A Broadband G-Band Frequency Doubler in 130-nm SiGe Technology

This paper presents a broadband G-band frequency doubler implemented in 130-nm SiGe BiCMOS technology. The design features an active balun integrated with a stacked doubler-and-amplification (D&A) stage. The balun converts a single-ended input into differential fundamental signals while generating common-mode second-harmonic signals on the noninverting and inverting paths. The D&A stage, comprising three stacked common-base transistor pairs, concurrently doubles the frequency of the differential fundamental component to generate the common-mode second harmonic and amplifies the common-mode second-harmonic component from the active balun. Consequently, the stacked topology enhances output power while improving fundamental rejection. Measurement results demonstrate a peak output power of 6.3 dBm at 180 GHz, a 3-dB bandwidth of 67 GHz (145–212 GHz, corresponding to a fractional bandwidth of 37.5%), and a peak efficiency of 2.2%. The measured fundamental rejection is greater than 20 dBc. The circuit occupies a total chip area of 0.56 mm² (core: 0.072 mm²).