The design of shared aperture antennas consisting of differently sized elements

A consistent strategy for the design of finite array antennas consisting of differently sized radiating elements is discussed. In view of increasing the total bandwidth of the antenna system, while maintaining a low mutual coupling between the elementary radiators, sparse subarrays, operating at adjacent frequency ranges, are interleaved on a common (shared) aperture. The sparse architectures are designed using a combinatorial method that ensures an acceptable behavior in the side-lobes region in conjunction with a narrow beamwidth. The effect of the mutual coupling between identical and differently sized elements is accurately evaluated and is accounted for in predicting the performance of each individual radiator. The concept is illustrated by designing a shared aperture antenna consisting of two interwoven subarrays that jointly cover a fractional bandwidth of 14% in the X-band. Cavity-backed, stacked-patches antennas with coaxial feeding are used as elementary radiators.