The authors describe a novel systolic array which can efficiently compute the minimum variance distortionless response (MVDR) from an array of antenna receiver elements in a rapidly changing signal environment. The MVDR beamforming problem amounts to minimising, in a least squares sense, the combined output from an antenna array subject to K independent linear equality constraints each of which corresponds to a chosen 'look direction' The constraints are independent in the sense that, for each new vector of received data samples, it is necessary to compute the minimum array output subject to each constraint in turn. This involves the solution of K independent, but closely related, least squares minimisation problems.

http://ieeexplore.ieee.org/iel3/1842/4835/00190331.pdf

A systolic array processor for MVDR beamforming

An efficient subband adaptive beamformer with perfect reconstruction general parameter filter banks (GPFB) for wideband array antenna is proposed in this paper, which is used to enhance performance of suppressing the interference and accelerate convergence speed of weights. Instead of the conventional FFT filter banks, GPFB are utilized to partition the frequency band into several subbands without aliasing between them. With subbands running at downsampling and in manner of parallel, the loads of computational processing costs, compared with traditional fullband methods, can be alleviated. Deep suppression of the interference and convergence speed of weights are also improved.

An Efficient Subband Method for Wideband Adaptive Beamforming

In this paper, a low-cost intelligent antenna, which has a low profile, high gain and broad bandwidth, is presented. The proposed antenna is an extension of the conventional Electronically Steerable Parasitic Array Radiator (ESPAR) antenna. It consists of one short monopole and twelve folded monopoles. The short monopole is placed in the centre and serves as the driven element, and the twelve folded monopoles serve as parasitic elements. The coupling between the driven and parasitic elements provides capacitive loading to the driven element, leading to a low profile antenna. The use of twelve PIN diodes enables the beamforming being performed by using Transistor-transistor logic (TTL) supply. When interference signals exist, an adaptive beamforming algorithm is employed to choose a radiation pattern with the best signal-to-noise ratio (SNR). The front-to-back ratio (FBR) and SNR is improved by introducing a reconfigurable chock ring (RCR) surrounding the antenna. To validate the concept, a prototype at S band is developed. Both measured and simulated results are presented. The antenna has a height of 24 mm only (0.16 at 2.0 GHz). The measurement results confirm that the antenna is capable of beamforming and beam scanning over 360°range in horizontal plane. The antenna has a broadband bandwidth from 2.0 to 2.5 GHz. Finally, the antenna is employed in a wireless communication system in an office environment and the system link quality is tested. It is shown that the antenna can boost the throughput of wireless system significantly.

https://ietresearch.onlinelibrary.wiley.com/doi/pdf/10.1049/iet-map.2011.0398

Low-cost intelligent antenna with low profile and broad bandwidth

A subband adaptive beamformer with general parameter filter banks (GPFB) for broadband array antennas is presented, which is used to enhance performance of suppressing the interference and accelerate convergence speed of weights. Instead of the conventional FFT filter banks, GPFB are utilized to partition the frequency band into several subbands without aliasing between them almost. Simulation results demonstrate that as subbands running at downsampling and in manner of parallel, the loads of computational processing costs, compared with traditional fullband methods, can be alleviated, deep suppression of the interference and convergence speed of weights are also improved.

Subband method for broadband arrays beamforming

The performance of a sub-band adaptive beamforming array (ABA) using different length quadrature mirror filter banks (QMF) for wideband signals is investigated. Delay taps have to be introduced to the full band ABA for wideband signals' operation for deep suppression of the interference. The addition of more taps may result in an increase of uncorrelated noise to the ABA operation. Hence an undesirable power loss at the direction perpendicular to the ABA may occur. The problem of the loss introduced by the additional taps is overcome by introducing a QMF based sub-banding concept. In this paper, different kernels QMF banks are used for the evaluation and hence the comparison of the beamforming application. The beamforming performance of the ABA using the short kernel QMF (eighth order) sub-band ABA is compared with that using a long kernel QMF (sixteenth order). The sub-band ABA with long kernel QMF shows improved signal gain and deep suppression of interference (similar to the short kernel QMF) in the direction perpendicular to the ABA, compared to the full band ABA.

https://www.ijcnis.org/index.php/ijcnis/article/download/29/29

Enhanced Wideband Adaptive Arrays with Different Length Quadrature Mirror Filter Banks

An efficient subband adaptive beamforming array (ABA) using a quadrature mirror filter (QMF) bank is presented. For wideband beamforming, taps have to be added to the full-band ABA for efficient suppression of the interference. However, the introduction of multiple taps results in the addition of uncorrelated noise to the ABA. This results in power loss in the direction perpendicular to the ABA. In order to compensate for the loss introduced by the addition of taps, the proposed concept is investigated. This configuration shows improved signal gain and deep suppression of the interference in the direction perpendicular to the ABA.

S. Chandran

Papers

Wideband adaptive beamforming array with improved radiation characteristics