Performance Of Radar System Research Articles

Signal fusion research in passive radar based on polarization diversity technology

AbstractPolarization diversity technology is an effective method to improve the detection performance of passive radar systems, but the related papers mainly conduct research on the polarization diversity in interference suppression, and there are few studies focusing on the polarization characteristics of the target itself. The work in this paper is divided into two parts. The first part is going to investigate the potential benefits of signal fusion in target polarization-scattering characteristic. The analysis results show that the cross-polarized component of the target scattered echo is not always weaker than the co-polarized component, and the polarization amplitude ratio value is mostly concentrated near 1. This indicates that polarization signal fusion will likely improve target detection performance. The other part introduces a polarization signal fusion method based on the non-coherent integration (P-NCI), but this method is susceptible to the influence of the difference in the signal-to-noise ratio (SNR) of the signal of each polarization channel, resulting in a reduction in the SNR of the fusion signal. The polarization signal fusion method based on adaptive weighting (AW-PSF) can effectively improve the robustness of signal fusion. The experimental results show that AW-PSF has better detection performance compared with single-polarization channel and P-NCI.

Spectrum Sharing Between Radar and Communication Systems Based on Overlapped Virtual Subarrays

In this paper, we propose a new technique for spectrum sharing between radar and communication systems. The new technique enjoys the advantages of null-space projecting which can be used to mitigate the interference between radar and communication systems. In order to reduce the number of radar antennas and reduce the requirement of manufacture, deploy and implementation, we also introduce virtual subarray architecture to reap more effective transmit array aperture. The essence is to partition the multiple-input multiple-output (MIMO) antenna array into multiple overlapped subarrays to reap a compromise between coherent gain and diversity gain. We show that the configuration with overlapped subarrays can be used to form narrower beams with lower sidelobes, which is good for reaping higher performance in target detection. In order to evaluate the impact on the performance of radar systems with the implementation of spectrum sharing, the generalized likelihood ratio test for target detection is derived. It is shown that, although the implementation of the proposed spectrum sharing method would loss the radar system’s target detection performance, we can reap the benefits of spectrum sharing. That is to say, we achieve a good tradeoff between spectrum sharing and target detecting.

A New Method Based on Copula Theory for Evaluating Detection Performance of Distributed-Processing Multistatic Radar System

A New Method Based on Copula Theory for Evaluating Detection Performance of Distributed-Processing Multistatic Radar System

A Multifeature TDAO-AIR Clutter Classification Approach for Inshore Ambiguity Identification and Suppression With Azimuth Multichannel SAR System

In the inshore region, the azimuth ambiguity of land clutter is the main factor, which reduces the clutter suppression performance for the multichannel synthetic aperture radar (SAR) system. To address this problem, we propose a multifeature tensor discriminant alternating optimization and affine invariant Riemannian (TDAO-AIR) classification approach. First, the correlation coefficient between channels is obtained to characterize the normalized SAR image amplitude. Next, multilook interferometric processing is performed to reduce the effect of Speckle noise and acquire multilook interferometric complex images. At the same time, we extract the correlation coefficient gradient and the multilook interferometric phase gradient in different spatial directions to characterize the spatial structure. Next, we construct a feature tensor (FT), including correlation coefficient between channels, multilook interferometric phase, and spatial structural gradient information for each range-Doppler unit (RDU). The TDAO algorithm is proposed to extract the core FT (CFT) by optimizing the objective function and getting the projection matrix. Then, the CFT is unfolded along the feature dimension, and the feature covariance matrix (FCM) is constructed for each RDU. With the AIR distance measure, the inshore region is divided into different clutter regions. Finally, in the azimuth ambiguous clutter region, independent and identically distributed (IID) training samples are selected to estimate the clutter covariance matrix (CCM), and robust adaptive clutter suppression is performed in the SAR image domain. The experiments on simulated and real measured data by TerraSAR-X demonstrate that the proposed method can accurately identify and suppress the azimuth ambiguity in the inshore region.

Modeling Buried Object Brightness and Visibility for Ground Penetrating Radar

Comparing the observed brightness of various buried objects is a straightforward way to characterize the performance of a ground penetrating radar (GPR) system. However, a limitation arises. A simple comparison of buried object brightness values does not disentangle the effects of the GPR system itself from the system's operating environment and the objects being observed. Therefore, with brightness values exhibiting an unknown synthesis of systemic, environmental, and object factors, GPR system analysis becomes a convoluted affair. In this work, we use an experimentally collected dataset of over 25,000 object observations from five different multi-static radar arrays to develop models of buried object brightness and control for these various effects. Our modeling efforts provide a means for quantifying the relative brightness of GPR systems, the objects they detect, and the physical properties of those objects which influence observed brightness. To evaluate the models' performance on new object observations, we repeatedly simulate fitting them to half the dataset and predicting the observed brightness values of the unseen half. Additionally, we introduce a method for estimating the probability that individual observations constitute a visible object, which aids in failure analysis, performance characterization, and dataset cleaning.

Joint Transmitting Subarray Partition and Beamforming for Active Jamming Suppression in Phased‐MIMO Radar

AbstractAs the tradeoff between conventional phased‐array and multiple‐input multiple‐output (MIMO) radars, phased‐MIMO radar has been studied in recent years, which can simultaneously obtain coherent processing gain and waveform diversity gain. In this paper, in order to effectively suppress the jamming signal and improve the target detection performance of radar system, a joint transmitting subarray partition and beamforming method in phased‐MIMO radar is proposed. To be specific, at the transmitter, the transmitting array of radar system is partitioned into a certain number of non‐overlapped subarrays, and the subarray structure of transmitting array and the corresponding beamformer weight vectors are simultaneously optimized by constructing the optimization model of maximizing the signal‐to‐noise ratio of the whole received echoes under certain constraint conditions, so as to effectively maximize the power utilization of radar transmitter, reduce the peak sidelobe level of transmit beampattern and improve the radar anti‐jamming performance. Moreover, the adaptive beamforming technique is applied to suppress the jamming signal entering the receiver, so that the transmitting and receiving adaptive degrees of freedom are jointly utilized to enhance the anti‐jamming capability of radar system. Simulation results demonstrate the validity of the proposed method.

Radar main‐lobe jamming suppression and identification based on robust whitening Blind Source Separation and Convolutional Neural Networks

The main-lobe jamming causes serious degradation of radar system performance in practical applications. In recent years, the Blind Source Separation (BSS) method has been applied to suppress the main-lobe jamming. However, the received echoes of target and jamming cannot be effectively identified while the robustness of the conventional BSS method is poor due to the influence of system noise. To tackle these problems, a radar main-lobe jamming suppression and identification method is proposed based on robust whitening BSS and Convolutional Neural Networks methods. First, the target echoes and jamming are separated by the proposed robust whitening BSS method. An iterative optimisation method is proposed to obtain the robust whitening matrix, and sufficient conditions are provided for solvability. Then, a Target echo and Jamming Identification Network (TJINet) is proposed to identify the signals after the robust whitening BSS. The proposed TJINet method uses residual blocks and branch structures to improve classification performance and utilises asymmetric convolution blocks to extract subtle features between the target echo and deceptive jamming. Simulation and experimental results show that the proposed method has better jamming suppression performance than the traditional methods under low signal-to-noise ratio (SNR) conditions, the algorithm converges faster, and also can stably identify the target echo and jamming signals.

Detection Performance Analysis of the Standard FDA and FDA-MIMO Radar in the Gaussian Background

This paper studies the optimal detection performance of the standard frequency diverse array (FDA) radar and FDA multi-input multioutput (FDA-MIMO) radar in Gaussian clutter and noise. Array signal processing scheme at the receiver is firstly designed to obtain the array steering vector containing range, azimuth, and frequency increment. For the two array configurations, namely, collocated transmit-receive and collocated transmit distributed receive, the likelihood ratio test statistics and the test statistic distributions are derived in the Neyman–Pearson sense. It is then investigated how the number of array elements influences the detection performance of various radar systems at low signal-to-noise ratio (SNR). Several numerical simulations are carried out to demonstrate that the performance improvement is hard for MIMO and FDA-MIMO by only increasing the number of transmit elements, while it is achievable for the FDA. The paper finally makes a comparative analysis for detection performances of five radar configurations under different SNRs.

Comparison of Atmospheric Refractivity Estimation Methods and Their Influence on Radar Propagation Predictions

AbstractEnvironmental predictions in the marine atmospheric surface layer (MASL) are imperative to optimize X‐band radar system performance in marine environments. Evaporation ducts (ED) lead to anomalous propagation where characterization of EDs in the MASL occurs primarily through two methods: in‐situ measurements and numerical modeling. This study investigates the differences in co‐located and synchronous refractivity estimations from the CASPER‐East campaign. Propagation predictions are generated for refractive profiles from in‐situ measurements, Monin‐Obukov boundary layer similarity theory, and numerical weather prediction forecasts. Variations in evaporation duct height (EDH) are found to be a primary driver of differences in propagation between the estimated refractivity profiles, where location of the EDH relative to the transmitter changes the sensitivity of propagation predictions to EDH estimates. Differences in propagation are large when EDH estimates span the transmitter height and the lowest EDH across the methods is small, regardless of how much variation there is in EDH estimates. When the lowest EDH is small and EDH estimates span the transmitter height there are differences in physical regimes causing large propagation discrepancies–for example, leakage into versus trapping within the duct. Variation in EDH between the methods is greatest in stable environments. M‐deficit and curvature of the refractive profiles also influence propagation specifically in scenarios when EDH spans the transmitter. When all EDHs are below the transmitter, EDH variance is the primary contributor to propagation variance, but M‐deficit and profile curvature variance play a secondary role. M‐deficits and curvature between the methods agree most often during periods of atmospheric stability.

Design of TR module aging control system based on adaptive filtering algorithm

As an important part of active phased array radar, the working stability of TR module has a direct impact on the detection performance of radar system. This paper designs a set of TR electrical aging test system, for batch component aging test at the same time. Based on the principle of spontaneous heating under full power operation, the test environment was designed. The design of wave control board circuit met the excitation requirements in the work of the components. Meanwhile, the adaptive filtering algorithm and classical control theory were combined to control the TR working temperature, which realized the requirements of stable aging test of batch TR module. This system can accurately monitor whether the TR component products fail in the process of electrical aging, and at the same time can more accurately control the working temperature of the tested products within the required temperature range. It also provides a technical basis for further analysis and improvement of TR component product performance parameters. This design method can also be applied to the aging screening of other electronic board cards or components with high reliability requirements.

Noise Radar Technology: Waveforms Design and Field Trials.

Performance of continuous emission noise radar systems are affected by the sidelobes of the output of the matched filter, with significant effects on detection and dynamic range. Hence, the sidelobe level has to be controlled by a careful design of the transmitted waveform and of the transmit/receive parts of the radar. In this context, the average transmitted power has to be optimized by choosing waveforms with a peak-to-average power ratio as close to the unity as possible. However, after coherent demodulation and acquisition of the received signal and of the reference signal at the transmitting antenna port, the goodness (low sidelobes) of the output from the matched filter can be considerably reduced by the deleterious effects due to the radar hardware, including the analog-to-digital converter (ADC). This paper aims to solve the above problems from both the theoretical and the practical viewpoint and recommends the use of tailored waveforms for mitigating the dynamic range issues. The new findings are corroborated by the results from two noise radar demonstrators operating in Germany (rural environment) and in Turkey (coast and sea environment) and the related lessons learnt.

Analytical Model and Real-Time Calculation of Target Echo Signals on Wideband LFM Radar

In wideband radar system testing and performance evaluation, target echo simulation should simultaneously meet real-time and high-precision requirements. In this paper, we focus on the wideband linear frequency modulated (LFM) radar signal, derive the echo signal time-domain analytical expression based on the multiscattering center model and propose a high-precision real-time echo simulation calculation method. Regarding the low model reliability and poor versatility problems in the current wideband radar target calculation, the analytical model proposed here truly reflects the inner-pulse modulation characteristics of the radar transmit signal and the wideband electromagnetic scattering characteristics of the target. Current wideband radar target signal calculation accuracy and real-time performance are also difficult to balance. Considering this problem, the wideband radar target echo analytical model proposed in this paper avoids the large amount of calculations required for the full numerical calculation and effectively improves the calculation accuracy and real-time performance of wideband radar target echo signal calculations without reducing calculation accuracy. The real-time calculation method involves elaborate amplitude-phase control. Simulation analysis and experimental verification confirmed the reliability and validity of these results. These research results have important theoretical significance and practical application value in the field of hardware-in-the-loop simulation.

Wind Direction Data from a Coastal HF Radar System in the Gulf of Naples (Central Mediterranean Sea)

Results on the accuracy of SeaSonde High Frequency (HF) radar wind direction measurements in the Gulf of Naples (Southern Tyrrhenian Sea, Central Mediterranean Sea) are here presented. The investigation was carried out for a winter period (2 February–6 March) and for one summer month (August) of the reference year 2009. HF radar measurements were compared with in situ recordings from a weather station and with model data, with the aim of resolving both small scale and large scale dynamics. The analysis of the overall performance of the HF radar system in the Gulf of Naples shows that the data are reliable when the wind speed exceeds a 5 m/s threshold. Despite such a limitation, this study confirms the potentialities of these systems as monitoring platforms in coastal areas and suggests further efforts towards their improvement.

Measurements Accuracy Evaluation for ATSC Signal-Based Passive Radar Systems

The detection and tracking performance of passive radar systems can be enhanced by exploiting multiple emitters and one receiver site by allowing for multiple bistatic geometries. This article investigates the measurement accuracy of passive radar systems that employ the advanced television system committee (ATSC 1.0) signal as a signal of opportunity. The monostatic and bistatic modified Cramér-Rao lower bound for the range and velocity measurements are derived as a quantitative way to evaluate the performance variation when exploiting multiple transmitters. The effect of 3D target position on the signal-to-noise ratio, with respect to stationary transmitters and receiver, is highlighted. Furthermore, signal-to-interference-and-noise ratio modeling is included by considering the direct signal interference suppression performance for a set of transmitters. An example in Columbus, Ohio, for a single receiver and multiple digital television transmitters that are spatially distributed is presented to find the optimal emitter that yields the best range and velocity measurement in the analyzed area. Target-tracking experiments show an agreement between the optimal emitter map and the tracking quality for the set of transmitters.

Salp swarm optimization in hybrid beamforming for MIMO radar

The Multi Input Multi Output (MIMO) radar waveform diversity Significantly improves parameter identifiably than phased-array radar performance. Precoding, combining and spatial multiplexing techniques improves the data throughput and reliability of the transmission in MIMO systems. But increment in transmit and receive elements in MIMO antenna array induces considerable increase in required power for hardware and computation cost. Hybrid beamforming employs fewer RF-to-baseband chains. With conscious selection of the weights for pre-coding and combining, hybrid beamforming establishes perfect trade-off between complexity, performance, cost, and power consumption in practical applications. Performance of MIMO radar system can be improved using newly developed bio inspired metaheuristic algorithms as compared to conventional and adaptive beamforming algorithms. In this work the Salp Swarm algorithm (SSA) is implemented to optimize the performance of hybrid beamforming using Raleigh channel and considering the bit error rate and normalized array power parameters. The swarming behavior of salps when navigating and foraging in oceans is the inspiration behind the SSA optimization algorithm. The obtained results are compared with the conventional phase-shift as well as adaptive linearly constrained minimum variance beamforming algorithms on simulation platform with standard considerations. It is observed that this new approach of Salp swarm algorithm is having improved and much better performance with the considered parameters.

추적 유지 성능 개선을 위한 전투기 레이다 추적 파형 운용기법

An active electronically scanned array radar is able to radiate the search beam and track beam more independently than a mechanically scanned array radar. However, as the scan angle increases, the detection performance degrades; as a result, the track-on target could be lost due to scan loss. To overcome the degradation of the tracking performance for off-boresight targets, the effective track-beam operation strategy is proposed to compensate for the scan loss by increasing the dwell time. Because this strategy increases the frame time, which affects the detection performance of the radar system, the detection and track maintenance performance are analyzed systematically.

Collaborative transmit resource scheduling and waveform selection for target tracking in multistatic radar system

This paper proposes a collaborative transmit resource scheduling and waveform selection (CTRSWS) strategy for target tracking in multistatic radar system which consists of one transmitter and an arbitrary number of receivers. The main mechanism of the proposed CTRSWS strategy is to exploit the optimisation technique to jointly optimise the illumination power, dwell time, waveform bandwidth, and pulse length under the constraints of several resource budgets and the predefined waveform library, aiming at improving the low probability of intercept (LPI) performance and target tracking accuracy of multistatic radar system simultaneously. The analytical expressions for the probability of intercept and the trace of the predicted error covariance matrix corresponding to the target state estimation are derived and adopted to evaluate the LPI performance and target tracking accuracy, respectively. Subsequently, the resulting non-convex and non-linear optimisation problem is resolved by an efficient and fast four-stage solution methodology. Several numerical results are provided to verify the effectiveness and superiority of the proposed CTRSWS scheme in terms of the achievable LPI performance and target tracking accuracy of multistatic radar system.

Метод формирующего оператора для моделирования циклостационарных случайных процессов

The paper proposes the shaping operator technique for modelling cyclostationary random process (CSRP) which belong to the class of second-order processes being described by the parametric pulse train model. Generating CSRP is expressed as the propagation result of the specially chosen elementary CSRP through the linear time-invariant system with a known impulse response. The paper describes the approach to forming the elementary CSRP based on the train made of Dirac delta-function uniformly following in time domain with constant step and defining the desired structural periodicity of the process being modelled. The analytical expressions for the main characteristics used for describing cyclostationary properties of the elementary process, including two-dimensional, cyclic and spectral corelation functions, were obtained. In addition to the case of the elementary CSRP with correlated weighting coefficients of delta-functions, the case of statistically independent coefficients was considered. It was shown that utilization of the spectral correlation function (SCF) for describing the cyclic property reveals the explicit analytical relation between characteristics of the elementary and modelled CSRPs provided the filter frequency response is known. The paper presents the comparative example which describes the modelling of two CSRPs: one of them was chosen as the train of rectangle pulses which is pulse amplitude modulated by stationary random time series, while the other is considered as a signal formed by the method of direct sequence spread spectrum. The chosen short-length Barker sequence as the code allowed performing visual comparison between absolute value of SCF components taken at the cyclic frequencies multiple of the chip frequency and cyclic frequencies multiple of the symbol frequency. The future development of the methods proposed in the paper opens the road to improving the performance of modern radar and telecommunication systems by means of utilizing cyclic frequencies which are non-random parameters describing the structural properties of signals under processing.

Dictionary Learning and Waveform Design for Dense False Target Jamming Suppression

For linear frequency modulation (LFM) pulse radars, dense false targets generated by new system jamming seriously damage the performance of such radar systems. In order to avoid the influence of dense false target jamming, an anti-jamming strategy combining waveform design and sparse decomposition are proposed. Specifically, the radar system transmits a random pulse initial phase (RPIP) signal, and uses peak detection method to detect the deception jamming. The phase distribution of the RPIP signal is partially randomly perturbed for a jamming, and we use optimization algorithm to design a phase perturbed LFM (PPLFM) signal with good autocorrelation characteristics. Using the correlation function of the designed signal, the target sample set and the jamming sample set are constructed, and the target echo and the jamming signal are separated using designed dictionary learning method to achieve suppression of dense false target jamming and range side-lobes. The effectiveness of the proposed method is verified by numerical simulation, and the results proved that this proposed method maintains good anti-jamming performance under low signal-tonoise ratio (SNR).

Radar Waveform Design Under Communication Sum Capacity Constraint

This paper considers a joint radar and wireless communication systems where the radar transmit waveform is adaptively designed. To ensure acceptable performance of both radar and communication systems operating in the same frequency bands, the radar makes use of knowledge provided by the communication systems and vice versa. Specifically, the radar transmit waveform is designed not only to maximize radar performance such as signal-to-interference-and-noise ratio (SINR) but also to guarantee acceptable communication systems performance by ensuring a prescribed total throughput or sum capacity of communication systems. We formulate an optimization problem that maximizes the radar performance subject to the radar power constraint and the communication sum capacity constraint. Since the sum capacity constraint is not a convex constraint, the resulting optimization problem is not convex. We provide a geometric analysis of the sum capacity constraint and the solution of the SINR maximization problem in two steps: 1) obtain the optimal solution with only radar power constraints, i.e., without the sum capacity constraint, and then 2) starting from the optimal solution of the first step, find a solution satisfying the sum capacity constraint. In this process, a closed form solution to find the locally optimal point at each search is derived, which reduces computational complexity of the proposed algorithm. Numerical results are provided to verify performance of the proposed method.