Validation of the Reference Impedance in Multiline Calibration with Stepped Impedance Standards

TL;DR

This paper introduces a novel method to validate the reference impedance in multiline TRL calibration by using multiple stepped impedance lines to extract the broadband reflection coefficient, enhancing calibration accuracy.

Contribution

A new technique utilizing multiple stepped impedance lines to experimentally validate the reference impedance in multiline TRL calibration without fully defined standards.

Findings

Effective validation of reference impedance demonstrated on PCB microstrip structures.

Method improves calibration accuracy by detecting impedance inconsistencies.

Applicable to broadband measurements with minimal additional standards.

Abstract

This paper presents a new technique for evaluating the consistency of the reference impedance in multiline thru-reflect-line (TRL) calibration. During the calibration process, it is assumed that all transmission line standards have the same characteristic impedance. However, these assumptions are prone to errors due to imperfections, which can affect the validity of the reference impedance after calibration. Our proposed method involves using multiple stepped impedance lines of different lengths to extract the broadband reflection coefficient of the impedance transition. This reflection coefficient can be used to validate the reference impedance experimentally without requiring fully defined standards. We demonstrate this method using multiline TRL based on microstrip structures on a printed circuit board (PCB) with an on-wafer probing setup.