Abstract: This paper describes the design, fabrication and performance of a monolithic 30GHz VCO.This MMIC chip utilizes the PHEMT technology.A negative resistance common-source feedback configuration is utilized in the design.The modified-Materka FET model parameters are extracted from the small signal S-parameters and dc I-V parameters.The varactor diode is implemented by common-source-drain-FET.The capacitance is controlled by the gate voltage.The circuit measurements show a frequency tuning bandwidth of about 150MHz at ～30.12GHz center frequency and an output power up to 12.5dBm.The measurements are corresponding with the design.

Key words: VCO,  PHEMT,  MATRK-model,  harmonic-balance-analysis