Fixture crosstalk assessment structure for VNA measurement how to quantify fixture crosstalk when it is not completely de-embeded?

In today's high-speed interconnect design, crosstalk is a critical parameter and the accurate measurement is very important. However, in the calibration procedure, the fixture crosstalk is usually ignored to avoid over-complicated de-embedding algorithms. This leads to certain levels of error in the de-embedded results of crosstalk value. Engineers have been struggling in assessing the quality of crosstalk measurement data as there is no clear indicator as to how much of the measured crosstalk is attributed to the fixture design. In this paper, we propose a dogleg/ spiderleg structure as a method to quantify the fixture crosstalk which remains after a calibration/de-embedding. The validity as a test fixture crosstalk assessment structure is examined extensively and the usage is verified.