University Reader in Experimental Radio Physics
Vice Master of Downing College and Director of Studies in Physics
Cambridge CB3 0HE
I am a physicist by training, and a radio astronomer by trade. A recent area of research has been measuring and investigating tiny fluctuations in the temperature of the cosmic microwave background radiation, which bathes us all with its feeble remnant echo of the fireball of the birth of the Universe. On another front I had also been using long-wavelength radio telescopes to study the older parts of radio galaxies, gigantic structures much of which are only visible in the radio wavebands. One of the things you need to have in any instrument is an aperture size which is hugely bigger than the wavelength. I was using a wavelength of 12 feet so I needed an instrument a thousand miles or more across. The only solution was to build a radio telescope in two parts, a large antenna near Cambridge and a portable element packed onto a trailer and towed by a motor caravan. It was easy enough to set up the portable end in a farmer's field in the South of France, but now I needed to find its position within a precision of 2 feet. I devised a method based on measuring the signals from public broadcast radio stations (like Radio Four FM) and this in turn led to my setting up Cambridge Positioning Systems Ltd. in order to exploit the method commercially on mobile phones. The technology combines measurements from GPS satellites with those of the network itself to provide positioning in all environments - inside buildings where satellite signals are very weak as well as outside. My current research includes invetigating how the environment affects the propagation of radio waves, especially in dense urban areas.
Microwave background astronomy, interplanetary scintillation, navigation and tracking systems.
Pratt, A. R., Faragher, R. and Duffett-Smith, P.J. "Fine Time Aiding and Pseudo-Synchronisation of GSM Networks". Institute of Navigation National Technial Meeting, Monterey, USA, January 2006.
Duffett-Smith, P. J. and Hansen P. "Precise time transfer in a mobile radio terminal". Institute of Navigation National Technical Meeting, San Diego, USA, January 2005.
Tarlow, B. J., Bartlett, D. W., and Duffett-Smith, P. J. "High accuracy network positioning technology for mobile phones in GSM and 3G". Mobile Location Workshop (MLW 2004), Athens, Greece, May 27-28, 2004.
O'O'Sullivan, C.M.M., Yassin, G., Woan, G., Scott, P.F., Saunders, R., Robson, M., Pooley, G.G., Lasenby, A.N., Kenderdine, S., Jones, M.E., Hobson, M.P. and Duffett-Smith, P.J. "A search for primordial anisotropies in the CMBR: First observations at 13.5 GHz with the CAT". Mon. Not. R. astr. Soc., 274, 861.
Duffett-Smith, P.J. and Woan, G., 1992. "The CURSOR radio navigation and tracking system". J. of Navigation, 45, 157-165.
Woan, G. and Duffett-Smith, P.J. "Terrestrial transmitters as phase calibrators in disconnected interferometry". Astr. Astrophys., 208, 381-384.
Woan, G. and Duffett-Smith, P.J., "The structure of Cassiopeia A at metre wavelengths". Mon. Not. R. astr. Soc., 243, 87-96.