A 310–340-GHz Coupled-Line Voltage-Controlled Oscillator Based on 0.25- $\mu$ m InP HBT Technology

A THz voltage-controlled oscillator (VCO) has been developed in this work based on a 0.25- μm InP heterojunction bipolar transistor (HBT) technology. The cross-coupled push-push oscillator adopted a novel coupled-line topology, in which the DC blocking capacitors and the load inductance are replaced by a pair of coupled-lines to improve the oscillation frequency and reduce the circuit area. Also, a base bias tuning was employed for effective oscillation frequency tuning. The circuit exhibited the voltage tuning from 309.5 GHz to 339.5 GHz, leading to a tuning range of 30 GHz. The maximum output power was -6.5 dBm at 334 GHz, achieved with a dc power consumption of 13.5 mW. Measured phase noise was -86.55 at 10-MHz offset. The circuit occupies only 0.014 mm ² excluding the probing pads.