Negative differential resistance based voltage-controlled oscillator for VHF band

This paper presents a novel sinusoidal negative differential resistance (NDR) voltage-controlled oscillator (VCO) for VHF band. The VCO circuit is based on a junction field effect transistor (JFET) in combination with a current mirror (CM). Mathematical model of the proposed VCO is described and the start-up conditions are determined. The designed VCO covers the frequency band between 139.8 and 256.2 MHz. It has a phase noise of -111.1 dBc/Hz at 10 kHz offset from carrier, consumes only 6.2mW, suppresses harmonics to better than -31dBc, and achieves a very good figure of merit (FOM) performance of -190 dBc/Hz. The implemented VHF VCO generates low-noise low-distortion signal confirming simulation results.