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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.

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Mushroomlike photonic band gap (PBG) structures exhibit two band gap characteristics: surface-wave suppression and in-phase reflectivity. The fundamental electromagnetic properties and the relationship between the surface-wave suppression band gap and the plane-wave reflection phase band are investigated and clarified by a finite-element full-wave analysis. The results of the plane-wave bistatic reflection experiments on mushroomlike PBG plates in an anechoic chamber are in good agreement with those of numerical simulation, confirming the phenomenon of dual in-phase reflection, i.e., dual-resonant behavior, for a transverse magnetic polarization plane wave at oblique incidence on a mushroomlike PBG surface. A modified local resonance cavity cell model of a PBG structure is presented to provide insight into the physical mechanism of dual-resonant behavior.

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A concept of modulated scattering array antenna is proposed based on the modulated scattering technique. The array antenna consists of one antenna element and several modulated scattering elements (MSE). The configuration of the array antenna is very simple because only one branch of the front-end circuit is required. It is shown by experimental investigations that a 3-element modulated scattering array antenna composed of one λ/4 monopole and two λ/4 modulated scattering monopoles with λ/4 array spacing can provide diversity gain up to 8 dB diversity gain at 0.1% of the cumulative distribution function in Rayleigh fading environment. The array antenna is suitable to the mobile handset applications where the space and the cost are strictly limited because of its simple configuration.

Abstract:The diversity performance of the modurated scattering array antenna (MSAA) with various array spacing is measured in Rayleigh fading environment to investigate experimentally the relation between the array spacing and the diversity performance of the MSAA. A 2-element modulated scattering monopole array antenna with various array spacing which is supposed to be used for mobile handset applications is used as the measurement model. It is found that the diversity performance of the MSAA can be improved by reducing the array spacing as small as about 0.2 wavelength.