Improvements in and relating to radar

An antenna, or a method of forming an antenna, comprises: two or more substantially identical antenna sub-arrays 3A, 3B, each with a plurality of separate antenna radiating elements 6A, 6B connected to a common radio frequency RF signal input/output port 4A, 4B. The separate antenna elements 6A, 6B are connected to the RF signal input/output port 4A, 4B via respective RF signal power dividers 8A, 8B. A variance in values of the power splitting ratio, and/or of the input RF signal reflectivity, and/or of the phase balance of corresponding signal power dividers of the two or more antenna sub-arrays 3A, 3B is sufficient to provide a cancellation ratio exceeding 40dB. Alternatively, the separate antenna elements 6A, 6B are connected to the RF signal input/output port 4A, 4B via respective transmission paths 7A, 7B with a variance in values of the transmission path lengths of corresponding signal transmission paths of the two or more antenna sub-arrays which is sufficient to provide a cancellation ...