Push-Push VCO with PN- and Pout-Enhanced Off-State Parallel FETs

We demonstrate a 77/154 GHz push-push voltage controlled oscillator (VCO) with tail double-frequency ($f_{02}=2 f_{01}$) output in 90 nm CMOS. Off-state parallel transistors (OSTs) are included in the cross-coupled transistors (CCTs) of the VCO to enhance the nonlinearity-based second-harmonic frequency tone. This leads to enhancement of phase noise (PN) and output power $\left(P_{out}\right)$ of the VCO. The VCO consumes 14.4 mW and achieves decent results. For example, at the fundamental (f
01
) port, the VCO achieves single-ended Pout of -6.8 dBm, tuning range of 7677.6 GHz, and a PN of -109.2 dBc / Hz at 10 MHz offset from the carrier. The corresponding FOM is -175.41 dBc / Hz. Moreover, a 70 / 140 GHz push-push VCO with head f
02
output is also implemented for comparison. The VCO consumes 11.8 mW and achieves single-ended P
out
of -3.6 dBm, tuning range of 66.3-70.2 GHz, and a PN of -113.8 dBc / Hz at 10 MHz offset at the fundamental port. The corresponding FOM is -180.01 dBc/Hz. To the authors’ knowledge, the PN and FOM of the VCO are one of the best results ever reported for a V-band CMOS VCO.