Coherent multichip RFID tag and method and apparatus for creating such coherence
First Claim
Patent Images
1. In an RFID tag employing more than two microradio chips connected to the feed point of the tag antenna, a method for assuring that the digital outputs of the microradio chips do not interfere with each other, comprising the steps of:
- providing more than two microradio chips in a single tag;
activating all of the microradio chips in a single tag such that they produce coherent outputs in the same time slot, the activation step providing that the outputs of the microradio chips in the single tag occur in the same time slot, the activation step including determining the time slot for which a microradio chip generates an output by providing each microradio chip with a pseudo-random number generator and a time slot selection unit coupled thereto, with the time slot selection unit keying the associated microradio chip transmitter in the single tag in a time slot set by the output of the pseudo-random number generator; and
,providing each of the pseudo-random number generators for the microradio chips in a single tag with an identical seed to assure coherence.
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Abstract
An RFID tag (10), containing at least two independent microscopic RFID chips (16) or microradios is programmed with the same unique identifier for each chip. The unique identifier is used in the RFID chips (16) to key the RFID chip (16) transmitting to produce outputs in the same time slot so that the outputs add coherently, thus to create an output that is identical to that of a conventional tag containing only one such chip.
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Citations
14 Claims
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1. In an RFID tag employing more than two microradio chips connected to the feed point of the tag antenna, a method for assuring that the digital outputs of the microradio chips do not interfere with each other, comprising the steps of:
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providing more than two microradio chips in a single tag; activating all of the microradio chips in a single tag such that they produce coherent outputs in the same time slot, the activation step providing that the outputs of the microradio chips in the single tag occur in the same time slot, the activation step including determining the time slot for which a microradio chip generates an output by providing each microradio chip with a pseudo-random number generator and a time slot selection unit coupled thereto, with the time slot selection unit keying the associated microradio chip transmitter in the single tag in a time slot set by the output of the pseudo-random number generator; and
,providing each of the pseudo-random number generators for the microradio chips in a single tag with an identical seed to assure coherence. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12)
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13. An RFID tag, comprising:
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a common antenna; more than two microradio chips in a single RFID tag coupled to said common antenna, each of said microradio chips including a pseudo-random number generator coupled to a time slot selection unit for selecting the time slot in which said microradio chips transmit, each microradio chip including a transmitter that transmits under control of said time slot selection unit; an identical seed for each of said pseudo-random number generators; a receiver and decoder for detecting the interrogation signals that arrive at said antenna; a seed generator coupled to said receiver and decoder for outputting said identical seed responsive to an interrogation signal; a data storage medium for storing at least an identification code related to a tagged item; a modulator coupled to said identification code for modulating said transmitter with said identification code; energy storage coupled to said antenna for converting RF energy at said antenna to energy to power said RFID chips; and
,for each microradio chip a synchronization unit coupled to said antenna for establishing phase coherence between RF energy arriving at said antenna and the output of a microradio chip transmitter, such that the output of said transmitter is phase coherent with the RF signal at said antenna, thus to establish phase coherence between all of the microradio chips associated with said tag and coupled to said common antenna. - View Dependent Claims (14)
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Specification