| With the rapid development of 5G technology,wireless communication is developing towards the trend of high power and broadband.As the core part of communication system,power devices have been more widely used.The linearity of power devices will affect the transmission performance of the whole communication system,so the characterization of input and output characteristics of power devices is particularly important.The complete design of power devices includes two parts: linear S-parameter measurement and nonlinear parameter measurement.In this paper,some problems existing in the measurement of power devices are studied and discussed.The main content of the thesis is divided into the following parts:Firstly,through the summary of the probe structure,a microwave test probe is simulated and designed.With the integration and miniaturization of power devices,the on-chip measurement of S parameters becomes more and more complex.As a key tool for on-chip S-parameter measurement,microwave probe undertakes the important function of transmitting measurement signal.In this paper,the mainstream microwave probe structures are summarized and analyzed.A microwave test probe with coaxial interface,microstrip transmission and GSG coplanar waveguide tip structure is designed by using HFSS electromagnetic simulation software.The equivalent object is made by using PCB process.The trend of experimental measurement results is close to that of simulation.It is verified that the structure of the microwave probe designed in this thesis is reasonable and has reference value for engineering application.Secondly,different nonlinear measurement techniques are compared and analyzed.Aiming at the problems of slow measurement efficiency and incomplete measurement parameters of traditional static measurement techniques,a scheme for testing the memory effect of power amplifier is proposed.In this scheme,the vector signal generator is used as the excitation,the vector signal analyzer is used for signal acquisition,and the computer is used for digital baseband signal processing.Through the test scheme,a single measurement can achieve a comprehensive acquisition of nonlinear parameters,and improve the test efficiency.In addition,the problem of data synchronization in the test process is deeply studied,and an algorithm based on cross-correlation interpolation synchronization is proposed.By testing several different types of modulation signals,the test scheme can stably characterize the nonlinearity of power amplifier.After comparison,the test scheme and synchronization algorithm results are close to the current instrument measurement results.Finally,when the modulation signal bandwidth increases gradually,the nonlinear and memory effects of power devices can not be ignored.The linearization technology of power devices is compared and analyzed,and the digital predistortion technology is selected as the research direction.Through the simplified Volterra series memory model,the memory effect behavior of power amplifier is modeled.The linearization of digital predistortion is realized by using indirect learning structure.After digital predistortion,the AM-AM distortion effect and AM-PM distortion effect are improved. |
