Research On(Micro-) Coaxial Filter Based On SOL De-Embedding Technology

With the maturity of the fifth generation mobile communication technology(5G),microwave circuits are gradually developing in the direction of low loss,high frequency band and integration.Due to the continuous improvement of frequency,the research on microwave circuit de-embedding technology is also extremely important.The traditional de-embedding technology often needs to be combined with computational electromagnetics algorithm,and the de-embedding process is complicated.The purpose of this paper is to study an efficient and accurate Short-Open-Load(SOL)numerical de-embedding technique.By using this technique,the equivalent circuit parameters of lumped elements based on(micro-)coaxial technology are extracted,and then microwave filters applied to 5G communication band are comprehensively designed by combining filter theory.The specific research contents are as follows:(1)The principle and verification of SOL de-embedding technology: The network analysis method of SOL de-embedding technology is studied in detail,and the analytical expressions of transmission matrix parameters of the network to be tested are derived.Subsequently,the technology is applied to(non-)uniform microstrip transmission network,and the equivalent circuit parameters and the characteristic parameters of periodic structure are extracted,and compared with the parameters obtained by traditional methods to verify the accuracy of SOL method.Furthermore,the technology is applied to extract the parameters of rectangular(micro-)coaxial transmission network,and the equivalent circuit parameters of capacitive and inductive lumped elements and J/K inverter based on rectangular(micro-)coaxial technology are accurately extracted.The results show that this method completes the de-embedding of the network to be tested by introducing the ABCD matrix in the microwave network,without requiring whether the feeders at both ends of the network to be tested are uniform,which greatly improves the application scope and convenience of extracting equivalent circuit parameters.(2)Comprehensive design of(micro-)coaxial low-pass and band-pass filter: Firstly,a low-pass prototype filter with cut-off frequency of 6 GHz and insertion loss of 0.01 d B is designed by using micro coaxial lumped elements.Then,a fifth-order bandpass filter with a center frequency of 3.5GHz,a relative bandwidth of 12% and an insertion loss of 0.05 d B is designed by using a micro-coaxial J converter and a 1/2 wavelength transmission line.The physical size of the filter is14.50 mm× 13.58 mm× 0.50 mm.Then,a bandpass filter with order 5,central frequency of 26 GHz,relative bandwidth of 14% and insertion loss of 0.05 d B is designed by using micro-coaxial K converter and 1/2 wavelength transmission line.The physical size of the filter is 5.89 mm× 4.00mm× 0.9 mm.Full-wave simulation is highly consistent with the results of scattering parameters obtained by equivalent circuit.Finally,due to the processing cycle of the micro-coaxial(Poly Strata)process,a band-pass filter designed by coaxial J-converter and 1/2 wavelength transmission line is designed by using the 3D printing(Poly Jet)process which is basically similar to the micro-coaxial processing principle,and the accuracy of the de-embedding technology and the filter design theory is verified.