Patent ID: 8581699

Claim:
A portable equipment detecting system mounted on a vehicle, communicating with a portable equipment by wireless communication thereby detecting a location of the portable equipment, the detecting system comprising: an antenna radiating electromagnetic waves, the antenna including a first element, a second element electrically connected in series to the first element, and a bypass wiring of which one end of the wiring is connected to a connection point of the first and second elements, the antenna being arranged such that a longitudinal direction of the first element is defined as a running direction of the vehicle and a longitudinal direction of the second element is defined as a direction perpendicular to both of the running direction of the vehicle and a vertical direction of the vehicle; transmitting means for transmitting a request signal requesting the portable equipment to return an acknowledge signal, the request signal being transmitted to the antenna thereby radiating the electromagnetic waves including the request signal; receiving means for receiving the acknowledge signal from the portable equipment via the antenna which receives the electromagnetic waves including the acknowledge signal; and detecting means for detecting the location of the portable equipment based on the acknowledge signal returned by the portable equipment, wherein power is supplied to the antenna in one of three supplied states including a first supplied state, a second supplied state and a third supplied state, wherein the first supplied state is configured such that the bypass wiring and the first element are electrically conducted to supply the power only to the first element, the second supplied state is configured such that the bypass wiring and the second element is electrically conducted to supply the power only to the second element and the third supplied state is configured such that the power is supplied to the first and second elements, the detecting means is configured to switch between three supplied states and detect the location of the portable equipment based on the acknowledge signal at a time when the supplied state is switched.