Design and fabrication of a wideband 56-to 63-GHz monolithic power amplifier with very high power-added efficiency

This paper describes the design, fabrication, and measurement of a wideband 60 GHz monolithic microwave integrated circuit (MMIC) power amplifier that has demonstrated via on-wafer continuous wave (CW) measurement a record 43% power-added efficiency (PAE) at an associated output power of 224 mW and 7.5 dB of power gain. At a higher drain bias of 3.5 V, the CW output power increased to 250 mW with 38.5% PAE. Additional performance improvement is expected when the MMICs are tested on-carrier with proper heat sinking. These state-of-the-art first-pass design results can be attributed to: 1) the use of a fully selective gate recess etch 0.12-mu m InP HEMT process fabricated on 2-mm-thick 3-in diameter InP substrates with slot via holes; 2) a design based on a novel on-wafer load-pull measurement technique; and 3) an accurate large-signal nonlinear model for InP HEMTs. In order to reach the low cost required for mass production, the same MMIC design was fabricated on an InP metamorphic HEMT (MHEMT) process. The MHEMT version of the MMIC demonstrated 41.5% PAE, with an associated output power of 183 mW (305 mW/mm) and 6.9 dB of power at 60 GHz when measured CW on-wafer. These InP HEMT and MHEMT results are, to our knowledge, the highest PAE and power bandwidth ever reported at V-band.