A Noise Circulating Oscillator

This paper presents a noise circulating crosscoupled voltage-controlled oscillator (VCO) topology with a transformer-based tank. The introduced noise circulating active core greatly suppresses the effective noise power from the active devices while offering the same amount of negative resistance compared to conventional cross-coupled VCO topologies. The mechanism of noise circulation is investigated with theoretical analysis and further verified by simulation. Due to the broadband nature of the noise circulating technique, the resulting VCO phase noise in both 1/f
²
and 1/f
³
regions is greatly improved over a wide frequency tuning range. A prototype VCO at 2.35 GHz is implemented in a standard 130-nm bulk CMOS process with 0.36-mm
²
core area. It draws 2.15 mA from a 1.2-V supply. The measured figure-of-merit (FoM) is 193.1/195.0/195.6 dBc/Hz at 100k/1M/10MHz offsets with a 1/f
³
phase noise corner of only 50 kHz. The VCO design consistently achieves 192.8 dBc/Hz FoM at 100k/1M/10MHz offsets and <;60 kHz 1/f
³
phase noise corner over its entire 18.6% frequency tuning range (2.05-2.47 GHz). It also exhibits low supply frequency pushing of -25 and -13 MHz/V at the highest and lowest frequencies, respectively.