220 GHz wideband distributed active power combiner

This paper presents an active power combiner for UWB applications implemented in a 0.13 μm SiGe BiCMOS technology (f_t = 300 GHz, f_max = 500 GHz). The circuit is based on distributed architectures: two travelling wave amplifiers sharing the output line are used for the signal combining, whereas a cascade single-stage distributed amplifier ensures high gains for the combining paths. The 3 dB bandwidth of operation is demonstrated from 1 to 170 GHz, while the 6 dB upper frequency exceeds 220 GHz. Good performances in terms of group delay variation are also reported. Over the 3 dB bandwidth the group delay variation is less than 10 ps, and over the 6 dB one it is less than 15 ps. The signal amplification in each path of the combiner is 20 dB from 1 to 170 GHz and it decreases to 15 dB at 220 GHz. Independent bias networks for each combining path enable also selective gain tuning capabilities: a gain tuning range of 20 dB is demonstrated. The system requires a chip area of 0.57 mm² and 203 mW of DC power. Compared against the state of the art, the presented circuit offers the widest bandwidth as well as the highest combining path gain.