Wide frequency-tunable resonant tunnelling diode terahertz oscillators using varactor diodes
A resonant tunnelling diode terahertz voltage-controlled oscillator integrated with a varactor diode (RTD VCO) for a wide tuning range was proposed and fabricated. In single RTD VCO, a tuning range of 120 GHz of the centre frequency of 640 GHz was achieved by a good combination of the RTD and varactor capacitances. A multi-element array of RTD VCOs was fabricated to increase the tuning range. A very wide frequency tuning of 320 GHz (580–900 GHz) was achieved with a four-element RTD VCO array.