Characterization of non-symmetric coplanar waveguide discontinuities

Abstract

A general technique to characterize non-symmetric coplanar waveguide (CPW) discontinuities with air-bridges, where the fundamental coplanar and slotline modes may be excited together, is presented. First, the CPW discontinuity without air-bridges is analyzed using the space-domain integral equation method. Second, the parameters (phase, amplitude, and wavelength) of the coplanar and slotline modes are extracted from an amplitude modulated-like standing wave existing in the CPW feeding lines. Then, a 2n*2n generalized scattering matrix of the discontinuity without air-bridges is derived which includes the occurring mode conversion. Finally, this generalized scattering matrix is reduced to an n*n one by enforcing suitable conditions at the ports which correspond to the excited slotline mode. For the purpose of illustration, the method is applied to a shielded nonsymmetric short-end shunt CPW stub, whose scattering parameters are compared with those of a symmetric one. >