Log Spiral Antenna 4dBi Typ. Gain, 0.2-1 GHz Frequency Range RM-LSA021-4

The log-spiral antenna is a classic angular antenna whose metal arm boundaries are defined by logarithmic spiral curves. While visually similar to the Archimedean spiral, its unique mathematical structure makes it a true “frequency-independent antenna.”

Its operation relies on its self-complementary structure (metal and air gaps are identical in shape) and its purely angular nature. The antenna’s active region at a specific frequency is a ring-shaped zone with a circumference of approximately one wavelength. As the operating frequency changes, this active region smoothly moves along the spiral arms, but its shape and electrical characteristics remain constant, enabling extremely wide bandwidth.

The key advantages of this antenna are its ultra-wideband performance (bandwidths of 10:1 or more are common) and its inherent capability to radiate circularly polarized waves. Its main drawbacks are relatively low gain and the need for a complex balanced feed network. It is widely used in applications requiring wideband operation, such as Electronic Countermeasures (ECM), broadband communications, and spectrum monitoring systems.