RFID SYSTEM WITH TIME SLOT INTERLEAVING

• US 20120280796A1
• Filed: 05/04/2012
• Published: 11/08/2012
• Est. Priority Date: 05/06/2011
• Status: Active Grant

• Current Assignee: Amtech Systems LLC (Roper Technologies, Inc.)
• Original Assignee: Amtech Systems LLC (Roper Technologies, Inc.)
• Inventors: Gravelle, Kelly, Melville, Michael, Kelsey, Karl
• Granted Patent: US 8,928,462 B2
• Time in Patent Office: Days
• US Class Current: 340/10.2
• CPC Class Codes: G06K 7/10019 resolving collision on the communication channels between simultaneously or concurrently interrogated record carriers. collision between the communication channels used by wireless communication devices, where the solution is not particularly adapted for RFIDs or the like, H04W74/08
• CPC Class Codes: G06K 7/10029 the collision being resolved in the time domain, e.g. using binary tree search or RFID responses allocated to a random time slot
• CPC Class Codes: G06K 7/10039 interrogator driven, i.e. synchronous
• CPC Class Codes: G06K 7/10356 using a plurality of antennas, e.g. configurations including means to resolve interference between the plurality of antennas
• CPC Class Codes: G06K 7/10366 the interrogation device being adapted for miscellaneous applications
• CPC Class Codes: G08G 1/017 identifying vehicles G08G1/015, G08G1/054 take precedence

Abstract

A method for interleaving time slots in a multi-antenna system for communication with RFID tags is disclosed. An example is shown for an eight antenna system. A first four antennas arranged side-by-side are sequentially energized to interrogate RFID transponders. A second set of four antennas arranged side-by-side, the first of which is adjacent to the last of the first set of antennas. A four-antenna sequence is performed for the first four antennas and a second four antenna sequence is performed for the second set of antennas. The first and second four antenna sequences are offset by only a marginal amount, sufficient to ensure that a transponder signal received four antennas away from an active antenna is not acknowledged because the receive window for the non-active antenna is delayed.

Claims

1. A method of communicating with an active RFID transponder in a system having a plurality transponder reader antennas arranged as a first set of adjacent reader antennas and a second set of adjacent reader antennas and two sets of time slots for sequentially transmitting to the first set of adjacent reader antennas during a first multi-position time slot and to the second set of adjacent reader antennas during a second multi-position time slot comprising:

sequentially transmitting a first interrogation signal to each of the first set of adjacent reader antennas during the first multi-position time slot;

opening a first receiving window a predetermined time after each of said first interrogation signals, said first receiving window allowing reception of signals only from the one of said first set of reader antennas that just transmitted;

sequentially transmitting a second interrogation signal to each of the second set of adjacent reader antennas during the second multi-position time slot;

opening a second receiving window a predetermined time after each of said second interrogation signals, said second receiving window allowing reception of signals only from the one of said second set of reader antennas that just transmitted;

and delaying the sequential transmission of said second interrogation signal to said second set reader antennas from the sequential transmission of said first interrogation signal to said first set of said reader antennas, such that said second receive windows of said second set of reader antennas are not aligned in time with said first receive windows of said first set of reader antennas.

2. The method of claim 1, wherein said first set of reader antennas consists of four reader antennas and said second set of reader antennas consists of four antennas.

3. The method of claim 1, wherein said first set of reader antennas consists of three antennas and said second set of reader antennas consists of three antennas.

4. The method of claim 1, wherein said first set of reader antennas consists of two reader antennas and said second set of reader antennas consists of two antennas.

5. The method of claim 1, wherein said first set of reader antennas is larger or smaller than said second set of reader antennas.

6. The method of claim 1, wherein said delay is longer than said first interrogation signal.

7. A method of interrogating active RFID transponders comprising:

transmitting a first interrogation signal from a first antenna and thereafter opening a first acquire window;

transmitting a second interrogation signal from a second antenna a predetermined delayed time after the start of said first interrogation signal and thereafter opening a second acquire window;

wherein said second interrogation signal is transmitted substantially during said first acquire window.

8. The method of claim 7, wherein said first and second antennas are close enough to an RFID transponder that said transponder can receive said first and said second interrogation signals.

9. The method of claim 8, wherein said first and second antennas are separated by additional antennas and wherein said additional antennas transmit interrogation signals at different times than said first and second interrogation signals.

10. A system for communicating with an active RFID transponder comprising

a transponder reader;

a first set of adjacent reader antennas; and

a second set of adjacent reader antennas;

wherein

said reader is adapted for sequentially transmitting to the first set of adjacent reader antennas during a first multi-position time slot and to the second set of adjacent reader antennas during a second multi-position time slot such that;

a first interrogation signal is sequentially transmitted to each of the first set of adjacent reader antennas during the first multi-position time slot;

a first receiving window is opened a predetermined time after each of said first interrogation signals, said first receiving window allowing reception of signals only from the one of said first set of reader antennas that just transmitted;

a second interrogation signal is transmitted to each of the second set of adjacent reader antennas during the second multi-position time slot;

second receiving window is opened a predetermined time after each of said second interrogation signals, said second receiving window allowing reception of signals only from the one of said second set of reader antennas that just transmitted;

the sequential transmission of said second interrogation signal to said second set reader antennas is delayed from the sequential transmission of said first interrogation signal to said first set of said reader antennas, such that said second receive windows of said second set of reader antennas are not aligned in time with said first receive windows of said first set of reader antennas.