GaAs PHEMT Noise Model And Design Of Low Noise Amplifier

GaAs-based pHEMT devices have been widely used in the design of radio frequency integrated circuits for wireless communication systems because of high electron mobilit y and low noise characteristics,particularly in RF front-ends low noise amplifier with high requirements for noise and sensitivity.With the rapid development of modern wireless communication system,Higher and higher requirements for GaAs MMIC LNA performance,the design and production of high performance LNA requires accurate small signal and noise models of semiconductor devices to provide theoretical support and design basis.Therefore,the establishment of accurate device model is criticial to the circuit design and simula t io n optimization of LNA.Based on the above background,in this dissertation,the small signal equivalent circuit model,noise model,model parameter extraction method and design of low noise amplifier for GaAs-based pHEMT have been studied,the main results are summar ize d as follows:1.Introduced the basic physical structure parameters of GaAs pHEMT devices.Based on the 0.15?m In GaAs Low Noise pHEMT process developed by Taiwan Win Semiconduc tor Company,the accurate GaAs pHEMT small signal equivalent circuit model is established.Using microwave network signal matrix technology,a general parameter extraction method based on simplified equivalent circuit topology under special bias for step-by-step extraction of model element parameters is proposed.Analyzed error with measured s parameters,it is proved that the established small signal equivalent circuit model and parameter extraction method have the good characteristics of precision(S-parameter amplitude and phase error less than 6% and 3 degrees)and wide band(2~26GHz),which provides the necessary data support for noise model analysis and circuit design.2.Based on the noise noise generation mechanism of GaAs pHEMT,the noise equiva le nt circuit model is characterized by the power spectral density of noise and the expression of undetermined noise factor to improve the traditional method of describing the noise source by empirical formula.A simple noise de-embedding technique based on noise correlation matrix theory is proposed for the effect of extra noise introduced by parasitic elements at high frequency.Considered the shot noise effect caused by gate leakage current,the analytical formula of noise factor of PUCEL and POSPIESZALSKI noise model is corrected.The established process of GaAs pHEMT noise model from noise de-embedding to noise factor extraction are improved.Compared the noise parameters of the simulation with measured data,this noise model can demonstrate the accuracy of predication.3.The impact of load RLC network on input match in wideband low noise amplifier design is analyzed by the established small signal model and the theoretical analysis of the mechanism principle of multi-frequency matching gain compensation is studied.Therefore,the design ideas of the bilateral matching and gain compensation are adopted to achieve excel ent RF characteristics like return loss and gain flatness in the whole frequency band.Based on the theoretical analysis of noise model,a broadband high-gain low-noise amplifier with 8~12GHz three-stage CASCADE structure is designed and the design process includes the selection of the circuit topology,the circuit design of the input and output stages,the analysis of the matching circuits between the stages and the layout optimization.The layout simulation show that,within the working band 8~12GHz,the input and output return loss is less than-10 d B,the small signal gain is 33.2±0.5d B,the noise figure is less than 2d B and a full band stability is realized.The results show that the chip has good performance of the noise and gain.