MODELING OF HERMETIC TRANSITIONS FOR MICROWAVE PACKAGES

Two numerical techniques, the finite difference in time domain (FDTD) and the finite element method (FEM) in frequency domain, are employed to characterize microstrip hermetic transition geometries in an effort to investigate high-frequency effects, Measurements performed on thes e transitions compare favorably with theory, Two different types of tr ansitions have been analyzed from 10 to 25 GHz and have been found to be limited in performance by higher return loss as frequency increases . It is shown that microstrip-through-CPW hermetic transitions in the shielded environment may suffer from parasitic waveguide modes which, however, can be eliminated with the use of vias at appropriate locatio ns, The hermetic wall on top of the CPW section shows a relatively sma ll (less than or equal to 2 dB) effect on the original circuit perform ance, Similarly, the hermetic bead transition shows good performance a t a lower frequency region while it degrades as frequency increases. T his indicates the need for very careful characterization of transition s intended for use in microwave and millimeter-wave applications. (C) 1996 John Wiley & Sons, Inc.