In this paper, a new plasma antenna of beam-forming is investigated based upon the interaction of plasma elements due to the incident electromagnetic wave. It presents a study of the multiple scattering from argon plasma cylinders rigorously applying boundary value method, grounded on the properties of electromagnetic wave transmitted in the argon plasma. Approximate expressions for the total radiation of plasma antenna in the far fleld are derived brie∞y. Such a novel plasma antenna of beam-forming, according to the research, exhibits interesting performance in terms of radiation e-ciency, beam-forming and beam-scanning. Valid results are brought forth to demonstrate the capabilities of such antenna of two scales. Comparisons are given in detail as well.

/pdf/a-new-plasma-antenna-of-beam-forming-4kjlkn4bem.pdf

A new plasma antenna of beam-forming

Direction of arrival (DOA) estimation is the basis for underwater target localization and tracking using towed line array sonar devices. A method of DOA estimation for underwater wideband weak targets based on coherent signal subspace (CSS) processing and compressed sensing (CS) theory is proposed. Under the CSS processing framework, wideband frequency focusing is accompanied by a two-sided correlation transformation, allowing the DOA of underwater wideband targets to be estimated based on the spatial sparsity of the targets and the compressed sensing reconstruction algorithm. Through analysis and processing of simulation data and marine trial data, it is shown that this method can accomplish the DOA estimation of underwater wideband weak targets. Results also show that this method can considerably improve the spatial spectrum of weak target signals, enhancing the ability to detect them. It can solve the problems of low directional resolution and unreliable weak-target detection in traditional beamforming technology. Compared with the conventional minimum variance distortionless response beamformers (MVDR), this method has many advantages, such as higher directional resolution, wider detection range, fewer required snapshots and more accurate detection for weak targets.

DOA Estimation for Underwater Wideband Weak Targets Based on Coherent Signal Subspace and Compressed Sensing.

Phased-array provides range-independent beampattern and consequently it cannot detect/suppress range-dependent targets/interferences. Moreover, an M-element phased-array can resolve at most M − 1 targets simultaneously. This study proposes a nested array receiver using diverse time-delayers (DTDs) for jointly estimating the range and angle of targets. The essence is to construct a new array structure by systematically nesting two uniform linear arrays through DTDs instead of phase controlling in traditional nested array technique. Using the second-order statistics of the received data, an M-element array can resolve O(M 2) targets. Moreover, the nested DTD receiver design is exploited for minimum variance distortionless response beamforming and direction finding. The improvements offered by the proposed method, as compared with basic DTD receivers, are demonstrated by examining the output signal-to-interference-plus-noise ratio, the probability of detection and the Cramer–Rao lower bounds for estimating the range and angle of targets.

https://ietresearch.onlinelibrary.wiley.com/doi/epdf/10.1049/iet-rsn.2015.0450

Nested array receiver with time-delayers for joint target range and angle estimation

A high performance robust beamforming scheme is proposed to combat model mismatch. Our method lies in the novel construction of interference-plus-noise (IPN) covariance matrix. The IPN covariance matrix consists of two parts. The first part is obtained by utilizing the Capon spectrum estimator integrated over a region separated from the direction of the desired signal and the second part is acquired by removing the desired signal component from the sample covariance matrix. Then a weighted summation of these two parts is utilized to reconstruct the IPN matrix. Moreover, a steering vector estimation method based on orthogonal constraint is also proposed. In this method, the presumed steering vector is corrected via orthogonal constraint under the condition where the estimation does not converge to any of the interference steering vectors. To further improve the proposed method in low signal-to-noise ratio (SNR), a hybrid method is proposed by incorporating the diagonal loading method into the IPN matrix reconstruction. Finally, various simulations are performed to demonstrate that the proposed beamformer provides strong robustness against a variety of array mismatches. The output signal-to-interference-plus-noise ratio (SINR) improvement of the beamformer due to the proposed method is significant.

/pdf/high-performance-robust-adaptive-beamforming-in-the-presence-5d60pz0g3f.pdf

High Performance Robust Adaptive Beamforming in the Presence of Array Imperfections

Superdirective beamforming can highly reduce the aperture size of high-frequency receive array. At the same time, the closely spaced elements of a small aperture array can make it low e-ciency and sensitivity to the array uncertainty, which limit its application in practice. Using a parameter called sensitivity factor, we found that array e-ciency and robustness against array error could be considered simultaneously. On that basis, we derive a novel superdirective beamforming criterion based on a constrained sensitivity factor for the HF circular receive array. New method is analytical and computationally inexpensive. Through making the directive gain with a given sensitivity factor maximum, we calculate the optimal weights of the array elements. To illustrate the proposed method can increase the acceptance of HF superdirective receive arrays in practice, several numerical results are provided.

/pdf/robust-superdirective-beamforming-for-hf-circular-receive-4dhak97hgn.pdf

Robust superdirective beamforming for hf circular receive antenna arrays

In this paper, we propose Modifled Interpolated Spatial Smoothing (MISS) algorithm that solves the problem when the inhibition gain generated by Interpolated Spatial Smoothing (ISS) algorithm is not su-ciently high in virtual antenna adaptive beam forming to suppress coherent interference. Using the subspace projection concept, this paper establishes an interference subspace spanned by the interference steering vectors of the virtual antenna array, and then the interference direction information can be imported into the transformation matrix by projecting the transformation matrix into the subspace, which will make the interference components in virtual smoothing covariance matrix enhanced as it is demonstrated by theoretical analysis. Employing the Minimum Variance Distortionless Response (MVDR) beam forming method, the interference inhibition gain and Signal to Interference and Noise Ratio (SINR) performance can be signiflcantly improved.

Y. Li

Papers

On adaptive beamforming for coherent interference suppression via virtual an