Checkpoint Systems, Inc.

Microchip Technology Inc.

William F Gallagher, Iii

Shinichiro Inui

Lee Furey

Youbok Lee

Russell E Barber

Samuel E Alexander

Ronald Salesky

Riccardo Benedetti

Eric Alan Eckstein

Sam E Alexander

Ron Salesky

Arbitration of multiple transponders, such as RFID tags, occurs in an interrogation field. The arbitration process is custom-tailored for individual applications, under software control, by the transponder reader or tag reader. Different wake-up slots are calculated for each tag during successive transmission cycles based upon the tag ID and the transmission cycle number. The tag reader may also send a special command to a tag to read its data and cause the tag to become decoupled from the environment. The tags may be selectively placed in either a tag-talk-first mode or a reader-talk-first mode. Furthermore, the tag reader may send a special fast read command to the tag which includes a read request and at least one parameter of the read request.

Anticollision protocol with fast read request and additional schemes for reading multiple transponders in an RFID system

Arbitration of multiple transponders, such as RFID tags, occurs in an interrogation field. The arbitration process is custom-tailored for individual applications, under software control, by the transponder reader or tag reader. Different wake-up slots are calculated for each tag during successive transmission cycles based upon the tag ID and the transmission cycle number. The tag reader may send a special fast read command to the tag which includes a read request and communications control parameters including the number of time slots for transponder communications, the number of transmissions that an individual transponder is allowed to issue, and the data rate at which the reader communicates to the transponder. The tag reader may also send a special command to a tag to read its data and cause the tag to become decoupled from the environment. Additional schemes are provided to halve the number of active tags in each transmission cycle and to selectively inactivate designated groupings of tag, thereby improving discrimination of the tags in the interrogation field. The tags may be selectively placed in either a tag-talk-first mode or a reader-talk-first mode.

A radio frequency identification (RFID) tag device having a pulse position modulation (PPM) decoder circuit which calculates a relative frequency relationship between an internal clock-oscillator of the RFID tag device and an external PPM source such as a RFID tag reader, and then synchronizes the RFID tag device PPM decoder circuit to the required precision for reliable PPM symbol decoding. The PPM decoder is synchronized by measuring the &ldquo;counts per pulse&rdquo; (CPP) from a calibration cycle having a plurality of pulses in a single symbol frame.

Method, system and apparatus for initiating and maintaining synchronization of a pulse position modulation (PPM) decoder with a received PPM signal

A rotating field antenna is provided which includes a figure eight shape loop, a center loop magnetically coupled to the figure eight shape loop, and a drive element for driving the figure eight loop. The figure eight shape loop has an upper loop, a lower loop and a crossover region therebetween. The center loop overlaps at least a portion of the crossover region and at least a portion of one or both of the upper and lower loops. The center loop has no direct or physical electrical connection to the offset figure eight shape loop. Magnetic induction produces a 90-degree phase difference between the phase of the figure eight loop and the phase of the center loop. The antenna thereby produces a rotating composite field when driven by the drive element. The figure eight loop and the center loop are coplanar. The drive element may be an amplified voltage source which has a fundamental frequency of about 13.56 MHz, thereby providing a multiple loop antenna which is useful for electronic article surveillance systems that use RFID tags which resonate at 13.56 MHz.

Rotating field antenna with a magnetically coupled quadrature loop

An RFID tag circuit provides magnetic decoupling and amplitude modulation. The circuit is made up of a first inductor and a second inductor connected in series, a first capacitor, a second capacitor, and a switch. The circuit includes a first resonant circuit formed from a parallel connection of the series connected first and second inductors, and the first capacitor. The first resonant circuit has a primary resonant frequency. The circuit also includes a second circuit formed from a series connection of the second capacitor and the switch. The series connection of the second capacitor and the switch are connected in parallel to the second inductor. One end of the series connected second capacitor and switch is connected to the common connection between the series connected first and second inductors. When the switch is open, the second circuit has a minimal or no effect on the tag and the first resonant circuit resonates at the primary resonant frequency when the tag is exposed to an external field at or near the primary resonant frequency. When the switch is closed, the second circuit defines a high impedance parallel resonant circuit which functions to block or minimize current flow at the primary resonant frequency, thereby preventing the tag from drawing any significant amount of power from the external field and from resonating at the primary resonant frequency. The tag is thereby decoupled from its environment.

RFID tag having parallel resonant circuit for magnetically decoupling

Noise reduction schemes are provided in a radio frequency identification (RFID) system for use with RFID intelligent tags. Fiber optics are used to communicate analog tag response signals from the output of the receiver circuit to the input of a tag response signal analyzing module, which includes a digital signal processor (DSP). The fiber optics creates electrical isolation between these circuit elements breaking ground loops, stopping internal switching noise from the DSP from entering the receiver circuitry, and preventing common mode signals from interfering with the desired RFID tag signal.

Optical interface between receiver and tag response signal analyzer in

Noise reduction schemes are provided in a radio frequency identification (RFID) system for use with RFID intelligent tags. Amplitude and phase noise is minimized by starting with a low noise crystal oscillator having an output frequency which is an integer multiple n of the desired RF field frequency, and then dividing this frequency by the integer multiple n. One or more cascaded flip-flops are used for the frequency dividing. Both outputs of the final stage flip-flop are used to drive the transmitter antenna to produce a continuous wave signal.

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Phoenixville, PA, United States of America

William F Gallagher, Iii