Patent ID: 7463208

Claim:
An antenna comprising a magnetic main-path member comprising a coil wound around a magnetic core, and a magnetic sub-path member magnetically connected to said magnetic core for constituting a substantially closed magnetic path with said magnetic main-path member such that a high S/N ratio in the antenna is acheived by adjusting both a relative permeability ratio and a cross section area ratio of the magnetic sub-path member to the magnetic core based on a result of the measurement of an S/N ratio before and after connecting a magnetic sub-path member to the magnetic core, said antenna meeting the relation of (S/N) 1 >(S/N) 0 , wherein (S/N) 1 is a ratio of a signal voltage S obtained from said coil to a noise voltage N in this antenna, and (S/N) 0 is a ratio of a signal voltage S to a noise voltage N in an antenna having the same structure except for having no magnetic sub-path member.