| 摘要 |
599876 Disclosed is a reader circuit for a radio frequency identification (RFID) reader having a dynamically adjustable Q-factor such that the reader transmits an activation signal configured to activate half duplex and full duplex transponders. The reader circuit has a signal source (611) configured to drive a resonant antenna (614), and a dynamic switching circuit configured to set the Q-factor of the resonant antenna (614) to a first value during the transmission of the activation signal. The resonant antenna (614) is a multi-filar antenna (614) comprising a primary filar (614a) and a set of secondary filars (614b) and a resistor (619) that is connected in series with at least one of the filars (614a, 614b). The dynamic switching circuit is configured to set the Q-factor of the resonant antenna (614) to a second value below the first value during detection of a data signal from a full duplex transponder. The dynamic switching circuit is also configured to set the Q-factor of the resonant antenna (614) to a third value below the second value when the RFID reader is not transmitting the activation signal. The dynamic switching circuit is also configured to control the Q-factor of the multi-filar resonant antenna (614). This is achieved by controlling the filars (614a, 614b) that are incorporated into the resonant antenna (614) circuit by setting the Q-factor of the resonant antenna (614) at a first value during the transmission of an activation signal comprises incorporating at least two of the filars into the resonant antenna (614) circuit so that the resistor (619) is not incorporated within the resonant antenna (614) circuit. The Q-factor of the resonant antenna (614) is then decreased during receipt of a data signal from any full duplex transponders present and during the transmission of the activation signal comprises incorporating a primary filar (614a) into the resonant antenna (614) circuit so that the resistor (619) is not incorporated in the resonant antenna (614) circuit. Finally, the Q-factor of the resonant antenna (614) is decreased upon stopping the transmission of the activation signal comprises incorporating the primary filar and the resistor (619) into the resonant antenna (614) circuit. |
