Quadifilar helix antenna with cage for axial ratio improvement and wide beam characteristic

A simple and novel technique to improve the axial ratio of quadrifilar helix antenna (QHA) and widen its beam width is presented. By adding a cage which consists of a loop and 4 sticks, the axial ratio performance is greatly decreases at the low elevation and the beam width is widened. An antenna for CNSS (Compass Navigation Satellite System, 2.492GHz) application is realized based on the technique. The axial ratio is below 4dB at the elevation of 5° and the 3dB beam width increases to about 180°. Measured results are presented to validate the concept.