Improving efficiencies of superdirective arrays of monopoles over lossy groundplanes by using superconducting disc overlays

Electrically small perfectly conducting superdirective monopole arrays above lossy metal groundplanes are analysed at 500 MHz using a moment method incorporating Sommerfeld terms. It is shown that significant improvements in efficiency are obtained when small perfectly conducting discs, which can be realised using high-temperature superconductors, are attached to the monopole bases, compared with monopoles being directly connected to groundplanes