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This letter presents a signal generation circuit that combines a wide tuning range voltage controlled oscillator (VCO) and a frequency doubler. The VCO provides two differential outputs with different power levels. A push-push frequency doubler is designed and cascaded to the high power output of the VCO, while the low power output is reserved to drive a frequency divider in a PLL. The VCO can be tuned from 33 to 43 GHz, with around 0 dBm output power at the low power output. Simultaneously, signal generation from 66 to 86 GHz is achieved at the doubler output, with a maximum output power of -1.1 dBm at 74 GHz (-2.5 dBm at 81 GHz). The measured phase noise at the VCO output and the doubler output are -91 dBc/Hz and -83 dBc/Hz at 1 MHz offset (-112 dBc/Hz and -106 dBc/Hz at 10 MHz offset), respectively. The circuit is realized in a 0.8 SiGe heterojunction bipolar transistor process, with fT/fmax of 80/90 GHz. The VCO consumes 81 mA current while the doubler consumes an extra 17 mA from a 4 V supply. The circuit demonstrates the possibility of wide-band signal generation up to fmax with sufficient output power (e.g. to drive a mixer) in a conservatively scaled, low-cost process.
Date of Publication: Oct. 2010