I. Introduction
Millimeter-wave MMIC power amplifiers are critical components in mm-wave wireless data networks, automotive and military radars. HEMTs with electron beam written gate fingers have until recently exhibited higher mm-wave gains than HBTs, and have dominated W-band applications. By scaling HBTs to submicron junction dimensions and reducing the impact of extrinsic parasitic capacitance [2], very high cutoff frequencies can be obtained which make HBT amplifiers at W-band feasible. Double heterojunction bipolar transistor (DHBT) technology has the advantage of providing improved linearity and efficiency over pHEMT devices[1]. However, DHBT power amplifiers still exhibit lower output power than pHEMT amplifiers at W-band frequency [3]–[9], So in practice a drive amplifier is often used before the power amplifier, yet it increases the area and cost.