Equivalent Circuit Modeling Of Transmission Line Metamaterial Unit Cells

Abstract

This thesis proposes a novel technique for extracting equivalent circuit models for transmission-line metamaterial unit cells. The technique uses pseudo-inverse techniques to find a direct solution of the over-determined matrix equation formed by matching a specific equivalent circuit topology to Method of Momentum (MoM) and measured frequency response data. The technique is shown to be robust to uncertainty in the frequency response data for a CRLH unit cell implemented in grounded coplanar waveguide (GCPW). This thesis also investigates how the GCPW unit cell can be encased within a substrate integrated waveguide (SIW) to suppress undesirable GCPW modes. A parametric study of via hole placement of the SIW walls using MoM simulation data is described for characterising the performance of the SIW- GCPW through-line structure. The thesis then shows how these two aspects can be applied to CRLH units cells in GCPW-SIW for both measurement and MoM frequency response data. Good agreement is observed between the frequency response calculated using the equivalent circuit model and the measured or simulation data. The potential application of the algorithm lies in efficient guidance and validation for new designs of CRLH TL structures.