Victim Radar Research Articles

FMCW Interference Waveform Estimation Based on Intentional Local Interference for Automotive Radars

We propose a new method to estimate the waveforms of frequency-modulated continuous-wave (FMCW) interferers by intentional interference. The proposed method utilizes the crossing interference of FMCW radar by adaptive waveform configuration. The victim radar analyzes the periodicity and frequency of the interference signal from the mixer at the FMCW receiver. The bandwidth, slope, and intervals of the interferer waveform are derived from multiple adaptive waveforms from interference detection results. The estimated time and frequency waveform parameters of the interferer can be utilized to generate an interference-free waveform. The proposed approach has been tested and validated using two different mmWave commercial off-the-shelf automotive FMCW radars: the AWR2243 and AWR2944 evaluation boards. In three different scenarios in indoor and outdoor environments, the proposed method successfully estimated interferer waveform parameters with 0.9 seconds of monitoring processing and less than 3% error.

Robust automotive radar interference mitigation using multiplicative-adaptive filtering and Hilbert transform

Radar is one of the sensors that have significant attention to be implemented in an autonomous vehicle since its robustness under many possible environmental conditions such as fog, rain, and poor light. However, the implementation risks interference because of transmitting and/or receiving radar signals from/to other vehicles. This interference will increase the floor noise that can mask the target signal. This paper proposes multiplicative-adaptive filtering and Hilbert transform to mitigate the interference effect and maintain the target signal detectability. The method exploited the trade-off between the step-size and sidelobe effect on the least mean square-based adaptive filtering to improve the target detection accuracy, especially in the long-range case. The numerical analysis on the millimeter-wave frequency modulated continuous wave radar with multiple interferers concluded that the proposed method could maintain and enhance the target signal even if the target range is relatively far from the victim radar.

Emulation and Malicious Attacks to Doppler and FMCW Radars for Human Sensing Applications

This article presents emulation and adverse attack scenarios for Doppler radar-based motion sensors and frequency-modulated continuous-wave (FMCW) radars employed for noninvasive vital signs measurement and human presence sensing. In contrast to existing radar threat models, the proposed model is tuned to mimic two characteristics of a human target measured by radars, i.e., the motion artifacts generated by a walking human and the inherent chest motion. Electronically synthesizing the abovementioned characteristics can interfere with the normal operation of radar systems used for automation, bioauthentication, and surveillance applications. The attacking/emulation systems were realized using commercially available radio frequency (RF) components. The 5.8-GHz benchtop prototypes of the Doppler- and FMCW-mode systems were designed, and experiments were conducted to validate the threat of these systems. First, a single-sideband (SSB) mixer is utilized to electronically modulate the continuous-wave (CW) signal transmitted by a Doppler radar to resemble a walking human subject. Next, fake human targets are injected into an FMCW radar by using an analog phase shifter that mimics the vital sign motion of a real human subject. In addition to impersonating the human vital sign motion, the FMCW mode spoofing system has the capability to alter the range of the human target without requiring any synchronization with the victim radar. The FMCW mode spoofing system successfully deceived two state-of-the-art human detection algorithms. Finally, a brief discussion is presented on the feasibility of using the proposed Doppler and FMCW mode spoofing device architecture as respective radar target emulators.

Interrupted-Sampling Repeater Jamming-Suppression Method Based on a Multi-Stages Multi-Domains Joint Anti-Jamming Depth Network

Jamming will seriously affect the detection ability of radar, so it is essential to suppress the jamming of radar echoes. Interrupted-sampling repeater jamming (ISRJ) based on a digital-radio-frequency-memory (DRFM) device can generate false targets at the victim radar by the interception and repeating of the radar transmission signal, which is highly correlated with the true target signal. ISRJ can achieve main lobe jamming and has both deception and oppressive jamming effects, so it is difficult for the existing methods to suppress this jamming effectively. In this paper, we propose a deep-learning-based anti-jamming network, named MSMD-net (Multi-stage Multi-domain joint anti-jamming depth network), for suppressing ISRJ main lobe jamming in the radar echo. In the first stage of MSMD-net, considering that the target signal is difficult to detect under a high jamming-to-signal ratio (JSR), we propose a preprocessing method of limiting filtering on the time-frequency domain to reduce the JSR using the auxiliary knowledge of radar. In the second stage, taking advantage of the discontinuity of the jamming in the time domain, we propose a UT-net network that combines the U-net structure and the transformer module. The UT-net performs target feature extraction and signal reconstruction in the signal time-frequency domain and preliminarily realizes the suppression of the jamming component. In the third stage, combined with phase information, a one-dimensional complex residual convolution U-net network (ResCU-net) is constructed in the time domain to realize jamming filtering and signal recovery further. The experimental results show that MSMD-net can obtain the best jamming suppression effect under different transmitted signals, different jamming modes, and different jamming parameters.

Automotive radar interference study for different radar waveform types

Mutual interference between different radar waveforms used in automotive radar applications is studied. The existing interference analysis is extended to a generalised radar-to-radar interference equation that covers most of the common interference scenarios for automotive radar systems. The outcome of the generalised equation is demonstrated for a number of typical scenarios where radars with different continuously transmitting waveforms are involved. The proposed equation can be used to characterise the received interference and its features by analysing the instantaneous beat frequency of the victim radar. Moreover, an interference analysis of phase-coded frequency-modulated continuous waveforms is performed and demonstrated experimentally by using real-time automotive radars for the first time in the literature. The experimental results corroborate the interference analysis of different waveforms and validate the proposed generalised interference equation under various conditions.

Automotive interference statistics and their effect on radar detector

Millimetre-wave frequency-modulated continuous wave (FMCW) radars are at present widely deployed in the autonomous vehicles. The growing usage of such sensors, as a vital part of a robust future autonomous sensing system, sees the potential for significant increase in mutual interference and adverse effects on sensor operation. Effective target detection in the background of interference requires knowledge of the interference statistics. In the case that such statistics are found to be similar to that of additive white Gaussian noise (AWGN), then classical well-established detection techniques can be applied. Conversely, if statistics are found to be different, traditional techniques (matched filtering) will not be optimal. Here, a statistical analysis of mutual interference within an FMCW victim radar is presented. The majority of cases show a low correlation between the interference pulses received at the victim radar, with close to a Gaussian distribution. Some specific cases show a high correlation between the interference pulses in the victim radar chirps with a sinusoidal-like distribution, which degrades the victim radar’s detection performance. The presented analysis is validated by experimental data for various interference cases.

A Frequency-Domain Spoofing Attack on FMCW Radars and Its Mitigation Technique Based on a Hybrid-Chirp Waveform

This article presents a novel spoofing device capable of injecting false target information into a frequency-modulated continuous-wave (FMCW) radar. The spoofing device uses a radio frequency (RF) single-sideband (SSB) mixer to introduce a frequency shift to the incoming RF signal transmitted by the victim radar and retransmits the modulated RF signal. The modulated RF signal resembles a false target. Upon down-conversion on the receiver chain of the victim radar, the modulated RF signal creates an illusion of a real target in the radar signal processing system. The frequency shift can be adjusted to vary the range of the spoofed target. The theory of the spoofing mechanism was developed, and a 5.8 GHz prototype was built for experimental validation. Experimental results demonstrate the ability of the proposed spoofing device to inject a false target at any arbitrary range. A hybrid-chirp FMCW approach was proposed and verified as a countermeasure to distinguish a real target from a spoofed target to mitigate the RF-spoofing attack.

Analysis and Investigation of Disturbance in Radar Systems Using New Techniques of Electronic Attack

With the end of World War II and the rapid advent of war technology, wars have shifted to electronic warfare, and today a nation can win wars that are more powerful in the field of telecommunications and electronic warfare. The purpose of this article is to promote new content in the field of electronic warfare and we try to introduce and introduce new techniques of electronic attacks on victim radar systems. With the exception of false targets created by point or sweep jams, most false targets are created with automatic responders or repeaters. An automatic response generator for producing false targets includes a receiver, a variable delay circuit, a signal generator, a power amplifier, and an antenna. Upon receiving a pulse from the threatening radar, the transponder waits for the time corresponding to the target man's distance to the false target, and then sends a similar echo signal to the radar. . As soon as the pulse is received from the threatening radar, the transponder delays it sufficiently to cause the difference in distance to create a false target. Then, a pulse similar to the RF echo pulse of the radar is returned to it.

Phenomenology of automotive radar interference

Mutual interference in automotive radar is expected to become a major issue owing to the rapid increase in the number of vehicles on the road equipped with radar. The phenomenology of interference in frequency modulated continuous wave radar is presented. Interference is empirically analysed at every signal processing stage in the victim radar by means of experimentally verified simulation modelling. Knowledge of how interference manifests in different domains provides a useful tool to develop algorithms for interference detection, mitigation and/or avoidance. The receiver's filter response is analysed to minimise the interference duration and increase the effectiveness of time-domain mitigation techniques. A innovative method of interference parameter extraction by using spectrograms is also introduced.

Jamming effect evaluation method based on radar behavior recognition

Rapid and accurate evaluation of radar jamming effect is an important link to enhance the effectiveness of cognitive electronic warfare. Based on the correlation between nodes of networked combat systems, this paper proposes a method to judge the jamming effect of radar through behavior recognition. The attacker utilizes its own sensors to perceive the behaviors of victim radar and its cooperative radar, uses support vector machine (SVM) algorithm to identify and classify their behaviors, marks the classification result as jamming effect label, determines the influence of jamming on the working state of radar, and evaluates the jamming effect of the victim radar. The simulation results show that the proposed method has higher accuracy than the traditional method that only considers victim radar’s behaviors, and the kernel function selection and the dimension of behavior parameters are closely related to the accuracy of the evaluation results.

Interference in Automotive Radar Systems: Characteristics, Mitigation Techniques, and Current and Future Research

This article examines the problem of interference in automotive radar. Different types of automotive radar as well as mechanisms and characteristics of interference and the effects of interference on radar system performance are described. The interference-to-noise ratio (INR) at the output of a detector is a measure of the susceptibility of a radar to interference. The INR is derived from different types of interfering and victim radars and depends on the location of both as well as parameters such as transmit power, antenna gain, and bandwidth. In addition, for victim radar with beamscanning, INR depends on the location of the target the victim radar is attempting to detect. Analysis is presented to show the effects of various interference scenarios on the INR. A review of the current state of the art in interference mitigation techniques previously deployed as well as areas of research currently being addressed is then provided. Finally, important future research directions are suggested.

Interrupted-Sampling Repeater Jamming Suppression Based on Stacked Bidirectional Gated Recurrent Unit Network and Infinite Training

Interrupted-sampling repeater jamming (ISRJ) is coherent jamming based on digital radio frequency memory (DRFM) device, which repeatedly samples, stores, modulates, and retransmits part of the radar emitted signal, and flexibly forms false targets in the victim radar with relatively low transmitting power. It significantly interferes the radar to detect, track, and recognize targets. There are many electronic counter-countermeasures against ISRJ, among which a series of filtering methods are promising. However, it is not fully addressed. This study proposes a filtering method based on stacked bidirectional gated recurrent unit network (SBiGRU) and infinite training to fulfill the ISRJ suppression for pulse compression (PC) radar with linear frequency modulation (LFM) waveform. SBiGRU method converts signal extraction into a temporal classification problem and accurately extracts the jamming-free signal segments to generate a band pass filter to suppress the ISRJ and retain the real target signal components simultaneously. Comparing with two most advanced filtering methods in the published literature, SBiGRU method has improved the jamming-free signal extraction accuracy, leading to better performances of ISRJ suppression and real targets detection, which are verified by Monte Carlo Simulations.

On deception jamming for countering LFM radar based on periodic 0-π phase modulation

Coherent jamming technology is one of the most important development trends in the modern radar countermeasures. This study presents a method capable of generating a series of deceptive coherent false targets for countering linear frequency modulation (LFM) radar based on periodic 0-π phase modulation. Utilizing the structure of digital radio frequency memory (DRFM), we impose phase modulation onto the intercepted radar signal and retransmit it to the victim radar. The jamming signal model is developed and its characteristics are analyzed in detail. An investigation has been carried out to determine the matched filter properties of the jamming signal. The expressions of some main parameters are deduced step by step. Theoretical analysis and simulation results prove that by flexibly adjusting the phase modulation parameters, different deception jamming effects will be obtained. The proposed method provides an idea for the coherent jamming signal design.

A Novel Noise Jamming Detection Algorithm for Radar Applications

In this letter, we devise and assess a new algorithm to detect a platform equipped with self-screening jamming systems. The latter illuminates the victim radar by means of noise-like signals leading to an increase of the constant false alarm rate threshold (at the detection stage) and a reduction of radar sensitivity. The problem is formulated in terms of a binary hypothesis test exploiting the rank-one modification of the interference covariance matrix introduced by the jammer and the generalized likelihood ratio test is derived. Performance analysis is conducted on simulated data and is aimed at highlighting the effectiveness of this new approach.

Coexistence of Outdoor Wi-Fi and Radar at 3.5 GHz

Coexistence between radar and outdoor wireless fidelity (Wi-Fi) needs thorough study since the IEEE 802.11 working group (WG) opposed the latest rules in 3550–3700 MHz (the 3.5 GHz band) that require “exclusion zones.” This letter proposes a method that suppresses Wi-Fi-to-radar (WtR) interference, in which a Wi-Fi transmitter (TX) is selected to avoid beam angles toward the victim radar. It is distinguished from prior schemes since it ensures that the Wi-Fi remains operable while suppressing the WtR interference.

Suppression of Repeat-Intensive False Targets Based on Temporal Pulse Diversity

This paper considers the problem of suppressing the repeat-intensive false targets produced by a deception electronic attack (EA) system equipped with a Digital Radio Frequency Memory (DRFM) device. Different from a conventional repeat jammer, this type of jamming intensively retransmits the intercepted signal stored in a DRFM to the victim radar in a very short time-delay interval relative to a radar pulse wide. A multipeak matched-filtering output is then produced other than the merely expected true target. An electronic protection (EP) algorithm based on the space time block code (STBC) is proposed to suppress the adverse effects of this jammer. By transmitting a pulse sequence generated from the STBC in succession and the following cancellation process applied upon the received signal, this algorithm performs successfully in a single antenna system provided that the target models are nonfluctuating or slow fluctuating and the pulse repetition frequency (PRF) is comparatively high. The performance in white and correlated Gaussian disturbance is evaluated by means of Monte Carlo simulations.