Nanosecond Pulse Circuit Board Interconnections

Abstract

The difficulties involved in using mating connectors to interconnect nanosecond pulse circuit boards are discussed. The effects of such connectors on pulse characteristics may be predicted by the techniques presented in this article. Experimental verification of predicted performance is presented in the form of photographs through the use of time domain reflectometry. The connector used to illustrate these techniques is a miniature printed circuit board type. An equivalent circuit for this connector is arrived at through an experimental procedure. Additional experimental justification of this circuit is presented. This equivalent circuit is used to derive an expression for the waveform of the pulse reflected from a connector contact pair. The risetime degradation of the pulse transmitted through the connector contact is evaluated by use of the equivalent circuit. The expression for the waveform coupled into a set of contacts by a pulse driving an adjacent pair is derived with the aid of the equivalent circuit. These expressions are presented and illustrated in the text. The mathematical derivations are presented in a set of appendices. Experimental verification of the analysis in the form of photographs of pulse reflection and pulse crosscoupling waveforms is offered. Methods of improving performance of the connector with regard to pulse risetime degradation, pulse reflection, and crosscoupling are demonstrated. Various arrangements of contact connectors and their relative merits are discussed.