Identification system and method with passive tag
First Claim
1. An identification system, comprisinga reading device including means for receiving and processing coded information received via a magnetic coupling from at least one portable tag and for radiating a continuous wave alternating magnetic field, the reading device includinga first conductive coil,a transmission circuit coupled to the first conductive coil for generating the continuous wave alternating magnetic field of a predetermined frequency;
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Accused Products
Abstract
An identification system with a reading device having a single turn transmission coil for continuously radiating alternating energy. A portable tag receives via a magnetic coupling, the energy from the reader and charges a storage capacitor to 5 volts. The capacitor is discharged rapidly during a time period less than the charging time period. This discharge of the capacitor powers a coded information transmission circuit during a small percentage of the duty cycle.
113 Citations
17 Claims
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1. An identification system, comprising
a reading device including means for receiving and processing coded information received via a magnetic coupling from at least one portable tag and for radiating a continuous wave alternating magnetic field, the reading device including a first conductive coil, a transmission circuit coupled to the first conductive coil for generating the continuous wave alternating magnetic field of a predetermined frequency; - and
at least one portable tag for transmitting the coded information via the magnetic coupling in response to the reception of the continuous wave alternating magnetic field radiated by the reading device, each portable tag including means for storing the coded information to be transmitted, a second conductive coil for receiving and collecting energy of the radiated magnetic field, a reception circuit including a storage capacitor electrically coupled to the second conductive coil for charging the storage capacitor throughout a first time duration, the reception circuit including a circuit switch electrically coupled to the storage capacitor for discharging the capacitor after the charge on the capacitor has attained a predetermined threshold level, the discharging occurring during a second time duration less than the first time duration, said circuit switch being activated in direct response to the voltage across the capacitor having attained the predetermined threshold level and independent of the amplitude of the received radiated magnetic field, and coded information transmission means responsive to the activation of the switch, allowing discharging of the storage capacitor, and operable to transmit the stored coded information to the reading device by means of the magnetic coupling, during the second time duration. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 15, 17)
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11. A method of communicating coded information from a passive portable tag to a reading device of an identification system wherein the reading device continuous wave alternating energy having a predetermined frequency and amplitude;
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receiving via the magnetic coupling of the portable tag the generated energy of the reading device at times when the reading device and the portable tag are magnetically coupled; storing in the portable tag the received generated energy during a first time period; releasing the stored energy as soon as it has reached a predetermined value, during a second time period having a duration less than said first time period; and using the released energy to transmit the coded information via the magnetic coupling of the portable tag during the second time period. - View Dependent Claims (12, 13, 14)
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16. A passive portable tag for an identification system having a reading device for supplying a continuous wave alternating magnetic field to the tag and for receiving information from the tag, when magnetically coupled to the tag, the tag comprising
a receiving coil for receiving the continuous wave alternating magnetic field from the reading device, a storage capacitor electrically connected to the receiving coil to be charged throughout a first time period to a predetermined voltage, a first circuit means responsive to the charged capacitor attaining a predetermined voltage level, to discharge the capacitor, and a second circuit means responsive to the discharging of the capacitor for transmitting the information during a second time period shorter than the first time period, the first circuit means being operable in direct response to the voltage across the capacitor having attained the predetermined voltage level and independent of the amplitude of the received continuous wave magnetic field.
Specification