Anti-collision tag apparatus and system
First Claim
1. A radio frequency tag identification system comprising a plurality of tags and a transceiver for sending information to and receiving information from the tags, wherein each tag is allocated an identification word comprising a predetermined number of bits, the tags comprising means for selectively modulating a signal received from the transceiver and transmitting the modulated signals back to the transceiver, and the transceiver comprising means for sending an interrogation signal comprising a plurality of portions, wherein each portion of the interrogation signal has two possible signal formats, in the form of pulses having different durations, and the format used for a given interrogation signal portion is determined by the transceiver in dependence on modulated responses received from the tags during the transmission of the said given interrogation signal any previous portion, wherein each portion is associated with a predetermined bit, or bit sequence, of the identification words and is used to simultaneously interrogate the tags to identify, in response to modulated signals provided by the tags in response to the predetermined bit or bit sequence, the presence of a tag or tags having a given value of the identification word at the predetermined bit or bit sequence, wherein each tag is deactivated when not having said given value of the identification word at the predetermined bit or bit sequence.
2 Assignments
0 Petitions
Accused Products
Abstract
This invention relates to radio frequency identification (RFID) apparatus comprising a reader/writer and transponders (tags) such that 2 or more transponders are capable of operating simultaneously in the same field so that information in the form of data bits may be received from or sent to the tags without corruption.
-
Citations
23 Claims
- 1. A radio frequency tag identification system comprising a plurality of tags and a transceiver for sending information to and receiving information from the tags, wherein each tag is allocated an identification word comprising a predetermined number of bits, the tags comprising means for selectively modulating a signal received from the transceiver and transmitting the modulated signals back to the transceiver, and the transceiver comprising means for sending an interrogation signal comprising a plurality of portions, wherein each portion of the interrogation signal has two possible signal formats, in the form of pulses having different durations, and the format used for a given interrogation signal portion is determined by the transceiver in dependence on modulated responses received from the tags during the transmission of the said given interrogation signal any previous portion, wherein each portion is associated with a predetermined bit, or bit sequence, of the identification words and is used to simultaneously interrogate the tags to identify, in response to modulated signals provided by the tags in response to the predetermined bit or bit sequence, the presence of a tag or tags having a given value of the identification word at the predetermined bit or bit sequence, wherein each tag is deactivated when not having said given value of the identification word at the predetermined bit or bit sequence.
-
10. A method of detecting the presence of tags within a target area by sending interrogation signals from a transceiver for selective modulation and transmission back to the transceiver by tags present in the target area, each tag being allocated an identification word comprising a predetermined number of bits, the method comprising:
sending from a transceiver an interrogation signal comprising a plurality of portions, each portion of the interrogation signal having two possible signal formats, in the form of pulses having different durations, and the format used for a given interrogation signal portion being determined by the transceiver in dependence on modulated responses received from the tags during the transmission of the said given interrogation signal portion, each portion being associated with a predetermined bit or bit sequence of the identification words and being capable of conveying a given value for the bit or sequence of bits, wherein tags having the value at the predetermined bit or bit sequence are configured to modulate the signal and transmit the modulated signal back to the transceiver, the modulation being used to identify the presence of those tags, and wherein each tag is deactivated when not having said given value of the identification word at the predetermined bit or bit sequence. - View Dependent Claims (11, 12, 13, 14, 15, 16, 17, 23)
-
18. A method of identifying tags within a target area using a communication signal having a plurality of portions, each portion being of a substantially continuous first duration representing a first value or of a substantially continuous extended duration representing a second value, such that the portion has two possible formats in the form of pulses having different durations, each tag being allocated an identification word comprising a predetermined number of bits, the method comprising the steps of:
-
(a) transmitting from a transmitter the communication signal comprising a plurality of portions, each portion being associated with a predetermined bit of the identification word; (b) receiving a portion of the signal at a tag and, if the identification word of the tag has said first value at the respective bit and if the tag is not deactivated, modulating the portion of the signal at the tag; (c) monitoring at the transmitter the signal for modulation and, (c1) if modulation is detected, recording the presence of at least one tag having the first value at the respective bit, not transmitting the communication signal portion for the extended duration such that the communication signal portion has the format with shorter pulse duration, and proceeding to step (f); (c2) if no modulation is detected during the first duration, continuing the transmission of the first communication signal portion for the extended duration such that the communication signal portion has the format with longer pulse duration; (d) receiving the signal at a tag during the extended duration and, if the identification word of the tag has the second value at the respective bit and if the tag is not deactivated, modulating the associated portion of the signal at the tag; (e) monitoring at the transmitter the communication signal for modulation and, (e1) if modulation is detected during the extended duration, recording the presence of at least one tag having the second value at the respective bit and proceeding to step (g), (e2) if no modulation is detected during the extended duration, indicating that no tag is present in the target area; (f) deactivating tags having the second value at the respective bit which do not receive an extended communication signal portion; (g) if a communication signal for each bit of the identification word has been transmitted, indicating the presence of a tag having an identification word corresponding to the combination of recorded bit values, otherwise proceeding to step (a) for the next signal portion bit. - View Dependent Claims (19, 20, 21, 22)
-
Specification