Radiating Elements for Wideband Electronically Scanned Arrays

The initial applications of active electronically scanned array antennas (AESA) in radar (and other) applications have been in areas where a narrow operating bandwidth (<10%) has been acceptable. However, although the cost of an AESA has reduced in recent years it is still a relatively expensive asset. Also, space on a military platform such as a fighter aircraft is at a premium. There is therefore a need to share AESA apertures between various functions. As a result, system requirements are emerging that demand much wider bandwidth AESAs (sometimes well in excess of 2:1). This paper briefly describes the rationale for wider band AESA antennas. It then describes the constraints that a wideband phased array places on a radiating element that would not apply to a free space antenna. The development of wideband radiating elements is then reviewed with particular reference to two state of the art papers that were recently published in the EMRS DTC held in July 2007.