Vector Network Analyzer Error Model And Calibration Theory

S-parameters has been wildly used in describing characters of microwave network and is important part of teaching, researching and experiment in the microwave field and the development of CAD, S-parameters become the main basis of microwave CAD. Therefore, the precise measurement of S-parameters has developed to be main topic and direction encountered by microwave field and is a necessary tool in the teaching and research. The microwave network analyzer is main instrument to measure S-parameters. Because of all kinds of errors existing in the measurement system which could result in bias between measure value and the truth. In order to remove the system errors, the Vector Network Analyzer (or VNA) must be calibrated before measuring the devices under test. Based on detailed analysis on architecture, working principle, signal flowing directions as well as measurement methods of the VNAs, this article sets up the 8-Errors Module, introduces two error correction methods using standard calibration kits: the OSL (OPEN+ SHORT+LOAD) method and the SLT(LOAD+THROUGH+SHORT) method. We found that this module can simplify the calculation in calibration. And we validate it in our experiments. Traditional calibration methods are done by using standard kits (e.t. standard SHORT, OPEN, MATCH) provided by instrument manufactures, calibration function set in and standard kits data stored in instruments. However, manufactures always provide standard kits with coaxial ports, while the port types of devices under test varies. This article also introduces 12-errors-module and 8-errors-module nonstandard error correction methods using SHORT and transmission LINE as calibration kits. Usually, the calibration kits SHORT and transmission LINE can easily be realized in practical measurement situations. The error correction methods given in this article can cut down the calculation work and speed up the VNA measurements. For these reasons, the measurement result can get closer to the dynamic performances and satisfy real time measurement requirements. Compared to traditional calibration theories, the 8-Errors calibration can meet the demand of high speed and high precision field situation, especially in the realm of military electric measurement. This module can also be of great value to the modularization of the VNA in the future. The nonstandard calibration methods given in this article give up the expensive standard calibration kits and solve most related problems in measurement practices. This article is also of great value to measurement on devices with various port types.