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Adaptive Beamforming of ESPAR Antenna--Unconventional Approach
Blagovest SHISHKOV Jun CHENG Takashi OHIRA
IEICE TRANSACTIONS on Electronics
Publication Date: 2002/03/01
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Issue on Signals, Systems and Electronics Technology)
Category: Digital Transmission
ESPAR antenna, adaptive beamforming, stochastic approximation, interference reduction, convergence, gradient noise, Hessian,
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The electronically steerable passive array radiator (ESPAR) antenna performs analog aerial beamforming that has only a single-port output and none of the signals on its passive elements can be observed. This fact and one that is more important--the highly nonlinear dependence of the output of the antenna from adjustable reactances--makes the problem substantially new and not resolvable by means of conventional adaptive array beamforming techniques. A novel approach based on stochastic approximation theory is proposed for the adaptive beamforming of the ESPAR antenna as a nonlinear spatial filter by variable parameters, thus forming both beam and nulls. Our theoretic study, simulation results and performance analysis show that the ESPAR antenna can be controlled effectively, has strong potential for use in mobile terminals and seems to be very perspective.