An Insertion Loss, Phase and Delay Measuring Set for Characterizing Transistors and Two-Port Networks Between 0.25 and 4.2 gc

Abstract

A new insertion loss, phase and delay measurement tool has been developed for characterizing gigacycle bandwidth transistors and general two-port networks on a small signal basis over a frequency range from 0.25 to 4.2 gc. Maximum inaccuracies are 0.1 db, 0.6 degree (over a 40-db loss range), and 0.5 nanosecond (over a 20-db loss range). Above 2.0 gc, the errors may double. The particular parameters selected for measurement are closely related to the scattering coefficients of the device under test, evaluated with respect to a 50-ohm impedance level. When measuring transistors, measurement data are corrected for the residuals of jig and bias fixtures. Transformation from the measured parameters to other sets (e.g., h, y, or z matrices) is routine. In order to minimize “instrument zero-line” and eliminate errors from circuit drift, a rapid sampling technique sequentially compares the unknown with a high-frequency reference. Measurement accuracy is held substantially independent of test signal frequency by heterodyning the measurement information to a fixed IF, where detection is performed by “IF substitution”, using adjustable standards of loss, phase, and delay. Substantial use of automatic control circuitry contributes to an easy and facile interface between machine and operator. This paper discusses the operation and design of the test set and its use as a tool in characterizing transistors.