Design considerations for millimetre wave lens antennas

The operational background and some of the possible single and dual lens antenna options for use in a millimetric sensor with approximately 3° beamwidth have been examined. A particular single lens antenna design gave a scan of more than ±3 beamwidths and compatibility with conical scan, beam broadening and monopulse operation. A dual lens antenna design was operated both with a single feed horn and with a rectangular matrix of plain waveguide radiators (with potential application in real time imaging). Good scan characteristics were obtained out to ±6 beamwidths with the single feed horn but the matrix feed assembly needed a group of elements to be fed in phase before equivalent performance could be obtained. The aim of the work was to simulate feeding the lens antenna with a monolithic array and whilst an array of waveguides can not accurately model all the properties of a monolithic array they are considered sufficiently representative to indicate some of the compromises that may have to be made.