Phase-Noise Improvement of GaAs pHEMT K-Band Voltage-Controlled Oscillator Using Tunable Field-Plate Voltage Technology

This letter presents a voltage-controlled oscillator (VCO) with low phase-noise performance by applying tunable field-plate (FP) voltage on 0.15-mum-gate-length GaAs pseudomorphic high-electron-mobility transistors (pHEMTs). In this letter, the FP metal between gate and drain terminals was connected to a single pad and was controlled by an extra voltage supplier (V
_FP
). Owing to the depth modulation of FP-induced depletion region at various FP voltages, the device flicker noise was also improved by applying negative V
_FP
. This technique is convenient to be applied in standard pHEMT fabrication and particularly attractive for reducing the phase noise of VCO design without extra power consumption. A tunable phase-noise inductor-capacitor feedback 21-GHz VCO was demonstrated. The measured phase noise of this novel design is -95 dBc/Hz at an offset frequency of 1 MHz, and this value can be improved to -99.6 dBc/Hz at V
_FP
of -5.5 V. The core dc-power consumption of this circuit is 30.8 mW.