Rigorous analysis of the higher order modes, impedance and attenuation factor of coupled striplines

The paper presents a rigorous and computationally efficient analysis of coupled striplines of arbitrary dimensions based on the transverse resonance diffraction (TRD) technique. The calculated higher order mode cutoff frequencies, impedance, coupling factors and attenuation factor are shown to give improved accuracy over a wide range of dimensions when compared with purely analytical and numerical approaches. The TRD results are also in excellent agreement with measured values for the higher order mode cutoff frequencies. The design parameters can be computed in a fraction of the time required for numerical based techniques such as finite elements.