Verification of Waveguide Measurements Using 2-Port Standards

Verification standards are required to determine the accuracy of waveguide measurements on a Vector Automatic Network Analyzer (VANA). The use of such standards can also show the importance of using certain measurement techniques. This paper deals with waveguide two-port standards which are precision, quarter-wave sections of reduced height waveguide, for which two-port s-parameters can be accurately calculated. A comparison of measured and calculated data will be shown. Measured data showing the effects of using index pins for flange alignment, and of using measured values for the calibration standards instead of nominal values will also be presented. The emphasis of this paper is primarily on presentation of measured data and comparision of the measured to the calulated data of the two-port standards. Some techniques that can be used to improve the accuracy of waveguide measurements in general are discussed, as well as how to use the two-port standards to get a feel for the level of accuracy of two-port measurements. The following is an outline of the paper, which is broken into two sections: I. Errors not Related to 2-Port Standards A. Flange Repeatibility B. Nominal vs. Measured Values for Standards II. Using 2-port Standards A. Calculation of S-parameters B. Comparision of Calculated vs. Measured Data The first section has to do with errors not related to the two-port standards that can be analyzed before getting to the two-port measurements.