On the design of microwave filters with coupled resonators

In this paper a synthesis method is presented, which is generally applicable to symmetric or asymmetric characteristics of microwave bandpass filters with coupled resonators. The realization procedure is based on law-pass prototype filters with reactive circuit elements. Commencing with the scattering coefficients S-11(p) and S-21(p) the transfer matrix polynomials are constructed. it is shown that with the circuit elements capacitor, frequency-invariant susceptance and imaginary admittance inverter low-pass prototype filters are designed that may be realized in microwave bandpass filters with coupled resonators.