A 248–262 GHz InP HBT VCO with Interesting Tuning Behavior

A fundamental-mode common-base voltage-controlled oscillator (VCO) based on 250-nm InP heterojunction bipolar transistor (HBT) technology is reported. The VCO, which employs varactors implemented by connecting the base and emitter of npn transistors as tuning components, shows a tuning range of 247.8-262.2 GHz. The output power is greater than 0 dBm over the entire tuning range, and dissipated dc power is around 85 mW. An unexpected tuning behavior was observed, which was shown to arise from the internal parasitic base inductance of the transistors used for varactors in this work.