The antenna apparatus of the present invention places antenna element 302 that transmits or receives electromagnetic waves on basic plate 301, places parasitic antenna elements 303 to 306 on basic plate 301 evenly spaced concentrically centered on antenna element 302, places switch elements 307 to 310...http://www.google.fr/patents/US6337668?utm_source=gb-gplus-shareBrevet US6337668 - Antenna apparatus
