Optimizing the radiation pattern of sparse periodic two-dimensional arrays

A method for reducing the number of elements in a 2-D array while minimizing degradation of the beam forming properties is described. The method relies on selecting a different arrangement of elements when the array is transmitting energy and when the array is receiving energy. The transmit and receive aperture functions are chosen to minimize the difference between the effective aperture of the sparse array and the effective aperture of a desired dense array. In a companion paper [see ibid vol. 43, pp. 7-14, 1996], the design of sparse linear arrays using the effective aperture method was described. Here, we extend this method to the design of 2-D arrays. Comparisons of the radiation patterns of a dense 2-D array and sparse 2-D arrays with random and periodic element spacing are given. Using the effective aperture method, we show that the number of elements in a 64/spl times/64 2-D array can be reduced by more than six times, and the elements in a 128/spl times/128 array can be reduced by more than 12 times, with little effect on the beam forming properties of the arrays.