Adaptive beamformer

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

Uplink Signaling and Receive Beamforming for Dual-Function Radar Communications

Abstract: Current techniques for dual-function radar-communications (DFRC) have been focused on downlink communication and information embedding into the emission of the radar system. In this paper, we consider the problem of half-duplex uplink communications in dual-function multiple-input multiple-output (MIMO) radar communication systems. The DFRC system consists of a dual-function platform which functions as a MIMO radar during transmit mode and simultaneously receives and processes signals reflected from targets and uplink communication signals transmitted by a communication user. We propose a method for uplink signaling via forming a number of uplink beams carrying the same number of data symbols. Moreover, we employ non-adaptive and adaptive beamforming techniques at the radar receiver to separate the received communication signal from the target return even if they arrive from the same spatial angle. Cross-interference between the received communication and the reflected radar signals is mitigated using adaptive beamforming. We assess the effectiveness of the proposed uplink communication technique by numerical results.

Adaptive Beamforming and Recursive DOA Estimation Using Frequency-Invariant Uniform Concentric Spherical Arrays

Abstract: This paper proposes recursive adaptive beamforming and broadband 2D direction-of-arrival (DOA) estimation algorithms for uniform concentric spherical arrays (UCSAs) having nearly frequency-invariant (FI) characteristics. The basic principle of the FI-UCSA is to transform the received signals to the phase mode and remove the frequency dependency of individual phase modes through a digital beamforming network. Hence, the far-field pattern of the array is determined by a set of weights. Thanks to the FI characteristic, traditional narrowband adaptive beamforming algorithms such as minimum variance beamforming and the generalized sidelobe canceller method can be applied to the FI-UCSA. Simulation results show that the proposed adaptive FI-UCSA beamformer achieves a lower steady-state error and converges faster than the conventional tapped-delay line approach while requiring fewer adaptive coefficients. A new broadband 2-D DOA estimation algorithm using ESPRIT techniques for FI-UCSA is proposed to recursively estimate the DOAs of the moving targets. Simulation results show that the proposed DOA estimation algorithm achieves a satisfactory performance for slowly varying sources at low arithmetic complexity.

MIMO adaptive beamforming for nonseparable multipath clutter mitigation

Abstract: The performance of ground-moving target indicator radars is often degraded in complex terrain by multipath spread-Doppler clutter. Multiple-input, multiple-output (MIMO) beamforming with limited training data has been previously proposed with separable transmit and receive weights appropriate for discrete multipath scenarios. In this paper, partially adaptive MIMO beamforming is presented for suppression of a nonseparable continuum of multipath clutter with limited training data. Simulation results for a forward-looking vehicle-mounted radar in a simplified urban environment are described.

Adaptive beamforming with joint robustness against covariance matrix uncertainty and signal steering vector mismatch

Abstract: A novel adaptive beamforming algorithm that is robust against covariance matrix uncertainty and the signal steering vector mismatch is proposed. Based on the optimisation of the diagonal loading covariance matrix in the sense of minimum mean square error, the mismatch vector between the actual steering vector and the presumed one is estimated iteratively by solving a quadratic convex optimisation problem, which is then used to update the steering vector to obtain the optimal beamformer.

Adaptive beamforming for interference rejection in an OFDM system

Abstract: Orthogonal frequency-division multiplexing (OFDM) has been utilized in various communication systems because of its ability to compensate for multipath channels using simple low-complexity equalizers. However, the performance of OFDM systems can still be compromised due to adjacent channel and cochannel interference. In this paper, we investigate the performance of an adaptive beamforming algorithm for an OFDM system based on the constant modulus (CM) array. We consider this blind technique for a wireless local area network such as the IEEE 802.11a standard. The algorithm exploits the constant modulus property of the low-rate OFDM data carriers, and we show that it can also be used for the nonconstant modulus constellations at higher data rates. We consider the case where cochannel users become active part way into the transmitted packet such that new beamformer weights should be computed to null these interfering signals.