A Low Phase Noise VCO for 60 GHz Radar Applications with a Direct Transformer-Based Fourth Harmonic Extraction in 28 nm CMOS

In this paper we present a simple generation of a continuously tunable local oscillator (LO) signal at 56.1-to-65.6GHz. It is realized by a voltage-controlled oscillator (VCO) using transformer-based fourth harmonic (H4) extraction directly from the core. We show in measurement that the direct H4 extraction approach is not adding any excess phase noise (PN) beyond the expected 20 · log(4) degradation due to the frequency scaling by four. The proposed VCO is realized in 28nm bulk CMOS technology and achieves best measured phase noise of −73.4dBc/Hz at 100kHz offset and −99.8dBc/Hz at 1MHz offset from a 56.1GHz carrier with a continuous frequency tuning range (FTR) of 15.6%. The DC power including VCO and buffer is 11.7mW. The VCO achieves a competitive FOMT of −188dBc/Hz.