Superdirective property of the microwave axicon

The microwave axicon considered is the analogue of the simple optical axicon. It consists of a dielectric cone of large semivertex angle placed in the aperture of a focused antenna. The effect shown both theoretically and experimentally is to reduce the beamwidth of the far-field radiation pattern to about two-thirds of the original value with an increase in the sidelobe level. In certain conditions this can give rise to a narrower pattern than that from a uniformly illuminated aperture of the same diameter.