Crosspolarisation characteristics of linear comb-line microstrip antennas

Microstrip antennas are a subject of increasing interest in the microwave antenna field, and the comb-line antenna is particularly attractive for medium to low sidelobe level operation. However, the crosspolarisation properties of such structures have not been discussed previously, although these are of importance where the suppression of sidelobes in all polarisation planes is required. A mainly experimental investigation is described into the crosspolarisation characteristics of comb-line antennas, and criteria for crosspolarisation suppression are derived for particular board characteristics at 4.3 GHz.