| 摘要 |
PCT No. PCT/CA91/00147 Sec. 371 Date Oct. 30, 1992 Sec. 102(e) Date Oct. 30, 1992 PCT Filed May 1, 1991 PCT Pub. No. WO91/17515 PCT Pub. Date Nov. 14, 1991.An electronic identification system comprising a transmitter for generating an electromagnetic excitation signal, one or more portable transponders for storing variable identification data, and for transmitting an information signal containing the identification data upon entering the field. Transmission of the information signal is independent of the excitation signal in both time and frequency. A radio frequency receiver is provided for receiving the information signal and in response generating output signal representing the variable identification data contained in the information signal. The system overcomes two principle disadvantages associated with existing systems: and excitation frequency can be selected for optimum performance given the circumstances dictated by each application; an independent response channel can be selected according to the requirements of each installation or application, thereby allowing response signals to be transmitted by transponders at a frequency which differs form the frequency of an interfering signal. |
