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Adaptive Control Algorithm of ESPAR Antenna Based on Stochastic Approximation Theory
Blagovest SHISHKOV Jun CHENG Takashi OHIRA
Publication
IEICE TRANSACTIONS on Communications
Vol.E85B
No.4
pp.802811 Publication Date: 2002/04/01 Online ISSN:
DOI: Print ISSN: 09168516 Type of Manuscript: PAPER Category: Antenna and Propagation Keyword: adaptive beamforming, ESPAR antenna, interference reduction, rate of convergence, stochastic approximation,
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Summary:
The electronically steerable passive array radiator (ESPAR) antenna is one kind of the parasitic elements based singleport output antennas with several variable reactances. It performs analog aerial beamforming and none of the signals on its passive elements can be observed. This fact and one that is more importantthe nonlinear dependence of the output of the antenna from adjustable reactancesmakes 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. Two learning rate schedule were examined about output SINR, stability, convergence, misadjustment, noise effect, bias term, etc., and the optimal one was proposed. Further development was traced. 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.

