A 170-GHz 23.7% Tuning-Range CMOS Injection-Locked LO Generator With Third-Harmonic Enhancement

This article proposes a harmonic-extraction technique to enhance the amplitude and the phase noise of LC oscillators at the third-harmonic frequency. By leveraging this technique, a cascaded subterahertz (sub-THz) injection-locked local oscillator (LO) generator is proposed, which consists of a fundamental voltage-controlled oscillator (VCO) and a millimeter-wave (mm-wave) injection-locked frequency multiplier (ILFM). Fabricated in a 65-nm CMOS process, the VCO prototype concurrently generates two output signals: the first output at the fundamental frequency from 17.1 to 21.7 GHz with a 10-MHz-offset phase noise from -120.6 to -126 dBc/Hz, the second output at the third-harmonic frequency from 51.3 to 65.1 GHz with a 10-MHz-offset phase noise of -116.3 dBc/Hz, and the third-harmonic output power of -19.1 dBm. The VCO prototype consumes 1.4 mW from a 0.3-V supply, resulting in an FoM from -186 to -189.6 dBc/Hz at the fundamental frequency. The sub-THz injection-locked LO generator achieves a frequency tuning range of 23.7% from 153.9 to 195.3 GHz with a 10-MHz-offset phase noise of -106.8 dBc/Hz and the output power of -14.6 dBm, and consumes 8.4 mW, which corresponds to an FoM of -181.2 dBc/Hz and an ${\mathrm {FoM}}_{T}$ of -188.7 dBc/Hz at 153.9 GHz.