Patent ID: 7777688

Claim:
A polarization switching antenna device applied to a radio apparatus, comprising: an antenna element that is constituted by a conductor shaped into a loop, and has a first end portion adapted to be connected to a first feeding point of the radio apparatus or a ground point and a second end portion adapted to be connected to a second feeding point of the radio apparatus or the ground point; a switch that is provided to at least one of the first end portion and the second end portion to open the antenna element from an electronic circuit of the radio apparatus, wherein a first antenna characteristic having a high sensitivity to a magnetic field and a second antenna characteristic having a high sensitivity to an electric field are switched by switching the switch; a Balun (Balanced to Unbalanced) that transforms a balanced input into an unbalanced output; and a route switching portion that switches a first signal route passing through the Balun and a second signal route not passing through the Balun to feed the antenna, wherein at least one of inputs of the Balun is connected to the antenna element through the switch.