Computations for radiation and surface-wave losses in coplanar waveguide bandpass filters

A new approach is developed to simulate both radiation and surface-wave los ses in general coplanar waveguide (CPW) discontinuity structures. The newly derived formulas are concise, simple, and efficient for computation. Full- wave characterization of CPW filter structures are first accomplished by th e mixed-potential integral equation and the method of moments. Given equiva lent magnetic-current distributions on the apertures of a CPW, the matrix p encil approach is applied to extract the scattering parameters and the new formulas are employed to obtain the losses and far-field patterns of the sp ace-wave radiation and surface wave. Simulation of the calculated radiation and surface-wave losses by field theory is found to be consistent to the t otal power loss determined from the scattering parameters by circuit theory , which verifies the correctness of our new expressions.