Tolerance Optimization of an LTCC via transition by a simple method for determining shape sensitivities of slightly shifted metallic surfaces

A perturbation approach is presented to estimate the influence of geometry variation on the performance of microwave devices. A first-order expression is given for the change of the scattering matrix due to a slight shift of a metallic surface by using the reciprocity condition between port sources and the perturbated volume element. Based on this result, the consequences of slight geometry changes can be estimated in an intuitive manner from mode field images. This is demonstrated in the practical example of a vertical microstrip-to-stripline transition at microwave frequencies for implementation in an industrial LTCC-process, where robust design is of utmost importance