Toroidal antenna
A Torusantenne is a parabolic antenna , wherein the for the reflector forming parabola has not been rotated about the axis of the main beam direction, but about an axis which is perpendicular thereto. This creates a reflector in the shape of a circular arc .
technical description
The directional characteristic (and consequently the antenna gain ) for each transmitting / receiving device is based only on a small area of the reflector surface. The size of this area is limited by the directional characteristics of the primary radiators (mostly horn radiators ). The effective antenna area for the respective channel is smaller than an approximately oval parabolic antenna with a diameter roughly the smaller dimension of the torus antenna. In relation to the total area, the antenna aperture is rather small. Overall, however, multiple use of the reflector surface is achieved because the individual areas can overlap. Since a focal line is generated instead of a focal point, the losses due to aberration are somewhat greater than with a parabolic antenna.
In contrast to a parabolic antenna with a multifeed holder , none of the positions for the primary radiator are preferred with the torus antenna.
Applications in radar and for terrestrial transmission
In the 1950s, the US armed forces procured the AN / FPS-50 radar system, which used torus antennas for early warning of ballistic missiles. The radars initially worked in the UHF range and, after a conversion, in the L band. The reflectors are 50 m high and 120 m long, with only half a parabolic arc being formed and the line of focal points located just above the earth's surface. By almost tripling the frequency, the torus antennas were much more efficient after the upgrade. The 80 primary radiators were mounted next to each other in different positions. This covered a side angle range of 40 ° per antenna. The radar was one of the last to use fixed torus antennas to turn direction.
An antenna system built in the 1960s based on this principle at the former cable headend in Cressey (California) , which received television signals from the San Francisco region around 160 km away, has still been preserved for terrestrial transmission in the ultra-short wave range . Ten towers around 27 meters high and erected in a circular arc around 110 m long carry horizontally stretched metal wires and thus form the reflector.
Application for satellite communication
Torus antennas are used nowadays to keep connections with several geostationary satellites at the same time in the microwave range with only one antenna . For this purpose, they are equipped with several primary antennas, which are aimed at different areas of the toroidal reflector ( multifeed ).
An approximately 80 m wide antenna of this type has been in the Owidiopol-2 facility near Welykodolynske in the Ukraine since around 1987 . Such antennas were later installed by the NSA in various countries to reduce the cost of monitoring satellite communications . These antennas are also used by cable network operators .
Smaller toroidal antennas also exist in the field of entertainment electronics , in order to be able to receive the signals of several television satellites with only one immovable reflector . These receiving antennas can also be equipped with a secondary reflector that works on the principle of a Cassegrain antenna and is also toroidal in shape. This allows the necessary distances between the LNBs to be increased so that satellite positions that are close to one another can also be served. Both reflectors are matched to one another in such a way that greater efficiency is made possible.
literature
- Alan GP Boswell: The parabolic torus reflector antenna. In: Marconi Review. 41, 1978, pp. 237-248.
- Biao Du, Edward KN Yung, Ke-Zhong Yang, Shun-Shi Zhong: Design of multibeam parabolic torus reflector antennas. In: Microwave and Optical Technology Letters. 27, 5, 2000, pp. 343-347.
- Kenneth S. Kelleher: A new wide-angle microwave reflector. In: Tele-Tech & Electronic Industries. 12, 6, 1953, pp. 98-99, 168-169.
- Yahya Rahmat-Samii, Reflector Antenna Developments: A Perspective on the Past, Present and Future, 2015, IEEE Antennas and Propagation Magazine, Volume 57, Issue 2, ISSN 1045-9243 , pp. 85-95.
Web links
Individual evidence
- ↑ Merrill Skolnik: Radar Handbook, Third Edition McGraw-Hill Professional, 2008, ISBN 978-0-07-148547-0 ( online PDF, p. 554. , accessed May 19, 2016)
- ↑ Documentation BMWES at www.globalsecurity.org
- ↑ Coordinates 37 ° 25 ′ 39 ″ N, 120 ° 39 ′ 3 ″ W
- ^ Neil McLain: Broadband networks part 29. In: SBE Chapter 24 Newsletter. March 1999, p. 6. ( online PDF ( memento of the original from October 23, 2007 in the Internet Archive ) Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this note. , accessed on May 19, 2016)
- ↑ Coordinates 46 ° 19 ′ 45 ″ N, 30 ° 32 ′ 26 ″ E
- ↑ Desmond Ball, Duncan Campbell, Bill Robinson, Richard Tanter: Expanded communications satellite surveillance and intelligence activities utilizing multi-beam antenna systems. NAPSNet Special Report, May 28, 2015
- ↑ Multiple-beam antennas. The New York Times, August 13, 1981.
- ↑ in English called shaping technique , see: Constantine A. Balanis: Antenna Theory. Analysis and Design. John Wiley & Sons, New York 2005, ISBN 0-471-66782-X , p. 895 (in online PDF p. 852, accessed on May 18, 2016)
