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Artykuły w czasopismach na temat „Frequency radar”
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Caffa, Mattia, Francesco Biletta i Riccardo Maggiora. "Binary-Phase vs. Frequency Modulated Radar Measured Performances for Automotive Applications". Sensors 23, nr 11 (1.06.2023): 5271. http://dx.doi.org/10.3390/s23115271.
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Radars have been widely deployed in cars in recent years, for advanced driving assistance systems. The most popular and studied modulated waveform for automotive radar is the frequency-modulated continuous wave (FMCW), due to FMCW radar technology’s ease of implementation and low power consumption. However, FMCW radars have several limitations, such as low interference resilience, range-Doppler coupling, limited maximum velocity with time-division multiplexing (TDM), and high-range sidelobes that reduce high-contrast resolution (HCR). These issues can be tackled by adopting other modulated waveforms. The most interesting modulated waveform for automotive radar, which has been the focus of research in recent years, is the phase-modulated continuous wave (PMCW): this modulated waveform has a better HCR, allows large maximum velocity, permits interference mitigation, thanks to codes orthogonality, and eases integration of communication and sensing. Despite the growing interest in PMCW technology, and while simulations have been extensively performed to analyze and compare its performance to FMCW, there are still only limited real-world measured data available for automotive applications. In this paper, the realization of a 1 Tx/1 Rx binary PMCW radar, assembled with connectorized modules and an FPGA, is presented. Its captured data were compared to the captured data of an off-the-shelf system-on-chip (SoC) FMCW radar. The radar processing firmware of both radars were fully developed and optimized for the tests. The measured performances in real-world conditions showed that PMCW radars manifest better behavior than FMCW radars, regarding the above-mentioned issues. Our analysis demonstrates that PMCW radars can be successfully adopted by future automotive radars.
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Roarty, Hugh J., Erick Rivera Lemus, Ethan Handel, Scott M. Glenn, Donald E. Barrick i James Isaacson. "Performance Evaluation of SeaSonde High-Frequency Radar for Vessel Detection". Marine Technology Society Journal 45, nr 3 (1.05.2011): 14–24. http://dx.doi.org/10.4031/mtsj.45.3.2.
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AbstractHigh-frequency (HF) surface wave radar has been identified to be a gap-filling technology for Maritime Domain Awareness. Present SeaSonde HF radars have been designed to map surface currents but are able to track surface vessels in a dual-use mode. Rutgers and CODAR Ocean Sensors, Ltd., have collaborated on the development of vessel detection and tracking capabilities from compact HF radars, demonstrating that ships can be detected and tracked by multistatic HF radar in a multiship environment while simultaneously mapping ocean currents. Furthermore, the same vessel is seen simultaneously by the radar based on different processing parameters, mitigating the need to preselect a fixed set and thereby improving detection performance.
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Wang, Dingyang, Sungwon Yoo i Sung Ho Cho. "Experimental Comparison of IR-UWB Radar and FMCW Radar for Vital Signs". Sensors 20, nr 22 (23.11.2020): 6695. http://dx.doi.org/10.3390/s20226695.
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In this paper, we compare the performances of impulse radio ultra-wideband (IR-UWB) and frequency modulation continuous wave (FMCW) radars in measuring noncontact vital signs such as respiration rate and heart rate. These two type radars have been widely used in various fields and have shown their applicability to extract vital signs in noncontact ways. IR-UWB radar can extract vital signs using distance information. On the other hand, FMCW radar requires phase information to estimate vital signs, and the result can be enhanced with Multi-input Multi-output (MIMO) antenna topologies. By using commercial radar chipsets, the operation of radars under different conditions and frequency bands will also affect the performance of vital sign detection capabilities. We compared the accuracy and signal-to-noise (SNR) ratios of IR-UWB and FMCW radars in various scenarios, such as distance, orientation, carotid pulse, harmonics, and obstacle penetration. In general, the IR-UWB radars offer a slightly better accuracy and higher SNR in comparison to FMCW radar. However, each radar system has its own unique advantages, with IR-UWB exhibiting fewer harmonics and a higher SNR, while FMCW can combine the results from each channel.
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Frech, Michael, Cornelius Hald, Maximilian Schaper, Bertram Lange i Benjamin Rohrdantz. "Assessing and mitigating the radar–radar interference in the German C-band weather radar network". Atmospheric Measurement Techniques 16, nr 2 (20.01.2023): 295–309. http://dx.doi.org/10.5194/amt-16-295-2023.
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Abstract. The national German weather radar network operates in C-band between 5.6 and 5.65 GHz. In a radar network, individual transmit frequencies have to be chosen such that radar–radar-induced interferences are avoided. In a unique experiment the Hohenpeißenberg research radar and five operational systems from the radar network were used to characterize radar–radar-induced interferences as a function of the radar frequency. The results allow assessment of the possibility of adding additional C-band radars with magnetron transmitters into the existing network. Based on the experiment, at least a 15 MHz separation of the nominal radar frequency is needed to avoid a radar–radar interference. The most efficient mitigation of radar–radar interference is achieved by the “Radar Tango”, which refers to the synchronized scanning of all radar systems in the network. Based on those results, additional C-band radar systems can be added to the German weather radar network if a further improvement of the radar coverage is needed.
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Yang, Jian, Zengtian Chang, Dongchu Su, Chenyong Li, Siwei Luo, BoWei Chang i Lu Qiang. "Influence of Public Mobile Communication System on the Frequency of S-Band Radars". Journal of Physics: Conference Series 2196, nr 1 (1.02.2022): 012031. http://dx.doi.org/10.1088/1742-6596/2196/1/012031.
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Abstract Given the interference between public mobile communication system and S-band radars, an applicable interference analysis model was established, the typical frequency parameters of radar and the key parameters of the base station were sorted out, the radiation parameters of the mobile terminal (MT) were tested practically, and the interferences of the base station and MT to radar were calculated. Further, the Monte Carlo method was taken to simulate the system-level lumped interference of the communication system to radar, and an analysis was made on the influence of the communication system on the frequency of radar. The results revealed that the public mobile communication system had severe lumped interference with radar, which may affect radar frequency. Therefore, it is necessary to take measures to protect radar.
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Muaaz, Muhammad, Sahil Waqar i Matthias Pätzold. "Orientation-Independent Human Activity Recognition Using Complementary Radio Frequency Sensing". Sensors 23, nr 13 (22.06.2023): 5810. http://dx.doi.org/10.3390/s23135810.
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RF sensing offers an unobtrusive, user-friendly, and privacy-preserving method for detecting accidental falls and recognizing human activities. Contemporary RF-based HAR systems generally employ a single monostatic radar to recognize human activities. However, a single monostatic radar cannot detect the motion of a target, e.g., a moving person, orthogonal to the boresight axis of the radar. Owing to this inherent physical limitation, a single monostatic radar fails to efficiently recognize orientation-independent human activities. In this work, we present a complementary RF sensing approach that overcomes the limitation of existing single monostatic radar-based HAR systems to robustly recognize orientation-independent human activities and falls. Our approach used a distributed mmWave MIMO radar system that was set up as two separate monostatic radars placed orthogonal to each other in an indoor environment. These two radars illuminated the moving person from two different aspect angles and consequently produced two time-variant micro-Doppler signatures. We first computed the mean Doppler shifts (MDSs) from the micro-Doppler signatures and then extracted statistical and time- and frequency-domain features. We adopted feature-level fusion techniques to fuse the extracted features and a support vector machine to classify orientation-independent human activities. To evaluate our approach, we used an orientation-independent human activity dataset, which was collected from six volunteers. The dataset consisted of more than 1350 activity trials of five different activities that were performed in different orientations. The proposed complementary RF sensing approach achieved an overall classification accuracy ranging from 98.31 to 98.54%. It overcame the inherent limitations of a conventional single monostatic radar-based HAR and outperformed it by 6%.
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Silva, Murilo Teixeira, Weimin Huang i Eric W. Gill. "Bistatic High-Frequency Radar Cross-Section of the Ocean Surface with Arbitrary Wave Heights". Remote Sensing 12, nr 4 (18.02.2020): 667. http://dx.doi.org/10.3390/rs12040667.
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The scattering theory developed in the past decades for high-frequency radio oceanography has been restricted to surfaces with small heights and small slopes. In the present work, the scattering theory for bistatic high-frequency radars is extended to ocean surfaces with arbitrary wave heights. Based on recent theoretical developments in the scattering theory for ocean surfaces with arbitrary heights for monostatic radars, the electric field equations for bistatic high-frequency radars in high sea states are developed. This results in an additional term related to the first-order electric field, which is only present when the small-height approximation is removed. Then, the radar cross-section for the additional term is derived and simulated, and its impact on the total radar cross-section at different radar configurations, dominant wave directions, and sea states is assessed. The proposed term is shown to impact the total radar cross-section at high sea states, dependent on radar configuration and dominant wave direction. The present work can contribute to the remote sensing of targets on the ocean surface, as well as the determination of the dominant wave direction of the ocean surface at high sea states.
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Mroz, Kamil, Alessandro Battaglia, Cuong Nguyen, Andrew Heymsfield, Alain Protat i Mengistu Wolde. "Triple-frequency radar retrieval of microphysical properties of snow". Atmospheric Measurement Techniques 14, nr 11 (17.11.2021): 7243–54. http://dx.doi.org/10.5194/amt-14-7243-2021.
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Abstract. An algorithm based on triple-frequency (X, Ka, W) radar measurements that retrieves the size, water content and degree of riming of ice clouds is presented. This study exploits the potential of multi-frequency radar measurements to provide information on bulk snow density that should underpin better estimates of the snow characteristic size and content within the radar volume. The algorithm is based on Bayes' rule with riming parameterised by the “fill-in” model. The radar reflectivities are simulated with a range of scattering models corresponding to realistic snowflake shapes. The algorithm is tested on multi-frequency radar data collected during the ESA-funded Radar Snow Experiment For Future Precipitation Mission. During this campaign, in situ microphysical probes were mounted on the same aeroplane as the radars. This nearly perfectly co-located dataset of the remote and in situ measurements gives an opportunity to derive a combined multi-instrument estimate of snow microphysical properties that is used for a rigorous validation of the radar retrieval. Results suggest that the triple-frequency retrieval performs well in estimating ice water content (IWC) and mean mass-weighted diameters obtaining root-mean-square errors of 0.13 and 0.15, respectively, for log 10IWC and log 10Dm. The retrieval of the degree of riming is more challenging, and only the algorithm that uses Doppler information obtains results that are highly correlated with the in situ data.
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Parent du Chatelet, Jacques, Chiraz Boudjabi, Lucas Besson i Olivier Caumont. "Errors Caused by Long-Term Drifts of Magnetron Frequencies for Refractivity Measurement with a Radar: Theoretical Formulation and Initial Validation". Journal of Atmospheric and Oceanic Technology 29, nr 10 (1.10.2012): 1428–34. http://dx.doi.org/10.1175/jtech-d-12-00070.1.
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Abstract Refractivity measurements in the boundary layer by precipitation radar could be useful for convection prediction. Until now such measurements have only been performed by coherent radars, but European weather radars are mostly equipped with noncoherent magnetron transmitters for which the phase and frequency may vary. In this paper, the authors give an analytical expression of the refractivity measurement by a noncoherent drifting-frequency magnetron radar and validate it by comparing with in situ measurements. The main conclusion is that, provided the necessary corrections are applied, the measurement can be successfully performed with a noncoherent radar. The correction factor mainly depends on the local-oscillator frequency variation, which is known perfectly. A second-order error, proportional to the transmitted frequency variation, can be neglected as long as this change remains small.
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Leinonen, Jussi, Matthew D. Lebsock, Simone Tanelli, Ousmane O. Sy, Brenda Dolan, Randy J. Chase, Joseph A. Finlon, Annakaisa von Lerber i Dmitri Moisseev. "Retrieval of snowflake microphysical properties from multifrequency radar observations". Atmospheric Measurement Techniques 11, nr 10 (5.10.2018): 5471–88. http://dx.doi.org/10.5194/amt-11-5471-2018.
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Abstract. We have developed an algorithm that retrieves the size, number concentration and density of falling snow from multifrequency radar observations. This work builds on previous studies that have indicated that three-frequency radars can provide information on snow density, potentially improving the accuracy of snow parameter estimates. The algorithm is based on a Bayesian framework, using lookup tables mapping the measurement space to the state space, which allows fast and robust retrieval. In the forward model, we calculate the radar reflectivities using recently published snow scattering databases. We demonstrate the algorithm using multifrequency airborne radar observations from the OLYMPEX–RADEX field campaign, comparing the retrieval results to hydrometeor identification using ground-based polarimetric radar and also to collocated in situ observations made using another aircraft. Using these data, we examine how the availability of multiple frequencies affects the retrieval accuracy, and we test the sensitivity of the algorithm to the prior assumptions. The results suggest that multifrequency radars are substantially better than single-frequency radars at retrieving snow microphysical properties. Meanwhile, triple-frequency radars can retrieve wider ranges of snow density than dual-frequency radars and better locate regions of high-density snow such as graupel, although these benefits are relatively modest compared to the difference in retrieval performance between dual- and single-frequency radars. We also examine the sensitivity of the retrieval results to the fixed a priori assumptions in the algorithm, showing that the multifrequency method can reliably retrieve snowflake size, while the retrieved number concentration and density are affected significantly by the assumptions.
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Johnston, Paul E., James R. Jordan, Allen B. White, David A. Carter, David M. Costa i Thomas E. Ayers. "The NOAA FM-CW Snow-Level Radar". Journal of Atmospheric and Oceanic Technology 34, nr 2 (luty 2017): 249–67. http://dx.doi.org/10.1175/jtech-d-16-0063.1.
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AbstractA vertically pointing radar for monitoring radar brightband height (BBH) has been developed. This new radar utilizes frequency-modulated continuous wave (FM-CW) techniques to provide high-resolution data at a fraction of the cost of comparable pulsed radars. This S-band radar provides details of the vertical structure of precipitating clouds, with full Doppler information. Details of the radar design are presented along with observations from one storm. Results from a calibration using these storm data show the radar meets the design goals. Eleven of these radars have been deployed and provide BBH data in near–real time.
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Shi, Di, Gunnar Gidion, Taimur Aftab, Leonhard M. Reindl i Stefan J. Rupitsch. "Frequency Comb-Based Ground-Penetrating Bioradar: System Implementation and Signal Processing". Sensors 23, nr 3 (25.01.2023): 1335. http://dx.doi.org/10.3390/s23031335.
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Radars can be used as sensors to detect the breathing of victims trapped under layers of building materials in catastrophes like earthquakes or gas explosions. In this contribution, we present the implementation of a novel frequency comb continuous wave (FCCW) bioradar module using a commercial software-defined radio (SDR). The FCCW radar transmits multiple equally spaced frequency components simultaneously. The data acquisition of the received combs is frequency domain-based. Hence, it does not require synchronization between the transmit and receive channels, as time domain-based broadband radars, such as ultra wideband (UWB) pulse radar and frequency-modulated CW (FMCW) radar, do. Since a frequency comb has an instantaneous wide bandwidth, the effective scan rate is much higher than that of a step frequency CW (SFCW) radar. This FCCW radar is particularly suitable for small motion detection. Using inverse fast Fourier transform (IFFT), we can decompose the received frequency comb into different ranges and remove ghost signals and interference of further range intervals. The frequency comb we use in this report has a bandwidth of only 60 MHz, resulting in a range resolution of up to 2.5 m, much larger than respiration-induced chest wall motions. However, we demonstrate that in the centimeter range, motions can be detected and evaluated by processing the received comb signals. We want to integrate the bioradar into an unmanned aircraft system for fast and safe search and rescue operations. As a trade-off between ground penetrability and the size and weight of the antenna and the radar module, we use 1.3 GHz as the center frequency. Field measurements show that the proposed FCCW bioradar can detect an alive person through different nonmetallic building materials.
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Figueras i Ventura, Jordi, i Pierre Tabary. "The New French Operational Polarimetric Radar Rainfall Rate Product". Journal of Applied Meteorology and Climatology 52, nr 8 (sierpień 2013): 1817–35. http://dx.doi.org/10.1175/jamc-d-12-0179.1.
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AbstractIn 2012 the Météo France metropolitan operational radar network consists of 24 radars operating at C and S bands. In addition, a network of four X-band gap-filler radars is being deployed in the French Alps. The network combines polarimetric and nonpolarimetric radars. Consequently, the operational radar rainfall algorithm has been adapted to process both polarimetric and nonpolarimetric data. The polarimetric processing chain is available in two versions. In the first version, now operational, polarimetry is only used to correct for attenuation and filter out clear-air echoes. In the second version there is a more extensive use of polarimetry. In particular, the specific differential phase Kdp is used to estimate rainfall rate in intense rain. The performance of the three versions of radar rainfall algorithms (conventional, polarimetric V1, and polarimetric V2) at different frequency bands (S, C, and X) is evaluated by processing radar data of significant events offline and comparing hourly radar rainfall accumulations with hourly rain gauge data. The results clearly show a superior performance of the polarimetric products with respect to the nonpolarimetric ones at all frequency bands, but particularly at higher frequency. The second version of the polarimetric product, which makes a broader use of polarimetry, provides the best overall results.
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Bhutani, Akanksha, Sören Marahrens, Michael Gehringer, Benjamin Göttel, Mario Pauli i Thomas Zwick. "The Role of Millimeter-Waves in the Distance Measurement Accuracy of an FMCW Radar Sensor". Sensors 19, nr 18 (12.09.2019): 3938. http://dx.doi.org/10.3390/s19183938.
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High-accuracy, short-range distance measurement is required in a variety of industrial applications e.g., positioning of robots in a fully automated production process, level measurement of liquids in small containers. An FMCW radar sensor is suitable for this purpose, since many of these applications involve harsh environments. Due to the progress in the field of semiconductor technology, FMCW radar sensors operating in different millimeter-wave frequency bands are available today. An important question in this context, which has not been investigated so far is how does a millimeter-wave frequency band influence the sensor accuracy, when thousands of distance measurements are performed with a sensor. This topic has been dealt with for the first time in this paper. The method used for analyzing the FMCW radar signal combines a frequency- and phase-estimation algorithm. The frequency-estimation algorithm based on the fast Fourier transform and the chirp-z transform provides a coarse estimate of the target distance. Subsequently, the phase-estimation algorithm based on a cross-correlation function provides a fine estimate of the target distance. The novel aspects of this paper are as follows. First, the estimation theory concept of Cramér-Rao lower bound (CRLB) has been used to compare the accuracy of two millimeter-wave FMCW radars operating at 60 GHz and 122 GHz. In this comparison, the measurement parameters (e.g., bandwidth, signal-to-noise ratio) as well as the signal-processing algorithm used for both the radars are the same, thus ensuring an unbiased comparison of the FMCW radars, solely based on the choice of millimeter-wave frequency band. Second, the improvement in distance measurement accuracy obtained after each step of the combined frequency- and phase-estimation algorithm has been experimentally demonstrated for both the radars. A total of 5100 short-range distance measurements are made using the 60 GHz and 122 GHz FMCW radar. The measurement results are analyzed at various stages of the frequency- and phase-estimation algorithm and the measurement error is calculated using a nanometer-precision linear motor. At every stage, the mean error values measured with the 60 GHz and 122 GHz FMCW radars are compared. The final accuracy achieved using both radars is of the order of a few micrometers. The measured standard deviation values of the 60 GHz and 122 GHz FMCW radar have been compared against the CRLB. As predicted by the CRLB, this paper experimentally validates for the first time that the 122 GHz FMCW radar provides a higher repeatability of micrometer-accuracy distance measurements than the 60 GHz FMCW radar.
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Bhutani, Akanksha, Sören Marahrens, Marius Kretschmann, Serdal Ayhan, Steffen Scherr, Benjamin Göttel, Mario Pauli i Thomas Zwick. "Applications of radar measurement technology using 24 GHz, 61 GHz, 80 GHz and 122 GHz FMCW radar sensors". tm - Technisches Messen 89, nr 2 (2.12.2021): 107–21. http://dx.doi.org/10.1515/teme-2021-0034.
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Abstract This paper presents a review of radar applications in high-accuracy distance measurement of a target. The radars included in this review are frequency modulated continuous wave (FMCW) radar sensors operating in four different millimeter-wave frequency bands, namely 24 GHz, 61 GHz, 80 GHz and 122 GHz. The radar sensors are used to measure the distance of standard and complex targets in a short range of a few meters, thus indicating that the choice of target and the medium used for radar signal propagation also play a key role in determining the distance measurement accuracy of an FMCW radar. The standard target is a trihedral corner reflector in a laboratory-based free space measurement setup and the complex targets include a piston in an oil-filled hydraulic cylinder and a planar positioning stage used in micromachining. In each of these measurement scenarios, a distance measurement accuracy in micrometer range is achieved due to the use of a sophisticated signal processing algorithm that is based on a combined frequency and phase estimation method. The paper is concluded with a technical comparison of the accuracy achieved by the FMCW radars reviewed in this article with other related works.
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Ilcev, Dimov Stojce. "Introduction to Coastal HF Maritime Surveillance Radars". Polish Maritime Research 26, nr 3 (1.09.2019): 153–62. http://dx.doi.org/10.2478/pomr-2019-0056.
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Abstract This paper presents the main technical characteristics and working performances of coastal maritime surveillance radars, such as low-power High-Frequency Surface Wave Radars (HFSWR) and Over the Horizon Radars (OTHR). These radars have demonstrated to be a cost-effective long-range early-warning sensor for ship detection and tracking in coastal waters, sea channels and passages. In this work, multi-target tracking and data fusion techniques are applied to live-recorded data from a network of oceanographic HFSWR stations installed in Jindalee Operational Radar Network (JORN), Wellen Radar (WERA) in Ligurian Sea (Mediterranean Sea), CODAR Ocean Sebsorsin and in the German Bight (North Sea). The coastal Imaging Sciences Research (ISR) HFSWR system, Multi-static ISR HF Radar, Ship Classification using Multi-Frequency HF Radar, Coastal HF radar surveillance of pirate boats and Different projects of coastal HF radars for vessels detecting are described. Ship reports from the Automatic Identification System (AIS), recorded from both coastal and satellite Land Earth Stations (LES) are exploited as ground truth information and a methodology is applied to classify the fused tracks and to estimate system performances. Experimental results for all above solutions are presented and discussed, together with an outline for future integration and infrastructures.
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Дудуш, А. С., І. І. Сачук, Сальман Оваід i А. К. Бідун. "Science & technology trends in cognitive radar concept". Системи обробки інформації, nr 3(166) (24.09.2021): 22–34. http://dx.doi.org/10.30748/soi.2021.166.02.
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Currently, human operators provide cognition in a radar system. However, advances in the “digitization” of radar front-ends, including digital arbitrary waveform generators (AWG) and advanced high performance embedded computing (HPEC) make it possible to vary all key radar parameters (power, pulse length, number of pulses, pulse repetition frequency (PRF), modulation, frequency, polarization) on a pulse-by-pulse basis within ns or ms and over a wide operating range. This timescale is much faster than the decision-making ability of a human operator. The cognitive-inspired techniques in radar, that are intensively developing last years, mimic elements of human cognition and the use of external knowledge to use the available system resources in an optimal way for the current goal and environment. Radar systems based on the perception-action cycle of cognition that senses the environment, learns relevant information from it about the target and the background and then adapts the radar to optimally satisfy the needs of the mission according to a desired goal are called cognitive radars. In the article, recent ideas and applications of cognitive radars were analyzed.
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Chaudhary, Sushank, Lunchakorn Wuttisittikulkij, Muhammad Saadi, Abhishek Sharma, Sattam Al Otaibi, Jamel Nebhen, Demostenes Zegarra Rodriguez i in. "Coherent detection-based photonic radar for autonomous vehicles under diverse weather conditions". PLOS ONE 16, nr 11 (15.11.2021): e0259438. http://dx.doi.org/10.1371/journal.pone.0259438.
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Autonomous vehicles are regarded as future transport mechanisms that drive the vehicles without the need of drivers. The photonic-based radar technology is a promising candidate for delivering attractive applications to autonomous vehicles such as self-parking assistance, navigation, recognition of traffic environment, etc. Alternatively, microwave radars are not able to meet the demand of next-generation autonomous vehicles due to its limited bandwidth availability. Moreover, the performance of microwave radars is limited by atmospheric fluctuation which causes severe attenuation at higher frequencies. In this work, we have developed coherent-based frequency-modulated photonic radar to detect target locations with longer distance. Furthermore, the performance of the proposed photonic radar is investigated under the impact of various atmospheric weather conditions, particularly fog and rain. The reported results show the achievement of significant signal to noise ratio (SNR) and received power of reflected echoes from the target for the proposed photonic radar under the influence of bad weather conditions. Moreover, a conventional radar is designed to establish the effectiveness of the proposed photonic radar by considering similar parameters such as frequency and sweep time.
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Shirasawa, K., N. Ebuchi, M. Leppäranta i T. Takatsuka. "Ice-edge detection from Japanese C-band radar and high-frequency radar coastal stations". Annals of Glaciology 54, nr 62 (2013): 59–64. http://dx.doi.org/10.3189/2013aog62a007.
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AbstractA C-band sea-ice radar (SIR) network system was operated to monitor the sea-ice conditions off the Okhotsk Sea coast of northern Hokkaido, Japan, from 1969 to 2004. The system was based on three radar stations, which were capable of continuously monitoring the sea surface as far as 60 km offshore along a 250 km long coastal section. In 2004 the SIR system was closed down and a sea surface monitoring programme was commenced using high-frequency (HF) radar; this system provides information on surface currents in open-water conditions, while areas with ‘no signal’ can be identified as sea ice. The present study compares HF radar data with SIR data to evaluate their feasibility for sea-ice remote sensing. The period of overlapping data was 1.5 months. The results show that HF radar information can be utilized for ice-edge mapping although it cannot fully compensate for the loss of the SIR system. In particular, HF radar does not provide ice concentration, ice roughness and geometrical structures or ice kinematics. The probability of ice-edge detection by HF radar was 0.9 and the correlation of the ice-edge distance between the radars was 0.7.
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Milczarek, Hubert, Czesław Leśnik, Igor Djurović i Adam Kawalec. "Estimating the Instantaneous Frequency of Linear and Nonlinear Frequency Modulated Radar Signals—A Comparative Study". Sensors 21, nr 8 (17.04.2021): 2840. http://dx.doi.org/10.3390/s21082840.
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Automatic modulation recognition plays a vital role in electronic warfare. Modern electronic intelligence and electronic support measures systems are able to automatically distinguish the modulation type of an intercepted radar signal by means of real-time intra-pulse analysis. This extra information can facilitate deinterleaving process as well as be utilized in early warning systems or give better insight into the performance of hostile radars. Existing modulation recognition algorithms usually extract signal features from one of the rudimentary waveform characteristics, namely instantaneous frequency (IF). Currently, there are a small number of studies concerning IF estimation methods, specifically for radar signals, whereas estimator accuracy may adversely affect the performance of the whole classification process. In this paper, five popular methods of evaluating the IF–law of frequency modulated radar signals are compared. The considered algorithms incorporate the two most prevalent estimation techniques, i.e., phase finite differences and time-frequency representations. The novel approach based on the generalized quasi-maximum likelihood (QML) method is also proposed. The results of simulation experiments show that the proposed QML estimator is significantly more accurate than the other considered techniques. Furthermore, for the first time in the publicly available literature, multipath influence on IF estimates has been investigated.
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Lengfeld, Katharina, Marco Clemens, Claire Merker, Hans Münster i Felix Ament. "A Simple Method for Attenuation Correction in Local X-Band Radar Measurements Using C-Band Radar Data". Journal of Atmospheric and Oceanic Technology 33, nr 11 (listopad 2016): 2315–29. http://dx.doi.org/10.1175/jtech-d-15-0091.1.
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AbstractThis paper presents a novel, simple method to correct reflectivity measurements of weather radars that operate in attenuation-influenced frequency bands using observations from less attenuated radar systems. In recent years radar systems operating in the X-band frequency range have been developed to provide precipitation fields for areas of special interest in high temporal (≤1 min) and spatial (≤250 m) resolution in complement to nationwide radar networks. However, X-band radars are highly influenced by attenuation. C- and S-band radars typically have coarser resolution (250 m–1 km and 5 min) but are less affected by attenuation.Correcting for attenuation effects in simple (non-Doppler) single-polarized X-band radars remains challenging and is often dependent on restriction parameters, for example, those derived from mountain returns. Therefore, these algorithms are applicable only in limited areas. The method proposed here uses measurements from C-band radars and hence can be applied in all regions covered by nationwide C- (or S-) band radar networks. First, a single scan of X-band radar measurements is used exemplary to identify advantages and disadvantages of the novel algorithm compared to a standard single radar algorithm. The performance of the correction algorithms in different types of precipitation is examined in nine case studies. The proposed method provides very promising results for each type of precipitation. Additionally, it is evaluated in a 5-month comparison with Micro Rain Radar (MRR) observations. The bias between uncorrected X-band radar and MRR data is nearly eliminated by the attenuation correction algorithm, and the RMSE is reduced by 20% while the correlation of ~0.9 between both systems remains nearly constant.
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Le, Minda, i V. Chandrasekar. "Ground Validation of Surface Snowfall Algorithm in GPM Dual-Frequency Precipitation Radar". Journal of Atmospheric and Oceanic Technology 36, nr 4 (kwiecień 2019): 607–19. http://dx.doi.org/10.1175/jtech-d-18-0098.1.
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AbstractExtensive evaluations have been performed on the dual-frequency classification module in the Global Precipitation Mission (GPM) Dual-Frequency Precipitation Radar (DPR) level-2 algorithm. Both rain type classification and melting-layer detection continue to show promising results in the validations. Surface snowfall identification is a feature newly added in the classification module to the recently released version to provide a surface snowfall flag for each qualified vertical profile. This algorithm is developed upon vertical features of Ku- and Ka-band reflectivity and dual-frequency ratio from DPR. In this paper, we validate this surface snowfall identification algorithm with ground radars including NEXRAD, NASA Polarimetric Radar (NPOL), and CSU–CHILL radar during concurrent precipitation events and GPM validation campaign Olympic Mountain Experiment (OLYMPEX). Other ground truth such as Precipitation Imaging Package (PIP) and ground report is also included in the validation. Based on 16 validation cases in the years 2014–18, the average match ratio between surface snowfall flag from space radar and ground radar is around 87.8%. Promising agreements are achieved with different validation sources. Algorithm limitation and potential improvement are discussed.
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Alattabi, Zaid R., Douglas Cahl i George Voulgaris. "Swell and Wind Wave Inversion Using a Single Very High Frequency (VHF) Radar". Journal of Atmospheric and Oceanic Technology 36, nr 6 (czerwiec 2019): 987–1013. http://dx.doi.org/10.1175/jtech-d-18-0166.1.
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AbstractA hybrid, empirical radar wave inversion technique that treats swell and wind waves separately is presented and evaluated using a single 48-MHz radar unit and in situ wave measurements. This hybrid approach greatly reduces errors in radar wave inversion during swell seas. Our analysis suggests that, prior to the inversion, the second-order spectrum should be normalized using Barrick’s weighting function because this process removes harmonic and corner reflection peaks from the inversion and improves the results. In addition, the resulting calibration constants for the wind wave component are not wave-frequency dependent and are similar in magnitude to those found in previous studies using different operating-frequency radars. This result suggests radar frequency independence, although additional experimental verification is required. The swell component of the model presented here ignores the effect of swell’s propagation direction on the radar signal. Although this approach has several limitations and may only be useful near the coast (where swell propagates close to perpendicular to the coastline), the resulting wave inversion is accurate even when swell is propagating close to perpendicular to the radar beam direction. RMS differences relative to in situ wave height measurements range from 0.16 to 0.25 m as the radar beam angle increases from 22° to 56°.
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Lipa, Barrick i Whelan. "A Quality Control Method for Broad-Beam HF Radar Current Velocity Measurements". Journal of Marine Science and Engineering 7, nr 4 (19.04.2019): 112. http://dx.doi.org/10.3390/jmse7040112.
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This paper describes a method to provide quality control for radial velocity maps derived from radar echo voltage cross spectra measured by broad-beam high frequency radars. The method involves the comparison of voltage cross spectra measured at Doppler frequencies in the Bragg region with values predicted from basic equations defining the complex voltage cross spectra in terms of the measured antenna patterns and the radar cross section. Poor agreement at a given Doppler frequency indicates contamination of the spectra, usually due to interference; velocity results from that Doppler frequency are then eliminated. Examples are given of its application to broad-beam radars operating at four sites.
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Lukin, Konstantin, Pavlo Vyplavin, Oleg Zemlyaniy, Volodymyr Palamarchuk i Sergii Lukin. "High Resolution Noise Radar without Fast ADC". International Journal of Electronics and Telecommunications 58, nr 2 (1.06.2012): 135–40. http://dx.doi.org/10.2478/v10177-012-0019-1.
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High Resolution Noise Radar without Fast ADCConventional digital signal processing scheme in noise radars has certain limitations related to combination of high resolution and high dynamic range. The bandwidth of radar signal defines range resolution of any radar: the wider the spectrum the better the resolution. In noise radar with conventional processing the sounding and reference signals are to be digitized at intermediate frequency band and to be processed digitally. The power spectrum bandwidth of noise signal which can be digitized with ADC depends on its sampling rate. In currently available ADCs the faster is sampling rate the smaller is its depth (number of bits). Depth of the ADC determines relation between the smallest and highest observable signals and thus limits its dynamic range. Actually this is the main bottleneck of high resolution Noise Radars: conventional processing does not enable getting high range resolution and high dynamic range at the same time. In the paper we discuss ways to go around this drawback by changing signal processing ideology in noise radar. We present results of our consideration and design of two types of high resolution Noise Radar which uses slow ADCs: noise radar with digital generation of sounding signal and analog evaluation of cross-correlation and stepped frequency noise radar. We describe main ideas of these radar schemes and results of experimental tests of the approaches.
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Kirincich, Anthony. "Toward Real-Time, Remote Observations of the Coastal Wind Resource Using High-Frequency Radar". Marine Technology Society Journal 47, nr 4 (1.07.2013): 206–17. http://dx.doi.org/10.4031/mtsj.47.4.22.
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AbstractThere is now a large installed base of high-frequency (HF) coastal ocean radars in the United States able to measure surface currents on an operational basis. However, these instruments also have the potential to provide estimates of the spatially variable surface wind field over distances ranging from 10 to 200 km offshore. This study investigates the ability of direction-finding HF radars to recover spatial maps of wind speed and direction from the dominant first-order region radar returns using empirical models. Observations of radar backscatter from the Martha’s Vineyard Coastal Observatory HF radar system were compared to wind observations from an offshore tower, finding significant correlations between wind speed and the backscatter power for a range of angles between the wind and radar loop directions. Models for the directional spreading of wind waves were analyzed in comparison to data-based results, finding potentially significant differences between the model and data-based spreading relationships. Using empirical fits, radar-based estimates of wind speed and direction at the location of the in situ wind sensor had error rates of 2 m/s and 60°, which decreased with hourly averaging. Attempts to extrapolate the results to the larger domain illustrated that spatially dependent transfer functions for wind speed and direction appear possible for large coastal ocean domains based on a small number of temporary, or potentially mobile, in situ wind sensors.
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Potapov, A. A., V. A. Kuznetsov i E. A. Alikulov. "Methods for Complexing Images Formed by Multi-Band Synthetic Aperture Radars". Journal of the Russian Universities. Radioelectronics 24, nr 3 (24.06.2021): 6–21. http://dx.doi.org/10.32603/1993-8985-2021-24-3-6-21.
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Introduction. Synthetic aperture radars (SAR) are important components of aviation-based systems for remote sensing of the Earth. The current level of such systems allows simultaneous radar surveys in several frequency ranges. Such surveys require complexing of the images formed in each of the frequency channels, which task is yet to be resolved.Aim. To review the formation principles and methods for joint processing of images using space and aviation-based multi-band synthetic aperture radar systems.Materials and methods. The methodology of systems analysis, involving the integral stages of decomposition, analysis and synthesis, was used. Decomposition of integrating multi-band radar images was performed considering the effect of various factors on the characteristics of radar images in different frequency ranges. Such factors include the principles of radar imaging, issues of radar images of multi-band synthetic aperture radars with real characteristics, and complexing levels.Results. According to the classical systems approach, the results of review and analysis are corresponded by appropriate conclusions on the shortcomings of each decomposition element and the synthesis of a proposal for achieving the goal. It was shown that joint processing of multi-band radar images can be carried out at the levels of signals, pixels, features and solutions, as well as their aggregates. Each approach is characterised by its shortcomings, which impede implementation of full integration of multi-band radar images without loss of information, which is due to the absence of information redundancy of radar images, compared to, e.g., optical images.Conclusion. Recommendations on the application of a particular method and the synthesis of a system for radar complexing images based on the texture-fractal approach were formulated. Directions for further work meeting all the requirements for completeness, reliability and information content of remote sensing of the Earth were outlined.
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Xu, Yanjie, Chunyang Wang, Guimei Zheng i Ming Tan. "Nonlinear Frequency Offset Beam Design for FDA-MIMO Radar". Sensors 23, nr 3 (28.01.2023): 1476. http://dx.doi.org/10.3390/s23031476.
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The beam pattern of frequency diversity array (FDA) radar has a range–angle two-dimensional degree of freedom, which makes it possible to distinguish different targets from the same angle and brings a new approach to anti-jamming of radars. However, the beam pattern of conventional linearly frequency-biased FDA radar is range–angle-coupled and time-varying. The method of adding nonlinear frequency bias among the array elements of the FDA array has been shown to eliminate this coupling property while still allowing for better beam performance of the emitted beam. In this paper, we obtain a decoupled and time-invariant beam direction map using the FDA-multi-input–multi-output (FDA-MIMO) radar scheme and then obtain a sharp pencil-shaped main sphere beam pattern with range–angle dependence using a linear frequency offset scheme weighted by a Chebyshev window. Finally, the anti-interference performance of the proposed method is verified in an anti-interference experiment.
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Duke, Jonathan, Eli Neville i Jorge Vargas. "A Modulated Approach for Improving MFSK RADARS to Resolve Mutual Interference on Autonomous Vehicles (AVs)". Sensors 23, nr 16 (15.08.2023): 7192. http://dx.doi.org/10.3390/s23167192.
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This paper proposes a novel automotive radar waveform involving the theory behind M-ary frequency shift key (MFSK) radar systems. Along with the MFSK theory, coding schemes are studied to provide a solution to mutual interference. The proposed MFSK waveform consists of frequency increments throughout the range of 76 GHz to 81 GHz with a step value of 1 GHz. Instead of stepping with a fixed frequency, a triangular chirp sequence allows for static and moving objects to be detected. Therefore, automotive radars will improve Doppler estimation and simultaneous range of various targets. In this paper, a binary coding scheme and a combined transform coding scheme used for radar waveform correlation are evaluated in order to provide unique signals. AVs have to perform in an environment with a high number of signals being sent through the automotive radar frequency band. Efficient coding methods are required to increase the number of signals that are generated. An evaluation method and experimental data of modulated frequencies as well as a comparison with other frequency method systems are presented.
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Krasnov, Oleg A., i Alexander G. Yarovoy. "Radar micro-Doppler of wind turbines: simulation and analysis using rotating linear wire structures". International Journal of Microwave and Wireless Technologies 7, nr 3-4 (czerwiec 2015): 459–67. http://dx.doi.org/10.1017/s1759078715000641.
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A simple electromagnetic model of wind-turbine's main structural elements as the linear wired structures is developed to simulate the temporal patterns of observed radar return Doppler spectra (micro-Doppler). Using the model, the micro-Doppler for different combinations of the turbines rotation frequency, radar pulse repetition frequency, and duration of the Doppler measurement interval are analyzed. The model is validated using the PARSAX radar experimental data. The model ability to reproduce the observed Doppler spectra main features can be used for development of signal-processing algorithms to suppress the wind-turbines clutter in modern Doppler radars.
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Cai, Bing, Qingchen Xu, Xiong Hu i Junfeng Yang. "Initial Results of Meteor Wind with Langfang Medium Frequency Radar". Atmosphere 11, nr 5 (14.05.2020): 507. http://dx.doi.org/10.3390/atmos11050507.
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We conducted meteor observations during the Leonid meteor shower on 16 November 2017 and 17 November 2018 with Langfang medium frequency (MF) radar (116° E, 40° N). This was the first nighttime meteor observation by MF radar in mid-latitude China. The observation period was 12:00–22:00 (UT) and the observation range was 78–150 km. By using broad vertical beams, totally 94 and 92 meteor echoes were obtained, along with their spatial, time and height distribution. Quite a few meteor echoes are within 30° zenith angles, from the southwest direction, and with a mean height of 107 km which is almost 10 km higher than traditional VHF (Very High Frequency) meteor radar observations. Initial bi-hourly and nightly averaged wind profiles were calculated, and well fitted the wind estimations by co-located VHF meteor radar at the altitude of 100–110 km. On the other side, echoes around 140 km are successfully detected in our observation, which may suggest that for most running MF radars, meteor echoes around 140 km altitude could be detected with a sampling pulse frequency less than 100 Hz.
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Choi, Mun Gak, Dong Sik Woo, Hyun Chul Choi i Kang Wook Kim. "High-Accuracy AM-FM Radar with an Active Reflector". Journal of Sensors 2017 (2017): 1–8. http://dx.doi.org/10.1155/2017/8589469.
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An amplitude-modulated and frequency-modulated (AM-FM) radar with an active reflector to produce high-accuracy distance measurements is proposed and demonstrated in this paper. The proposed radar consists of an AM-FM base module and an active reflector. The combination of AM and FM modulations resolves ambiguity of the absolute distance in typical AM radars, while improving range accuracy in typical FM radars with narrow bandwidth. Also, the active reflector, which translates the frequency of the received signal, resolves the problem of phase detection interference due to the direct Tx-to-Rx leakage in AM radars. In this paper, the operating principle, experimental tests, and analysis are presented. The implemented AM-FM radar operates in X-band (Tx: 10.5 GHz, Rx: 8.5 GHz) with the 620 MHz bandwidth. The measured range accuracy of less than ±10 mm at a distance of 70 m is obtained.
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Hou, Yidong, Biyang Wen, Yonghuai Yang, Jing Yang i Caijun Wang. "Two-Dimensional River Flow Patterns Observed with a Pair of UHF Radar System". International Journal of Antennas and Propagation 2017 (2017): 1–11. http://dx.doi.org/10.1155/2017/4792324.
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A pair of ultrahigh-frequency (UHF) radars system for measuring the two-dimensional river flow patterns is presented. The system consists of two all-digital UHF radars with exactly the same hardware structure, operating separately at 329–339 MHz and 341–351 MHz. The adoption of direct radio frequency (RF) sampling technique and digital pulse compression simplifies the structure of radar system and eliminates the distortion introduced by the analog mixer, which improves the SNR and dynamic range of the radar. The field experiment was conducted at Hanjiang River, Hubei province, China. Over a period of several weeks, the radar-derived surface velocity has been very highly correlated with the measurements of EKZ-I, with a correlation coefficient of 0.958 and a mean square error of 0.084 m/s.
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Franck, Anna, Dmitri Moisseev, Ville Vakkari, Matti Leskinen, Janne Lampilahti, Veli-Matti Kerminen i Ewan O'Connor. "Evaluation of convective boundary layer height estimates using radars operating at different frequency bands". Atmospheric Measurement Techniques 14, nr 11 (24.11.2021): 7341–53. http://dx.doi.org/10.5194/amt-14-7341-2021.
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Abstract. Knowledge of the atmospheric boundary layer state and evolution is important for understanding air pollution and low-level cloud development, among other things. There are a number of instruments and methods that are currently used to estimate boundary layer height (BLH). However, no single instrument is capable of providing BLH measurements in all weather conditions. We proposed a method to derive a daytime convective BLH using clear air echoes in radar observations and investigated the consistency of these retrievals between different radar frequencies. We utilized data from three vertically pointing radars that are available at the SMEAR II station in Finland, i.e. the C band (5 GHz), Ka band (35 GHz) and W band (94 GHz). The Ka- or W-band cloud radars are an integral part of cloud profiling stations of pan-European Aerosol, Clouds and Trace Gases Research Infrastructure (ACTRIS). Our method will be utilized at ACTRIS stations to serve as an additional estimate of the BLH during summer months. During this period, insects and Bragg scatter are often responsible for clear air echoes recorded by weather and cloud radars. To retrieve a BLH, we suggested a mechanism to separate passive and independently flying insects that works for all analysed frequency bands. At the lower frequency (the C band) insect scattering has been separated from Bragg scattering using a combination of the radar reflectivity factor and linear depolarization ratio. Retrieved values of the BLH from all radars are in a good agreement when compared to the BLH obtained with the co-located HALO Doppler lidar and ERA5 reanalysis data set. Our method showed some underestimation of the BLH after nighttime heavy precipitation yet demonstrated a potential to serve as a reliable method to obtain a BLH during clear-sky days. Additionally, the entrainment zone was observed by the C-band radar above the CBL in the form of a Bragg scatter layer. Aircraft observations of vertical profiles of potential temperature and water vapour concentration, collected in the vicinity of the radar, demonstrated some agreement with the Bragg scatter layer.
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Ibragimova, Ya G., O. A. Tereshenkova, A. A. Kim i V. S. Luginya. "Methods and tools for radio frequency locators parameters verification". Radio industry (Russia) 30, nr 2 (6.06.2020): 8–17. http://dx.doi.org/10.21778/2413-9599-2020-30-2-8-17.
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Radio frequency locators, or radars, are one of the most common and effective devices of remote sensing of the atmosphere which are used to detect and recognize distant objects, measure their dynamic parameters, or research the properties of the atmosphere. The methods and tools for verifying their operational parameters are of great interest, since the specificity of the radar in most cases makes it difficult to verify them due to the impossibility of creating a reference atmospheric path. To date, there is no single methodology for assessing the control of the basic operational parameters of radars. The methods and technical tools used are often difficult to implement, have a narrow range of applications and require confirmation of their own characteristics. The article presents the classification and analysis results of existing methods and technical tools of radio frequency locators operational parameters verification. Based on the analysis, recommendations for choosing an approach to conducting verification measures depending on the type of radar are given.
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Zhu, Langfeng, Tianyi Lu, Fan Yang, Bin Liu, Lunyu Wu i Jun Wei. "Comparisons of Tidal Currents in the Pearl River Estuary between High-Frequency Radar Data and Model Simulations". Applied Sciences 12, nr 13 (27.06.2022): 6509. http://dx.doi.org/10.3390/app12136509.
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High-frequency (HF) radar data, derived from a pair of newly developed radar stations in the Pearl River Estuary (PRE) of China, were validated through comparison with in situ surface buoys, ADCP measurements, and model simulations in this study. Since no in situ observations are available in the radar observing domain, a regional high-resolution ocean model covering the entire PRE and its adjacent seas was first established and validated with in situ measurements, and then the HF radar data quality was examined against the model simulations. The results show that mean flows and tidal ellipses derived from the in situ buoys and ADCP were in very good agreement with the model. The model–radar data comparison indicated that the radar obtained the best data quality within the central overlapping area between the two radar stations, with the errors increasing toward the coast and the open ocean. Near the coast, the radar data quality was affected by coastlines and islands that prevent HF radar from delivering high-quality information for determining surface currents. This is one of the major drawbacks of the HF radar technique. Toward the open ocean, where the wind is the only dominant forcing on the tidal currents, we found that the poor data quality was most likely contaminated by data inversion algorithms from the Shangchuan radar station. A hybrid machine-learning-based inversion algorithm including traditional electromagnetic analysis and physical oceanography factors is needed to develop and improve radar data quality. A new radar observing network with about 10 radar stations is developing in the PRE and its adjacent shelf, this work assesses the data quality of the existing radars and identifies the error sources, serving as the first step toward the full deployment of the entire radar network.
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Arnold, Emily, Carl Leuschen, Fernando Rodriguez-Morales, Jilu Li, John Paden, Richard Hale i Shawn Keshmiri. "CReSIS airborne radars and platforms for ice and snow sounding". Annals of Glaciology 61, nr 81 (19.11.2019): 58–67. http://dx.doi.org/10.1017/aog.2019.37.
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AbstractThis paper provides an update and overview of the Center for Remote Sensing of Ice Sheets (CReSIS) radars and platforms, including representative results from these systems. CReSIS radar systems operate over a frequency range of 14–38 GHz. Each radar system's specific frequency band is driven by the required depth of signal penetration, measurement resolution, allocated frequency spectra, and antenna operating frequencies (often influenced by aircraft integration). We also highlight recent system advancements and future work, including (1) increasing system bandwidth; (2) miniaturizing radar hardware; and (3) increasing sensitivity. For platform development, we are developing smaller, easier to operate and less expensive unmanned aerial systems. Next-generation platforms will further expand accessibility to scientists with vertical takeoff and landing capabilities.
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Pazmany, Andrew L., James B. Mead, Howard B. Bluestein, Jeffrey C. Snyder i Jana B. Houser. "A Mobile Rapid-Scanning X-band Polarimetric (RaXPol) Doppler Radar System". Journal of Atmospheric and Oceanic Technology 30, nr 7 (1.07.2013): 1398–413. http://dx.doi.org/10.1175/jtech-d-12-00166.1.
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Abstract A novel, rapid-scanning, X-band (3-cm wavelength), polarimetric (RaXPol), mobile radar was developed for severe-weather research. The radar employs a 2.4-m-diameter dual-polarized parabolic dish antenna on a high-speed pedestal capable of rotating the antenna at 180° s−1. The radar can complete a 10-elevation-step volume scan in about 20 s, while maintaining a 180-record-per-second data rate. The transmitter employs a 20-kW peak-power traveling wave tube amplifier that can generate pulse compression and frequency-hopping waveforms. Frequency hopping permits the acquisition of many more independent samples possible than without frequency hopping, making it possible to scan much more rapidly than conventional radars. Standard data products include vertically and horizontally polarized equivalent radar reflectivity factor, Doppler velocity mean and standard deviation, copolar cross-correlation coefficient, and differential phase. This paper describes the radar system and illustrates the capabilities of the radar through selected analyses of data collected in the U.S. central plains during the 2011 spring tornado season. Also noted are opportunities for experimenting with different signal-processing techniques to reduce beam smearing, increase sensitivity, and improve range resolution.
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Alvarez-Lopez, Yuri, Cebrian Garcia-Gonzalez, Carlos Vazquez-Antuna, Samuel Ver-Hoeye i Fernando Las-Heras. "FREQUENCY SCANNING BASED RADAR SYSTEM". Progress In Electromagnetics Research 132 (2012): 275–96. http://dx.doi.org/10.2528/pier12071811.
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Headrick, J. M., i J. F. Thomason. "Applications of high-frequency radar". Radio Science 33, nr 4 (lipiec 1998): 1045–54. http://dx.doi.org/10.1029/98rs01013.
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Chadwick, A. "Superresolution for high-frequency radar". IET Radar, Sonar & Navigation 1, nr 6 (2007): 431. http://dx.doi.org/10.1049/iet-rsn:20060176.
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Seyfried, Daniel, i Joerg Schoebel. "Stepped-frequency radar signal processing". Journal of Applied Geophysics 112 (styczeń 2015): 42–51. http://dx.doi.org/10.1016/j.jappgeo.2014.11.003.
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Huo, Juan, Yongheng Bi, Bo Liu, Congzheng Han i Minzheng Duan. "A Dual-Frequency Cloud Radar for Observations of Precipitation and Cloud in Tibet: Description and Preliminary Measurements". Remote Sensing 13, nr 22 (19.11.2021): 4685. http://dx.doi.org/10.3390/rs13224685.
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A new dual-frequency Doppler polarimetric cloud radar (DDCR), working at 35-GHz (Ka-band radar, wavelength: 8.6 mm) and 94-GHz (W-band radar, wavelength: 3.2 mm) frequencies, has been in operation at Yangbajing Observatory on the Tibetan Plateau (China) for more than a year at the time of writing. Calculations and field observations show that the DDCR has a high detection sensitivity of −39.2 dBZ at 10 km and −33 dBZ at 10 km for the 94-GHz radar and 35-GHz radar, respectively. The radar reflectivity measured by the two radars illustrates different characteristics for different types of cloud: for precipitation, the attenuation caused by liquid cloud droplets is obviously more serious for the 94-GHz radar than the 35-GHz radar (the difference reaches 40 dB in some cases), and the 94-GHz radar lost signals due to serious attenuation by heavy rainfall; while for clouds dominated by ice crystals where the attenuation significantly weakens, the 94-GHz radar shows better detection ability than the 35-GHz radar. Observations in the Tibetan region show that the 35-GHz radar is prone to missing cloud near the edge, such as the cloud-top portion, resulting in underestimation of the cloud-top height (CTH). Statistical analysis based on one year of observations shows that the mean CTH measured by the 94-GHz radar in the Tibetan region is approximately 600 m higher than that measured by the 35-GHz radar. The analysis in this paper shows that the DDCR, with its dual-frequency design, provides more valuable information than simpler configurations, and will therefore play an important role in improving our understanding of clouds and precipitation in the Tibetan region.
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Junyent, Francesc, V. Chandrasekar, V. N. Bringi, S. A. Rutledge, P. C. Kennedy, D. Brunkow, J. George i R. Bowie. "Transformation of the CSU–CHILL Radar Facility to a Dual-Frequency, Dual-Polarization Doppler System". Bulletin of the American Meteorological Society 96, nr 6 (1.06.2015): 975–96. http://dx.doi.org/10.1175/bams-d-13-00150.1.
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Abstract This paper describes the transformation of the Colorado State University–University of Chicago–Illinois State Water Survey (CSU–CHILL) National Radar Facility from a single-frequency (S band) dual-polarization Doppler weather radar system to a dual-frequency (S and X bands) dual-polarization Doppler system with coaxial beams. A brief history regarding the development of dual-wavelength radars is first presented. In the past, dual-wavelength measurements were used to detect hail using the dual-wavelength ratio defined as the ratio of intrinsic (or attenuation corrected) X-band reflectivity to the S-band reflectivity. Departures of this ratio from unity were taken to indicate the presence of hail, produced by Mie scattering at the shorter wavelength by hail. Most dual-wavelength radars were developed with attempts to match beams for S and X bands, which implies that the sample volumes for the two frequencies were essentially the same. The X-band channel of the CSU–CHILL radar takes a different approach, that of making use of the already existing dual-offset-fed antenna designed to give a 1° beamwidth at S band, resulting in an X-band beamwidth of approximately 0.3°, with very high gain. Thus, the X band provides about a factor of 3 more resolution than the S-band component while maintaining the same sensitivity as the S-band component. Examples of cold season and warm season data from the X-band and S-band radar components are presented, demonstrating the successful transformation of the CSU–CHILL radar into a unique multifrequency, multipolarization system. The new CSU–CHILL dual-wavelength, dual-polarization weather radar will serve as an important asset for the scientific community.
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Yaghoubi Aliabad, Pourya, Hossein Soleimani i Mohammad Soleimani. "Reducing the Sidelobes in Doppler-Range Beam Pattern and Controlling the Frequency Channel in SIAR". Wireless Communications and Mobile Computing 2023 (24.08.2023): 1–12. http://dx.doi.org/10.1155/2023/3451354.
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Synthetic impulse and aperture radar (SIAR) is a multi-input multi-output orthogonal multicarrier frequency radar, kind of frequency diverse array (FDA). This radar has omnidirectional emission in the transmitter and each receiver or receiving array can form a beam. The 4D matched filter of this radar’s circular arrays can reveal the range, elevation angle, azimuth angle, and Doppler. The existence of a high sidelobe in the range-Doppler is one of the significant challenges of this radar, and pulse-to-pulse frequency code non-agile (PPFCNA) and pulse-to-pulse frequency code agile (PPFCA) are often used to reduce it. Weighting is one of the available methods for reducing sidelobes in array radars, but weighting in the matched filter is more effective in SIAR radars due to their ability to transmit signals with different and orthogonal frequencies. This paper proposes the use of amplitude weighting in the submatched filter, which is made possible by increasing the degree of freedom in the SIAR process. In this method, each receiver’s signal is independently processed and weighted with a submatched filter. Then, a synthetic pulse is formed by combining the data from multiple channels. The output of the simulation with weighting in the matched filter for the PPFCNA indicates an 8.7908 dB reduction in sidelobes, while the output for the PPFCA indicates a 3.3779 dB reduction in sidelobes.
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Zhao, Hong-Ze, Guang-Hui Wei, Xiao-Dong Pan, Xue Du i Xu-Xu Lyu. "Pseudo-Signal Interference Regularity of Single-Frequency Electromagnetic Radiation to Stepped-Frequency Radar". Electronics 11, nr 17 (2.09.2022): 2768. http://dx.doi.org/10.3390/electronics11172768.
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When typical radar equipment is subjected to single-frequency electromagnetic radiation, the radar display interface forms a pseudo-signal, resulting in the misjudgment of real targets. Based on the working principle of stepped-frequency radar ranging, the effect mechanism of radar equipment pseudo-signal interference is revealed. Taking a Ku band stepped-frequency ranging radar as the test object, the pseudo-signal interference effect test of single-frequency electromagnetic radiation is carried out in this study. The pseudo-signal level value of 6 dBmV is selected as the sensitive criterion of the pseudo-signal interference effect. Through experiments, the variation curves of the pseudo-signal level values of the sensitive frequency bands and the typical frequency points inside and outside the band with the field strength of the single-frequency interference are obtained. Based on the nonlinear distortion analysis of the receiving circuit, the variation laws of the pseudo-signal level values inside and outside the band are explained, respectively. The experimental results show that there are at least seven pseudo-signal interference-sensitive bands in the tested radar, and the first pseudo-signal strength is only related to the interference signal strength. The essence of the second type of pseudo-signal interference is intermodulation interference, and the pseudo-signal level is related to the interference signal and the useful signal strength.
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Lombardo, F., F. Napolitano, F. Russo, G. Scialanga, L. Baldini i E. Gorgucci. "Rainfall estimation and ground clutter rejection with dual polarization weather radar". Advances in Geosciences 7 (16.02.2006): 127–30. http://dx.doi.org/10.5194/adgeo-7-127-2006.
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Abstract. Conventional radars, used for atmospheric remote sensing, usually operate at a single polarization and frequency to estimate storm parameters such as rainfallrate and water content. Because of the high variability of the drop size distribution conventional radars do not succeed in obtaining detailed information because they just use horizontal reflectivity. The potentiality of the dual-polarized weather radar is investigated, in order to reject the ground-clutter, using differential reflectivity. In this light, a radar meteorology campaign was conducted over the city of Rome (Italy), collecting measurements by the polarimetric Doppler radar Polar 55C and by a raingauge network. The goodness of the results is tested by comparison of radar rainfall estimates with raingauges rainfall measurements.
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Lakshmi, K. Jansi, i K. Surya Narayana Reddy. "Implementation of High Speed Self Switching Frequency Agile RADAR". International Journal of Reconfigurable and Embedded Systems (IJRES) 3, nr 1 (1.03.2013): 11. http://dx.doi.org/10.11591/ijres.v3.i1.pp11-17.
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<div class="WordSection1"><p><strong><a href="mailto:suryak1986@yahoo.com"></a></strong></p></div><strong> </strong>The radar has to resist diversified jamming; High Speed self-adaptive frequency agility is an important and effective function for radars to resist jamming. The procedure to achieve this function are described, and the function is realized with FPGA using Hardware description Language, the validity is proved by on- line sampling and simulation. The High speed self-adaptive frequency agility module can analyze the type of jamming to select transmitting frequency to avoid the frequencies which have interference, under frequency diversity and fixed frequency, respectively. The general application on a searching radar shows that the module has good real-time and anti- jamming capacity.
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Cao, Yu Peng, Yang Zhang, Jun Luo, Fu Sheng Jian, Xi Guo Dai, Zhu Qun Zhai, Xiao Ying Ma i in. "Simulation Detection Power of Shore-Based Radar under the Influence of Sea Clutter". Advanced Materials Research 1049-1050 (październik 2014): 1200–1204. http://dx.doi.org/10.4028/www.scientific.net/amr.1049-1050.1200.
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According to the principle of electromagnetic wave propagation and the model of radar multipath propagation, this paper established radar detection power model in natural space under the impact of sea clutter, and on condition that conducting simulations to study detection power of shore-based radars on different altitudes and different operating frequencies. Simulation results indicate that when the radar operating frequency is constant, with the erection height increases, the detection range will increase at the same time, while significantly reduced about blind region. When the radar erection height is constant, blind region is filled with radars working at C, S and X operating frequencies. The effect of blind filling is of great importance for adjacent bands. This paper provides theoretical reference analysis for radar detection power assessing and overall with a strong engineering application value.
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Mercuri, Marco, Paweł Barmuta, Ping Jack Soh, Paul Leroux i Dominique Schreurs. "Monostatic continuous-wave radar integrating a tunable wideband leakage canceler for indoor tagless localization". International Journal of Microwave and Wireless Technologies 9, nr 8 (22.05.2017): 1583–90. http://dx.doi.org/10.1017/s1759078717000551.
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Continuous-wave (CW) radars have been recently investigated in healthcare aiming at contactless health monitoring. However, a major problem in monostatic CW architectures is represented by the unwanted leakage produced by poor isolation between transmitter and receiver, which can drastically decrease the receiver's sensitivity reducing therefore the radar dynamic range. Although this situation can be easily controlled in case of narrowband CW radar by an appropriate passive microwave design, it becomes much more complicated in case of stepped-frequency CW and frequency-modulated CW architectures that present an ultra-wideband nature. In this paper, a monostatic CW radar integrating a tunable wideband leakage canceler aiming at indoor tagless localization is presented and discussed. The use of the feedforward canceler allows a strong reduction of the unwanted leakage over the whole radar bandwidth. Experimental results demonstrate the feasibility of this approach, showing an outstanding improvement of the radar dynamic range.