Broadband Gm-boosted differential HBT doublers with transformer balun

Broadband monolithic InGaP HBT frequency doublers for K-Band application have been developed. The designs employ a Gm-boosted differential common-base configuration using either capacitive or transformer-based coupling between base and emitters. The design with cross-coupled capacitors presents a fundamental rejection better than 20 dB over a 100% 3dB bandwidth, extending from 6-18 GHz. The transformer-coupled design has about 15dB fundamental rejection over a slightly narrower bandwidth extending from 7-16 GHz. Both doublers have conversion gain peaking at more than -0.8dB and output power more than 13 dBm.