A Controlled Reception Pattern Antenna Array With Dual-Mode Circular Microstrip Antenna Elements for Increased Angular Availability

Planar-controlled reception pattern antenna (CRPA) arrays suffer from low null resolution at low elevation angles, which results in a diminished angular space available for reception. The null resolution becomes even worse as the array aperture size is shrunk in modern compact CRPAs. Nonplanar arrays have been used to address this issue, but they are high profile and bulky. A novel planar solution, specifically suited for compact arrays, is proposed in this communication. We show that by utilizing concentric dual-mode TM₁₁-TM₂₁ circular microstrip antenna elements in an array, an angular availability similar to a spherical array can be achieved. This is demonstrated by studying the array nulling performance in many Monte Carlo trials with randomly polarized interferers, where the adapted array patterns are computed using a simple null-steering algorithm.