On the use of a conical cornucopia antenna to reduce EMI

The wide-angle radiation form a prime-fed parabolic reflector antenna and the associated EMI (electromagnetic interference) it produces can be greatly reduced by constructing the antenna in the form of an absorber-lined conical cornucopia (CC). Measured RPEs (radiation pattern envelopes) are inspected for the case where all antennas have about a 10-ft diameter and 43-dBi gain at 6 GHz and typify the type of WAR (wide-angle radiation)-RPE improvement achievable if scaled to other bands/sizes. It is shown that the CC's RPEs for angles from about 10 full half-power beamwidths (here 10°) and beyond, and most especially from about 30 full half-power beamwidths (here 30°) and beyond, are vastly superior to those of either the standard or improved (UHX/UMX) parabolic dishes. Indeed, it is seen that the CC's RPE levels are about 95 dB down from on axis for angles greater than about 90°. In other words, the CC's wide-angle RPE is about 40 dB lower than that of a standard parabolic-dish antenna of the same gain. These very low WAR levels then greatly mitigate the EMI to adjacent microwave routes in terrestrial radio relay applications