A Class-C self-mixing-VCO architecture with high tuning-range and low phase-noise for mm-wave applications

Achieving high tuning-range and low phase-noise simultaneously in mm-wave voltage-controlled oscillators (VCO) has been a severe design challenge. Our architecture, referred herein as a self-mixing VCO (SMV), utilizes a Class-C push-push VCO topology to generate the first (f0) and second harmonics (2f0) and then mixes them together to obtain the desired third harmonic (3f0) component. Compared to a fundamental-mode VCO operating at 3f0 in mm-wave band, the SMV architecture achieves superior frequency tuning range (FTR) and phase-noise (PN) performance. A Class-C topology enhances the second-harmonic content to improve mixing efficiency, decreases parasitic capacitance and reduces phase noise. A 52.8-to-62.5 GHz SMV prototype is designed and implemented in a 0.13-µm CMOS process. Measurement results show an FTR of 16.8% together with a PN of −100.57 dBc/Hz at 1 MHz offset - resulting in an FTR-inclusive figure-of-merit (FOMT) of −190.85 dBc/Hz while consuming 7.6 mW from a 1.2 V supply voltage.