Scan blindness mitigation using photonic bandgap structure in phased arrays

Electronically scanned phased array antennas have been in use for many years for such applications as search and surveillance, tracking, and remote sensing. They offer fast beam switching and multi-beam operation, but are subject to scan blindness due to the effects of mutual coupling between elements. Scan blindness is an undesirable decrease in array gain at specific frequencies and angles. The blindness comes about when the array structure is capable of supporting a forced surface wave model. A novel substrate will be investigated which may eliminate scan blindness by cutting off these surface wave modes. Researchers have been investigating the properties of a periodic dielectric structure exhibiting a photonic bandgap since 1987. This photonic bandgap structure prevents electromagnetic propagation in any direction (in two dimensions for the 2D structure). The geometries examined have been two and three-dimensionally periodic with lattice structures typically being triangular or rectangular. The investigation of the photonic bandgap structures had been confined to theory until about 1994 when researchers constructed and characterized the properties of a finite 2D structure. Recently, researchers have suggested using the photonic bandgap structure as a substrate. This paper investigates the use of a photonic bandgap substrate, PBGS, to reject the surface wave and eliminate scan blindness. To support the theory, experimental data will be presented comparing the scan performance of an array on a PBGS and an array on a conventional homogeneous substrate.