Performance Of Adaptive Array Antennas Research Articles

A New Blind Beamforming and Hop-Timing Detection for FH Communications

Hop-timing detection is of extreme importance for the reception of frequency hopping (FH) signals. Any error in the hop-timing detection has a deleterious effect on the performance of the receiver in frequency hopping (FH) communication systems. However, it is not easy to detect the hop-timing under low signal to noise power ratio (SNR) environments. Adaptive array antennas (AAA) have been expected to improve the performance of FH communication systems by beamforming for the direction of arrival of the desired signal. Since the conventional AAA exploits at least the coarse synchronization for dehopping of FH signals before achieving the beamforming, any fault in the hop-timing detection causes the deterioration of the performance of AAA. Using AAA based on the constant modulus algorithm (CMA), this paper proposes a new method for blind beamforming and hop-timing detection for FH signals. The proposed method exploits both the spatial and temporal characteristics of the received signal to accomplish the beamforming and detect the hop-timing without knowing any a priori information such as fine/coarse time synchronization and training signal. The performance verifications of the proposed method based on pertinent simulations are presented.

Performance of adaptive array antennas in mobile fading environment

A performance comparison between uniformly and non-uniformly spaced adaptive array antennas in a mobile fading environment is presented. Here, deterministic and simulation models of the frequency-non-selective mobile fading channels are investigated and used to explain the behaviour of steered beam adaptive arrays in terms of the output signal-to-interference-plus-noise ratio and pointing accuracy. It is found that the non-uniformly spaced arrays give a performance improvement of >25% in comparison with the uniformly spaced arrays.

Performance of adaptive array antenna with arbitrary geometry in the presence of mutual coupling

The effect of the mutual coupling between the array elements on the performance of the adaptive array antennas (AAA) is investigated when the actual received voltages which include the mutual coupling are directly used to estimate the weight vector based on the adaptive algorithm. The output signal-to-interference-noise ratio (SINR), the convergence of the adaptive algorithm and the synthesized pattern are evaluated to study the effect due to the existence of the mutual coupling. It is found that the mutual coupling affects the antenna adaptive gain, but does not affect the adaptive processing. It is also found that the mutual coupling does not always degrade the iterative convergence of the adaptive algorithm. It is proved that any invertible matrix for compensating the mutual coupling cannot improve the output SINR. It is also indicated that the radiation pattern can be correctly synthesized in the presence of the mutual coupling by introducing the universal steering vector (USV) whose element corresponds to the array element pattern.

Multipath performance of handset adaptive array antennas in the vicinity of a human operator

This paper examines the performance of the adaptive array antennas used in digital handset systems by studying the minimum mean square error (MMSE) algorithm at 2 GHz. The array is comprised of multiple quarter-wavelength monopole antennas and planar inverted-F antennas (PIFAs). By calculating the spatial correlation between two different directions, we describe how significant enhancement in the capability of reducing interference signals can be achieved, even when the handset is being held in the vicinity of a human operator in the talking position. Secondly, a computer simulation has been carried out under a flat Rayleigh fading environment with multiple cochannel interference signals, in which the average bit error rate (BER) of the handset adaptive array antenna has been characterized for the coherent detection of phase-shift keyed (PSK) signals. The performance of the handset adaptive array is compared to that of an adaptive array comprising plural parallel half-wavelength dipole antennas that are one half-wavelength apart. The performance was also evaluated with regard to the distance between the handset and the human head for different unequal median values and fading correlations of the received signals. The study has revealed that the adaptive array under consideration has substantial potential, not only to reduce the relative power of interference signals, but also to combat multipath fading of the desired signal by using the spatial diversity function of the MMSE, even in close proximity to a human operator.

Analysis of the error performance of adaptive array antennas for CDMA with noncoherent M-ary orthogonal modulation in Nakagami fading

This letter presents an analytical model for evaluating the bit error rate (BER) of a direct sequence code division multiple access (DS-CDMA) system, with M-ary orthogonal modulation and noncoherent detection, employing an array antenna operating in a Nakagami fading environment. An expression of the signal to interference plus noise ratio (SINR) at the output of the receiver is derived, which allows the BER to be evaluated using a closed form expression. The analytical model is validated by comparing the obtained results with simulation results.

Performance of adaptive array antenna at PHS base station

AbstractAssuming the PHS channel, the transmission characteristics of a system in which adaptive arrays are installed only at the base stations are studied. In order to handle co‐channel interference and fading at the same time, the effect of the adaptive array is studied when the antenna element spacing is increased. A computer simulation shows that the bit error rate is improved because a sufficient space diversity effect is obtained and the interference suppression characteristics are not degraded. Improvement of the characteristics is achieved when the weights determined in the uplink are used in the downlink. © 2002 Wiley Periodicals, Inc. Electron Comm Jpn Pt 1, 86(3): 92–101, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecja.1158

Effects of finite weight resolution and calibration errors on the performance of adaptive array antennas

Adaptive antennas are now used to increase the spectral efficiency in mobile telecommunication systems. A model of the received carrier-to-interference plus noise ratio (CINR) in the adaptive antenna beamformer output is derived, assuming that the weighting units are implemented in hardware, The finite resolution of weights and calibration is shown to reduce the CINR. When hardware weights are used, the phase or amplitude step size in the weights can be so large that it affects the maximum achievable CINR. It is shown how these errors makes the interfering signals leak through the beamformer and we show how the output CINR is dependent on power of the input signals. The derived model is extended to include the limited dynamic range of the receivers, by using a simulation model. The theoretical and simulated results are compared with measurements on an adaptive array antenna testbed receiver, designed for the GSM-1800 system. The theoretical model was used to find the performance limiting part in the testbed as the 1 dB resolution in the weight magnitude. Furthermore, the derived models are used in illustrative examples and can be used for system designers to balance the phase and magnitude resolution and the calibration requirements of future adaptive array antennas.