Generalised approach to the design of narrowband antenna array processors with broadband capability

A few techniques have been proposed for designing narrowband antenna array processors with a specific broadband capability. In one approach the array processor is designed by imposing on it a set of linear constraints. This set consists of two parts. In the first part, the processor is constrained to have unity gain in the desired look direction at the centre frequency of the frequency band of interest. In the second part, an additional set of linear constraints is used to ensure that the gradient (first-order derivative) of the frequency response of the processor can be approximated to zero, in the minimum meansquare sense, over a specific frequency band. In the paper, it is shown that this approach can be extended to higher orders (n orders) so that other (n-1) sets of new linear constraints can be obtained. With the extended higher order constraints, a generalised formulation is arrived at for this class of constraints. Computer simulation results are given to show the performance characteristics of a high order processor using linear array geometry