A spiral antenna is a type of radio frequency antenna shaped as a spiral,[1]: 14‑2 first described in 1956.[2] Archimedean spiral antennas are the most popular, while logarithmic spiral antennas are independent of frequency:[3] the driving point impedance, radiation pattern and polarization of such antennas remain unchanged over a large bandwidth.[4] Spiral antennas are inherently circularly polarized with low gain; antenna arrays can be used to increase the gain. Spiral antennas are reduced in size with its windings making it an extremely small structure. Lossy cavities[5] are usually placed at the back to eliminate back lobes, because a unidirectional pattern is usually preferred in such antennas. Spiral antennas are classified into different configurations: Archimedean spiral, logarithmic spiral, square spiral, etc.
- ^ Johnson, Richard C.; Jasik, Henry, eds. (1961). Antenna Engineering Handbook (Second ed.). ISBN 0-07-032291-0.
- ^ Orr, William I. (1976). Beam Antenna Handbook (5th ed.). Radio Publications. pp. 185–186.
- ^ Kraus, John (1988). Antennas (2 ed.). McGraw-Hill. p. 697. ISBN 0-07-035422-7.
- ^ Mayes, Paul E. (1992). "Frequency-independent antennas and broad-band derivatives thereof". Proceedings of the IEEE. 80 (1): 103–112. Bibcode:1992IEEEP..80..103M. doi:10.1109/5.119570.
- ^ Hill, David A.; Ma, M. T.; Ondrejka, Arthur; Riddle, Billy F.; Crawford, M. L.; Johnk, Robert T. (September 1993). "Aperture-excitation of electrically-large, lossy cavities". NASA STI/Recon Technical Report N. 1361: 31683. Bibcode:1993STIN...9431683H.