A General and Effective Mode Filtering Method for the Suppression of Clutter in Far-Field Antenna Measurements

The use of mode filtering to improve the quality of antenna measurements taken in non-anechoic environments is well known, [1, 2, 3, 4, 5]. In the far-field case [6, 7, 8], it has been shown that it is possible to use standard cylindrical nearfield theory [8] to implement the necessary mode filtering using a singularly polarized, great circle, far-field pattern cut consisting of amplitude and phase data. The careful verification of this technique using a compact antenna test range (CATR) was reported in [7, 8] however that implementation had, as a prerequisite, the need to acquire the far-field data on a monotonic and equally spaced pattern abscissa. In many instances this is not convenient or perhaps impossible. This paper presents a recent development which allows data to be processed rigorously when having been acquired using an unequally spaced angular abscissa. This paper sets out the novel, far more sophisticated, algorithm together with results of actual range measurements that were processed using this new technique.