The design of a Rotman lens

A Rotman parallel-plate-lens with a linear array antenna preceeded by a multibeam forming network to excite several orthogonal beams simultaneously, is described. This lens type is chosen for its relatively few phase errors. The lens principle is based upon electrical path length differences between input and output-ports, the beam direction being frequency independent. The design is executed in microstrip with a 10.5 substrate permittivity, using computer facilities to fix contours and ports accurately. The design is meant for the 8 to 12 GHz frequency-band. Measurements show good agreement with the theory, although standing wave ratios of the input-ports are still too high. The antenna is developed for electronic countermeasures.