| 摘要 |
An electromagnetic transmission and detection system is disclosed, comprising a transmission coil (20) for producing a high intensity electromagnetic field, and first and second receiver coils (32, 34) for receiving a low-intensity electromagnetic field transmitted from an inductively powered transponder device (30). The receiver coils are positioned diametrically opposite each other and connected in a differential circuit relationship such that the magnitude of electrical signals induced in the coils by ambient electromagnetic energy are substantially equal and opposite each other. The coil assembly for use in the transponder includes a primary coil (156), the leads of which are left floating, and a secondary coil (158) which has its leads connected to an integrated identification circuit within the transponder. Both coils are wrapped around the same coil forming ferrite rod, and are configured to resonate at the same operating frequency, such that the quantity of energy which can be transferred between the transmitter and the transponder is maximized. |
