RFID system with time slot interleaving
View Patent ↗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.
1. An RFID interrogation system configured to transmit to and receive signals from first and second antennas located in proximity to each other and located to direct signals to and receive signals from respective interrogation zones, wherein said transmission and reception occur during predetermined timeframes each comprising a downlink period and an uplink period such that:
a first downlink signal from a first RFID interrogator is transmitted to the first antenna during a first downlink window and after said first downlink window a first uplink window for receiving a signal from a first RFID transponder is opened and
a second downlink signal from said first RFID interrogator or from a second RFID interrogator is transmitted to the second antenna during a second downlink window and after said second downlink window a second uplink window for receiving a signal from a second RFID transponder is opened and wherein:
said first uplink window comprises a first acquire window,
said second uplink window comprises a second acquire window,
said second downlink signal is transmitted after said first downlink signal such that
said first acquire window occurs after said second downlink signal and said second acquire window occurs after said first acquire window and
wherein during said first acquire window, the system is not enabled to receive a signal from said second antenna and during said second acquire window, the system is not enabled to receive a signal from said first antenna
and wherein said first and second acquire windows do not overlap in time.
2. The method of claim 1 , wherein said system is configured to assign a signal reception occurring during said first acquire window as a response to said first interrogation signal.