Topic
Adaptive beamformer
About: Adaptive beamformer is a research topic. Over the lifetime, 4934 publications have been published within this topic receiving 93100 citations.
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01 Aug 2014
TL;DR: In this article, a general derivation of the quaternion-valued gradient operator is presented and applied to wind profile prediction and the adaptive beamforming problem for vector sensor arrays.
Abstract: Quaternion-valued signal processing has received increasing attention recently. One key operation involved in derivation of all kinds of adaptive algorithms is the gradient operator. Although there have been some derivations of this operator in literature with different level of details, it i s still not fully clear how this operator can be derived in the most general case and how it can be applied to various signal processing problems. In this work, we will give a general derivation of the quaternion-valued gradient operator and then apply it to two different areas. One is to combine with the classic computational fluid dynamics (CFD) approach in wind profile prediction and the other one is to apply the result to the adaptive beamforming problem for vector sensor arrays.
20 citations
01 Jan 1990
TL;DR: Results of the above method applied to digitized snapshot data are presented and Unexpected performance degradations observed in these results are explained and two remedies proposed.
Abstract: This paper elaborates on a technique described in (l) for simultaneously receiving and estimating the directions-of-arrival of multiple cochannel signals impinging on an array of sensors. The method described therein used a combination of adaptive CM Array beamformers anid signal cancellers to sequentially lock onto and re- move emitters one-by-one from the sensor signals. Inherent to the signal cancellation process was the generation of a direction vector associated with the signal being cancelled. In this paper, results of the above method applied to digitized snapshot data are presented. Unexpected performance degradations observed in these results are explained and two remedies proposed. One remedy involves the ad- dition of a parallel arrangement of CM Arrays whose weight wectors are initialized bawd on the cascaded array weight vectors and signal canceller vector:;. The other remedy involves the modification of the error signals used to adapt the signal cancellers
20 citations
TL;DR: It is shown that the array-based GLRT acquisition is equivalent to a conventional acquisition based on the output of a time reference beamformer, even when the array is moderately uncalibrated.
Abstract: This paper addresses the signal acquisition problem in the presence of interferences using antenna arrays in the general framework of Global Navigation Satellite Systems receivers. We describe and compare two different approaches: the first one is based on the generalized likelihood ratio test (GLRT) detector directly applied on the array snapshots, and the second one uses a digital beamformer as a spatial filter to mitigate the interferences and acquire the signal using the beamformer output. We show that the array-based GLRT acquisition is equivalent to a conventional acquisition based on the output of a time reference beamformer. The test statistics of the techniques are analyzed in terms of the probability of detection and false alarm. Monte Carlo simulations using the Galileo E1 signal structure support the theoretical results, even when the array is moderately uncalibrated.
20 citations
TL;DR: A Bernstein-type inequality for stochastic processes of quadratic forms of Gaussian variables is employed to transform the probabilistic constraint to a deterministic form to simplify probability-constrained beamforming.
20 citations
01 Jan 2007
TL;DR: Simulation results show that the proposed adaptive beamformer using FI UCSA can obtain a higher output signal to inference plus noise ratio over the conventional tapped-delay line approach and the usefulness of the proposed UCSA-FIB in broadband 2-D DOA estimation is also verified by computer simulation.
Abstract: This paper proposes a new digital beamformer for uniform concentric spherical array (UCSA) having nearly frequency invariant (FI) characteristics. The basic principle is to transform the received signals to the phase mode and remove the frequency dependency of the individual phase mode through the use of a digital beamforming network. It is shown that the far field pattern of the array is determined by a set of weights and it is approximately invariant over a wide range of frequencies. FI UCSAs are electronic steerable in both the azimuth and elevation angles, unlike their concentric circular array counterpart. The frequency invariant characteristic of the FI UCSA also makes it possible to design separately the compensation network and beamformer weighting coefficients. The design of the compensation network is formulated as a second order cone programming (SOCP) problem and is solved optimally for minimax criterion. Thanks to the frequency invariant characteristic, traditional narrow band adaptive beamforming algorithms such as minimum variance beamforming (MVB) can be applied to the FI UCSA. Also, traditional narrow band 2-D direction of arrival (DOA) estimation algorithms such as unitary ESPRIT can be extended to broadband DOA estimation using FI UCSA. Simulation results show that the proposed adaptive beamformer using FI UCSA can obtain a higher output signal to inference plus noise ratio over the conventional tapped-delay line approach. Simulation results also show that FI UCSA has uniform beampattern and resolution around 360° in both azimuth and elevation angles, unlike FI uniform concentric circular array. The usefulness of the proposed UCSA-FIB in broadband 2-D DOA estimation is also verified by computer simulation.
20 citations