| In order to meet the demands of large-data capacity,high-speed transmission and obtain more spectrum resources,modern wireless communication systems are developing towards millimeter-wave communication technology.The solid-state power amplifier is the core device of the transmitter of the millimeter-wave communication system.Its power output is relatively high and even reaches the saturated output state,that is,it generally works in the nonlinear region to achieve higher efficiency and longer-distance transmission,but this will cause nonlinear distortion and reduce the quality of signal transmission.For the purpose of improving the linearity of the communication system and ensuring the quality of signal transmission,it is necessary to adopt linearization technology.The predistortion linearization technology is relatively mature and is used for the linearization of low-frequency power amplifiers,but there are still problems such as limited by operating frequency,input power range,etc.,which make it difficult for the system to obtain high-efficiency linearization performance with broadband and large dynamic range;in addition,GaN power devices in solid-state power amplifiers are more and more widely used today because they are suitable for high frequency and high output power applications.Due to the high operating temperature of GaN power devices,strong nonlinear characteristics,and 1d B compression point is difficult to define and other characteristics,it is difficult to linearize it,especially above the millimeter-wave frequency band,there is still a lack of relevant design experience for the linearization of GaN power devices,so it is necessary to conduct further research on the pre-distortion technology of millimeter-wave GaN power amplifiers.The main research contents are:(1)In view of the defects of traditional predistortion technology,research and discussion on new schemes and new architectures are carried out.Firstly,it is necessary to carry out the basic theoretical derivation analysis and software simulation verification of the new scheme.The simulation results show that the new architecture has an excellent effect on improving the nonlinear distortion of the power amplifier.(2)The fabrication of the key components that the system needs to use is completed.The Wilkinson power divider,is working in the range of 26?34GHz,whose amplitude difference between the two branches is 0.05 d B at most,the phase difference is at most0.51°,and the transmission loss is less than 0.51 d B,reaching a good level;the 40 d B coupler is working in the range of 29?31GHz,and the coupling is 37.3?39.6 d B,the transmission loss is less than 0.2d B,which is basically consistent with the simulation results;the reflective phase shifter is working in the range of 29?31GHz,the transmission coefficient fluctuates around-5.5d B,the fluctuation range is less than ±0.8d B,and the phase shift range reaches 160°,which generally meets the design requirements;(3)the production and test analysis of the linearization system are completed.The main power amplifier module and the linearization module are respectively tested for single-tone signal and dual-tone signal and then compared and analyzed.In the working frequency range of 29?31GHZ,for the single-tone signal test,adding the power amplifier of the linearization module,the amplitude compression is improved by 1.91?3.55 d B,the phase compression is improved by 6.24?7.73°,and the output 1d B compression point P-1d B is improved by 2.04?3.95 d B.A good level of improvement has been achieved;For the two-tone signal test,the third-order intermodulation coefficient is improved by0.59?2.07 d B when the power amplifier with the linearization module is added.The work of this thesis has a good guiding significance for the exploration and implementation of the linearization of millimeter-wave GaN power amplifiers. |
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