Research On Millimeter Wave Linear Drive Amplification Technology For Satellite Communication

With the high-speed development of satellite communication technology,the data throughput of communication satellites is increasing,which requires communication systems with low bit error rate to improve the efficiency of signal transmission,which puts forward high requirements on the linearity of communication systems.As a widely used signal amplification device in the transceiver stage of satellite communication systems,the traveling wave tube power amplifier(TWTA)is the main source of nonlinear distortion in the whole system.Therefore,reducing the nonlinear distortion of the TWTA without affecting its efficiency has become an important research direction to improve the linearity of satellite communication systems.The linear channel amplifier(LCAMP)is an important component in the satellite transceiver system as the driving pre-stage of the traveling wave tube,which can effectively improve the nonlinear distortion while providing the driving power required by the traveling wave tube.In this thesis,the key components of the linear channel amplifier are designed and studied firstly.1.A reflective pre-distortion circuit with a broadband three-branch bridge is designed.And for optimizing the input port standing wave of the circuit,a short-circuit branch is added to the coupling port of the bridge to optimize the input port parameter S₁₁by 5d B,and a defected ground(DGS)structure is introduced to the high-resistance microstrip line in the bridge to reduce the actual processing difficulty.2.To enhance the flexibility of amplitude and phase distortion adjustment of the pre-distortion device,a pre-distortion circuit with two nonlinear branch synthesis structures is proposed.The measured amplitude expansion?5.2d B,phase expansion?52°,and can achieve in the amplitude expansion change of about 1d B,phase expansion of up to 40°adjustment range.3.A frequency band of 38.5?42.5GHz based on analog negative feedback loop and automatic level control circuit with temperature compensation is designed.The measured circuit keeps the output power fluctuation?2d B in the dynamic range of-12?-6d Bm at room temperature and?1d B in the same input dynamic range at high and low temperature.Finally,a linear channel amplifier with 38.5?42.5GHz operating band is designed by combining the key components of the above design.It is measured that the module can maintain relatively stable output power in the input power range of-24?-14d Bm under the automatic level control mode(ALC)at room temperature,and the output power fluctuation is?3d B.In high and low temperature(-55,85?)ALC mode,after adding temperature compensation,the overall change of output power curve is reduced from more than 18d B to within 10d B,and the temperature compensation amount is>8d B.For gain adjustment,in ALC mode,the gain adjustment amount is 31.3d B with0.5±0.2d B/step,in fixed gain mode(FGM),the gain adjustment amount is 30.8d B with1±0.3d B/step.The amplitude expansion of the sample module is?5.5d B and the phase expansion is?50°in the working frequency band.