A Compact Self-similar Power Combining Topology

K. Sengupta and A. Hajimiri

A compact, modular 16-way combiner is presented which is based on a self-similar combiner topology. The combiner achieves a simulated passive efficiency of 38% at 77 GHz in a standard 90nm process with 1.49jlm thick AI top metal. A 77 GHz power amplifier is built based on the combiner, combining the output power of 16 stages to achieve a Psat of 11.4dBm, small signal gain of 9.4dB, and a 3dB bandwidth of more than 11 GHz on a 0.7V supply, with the optimal MAG for the technology being approximately 5dB at 77 GHz. The power amplifier is unconditionally stable with the K factor exceeding 3.8 between 50-90 GHz. The entire architecture is based on a modular power splitting and combining network that makes the design flexible and scalable. To the best of the authors’ knowledge, this is the highest Psat reported at 77 GHz in CMOS with a sub IV quiescent Vds.