A Low-Phase-Noise Voltage Controlled Oscillator with Tuning Bandwidth of 25% Using Stacked-FET Approaches for Enhanced Output Power

This paper describes a monolithic microwave integrated circuit (MMIC) GaAs pseudomorphic high-electron-mobility transistor (pHEMT) voltage controlled oscillator (VCO) circuits using the approaches of stacked filed-effect transistor (FET) approach. The stacked structure oscillator has high output power, high drain efficiency, and stable oscillation performance, and the load impedance can be changed to improve the oscillator's bandwidth. For a bias of $\mathrm{V}_{\mathrm{d}}/\mathrm{I}_{\mathrm{d}}=4.5\ \mathrm{V}/8.6\ \text{mA}$ , the VCO's frequency ranges from 35 to 45 GHz, with a tuning bandwidth of 25%, an output power greater than 11.7 dBm, and a drain efficiency of 38.2%. At 1-MHz offset frequency, the VCO exhibits phase noise of −103 dBc/Hz. At the same time, we investigate the relationship between bias voltage and phase noise via simulation.