Coupled Embedding Networks for 7-dB Gain-per-Stage at 130-140 GHz in a 20-dBm Gallium Nitride Power Amplifier

Abstract

We propose a coupled embedding network (CEN) as a portable, robust design technique to simultaneously introduce gain boosting and loadline matching in millimeter-wave power (mm-wave) amplifiers (PAs). The approach uses directional couplers as an abstraction for the embedding network and produces straightforward design equations to achieve optimal input-stability margins for any specified gain. We demonstrate the design process and implementation using a 40-nm Gallium Nitride (GaN) process technology through simulated and measured performance of the PA with and without the embedding network. The output power is greater than 20 dBm and remains above 18 dBm over an 8 GHz bandwidth. Peak power added efficiency (PAE) is 6.5%. The 3-stage PA achieves 21 dB of gain at 137 GHz offering 7.1-dB gain per device. The measured gain is 8 dB higher than the common-emitter design with the same number of stages. To our knowledge, this is the highest gain per stage for a GaN PA in D-band.