High Frequency PCB Probing with Fixture Removal for Multi- Port Devices

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  • Author: By Heidi Barnes, Jose Moreira, Mike Resso, and Robert Schaefer Wang, Tom Schiltz
Modern day printed circuit boards (PCBs) have easily met the challenge of 10 GHz high frequency designs and now push well beyond 40 GHz. Higher complexities of mixed signal devices and increasing densities of sub-millimeter pitch packaging creates a significant multi-port design challenge that is often difficult to verify or troubleshoot with existing measurement calibration techniques. Full characterization of a signal path is easily done with a high frequency Vector Network Analyzer, but making the fixture connection from the large coaxial inputs of a VNA to the planar PCB substrate is not a trivial problem at high frequencies [1]. The presence of crosstalk in the multi-port fixture connections and the issues in designing relevant PCB probe calibration standards can easily create a roadblock to acquiring accurate measurements of a PCB footprint or signal path. This article will explore the use of an optimized probe to PCB interposer technique along with simplified calibrations with de-embedding to provide robust high frequency multi-port measurements of PCB structures.