Q-Band Analog Predistortion Technology

With the development of satellite communications,the requirements for power amplifier bandwidth,gain,power,linearity,etc.are getting higher and higher.On the other hand,in order to obtain more spectrum resources for satellite communication,the frequency band of the communication system is gradually developing to the millimeter wave high frequency band,such as the Ka,Q,V,and W frequency bands.Due to the advantages of solid-state power amplifiers in terms of operating bandwidth,linearity and reliability,they have been continuously researched and developed,and have gradually replaced the role of traveling wave tube amplifiers in satellite communications.At the same time,the power amplifier will produce a serious distortion effect when a large signal is input,and the analog predistortion technology is an important means to improve the distortion of the power amplifier.After researching and summarizing the development trend of domestic analog predistortion technology,it is found that although analog predistortion technology has been widely studied,most of them are aimed at the frequency band Ka and below,and the research on analog predistortion technology above the frequency band Ka is rare.At the same time,there is also a lot of research space for the separately adjustable analog predistortion technology of amplitude and phase.In view of the above problems,thesis starts from the cold mold structure to simulate the predistortion circuit.These Q-band cold-mode pre-distorters are simulated and fabricated using the designs of three analog predistortion circuits based on p HEMT.The pre-distorter can achieve 5d B gain expansion and maximum 20° phase compression in the 37-42 GHz frequency band.In the cascade test with the power amplifier,the thirdorder intermodulation can be improved by 11 d Bc.The circuit has a good compensation effect on the distortion characteristics of the solid-state power amplifier.In order to further improve the tunability of the circuit,thesis starts from the research on the analog predistortion circuit of the dual-channel synthesis structure,and basically realizes the tunability of the circuit by means of the signal synthesis of the linear branch and the nonlinear branch.The linear branch in the circuit has the function of adjustable gain and phase,and the nonlinear branch generates nonlinear signal,and the expected effect is obtained through vector synthesis.The analog predistortion linearizer with adjustable amplitude and phase is simulated and processed.The test results show that the linearizer can basically realize the function of independently adjustable amplitude and phase in the frequency band of 37-42 GHz.