High-Power and High-Efficiency Millimeter-Wave Harmonic Oscillator Design, Exploiting Harmonic Positive Feedback in CMOS

Based on time-variant behavior of metal-oxide-semiconductor field-effect transistors in large-signal operations, harmonic translations and their mutual effects are analyzed. Large amplitudes at terminal voltages of these transistors push them into different regions of operation. In this paper, harmonic translations are derived as a result of such changes in operation region of transistors. Operation in triode region for a portion of oscillation cycle results in iterative harmonic translations between fundamental frequency and second harmonic. They boost each other constructively for significantly stronger oscillation, more second harmonic output power, and enhanced dc-to-RF efficiency. Based on this analysis, a 215-GHz signal source, implemented in a TSMC 65-nm CMOS LP is presented. The proposed oscillator achieves a maximum output power of 5.6 dBm and a dc-to-RF efficiency of 4.6%. The measured phase noise is -94.6 dBc/Hz at 1-MHz offset. The proposed oscillator occupies only 0.08 mm2of chip area.