Electronically steerable parasitic array radiator antenna

Abstract

SUMMARYThe electronically steerable parasitic array radiator antenna consists of one feed radiating element and parasitic radiating elements placed in the near field of the active radiator. A beam is formed due to spatial electromagnetic field coupling among radiating elements. The radiation pattern is electronically controlled by means of the variable capacitance devices (varactors) loading the parasitic elements. Unlike a conventional phased array, only one transmitter and receiver are needed for system configuration. Therefore, adaptive beamforming of low dissipation power and low fabrication cost can be achieved. On the other hand, there is only one output port to observe the signal and the weights can be controlled indirectly via reactors instead of direct control. In addition, due to interelement mutual coupling and the parasitic element being directly connected to the reactive device, the linear adaptive array theory developed to date cannot be applied straightforward. In this paper, the configuration of this antenna, its operating principle and formulation, and its measurement method, control scheme, and applications to signal processing are presented. We describe a mathematical model to simulate the radio frequency behavior of the antenna, the equivalent weight vector used for formulation of the characteristics, the admittance matrix including varactors, the effective element length, the equivalent steering vector method, the method for effectively extending the variable range of the capacitance of the varactor, the reactance circuit to cancel nonlinear distortions, the method for calibration of varactors and radiation pattern by measurement of near field of the radiating element, the learning criteria used to control radiation patterns autonomously in adaptation to the electromagnetic environment, the reactance optimization algorithm, the concept of the reactance domain signal processing and the direction of arrival estimation based on such a process, and diversity reception and spatial correlation.

Performance Evaluation of Beamspace MIMO Systems with Channel Estimation in Realistic Environments

“…For the MMSE estimator, the correlation matrix was set according to R hh = 1/M 2 I M . The simulation results (lines) and the theoretic results (markers) from (15) and (20) were identical, which also means that 'B2' and ideally rich scattering channels behave similarly in beamspace, as far as the estimation procedure is concerned. MMSE and LS results are practically equal for high SNR, while for low SNR MMSE performs better.…”

Reactance-domain SSP MUSIC for DOA estimation of coherent waves with a seven-element circular ESPAR antenna

“…, and R xx (3) , then the MUSIC spectra P MUSIC (1) (φ), P MUSIC (2) (φ), and P MUSIC (3) (φ) are given by a sub (1) (φ), a sub (2) (φ), and a sub (3) (φ) are written as follows when Eq.…”

“…Then the correlation matrix R sub (1) of the subarray is represented by Similarly, the correlation matrices R xx (2) and R xx (3) that perform the F/B spatial smoothing in the center (SSP060) and on the right (SSP120) in Fig. 3 are rewritten to obtain Specifically, the row and column of R xx are rearranged in the same order to construct the correlation matrix of the subarrays.…”

Multi-antenna transmission using ESPAR with peak power constraints

“…Each additional antenna element requires an additional radio frequency (RF) chain, resulting in increased cost and complexity. Therefore, Electronically steerable parasitic array radiator (ESPAR) has been proposed to reduce the cost and physical size of multiple antenna devices [4] and provide multi-antenna functionality with a single RF chain. For an ESPAR antenna (EA), the mutual coupling is exploited to control the currents at all of the parasitics.…”