Statistical method for wideband calibration of vector network analysers based on parameter modeling of standards

Aim of project
The project is aimed at enhancement of calibration applied for vector network analysers, especially at low and very high frequencies. Its main task regards development of a new broadband technique for calibrating such analysers, in which one may more extensively utilise one-port impedance standards with high reflection coefficients. Using a new measurement model, the technique enables determining both systematic error terms of the analyser and electrical characteristics of the standards. The new model of measurement system is complex and accounts not only for the relationships between measurement results at each frequency but also at various frequencies. Thus, it combines a typical model for systematic analyser errors with a new parametric model describing frequency dependence of the reflection coefficient of the standards. This model refers to standards of the same design, based on uniform transmission line of unknown line length and terminated at unknown impedance (usually short or open circuit). With such a complex modelling in the frequency domain, the new approach outperforms the traditional techniques utilising the same calibration measurements, but independently at each frequency.

Expected results
The new method does not require electric parameters of the standards to be known, since they are identified from the calibration measurements made in situ in the system. By providing means for electrical characterisation of the standards, this method constitutes an alternative to the traditional approach based on expensive mechanical measurements. Consequently, its users can benefit from the use of multiple low-cost standards whose characteristics are partially known. In the millimeter wavelength range, the method may be an option to the multiline TRL method, considered today as a benchmark calibration. The new method will be implemented in software for automatic calibration of vector network analysers using standards based on typical wave guiding structures, e.g. coaxial and microstrip lines, coplanar waveguide and waveguide. The results will be published in scientific journals and at international conferences. Some solutions can be patented and commercialised.