A Simple Circularly Polarized Wave Antenna using a Modified Transmission Line Antenna and Spiral Parasitic Element

A simplified modified transmission line antenna (MTLA) is combined with a one-and-a-quarter turn spiral wire parasitic element to achieve a circularly polarized wave antenna with good axial ratio of the supported wave and low return loss. The circularly polarized wave is generated primarily by the spiral element driven through the MTLA by electromagnetic coupling, and the main advantage of this antenna is that the circularly polarized wave can be controlled by the structure of the parasitic spiral element, while the impedance characteristics can be controlled by the shape of the MTLA. Thus, using this approach, a circularly polarized wave antenna with good impedance characteristics can be achieved using a relatively simple structure.