The paper presents a new set of constraints for controlling the beam pattern spatial derivatives of a broad-band element space antenna array processor. The constraints ensure that the beam pattern of the processor is independent of the choice of phase centre location. The results are applicable to arbitrary array configuration and arbitrary frequency response including a flat response. It is shown that in general, for the first-order case, the set of constraints is linear but, for the second-order case, the set of constraints is linear as well as quadratic. The paper then considers the flat response case in detail and presents a method for realising the quadratic constraint with two linear constraints. It is shown that, using these two linear constraints, the dependency of the beam pattern on the choice of the phase centre location cannot be totally eliminated but the effect has been very much reduced. As a byproduct, the new set of linear constraints also reduce the number of constraints required to achieve beam broadening for the exactly pre-steered broad-band processors. The paper also presents a method for optimising the beam pattern with respect to the phase centre location. Numerical results showed that the optimised version has a better performance in terms of maintaining the beam-width broadening and a capability of rejecting interference. However, the optimisation involves non-linear processing. This may make it unsuitable for on-line implementation.
|Number of pages||15|
|Journal||Journal of Electrical and Electronics Engineering, Australia|
|Publication status||Published - 1 Jun 1991|