System zur Bestimmung der Position eines tragbaren Geräts, Verfahren zur Bestimmung der Position eines tragbaren Geräts, und Vorrichtung zur Bestimmung der Position eines tragbaren Geräts

摘要

A portable-device position determination system has a portable device that is configured to be possessed by a user, and an in-vehicle device that is mounted on a vehicle and conducts wireless communication with the portable device. The in-vehicle device transmits a request signal to the portable device. The portable device detects a received signal intensity of the request signal to send back the received signal intensity to the in-vehicle device. The in-vehicle device compares the received signal intensity of the request signal detected by the portable device to a threshold to determine a position of the portable device. The in-vehicle device includes a transmission controller that generates the request signal, supplies an electric power to a transmitting antenna, and transmits the request signal from the transmitting antenna, and a current detector that detects a current passed through the transmitting antenna when the request signal is transmitted.