Nonlinear and Load-Pulling Effects in an Octave-Bandwidth Transmit Array

This article presents the design and nonlinear analysis of an octave-bandwidth transmit in-phase power combiner feed network. The goal is to evaluate the effect of nonlinearities on the in-phase spatial power combiner figures of merit (FoMs), namely effective isotropically radiated power (EIRP), overall efficiency, and linearity across a wide bandwidth and as a function of active antenna impedance and power amplifier (PA) supply voltage (
$V_{\textrm {DD}}$
). The analysis is showcased on a 6–12 GHz four-element array implemented with electrically small flared horns fed with microstrip-to ridge waveguide transitions, 2-W commercial gallium nitride (GaN) monolithic microwave integrated circuit (MMIC) amplifiers, and an in-phase Wilkinson power splitter. Over-the-air (OTA) measurements show an EIRP of 50 dBm over the octave bandwidth. Adjacent channel power ratio (ACPR) variation over frequency, power, and supply voltage is also measured through OTA and shows a variation of 10 dB over the considered variables.