A Q-Band MHEMT 100-mW MMIC Power Amplifier with 46 % Power-Added Efficiency

A Q-band MMIC power amplifier has been designed, processed, and measured with first pass success. Design parameters include 20 dBm power, 25 dB gain, 40 % PAE, input return loss of 10 dB and output return loss of 6 dB across 43.5 to 45.5 GHz. The MMIC design is based on the BAE Systems 0.1 mu m MHEMT device, which has high gain and excellent PAE. The two-stage amplifier uses a 2-finger, 75 mu m unit gate width, 0.1 pin gate length MHEMT device for the first stage and two 4-finger, 75 mu m unit gate width, 0.1 mu m gate length MHEMT devices for the output stage. Complete stabilization for both the even and odd mode is provided using feedback and resistors in critical locations of the circuit. The first stage is optimized for gain while the output stage is optimized for power and power-added efficiency (PAE). The complete MMIC amplifier measures 3.5 mm x 1.7 mm complete with dc blocks and dc biasing elements. Measured performance includes record high PAE of 46 % at 44.5 GHz, 24 dB small-signal gain, 1 dB compressed power of 18 dBm, and 3-dB compressed power of 20.5 dBm across the 43.5 to 45.5 GHz frequency band.