A SiGe Oscillator with Second Harmonic Control Technique for mmWave Applications

This paper presents a novel Colpitts-based oscillator employing SiGe:C 130 nm bipolar devices provided by IHP foundry, featuring a transit frequency of 350 GHz and a maximum oscillation frequency of 450 GHz. Designed for mmWave and subterahertz applications, the oscillator operates at a fundamental frequency of 220 GHz, delivering an output power of 4 dBm. Simultaneously, it generates a second harmonic signal at 440 GHz with an output power of $-\mathbf{4. 2 ~ d B m}$, enabled by an innovative second harmonic regulation technique that enhances harmonic extraction and efficiency. A dedicated Second Harmonic Optimizer ($\mathbf{2 H}$-OPT) is integrated into the design to efficiently capture and amplify the second harmonic generated by device nonlinearity. Simulation results confirm that the oscillator maintains reliable performance, with high output power, a phase noise of $-89 \mathrm{dBc} / \mathrm{Hz}$ at a 10 MHz offset, and stable frequency operation. These attributes make the proposed design an attractive candidate for high-frequency applications in communications, sensing, and imaging.