Patent ID: 6278698
Filing Date: 2001-08-21
Classification: G06K,H01Q,H03L

Abstract:
A radio frequency identification device comprising:an integrated circuit including a microprocessor, a receiver configured to receive radio frequency commands from an interrogation device and having an output coupled to the microprocessor, a transmitter configured to transmit a signal identifying the device to the interrogator in response to a command from the microprocessor, and a wake-up timer circuit coupled to the receiver and configured to determine if a signal received by the receiver is a radio frequency command from the interrogation device, the integrated circuit at times switching between a sleep mode and a receiver on mode, more power being consumed in the receiver on mode than in the sleep mode, the integrated circuit switching from the receiver on mode to a microprocessor on mode when logic in a wake-up timer circuit determines that a signal received by the receiver is a radio frequency command from the interrogation device, the receiver further including an amplifier powered by a selectively engageable voltage source engaged in the receiver on mode but not in the sleep mode, the amplifier including first and second inputs for receiving an input signal to be amplified, the inputs respectively including coupling capacitors, a differential amplifier having inputs respectively connected to the first and second inputs through the coupling capacitors, and having an output, selectively engageable resistances between the voltage source and respective inputs of the differential amplifier, second selectively engageable resistances between the voltage source and respective inputs of the differential amplifier, the second resistances respectively having smaller values than the first mentioned resistances, the second resistances being engaged then disengaged in response to the integrated circuit switching from the sleep mode to the receiver on mode.