AbstractA 2‐turn helical antenna with small pitch angle between 0.6° and 3° has been studied as a radiation element of circular polarization waves in this article. The antenna with pitch angle 2° exhibits a 3‐dB axial ratio bandwidth of 9.8%, and the optimal axial ratio of 0.1 dB. When the pitch angle decreases to 0.6°, the 3‐dB axial ratio bandwidth and the best axial ratio are 5% and 0.15 dB, respectively. Variation of on‐axis axial ratio as a function of the straight wire height h has been computed, and the current along the helix is also given. Experimental verification of the antenna performance is presented. The antenna with low profile and high polarization purity characteristics is suitable for application of array antenna. © 2006 Wiley Periodicals, Inc. Microwave Opt Technol Lett 49: 17–19, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.22054