A Compact Self-similar Power Combining Topology

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 1.49 µm 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 P_(sat) 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 P_(sat) reported at 77 GHz in CMOS with a sub 1V quiescent V_(ds)