Inadequacy of the Rayleigh range criterion for superdirective arrays

The paper demonstrates that conventional antenna test criteria cannot be applied to a superdirective array and that the concept of the Rayleigh range is no longer valid. The dominant factor is the tolerance of the superdirective array function which generates the required radiation pattern. A superdirective radiation pattern with a beamwidth slightly less than in the case of uniform illumination, but with much greater sidelobe suppression, calls for a disproportionate increase in the modified Rayleigh range. These effects must be taken into account in the measurement of superdirective radiation patterns in standard antenna test facilities and in the deployment of a superdirective array.