A V-band balanced two-stage power amplifier MMICs with Lange couplers is demonstrated using 0.15 µm GaAs pHEMT technology in this paper. A CPWG-MS-CPWG topology with via holes at the transistors as the transition between coplanar waveguide with backside ground (CPWG) and microstrip (MS) is employed for the two-stage amplifier. CPWG is applied to realize the flip-chip transition interface for both input and output ports of the amplifier and interstage MS matching has the advantage of small size. The structure parameters of the CPWG Lange coupler and matching network are designed and optimized for power combining. Finally, a 60-GHz balanced two-stage power amplifier using a CPWG-MS-CPWG structure delivers the small signal gain of 18 dB, OP 1dB of 12 dBm and P sat of 15 dBm.
