Ka-band Three-terminal Devices, Voltage-controlled Oscillator

Millimeter-wave oscillator is one of key components for radar, electronic-war, communication and measurement etc. millimeter-wave systems, which have been regarded as the core of the millimeter-wave system. With the development of millimeter-wave technology and demand of practical engineering application, there is great demand for oscillator in terms of stability, phase noise, output power, and high dc-to-radio-frequency (RF) conversion efficiency.Traditionally, millimeter-wave oscillators have been designed using two-port devices such as BVIPATT and Guun. With the development and application of three-terminal devices, a millimeter-wave three-terminal device oscillator has some advantages over a two-terminal oscillator, for instance, operation frequency band, efficiency, stability and integrity. Especially, for PHEMT (pseudomorphic high electron-mobility transistors) oscillator and HBT (heterojunction biplor transistors) oscillator, there is lower noise and better integrity, operate in wider dynamic range and higher frequency band. So, it has great potential for application.A PHEMT oscillator at Ka frequency band is developed in this paper. The integrated microstrip circuit is used, the low noise PHEMT is chosen as the active device. The large signal and small signal equivalent circuit of the PHEMT have been presented, the parameters of the equivalent circuits have been extracted from the small-signal S-parameters and dc I-V characteristics using Levenberg-Marquart method. The bond wire, the via hole and the uncontinuity of the microstrip's effect have been taken into account .At first, a satisfactory circuit topology and DC bias condition have been determined early in the design procedure according to electrical requirement. The values of the variables and the tuning location of the varactor have been found using small signal techniques through small signal parameter analysis. Harmonic-balance method and numerical device-line measurement have been adopted to carry out large signal analysis for the accurate design of the oscillator and its associated parameters, resulting in reliable performance predictions. More than 5.5 dBm output power, more than 300 MHZ voltage-controlling range and 4.2% linearity have been achieved in Ka-band. Finally some experiment phenomenon is analyzed.