A bipolar MMIC frequency tripler

A concept for an MMIC frequency tripler using SiGe HBT´s is proposed and verified in this paper. The main circuit of this tripler consists of a differential-pair frequency doubler followed by a single-balanced mixer that multiplies the doubler output with the fundamental frequency input to generate the triple-frequency output. The single-balanced mixer is an emitter-coupled differential pair and because its output is taken differentially by a differential output stage, the even harmonics are highly suppressed. An on-chip LC notch filter is further introduced in the output stage to suppress the fundamental, leaving the triple frequency dominating the output. The designed tripler can convert a 3-GHz input signal to a 9-GHz signal, with high suppressions of 28 dB, 22 dB, and 30 dB on the fundamental, the second, and 4th harmonics respectively.