Impedance measuring scheme using a three-probe microstrip circuit

Abstract

This report is the account of a project aimed at producing a measurement system for determining the impedance of unknown loads at microwave frequencies at X-Band. While the original three-probe impedance measurement theory seemed to be potentially useful, in practice, problems cropped up with the applicability of the calibration procedure adopted. These problems were the main motivation behind the new theoretical approach and the embedded calibration procedure that was created. This approach determines the impedance of the unknown load without using the open load and matched termination, to determine the impedance of the unknown load while at the same time, our scheme takes into account the transitions and discontinuities at the test port. This report also gives an account of the system design, construction and testing, as well as an account of the control and calculation software. Although the results obtained did not match expectations a number of modifications are suggested which should eventually lead to system functionality.