Patent ID: 7113148

Claim:
A bifilar helical antenna, comprising: an output/input unit, which is further composed of a substrate and a hybrid disposed on the substrate, in which the surface of the substrate is coated with a metallic conductive layer; the hybrid is a microstrip-line pattern formed by the metallic conductive layer on surface of the substrate, and is provided with a ring part and a plurality of transmission ports; and an antenna unit, which is further composed of a shell and an impedance transformer, in which the shell is a cylindrical hollow tube disposed on the substrate of the output/input unit, on which a first and a second helical line parallel to each other are wound, where both the bottom ends of the helical lines are electrically connected to each other, the impedance transformer is comprised of a first and a parallel second transmission line, in which both the top ends of the transmission lines are electrically connected with the top ends of the first and the second helical line, respectively, while the bottom ends of the transmission lines are electrically connected to different transmission ports of the mixer.