An X-Band Low Noise InP-HBT VCO with Separate Optimized Varactor Layers

A Colpitts 8 GHz InP heterojunction bipolar transistor (HBT) monolithic voltage controlled oscillator (VCO) with separate varactor layers is presented. The separate and optimized varactor layers were grown underneath the transistor layers. A broad tuning range of 12%, low phase noise of -94 dBc/Hz at 100 KHz offset frequency, and high linearity of 2% were demonstrated. The VCO power consumption was 30 mW while providing -3 dBm output power. The over all chip size is 1.3times0.8 mm².