The Research And Design Of Broadband And High Linear Amplifier Based On GaAs

With the vigorous development of semiconductor technology,more and more high-performance semiconductor materials have been developed and widely used in various fields of human production and life.Among many semiconductor materials,GaAs has gradually become an indispensable component in the field of electronic industry due to its excellent performance.GaAs-based monolithic microwave integrated circuit is widely used in personal mobile communication,radar,instrumentation,electronic warfare weapon systems and other fields.Thanks to the development of GaAs semiconductor technology,the performance of microwave amplifiers has also been greatly improved.The main content of this thesis is to design a broadband amplifier and a high linear amplifier respectively by using GaAs pHEMT and GaAs HBT.The first broadband amplifier adopts a distributed structure based on GaAs pHEMT.Because the characteristics of transistors have a great influence on the performance of distributed amplifiers,the design first establishes an ideal distributed amplifier based on FET small signal model,and then discusses the influence of intrinsic parameters of transistors on the performance of distributed amplifiers.Considering the large drain line loss in high frequency band,the gain unit of this design adopts Cascode structure that can compensate drain line loss.In order to solve the instability of the distributed amplifier at the cut-off frequency,corresponding measures are taken to ensure that the distributed amplifier meets the absolute stability condition.Finally,aiming at the designed distributed amplifier,the low frequency terminals of gate line and drain line are designed,which solves the problem of gain overshoot in low frequency band and improves the overall gain flatness of the distributed amplifier.The simulation results show that the designed broadband amplifier has a bandwidth of more than 30GHz.In the range of 0.1-30GHz,the small signal gain is more than 15dB,and has good gain flatness.The input and output return loss is less than-10dB,and the output power at the 1 dB compression point can reach 21dBm.The second high linear power amplifier adopts a 3-stage cascade structure based on GaAs HBT technology.The stability of the circuit is improved by adding negative feedback in the first two stages.The linearity and efficiency of the power amplifier are optimized by using active linear bias circuit and harmonic suppression.After debugging GaAs HBT high-linearity power amplifier,the test results show that the small signal gain of the amplifier reaches 36dB and S₁₁ is less than-10 dB.What's more,good input matching is obtained.The output power of 1dB compression point is 32.1dBm,and the additional power efficiency reaches 35%.When the frequency is 2.14 GHz and the output power is 24.5dBm,the ACPR test result is-47.1dBc（20MHz offset）,which achieves good linearity and the second harmonic suppression reaches-46.8 dBc.