A Ka-band Power Amplifier with On-chip Power Detector in 0.15 μm GaAs pHEMT Technology

A three stage 28 GHz power amplifier (PA) with on-chip power detector is presented. A 0.15 mu m GaAs pHEMT process is used to implement the power amplifier. The chip size is 2.09 mm x 1.28 mm including the on-chip power detector and I/O pads. The PA die chip is attached on a commercial open cavity QFN package to evaluate the performances in surface mount use. The on-chip power detector is designed with directional coupler using diode rectifier to monitor available output power from the PA. The detector output voltage is very coherent to the output power in the operation frequency from 26.6 GHz to 29.2 GHz, where the deviation of the detector output voltage is lower than +/- 3.7 % up to 27.4 dBm output power. The output P1dB is over than 26.9 dBm, saturated output power is over 27.4 dBm, and the PAEmax is 25 similar to 30 % across the operation frequency.