Obtaining high-performance time-domain characteristics from calculated S-parameters for various electronic package and interconnection structures

Previous efforts by our group have focused on frequency domain analysis of various packaging structures and on the generation of equivalent circuits for use by circuit designers. Other articles have also presented frequency-domain or time-domain results such as pulse degradation for various IC structures. This paper attempts to tie the two together by using the finite-difference time-domain (FDTD) method to calculate the frequency dependent S-parameters as well as the time-domain pulse propagation characteristics of various packaging structures to develop guidelines that may help circuit designers predict limits of packaged ICs. Some general guidelines are presented to relate information from S-parameters to the type of pulses that can be transmitted through/to the ICs with minimal distortion and coupled noise. For example, it is shown that for crosstalk, the frequency at which a coupled signal rises to -10 dB is proportional to the reciprocal of the rise time of the digital pulse. Furthermore, for transmission, the frequency at which the insertion loss has dropped to -3 dB is proportional to the reciprocal of the total pulse length. Examples of this relationship are demonstrated for a microstrip via and a crossover, among others.