A helical antenna with a self-complementary shape

The authors propose a bifilar helical antenna with a self-complementary shape. Bifilar helical antennas having an omnidirectional radiation pattern often have been composed of thin wires . In these conventional shapes, it is difficult to design an antenna satisfying both desired characteristics of the radiation and the reflection because the design parameters, such as antenna diameter, simultaneously influence these characteristics. The proposed antenna has an input impedance of which the conductance is almost constant by applying a self-complementary shape to the antenna structure. This technique allows selection of the optimal antenna diameter for the radiation characteristic independent of its impedance matching.