BROADBAND MATCHING FOR CIRCUITS WITH RESISTIVE TERMINATIONS

Abstract

The work presented here explores the broadband matching characteristics for repre-sentative circuits with resistive terminations for frequencies up to 40 GHz, the typical band of interest for 100 Gigabit Ethernet (100GbE) applications. A simple test circuit comprised of high-frequency connectors, microstrip transmission lines and resistive terminations was de-signed and fabricated to better understand the mechanisms affecting broadband matching. High fidelity measurements were performed using both a vector network analyzer (VNA) and a time-domain reflectometer (TDR). The data provided by these two devices were used to isolate the broadband behavior of the individual circuit components through the time-gating process, and that process showed the microstrip transmission line on FR-4 to be the greatest contributor to high-frequency mismatch. One facet of the work presented here was to explore the accuracy of a state-of-the-art electromagnetics model in estimating the broadband behavior of the test circuit. Comparisons of measured and modeled data are provided here, and those comparisons show reasonable agreement