GaAs HBT VCO Radiation Noise Research

The continuous development of personal mobile devices makes the rapid development of mobile communication, which attracts people more attention to wireless communications. The RF circuit is also attracted much attention. VCO is a major constituent of the PLL. It is an indispensable part of the generation frequency and it is widely used for satellite communication terminals, cellular phones, radar, military communications systems, missile guidance systems, a base station, a digital radio communication optical transmitter, optical multiplexer and other electronic systems. And the phase noise of VCO, as a necessary measure of its performance characteristics, is more and more attracted. As an important part of phase-locked loop, the phase noise of phase-locked loop is determined by the noise of VCO. So the study of the noise of VCO is improving the quality of phase-locked loop.Compared to common bipolar transistor, HBT is attracted much attention for its many unique advantages. And as a member heterojunction bipolar transistor, Compared to Si HBT, Ga As HBT has higher critical breakdown electric field, wider band gap, higher thermal conductivity, higher intrinsic temperature, higher electron saturation velocity. Especially Ga As HBT has better irradiation-hardened feature, therefore it is widely used and widely applicated such as aerospace, military, nuclear radiation.In this thesis, the phase noises before and after irradiation of Ga As HBT voltage-controlled oscillator circuit uses the simulation tool of ADS to simulate. The simulation of VCO circuit phase noise are not accurate enough, for the Ga As HBT small signal noise model in ADS are not accurate enough. In order to solve this problem,it is necessary to establish the precise Ga As HBT small signal noise model. Firstly, the method of analytical model is used to establish the accurate Ga As HBT small signal model. The influence of the base, emitter and the internal and external resistance of the collector, base-emitter junction capacitance, base-collector capacitance and the dynamic resistance to the small signal model is considered. A hierarchical extraction is used to extract parameters. Open and short construction is used to extract parasitic parameters. The method of open collector is used to extract outside parameters. The method of fractional extraction is used to extract intrinsic parameters. In this thesis, the thermal noise and shot noise is added on the basis of the small signal model.Phase noise is simulated by adding more precise Ga As HBT small signal noise model into the VCO circuit,. Firstly the phase noise of the VCO circuit is simulated.Then by adjusting the values of circuit component, the simulation results is consistent with experimental value. Finally the trends of circuit components is concluded. Analysis is made combined with a simple phase noise model of LC voltage controlled oscillator circuit. Through the experiment and analysis, Capacitance in circuit has larger change before and after irradiation. And it has the biggest impact on phase noise before and after irradiation. At the same time, the change of capacitance also makes quality factor of the biggest influence on phase noise before and after irradiation.