Analysis and Electrical Modelling of Dual‐Port Antenna for Outphasing Power Combining

Abstract

This paper presents a two-port folded monopole antenna to be used as a signal combiner and radiating element in outphasing applications, enhancing the system efficiency by minimizing insertion loss. A simple but effective circuit model is proposed to estimate radiated and reflected power based on impedance values and the outphasing angle. The equivalent circuit was validated through analytical and experimental methods, using standard measurement techniques to obtain the Z-parameters. Additionally, a custom setup utilizing a software-defined radio platform was implemented to overcome the limitations of conventional instruments in measuring outphasing systems and to verify the proposed model. Measurements performed on a prototype resonating at 933 MHz demonstrated excellent linearity and spectral performance, achieving an adjacent channel power ratio (ACPR) below −45 dBc, superior to other combining antennas in the literature. Additionally, a reasonable error vector magnitude (EVM) of −32 dB was observed for broadband signals modulated with QPSK, 16-QAM, and 64-QAM.