A method for detecting RFID tags attached to items positioned at a radio frequency identification (RFID) self-service checkout station is presented. The method includes creating one or more virtual shields at the RFID self-service checkout station, the one or more virtual shields defining checkout bins, associating RFID readers to the checkout bins, and enabling an RFID reader associated with the checkout bins to differentiate between RFID tags attached to items positioned inside a checkout bin and RFID tags attached to items positioned outside the checkout bin by at least determining a signal strength of each RFID tag detected by the RFID reader and estimating, based on an outcome of the signal strength of each RFID tag, a distance between each RFID reader and each RFID tag.

A method for detecting receivers includes a step of detecting a receiver, in which step a general controller detects an adjustable receiver when a general antenna receives a secondary wave emitted by the adjustable receiver, followed by a reconfiguration step in which the general controller commands a controller of the detected adjustable receiver to switch to an interaction mode in which the impedance of the adjustable receiver is alternated between a first configuration impedance and a second configuration impedance in order to detect other receivers. The reconfiguration step is of a duration that is an order of magnitude higher than the duration of each alternation of the first and second configuration impedances.

A radio frequency identification (RFID) system for frequency multiplexing includes, in an exemplary embodiment, an RFID interrogator configured for generating an RFID signal, wherein a channel frequency of the RFID signal changes over time within an operating bandwidth; and one or more electromagnetic transmissive elements each extending between a first end thereof and a second end thereof, each of the electromagnetic transmissive elements electrically coupled with the RFID interrogator at the first end thereof, each of the electromagnetic transmissive elements comprising a frequency dependent load at the second end thereof and configured for transmitting the RFID signal from the RFID interrogator to the frequency dependent load, wherein the frequency dependent load presents different electromagnetic characteristics to the RFID signal transmitted to the frequency dependent load depending on the channel frequency of the RFID signal. Other embodiments include a method for frequency multiplexing including similar components.

Devices and methods for reading multiple types of RFID tags having different frequencies and or encoding schemes are disclosed. One or more search signals covering a plurality of RFID bands are transmitted. A presence indication of an RFID tag in one of the plurality of RFID bands is detected. An interrogating signal having a carrier frequency tuned to a frequency at which the presence indication is detected is transmitted. A tag response signal comprising tag information associated with the RFID tag is received. A digital response signal based on the tag response signal is digital signal processed to obtain the tag information.

An apparatus, system, and method for wireless communication with remote devices that reduce or eliminate interference from zero-mean noise and deterministic signals within the operating system frequency band are provided. An interrogator uses dithering of the initiation time of sequential transmitted signals or sets of transmitted signals with synchronous accumulation of the resulting received signals to reduce the relative strength of interfering signals while increasing the relative strength of the desired signal. The apparatus, system, and method are particularly advantageous when used to extract identification and/or sensor data from passive wireless sensors and tags.

Disclosed is a system for electromagnetic interrogation of RFID transponders including at least one RFID terminal configured to emit an interrogation signal at a frequency F1, at least one RFID device referred to as repeater configured to receive the interrogation signal with frequency F1 and to repeat same towards at least one RFID transponder at the frequency F2, characterised in that the at least one RFID terminal includes at least one RFID reader configured to emit an interrogation signal with frequency F0 and at least one add-on RFID device configured to perform a frequency transposition from the frequency F0 to the frequency F1, the frequencies F0 and F1 being different.

A multi-protocol RFID interrogating system employs a synchronization technique (step-lock) for a backscatter RFID system that allows simultaneous operation of closely spaced interrogators. The multi-protocol RFID interrogating system can communicate with backscatter transponders having different output protocols and with active transponders including: Title 21 compliant RFID backscatter transponders; IT2000 RFID backscatter transponders that provide an extended mode capability beyond Title 21; EGOTM RFID backscatter transponders, SEGOTM RFID backscatter transponders; ATA, ISO, ANSI AAR compliant RFID backscatter transponders; and IAG compliant active technology transponders. The system implements a step-lock operation, whereby adjacent interrogators are synchronized to ensure that all downlinks operate within the same time frame and all uplinks operate within the same time frame, to eliminate downlink on uplink interference.

Systems and methods for backscatter communications are provided that employ a backscatter reader to transmit a carrier signal to multiple backscatter tags having heterogeneous hardware and specifications. In response to receiving the carrier, the tags encode data into the received signal and, concurrently, transmit their respective backscattered signal to the reader. The concurrent signals are received by the reader as a combined signal. The reader detects edges in the received signal, based on the corresponding in-phase (I) and quadrature (Q) signals. The edges are then assigned to streams based on the offset or transmission rate of the tags. In some cases, the reader can detect edge collisions. These collisions can be resolved by causing the colliding signals to be retransmitted or by separating the colliding signals. The individual streams corresponding to each of the tags can then be decoded to identify the originally transmitted data from each tag.

Embodiments provide an RFID reader. The RFID reader includes a collision detector, a decoder and a frame length adjuster. The collision detector is configured to detect for each slot of a plurality of slots of a current frame, in which a collision of signals transmitted by at least two RFID tags occurred, a signal property of a signal of the signals transmitted by at least two RFID tags. The decoder is configured to decode for the slot in which the collision is detected the signal of the signals transmitted by the at least two RFID tags using the detected signal property, wherein a collision recover probability describing a probability that the decoder can accurately decode the one signal depends on a signal-to-noise ratio (SNR) of the current frame. The frame length adjuster is configured to adjust a frame length of a subsequent frame in dependence on the collision recover probability.

An incontinence detection system monitors an area for moisture events and wirelessly transmits moisture-related information to one or more notification devices. The system has a pad that includes a substrate and one or more sensors supported by the substrate. The sensor(s) emit wireless signals indicative of the moisture-related information. A sensor event communication system forwards the sensor signals to another device, such as a notification device. Portions of the system are included in a patient support apparatus, such as a bed.