Research On Measurement Uncertainty Of Vector Network Analyzer

The vector network analyzer(VNA)has,for almost a hundred years,found frequent application within microwave measurement.It is well known that measurement instruments can hardly perform ideally,especially for the VNA,which operates from several MHz to hundreds of GHz,the perfect characteristics and excellent consistency cannot be ensured within such a wide frequency range.These all lead to the measurement uncertainty of VNA.The measurement uncertainty of VNA reflects the inaccuracy of the measurement result due to the existence of the measurement error,and is an index of the reliability of the measurement result.The main work of this thesis includes as follows:1)In light of the hardware topology of VNA,the calibration technique based on 12-term error model and 8-term error model is studied.According to the calibration standards used in calibration process,the calibration techniques such as SOLT(Short-Open-Load-Thru)and TRL(Thru-Reflect-Line)methods are depicted in detail.2)A measurement uncertainty evaluation method of two-port VNA with four measurement channels is derived.For the 8 term error model,the influence of non-ideal calibration standards on S-parameter measurement is shown in the analytical form.3)A measurement uncertainty evaluation method of two-port VNA S-parameters introduced by random errors is presented.In this method,four categories of measurement error are taken into account,including residual system error,system's nonlinearity,random error and environment conditions of the measurement,in which more error sources are considered than current uncertainty evaluation methods.4)The measurement uncertainty evaluation method of VNA S-parameter introduced by non-ideal standards is extended to multi-port VNA.Using the concept of generalized node and port extension,the complex four-port 16-term error model is reduced to the generalized eight-term error model.All the coefficients in signal paths are replaced by the complex square matrices and the nodes correspondingly become complex vectors.Finally,the uncertainties of four-port VNA S-parameter measurements applying the TRL calibration method are shown in the form of matrix.