A low phase-noise GaAs FET/BJT voltage-controlled oscillator for microwave applications

摘要

This paper presents a novel negative differential resistance (NDR) voltage-controlled oscillator (VCO) for microwave applications. The VCO circuit comprises a GaAs field-effect transistor (FET) and a bipolar junction transistor (BJT) current mirror. The VCO has an N-type I–V characteristic with controllable slope of the NDR region. The mathematical models of the I–V characteristic are developed using three the most frequently used models of GaAs FET drain current: Curtice, Statz and TOM. The designed VCO uses an n-channel GaAs metal semiconductor field effect transistor (MESFET) NE722S01 and four p-n-p bipolar junction transistors (BJTs) MRFC521. The VCO covers a frequency band between 1.233 GHz and 1.679 GHz with maximum in-band phase-noise of −146 dBc/Hz at 100-kHz offset over the tuning range. Power consumption of the VCO core is 53 mW from a 6.5 V supply. The implemented prototype of the proposed oscillator draws 4 mA from a 3.2V power supply and generates low-noise low-distortion signal.