Patent ID: 6741814
Filing Date: 2004-05-25
Classification: H01P

Abstract:
A compact balun comprising:a transmission line of two conductors bent to form a U-shape including a more curved section with two ends each connected to a respective less curved section; a respective terminal at a terminal end of each less curved section, the terminal ends being remote from the connection to the more curved section, wherein each respective terminal includes a plurality of contacts each of which connects to one of the two conductors; and one or more cylindrical ferrite beads, each with an axial hole through which a respective less curved section of the transmission line extends, wherein: the conductors of the transmission line are separated by a dielectric material; the dielectric material is Teflon; the transmission line is a coaxial cable; the coaxial cable does not have an outer covering; the coaxial cable is semi-rigid, has characteristic impedance of 75 ohms, and is approximately 2.5 mm in diameter; the more curved section has a radius of approximately 3 to 6 mm; the radius of the more curved section is approximately 4 mm; the length of the less curved sections between the connections to the curved section and the closest terminal of one of the wires are approximately 15 to 30 mm long; there are two beads on each less curved section of the pair of transmission lines; the beads are approximately 4 to 8 mm long and approximately 4 to 6 mm in diameter; the beads are approximately 6 mm long and approximately 5 mm in diameter; the beads on the same less curved section are approximately in contact; the terminals include a section of coaxial cable 1-3 mm long, a section of inner conductor covered with dielectric material that is 1 to 3 mm long, and a section of inner conductor 1 to 8 mm long; the insertion loss of the balun is less than 0.5 dB at 900 MHz; the insertion loss of the balun is approximately 0.2 dB at 900 MHz; the return loss is less than 30 dB; the return loss being approximately 20 dB; and the balun has a substantially flat response for signal transmission frequencies between 5 and 1005 MHz.