Port and Radiation Pattern Decoupling of Dielectric Resonator Antennas

Abstract

A new decoupling method is proposed in this article, which simultaneously realizes port and radiation pattern decoupling, namely, high isolation and undistorted radiation patterns, respectively. The proposed decoupling method shows its effectiveness in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1\times 2$ </tex-math></inline-formula> dielectric resonator (DR) antennas (DRAs) even with zero spacing. Conformal strips are attached to the sidewall of the DRs and parallel to the E-plane of the DRAs. Coupled from the resonant DR, the conformal strips can generate an induced current, thus forming an induced field inside the DR. It can be noted that, inside the two DRs, the DR resonant field and the strip induced field are antiphase and in-phase, respectively. Tuning the conformal strips can change the amplitude ratio and phase difference between the resonant and induced fields, which can be used to cancel the fields inside the DR based on the superposition principle. When one DR is excited, the field inside the other DR can be very weak. The DRs can then work at their fundamental TE <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\delta 11}$ </tex-math></inline-formula> modes independently. Therefore, their radiation patterns are not distorted together with high port isolation. A new indicator, energy storage proportion (ESP), is proposed to evaluate the decoupling effect. It can be found that, when the ESP gets close to 1, the radiation patterns will be restored together with high isolation. To verify the idea, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1\times 2$ </tex-math></inline-formula> DRAs are designed, fabricated, and measured. A reasonable agreement can be observed between the measured and simulated results for both H- and E-plane decoupled cases. All the measured overlapping impedance bandwidths are larger than 6%, the envelope correlation coefficients are lower than 0.059, and the isolations are higher than 20 dB. It should be highlighted that all the radiation patterns in this article have been restored, useful for practical applications using multiple-input multiple-output techniques.