Andrew Gregory received his BSc degree in Physics from The University of Manchester before taking up employment at NPL. During most of his time at NPL, he has worked in the RF & Microwave Group. Microwave Vector Network Analysers (VNAs) first became available at about the time that Andrew joined NPL, and he has worked extensively with these instruments for obtaining accurate measurements of S-parameters and Q-factor.
Andrew's main research interest has been developing methods for measuring dielectric properties of materials traceably using VNA-based techniques. Examples of past projects are:
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A programme of measurements to obtain traceable complex permittivity data for common polar reference liquids (e.g. methanol and ethanol), which produced reference data with a comprehensive uncertainty analysis. These are published in an NPL report (MAT 23) which is used widely. Traceable data is needed for calibrating and checking instruments such as coaxial sensors/coaxial probes. An example of its application is in health and safety measurements of cell phone dosimetry, where it is required that the complex permittivity of tissue simulant materials is measured to ensure that they are in agreement with values that are published in international standards.
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Development of a Near-Field Scanning Microwave Microscope (NSMM) that is capable of obtaining images of the dielectric permittivity and loss of polished samples on a micron scale. This was partly funded by the international European Metrology Research Programme (EMRP).
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Improving VNA-based methods for measuring complex permittivity to make measurements traceable and enable evaluation of uncertainty. He devised a Monte Carlo method for evaluating the uncertainty of coaxial sensors/coaxial probes.
Andrew is a Member of the Institute of Physics and a Chartered Physicist.
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Current Interests
Andrew now works in the Electromagnetic Technologies Materials Group, where he oversees an extensive range of facilities for measuring complex permittivity in the frequency range 1 kHz to 144 GHz. He is also a researcher in a number of projects funded by the European Metrology Programme for Innovation and Research (EMPIR). These include a project entitled 'Traceability for Electrical Measurements at Millimetre-wave and Terahertz Frequencies for Communications and Electronics Technologies' (TEMMT).
Email Andrew Gregory