Intermec IP Corporation

Vijay Pillai

Harley K Heinrich

Rene D Martinez

Pavel Nikitin

For Sander Lam

Shashi Ramamurthy

David E Dieska

A radio frequency identification (RFID) reader outputs an interrogation signal, and hops/varies the phase of the interrogation signal sent by the RFID reader over time. Varying the phase of the interrogation signal enables the RFID reader to provide, for each zone of an RF field of the RFID reader, a particular phase that reduces of the effects of interference RF signal(s) present in that zone of the RF field. Reducing the interference in each zone of the RF field increases the throughput of RFID tags that can be successfully read by the RFID reader.

Phase hopping to reduce interference and improve radio frequency identification (RFID) tag throughput

Processing a transponder signal received from a transponder may include providing a first signal that is in-phase with the transponder signal and a second that is off-phase with the first signal. A first transformed signal is generated using the first signal, where the first transformed signal has a first characteristic equal to the first characteristic of the first signal and a second characteristic different from the second characteristic of the first signal. A second transformed signal is generated using the second signal, where the second transformed signal has a first characteristic equal to the first characteristic of the second signal and a second characteristic different from the second characteristic of the second signal. Information incorporated in the transponder signal is obtained using a combination of the first transformed signal and the second transformed signal.

System and method of reading RFID tags at high speeds

A state storage device for use in an RFID tag includes, in at least one embodiment, a capacitor coupled to a high impedance node. The storage device can be configured to indicate a high or low bit condition. The high impedance node can be designed to dissipate the stored electrical charge at a user-controlled, predefined, or known rate. The state storage device can be configured to store the bit condition for no more than four seconds. In some embodiments, the high impedance node can be formed from an electrically trimmed transistor.

State storage with defined retention time

A radio frequency identification (RFID) device with two or more antennas may select one antenna to backscatter or otherwise transmit, while deriving power from receipt of a carrier wave at one or more other antennas. The RFID device may select the antenna receiving the lower power or producing the lower voltage to transmit. The RFID device may select the antenna receiving the higher power or producing the higher voltage to transmit if the lower power or voltage is insufficient to operate the RFID device to backscatter or transmit. The RFID device may select neither antenna to transmit if the higher power or voltages are insufficient to operate the RFID device to backscatter or transmit.

Device and method for selective backscattering of wireless communications signals

A system and method is provided for using a frequency division circuit to produce a desired frequency in a radio frequency identification transponder (RFID tag). In a preferred embodiment of the present invention, an RFID tag includes a frequency division circuit connected to a logic circuit and a oscillator. The logic circuit is adapted to identify at least one frequency associated with a received RF signal (e.g., the frequency of the signal, a frequency identified by the signal, etc.). This frequency is then used by the frequency division circuit to calibrate the frequency provided by the oscillator. In one embodiment of the present invention, the frequency division circuit includes at least one variable counter adapted to divide the frequency provided by the oscillator (i.e., the oscillation frequency) by a programmable factor to produce a desired frequency. The desired frequency is then provided to the logic circuit and used to modulate a received RF signal. In another embodiment of the present invention, the frequency division circuit further includes at least one fixed counter, wherein the fixed counter is not programmable. In this embodiment, the fixed counter is used to produce a particular (lower) frequency, and the variable counter is used to produce the desired frequency. Such an embodiment, for example, can be used to decrease the amount of time required to produce a desired frequency (e.g., by starting with a lower fixed frequency) and increase the amount of time available to perform alternate functions (e.g., communicate with external devices, etc.).

System and method for setting an oscillator in an RFID transponder

At least one identification (ID) number is used to effectuate communication between a radio frequency (RF) number and a radio frequency identification (RFID) base station. In accordance with a first embodiment of the present invention, at least a first ID number and a second ID number are stored on an RF transponder. Upon receipt of a write request, the RF transponder compares an ID number portion of the write request with the second ID number stored on the RF transponder. If the numbers matched, then a data portion of the write request is stored on the RF transponder. If the ID numbers do not match, then the write request is ignored. In accordance with a second embodiment of the present invention, the RF transponder is adapted to determine the second ID number using at least a portion of the first ID number. For example, the second ID number could be a subset of the first ID number, determined using an algorithm that is based (at least in part) on a portion of the first ID number, etc. In accordance with a third embodiment of the present invention, the second ID number is independent of the first ID number. For example, the second ID number could be a constant that is unrelated to the first ID number. In accordance with a fourth embodiment of the present invention, the data portion of the write request is stored on the RF transponder before the ID number portion of the write request is compared to the ID number stored on the RF transponder. If the ID number portion of the write request matches the ID number stored on the RF transponder, then the stored data is left undisturbed. If, however, the ID numbers do not match, then the stored data is erased (e.g., replaced with a null set, the original data, etc.).

System and method of reading from and/or writing to an RF transponder

An identification protocol that includes multiple identification methodologies is used to isolate and identify a radio frequency (RF) transponder. In accordance with a preferred embodiment of the present invention, the RF transponder includes a memory device, an RF front end, a random number generator (RNG), a counter, and a signal processing circuit connected thereto and programmed to operate in accordance with an identification protocol (or portions thereof). If multiple RF transponders are transmitting their ID numbers simultaneously, the radio frequency identification (RFID) base station may chose to resolve these conflicts later by transmitting the {a} Next_Cycle command, which moves the transponders back to a ready state. Alternatively, the {a} Fail command can be used to isolate and identify individual RF transponders. Once the transponder is isolated, it can be acknowledged and/or move to a 20 data_exchange state by transmitting a Read_New, FAK, PAK or AAK command, each one having unique characteristics.

Enhanced identification protocol for RFID systems

A radio frequency identification (RFID) system includes a plurality of RFID tags each having adjustable tag resonant frequency, and an RFID reader configured to transmit interrogation and change frequency RF signals. The interrogation and change frequency RF signals are transmitted at the current tag resonant frequency. The plurality of RFID tags modify the tag resonant frequency to a new tag resonant frequency in response to the change frequency RF signals. RFID tag identification rates may be enhanced by interrogating the plurality of RFID tags at the tag resonant frequency for a dwell time, receiving response RF signals, determining a new tag resonant frequency, and transmitting a change frequency RF signal that causes the RFID tags to change the tag resonant frequency to the new tag resonant frequency. The new resonant frequency may be based on the number of received responses.

System and method of enhancing range in a radio frequency identification system

A multistage voltage multiplying circuit for single chip passive RF tags is provided, wherein the parasitic capacitance of the diodes of each stage of the voltage multiplying circuit is much less than the parasitic capacitance of the diodes of the preceding stage.

Radio frequency identification transponder with a quadrupler or N-tupler circuit for efficient RF to DC conversion

An RFID tag is powered both by an internal battery and passively by an interrogating RF field. As a result, the RFID tag can be passively powered after the internal battery has been depleted. More particularly, an embodiment of the RFID tag includes electronic circuitry to provide RFID functionality, and an energy storage device coupled to the electronic circuitry to provide an operational voltage thereto. A battery is operatively coupled to the energy storage device to charge the energy storage device. A rectified RF power source derived from an interrogating RF field is also operatively coupled to the energy storage-device to charge the energy storage device. The rectified RF power source and the battery are electrically separated from each other. The energy storage device remains charged by the battery in the absence of the RF interrogating field while the battery has remaining capacity. After the battery has become depleted, the energy storage device is charged by the presence of the RF interrogating field.

RFID tag having combined battery and passive power source

RFID tag with a quadrupler or N-tupler circuit for efficient RF to DC conversion

The present invention provides an RFID transponder that includes a state holding cell that maintains the present state of the RFID transponder during temporary losses of power. After power is restored to the RFID transponder, the state holding cell restores the present state to the RFID transponder so that transactions with an RFID interrogator can continue without having re-transmit redundant commands. The RFID transponder further comprises an RF front end adapted to receive an interrogating RF signal. An analog circuit is coupled to the RF front end and is adapted to recover analog signals from the received interrogating RF signal. The analog circuit provides state information defining a desired state of the RFID transponder corresponding to the analog signals. A digital state machine is coupled to the analog circuit and adapted to execute at least one command in accordance with the state information. A memory is coupled to the digital state machine and is adapted to store and retrieve digital data responsive to the at least one command executed by the digital state machine. A power capacitor is coupled to the RF front end and derives a voltage rectified from the interrogating RF signal to charge the power capacitor. The power capacitor thereby provides electrical power for the analog circuit, the digital state machine and the memory. The state holding cell is coupled to the analog circuit and the digital state machine and is adapted to maintain the state information during a loss in power provided by the power capacitor due to lapse in receipt of the interrogating RF signal by the RF front end.

Growing community of inventors

Mukilteo, WA, United States of America

Vijay Pillai