The circular travelling-wave antenna

The circular traveling-wave antenna consists of a conductor formed into a circle, which is fed at one point and so terminated at the diametrically opposite point that only a traveling wave exists cn the antenna. Consequently the beam of the antenna can be steered in azimuth by moving the feed point and the load point around the circumference of the circle. Azimuthal radiation patterns have been calculated for antennas having circumferences of 3, 4, 5, and 6 wavelengths. In addition, experimental patterns have been obtained for antennas having circumferences cf 1.75 tc 14 wavelengths. The patterns for both the radiation intensity and the -polarized component of the electric field display a single main lobe in the direction of the load end of the antenna, with rather high-level side lobes. In an attempt to obtain radiation patterns having lower side lobe levels, the effect of using two and three concentric circular traveling-wave antennas of different radii has been investigated. The patterns of these antennas, which have diameters of less than two wavelengths are comparable in side-lobe levels to those obtained with rhombic antennas.