Research On Analog Predistortion Technology Of V-band Traveling Wave Tube

With the rapid development of human society,the communication field has higher and higher requirements for the richness of system operating frequency bands.Low-frequency communication can no longer meet today's increasing communication needs,and it has become an inevitable trend to obtain high-quality communication.The development and application of millimeter wave and even submillimeter wave signal resources have gradually attracted the attention of researchers.However,with the increase of the application frequency,the influence of the linearity of the satellite system on the accuracy of signal transmission cannot be ignored.As the key device in the system,the power amplifier(PA)is the main factor affecting the linearity of the communication system.In order to improve the nonlinear distortion of the PA and improve the communication quality of the millimeter wave system,the research on the corresponding linearization technology is of great significance.In this Thesis,we choose the analogue pre-distortion linearisation technique,which is effective in improving the non-linear distortion of power amplifiers in the millimetre wave band and enables them to maintain a high output power,as the theoretical support for the design of a linearisation module for a travelling wave tube power amplifier(TWTA)in the V-band(59.1-61.1 GHz).The first Analog Predistortion Linearizer(APD)selects Schottky diodes as the core device,and selects the reflective circuit structure for design.At the same time,considering the operating frequency of the V-band,the WR15 waveguide is used as the port instead of the traditional microstrip bridge structure.It can be seen from the test results that the designed APD has an amplitude expansion greater than 7.8d B and a phase expansion greater than 28°.On this basis,in order to make the designed APD have a better matching degree with the corresponding TWTA,a V-band TWTA linearization driver module is designed.Experiments show that in the frequency range of 59.1?61.1 GHz,the input power dynamic range is 30 d B,the gain expansion?4.7 d B,the phase expansion?45.6°,maximum output power?15 d Bm,input/output VSWR<2:1,and it has the ability to match well with TWTA.The second increases the adjustability of the amplitude and phase,improves the reflective circuit structure,and selects a two-way circuit structure for design.Considering the operating frequency and other factors,a V-band waveguide power divider is designed as the input and output structure.A ceramic substrate loaded with thin film resistors is inserted into the center of the power divider to effectively increase the isolation of the two output ports.It can be seen from the simulation results that this APD can achieve a gain expansion?7.6 d B and a phase expansion?55°,and the newly added linear branch can adjust the amplitude independently without affecting the phase.Effectively improve the adjustability of amplitude and phase.