Forward Scatter Radar Research Articles

Micro-Doppler Estimation and Analysis of Slow Moving Objects in Forward Scattering Radar System

Micro-Doppler signature can convey information of detected targets and has been used for target recognition in many Radar systems. Nevertheless, micro-Doppler for the specific Forward Scattering Radar (FSR) system has yet to be analyzed and investigated in detail; consequently, information carried by the micro-Doppler in FSR is not fully understood. This paper demonstrates the feasibility and effectiveness of FSR in detecting and extracting micro-Doppler signature generated from a target’s micro-motions. Comprehensive theoretical analyses and simulation results followed by experimental investigations into the feasibility of using the FSR for detecting micro-Doppler signatures are presented in this paper. The obtained results verified that the FSR system is capable of detecting micro-Doppler signature of a swinging pendulum placed on a moving trolley and discriminating different swinging speeds. Furthermore, human movement and micro-Doppler from hand motions can be detected and monitored by using the FSR system which resembles a potential application for human gait monitoring and classification.

Forward scatter radar for remote intelligence of building interiors

Through-wall radar allows for remote intelligence of building interiors including stand-off detection and tracking of persons inside a building. However, reliable radar tracking of people inside a building is not trivial. Conventional, monostatic through-wall radar measures the backscatter of moving people. The backscatter from a human is relatively low compared with the scattering from building features or furniture. The forward scatter radar (FSR) concept is proposed to detect and possibly track moving people in specific areas of a building. The FSR concept exploits the forward scatter (FS) of objects, which is typically larger than their backscatter; for humans a factor of 20 is possible. It is shown that stand-off detection of moving people inside a building can be performed reliably and consistently based on their FS.

Looking inside

looking inside

Passive Multifrequency Forward-Scatter Radar Measurements of Airborne Targets Using Broadcasting Signals

This paper demonstrates the feasibility and effectiveness of forward-scatter radar (FSR) target detection based on the signals of opportunity made available by standard radio and TV broadcast transmission stations. This passive FSR (P-FSR) operation is obtained by means of a simple and robust correlation process based on self-mixing. This is shown to be very effective in extracting the characteristic FSR modulation produced by airborne targets, from the signals received from frequency modulated, digital audio broadcasting, and digital video broadcasting transmitters of opportunity. Target detectability is discussed as a function of the carrier frequency, the target size, and its height at the baseline crossing. Experimental results are shown using a wide variety of sources of opportunity, target types, baselines, and receiver configurations. The target signatures obtained from the different illuminators are compared and ways of extracting the kinematic parameters of the aircraft are discussed. This validates the claimed effectiveness and robustness of the P-FSR with the presented processing scheme.

Human Motion Ground Target Signal Processing of Forward-Scattering Radar (FSR) Network

Human Motion Ground Target Signal Processing of Forward-Scattering Radar (FSR) Network

Simultaneous data collection of small maritime targets using multistatic radar and forward scatter radar

Radar detection of small maritime targets is of great interest in the context of coastal and port security for prevention of activities such as smuggling and piracy. Multistatic radar and forward scatter radar offer detection advantages compared with conventional monostatic systems, such as advantageous multi-perspective target view for the former and target radar cross-section enhancement for the latter. In this study, experimental results are presented to characterise simultaneous measurements investigating the detection of a small inflatable boat by a multistatic radar and a forward scatter radar. These results are believed to be the first example of simultaneous experimental comparison of such systems.

Simulation Study of a Small UHF Printed Monopole Antenna for Forward Scatter Radar Network

Simulation Study of a Small UHF Printed Monopole Antenna for Forward Scatter Radar Network

Micro‐Doppler detection in forward scattering radar: theoretical analysis and experiment

Forward scatter radar (FSR) is actively studied in the field of radars, as it has many advantages such as robust to radar absorbing material and possibility in target recognition. In many radar systems, micro-Doppler signature is one of the most distinguished information used for target recognition. Yet, there is lacking in established work on investigating the feasibility of using FSR to detect and analyse micro-Doppler signature generated from micro-motions of moving targets. Hence, a theoretical and experimental investigation of using the FSR to detect micro-Doppler signatures is presented. The preliminary results for both theoretical and experiment investigations verified that the FSR system is capable to detect the micro-Doppler signature for a swinging pendulum attached to the moving trolley.

Forward Scatter Radar for Air Surveillance: Characterizing the Target-Receiver Transition from Far-Field to Near-Field Regions

A generalized electromagnetic model is presented in order to predict the response of forward scatter radar (FSR) systems for air-target surveillance applications in both far-field and near-field conditions. The relevant scattering problem is tackled by developing the Helmholtz–Kirchhoff formula and Babinet’s principle to express the scattered and the total fields in typical FSR configurations. To fix the distinctive features of this class of problems, our approach is applied here to metallic targets with canonical rectangular shapes illuminated by a plane wave, but the model can straightforwardly be used to account for more general scenarios. By exploiting suitable approximations, a simple analytical formulation is derived allowing us to efficiently describe the characteristics of the FSR response for a target transitioning with respect to the receiver from far-field to near-field regions. The effects of different target electrical sizes and detection distances on the received signal, as well as the impact of the trajectory of the moving object, are evaluated and discussed. All of the results are shown in terms of quantities normalized to the wavelength and can be generalized to different configurations once the carrier frequency of the FSR system is set. The range of validity of the proposed closed-form approach has been checked by means of numerical analyses, involving comparisons also with a customized implementation of a full-wave commercial CAD tool. The outcomes of this study can pave the way for significant extensions on the applicability of the FSR technique.

Joint Time-Frequency Signal Processing Scheme in Forward Scattering Radar with a Rotational Transmitter

This paper explores the concept of a Forward Scattering Radar (FSR) system with a rotational transmitter for target detection and localization. Most of the research and development in FSR used a fixed dedicated transmitter; therefore, the detection of stationary and slow moving target is very difficult. By rotating the transmitter, the received signals at the receiver contain extra information carried by the Doppler due to the relative movement of the transmitter-target-receiver. Hence, rotating the transmitter enhances the detection capability especially for a stationary and slow-moving target. In addition, it increases the flexibility of the transmitter to control the signal direction, which broadens the coverage of FSR networks. In this paper, a novel signal processing for the new mode of FSR system based on the signal’s joint time-frequency is proposed and discussed. Additionally, the concept of the FSR system with the rotational transmitter is analyzed experimentally for the detection and localization of a stationary target, at very low speed and a low profile target crossing the FSR baseline. The system acts as a virtual fencing of a remote sensor for area monitoring. The experimental results show that the proposed mode with the new signal processing scheme can detect a human intruder. The potential applications for this system could be used for security and border surveillance, debris detection on an airport runway, ground aerial monitoring, intruder detection, etc.

Analysis on Target Detection and Classification in LTE Based Passive Forward Scattering Radar.

The passive bistatic radar (PBR) system can utilize the illuminator of opportunity to enhance radar capability. By utilizing the forward scattering technique and procedure into the specific mode of PBR can provide an improvement in target detection and classification. The system is known as passive Forward Scattering Radar (FSR). The passive FSR system can exploit the peculiar advantage of the enhancement in forward scatter radar cross section (FSRCS) for target detection. Thus, the aim of this paper is to show the feasibility of passive FSR for moving target detection and classification by experimental analysis and results. The signal source is coming from the latest technology of 4G Long-Term Evolution (LTE) base station. A detailed explanation on the passive FSR receiver circuit, the detection scheme and the classification algorithm are given. In addition, the proposed passive FSR circuit employs the self-mixing technique at the receiver; hence the synchronization signal from the transmitter is not required. The experimental results confirm the passive FSR system’s capability for ground target detection and classification. Furthermore, this paper illustrates the first classification result in the passive FSR system. The great potential in the passive FSR system provides a new research area in passive radar that can be used for diverse remote monitoring applications.

STATISTICAL ANALYSIS FOR TERENGGANU FORWARD SCATTER RADAR SEASIDE CLUTTER

The statistical analysis for Terengganu, Malaysia seaside clutter is presented in this paper. The measured clutter data were collected using a prototype of forward scatter radar (FSR) micro-sensor network with very high frequency (VHF) and ultra-high frequency (UHF) bands. Four categories of clutter strength were recorded during the measurements, which are low, medium, strong and very strong clutter. The classes were divided according to the wind speed occurred during the measurements period. The analysis is to determine the best-fit distribution model for the measured clutter data. Four types of distribution models are used in this analysis, which are Weibull, Gamma, Log-Logistic and Log-Normal distribution. One of the goodness of fit (GOF) tests called root mean square error (RMSE) is used to prove which distribution is a better fit to the probability distribution of the measured clutter data. The obtained results show that for 64 MHz with all clutter level strength, Weibull distribution provides better fit and records the lowest RMSE. Weibull distribution also fits best to the clutter data for low clutter of 151 MHz. However, for the rest of clutter level strength for 151 MHz, Gamma distribution is the best-fitted model with lowest RMSE values. Log-Logistic distribution proves to be the best fitted model to all clutter level strength of clutter data for 434 MHz with smallest RMSE values.

Improved Reconstruction of Radio Holographic Signal for Forward Scatter Radar Imaging.

Forward scatter radar (FSR), as a specially configured bistatic radar, is provided with the capabilities of target recognition and classification by the Shadow Inverse Synthetic Aperture Radar (SISAR) imaging technology. This paper mainly discusses the reconstruction of radio holographic signal (RHS), which is an important procedure in the signal processing of FSR SISAR imaging. Based on the analysis of signal characteristics, the method for RHS reconstruction is improved in two parts: the segmental Hilbert transformation and the reconstruction of mainlobe RHS. In addition, a quantitative analysis of the method’s applicability is presented by distinguishing between the near field and far field in forward scattering. Simulation results validated the method’s advantages in improving the accuracy of RHS reconstruction and imaging.

Target motion estimation via multi‐node forward scatter radar system

The focus of this study is on the estimation of the kinematic parameters of a moving target via a multiple-input-multiple output (MIMO) forward scatter radar (FSR) system. For this purpose, a crossing time-based estimation technique is proposed that exploits the information on the time instants at which the target crosses the individual baselines of multiple FSR nodes to retrieve the target motion parameters. First the accuracy of such technique is investigated from a theoretical point of view through Monte Carlo simulations and then the effectiveness of the proposed approach is demonstrated by applying it to measured MIMO FSR data. Shown results prove the practical applicability of the proposed technique and demonstrate the potential of MIMO FSR configuration.

Experimental verification of maritime target parameter evaluation in forward scatter maritime radar

Maritime security is related to national economic and political interests and is strategically important. One efficient way to accomplish maritime border protection is to use the netted forward scatter radar (FSR). FSR is a special type of bistatic radar that operates in a relatively narrow scattering area along the transmitter–receiver baseline, where the effect of the electromagnetic waves forward scattering on targets is dominant above other scattering mechanisms, and in this case, a forward scatter (FS) cross section may increase by orders of magnitude in comparison with the monostatic radar cross section (RCS). Considered in this study are the major problems of marine forward scattering radar detection and estimation of length of low-profile (small and slow) marine targets using a pre-processing approach. It is based on the assumption that the variation of the phase and amplitude in the Doppler signal signature is stronger inside the FS zone than in an outside region. Two variants of pre-processing algorithms are presented in the study, one for the envelope and the other for the phase. Both variants are based on the use the local variance filtering. The results obtained prove the sufficient improvement in a signal-to-clutter ratio (SCR). Estimation of the marine target length under the low SCR is designed using the assumption of known or previously estimated velocity. Presented results demonstrate high accuracy of length estimation. Considered steps of targets detection and target attributes evaluations are necessary for maritime targets classification. The designed algorithms are verified using a set of experimental records of signals from different marine targets obtained using marine FSR developed by the teams from University of Birmingham, UK and Sofia University, Bulgaria.

Determination of the Difference of the Distances to a Moving Object in the Forward-Scatter Radar Systems with Diversity Reception

We consider a method for determining the difference of the distances from the receiving antennas to a moving object in the systems based on the observation of a forward-scattered field. The method can be used for determining the object location in the forward-scatter radars with several receivers.

Radio holography signal reconstruction and shadow inverse synthetic aperture radar imaging in ground‐based forward scatter radar: theory and experimental results

The radio hologram signal (RHS) extraction is the pre-condition of shadow inverse synthetic aperture radar (SISAR) imaging in forward scatter radar (FSR). However, for a ground-based FSR imaging system, which usually includes an envelope detection module, it is pretty hard to obtain the complex RHS. Thus a novel method for RHS reconstruction is proposed by considering the relationship between the in-phase part and the orthogonal part. The operation of envelope detection is never combined with segmented Hilbert transform before in RHS reconstruction and detailed skills in applying the method are discussed with simulations. Then, the proposed method is verified through real experimental data processing, of which a metal board and a microbus are regarded as the targets. Furthermore, target profiles via SISAR imaging processing are achieved very well when using the reconstructed RHS.

Measured forward‐scatter sea clutter at near‐zero grazing angle: analysis of spectral and statistical properties

To develop forward-scatter radar (FSR) systems for use in maritime applications, a fundamental understanding of the operating environment is required. Currently, there is a lack of published experimental FSR sea clutter data at very low (near-zero) grazing angle over the sea. This data is necessary for the development of FSR systems for maritime applications. Therefore to facilitate further investigation, clutter data for such a system has been recorded at frequencies of 7.5 and 24 GHz with static, medium gain antennas for low sea states 1-3 on the Douglas scale. Analysis of forward scatter propagation phenomena is presented, and spectral and statistical analysis of forward-scatter clutter is performed.

短基线前向散射雷达系统运动目标分辨率分析

According to the system characteristic of short baseline forward scatter radar (FSR), using the prin- ciple of shadow inverse synthetic aperture radar and ambiguity function, the resolution along baseline direction and crossing baseline direction are derived and analytically obtained. It is found that the resolution of crossing baseline direction is proportional to signal wavelength, furthermore, the resolution possibility along baseline di- rection is demonstrated at rst time. Finally, the correctness of resolution analysis is veri ed via the experimental data.

Accurate three-dimensional tracking method in bistatic forward scatter radar

Accurate three-dimensional (3D) tracking in bistatic forward scatter radar (BFSR) isa challenging problem because of absent range resolution and poor measurements. Inthis article, an accurate 3D tracking method of BFSR is proposed. Aiming to overcomethe filter divergence caused by large initial state estimation error, firstly, anaccurate initial state estimation approach is presented based on analytic derivationand Levenberg–Marquardt algorithm, which has the potential to improve theaccuracy of initial state estimation. Furthermore, in order to reduce the computationcost of filtering process and speed up the filtering convergence rate, the accurateinitial state estimation and extended Kalman filter algorithm in BFSR are combined toachieve a precise target 3D tracking. Finally, the proposed accurate tracking methodis verified through comparative analysis of the simulation results.