Peter Clarricoats made major contributions to applied electromagnetics in two distinct fields —microwave and optical waveguides, and microwave antenna feeds. In a sustained series of analytical papers, Peter established the theory which has since been widely used in the context of optical fibres, of electromagnetic propagation on dielectric and ferrite structures. In the course of this he made two wholly unanticipated discoveries: the fact that such structures can, under some conditions, support ‘backward waves’ — waves in which the energy travels in a direction counter to the propagation of the phase fronts; and the fact that under certain conditions, guides can propagate complex modes — modes which are neither purely propagating nor purely evanescent. The performance of large antennas used in satellite communications and in radio astronomy depends critically on the form of the ‘feed’ — the radiating source which illuminates the main antenna mirror. Peter was one of the first to recognise the radical improvements which stem from the use of a corrugated horn, and presented the first detailed theoretical analysis of its action.
Professor Peter Clarricoats CBE FREng FRS died on 17 January 2020.