An electrically small, ultra-wideband, top-loaded monopole antenna 20 comprises a ground plane 24, a coaxial feed 21 and an antenna element. The said antenna element comprises a cylindrical conductive case 26 and an extended portion 23a of the conductive core 23 of the coaxial feed 21. The cylindrical conductive case 26 is isolated from the ground plane 24 by a first dielectric material 29. The said case 26 is electrically connected to a structure 27 which are arranged to provide top-loading of the extended portion 23a of the conductive core 23. The said case 26 includes a second dielectric material 28 which electrically insulates the conductive core portion 23a from the said case 26 and the said structure 27. The coaxial feed 21 has an outer conductor 22 connected to the ground plain 24 and an inner conductor core 23 which extends through the first dielectric material 29 and into the second dielectric material 28 and the case 26. The said structure 27 may be a conductive disc. Radial fins or high impedance surfaces may be formed around the antenna 20. The antenna 20 may be used in array formations where the antennas may be of different sizes. The small antenna may provide a large matching bandwidth with reduced lossy effects suitable for use within mobile handsets and computer networks.
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