and an indicator. In the developed meters of the amplitude of the periodic signal, the process of forming the measuring periods and their calculation was applied, this made it possible to avoid the conversion of the alternating voltage into an equivalent parameter. The process of forming measurement periods and their calculation is realized on the basis of a comparator and a counter. The application of the Fibonacci register allowed setting the conversion time at the level of N/f (number of register bits / frequency of the incoming signal). Using the Fibonacci sequence of the pentanacci sequence in the basis of the work of the Fibonacci register allowed obtaining odd code values at its output.Based on the obtained research results, a high-resolution converter of the amplitude of high-frequency periodic signals can be developed into a binary code with high speed for tasks: industrial tomography, radar and radio navigation.
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Shiryaev, Daniil S., Olga A. Kozyreva, Ivan S. Polukhin, Sergey A. Shcheglov, Svetlana A. Degtiareva, Maxim A. Odnoblyudov, and Vladislav E. Bougrov. "The Intellectual Lighting And Data Transmission System based On RGBW Light Emitting Diodes." Light & Engineering, no. 01-2021 (February 2021): 63–68. http://dx.doi.org/10.33383/2019-058.
Full textAbstract:
The system of intellectual lighting data transmission via visible light is developed and manufactured. Spectral characteristics of a downlink which uses the red crystal of a RGBW light emitting diode for data transfer were studied. The DALI protocol-based radiation chromaticity control system which allows us to set different lighting scenarios with constant data transmission rate was developed. The radiation chromaticity range covers almost the entire colour gamut in the colour space. The system of high-frequency matching of system component impedances was developed and frequency characteristics of the suggested scheme were studied for development of the system. Optimal parameters of the signal for visual light communication such as carrier frequency, modulation type and band were determined. Observation of the constellation diagram which represents different values of the complex amplitude of the keyed signal in the form of a complex number on a quadrature plane (cosine and sine components of the carrying signal) and of fixation of the amplitude of the error vector magnitude (EVM) was selected as a method of study of the transmission channel quality. The value of EVM in the visible light transmission channel was significantly lower for signals with amplitude modulation than for phase-manipulated signals. When implementing different lighting change scenarios, radiation of other crystals of the light emitting diode crystals not used for transmission did not lead to increase of EVM by more than one percent.
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Zhao, Binbin, Yibo Peng, Xingguang Wang, and Cheng Wang. "Modulation Characteristics of Period-One Oscillations in Quantum Cascade Lasers." Applied Sciences 11, no. 24 (December 10, 2021): 11730. http://dx.doi.org/10.3390/app112411730.
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Quantum cascade lasers subject to tilted optical feedback produce periodic oscillations, quasi-periodic oscillations, and low-frequency oscillations. This work presents the modulation characteristics of period-one (P1) oscillations in a quantum cascade laser with tilted optical feedback. The electrical signal at the oscillation frequency is more than 50 dB higher than the noise level, and the electrical linewidth is less than 2.0 kHz. This electrical linewidth is about four orders of magnitude narrower than the optical linewidth (around 16 MHz) of the free-running laser, which suggests that the optical sidebands induced by the P1 oscillations are highly coherent with the main optical mode. In addition, the modulation depth of the optical signal is found to be in the range of 1% to 3.5%. In addition, it is verified in the simulations that the P1 oscillations induce not only amplitude modulation but also frequency modulation due to the phase-amplitude coupling effect.
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Li, Yuan Yuan, Qi Zhong Liu, and Chao Gang Yu. "Wavelet Transform for Starting Characteristics of Three-Phase Cage Asynchronous Motor." Advanced Materials Research 347-353 (October 2011): 2987–90. http://dx.doi.org/10.4028/www.scientific.net/amr.347-353.2987.
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In electric machinery performance test, tooth harmonic time-frequency characters of first order of three-phase cage asynchronous motor are most important. The MATLAB software is used to make model and simulate the starting characteristic of asynchronous motor in this article, while the stator current signal of starting motor is de noised by wavelet transform. Through decomposition and reconstruction of wavelet transform, the amplitude of fundamental and harmonic wave in de noising stator current can be reduced, and then the tooth harmonic of first order of starting rotor is extracted. Using the excellent time-frequency analyzing characters of wavelet package transform, the tooth harmonic time-frequency curve is fitted.
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Zhang, Jie, and Jiudong Zheng. "Prototype Verification of Self-Interference Suppression for Constant-Amplitude Full-Duplex Phased Array with Finite Phase Shift." Electronics 11, no. 3 (January 18, 2022): 295. http://dx.doi.org/10.3390/electronics11030295.
Full textAbstract:
In view of the strong self-interference problem when the practical phased array system is simultaneously applied for transmission and reception, under the constraints including limited quantization number, constant envelope amplitude, scanning mode, wideband signal mode, etc., this work studies it and proposes the amplitude-phase joint adjustment method and the phase-only method for beamforming optimization. Through digital simulation design, electromagnetic simulation evaluation and principle test verification, under the actual array system conditions, including 6-bit phase quantization or phase step size of 5.625° and amplitude 0.5 dB quantization step, when the transmitting beam is pointing (0°, 0°), the research has achieved a performance of 11.9~14.4 dB for self-interference suppression; at the same time, the optimized beam shape is maintained well, and the ratio of the main lobe to the side lobes does not change significantly, but the beam gain has a loss of about 2~3 dB. In addition, we studied the interference suppression performance and beam feature retention performance of the optimized beamforming weights in the case of array scanning and broadband signals, and analyzed the influence of the changes in the mutual coupling characteristics between elements caused by scanning and frequency changes on the cancellation performance. This provides a reference for the application research of the simultaneous transmitting and receiving self-interference suppression technology in the actual array system state.
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Magerramov, R. V. "Conversion of amplitude modulated square wave signal from current sensor to pulse duration using PLL circuit." Issues of radio electronics, no. 8 (August 7, 2019): 37–42. http://dx.doi.org/10.21778/2218-5453-2019-8-37-42.
Full textAbstract:
At the moment, almost any electronic product incorporates measuring sensors for converting physical quantities. These devices produce a signal of measurement information in a form suitable for transmission and further conversion. As a rule, the output signal from the measurement sensors undergoes first preprocessing such as amplification, filtering, modulation, etc. After preprocessing the prepared signal, various architectures of analog‑to‑digital converters (ADC) are used. The choice of ADC depends on the parameters of the conversion signal and the dynamic characteristics of the sensors used. This paper considers converting a square‑amplitude modulated signal from a current sensor to a pulse width using a phase‑locked loop (PLL). The architecture of the ADC based on the PLL circuit allows obtaining a linear dependence of the output signal duty cycle on the value of the measured input current. The layout of the device is implemented on a printed circuit board, the main components of which are: current sensor, which is a bridge circuit of magnetoresistive conductors; phase‑sensitive rectifier and microcircuit of a two‑channel PLL circuit made inTechnological Center.
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Xu, Hui Yan. "Fractional Fourier Transform Image Analysis." Applied Mechanics and Materials 198-199 (September 2012): 288–93. http://dx.doi.org/10.4028/www.scientific.net/amm.198-199.288.
Full textAbstract:
As a generalized form of the Fourier transform, fractional Fourier transform (FRFT) ,which is integrated the signal in time domain and frequency domain, is a new time-frequency analysis. From the simulation point of view to image the distribution of energy in the fractional Fourier domain, the amplitude and phase characteristics, simulation results show that any fractional Fourier domain, can reflect the image of the space-frequency domain characteristics, with the order, the image The distribution of the space-frequency domain characteristics will change. The image of the fractional Fourier transform amplitude and phase reconstruction of the image information with the original image also showed some important conclusions for the fractional Fourier transform applied to image recognition and edge detection is of great significance.