In writing the short feature on Picosecond Pulse Labs' marvelous little pickoff tee (see below), I was reminded of numerous lessons in time-domain testing from a man who, over the course of time, became my friend. On the day that we met, he was a veritable bundle of energy. Nestled away in a combination office and laboratory in Santa Monica, CA, Siegfried Knorr split his time between his services as an Adjunct Engineering Professor at the University of California at Los Angeles (UCLA) and his then new company, Colby Instruments. At the time, he was building pulse generators for Motorola, among other customers, and had developed machines that could produce extremely short, clean pulses for testing radars and high-speed digital systems.

Always generous with his time, Siegfried explained the layout of his invention and then pointed to a bank of high-speed oscilloscopes from the likes of Tektronix and Hewlett-Packard (now Agilent). He offered a great deal of insights into how to interpret information from a time- domain measurement and how, back then, this understanding of the time domain was becoming a lost art. Much of what I learned about the time domain came from dinners with Siegfried over the years until his death a few years ago.

In seeing a data sheet for the new pickoff tee, I am reminded that some, such as Jim Andrews who founded Picosecond Pulse Labs, are still engaged in the creative art of time-domain testing. Such testing can often shed light on the inductive and capacitive effects of a circuit on a high- speed signal, and provides a "second view" to traditional frequency-domain measurements.

by Jack Browne, MWRF Technical Director