Low-Profile Composite Helical-Spiral Antenna for a Circularly-Polarized Tilted Beam

A wire composite helical-spiral (CHES) antenna fed from the central point of its bottom is investigated, where the number of helical turns is selected to be extremely small (one turn). The CHES is designed such that it radiates a circularly-polarized tilted beam under the condition that the diameter of the CHES is smaller than that of a corresponding tilted-beam spiral antenna. It is found that the direction of the tilted beam in the elevation plane is not sensitive to a change in frequency. The input impedance and the gain are relatively constant within a design frequency range of approximately 9%.