Designing and Verifying Power Amplifier Systems for Multiport Wideband Excitation

Wide bandgap materials like GaN show excellent power-efficiency at high frequency but suffers from dispersion effects from gate and drain-lag. Therefore, CW operation may be far from the response such devices show in dynamic wideband (WB) operation with high PAPR signals. WB operation needs to be characterized and properly modelled to enable first-pass success in the design process. This includes: (1) Large signal dispersion models that need to be verified by wideband (WB) load-pull simulations and measurements, (2) WB circuit simulations to give expected system performance at an early stage, and (3) coherent simulation of more complex dual-input-single-output (DISO) or parallel multi-cell amplifier hardware that can be designed and later tested and modelled under emulated real-life WB conditions with multi-port excitation. With such an approach, the complex electrical and thermal coupling in single and multi-amplifier systems can be identified and modelled under real WB multi-port conditions, already in the design process, prior to fabrication, expensive packaging and module assembly. For the verification we present a WB multi-port measurement system for mm-wave devices. It is developed for active WB load-pull of transistors for model verification, coherent multi-port WB excitation for DISO type PAs, and for MIMO and beam-forming hardware WB evaluation. In full operation, it will allow 16-port measurements up to 67GHz with a possible instantaneous bandwidth exceeding 5GHz.