Design of a 60 GHz GaAs Enhancement-Mode pHEMT Power Amplifier MMIC with 28 dBm Output Power

Abstract

A 60 GHz power amplifier (PA) monolithic microwave integrated circuit (MMIC) with +28 dBm output power is designed in an enhancement-mode 0.15 μm GaAs pseudomorphic high-electron-mobility transistor (pHEMT) technology. A two-stage topology and a four-way power combining technique are adopted to achieve a high power gain, high output power, and high linearity. Transistor-level circuit and layout designs are developed, and the circuit performances are verified through three-dimensional electromagnetic simulations. The designed PA MMIC exhibits a saturated output power of +28.4 dBm, output-referred 1-dB gain compression point of +28 dBm, power gain of +8.1 dB, and power added efficiency of 29.3 %. S-parameter simulations show that the small-signal gain is +8.1 dB, and the operating bandwidth is between 55.7 and 63.1 GHz, with a fractional bandwidth of 12.3 %. The supply voltages are 4 V for the drain and 0.6 V for the gate. The positive-only supply voltages resulting from the enhancement-mode pHEMT simplify the supply voltage network compared with the conventional depletion-mode pHEMT design. The layout die size of the PA MMIC is 1.99×1.62 mm 2 , and the power density performance of 214 mW/mm 2 is satisfactory.