Design and Analysis of a 55–71-GHz Compact and Broadband Distributed Active Transformer Power Amplifier in 90-nm CMOS Process

A 55–71-GHz fully integrated power amplifier (PA) using a distributed active transformer (DAT) is implemented in 90-nm RF/MS CMOS technology. The DAT combiner, featuring efficient power combination and direct impedance transformation, is suitable for millimeter-wave (MMW) PA design. Systematic design procedures including an impedance allocation plan, a compensation line, and a gain boosting technique are presented for the MMW DAT PA. The monolithic microwave integrated circuit (MMIC) performs a high and flat small-signal gain of ${hbox{26}} pm {hbox{1.5}}~{hbox{dB}}$ from 55 to 71 GHz, which covers a full band for 60-GHz wireless personal area network applications. Using cascode devices and a DAT four-way power combination, the CMOS PA delivers 14.5- and 18-dBm saturated output power with 10.2% and 12.2% power-added efficiency under 1.8- and 3-V supply voltage, respectively, at 60 GHz. The maximum linear output power ( $ P _{1~{rm dB}} $) is 14.5 dBm. To the best of our knowledge, the MMIC is the first demonstration of a $V$-band CMOS PA using a DAT combining scheme with highest linear output power among the reported 60-GHz CMOS PAs to date.