Comparison of multi-port VNA architectures — Measured results

Multi-port vector network analyzers (VNA) have become important measurement tools for the characterization of high frequency/high speed computer system and communications interconnects. These systems utilize many parallel channels of differential transmission lines to carry the high bandwidth data between devices. The need to measure the differential transmission line and crosstalk characteristics of these structures has driven the need for 4, 8, and 12 ports on microwave VNA's. 4-port VNA's have been commercially available for some time to address part of this need. In order to avoid additional complexity and cost these early architectures are unable to utilize the more recent, non-redundant calibration algorithms. These faster, more flexible algorithms can reduce the calibration and measurement time for multi-port devices at some cost to measurement accuracy. Through the evaluation of commercial verification devices after multiple calibrations, this paper illustrates that by comparing algorithms across two 4-port architectures, this compromise in accuracy may not be significant when compared to the savings in time and fewer standard connections.