Coherent multichip rfid tag and method and apparatus for creating such coherence

• US 20090303014A1
• Filed: 08/24/2006
• Published: 12/10/2009
• Est. Priority Date: 08/25/2005
• Status: Active Grant

• Current Assignee: RadioFIDO LLC
• Original Assignee: BAE Systems Information and Electronic Systems Integration Incorporated (BAE Systems Plc)
• Inventors: Brommer, Karl D., Erikson, Kenneth R.
• Granted Patent: US 8,115,630 B2
• Time in Patent Office: Days
• US Class Current: 340/10.200
• CPC Class Codes: G06K 19/072 the record carrier comprising a plurality of integrated circuit chips
• CPC Class Codes: G06K 19/0723 the record carrier comprising an arrangement for non-contact communication, e.g. wireless communication circuits on transponder cards, non-contact smart cards or RFIDs

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.

Claims

1. In an RFID tag employing multiple 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 step of:

activating all of the microradio chips such that they produce an output in the same time slot.

2. The method of claim 1, wherein providing that the outputs of the microradio chips occur in the same time slot includes the steps of:

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 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 with an identical seed.

3. The method of claim 2, wherein the outputs of the microradio chips include bits of information, and further including the step of providing phase coherence of the outputs of all of the microradio chips such that not only is each bit of information in the output of each microradio chip transmitted at the same time, the RF output of all of the microradio chips is phase coherent such that the outputs of the microradio chips add constructively to increase the output of the antenna.

4. The method of claim 1, and further including the step of transmitting an RF signal to all of the microradio chips through the tag antenna such that the transmitters of all of the microradio chips are synchronized in phase to the RF signal, whereby not only will the digital bits be transmitted by all of the microradio chips at the same time, but also the signals from all of the microradio chips will be phase coherent and in phase.

5. The method of claim 1, wherein the microradio chips are provided with identical pseudo-random number generators having the same time delays therethrough, and further including the step of providing the same seed to each of the pseudo-random number generators such that the same time slot can be selected for the transmission of the digital outputs.

6. The method of claim 1, and further including the step of irradiating the tag with RF energy from a reader of sufficient strength to charge up each of the microradio chips to turn on the electronics contained in each chip.

7. The method of claim 6, and further including the step of having the reader transmit out a query to each of the microradio chips.

8. The method of claim 7, wherein upon receipt of a query from the reader each of the microradio chips individually responds and sends out a signal through the tag antenna, all of the microradio chips sending out the same kind of signal.

9. The method of claim 8, wherein all of the signals transmitted by the microradio chips are digital signals involving 1'"'"'s and 0'"'"'s that come out in the same time slot at the same time from each of the microradio chips.

10. The method of claim 1, and further including the step of programming the tag at the point of shipment of an item bearing the tag such that each of the associated microradio chips in the tag is programmed with a unique identification number.

11. The method of claim 10, wherein each of the microradio chips includes a pseudo-random number generator, and wherein the programming step includes the step of installing the same seed in all of the pseudo-random number generators for all of the microradio chips associated with the tag.

12. The method of claim 11, wherein the programming step includes instructing different tags to install different seeds such that the microradio chips of different tags, while transmitting in a single time slot, are programmed such that different tags have different seeds and thus different time slots associated therewith, whereby the tags may be programmed with different seeds during attachment to different items.

13. The method of claim 12, and further including the step of reading out the tag utilizing a reader and further including the step of instructing the microradio chips in a tag to transmit in a different time slot upon detection of collisions with other tags.

14. The method of claim 13, wherein the step of instructing the tags to transmit in different time slots based on the detection of a collision includes having each tag generate a new time slot using a different pre-stored seed.

15. The method of claim 14, wherein the instruction to use a different pre-stored seed is in response to the detection of a collision by the reader.

16. An RFID tag, comprising:

a common antenna;

a number of microradio chips coupled to said 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;

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 a 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; and

,

energy storage coupled to said antenna for converting RP energy at said antenna to energy to power the circuits in said RFID chip.

17. The apparatus of claim 16, and further including 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.

18. The apparatus of claim 16, wherein said seed generator includes a unit for pre-storing different seeds and wherein said receiver and decoder, upon receipt of a collision-indicating signal from said reader, instructs said seed generator to generate a second seed different from a first seed to establish a time slot different from that associated with the first seed.

19. An RFID tag containing at least two RFID microradio integrated circuits, each circuit comprising:

RF reception means;

a decoder/encoder for decoding and encoding information;

storage for storing a unique identifier code;

a pseudo-random number generator; and

,

an RF transmitter.