Impact of Amplitude and Phase Imbalance on Dual Differential Fed Patch Antenna With High Isolation

Abstract

In this paper, the impact of amplitude and phase imbalance on a proposed dual differential fed patch antenna is analyzed in the context of system effective reflection coefficient and axial ratio (AR). A single square patch with four ports is used as a solo radiating element and provides absolute symmetry at radiating. An in-depth analysis will be presented to understand the impact of external RF chain components on the performance of the proposed antenna. When fully differential excitations and perfect symmetry can be achieved, all six polarization states exhibit identical system effective reflection coefficients with close to ideal AR for CP. When phase imbalance and amplitude imbalance only exist in between the two differential pairs, the antenna system matching performance is found to be unchanged. In the presence of the feed network, circular polarization (CP) achieves a measured maximum AR of 0.49dB along the antenna pointing angle, while linear polarization (LP) has a measured maximum cross polarization of −30dB. This work monitors the beamwidth over which the AR can be kept below 1dB (BW-AR−1dB). Based on the optimization of phase imbalance, a novel BW-AR−1dB enhancement technique is introduced. Compared to the case with better AR at the main beam location, an improvement of 14. beamwidth is measured without significant degradation of AR. Isolation better than 40dB across an operating frequency of 9.27 – 9.4 GHz has been experimentally demonstrated for the proposed dual differential fed technique. The resulting antenna is compact and low profile which is an appealing candidate for phased array applications.