Millimeter-Wave Series Power Combining Using Sub-Quarter-Wavelength Baluns Hyun-chul Park, Student Member , IEEE, Saeid Daneshgar, Zach Grif fith, Senior Member , IEEE,M i g u e l U r t e a g a

Abstract

We present a new millimeter-wave power-combining technique using transmission-line baluns which both connect tran- sistor outputs in series and inductively tune the transistor output capacitances. The baluns are much shorter than a quarter-wave- length , hence are more compact and have l ess insertion loss than a balun. We introduce one topology providing an even number of series connections, including 2:1 and 4:1, and a second topology providing either an even or odd num ber of series connec- tions. We then analyze segmented transformer power-combiners as a set of multi-conductor transmission-lines, and explore the rela- tionship between transformer and trans mission-line balun power- combiners. We demonstrate the technique with 2:1 and 4:1 series- connected designs implemented in a 0.25 mI n PH B Tp r o c e s s .A t 86 GHz, a single-stage power ampli fie r( P A )u s i n gt h e2 : 1b a l u n s exhibits 30.4% peak PAE, 20.37 dBm output power and 23 GHz 3-dB bandwidth from a 448 816 m die. A two-stage PA using the 2:1 baluns exhibits 30.2% PAE, and 23.14 dBm from an 824 816 m die. At 81 GHz, a two-stage PA with 4:1 series output power-combining exhibits 23.4% PAE, and 26.7 dBm (470 mW) from a 1,080 980 m die.