NON-REFLECTIVE MICROWAVE FREQUENCY-SELECTIVE CIRCUITS BASED ON COUPLED STRIPLINES AND LUMPED RLC-ELEMENTS AND THERE APPLICATION

Abstract

Non-reflecting frequency-selective circuits (NFSC) based on coupled strip lines (CSL) and lumped RLC-elements are investigated. The frequency characteristics of NFSC are analyzed for known design parameters of CSL, and parameters of RLC-elements. It is shown that the use of the proposed circuits containing a section of coupled lines, the diagonal ports of which are loaded with the impedance of RLC circuits on lumped elements, makes it possible to obtain the frequency response of a bandpass filter with a minimum reflection coefficient from the input and output in a single passband and stopbands in a wide frequency range. The inverse problem of determining the impedance of RLC circuits from lumped elements based on a given scattering matrix of the NFSC has been solved. The parameters of non-reflecting filters based on the proposed circuits have been experimentally confirmed: losses of –2.1 dB at a central frequency of 949.2 MHz of a passband of 174.1 MHz; return losses of no more than – 10 dB up to a frequency of 7.5 GHz in the entire frequency range