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Purpose The purpose of this paper is to present and solve the problem of adaptive beamforming (ABF) for a uniform linear array (ULA) as an optimization problem. ABF mainly concerns with estimation of weights of antenna array so as to direct the major lobe in the direction of desired user and nulls in the direction of interfering signals with reduced side lobe level (SLL).Design/methodology/approach The potential of gravitational search algorithm is explored to optimize multi-objective fitness function for ABF using MATLAB software.Findings The performance of the algorithm has been compared by considering different number of interference signals at different power levels. The proposed algorithm presents good convergence rate and accurate steering of main lobe and nulls with reduced SLL compared to the well-known ABF technique, namely, minimum variance distortionless response (MVDR) and previously reported results. The simulation results are presented in tabular form.Research limitations/implications The present work is limited to simulation. The researchers are encouraged to solve the problem of ABF using the proposed approach in hardware.Originality/value The application of proposed algorithm is to optimize multi-objective function for ABF with reduced SLL in linear antenna arrays. [ABSTRACT FROM AUTHOR]

Abstract: The problem of calibration has arisen because the phase characteristics of signal paths associated with each antenna in a smart antenna system (SAS) are different (in both receiving (RX) and transmitting (TX) modes). In this paper, we propose a simple and accurate calibration technique for eliminating the phase characteristic difference of the signal path associated with each antenna element in both RX and TX modes. Also, through the experimental data obtained from SAS, which has been implemented with the CDMA2000 1X standard, we confirm that the proposed technique has eliminated the characteristic difference. [Copyright &y& Elsevier]

Abstract: This paper presents a performance analysis of PN-code acquisition in a smart antenna system operating in Rayleigh fading channels with various degrees of angular spread in the arrival direction of the received signal. It was determined that the performance enhancement provided by the smart antenna system is upper- and lower-bounded by the degrees of statistical independence between channel responses associated with each of the antenna elements. The performance of PN-code acquisition in a smart antenna system is then determined in accordance with the degree of angular spread in the range determined by the upper and lower bounds. The theoretical analysis for deriving the bounds shown in this paper is verified through extensive computer simulations with various angular spreads encountered in the Rayleigh fading channel. [Copyright &y& Elsevier]

Karystinos, G. N., Qian, H., Medley, M. J., and Batalama, S. N., Short Data Record Adaptive Filtering: The Auxiliary-Vector Algorithm, Digital Signal Processing12 (2002) 193–222Based on statistical conditional optimization criteria, we developed an iterative algorithm that starts from the matched filter (or constraint vector) and generates a sequence of filters that converges to the minimum variance distortionless response (MVDR) solution for any positive definite input autocorrelation matrix. Computationally, the algorithm is a simple recursive procedure that avoids explicit matrix inversion, decomposition, or diagonalization operations. When the input autocorrelation matrix is replaced by a conventional sample-average (positive definite) estimate, the algorithm effectively generates a sequence of MVDR filter estimators: The bias converges rapidly to zero and the covariance trace rises slowly and asymptotically to the covariance trace of the familiar sample matrix inversion (SMI) estimator. For short data records, the early, nonasymptotic, elements of the generated sequence of estimators offer favorable bias–covariance balance and are seen to outperform in mean-square estimation error constraint-LMS, RLS-type, and orthogonal multistage decomposition estimates (also called nested Wiener filters) as well as plain and diagonally loaded SMI estimates. The problem of selecting the most successful (in some appropriate sense) filter estimator in the sequence for a given data record is addressed and two data-driven selection criteria are proposed. The first criterion minimizes the cross-validated sample average variance of the filter estimator output. The second criterion maximizes the estimated J-divergence of the filter estimator output conditional distributions. Illustrative interference suppression examples drawn from the communications literature are followed throughout this presentation. [Copyright &y& Elsevier]

Amin, M., Zhang, Y., Mancuso, V., and Hoorfar, A., Applications of Smart Antennas to Rotorcrafts, Digital Signal Processing12 (2002) 159–174Transmitted and received signals involving rotorcrafts are subject to intermodulations caused by the rotor blades. In this paper, the statistical characteristics of the wireless communication link between a rotorcraft transmitter and a receiver on the ground are developed. Both the scattering and Doppler effects of the rotating blades on the impairment of frequency modulated frequency hopping signals are considered. The channel model includes the near-field wave propagation between the transmitter antenna and the scattering blades. The channel model is used to examine the performance of different diversity techniques, namely, the transmitter diversity, multicarrier frequency hopping, and the fast frequency hopping, in view of antenna polarization and relative strength of the direct path and the scattering component from the rotating blades. [Copyright &y& Elsevier]

The article reports that researchers of Utah State University (USU) are working on technology to allow a single antenna to change its properties to address frequency, polarization and radiation pattern. Topics include views of associate professor Bedri Cetiner on smarter antenna technologies, grant received by USU from U.S. Air Force, and the ability of antenna to change its dimensions to better function with varying signals.