Model Establishment And Characteristics Analysis Of Frequency Converter Based On Vector Network Analysis Technology

With the development of high-speed broadband communication and electronic systems,the bandwidth for the operating signals carried by systems is becoming wider,and the modulation methods are becoming more complex.Therefore,the nonlinear effects of the system is increasingly significant.The microwave modules in communication systems are the main sources of nonlinear effects;in particular,the amplification and frequency conversion devices in them determine the nonlinear response characteristics of the entire system.Therefore,nonlinear modelling and measurement of the amplification and frequency conversion devices are essential for the improvement of high-speed broadband communication and electronic system design.Because of the influence of the nonlinear effects,the microwave modules have a significant memory effects when excited by broadband signals.Researchers attribute the memory effects of the microwave modules mainly to the influence of amplifiers and have conducted a comprehensive research on the characteristics of the memory effects of amplifiers through mechanism analysis,common characteristic description,highprecision model construction,and the creation of new measurement methods.However,with the development of high-speed broadband communication and electronic systems,the contribution of frequency conversion devices to the memory effects of microwave modules has become increasingly obvious.The study of the intermodulation component of the frequency conversion devices is an important point for analyzing the characteristics of the memory effects.Studies on the asymmetry exhibited by the upper and lower sidebands of the intermodulation component have been conducted domestic and foreign scholars through experimental investigation and model building,but the mechanism behind the phenomenon has not been analysed,and its common characteristics have not been described.Therefore,a more in-depth study on the characteristics of the memory effects of the frequency conversion devices from the perspective of the intermodulation component is needed.In addition,the accurate measurement methods of frequency conversion devices have always been a focus of research in both China and abroad.The error model with the frequency offset mode(FOM)can,to some extent,reduce the influence of system errors on the measurement results obtained from frequency converters.However,the limitations of this error model may lead to certain errors in the calibration of the measurement results obtained from frequency converters.Therefore,it is necessary to perform in-depth analyses on the limitations of the FOM error model and evaluate to what extent these limitations affect the calibration results of different frequency converter types.The above-mentioned problems need to be addressed urgently for frequency conversion devices.The main contributions and innovations of this study are as follows.(1)An analysis model for the memory effects of the two-tone signals of the frequency conversion devices was developed to characterize the common features of the third intermodulation(IM3)and to analyse the mechanism of the phase asymmetry of the upper and lower sidebands of the IM3 component.Two models for analysing the memory effects of frequency conversion devices were developed.One is based on the simplified generalized frequency response function(S-GFRF)and the other on the time varying modulation function(TVMF).The theoretical derivation,simulation,and experimental verification of these two models were performed.The results showed that the S-GFRFbased memory effects analysis model can accurately predict the common characteristics of the amplitude and phase variations of the IM3 component with the spacing between two-tone signals,while the TVMF-based memory effects analysis model can effectively analyse the second-order memory effects mechanism of the phase asymmetry of the upper and lower sidebands of the IM3 component.(2)The common characteristics of the IM3 component of the frequency conversion devices under the excitation of the two-tone modulated large carrier signals were analysed by modelling.Based on the memory effects analysis model architecture of the S-GFRF,the analysis model of the memory effects of the frequency conversion device with the two-tone modulated large-carrier signal was derived.Meanwhile,a new two-tone measurement system for frequency conversion devices based on vector network analysis technology was designed.This test system can be used to verify the memory effects analysis model of the two-tone modulated large carrier frequency conversion devices and supports the simplification of the digital predistortion model of the frequency conversion devices.(3)A new simulation and experimental system for the load pull of frequency conversion devices was designed.The limitations of the error model with the frequency offset mode were analysed in depth using this system.The influence of the error model with the frequency offset mode on the accuracy of the calibration results of frequency conversion devices was also investigated using the X-parameter theory.The influence pattern of the error model with the frequency offset mode on the calibration results of different types of frequency conversion device was verified by simulation and experiment.