Adaptive beamformer

About: Adaptive beamformer is a research topic. Over the lifetime, 4934 publications have been published within this topic receiving 93100 citations.

Two-stage adaptive noise cancellation for intermittent-signal applications (Corresp.)

Abstract: A novel two-stage adaptive signal extractor for intermittent signal applications is presented. If the presence and absence of the signal can be detected, the first stage will adapt only while the signal is absent and thereby effect a reduction in noise, whereas the second stage will adapt only when the signal is present and thereby effect a reduction in the distortion caused by the gust stage. Bounds on performance are derived, and performance improvement relative to a conventional one-stage adaptive noise canceller is assessed.

Apparatus and method for adaptive beamforming in an antenna array

Abstract: An apparatus and a method for receiving and transmitting information from an array of adaptive antenna elements, wherein a predictive filtre (68) supplies an estimate of received signal samples (x(n)) likely to be received in a burst immediately preceding a transmission. Combination (70) of this estimate x(n) with received signal samples (x) obtained from actual (historically received) signals, received over a predetermined number of frames, yields estimates of optimum beamforming coefficients wopt for application (74) to data (76) for transmission from an adaptive array of antenna elements (41). As such, available processing time for obtaining the beamforming coefficents is increased.

Angle of Arrival Estimation Through a Full-Hardware Approach for Adaptive Beamforming

Abstract: This brief introduces a full-hardware approach for Angle of Arrival (AoA) estimation in phased array antennas. The system has a modular structure composed of an analog section to up/down-convert RF signals and a digital section for the AoA estimation. The estimation furnished by the proposed approach can be used to perform adaptive beamforming either to increase the range of operation and/or reduce transmitted power in IoT applications. Some preliminary experimental results are reported validating the proposed strategy for a single narrowband received signal.

The SVD Beamformer: Physical Principles and Application to Ultrafast Adaptive Ultrasound

Abstract: A shift of paradigm is currently underway in biomedical ultrasound thanks to plane or diverging waves coherent compounding for faster imaging. One remaining challenge consists in handling phase and amplitude aberrations induced during the ultrasonic propagation through complex layers. Unlike conventional line-per-line imaging, ultrafast ultrasound provides backscattering information from the whole imaged area for each transmission. Here, we take benefit from this feature and propose an efficient approach to perform fast aberration correction. Our method is based on the Singular Value Decomposition (SVD) of an ultrafast compound matrix containing backscattered data for several plane wave transmissions. First, we explain the physical signification of SVD and associated singular vectors within the ultrafast matrix formalism. We theoretically demonstrate that the separation of spatial and angular variables, rendered by SVD on ultrafast data, provides an elegant and straightforward way to optimize the angular coherence of backscattered data. In heterogeneous media, we demonstrate that the first spatial and angular singular vectors retrieve respectively the non-aberrated image of a region of interest, and the phase and amplitude of its aberration law. Numerical, in vitro and in vivo results prove the efficiency of the image correction, but also the accuracy of the aberrator determination. Based on spatial and angular coherence, we introduce a complete methodology for adaptive beamforming of ultrafast data, performed on successive isoplanatism patches undergoing SVD beamforming. The simplicity of this method paves the way to real-time adaptive ultrafast ultrasound imaging and provides a theoretical framework for future quantitative ultrasound applications.

Adaptive Phased-Array Tracking in ECM using Negative Information

Abstract: Target tracking with adaptive phased-array radars in the presence of standoff jamming presents both challenges and opportunities to the track filter designer. A measurement likelihood function is derived for this situation which accounts for the effect of both positive and negative contact information. This likelihood function is approximated a? a weighted sum of Gaussian terms consisting of both positive and negative weights, accounting for the positive and negative contact information. Additionally, recent theoretical results have been reported which have derived an accurate measurement error covariance in the vicinity of the jammer when adaptive beamforming is used by the radar to null the effects of the jammer. We compare the impact of using a likelihood function that accounts for negative contact information and the corrected measurement error covariance by comparing five Kalman filter-based trackers in five different scenarios. We show that only those track filters which use both the negative contact information and the corrected measurement error covariance are effective in maintaining track on a maneuvering target as it passes through the jamming region. This approach can also be generalized to any target tracking problem where the sensor response is anisotropic.