Design Of Doherty Amplifier And Distributed Amplifier Based On GaAs

Amplifier design has long been a focus and hot spot in RF front-end design.In recent years,the rapid development of communication technology has improved the quality of our lives.However,with this,we must overcome the challenges in the design process of communication systems.For example,in order to effectively utilize spectrum resources and realize high-speed transmission of signals,complex digital modulation techniques such as OFDM(Orthogonal Frequency Division Multiplexing),which are not constant envelopes,are widely used.However,non-constant envelope signals obtained by such modulation have high peak-to-average power ratios(Peak to Average Power Ratio,PAPR),which requires the amplifier to maintain good linearity over a large back-off power range,as well as higher efficiency.Furthermore,the development of communication systems,in addition to maintaining high-speed transmission of data,also puts higher demands on the bandwidth of communication systems.The design of wideband amplifiers is another hotspot in scholars' research.Distributed amplifiers,as typical ultra-wideband amplifiers,have always been one of the focuses of scholars.Firstly,the research background and development status of Doherty amplifiers and distributed amplifiers are mainly investigated.The various performance indicators of amplifiers are explained.The indicators include gain,output power,noise figure,efficiency,etc.,and the classification of amplifiers is carried out.Then two amplifiers,a Doherty amplifier and a distributed amplifier,were designed separately to give a detailed design process.In order to pursue high efficiency in back-off region,a Ka-band broadband Doherty amplifier is designed in Chapter 3 to meet the needs of communication systems.Designed with a phase shift,low Q wideband matching network to achieve P1 dB greater than 24 dBm in a wide frequency range of 24 – 30 GHz,saturated output power of 26 dBm,typically at 28 GHz,peak saturation efficiency of 37%,and the efficiency is 27% with output power back-off of 6 dB from saturation output power.In the fourth chapter,in this thesis,a distributed amplifier of 0.9 – 6 GHz for the design of wideband amplifier has been designed.The amplifier is based on 0.25-?m GaAs process and uses cascode as gain unit to achieve high gain and high power output.The test results show that the designed small-band signal gain is greater than 12.5 dB,the output P1 dB is greater than 30 dBm,and the input return loss is below-10 dB.