Journal articles on the topic 'Clutter echoe'
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1
Lu, Qing Qing, Jie Xin Pu, Xiao Hong Wang, and Zhong Hua Liu. "A Clutter Suppression Algorithm for GPR Data Based on PCA Combining with Gradient Magnitude." Applied Mechanics and Materials 644-650 (September 2014): 1662–67. http://dx.doi.org/10.4028/www.scientific.net/amm.644-650.1662.
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Ground penetrating radar (GPR) is a powerful tool for detecting defects behind reinforced concrete (RC) structures. However, the received data from GPR includes a large number of clutters which are easy overwhelming the signal of target. In order to successfully extract the target signature, these clutters effects need to be eliminated. In this article, a clutter suppression algorithm based on Principal Component Analysis (PCA) combining with gradient magnitude is presented. PCA clutter suppression algorithm is applied to the data and removes most of the echoes from ground surface and portion of other clutters with weak energy. Then gradient magnitude clutter suppression is used to remove majority of the residue clutters. It is demonstrated from simulation that the proposed algorithm is able to significantly suppress the clutters and is superior to the PCA clutter suppression, magnitude clutter suppression and means subtraction method.
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Hubbert, J. C., M. Dixon, and S. M. Ellis. "Weather Radar Ground Clutter. Part II: Real-Time Identification and Filtering." Journal of Atmospheric and Oceanic Technology 26, no. 7 (July 1, 2009): 1181–97. http://dx.doi.org/10.1175/2009jtecha1160.1.
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Abstract The identification and mitigation of anomalous propagation (AP) and normal propagation (NP) ground clutter is an ongoing problem in radar meteorology. Scatter from ground-clutter targets routinely contaminates radar data and masks weather returns causing poor data quality. The problem is typically mitigated by applying a clutter filter to all radar data, but this also biases weather data at near-zero velocity. Modern radar processors make possible the real-time identification and filtering of AP clutter. A fuzzy logic algorithm is used to distinguish between clutter echoes and precipitation echoes and, subsequently, a clutter filter is applied to those radar resolution volumes where clutter is present. In this way, zero-velocity weather echoes are preserved while clutter echoes are mitigated. Since the radar moments are recalculated from clutter-filtered echoes, the underlying weather echo signatures are revealed, thereby significantly increasing the visibility of weather echo. This paper describes the fuzzy logic algorithm, clutter mitigation decision (CMD), for clutter echo identification. A new feature field, clutter phase alignment (CPA), is introduced and described. A detailed discussion of CPA is given in Part I of this paper. The CMD algorithm is illustrated with experimental data from the Denver Next Generation Weather Radar (NEXRAD) at the Denver, Colorado, Front Range Airport (KFTG); and NCAR’s S-band dual-polarization Doppler radar (S-Pol).
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Xu, Yong, Tao Jia, Dong Cao, Pengyu Guo, Yue Ma, and Hongtao Yan. "Adaptive Clustering-Based Marine Radar Sea Clutter Normalization." Journal of Sensors 2021 (October 22, 2021): 1–11. http://dx.doi.org/10.1155/2021/2938251.
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Radar sea clutters are echoes reflected from a patch of ocean surface, which may significantly interfere with the signals from targets, and seriously degrade the performance of marine radar remote sensing. Thus, it is vital to eliminate the effects of sea clutter. In this paper, we aim at normalizing sea clutter to a uniform level. Firstly, a detailed analysis about the characteristics and differences of clutter and targets is presented; then, we present a heuristic processing scheme which works by solving the task of sea clutter normalization as a classification problem followed by energy normalization. Multiscale and speed-up strategies are incorporated into the dynamic clustering algorithm to found a robust real-time normalization method. Finally, extensive experiments show state-of-the-art results on challenging sea clutter echoes, which demonstrate the feasibility and robustness of the proposed adaptive clustering normalization method.
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Zhang, Xin, Qiang Yang, and Weibo Deng. "Weak Target Detection within the Nonhomogeneous Ionospheric Clutter Background of HFSWR Based on STAP." International Journal of Antennas and Propagation 2013 (2013): 1–11. http://dx.doi.org/10.1155/2013/382516.
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High Frequency Surface Wave Radar (HFSWR) can perform the functions of ocean environment monitoring, target detection, and target tracking over the horizon. However, its system's performance is always limited by the severe ionospheric clutter environment, especially by the nonhomogeneous component. The nonhomogeneous ionospheric clutter generally can cover a few Doppler shift units and a few angle units. Consequently, weak targets masked by the nonhomogeneous ionospheric clutter are difficult to be detected. In this paper, a novel algorithm based on angle-Doppler joint eigenvector which considers the angle-Doppler map of radar echoes is adopted to analyze the characteristics of the nonhomogeneous ionospheric clutter. Given the measured data set, we first investigate the correlation between the signal of interest (SOI) and the nonhomogeneous ionospheric clutter and then the correlation between the nonhomogeneous ionospheric clutters in different two ranges. Finally, a new strategy of training data selection is proposed to improve the joint domain localised (JDL) algorithm. Simulation results show that the improved-JDL algorithm is effective and the performance of weak target detection within nonhomogeneous ionospheric clutter is improved.
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Hubbert, J. C., M. Dixon, S. M. Ellis, and G. Meymaris. "Weather Radar Ground Clutter. Part I: Identification, Modeling, and Simulation." Journal of Atmospheric and Oceanic Technology 26, no. 7 (July 1, 2009): 1165–80. http://dx.doi.org/10.1175/2009jtecha1159.1.
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Abstract Real-time ground-clutter identification and subsequent filtering of clutter-contaminated data is addressed in this two-part paper. Part I focuses on the identification, modeling, and simulation of S-band ground-clutter echo. A new clutter identification parameter, clutter phase alignment (CPA), is presented. CPA is a measure primarily of the phase variability of the in-phase and quadrature-phase time series samples for a given radar resolution volume. CPA is also a function of amplitude variability of the time series. It is shown that CPA is an excellent discriminator of ground clutter versus precipitation echoes. A typically used weather model, time series simulator is shown to inadequately describe experimentally observed CPA. Thus, a new technique for the simulation of ground-clutter echo is developed that better predicts the experimentally observed CPA. Experimental data from the Denver Next Generation Weather Radar (NEXRAD) at the Denver, Colorado, Front Range Airport (KFTG), and NCAR’s S-band dual-polarization Doppler radar (S-Pol) are used to illustrate CPA. In Part II, CPA is used in a fuzzy logic algorithm for improved clutter identification.
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Ming, Chen, Stephanie Haro, Andrea Megela Simmons, and James A. Simmons. "A comprehensive computational model of animal biosonar signal processing." PLOS Computational Biology 17, no. 2 (February 17, 2021): e1008677. http://dx.doi.org/10.1371/journal.pcbi.1008677.
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Computational models of animal biosonar seek to identify critical aspects of echo processing responsible for the superior, real-time performance of echolocating bats and dolphins in target tracking and clutter rejection. The Spectrogram Correlation and Transformation (SCAT) model replicates aspects of biosonar imaging in both species by processing wideband biosonar sounds and echoes with auditory mechanisms identified from experiments with bats. The model acquires broadband biosonar broadcasts and echoes, represents them as time-frequency spectrograms using parallel bandpass filters, translates the filtered signals into ten parallel amplitude threshold levels, and then operates on the resulting time-of-occurrence values at each frequency to estimate overall echo range delay. It uses the structure of the echo spectrum by depicting it as a series of local frequency nulls arranged regularly along the frequency axis of the spectrograms after dechirping them relative to the broadcast. Computations take place entirely on the timing of threshold-crossing events for each echo relative to threshold-events for the broadcast. Threshold-crossing times take into account amplitude-latency trading, a physiological feature absent from conventional digital signal processing. Amplitude-latency trading transposes the profile of amplitudes across frequencies into a profile of time-registrations across frequencies. Target shape is extracted from the spacing of the object’s individual acoustic reflecting points, or glints, using the mutual interference pattern of peaks and nulls in the echo spectrum. These are merged with the overall range-delay estimate to produce a delay-based reconstruction of the object’s distance as well as its glints. Clutter echoes indiscriminately activate multiple parts in the null-detecting system, which then produces the equivalent glint-delay spacings in images, thus blurring the overall echo-delay estimates by adding spurious glint delays to the image. Blurring acts as an anticorrelation process that rejects clutter intrusion into perceptions.
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Hui, Jian Xin, Lei Wu, Yu Chun Gao, and Jie Zhou. "A Spectral Moment Estimation Method for Wind Profile Radar." Advanced Materials Research 179-180 (January 2011): 740–45. http://dx.doi.org/10.4028/www.scientific.net/amr.179-180.740.
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Spectrum in the wind profile radar data processing, radar detection of low-level spectral data from the library there are usually clutter, intermittent clutter, clutter and atmospheric echoes magnetic mixed overlap situation. In order to effectively restrain and remove clutter and increase the wind profile radar detection range and accuracy, must be on the air back to the effective spectrum of the spectral moments estimation. Based on the wind profile radar Doppler echo power spectral analysis, maximum likelihood method based on estimated spectral data of radar echo spectrum method using MATLAB simulation analysis , compared with the conventional method of analysis to verify the feasibility and effectiveness of the algorithm, also, try the algorithm is applied to the complexity of the weather with a strong interference case of precipitation particles; Data analysis showed that the actual detection, from the library in the lower spectrum moment estimation has been improved significantly.
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Jensen, M. E., L. A. Miller, and J. Rydell. "Detection of prey in a cluttered environment by the northern bat Eptesicus nilssonii." Journal of Experimental Biology 204, no. 2 (January 15, 2001): 199–208. http://dx.doi.org/10.1242/jeb.204.2.199.
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We studied the acoustic behaviour of bats (Eptesicus nilssonii) hunting for large (wing span 5 cm) non-hearing hepialid moths (Hepialus humuli). Groups of silvery-white male H. humuli perform a short (30 min) hovering display flight over grassland at dusk. They typically hover at, or below, the tops of grass panicles and are therefore situated in a highly acoustically cluttered habitat. Occasionally, they move to a new position by making short (1–5 s) flights at higher levels. E. nilssonii is not a clutter specialist, and yet we found that they attacked H. humuli within the ‘clutter overlap zone’. The bats did not change their signal design in any marked manner for this specific task. Measurements of echoes from a moth 10 cm above or below the grass tops showed that information for detecting the moths was available to the bats. Nevertheless, the bats did not attack moths in stationary hovering display flight, only when they moved above the grass panicles. The duration of the up/down flights (movements) were almost always longer than an entire capture sequence by the bats. Apparently, the bats rely on the movement of the moth in space, monitored over successive echoes, to discriminate moth echoes from overlapping clutter echoes.
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Oh, Young-A., Hae-Lim Kim, and Mi-Kyung Suk. "Clutter Elimination Algorithm for Non-Precipitation Echo of Radar Data Considering Meteorological and Observational Properties in Polarimetric Measurements." Remote Sensing 12, no. 22 (November 18, 2020): 3790. http://dx.doi.org/10.3390/rs12223790.
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Non-precipitation echoes due to ground and sea clutter, chaff, anomalous propagation, biological targets, and interference in weather radar observations are major issues causing a decline in the accuracy of meteorological and hydrological applications based on radar data. Statistically based quality control techniques using polarimetric variables have improved the accuracy of radar echo classification, however their performance is affected by attenuation, nonuniform beam filling, and hydrometeor diversity as well as terrain blockage, beam broadening, and noise correction issues due to the quality degradation of polarimetric measurements. To address this, a new quality control algorithm, named clutter elimination algorithm for non-precipitation echo of radar data (CLEANER), was designed by employing independent feature parameters and variable classification conditions with spatial and temporal observation environments to adapt to these meteorological artifacts and observational limitations. CLEANER was applied to several precipitation cases with various non-precipitation echoes, showing improved performance compared with results from the fuzzy logic-based quality control algorithm in terms of non-precipitation echo removal as well as in precipitation echo conservation. In addition, CLEANER shows better computational efficiency and robustness, as well as an excellent expandability for different radar networks.
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Sud, Seema. "Noise and Interference Suppression in Sonar Echoes Using the Fractional Fourier Transform." European Journal of Engineering Research and Science 2, no. 7 (July 25, 2017): 40. http://dx.doi.org/10.24018/ejers.2017.2.7.422.
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The Fractional Fourier Transform (FrFT) enables separation of signals from noise and interference by utilizing the entire time-frequency space. Signals are filtered by rotating to a new time axis ‘ta’, with rotational parameter ‘a’, selected using some metric such as mean-square error (MSE) between a desired signal-of-interest (SOI) and its estimate. The FrFT has been applied to numerous problems, but it is most suited for applications such as sonar and radar, when the time-frequency distribution of the SOI and the undesired environment are different. It can greatly outperform the conventional fast Fourier Transform (FFT), which is solely a frequency domain method (a=1), as well as conventional time-based MMSE adaptive filtering (a=0). In this paper, we present a simple FrFT-based algorithm that separates sonar echoes of a desired SOI, e.g. a chirp, from the cluttered background, which could be noise or interference (i.e. another signal). We exploit the fact that we can find the best time axis ‘ta’ in which the SOI becomes a tone, or close to it, with the FrFT, enabling easy notching (zeroing) of the clutter. By searching for the tone peak and notching everywhere except the peak, we can successfully and easily remove the clutter. This algorithm is robust because clutter typically does not correlate with the signal in the FrFT domain, and thus does not impair our ability to estimate the peaks and notch the clutter. We compute the MSE between the true transmitted signal and the received echo with and without this algorithm as a function of signal-to-noise ratio (SNR) and show that 5 dB reduction in MSE is possible with the FrFT.
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Sud, Seema. "Noise and Interference Suppression in Sonar Echoes Using the Fractional Fourier Transform." European Journal of Engineering and Technology Research 2, no. 7 (July 25, 2017): 40–44. http://dx.doi.org/10.24018/ejeng.2017.2.7.422.
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The Fractional Fourier Transform (FrFT) enables separation of signals from noise and interference by utilizing the entire time-frequency space. Signals are filtered by rotating to a new time axis ‘ta’, with rotational parameter ‘a’, selected using some metric such as mean-square error (MSE) between a desired signal-of-interest (SOI) and its estimate. The FrFT has been applied to numerous problems, but it is most suited for applications such as sonar and radar, when the time-frequency distribution of the SOI and the undesired environment are different. It can greatly outperform the conventional fast Fourier Transform (FFT), which is solely a frequency domain method (a=1), as well as conventional time-based MMSE adaptive filtering (a=0). In this paper, we present a simple FrFT-based algorithm that separates sonar echoes of a desired SOI, e.g. a chirp, from the cluttered background, which could be noise or interference (i.e. another signal). We exploit the fact that we can find the best time axis ‘ta’ in which the SOI becomes a tone, or close to it, with the FrFT, enabling easy notching (zeroing) of the clutter. By searching for the tone peak and notching everywhere except the peak, we can successfully and easily remove the clutter. This algorithm is robust because clutter typically does not correlate with the signal in the FrFT domain, and thus does not impair our ability to estimate the peaks and notch the clutter. We compute the MSE between the true transmitted signal and the received echo with and without this algorithm as a function of signal-to-noise ratio (SNR) and show that 5 dB reduction in MSE is possible with the FrFT.
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Ji, Xiaowei, Qiang Yang, and Linwei Wang. "A Self-Regulating Multi-Clutter Suppression Framework for Small Aperture HFSWR Systems." Remote Sensing 14, no. 8 (April 14, 2022): 1901. http://dx.doi.org/10.3390/rs14081901.
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The problem that this paper is concerned with is High Frequency Surface Wave Radar (HFSWR) detection of desired targets against a complex interference background consisting of sea clutter, ionosphere clutter, Radio Frequency Interference (RFI) and atmospheric noise. Eliminating unwanted echoes and exploring obscured targets contribute to achieving ideal surveillance of sea surface targets. In this paper, a Self-regulating Multi-clutter Suppression Framework (SMSF) has been proposed for small aperture HFSWR. SMSF can remove many types of clutter or RFI; meanwhile, it mines the targets merged into clutter and tracks the travelling path of the ship. In SMSF, a novel Dynamic Threshold Mapping Recognition (DTMR) method is first proposed to reduce the atmospheric noise and recognize each type of unwanted echo; these recognized echoes are fed into the proposed Adaptive Prophase-current Dictionary Learning (APDL) algorithm. To make a comprehensive evaluation, we also designed three novel assessment parameters: Obscured Targets Detection Rate (OTDR), Clutter Purification Rate (CPR) and Erroneous Suppression Rate (ESR). The experiment data collected from a small aperture HFSWR system confirm that SMSF has precise suppression performance over most of the classical algorithms and concurrently reveals the moving targets, and OTDR of SMSF is usually higher than compared methods.
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Wu, Chong, Liping Liu, Chao Chen, Chian Zhang, Guangxin He, and Juan Li. "Challenges of the Polarimetric Update on Operational Radars in China—Ground Clutter Contamination of Weather Radar Observations." Remote Sensing 13, no. 2 (January 10, 2021): 217. http://dx.doi.org/10.3390/rs13020217.
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China New Generation Doppler Weather Radar (CINRAD) plans to upgrade its hardware and software to achieve polarimetric function. However, the small-magnitude polarimetric measurements were negatively affected by the scattering characteristics of ground clutter and the filter’s response to the ground clutter. This polarimetric contamination was characterized by decreased differential reflectivity (ZDR) and cross-correlation coefficient (ρhv), as well as an increased standard deviation of the differential phase (ΦDP), generating a large-area and long-term observational anomaly for eight polarimetric radars in South China. Considering that outliers simultaneously appeared in the radar mainlobe and sidelobe, the variations in the reflectivity before and after clutter mitigation (ΔZH) and ρhv were used for quantitatively describing the random dispersion caused by mainlobe and sidelobe clutters. The performance of polarimetric algorithms was also reduced by clutter contamination. The deteriorated membership functions in the hydrometeor classification algorithm changed the proportion of classified echoes. The empirical relations of R(ZH, ZDR) and R(KDP) were broken in the quantitative precipitation estimation algorithm and the extra error considerably exceeded the uncertainty caused by the drop-size distribution (DSD) variability of R(ZH). The above results highlighted the negative impact of clutter contamination on polarimetric applications that need to be further investigated.
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Wu, Chong, Liping Liu, Chao Chen, Chian Zhang, Guangxin He, and Juan Li. "Challenges of the Polarimetric Update on Operational Radars in China—Ground Clutter Contamination of Weather Radar Observations." Remote Sensing 13, no. 2 (January 10, 2021): 217. http://dx.doi.org/10.3390/rs13020217.
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China New Generation Doppler Weather Radar (CINRAD) plans to upgrade its hardware and software to achieve polarimetric function. However, the small-magnitude polarimetric measurements were negatively affected by the scattering characteristics of ground clutter and the filter’s response to the ground clutter. This polarimetric contamination was characterized by decreased differential reflectivity (ZDR) and cross-correlation coefficient (ρhv), as well as an increased standard deviation of the differential phase (ΦDP), generating a large-area and long-term observational anomaly for eight polarimetric radars in South China. Considering that outliers simultaneously appeared in the radar mainlobe and sidelobe, the variations in the reflectivity before and after clutter mitigation (ΔZH) and ρhv were used for quantitatively describing the random dispersion caused by mainlobe and sidelobe clutters. The performance of polarimetric algorithms was also reduced by clutter contamination. The deteriorated membership functions in the hydrometeor classification algorithm changed the proportion of classified echoes. The empirical relations of R(ZH, ZDR) and R(KDP) were broken in the quantitative precipitation estimation algorithm and the extra error considerably exceeded the uncertainty caused by the drop-size distribution (DSD) variability of R(ZH). The above results highlighted the negative impact of clutter contamination on polarimetric applications that need to be further investigated.
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Peters, G., and H. J. Kirtzel. "Complementary wind sensing techniques: sodar and RASS." Annales Geophysicae 12, no. 6 (May 31, 1994): 506–17. http://dx.doi.org/10.1007/s00585-994-0506-5.
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Abstract. Radioacoustic sounding (RASS), normally used for temperature profiling, can also be applied for wind measurements. The RASS detects echoes of radar waves, which have been scattered at acoustic waves, and derives the sound velocity from the frequency shift. From the difference of sound velocities measured under different beam directions windprofiles can be determined. Ground clutter does not principally interfere with RASS echoes due to their big frequency shift. Therefore, RASS can supplement radar wind profilers at lower levels where clear-air echoes may be not detectable due to ground clutter. The upper measuring altitude of RASS is limited to a few thousand radar wavelengths by the sound absorption and by the drift of the focal spot of the RASS echo. A further alternative for low-level wind measurements is the Doppler sodar. It is less sensitive to ground clutter than radar, but the measuring height is also limited by sound absorption. It requires no frequency allocation and may therefore be the only choice at some locations. In Germany, Doppler sodars have been operating successfully on a routine basis for more than 10 years at several sites for environmental monitoring purposes.
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Yang, Jian, Xinxin Liu, Bo Yang, Jian Lu, and Guisheng Liao. "Detection and Speed Estimation of Moving Target Based on Phase Compensation and Coherent Accumulation Using Fractional Fourier Transform." Sensors 20, no. 5 (March 4, 2020): 1410. http://dx.doi.org/10.3390/s20051410.
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As unmanned aerial vehicles and other small, low-flying, and low-speed aircrafts are being extensively used, studies on their detection are being extensively conducted in radar application research. However, weak echoes, low Doppler frequencies, and target echoes mixed with ground clutter can considerably degrade the detection performance. Therefore, specific methods for the detection of such targets should be devised. We propose herein a phase compensation and coherent accumulation algorithm based on the fractional Fourier transform (FRFT) for detection and speed estimation of this type of target. First, the energy of the target echo is converged using the FRFT. Next, the phase between the peaks of the target echo is analyzed. Phase compensation and coherent accumulation determined from the expected target speed in the fractional domain eliminate ground clutter and further improve the signal-to-interference-plus-noise ratio. Finally, constant false alarm rate detection is used to identify the target, for which radial speed can be estimated directly according to the peak coordinates. The validity of the algorithm is verified via data simulation and application to real data.
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YING, YINGZI, and LI MA. "VOLUME CLUTTER ELIMINATION, ROUGH INTERFACE REVERBERATION SUPPRESSION, AND TARGET RESONANCE CONVERGENCE IN HETEROGENEOUS MEDIA USING AN ITERATIVE TIME REVERSAL MIRROR." Journal of Computational Acoustics 18, no. 03 (September 2010): 227–43. http://dx.doi.org/10.1142/s0218396x10004140.
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The presence of the clutter of volume scattering and the echo return from rough interface hinders the detection of target in heterogeneous media. This work investigates the application of an iterative time reversal mirror to mitigate the difficulties. Numerical simulations based on pseudospectral finite-difference time-domain method are performed in one and two layered media. A wideband probe pulse is launched to initiate the process, and the time-reversed echo received at the same position is retransmitted as the renewed input signal for next iteration, and repeat the procedures iteratively. The results illustrate as the number of iteration increases, small volume clutter is eliminated, interface reverberation is suppressed relatively, and the echoes will converge to a time-harmonic waveform that corresponds to an object's dominant resonance mode. The detection of target is achieved by extracting this important acoustic signature.
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Yang, Junying, Xiaolan Qiu, Lihua Zhong, Mingyang Shang, and Chibiao Ding. "A Simultaneous Imaging Scheme of Stationary Clutter and Moving Targets for Maritime Scenarios with the First Chinese Dual-Channel Spaceborne SAR Sensor." Remote Sensing 11, no. 19 (September 29, 2019): 2275. http://dx.doi.org/10.3390/rs11192275.
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The technique of azimuth multichannel synthetic aperture radar (SAR) system has become a potential solution to the irreconcilable conflict between high-resolution and wide-swath (HRWS) confronted with in a traditional SAR system. Unambiguous imaging, especially for a scene with moving targets, is one of the crucial research topics in the HRWS SAR system. This paper proposes a simultaneous imaging scheme of moving targets and stationary clutter for maritime scenarios. First, the moving target echoes are extracted from the stationary clutter. After that, two methods working in completely different principles are used to estimate the radial velocity of each moving target, and the estimated result is used for phase compensation. After that, the moving target echoes are added back to the stationary scene echo and sent to the reconstruction filter. Lastly, the reconstructed echo can be processed by the classical Chirp Scaling (CS) algorithm. Experiments are carried out using the Chinese GaoFen-3 dual-channel data. The estimated velocities of the moving targets are verified by automatic identification service (AIS) information, and the imaging results show that the false targets are effectively suppressed and the moving targets also return to their correct positions along the azimuth.
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Yang, Xuguang, Changjun Yu, Aijun Liu, Linwei Wang, and Taifan Quan. "The Vertical Ionosphere Parameters Inversion for High Frequency Surface Wave Radar." International Journal of Antennas and Propagation 2016 (2016): 1–8. http://dx.doi.org/10.1155/2016/8609372.
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High Frequency Surface Wave Radar (HFSWR), which is currently applied in over-the-horizon detection of targets and sea states remote sensing, can receive a huge mass of ionospheric echoes, making it possible for the ionospheric clutter suppression to become a hot spot in research area. In this paper, from another perspective, we take the ionospheric echoes as the signal source rather than clutters, which provides the possibility of extracting information regarding the ionosphere region and explores a new application field for HFSWR. Primarily, pretreatment of threshold segmentation as well as connected region generation is used in the Range-Doppler (R-D) Spectrum to extract the ionospheric echoes. Then, electron density and plasma frequency of field aligned irregularities (FAIs) caused by plasma instabilities in the F region are obtained by the coherent backscattered radar equation. The plasma drift velocity of FAIs can also be estimated from Doppler shift. Ultimately, the effectiveness of inversion is verified by comparing with IRI2012.
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Warnecke, Michaela, Chen Chiu, Jonathan Engelberg, and Cynthia F. Moss. "Active Listening in a Bat Cocktail Party: Adaptive Echolocation and Flight Behaviors of Big Brown Bats, Eptesicus fuscus, Foraging in a Cluttered Acoustic Environment." Brain, Behavior and Evolution 86, no. 1 (2015): 6–16. http://dx.doi.org/10.1159/000437346.
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In their natural environment, big brown bats forage for small insects in open spaces, as well as in vegetation and in the presence of acoustic clutter. While searching and hunting for prey, bats experience sonar interference, not only from densely cluttered environments, but also from calls of conspecifics foraging in close proximity. Previous work has shown that when two bats compete for a single prey item in a relatively open environment, one of the bats may go silent for extended periods of time, which can serve to minimize sonar interference between conspecifics. Additionally, pairs of big brown bats have been shown to adjust frequency characteristics of their vocalizations to avoid acoustic interference in echo processing. In this study, we extended previous work by examining how the presence of conspecifics and environmental clutter influence the bat's echolocation behavior. By recording multichannel audio and video data of bats engaged in insect capture in open and cluttered spaces, we quantified the bats' vocal and flight behaviors. Big brown bats flew individually and in pairs in an open and cluttered room, and the results of this study shed light on the different strategies that this species employs to negotiate a complex and dynamic environment.
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Rennie, S. J., A. J. Illingworth, and S. L. Dance. "On differentiating ground clutter and insect echoes from Doppler weather radars using archived data." Atmospheric Measurement Techniques Discussions 3, no. 2 (April 16, 2010): 1843–60. http://dx.doi.org/10.5194/amtd-3-1843-2010.
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Abstract. Normally wind measurements from Doppler radars rely on the presence of rain. During fine weather, insects become a potential radar target for wind measurement. However, it is difficult to separate ground clutter and insect echoes when spectral or polarimetric methods are not available. Archived reflectivity and velocity data from repeated scans provide alternative methods. The probability of detection (POD) method, which maps areas with a persistent signal as ground clutter, is ineffective when most scans also contain persistent insect echoes. We developed a clutter detection method which maps the standard deviation of velocity (SDV) over a large number of scans, and can differentiate insects and ground clutter close to the radar. Beyond the range of persistent insect echoes, the POD method more thoroughly removes ground clutter. A new, pseudo-probability clutter map was created by combining the POD and SDV maps. The new map optimised ground clutter detection without removing insect echoes.
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Kuriakose, Maju, Jan-Willem Muller, Patrick Stähli, Martin Frenz, and Michael Jaeger. "Receive Beam-Steering and Clutter Reduction for Imaging the Speed-of-Sound Inside the Carotid Artery." Journal of Imaging 4, no. 12 (December 7, 2018): 145. http://dx.doi.org/10.3390/jimaging4120145.
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Handheld imaging of the tissue’s speed-of-sound (SoS) is a promising multimodal addition to diagnostic ultrasonography for the examination of tissue composition. Computed ultrasound tomography in echo mode (CUTE) probes the spatial distribution of SoS, conventionally via scanning the tissue under a varying angle of ultrasound transmission, and quantifying—in a spatially resolved way—phase variations of the beamformed echoes. So far, this technique is not applicable to imaging the lumen of vessels, where blood flow and tissue clutter inhibit phase tracking of the blood echoes. With the goal to enable the assessment of atherosclerotic plaque composition inside the carotid artery, we propose two modifications to CUTE: (a) use receive (Rx) beam-steering as opposed to transmit (Tx) beam-steering to increase acquisition speed and to reduce flow-related phase decorrelation, and (b) conduct pairwise subtraction of data obtained from repetitions of the scan sequence, to highlight blood echoes relative to static echo clutter and thus enable the phase tracking of blood echoes. These modifications were tested in a phantom study, where the echogenicity of the vessel lumen was chosen to be similar to the one of the background medium, which allows a direct comparison of SoS images obtained with the different techniques. Our results demonstrate that the combination of Rx-steering with the subtraction technique results in an SoS image of the same quality as obtained with conventional Tx-steering. Together with the improved acquisition speed, this makes the proposed technique a key step towards successful imaging of the SoS inside the carotid artery.
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Overeem, Aart, Remko Uijlenhoet, and Hidde Leijnse. "Full-Year Evaluation of Nonmeteorological Echo Removal with Dual-Polarization Fuzzy Logic for Two C-Band Radars in a Temperate Climate." Journal of Atmospheric and Oceanic Technology 37, no. 9 (September 1, 2020): 1643–60. http://dx.doi.org/10.1175/jtech-d-19-0149.1.
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AbstractThe Royal Netherlands Meteorological Institute (KNMI) operates two dual-polarization C-band weather radars in simultaneous transmission and reception (STAR; i.e., horizontally and vertically polarized pulses are transmitted simultaneously) mode, providing 2D radar rainfall products. Despite the application of Doppler and speckle filtering, remaining nonmeteorological echoes (especially sea clutter) mainly due to anomalous propagation still pose a problem. This calls for additional filtering algorithms, which can be realized by means of polarimetry. Here we explore the effectiveness of the open-source wradlib fuzzy echo classification and clutter identification based on polarimetric moments. Based on our study, this has recently been extended with the depolarization ratio and clutter phase alignment as new decision variables. Optimal values for weights of the different membership functions and threshold are determined employing a 4-h calibration dataset from one radar. The method is applied to a full year of volumetric data from the two radars in the Dutch temperate climate. The verification focuses on the presence of remaining nonmeteorological echoes by mapping the number of exceedances of radar reflectivity factors for given thresholds. Moreover, accumulated rainfall maps are obtained to detect unrealistically large rainfall depths. The results are compared to those for which no further filtering has been applied. Verification against rain gauge data reveals that only a little precipitation is removed. Because the fuzzy logic algorithm removes many nonmeteorological echoes, the practice to composite data from both radars in logarithmic space to hide these echoes is abandoned and replaced by linearly averaging reflectivities.
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Zhu, Hongxiao, Anupam Kumar Gupta, Xiaowei Wu, Michael Goldsworthy, Ruihao Wang, Mohitha Mikkilineni, and Rolf Müller. "A validation study for a bat-inspired sonar sensing simulator." PLOS ONE 18, no. 1 (January 20, 2023): e0280631. http://dx.doi.org/10.1371/journal.pone.0280631.
Full textAbstract:
Many species of bats rely on echoes to forage and navigate in densely vegetated environments. Foliage echoes in some cases can help bats gather information about the environment, whereas in others may generate clutter that can mask prey echoes during foraging. It is therefore important to study foliage echoes and their role in bat’s sensory ecology. In our prior work, a foliage echo simulator has been developed; simulated echoes has been compared with field recordings using a biomimetic sonar head. In this work, we improve the existing simulator by allowing more flexible experimental setups and enabling a closer match with the experiments. Specifically, we add additional features into the simulator including separate directivity patterns for emitter and receiver, the ability to place emitter and receiver at distinct locations, and multiple options to orient the foliage to mimic natural conditions like strong wind. To study how accurately the simulator can replicate the real echo-generating process, we compare simulated echoes with experimental echoes measured by ensonifying a single leaf across four different species of trees. We further extend the prior work on estimating foliage parameters to estimating a map of the environment.
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Cui, Yan, Yin Sheng Wei, Xiao Guo Song, and Rong Qing Xu. "A Novel Phase Distortion Correction Method Based on Temporal Correlation Matrix." Applied Mechanics and Materials 58-60 (June 2011): 1258–63. http://dx.doi.org/10.4028/www.scientific.net/amm.58-60.1258.
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Since the existence of the ionosphere contamination, results of high-frequency radar has been greatly affected. This paper addresses a new method based on temporal correlation matrix to correct phase distortion for HF sky-wave radars. Strong point echoes, such as target, clutter, transponder and so on, which are highly temporal correlated, can be used to structure temporal correlation matrix. And the matrix contains angles of echoes and phase distortions information. In this paper, we use two-dimension FFT to estimate angle of strong point echo, and then obtain the corrections. Computer simulations are conducted to show the validity of the new method, and some of performances of PGA were compared.
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Berenguer, Marc, Daniel Sempere-Torres, Carles Corral, and Rafael Sánchez-Diezma. "A Fuzzy Logic Technique for Identifying Nonprecipitating Echoes in Radar Scans." Journal of Atmospheric and Oceanic Technology 23, no. 9 (September 1, 2006): 1157–80. http://dx.doi.org/10.1175/jtech1914.1.
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Abstract Because echoes caused by nonmeteorological targets significantly affect radar scans, contaminated bins must be identified and eliminated before precipitation can be quantitatively estimated from radar measurements. Under mean propagation conditions, clutter echoes (mainly caused by targets such as mountains or large buildings) can be found in almost fixed locations. However, in anomalous propagation conditions, new clutter echoes may appear (sometimes over the sea), and they may be difficult to distinguish from precipitation returns. Therefore, an automatic algorithm is needed to identify clutter on radar scans, especially for operational uses of radar information (such as real-time hydrology). In this study, a new algorithm is presented based on fuzzy logic, using volumetric data. It uses some statistics to highlight clutter characteristics (namely, shallow vertical extent, high spatial variability, and low radial velocities) to output a value that quantifies the possibility of each bin being affected by clutter (in order to remove those in which this factor exceeds a certain threshold). The performance of this algorithm was compared against that of simply removing mean clutter echoes. Satisfactory results were obtained from an exhaustive evaluation of this algorithm, especially in those cases in which anomalous propagation played an important role.
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Zhang, Guifu, Yinguang Li, Richard J. Doviak, Dave Priegnitz, John Carter, and Christopher D. Curtis. "Multipatterns of the National Weather Radar Testbed Mitigate Clutter Received via Sidelobes." Journal of Atmospheric and Oceanic Technology 28, no. 3 (March 1, 2011): 401–9. http://dx.doi.org/10.1175/2010jtecha1453.1.
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Abstract The phased-array radar (PAR) of the National Weather Radar Testbed (NWRT) has a unique hybrid (mechanical and electrical) azimuth scan capability, allowing weather observations with different antenna patterns. Observations show the standard deviation of the sample mean power of weather echoes received through the main lobe of a set of squinted beams is less than the clutter received via sidelobes. This then allows use of a multipattern technique to cancel sidelobe echoes from moving scatterers, echoes that cannot be filtered with a ground-clutter canceler. Although the multipattern technique was developed to cancel clutter received through sidelobes, results show clutter from objects moving within the beam can also be canceled.
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Li, Hai, Yutong Chen, Kaihong Feng, and Ming Jin. "Low-Altitude Windshear Wind Speed Estimation Method based on KASPICE-STAP." Sensors 23, no. 1 (December 21, 2022): 54. http://dx.doi.org/10.3390/s23010054.
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Aiming at the problem of low-altitude windshear wind speed estimation for airborne weather radar without independent identically distributed (IID) training samples, this paper proposes a low-altitude windshear wind speed estimation method based on knowledge-aided sparse iterative covariance-based estimation STAP (KASPICE-STAP). Firstly, a clutter dictionary composed of clutter space–time steering vectors is constructed using prior knowledge of the distribution position of ground clutter echo signals in the space–time spectrum. Secondly, the SPICE algorithm is used to obtain the clutter covariance matrix iteratively. Finally, the STAP processor is designed to eliminate the ground clutter echo signal, and the wind speed is estimated after eliminating the ground clutter echo signal. The simulation results show that the proposed method can accurately realize a low-altitude windshear wind speed estimation without IID training samples.
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Siemers, Björn M., Peter Stilz, and Hans-Ulrich Schnitzler. "The acoustic advantage of hunting at low heights above water: behavioural experiments on the European ‘trawling’ bats Myotis capaccinii, M. dasycneme and M. daubentonii." Journal of Experimental Biology 204, no. 22 (November 15, 2001): 3843–54. http://dx.doi.org/10.1242/jeb.204.22.3843.
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SUMMARY We have demonstrated in behavioural experiments that success in capturing prey from surfaces in ‘trawling Myotis’ (Leuconoë-type) depends on the acoustic properties of the surface on which the prey is presented. Two types of surface structure were ensonified with artificial bat signals to probe their acoustic characteristics. We have shown that perception of prey by echolocation is easier if the prey is presented on a smooth surface (such as calm water) than if it is presented on a structured surface (such as vegetation or the ground). This is because the smooth surface reflects a much lower level of clutter echoes than the structured one if ensonified at an angle typical for bats foraging low over water. The ensonification experiments revealed that the sound pressure level of the echo was even higher for mealworms on a smooth surface than for mealworms suspended in air. This might be because waves travelling via the surface also contribute to the echo (e.g. reflection from the surface to the mealworm, back to the surface and then to the receiver). From the behavioural experiments, we conclude that ‘trawling Myotis’ take isolated objects on smooth (water) surfaces for prey. Those objects reflect isolated, stationary acoustic glints back to the echolocating bats. Conversely, ‘trawling Myotis’ will not recognise prey if prey echoes are embedded in numerous clutter echoes. We have demonstrated marked similarities between the three European ‘trawling Myotis’ species M. dasycneme, M. daubentonii and M. capaccinii in echolocation behaviour, search image, foraging strategy and prey perception. We propose that a combination of prey abundance and acoustic advantages could have led to repeated and convergent evolution of ‘trawling’ bats in different parts of the world.
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Patterson, Grant, Ju Wang, Michael Goldsworthy, Salwani Osman, Adam Hinson, and Rolf Müller. "Autonomous localization and mapping based on biomimetic sonar in natural environments." Journal of the Acoustical Society of America 152, no. 4 (October 2022): A69. http://dx.doi.org/10.1121/10.0015574.
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Bats navigating in dense vegetation based on biosonar have to obtain the necessary sensory information from “clutter echoes,” i.e., echoes that are superpositions of contributions of many reflecting facets (e.g., leaves). Since the locations and reflective properties of the individual facets are unknown, clutter echoes have to be treated as random signals that can neither be predicted nor—under most practical circumstance—be replicated. Nevertheless, prior research has shown that deep neural networks are capable of extracting fairly precise location information from clutter echoes. This raises the question whether clutter echoes could be used to provide navigational guidance in a conventional simultaneous localization and mapping (SLAM) framework, which is to a large extent dependent on precise and deterministic measurement to generate a localized map. Our hypothesis is that biomimetic sonar echoes indeed contain the information that is necessary support to local path planning, which can be utilized by a suitable deep learning architecture and training process. To investigate this issue, we have collected data in natural, heavily vegetated environments using a biomimetic sonar head that mimics the periphery of the biosonar system in horseshoe bats. The annotation of the data and the network training process is currently undergoing.
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Geng, Jianrong, Juan He, Hongxia Ye, and Bin Zhan. "A Clutter Suppression Method Based on LSTM Network for Ground Penetrating Radar." Applied Sciences 12, no. 13 (June 25, 2022): 6457. http://dx.doi.org/10.3390/app12136457.
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It is critical to estimate and eliminate the wavelets of ground penetrating radar (GPR), so as to optimally compensate the energy attenuation and phase distortion. This paper presents a new wavelet extraction method based on a two-layer Long Short-Term Memory (LSTM) network. It only uses several random A-scan echoes (i.e., single channel detection echo sequence) to accurately predict the wavelet of any scene. The layered detection scenes with objects buried in different region are set for the 3D Finite-Difference Time-Domain simulator to generate radar echoes as a dataset. Additionally, the simulation echoes of different scenes are used to test the performance of the neural network. Multiple experiments indicate that the trained network can directly predict the wavelets quickly and accurately, although the simulation environment becomes quite different. Moreover, the measured data collected by the Qingdao Radio Research Institute radar and the unmanned aerial vehicle ground penetrating radar are used for test. The predicted wavelets can perfectly offset the original data. Therefore, the presented LSTM network can effectively predict the wavelets and their tailing oscillations for different detection scenes. The LSTM network has obvious advantages compared with other wavelet extraction methods in practical engineering.
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Gui, Renzhou. "Utilizing higher moments to detect time-varying target in radar echo with non-stationary background." International Journal of Microwave and Wireless Technologies 8, no. 2 (February 13, 2015): 215–19. http://dx.doi.org/10.1017/s1759078715000173.
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Detecting time-varying target in non-stationary background is difficult and attractive problem. Time-varying movement exists widely in radar and communication systems. The non-linear processing with higher moments is discussed in the situation. Firstly the signal model of time-varying target with fix acceleration is analyzed. Then the radar echoes from synthetic aperture radar (SAR) are processed with higher moments. It not only restrains Gaussian noise automatically, but also suppresses non-stationary noise. Time-varying targets are different from the non-stationary background clutters. Moreover, the influences of the shadows about time-varying targets are reduced in the algorithm of higher moments. The proposal mentioned above utilizes higher moments to avoid analyzing the complex electromagnetic wave propagation and scatter theory. The differences of detection probability are compared between the chip with time-varying target and the clutter chip. The performances among different number order moments are compared by processing lots of actual SAR data added non-stationary noise. Lastly, the suitable number order moments are suggested by comparing the results from processing the actual radar echoes.
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Wang, Qiang, Bin Xue, Xiaowei Hu, Guangen Wu, and Weihu Zhao. "Robust Space–Time Joint Sparse Processing Method with Airborne Active Array for Severely Inhomogeneous Clutter Suppression." Remote Sensing 14, no. 11 (June 1, 2022): 2647. http://dx.doi.org/10.3390/rs14112647.
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Due to clutter inhomogeneity, the clutter suppression ability of space–time adaptive processing (STAP) is usually constrained by the insufficient number of independent and identically distributed (IID) clutter training samples and, as a result, is sacrificed to achieve the demanded sample reduction. Moreover, since clutter heterogeneity is exacerbated in the real environment, the IID training sample size can be heavily reduced, leading to the deterioration in clutter suppression. To solve this problem, a novel robust space–time joint sparse processing method with airborne active array is proposed. This method has several outstanding advantages: (1) only the single snapshot cell under test (CUT) data is used for the superior clutter suppression performance; and (2) the proposed method completely removes the dependence of the system processing ability on IID training samples. In this paper, the signal model of uniform transmitting subarray diversity is first established to obtain the single snapshot echo observed CUT data. Then, with the matched reconstruction, the single snapshot data are equivalently converted into multi-frame echo data. Finally, a fast multi-frame echo data joint sparse Bayesian algorithm is used to achieve heterogeneous clutter suppression. Numerous experiments were performed to verify the advantages of the proposed method.
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Kim, Yong Hyun, Sungshin Kim, Hye-Young Han, Bok-Haeng Heo, and Cheol-Hwan You. "Real-Time Detection and Filtering of Chaff Clutter from Single-Polarization Doppler Radar Data." Journal of Atmospheric and Oceanic Technology 30, no. 5 (May 1, 2013): 873–95. http://dx.doi.org/10.1175/jtech-d-12-00158.1.
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Abstract In countries with frequent aerial military exercises, chaff particles that are routinely spread by military aircraft represent significant noise sources for ground-based weather radar observation. In this study, a cost-effective procedure is proposed for identifying and removing chaff echoes from single-polarization Doppler radar readings in order to enhance the reliability of observed meteorological data. The proposed quality control procedure is based on three steps: 1) spatial and temporal clustering of decomposed radar image elements, 2) extraction of the clusters’ static and time-evolution characteristics, and 3) real-time identification and removal (or censoring) of target echoes from radar data. Simulation experiments based on this procedure were conducted on site-specific ground-echo-removed weather radar data provided by the Korea Meteorological Administration (KMA), from which three-dimensional (3D) reflectivity echoes covering hundreds of thousands of square kilometers of South Korean territory within an altitude range of 0.25–10 km were retrieved. The algorithm identified and removed chaff clutter from the South Korean data with a novel decision support system at an 81% accuracy level under typical cases in which chaff and weather clusters were isolated from one another with no overlapping areas.
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Yan, Shi, Xin Zi Yuan, Nai Zhi Zhao, Wei Wang, and Yang Cheng. "Finite Element Analysis of Corrosion Damaged Pipeline Using PZT-Based Ultrasonic Guided Wave Energy Method." Advanced Materials Research 1079-1080 (December 2014): 368–73. http://dx.doi.org/10.4028/www.scientific.net/amr.1079-1080.368.
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PZT-based ultrasonic guided wave has played an important role in health monitoring of pipeline structures. By using the PZT-based ultrasonic guided wave energy method and finite element software ABAQUS, the numerical simulation is performed to analyze various corrosion damaged pipeline structures, emphasizing on the damage identification, sensitivity analysis and longitudinal energy attenuation of the guided wave along various corrosion damaged pipelines. The preliminary analysis of the echo signals shows that the grass-like clutter wave belongs to echoes of the corrosion damage of the pipeline, and the wave energy spreads faster here. At the same time, by frequency spectrum analysis of the echo signal, the relationship between the reflection coefficient and the radial depth of defection is made which can be used to approximately evaluate geometrical dimension of the damage.
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Wang, Tao, Ling Zhang, and Gangsheng Li. "Shipborne HFSWR Target Detection in Clutter Regions Based on Multi-Frame TFI Correlation." Remote Sensing 14, no. 17 (August 25, 2022): 4192. http://dx.doi.org/10.3390/rs14174192.
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High-frequency surface wave radar (HFSWR) is an important marine monitoring technology, and this new regime of radar plays an important role in large-scale, continuous early-warning monitoring at sea. In particular, shipborne HFSWR has wider applications in detecting interesting sea areas, with the advantages of flexible deployment and extended detection capability. Due to the large amount of sea clutter accompanying the echo signals of shipborne HFSWR and the spread of sea clutter due to platform motion, the detection of targets in clutter regions is extremely difficult. In this paper, a multi-frame time-frequency (TF) analysis–based target-detection method is proposed. First, the sea clutter spreading area in the HFSWR echo signal is modeled, and the effects of platform motion and currents on the sea clutter spread are analyzed to determine the sea clutter coverage area; this paper focuses on frequency modeling. Then the TF image (TFI) of each range cell is obtained by TF analysis of the cells within a certain range of the echo signal, and the range cells of possible target points are determined by binary classification of the TFI through a convolutional neural network. Finally, the location of the final target point is obtained by correlation of multi-frame TFIs. Shipborne HFSWR field experiments show that the proposed detection method performs well in detecting targets concealed by sea clutter.
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Lakshmanan, Valliappa, Jian Zhang, and Kenneth Howard. "A Technique to Censor Biological Echoes in Radar Reflectivity Data." Journal of Applied Meteorology and Climatology 49, no. 3 (March 1, 2010): 453–62. http://dx.doi.org/10.1175/2009jamc2255.1.
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Abstract Existing techniques of quality control of radar reflectivity data rely on local texture and vertical profiles to discriminate between precipitating echoes and nonprecipitating echoes. Nonprecipitating echoes may be due to artifacts such as anomalous propagation, ground clutter, electronic interference, sun strobe, and biological contaminants (i.e., birds, bats, and insects). The local texture of reflectivity fields suffices to remove most artifacts, except for biological echoes. Biological echoes, also called “bloom” echoes because of their circular shape and expanding size during the nighttime, have proven difficult to remove, especially in peak migration seasons of various biological species, because they can have local and vertical characteristics that are similar to those of stratiform rain or snow. In this paper, a technique is described that identifies candidate bloom echoes based on the range variance of reflectivity in areas of bloom and uses the global, rather than local, characteristic of the echo to discriminate between bloom and rain. Every range gate is assigned a probability that it corresponds to bloom using morphological (shape based) operations, and a neural network is trained using this probability as one of the input features. It is demonstrated that this technique is capable of identifying and removing echoes due to biological targets and other types of artifacts while retaining echoes that correspond to precipitation.
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Powell, Scott W., Robert A. Houze,, and Stella R. Brodzik. "Rainfall-Type Categorization of Radar Echoes Using Polar Coordinate Reflectivity Data." Journal of Atmospheric and Oceanic Technology 33, no. 3 (March 2016): 523–38. http://dx.doi.org/10.1175/jtech-d-15-0135.1.
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AbstractAn algorithm used to classify precipitation echoes by rain type without interpolating radar data to a constant height is detailed. The method uses reflectivity data without clutter along the lowest available scan angle so that the classifications yield a more accurate representation of the rain type observed at the surface. The algorithm is based on that of Steiner et al. but is executed within a polar coordinate system. An additional procedure allows for more small, isolated, and/or weak echo objects to be appropriately identified as convective. Echoes in the immediate vicinity of convective cores are included in a new transition category, which consists mostly of echoes for which a convective or stratiform determination cannot be confidently made. The new algorithm more effectively identifies shallow convection embedded within large stratiform regions, correctly identifies isolated shallow and weak convection as such, and more often appropriately identifies periods during which no stratiform precipitation is present.
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Liu, Zhutian, Zhongyu Li, Huaiqin Yu, Junjie Wu, Yulin Huang, and Jianyu Yang. "Bistatic Forward-Looking SAR Moving Target Detection Method Based on Joint Clutter Cancellation in Echo-Image Domain with Three Receiving Channels." Sensors 18, no. 11 (November 8, 2018): 3835. http://dx.doi.org/10.3390/s18113835.
Full textAbstract:
In bistatic forward-looking synthetic aperture radar (BFSAR) ground moving target detection (GMTD), the suppression of the strong and heterogeneous ground clutter is one of the most crucial and challenging issues. Due to the bistatic forward-looking mode and long observation time, Doppler ambiguity, range and Doppler cells migration and non-stationary characteristics will exist in clutter receives, which leads to severe performance degradation of the traditional method. Hence, this paper proposes a GMTD method based on joint clutter cancellation in echo-image domain for BFSAR to achieve effective GMTD in heterogeneous BFSAR clutter. First, the pre-filtering and keystone transform are applied to suppress Doppler ambiguity and correct range cell migration, respectively. Then, time-division space-time adaptive clutter cancellation is adopted to suppress clutter at the first time in the echo domain, which can eliminate the effect of the migration of Doppler cells. However, its performance will be severely degraded due to the strong non-stationary characteristic of BFSAR clutter. Finally, adaptive displaced phase center antenna is exploited to suppress the residual non-stationary BFSAR clutter in image domain. Experimental results have shown that the strong non-stationary clutter of BFSAR has been sufficiently suppressed by the proposed method and the SCNR provided is enough to detect a moving target well.
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Zrnić, Dusan S., Valery M. Melnikov, and Alexander V. Ryzhkov. "Correlation Coefficients between Horizontally and Vertically Polarized Returns from Ground Clutter." Journal of Atmospheric and Oceanic Technology 23, no. 3 (March 1, 2006): 381–94. http://dx.doi.org/10.1175/jtech1856.1.
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Abstract Characteristics of the magnitude and phase of correlation coefficients between horizontally and vertically polarized returns from ground clutter echoes are quantified by analyzing histograms obtained with an 11-cm wavelength weather surveillance radar in Norman, Oklahoma. The radar receives simultaneously horizontal and vertical (SHV) electric fields and can transmit either horizontal fields or both vertical and horizontal fields. The differences between correlations obtained in this SHV mode and correlations measured in alternate H, V mode are reviewed; a histogram of differential phase obtained in Florida using alternate H, V mode is also presented. Data indicate that the backscatter differential phase of clutter has a broad histogram that completely overlaps the narrow histogram of precipitation echoes. This is important as it implies that a potent discriminator for separating clutter from meteorological echoes is the texture of the differential phase. Values of the copolar cross-correlation coefficient from clutter overlap completely those from precipitation, and effective discrimination is possible only if averages in range are taken. It is demonstrated that the total differential phase (system and backscatter) depends on the polarimetric measurement technique and the type of scatterers. In special circumstances, such as calibrating or monitoring the radar, clutter signal can be beneficial. Specifically, system differential phase can be estimated from histograms of ground clutter, receiver differential phase can be estimated from precipitation returns, and from these two, the differential phase of transmitted waves is easily computed.
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Siemers, Björn M., Grit Schauermann, Hendrik Turni, and Sophie von Merten. "Why do shrews twitter? Communication or simple echo-based orientation." Biology Letters 5, no. 5 (June 17, 2009): 593–96. http://dx.doi.org/10.1098/rsbl.2009.0378.
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Shrews are very vocal animals. We tested behaviourally whether the high-pitched laryngeal ‘twittering’ calls of as-yet unclear function serve for communication or echo-based orientation. We used a representative species from each of the two largest phylogenetic groups of shrews. In both species, experimental manipulation of substrate density, but not of the likelihood of conspecific presence, affected the shrews' call rate when exploring an unknown environment. This adaptation of call rate to the degree of habitat clutter parallels bat echolocation and suggests that shrews may use the echoes and reverberations of their calls for identifying routes through their habitat or for probing habitat type. To assess the acoustic feasibility of shrew echo orientation, we ensonified shrew habitats in the field with an ‘artificial shrew’ (small speaker mounted close to a sensitive microphone). The data showed that shrew-like calls can indeed yield echo scenes useful for habitat assessment at close range, but beyond the range of the shrews' vibrissae.
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Silberstein, David S., David B. Wolff, David A. Marks, David Atlas, and Jason L. Pippitt. "Ground Clutter as a Monitor of Radar Stability at Kwajalein, RMI." Journal of Atmospheric and Oceanic Technology 25, no. 11 (November 1, 2008): 2037–45. http://dx.doi.org/10.1175/2008jtecha1063.1.
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Abstract There are many applications in which the absolute and day-to-day calibrations of radar sensitivity are necessary. This is particularly so in the case of quantitative radar measurements of precipitation. While fine calibrations may be made periodically by a variety of techniques such as the use of antenna ranges, standard targets, and solar radiation, knowledge of variations that occur between such checks is required to maintain the accuracy of the data. This paper presents a method for this purpose using the radar on Kwajalein Atoll to provide a baseline calibration for the control of measurements of rainfall made by the Tropical Rainfall Measuring Mission (TRMM). The method uses echoes from a multiplicity of ground targets. The daily average clutter echoes at the lowest elevation scan have been found to be remarkably stable from hour to hour, day to day, and month to month within better than ±1 dB. They vary significantly only after either deliberate system modifications, equipment failure, or other unknown causes. A cumulative distribution function (CDF) of combined precipitation and clutter reflectivity (Ze in dBZ) is obtained on a daily basis, regardless of whether or not rain occurs over the clutter areas. The technique performs successfully if the average daily area mean precipitation echoes (over the area of the clutter echoes) do not exceed 45 dBZ, a condition that is satisfied in most locales. In comparison, reflectivities associated with the most intense clutter echoes can approach 70 dBZ. Thus, the level at which the CDF reaches 95% is affected only by the clutter and reflects variations only in the radar sensitivity. Daily calculations of the CDFs have recently been made beginning with August 1999 data and are used to correct 7.5 yr of measurements, thus enhancing the integrity of the global record of precipitation observed by TRMM. The method is robust and may be applicable to other ground-based radars.
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Zhang, Guangwei, Ping Li, Guolin Li, and Ruili Jia. "Distribution Characteristics of Ground Echo Amplitude and Recognition of Signal Grazing Angle." Sensors 21, no. 24 (December 12, 2021): 8315. http://dx.doi.org/10.3390/s21248315.
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With the continuous advancement of electronic technology, terahertz technology has gradually been applied on radar. Since short wavelength causes severe ground clutter, this paper studies the amplitude distribution statistical characteristics of the terahertz radar clutter based on the measured data, and provides technical support for the radar clutter suppression. Clutter distribution is the function of the radar glancing angle. In order to achieve targeted suppression, in this paper, selected axial integral bispectrum (selected AIB) feature is selected as deep belief network (DBN)input to complete the radar glancing angle recognition and the network structure, network training method, robustness are analyzed also. The ground clutter amplitude distribution can follow normal distribution at 0~45° grazing angles. The Weibull distribution and G0 distribution can describe the amplitude probability density function of ground clutter at grazing angles 85° and 65°. The recognition rate of different signal grazing angles can reach 91% on three different terrains. At the same time, the wide applicability of the selected AIB feature is verified. The analysis results of ground clutter amplitude characteristics play an important role in the suppression of radar ground clutter.
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Liu, Yun Feng, Ji Dong Suo, Xiao Ming Liu, and Bo Li. "Adaptive Radar Sensitivity Time Control Based on Linear Prediction Sea Clutter." Applied Mechanics and Materials 701-702 (December 2014): 279–82. http://dx.doi.org/10.4028/www.scientific.net/amm.701-702.279.
Full textAbstract:
Sea clutter is interference background in radar target processing. It is difficult to detect long-range weak target in sea clutter. Sea clutter signal changes complex, with high intensity. For close signal, radar receiver will overload and reach saturation point. We are interested in the most dynamic range for displaying target echo and fast changing component of clutter. By analyzing spatial and temporal correlation of sea clutter, slow changing component can be minus from sea clutter. The innovation of this paper is to propose a linear prediction error method for sea clutter to increase dynamic range of radar receiver. It prevents overloading and reaching saturation point at close range.
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Luo, Feng, Yao Feng, Guisheng Liao, and Linrang Zhang. "The Dynamic Sea Clutter Simulation of Shore-Based Radar Based on Stokes Waves." Remote Sensing 14, no. 16 (August 12, 2022): 3915. http://dx.doi.org/10.3390/rs14163915.
Full textAbstract:
The sea clutter model based on the physical sea surface can simulate radar echo at different times and positions and is more suitable for describing dynamic sea clutter than the traditional models based on statistical significance. However, when applying the physical surface model to shore-based radar, the effects of wave nonlinearity, breaking wave, shadow, and radar footprint size must be considered. In this paper, a dynamic sea clutter simulation scheme based on a nonlinear wave is proposed that uses random Stokes waves instead of linear superposition waves to simulate the nonlinear dynamic sea surface and then calculates echo in the form of scattering cells. In this process, the relationship between wind speed and the nonlinear factor of the Stokes wave is derived, a simple model of shadow modulation is provided, and a method for appending the sea clutter spikes formed by breaking waves is developed. The experimental results show that the simulated sea clutter and the real measured clutter have good consistency in intensity, amplitude statistical distribution, Doppler spectrum, and spatiotemporal correlation. The proposed scheme is suitable for the sea clutter simulation of shore-based radar and can also adjust the relevant parameters to extend to other types of sea clutter simulation.
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Unal, Christine. "Spectral Polarimetric Radar Clutter Suppression to Enhance Atmospheric Echoes." Journal of Atmospheric and Oceanic Technology 26, no. 9 (September 1, 2009): 1781–97. http://dx.doi.org/10.1175/2009jtecha1170.1.
Full textAbstract:
Abstract The clutter present in the Doppler spectra of atmospheric targets can be removed by using polarimetry. The purpose is to suppress the Doppler velocity bins where spectral polarimetric parameters have atypical values. This procedure largely improves profiles of moments and polarimetric parameters of atmospheric targets. Several spectral polarimetric clutter-reduction techniques, which are based on thresholding and intended for real-time processing, are discussed in this paper. A new method, the double spectral linear depolarization ratio clutter-suppression technique, is proposed. Very satisfactory performances are obtained with this method, which can be used in the full range of elevations (0°–90°). Spectral polarimetric clutter-suppression techniques for real-time processing were studied for the S-band high-resolution Transportable Atmospheric Radar (TARA) profiler. For this study, precipitation, cloud, and clear-air scattering are considered examples of atmospheric echoes. After successful testing in 2008, the double spectral linear depolarization ratio filter was implemented in the real-time processing of the X-band scanning drizzle radar (IDRA).
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Li, Yinguang, Guifu Zhang, Richard Doviak, and Darcy Saxion. "Scan-to-Scan Correlation of Weather Radar Signals to Identify Ground Clutter." Geoscience and Remote Sensing Letters, IEEE 10, no. 4 (February 2013): 855–59. http://dx.doi.org/10.1109/lgrs.2012.2226233.
Full textAbstract:
The scan-to-scan correlation method to discriminate weather signals from ground clutter, described in this letter, takes advantage of the fact that the correlation time of radar echoes from hydrometeors is typically much shorter than that from ground objects. In this letter, the scan-to-scan correlation method is applied to data from the WSR-88D, and its results are compared with those produced by the WSR-88D's ground clutter detector. A subjective comparison with an operational clutter detection algorithm used on the network of weather radars shows that the scan-to-scan correlation method produces a similar clutter field but presents clutter locations with higher spatial resolution.
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Hu, Ju Rong, Long Chen, and Jing Zhou. "Multifunction Simulator for Radar Test." Applied Mechanics and Materials 278-280 (January 2013): 893–96. http://dx.doi.org/10.4028/www.scientific.net/amm.278-280.893.
Full textAbstract:
Abstract. This paper describes the design of a general purpose multifunction simulator which is used to test radar and its components. The simulator is a hardware system controlled by computer software which generates echoes of targets, clutter and jamming for radar electromagnetic environment scenario simulation. It will responds to the subject radar’s antenna scan by producing composite echoes in real time. Computer programs are used to management the simulation process and allow various combinations of electromagnetic environment. Parallel signal generator is exploited to increase the execution speed and achieve real-time performance. Since the simulator can produce video frequency and intermediate frequency echo separately it can be used for the test of most components of radar. The capability to accommodate dynamic scenarios of long duration in real time for detailed tracking studies distinguishes the simulator from other pulse-by-pulse simulators that have been previously reported.
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Zhu, Huijie, Lijun Wang, and Mingqian Liu. "Using DTMB-Based Passive Radar for Small Unmanned Aerial Vehicle Detection." Wireless Communications and Mobile Computing 2021 (May 6, 2021): 1–10. http://dx.doi.org/10.1155/2021/9987992.
Full textAbstract:
There is inevitable polarization angle deviation between the target echo signal and the direct path signal of illuminator of opportunity (IO) in passive radar. In order to investigate the potential performance loss in target detection induced by the random deviation, small unmanned aerial vehicle (UAV) detection experiments with digital television terrestrial multimedia broadcasting- (DTMB-) based passive radar are conducted in this paper. Experimental results show that the polarization angles of the clutter signal and target echo signal are inconsistent. When the polarization diversity technology is used to suppress the clutter signal, the processing performance of the target echo signal may be reduced. On the premise that clutter is effectively suppressed by the processing algorithm, polarization synthesis can maximize the target echo signal processing gain. The effectiveness of the target localization algorithm combining time difference of arrival (TDOA) and direction of arrival (DOA) is also verified with polarization diversity reception in this paper.
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Nguyen, Cuong M., Dmitri N. Moisseev, and V. Chandrasekar. "A Parametric Time Domain Method for Spectral Moment Estimation and Clutter Mitigation for Weather Radars." Journal of Atmospheric and Oceanic Technology 25, no. 1 (January 1, 2008): 83–92. http://dx.doi.org/10.1175/2007jtecha927.1.
Full textAbstract:
Abstract A parametric time domain method (PTDM) for clutter mitigation and precipitation spectral moments’ estimation for weather radars is introduced. Use of PTDM allows for the simultaneous estimation of clutter and precipitation echo spectral moments. It is shown that this approach leads to accurate estimates of precipitation spectral moments in the presence of clutter. Based on simulations, the PTDM performance is evaluated and compared against the clutter spectral filtering technique. In this study special attention is paid to the cases of strong clutter contamination. Furthermore, both methods, the PTDM and spectral clutter filter, are illustrated using the Colorado State University–University of Chicago–Illinois State Water Survey (CSU–CHILL) observations.