Frequency diverse array (FDA)-multiple-input multiple-output (MIMO) radars can generate a range-angle two-dimensional transmit steering vector (SV), which is capable of suppressing mainbeam deceptive jamming in the transmit–receive frequency domain by utilizing additional degrees of freedom (DOFs) in the range dimension. However, when there are target SV mismatch, covariance matrix estimation error and target contamination, the jamming suppression performance degrades severely. In this paper, a robust adaptive beamforming algorithm for anti-jammer application based on covariance matrix reconstruction is proposed in FDA-MIMO radar. In this method, the residual noise is further determined by using the spatial power spectrum estimation approach, which results in improved estimation accuracy of the signal covariance matrix and the desired target SV. The jamming SV is obtained from vectors in the intersection of two subspaces (namely, the signal-jamming subspace derived from the sample covariance matrix (SCM) and the jamming subspace generated from the jamming covariance matrix) by an alternating projection algorithm. Furthermore, the jamming power is obtained by exploiting the orthogonality between the different SVs. With the obtained parameters of target and jamming, the optimal adaptive beamformer weight vector is calculated. Simulation results demonstrate that the proposed algorithm can cope with the mainbeam deceptive jamming suppression under various model mismatches and has excellent performance over a wide range of signal-to-noise ratios (SNRs).

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Robust Beamforming Based on Covariance Matrix Reconstruction in FDA-MIMO Radar to Suppress Deceptive Jamming

Joint optimization of SINR and maximum sidelobe level for hybrid beamforming systems with sub-connected structure

An adaptive beamformer is sensitive to model mismatch, especially when the desired signal exists in the training samples. Focusing on the problem, this paper proposed a novel adaptive beamformer based on the interference-plus-noise covariance (INC) matrix reconstruction method, which is robust with gain-phase errors for uniform or sparse linear array. In this beamformer, the INC matrix is reconstructed by the estimated steering vector (SV) and the corresponding individual powers of the interference signals, as well as noise power. Firstly, a gain-phase errors model of the sensors is deduced based on the first-order Taylor series expansion. Secondly, sensor gain-phase errors, the directions of the interferences, and the desired signal can be accurately estimated by using an alternating descent method. Thirdly, the interferences and noise powers are estimated by solving a quadratic optimization problem. To reduce the computational complexity, we derive the closed-form solutions of the second and third steps with compressive sensing and total least squares methods. Simulation results and measured data demonstrate that the performance of the proposed beamformer is always close to the optimum, and outperforms other tested methods in the case of gain-phase errors.

https://www.mdpi.com/1424-8220/20/10/2930/pdf

Robust Adaptive Beamforming with Optimal Covariance Matrix Estimation in the Presence of Gain-Phase Errors.

The invention relates to a navigation anti-interference enhancement load system and method based on a low-orbit satellite. The system comprises a GNSS signal receiving antenna, a GNSS signal down-conversion module, a baseband processing module, a navigation anti-interference signal upper side frequency module, a power amplifier module, a navigation anti-interference signal broadcast antenna, a frequency synthesizer and a constant temperature crystal oscillator. Through a navigation anti-interference signal broadcasted by a navigation anti-interference enhancement load, sensitivity and an anti-interference ability of a ground navigation receiver are increased, and availability of a ground satellite navigation receiver in a complex environment is solved.

Navigation anti-interference enhancement load system and method based on low-orbit satellite

The invention discloses connection planning methods for a low earth orbit communication satellite constellation and subscriber stations. The minimum communication spread angle cosine of satellite-earth core-subscriber station is obtained according to the minimum communication elevation angles of the subscriber stations. Connection sequences between the subscriber stations and the satellite constellation are established according to connectable time. A method for computing user link beam serial numbers is established according to antenna configuration of user link beams. The connection planningproblem between the low earth orbit communication satellite constellation and the subscriber stations is solved.

Connection planning methods for low earth orbit communication satellite constellation and subscriber stations

A weighted subspace-constrained minimum variance distortion-less response (WS-MVDR) beamformer is proposed for robustly controlling the peak sidelobe level (PSL) as well as the sidelobe shape of adaptive array pattern with stable mainlobe. The adaptive weight vector is projected onto the subspace constructed from the weighted sidelobe steering vectors. The norm of the projection is constrained below the derived constant value determined by the desired PSL. The only inequality constraint is introduced to the conventional MVDR beamformer, resulting in a second-order cone programming problem. The numerical results demonstrate that WS-MVDR outperforms existing ones in terms of beampattern control capability and computational complexity.

Weighted Subspace-Constrained Adaptive Beamforming for Sidelobe Control

The invention relates to a low earth orbit satellite smart antenna receiving system and method. The receiving system is composed of an array antenna consisting of N element antennas, N paths of digital receivers and a self-adaptive anti-interference smart antenna digital circuit; the smart antenna receiving system adopts a nulling anti-interference digital multi-beam forming technology and a multi-objective angle estimation technology, which can form a capture beam and a tracking beam at the same time; the tracking beam pointing is adjusted in real time according to a user angle estimation result or satellite orbit characteristics; and the interference nulling positions of the capture and tracking beams are adjusted in real time according to an interference angle estimation result or the satellite orbit characteristics. The low earth orbit satellite smart antenna receiving system provided by the invention can quickly locate the interference and the target, and form a nulling direction pattern in the airspace to suppress the interference of dynamic changes, so that the low earth orbit satellite smart antenna receiving system is especially suitable for a smart antenna system for low earth orbit satellite earth communication.

Low earth orbit satellite smart antenna receiving system and method

In this paper, a fast polarization and power pattern optimization and tracking algorithm based on iterative alternating projection is proposed for dynamic polarized pattern synthesis of vector electromagnetic sensor array. The synthesis problem is functioned and optimized by rapid projection and iteration among multiple subsets for arbitrary polarimetric characteristics and co-polarized pattern with cross-polarization and sidelobe level control. The tracking of dynamically changing polarized pattern can be accurately realized. The numerical simulation experiments on an orthogonal dipole vector electromagnetic sensor array verify the effectiveness and fastness of the proposed algorithm.

Peng Shen

Papers

Weighted Subspace-Constrained Adaptive Beamforming for Sidelobe Control

Low earth orbit satellite smart antenna receiving system and method

Dynamic Polarized Pattern Synthesis of Vector Electromagnetic Sensor Array