Improving a Ka-Band Integrated Balanced Power Amplifier Performance by Compensating Quadrature Hybrid Mismatch Effects

This article presents an integrated quadrature balanced power amplifier (PA) operating at a 26-GHz frequency range and techniques to mitigate the frequency-dependent amplitude response of quadrature hybrids used in the balanced amplifier design. The overall structure consists of two stacked pseudo-differential PAs and transformer-based quadrature hybrids designed with 22-nm CMOS FDSOI. Two techniques to compensate frequency-dependent amplitude response of the quadrature hybrid when operating away from the center frequency are proposed. The first one involves a dual input drive and the second one involves asymmetric biasing. With distortion contribution analysis, it is shown that asymmetric biasing compensates quadrature hybrid asymmetry but also produces mutually compensating third-order nonlinearity, resulting in improved linearity. Measurements with continuous wave (CW) and high dynamic range fifth generation (5G) modulated signal demonstrate that the described techniques improve output power that can be reached within the linearity specifications when operating away from the center frequency.