Dr Laurence Stant

Vector Network Analysers (VNA) are used extensively for many types of measurement that are made at frequencies ranging from a few kilohertz to at least one terahertz. At radio and microwave frequencies, there are well-established methods for assessing the quality and integrity of these measurements, when they are made in coaxial lines. These methods are usually based on determining the size of residual errors that remain in the VNA after calibration. However, to date, the performance of these methods has not been investigated in rectangular waveguide, and, at higher frequencies (i.e. at millimetre- and submillimetre-wave frequencies). This paper investigates the application of one of these techniques to VNAs configured for waveguide measurements at microwave, millimetre- and submillimetre-wave frequencies. Typical values of residual errors in voltage reflection coefficient (VRC) obtained over microwave and millimetre-wave frequency ranges were between 0.002 to 0.021 linear units. Submillimetre-wave frequency waveguide configurations were found to exhibit significantly larger residual errors and are being investigated further to assess whether the ripple extraction technique is valid at those frequencies. Residual error values obtained in this investigation are considered representative for this technology and so can be used by other users of waveguide VNAs to compare with values obtained on their own systems, therefore helping to verify the performance of their systems.

The Joint Committee for Guides in Metrology (JCGM) publishes and maintains reference documents relating to general aspects in metrology. Working Group 1 of the JCGM is responsible for the Evaluation of Measurement Data series of documents that gives information for evaluating and expressing uncertainty in measurement. This paper compares several methods for evaluating measurement uncertainty that are described in these documents. Emphasis is given to situations where more than one input quantity is measured simultaneously. This leads to an investigation into how these methods perform when these quantities are high-frequency electromagnetic scattering parameters. It is shown that for measurements involving a large number of input quantities, such as those involving microwave scattering parameters, the required number of observations for the approach given in the GUM Supplements to work can be prohibitively large.

Vector network analysers (VNAs) are used extensively for measurements that are made at frequencies ranging from a few kilohertz to at least one terahertz. At radio and microwave frequencies, there are well-established methods for assessing the quality and confidence of these measurements, when they are made in coaxial lines. These methods are usually based on determining the size of residual errors that remain in the VNA after calibration. To date, the performance of these methods has not been investigated in rectangular waveguide, and, at millimetre- and submillimetre-wave frequencies. This study investigates the application of one of these techniques for waveguide measurements at microwave, millimetre- and submillimetre-wave frequencies. Typical values of residual errors obtained over these frequency ranges are given, and range from 0.001 to 0.024 linear units up to 220 GHz. Above this frequency, the technique is shown to underestimate some residual errors. The values reported up to 220 GHz are considered representative and so can be used by other users of waveguide VNAs to compare with values obtained on their own systems; therefore, helping to verify the performance of their systems.