Spiral antenna

A spiral antenna is a type of radio frequency antenna shaped as a spiral,:  14‑2  first described in 1956. Archimedean spiral antennas are the most popular, while logarithmic spiral antennas are independent of frequency: the driving point impedance, radiation pattern and polarization of such antennas remain unchanged over a large bandwidth. 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 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.

Not to be confused with Helical antenna.
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