Chunxi Dong

Computationally Efficient 2-D DOA Estimation for L-Shaped Array With Automatic Pairing

As L-shaped array can provide good angle estimation performance and is easy to implement, many two-dimensional (2-D) direction-of-arrival (DOA) estimation algorithms have been developed. In this letter, we present a low-computation-complexity DOA estimation method for L-shaped array that exploits the conjugate symmetry property of the array manifold matrix to increase the effective array aperture and improve the angle estimation performance. Hence, the DOA estimation is obtained via combining propagator method (PM) with ESPRIT algorithm, which does not need spectrum peak search or additional angle pair matching procedure. Simulation results demonstrate the effectiveness of the proposed method.

The Influence of Rebound Jamming on SAR GMTI

Ground moving-target indication (GMTI) has been extensively used in the measuring of ocean surface currents and ground traffic. The influence of rebound jamming on synthetic aperture radar (SAR) GMTI is studied in this letter. The rebound jamming signal is either deceptive or barrage jamming according to the time delay. When the time delay between each pulse is constant, the jamming focused on a morphed image of the imaging area. After displaced phase-center antenna (DPCA) processing, the image with azimuth near the jammers azimuth will be canceled similar to stationary targets, and the other part of the DPCA image remains. When the time delay is random between each pulse, the rebound jamming is barrage jamming for both the SAR image and the DPCA image. The validity of the proposed method is verified by theoretic analysis and simulation results.

2-D DOA Estimation for L-Shaped Array With Array Aperture and Snapshots Extension Techniques

A two-dimensional (2-D) direction of arrival estimation method for L-shaped array with automatic pairing is proposed. It exploits the conjugate symmetry property of the array manifold matrix to increase the effective array aperture and the number of virtual snapshots simultaneously, and then applies the principle of MUSIC to construct an angle cost function and transforms the conventional 2-D search into 1-D via a Rayleigh quotient, which can greatly reduce the computation complexity. Finally, the azimuth and elevation angles are estimated without pair matching. Simulation results show that the proposed method has a better performance and can resolve more sources than some existing computationally efficient methods.

Conjugate Augmented Spatial Temporal Technique for 2-D DOA Estimation With L-Shaped Array

To solve the angle ambiguity problem when multiple sources have the same azimuth or elevation angles, a novel two-dimensional direction of arrival (2-D DOA) estimation method with L-shaped array based on conjugate augmented spatial temporal technique is developed in this letter. The basic idea of the proposed method is to utilize the conjugate symmetry property of the signal auto-correlation function with different delays to construct a conjugate augmented spatial-temporal cross-correlation matrix (CAST-CCM) and form joint diagonalization structure from the signal subspace corresponding to the CAST-CCM. Hence, the DOAs are estimated and paired automatically via joint diagonalization technique. The proposed method can handle the angle ambiguity problem efficiently and can also work in the underdetermined case. The effectiveness of the proposed method is verified through computer simulations.

Broadband DOA Estimation Based on Nested Arrays

Direction of arrival (DOA) estimation is a crucial problem in electronic reconnaissance. A novel broadband DOA estimation method utilizing nested arrays is devised in this paper, which is capable of estimating the frequencies and DOAs of multiple narrowband signals in broadbands, even though they may have different carrier frequencies. The proposed method converts the DOA estimation of multiple signals with different frequencies into the spatial frequency estimation. Then, the DOAs and frequencies are pair matched by sparse recovery. It is possible to significantly increase the degrees of freedom (DOF) with the nested arrays and the number of sources can be more than that of sensor array. In addition, the method can achieve high estimation precision without the two-dimensional search process in frequency and angle domain. The validity of the proposed method is verified by theoretic analysis and simulation results.

Two-dimensional DOA estimation for L-shaped array with nested subarrays without pair matching

Non-uniform L-shaped array consisting of two nested arrays and its computationally efficient two-dimensional direction-of-arrival (DOA) estimation method are developed in this study. The basic idea of the proposed method is to utilise the property of nested arrays and the conjugate symmetry property of the signal auto-correlation function for different time lags to construct a conjugate augmented spatial–temporal cross-correlation matrix (CAST-CCM) and form joint diagonalisation structure from the signal subspace corresponding to the CAST-CCM. Hence, the DOAs are estimated and paired automatically via signal subspace joint diagonalisation technique. The proposed method can handle underdetermined DOA estimation with automatic matching and deal with the angle ambiguity problem when multiple sources have the same azimuth or elevation angles. Meanwhile, the proposed method is computationally efficient without multidimensional search. The effectiveness of the proposed method is verified through computer simulations.

A Novel Plasma Jamming Technology Based on the Resonance Absorption Effect

Based on the resonance absorption effect of plasma, the mechanism of plasma jamming technology is studied and verified in this letter. Different from the power perspective, the effects of plasma on the radar echo waveform and the radar signal detection are studied. It is found that the radar echo waveform is distorted and the performance of pulse compression is degraded. Moreover, the phenomenon of radar false targets appears with several meters apart. Thus, plasma could not only act as electromagnetic wave absorbers, but also a kind of passive jammer. Finally, many optimal plasma parameters are presented to achieve desired jamming effects for different radar frequencies. These data provide some useful references to plasma jamming technology.

Evaluations of Plasma Stealth Effectiveness Based on the Probability of Radar Detection

To overcome the limitations of radar cross section characteristic, a method using detection probability as an indicator to evaluate plasma stealth effectiveness is proposed in this paper. Based on shift operator finite-difference time-domain method, the distorted waveform of linear frequency modulation radar echo is obtained when the targets coated with plasma. Then, by making a comparison between outputs of pulse compression with and without plasma, the peak instantaneous signal-to-noise ratio (SNR) loss is calculated. According to the signal detection theory, the relationship between plasma parameters and radar detection probability is built up through the SNR loss, in which the attenuation of radar echo and the mismatch loss of pulse compression are both considered. Finally, effects of plasma parameters including electron density, collision frequency, and radar frequency on the probability of detection have been studied systematically. By adopting detection probability

A Deception Jamming Method Countering Bi- and Multistatic ISAR Based on Micro-Doppler Effect

P_{d }\le 0.1

The mosaic scene deception jamming based on 2-D separation modulation against SAR

as a valid criterion, the effective plasma parameters for different radar frequencies are given as a guide when using plasma for stealth application.