Efficient TLM sensitivity analysis exploiting rubber cells

The Adjoint Variable Method (AVM) is applied for the first time to perform sensitivity analysis for Transmission Line Modeling (TLM) using rubber cells with modified tensor properties. Rubber cells allow the conformal modeling of off-grid boundaries in the TLM domain using modified tensor properties. The scattering matrix of the rubber cell is analytically dependent on the dimensions of the modeled discontinuities. Using this property, an exact adjoint system is derived. The original and adjoint systems supply the necessary field information for the rubber cell based sensitivity calculations. Our technique is illustrated through sensitivity analysis and optimization of a waveguide bandpass filter.