Abstract: A radio frequency identification (RFID) system includes an array of antennas to distinguish line-of-sight (LOS) paths from non-line-of-sight (NLOS) paths. The distance between adjacent antennas in the array of antennas is less than half the wavelength of the radio frequency (RF) signal of the system. Each antenna in the antenna array is also digitally controlled to change relative phase difference among the antennas, thereby allowing digital steering of the array of antennas across angles of arrival (AOAs) between 0 and ?. The digital steering generates a plot of signal amplitudes as a function of AOAs. LOS paths are distinguished from NLOS paths based on the shapes (e.g., depth, gradient, etc.) of local extremes (e.g., maxima or minima) in the plot.

Abstract: Radio-frequency identification (RFID) systems use readers to query and locate passive RFID tags in stores, warehouses, and other environments. An interrogation signal emitted by an antenna array from a reader powers up the tag, which replies by modulating and backscattering incident radiation toward the reader. The antenna array in the reader detects the modulated and backscattered radiation, which is usually several of orders of magnitude weaker than the interrogation signal, as the tag's reply. Unfortunately, crosstalk between the antenna elements in the antenna array limits the reader's sensitivity, which in turn limits the range at which the reader can detect and locate tags. Increasing the pitch of the antenna array to greater than half the wavelength of the interrogation signal reduces crosstalk but introduces grating lobes that produce spurious replies. Fortunately, filtering these spurious replies yields sensitive measurements from an antenna array with a pitch large enough to suppress crosstalk.

Abstract: Radio-frequency identification (RFID) systems use readers to query and locate passive RFID tags in stores, warehouses, and other environments. A signal from the reader powers up the tag, which modulates and backscatters the signal toward the reader. Unfortunately, the maximum permitted RF signal power, self-interference at the reader, tag sensitivity, and channel loss limit the range at which readers can detect and locate tags. Using multiple readers simultaneously circumvents these limits. When used together, each reader transmits a signal to a tag in turn, and all of the readers listen for each of the tag’s responses. The readers that are not transmitting do not experience self-interference and so can detect responses at lower power levels (longer ranges). Because the readers are at different locations, they measure different angles of arrival (AOAs) for each response. These simultaneous measurements can be used to locate each tag faster and with higher fidelity.

Abstract: A system and method for locating radio-frequency identification tags within a predetermined area. The method can incorporate sub-threshold superposition response mapping techniques, alone, or in combination with other methods for locating radio-frequency identification tags such as but not limited to time differential on arrival (TDOA), frequency domain phase difference on arrival (FD-PDOA), and radio signal strength indication (RSSI). The system can include a plurality of antennas dispersed in a predefined area; one or more radio-frequency identification tags; a radio-frequency transceiver in communication with said antennas; a phase modulator coupled to the radio-frequency transceiver; and a system controller in communication with said transceiver and said phase modulator. Calibration techniques can be employed to map constructive interference zones for improved accuracy.

Abstract: Radio-frequency identification (RFID) systems use readers to query and locate passive RFID tags in stores, warehouses, and other environments. An interrogation signal emitted by an antenna array from a reader powers up the tag, which replies by modulating and backscattering incident radiation toward the reader. The antenna array in the reader detects the modulated and backscattered radiation, which is usually several of orders of magnitude weaker than the interrogation signal, as the tag's reply. Unfortunately, crosstalk between the antenna elements in the antenna array limits the reader's sensitivity, which in turn limits the range at which the reader can detect and locate tags. Increasing the pitch of the antenna array to greater than half the wavelength of the interrogation signal reduces crosstalk but introduces grating lobes that produce spurious replies. Fortunately, filtering these spurious replies yields sensitive measurements from an antenna array with a pitch large enough to suppress crosstalk.

Abstract: Radio-frequency identification (RFID) systems use readers to query and locate passive RFID tags in stores, warehouses, and other environments. A signal from the reader powers up the tag, which modulates and backscatters the signal toward the reader. The reader or an appliance coupled to the reader can estimate the tag's position based on the angle of arrival (AOA) of the backscattered signal. In some situations, AOA measurements by different readers may yield different position estimates for the same tag. If these position estimates are close enough to each other (e.g., within the expected imprecision or error radius), they can be averaged to improve precision. If not, the appliance can measure the variance or another measure of dispersion for each reader's position estimates, then pick the reader with the lowest dispersion as the preferred or best sensor for locating that tag, improving precision and reducing processing time.

Abstract: A radio frequency identification (RFID) system includes an array of antennas to distinguish line-of-sight (LOS) paths from non-line-of-sight (NLOS) paths. The distance between adjacent antennas in the array of antennas is less than half the wavelength of the radio frequency (RF) signal of the system. Each antenna in the antenna array is also digitally controlled to change relative phase difference among the antennas, thereby allowing digital steering of the array of antennas across angles of arrival (AOAs) between 0 and ?. The digital steering generates a plot of signal amplitudes as a function of AOAs. LOS paths are distinguished from NLOS paths based on the shapes (e.g., depth, gradient, etc.) of local extremes (e.g., maxima or minima) in the plot.

Abstract: When a radio-frequency identification (RFID) tag reader queries an RFID tag, the reader or an appliance coupled to the reader derives a channel estimate from the tag's reply to the reader's query. The channel estimate represents the communications channel between the reader and that tag—or more precisely between the reader and the tag's location. This channel estimate acts as a fingerprint or signature for the communications channel between the reader and the tag's location. If the tag's environment is relatively static, then the channel estimate should be relatively stable, even if the tag is moved. The reader or appliance creates a library of tag locations indexed by channel estimate for each tag within range of the reader. When the reader receives a reply from a tag at an unknown location, the reader or appliance computes the corresponding channel estimate and uses that channel estimate to look up the closest location in the library of tag locations.

Abstract: Methods and apparatus for deploying RFID readers in an RFID environment that contains dense populations of tags are described. The RFID readers are deployed using a process that provides adequate link margins so that communication can be established with RFID tags in all regions of interest within the RFID environment.

Abstract: Radio-frequency identification (RFID) systems use readers to query and locate passive RFID tags in stores, warehouses, and other environments. A signal from the reader powers up the tag, which modulates and backscatters the signal toward the reader. Unfortunately, the maximum permitted RF signal power, self-interference at the reader, tag sensitivity, and channel loss limit the range at which readers can detect and locate tags. Using multiple readers simultaneously circumvents these limits. When used together, each reader transmits a signal to a tag in turn, and all of the readers listen for each of the tag's responses. The readers that are not transmitting do not experience self-interference and so can detect responses at lower power levels (longer ranges). Because the readers are at different locations, they measure different angles of arrival (AOAs) for each response. These simultaneous measurements can be used to locate each tag faster and with higher fidelity.

Abstract: Systems and methods for automated processing of item returns are disclosed. A method includes detecting, by a processor, that an item has been placed into a container. The processor may detect that the item has been placed into the container using one or more of computer vision, sensors, and/or RFID tag signals received from an RFID tag attached to the item. An RFID tag reader transmits first signals to the RFID tag and receives a response to the first signals from the RFID tag. The processor determines transaction data associated with the item based on the RFID tag response, including purchase amount, payment method, and purchase date. The processor then at least partially refunds an amount in response to the transaction data.

Abstract: Systems and methods for tracking items in a retail environment using combined computer vision (CV) and radio frequency identification (RFID) techniques are disclosed. In an exemplary embodiment, local camera nodes (LCNs) track a person through a retail environment and detect interactions between the person and an object or fixture in the environment. In response to detecting the interaction, an RFID sensor queries one or more RFID tags disposed in a sub-volume in which the interaction occurred. A system may determine that the person has picked up an object with an RFID tag, and both the person and the object may be tracked through the retail environment, including when the person exits the retail environment. Inventory may be managed and tracked using these combined CV and RFID techniques.

Abstract: Methods and apparatus for deploying RFID readers in an RFID environment that contains dense populations of tags are described. The RFID readers are deployed using a process that provides adequate link margins so that communication can be established with RFID tags in all regions of interest within the RFID environment.

Abstract: Methods and apparatus to detect RFID tags in motion or that have moved during a period of time. Inventory records that include locations of tags can be updated quickly and accurately for a large number of RFID-tagged objects in a region by querying and obtaining responses from only the portion of the RFID-tagged objects in the region that have moved or are moving.

Abstract: Methods and apparatus for estimating RFID tag locations in multipath environments are described. A plurality of RFID readers, sparsely placed reference tags, and constructed signal vectors can be used to estimate the location of RFID tags in a multipath environment.

Abstract: Methods and apparatus for deploying RFID readers in an RFID environment that contains dense populations of tags are described. The RFID readers are deployed using a process that provides adequate link margins so that communication can be established with RFID tags in all regions of interest within the RFID environment.

Abstract: Radio-frequency identification (RFID) tag readers or sensors interrogate and locate RFID tags in stores, warehouses, and other environments. Unfortunately, these sensors are vulnerable to intrusions, including attacks that can expose any computer network to which the sensors are coupled. Attacks like these can be prevented using a secure booting process for distributing and loading an operating system and/or other software onto each sensor. When the sensor first boots up, it validates a pair of locally stored binary files, e.g., using a pair of locally stored digital keys. Once booted, it establishes a secure connection to a controller, then downloads, validates, and executes a binary file from the controller. Executing the binary file from the controller loads an operating system kernel into the sensor's memory for secure operation.

Abstract: A radio frequency identification (RFID) system includes an array of antennas to distinguish line-of-sight (LOS) paths from non-line-of-sight (NLOS) paths. The distance between adjacent antennas in the array of antennas is less than half the wavelength of the radio frequency (RF) signal of the system. Each antenna in the antenna array is also digitally controlled to change relative phase difference among the antennas, thereby allowing digital steering of the array of antennas across angles of arrival (AOAs) between 0 and ?. The digital steering generates a plot of signal amplitudes as a function of AOAs. LOS paths are distinguished from NLOS paths based on the shapes (e.g., depth, gradient, etc.) of local extremes (e.g., maxima or minima) in the plot.

Abstract: A radio-frequency identification (RFID) tag, or tag, is affixed to a particular item and stores unique identifying information about that item. It can be queried with a reader that transmits wireless signals to the tag and receive the tag's responses, which can be correlated with information in inventory records. Conventionally, when a reader stops receiving a tag's responses to these queries, the inventory records are updated to show that the tag and associated item have been removed from the inventory. But a tag can stop producing detectable response for other reasons, including being too close to other tags, so simply removing the tag and item can lead to inaccurate inventory records. Stateful inventory technology address this problem by maintaining and transitioning tags among different states, including a stale state for tags that have not been read recently, depending on when and where the tags were last read.

Abstract: A radio frequency identification (RFID) system includes an array of antennas to distinguish line-of-sight (LOS) paths from non-line-of-sight (NLOS) paths. The distance between adjacent antennas in the array of antennas is less than half the wavelength of the radio frequency (RF) signal of the system. Each antenna in the antenna array is also digitally controlled to change relative phase difference among the antennas, thereby allowing digital steering of the array of antennas across angles of arrival (AOAs) between 0 and ?. The digital steering generates a plot of signal amplitudes as a function of AOAs. LOS paths are distinguished from NLOS paths based on the shapes (e.g., depth, gradient, etc.) of local extremes (e.g., maxima or minima) in the plot.