Compact antennas are usually one-quarter of the wavelength being transmitted, but engineers at Virginia Tech (USA) are claiming a 2.5-fold reduction in the size of an ultra-wideband (UWB) antenna. The compact UWB antenna (CUA) has a curved multi-element shape twisting around the inside of a spherical envelope with a diameter just one-tenth of the wavelength being transmitted.
Unlike conventional AM, FM or similar encoding schemes, UWB uses pulsed transmissions that encode information by generating radio energy at specific times over large bandwidths. The technique is called pulse position or time modulation.
According to the designers, the antenna has a 10-to-1 instantaneous bandwidth, and it could be used for frequency-domain, multiband and multichannel applications, as well as time-domain or pulsed applications. The antenna is claimed to achieve nearly optimal UWB performance for short-range transmission of low energy, high-bandwidth data such as video signals. Although other 10:1 bandwidth antennas exist, such as spiral and log-periodic designs, he said that they do not work well in radar applications, but the CUA can be used in pulsed radar systems.
The key to the CUA is that it utilises a spherical volume to pull in nearly the maximum amount of signal power that is theoretically possible. The CUA takes advantage of the underlying theory of UWB antennas by employing arms that twist around a metallic central core with a relatively constant distance between the core and the arms. The arms could be etched on the inside of a radome in low-cast applications, or they could be constructed from curved wires or tubing.
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