A new approach to the efficient determination of the hybrid and complex spectrum of inhomogeneous, closed waveguide

Many hybrid modes are required in computing discontinuities by modal methods in structures such as finline, cpw or microstrip. We provide a new analytical method based on a novel discretization of the Maxwell´s equations by means of the modes at cutoff. This approach gives physical insight as well as providing a compact and effective algorithm for finding the characteristics of many modes, including their below cutoff and complex behaviour. Numerical results are provided for finline, showing excellent agreement with existing data, with very modest running times on an ordinary P.C.