Superconducting superdirectional antenna arrays

Electrically and physically small antenna arrays in a superconducting state can be used to obtain a radiation pattern of moderate directivity with high radiation efficiency. The loss resistance is reduced by several orders of magnitude, and superdirectivity is achieved with a loop antenna array. Radiation beamwidth depends upon only the number and relative phase of the loops and is independent of array size. Experimental results show efficiency of an electrically small two loop antenna array increases 250 times when placed in a liquid helium environment. Its directive properties compare well with theoretical predictions.