Neural Network-Guided Sparse Recovery for Interrupted-Sampling Repeater Jamming Suppression

Interrupted-sampling repeater jamming (ISRJ) is a new type of DRFM-based jamming designed for linear frequency modulation (LFM) signals. By intercepting the radar signal slice and retransmitting it many times, ISRJ can obtain radar coherent processing gain so that multiple false target groups can be formed after pulse compression (PC). According to the distribution characteristic of the echo signal and the coherence of ISRJ to radar signal, a new method for ISRJ suppression is proposed in this study. In this method, the position of the real target is determined using a gated recurrent unit neural network (GRU-Net), and the real target can be, therefore, reconstructed by adaptive filtering in the sparse representation of the echo signal based on the target locating result. The reconstruction result contains only the real target, and the false target groups formed by ISRJ are suppressed completely. The target locating accuracy of the proposed GRU-Net can reach 92.75%. Simulations have proved the effectiveness of the proposed method.

On Vulnerability of Selected IoT Systems to Radio Jamming—A Proposal of Deployment Practices

Weightless and SigFox are both narrowband communication systems designed for the Internet of Things, along with some other counterparts such as LoRa (Long Range) and narrowband Internet of Things (NB-IoT). As systems dedicated specifically for long-range operations, they possess considerable processing gain for energetic link budget improvement and a remarkable immunity to interference. The paper describes outcomes of a measurement campaign during which the Weightless and SigFox performance was tested against variable interference, generated in an anechoic chamber. Results allow the quantitative appraisal of the system behavior under these harsh conditions with respect to different operational modes of the two investigated IoT systems. The outcomes are then investigated with respect to an intentional radio jammer attempting to block a base station (BS) operation by directly radiating an interfering signal towards it. An Interference Margin is proposed for a quantitative expression of a system’s resilience to jamming. This margin, calculated for all available configuration settings, allows the clear assessment of which combination of a system’s operational parameters does and which does not provide immunity to this type of radio attack.

Performance Characteristics: The Phase Mimo Radar Technique

The phased-MIMO radar technology is the combination of the phased array and the MIMO (Multiple Input Multiple Output) radar technique. This proposed new technique gives the benefits of MIMO radar without sacrificing the main benefits of phased-array radar, which is the gain in coherent processing on the emission side. The intention of the proposed technique is to divide the transmission network into a number of overlapping subnets. This means that each subnet is used to consistently transmit a waveform that is orthogonal to the waveforms transmitted by the other subnets. The MIMO technique applied to traditional phased array radar has been investigated and has yielded many advantages over the phased array radar system and the MIMO radar. A Coherent processing gain can be obtained by designing a weight vector for each subnet to form a beam in a particular direction in space. The proposed technique compared to the previous techniques, which was a phased array and a MIMO radar, is analytically demonstrated and simulated by MATLAB analysis of the corresponding beam patterns and of the overall beam patterns.

Direction of Arrival Estimation Using Two Hydrophones: Frequency Diversity Technique for Passive Sonar

The traditional passive azimuth estimation algorithm using two hydrophones, such as cross-correlation time-delay estimation and cross-spectral phase estimation, requires a high signal-to-noise ratio (SNR) to ensure the clarity of the estimated target trajectory. This paper proposes an algorithm to apply the frequency diversity technique to passive azimuth estimation. The algorithm also uses two hydrophones but can obtain clear trajectories at a lower SNR. Firstly, the initial phase of the signal at different frequencies is removed by calculating the cross-spectral density matrix. Then, phase information between frequencies is used for beamforming. In this way, the frequency dimension information is used to improve the signal processing gain. This paper theoretically analyzes the resolution and processing gain of the algorithm. The simulation results show that the proposed algorithm can estimate the target azimuth robustly under the conditions of a single target (SNR = −16 dB) and multiple targets (SNR = −10 dB), while the cross-correlation algorithm cannot. Finally, the algorithm is tested by the swell96 data and the South Sea experimental data. When dealing with rich frequency signals, the performance of the algorithm using two hydrophones is even better than that of the conventional broadband beamforming of the 64-element array. This further validates the effectiveness and advantages of the algorithm.

On the efficient computation of range and Doppler data in noise radar

In noise radar, digital signal processing algorithms for implementing the computation of the Cross Ambiguity Function through range correlation and Doppler compensation call for optimized solutions. In fact, to achieve a high coherent processing gain, they often compute a large amount of data beyond the maximum range and/or the maximum radial velocity of interest, adding useless information. A novel, efficient algorithm, called Range Filter Bank, is proposed to implement a scope-tailored computation of range/Doppler data in continuous emission noise radar. Downstream its theoretical analysis, the algorithm has been applied to a real-life case study based on dedicated field experiments, in which good quality kinematic data of a car moving at various speeds have been extracted.