4-arm Sinuous antenna

Image of the 4-arm Sinuous antenna.

The 4-arm Sinuous antenna is popular in military and civil applications like radar, direction finding and electronic-counter-measure systems or as a broad-band, polarization-agile feed in measurement systems. As is the case for all antennas in the planar-spiral family, the sinuous provides good broadband characteristics but has the added advantage that it is capable of simultaneously receiving signals of different polarizations in the same aperture with good isolation between the ports. The Sinuous antenna is often used in a cavity-backed configuration, though the cavity needs to be absorber-filled to maintain broad-band performance.