The Design of 40 GHz Active Power Splitter

Abstract

Based on the idea of distributed amplifier, a wideband active power divider is designed using 90 nm CMOS process to provide positive gain and superb isolation between its two output ports from quasi-DC up to 40 GHz. Compared with our previously demonstrated 20 GHz one, the requirement of good input matching over the whole bandwidth poses an even severe constraint in the development of this 40 GHz active power splitter, as the tradeoff between gain and bandwidth becomes more intricate now. Mutual-coupling inductors are therefore adopted in the circuit's artificial transmission line to improve both the input return loss and allow the use of larger transistors in the gain stage. The fabricated circuit exhibits good input and output matching and has better than 10 dB output-port isolation across the whole band, with the bias of 1.8 V and 190 mA. Related circuit theories and mathematics will also be presented in this paper.