Design Of Filters And Cable Test Technology Based On Reconstruction Of Non-uniform Transmission Lines

Microwave devices,mainly include filters,couplers,resonators and etc.,which are used to dispose the input signal specifically,so that the output signal may meet a certain demand for amplitude,frequency and phase.RF and microwave devices are made by the discontinuity of the transmission line,which in essence are non-uniform transmission lines,so the design of RF and microwave devices can be seen as the design of non-uniform transmission lines.Reconstruction of Non-uniform transmission lines(NTLs)is an effective method for inverting the transmission line structure from a specific response.It can calculate the impedance distribution of transmission lines from the given S-parameter and time-domain response,and then obtain the structure of the non-uniform transmission lines.Therefore,reconstruction of NTLs is one of the most important technique for microwave device design.Test fixture must be introduced when testing the high-speed data transmission line.The introduction of the non-ideal test fixture can cause measurement errors,so calibration of the test fixture is particularly important.Test fixtures can be considered as one of the NTLs,so the reconstruction of NTLs can be used for calibration of test fixture.The main work of this paper is as follows:1.Realization and verification of the validity of reconstruction algorithm for NTLs based on time domain reflectometry(TDR).Analysis of the effects of truncation and windowing on impedance reconstruction.Research on the modeling method of NTL filters from frequency domain to digital domain.2.The reflection coefficient of two low-pass filters is designed by MATLAB digital filter design tools,and the corresponding non-uniform transmission line structure is reconstructed;secondly,a NTL wide stopband filters is designed by cascade and periodicity.3.By using MATLAB digital filters design tools,the reflection coefficient of a double passband digital filter is performed.The corresponding transmission line structure is then obtained by using NTL reconstruction algorithm.Through simulation and optimization,a NTL double passband filters is finally designed,with a low-pass band and a bandpass band.4.In the high-speed data cable testing system,the NTL model of the test fixture is reconstructed after measuring the reflection coefficient,thus the automatic calibration of the test fixture is realized.The cables can be tested directly without a separate calibration of the test fixture,which greatly improves the test efficiency.Finally,a set of cable test system is developed based on this method.