Vehicular speed response adaptive antenna

When an adaptive antenna is used on the downlink receiver side of a moving vehicle, especially in the presence of high‐speed fading, the received signal becomes unsteady and the communications performance is significantly degraded because the updating of the antenna weight is not carried out accurately. In order to resolve this problem, this paper proposes a vehicular speed response adaptive antenna (VSR‐AA). Its performance in a Nakagami–Rice fading environment is evaluated by computer simulation. In order to operate the vehicular speed response VCO, which plays an important role in the proposed VSR‐AA, the angle of arrival of the direct wave must be known. It is shown that the direction can easily be estimated with sufficient accuracy from the maximum gain direction of the characteristic of the adaptively formed beam. By using the proposed VSR‐AA, an improvement of about 10 dB in Eb/N0 at BER = 10−2 can be obtained over the conventional adaptive antenna under the conditions of a Rice factor of 5.0, eight antenna elements, and fDT (product of the maximum Doppler frequency and data symbol length) = 0.05. Further, the BER is substantially degraded in the conventional system as fDT becomes larger. On the other hand, in the proposed system, the BER obtained is almost constant so that a high degree of communications quality is maintained. © 2002 Wiley Periodicals, Inc. Electron Comm Jpn Pt 3, 85(8): 11–21, 2002; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjc.10004