This paper describes recent progress in the development of low-profile radiating-line antennas for producing circularly polarized CP radiation. Numerical studies of annular sector and log-spiral radiating lines have been done using a numerical electromagnetics code based upon patch basis functions. The relative merits and performance limitations of annular sector ANSERLIN, one-arm spirals, and two-arm spirals are discussed. The results of the computer simulations were used to choose parameters for some physical models. Measured performance is close to that predicted by computer. A limiting factor in achieving large bandwidths has been traced to the rather slow rate of attenuation of the current along the antenna arm. Much greater bandwidth has been obtained by placing an absorbing film between the radiating arm and the ground plane.
This article is from 'Proceedings of the Antenna Applications Symposium Held on 25-27 September 1991. Volume 1,' AD-A253 682, p404-433.