On properties and design of nonuniformly spaced linear arrays [antennas]

The properties of nonuniformly spaced linear arrays (and nonrecursive filters with nonequidistant taps) are studied. It is shown that in many cases the element spacings of the optimal solution are integer multiples of a suitably chosen basic spacing. This significantly simplifies the design procedure since the arrays can be designed as thinned uniformly spaced arrays, thus avoiding complicated nonlinear optimizations. A simple thinning procedure is used. Another design procedure based on Nth-band FIR (finite-impulse response) filter concepts is introduced, making possible the use of standard FIR filter design methods for nonuniformly spaced arrays; illustrative examples are included. The results compare favorably to published results for nonuniformly spaced designs that did not exploit the special properties of uniform or discrete nonuniform arrays