Design and Experimental Results of a Spherical Antenna Array for a Conformal Array Demonstrator

Conformal antenna arrays fitted to non-planar surfaces on parts of modern aircrafts, vehicles or ships are considered an attractive alternative for many applications whereas planar arrays or reflector antennas have definite drawbacks. Some of the potential advantages are improved aerodynamics, increased payload, large field of view (LFOV) and low observability (LO). However, the usage of conformal array technology in commercial applications is still comparably rare. Recent examples of antenna arrays on curved apertures are typically of cylindrical shape but only exhibit a weak degree of curvature. The present paper describes the development of a spherical antenna array with 95x3 antenna elements, a diameter of 300 mm and an opening angle of 112deg . Since the number of antenna elements on a planar or curved antenna aperture required for high directivity and two-dimensional beam steering can easily become very large, especially if an element spacing around half the free space wave length is required, the antenna elements are arranged in sub-arrays, each carrying 3 circularly polarized patch antennas at a centre frequency of f = 9.5 GHz and a phase corrected feed network on a common substrate. The sub-array is suited for easy integration into antenna arrays with double curved aperture and can be seen as a trade-off between antenna gain vs. beam granularity. Experimental results on antenna matching and radiated far field patterns as well as measured beam forming results will be presented.