Planar Spiral Antenna 5 dBi Typ. Gain, 18-40 GHz Frequency Range RM-PSA1840-5

A planar spiral antenna is a classic frequency-independent antenna renowned for its ultra-wideband characteristics. Its structure consists of two or more metallic arms that spiral outward from a central feed point, with common types being the Archimedean spiral and the logarithmic spiral.

Its operation relies on its self-complementary structure (where metal and air gaps have identical shapes) and the “active region” concept. At a specific frequency, a ring-like region on the spiral with a circumference of about one wavelength is excited and becomes the active region responsible for radiation. As the frequency changes, this active region moves along the spiral arms, allowing the antenna’s electrical characteristics to remain stable over an extremely wide bandwidth.

The key advantages of this antenna are its ultra-wide bandwidth (often 10:1 or greater), inherent capability for circular polarization, and stable radiation patterns. Its main drawbacks are its relatively large size and typically low gain. It is widely used in applications demanding ultra-wideband performance, such as electronic warfare, broadband communications, time-domain measurements, and radar systems.