The frequency-domain transmission line matrix method-a new concept

A frequency-domain transmission line matrix (TLM) method for the frequency-selective S-matrix computation of 3D waveguide discontinuities is presented. It combines the flexibility of the conventional TLM method with the computational efficiency of frequency-domain methods. The basis for this technique is the excitation of an impulse train of sinusoidally modulated magnitude, which retains the form of an impulse while its envelope contains the information of the structure at the modulation frequency. Utilizing the diakoptics technique in conjunction with the concept of the intrinsic scattering matrix, the original electromagnetic field problem is simplified to a matrix algebra problem. A variety of structures have been analyzed in order to check the accuracy of the approach, and excellent agreement has been observed in all cases. S-parameters for CPW air-bridges including finite thickness and conductivity of the metallizations are computed. The effect of superconducting air-bridges is analyzed