Simulation and optimization of dummy loads for wideband microwave calorimeters

A high resolution two-dimensional finite difference in time domain method (FDTD) with uniaxial perfectly matched layers (UPMLs) was applied to analysis of a three-layer wide-aperture microwave calorimeter. The method was shown to be an efficient tool for calculating the optimum geometric parameters of a semi-infinite (periodic in one coordinate) model of the dummy load. Using the time-domain results, the frequency-dependent transmission and reflection coefficients of the load were calculated for normal incidence of a monochromatic plane wave at operating frequencies range of 1-12 GHz (L-, S-, C- and X-bands) for the first time. The results of calorimeter structure optimization are very useful for manufacturing real liquid-filled experimental calorimeters.