Current Interests

In recent years Andrew has been working in the Nano & Multi-functional Materials group, where he is has developed 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 instrument has been used to measure the properties of ceramics, minerals, and graphene. Collaborative work under an international European Metrology Research Programme (EMRP) is continuing the development of this instrument.

Biography

Andrew Gregory received his BSc degree in Physics from the University of Manchester before taking a position of employment at NPL. During most of his time at NPL he has worked in the RF and Microwave Group. Microwave Vector Network Analysers (VNAs) first became available at about the time that he joined NPL, and he has worked extensively with these instruments for obtaining accurate measurements of S-parameters and Q-factor. His main research interest has been developing methods for measuring dielectric properties of materials traceably using VNA-based techniques. He has worked on 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 that is now used worldwide. 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 it is in agreement with values that are published in international standards. For such measurements, reference data is needed for calibrating and checking instruments such as coaxial sensors/ coaxial probes.

Andrew is a Member of The Institute of Physics and a Chartered Physicist.

Selected Publications

• Tables of the Complex Permittivity of Dielectric Reference Liquids at Frequencies up to 5 GHz
  A. P. Gregory and R. N. Clarke
  NPL Report MAT 23 (2009) ISSN 1754-2979
• A Review of RF and Microwave Techniques for Dielectric Measurements on Polar Liquids
  A. P. Gregory and R. N. Clarke
  IEEE Trans. Diel. and Elec. Insulation, 13 (4) pages 727-743 (2006)
• Dielectric metrology with coaxial sensors
  A. P. Gregory and R. N. Clarke
  Meas. Sci. Technol., 18, pages 1372-1386, 2007
• Traceable Measurement Of Dielectric Reference Liquids Over The Temperature Interval 10 ºC - 50 ºC Using Coaxial-Line Methods
  A. P. Gregory, R. N. Clarke and M. G. Cox
  Meas. Sci. Technol., 20, article 75106 (2009)
• Traceable Measurements of the Static Permittivity of Dielectric Reference Liquids over the Temperature Range 5 – 50 ºC
  A. P. Gregory and R. N. Clarke
  Meas. Sci. Technol., 16, pages 1506-1516 (2005)

Contact details

E-mail: andrew.gregory@npl.co.uk
Tel: 020 8943 6430