53 results about "Backscatter modulation" patented technology

A system and method is provided for locating objects using RFID tags. The system and method uses an RFID reader and a distance calculator to efficiently and accurately determine the location of objects that include an RFID tag. The RFID reader transmits a plurality of signals to the RFID tag, with the plurality of signals having different fundamental frequencies. In response, the RFID tag backscatter modulates the plurality of transmitted signals to create a plurality of backscatter modulated signals. The RFID reader receives and demodulates the plurality of backscatter modulated signals. The distance calculator determines the phase of the plurality of backscatter modulated signals and determines a rate of change of the phase in the backscatter modulated signals with respect to the rate of change in the fundamental frequency of the transmitted signals and uses this information to calculate the distance to the RFID tag.

An object location system and method is provided for locating objects. The system includes an RFID reader, an angle calculator, and a distance calculator to determine which of a plurality of zones an object is located in or passing through. An RFID tag is affixed with the object that is to be located. The RFID reader transmits signals to the RFID tag and receives backscatter-modulated signals from the RFID tag at one or more RFID antennas. From those received signals, the angle calculator determines an angle of position of the RFID tag relative to the RFID antenna. From the angle of position the zone in which the object is located is determined.

An RFID transponder for use in a security system based upon RFID techniques. The RFID transponder may be connected to an intrusion sensor. Example intrusion sensors are magnetically sensitive relay or LED detectors. The RFID transponder may also be connected to a passive infrared sensor. The RFID transponder can contain a battery, and the battery can be recharged by receiving and converting RF energy transmitted by the RFID reader. The security system also supports RFID transponders that may be carried by persons or animals, of that may contain a button used to signal an event such as an emergency. The RFID transponder typically uses backscatter modulation for responses, and can accept various modulation techniques for inbound wireless communications. The RFID transponder only responds when permitted.

A participatory athletic event timing system based on backscattering modulation in the UHF band and including wirelessly encoding writable data tags with participant's bib numbers or a calculated derivative thereof for timing participants in a participative athletic event, and attaching the data tags to the participant's bibs for distribution of the bibs and data tags to participants so as to eliminate the need for matching data tags with bibs and maintaining the sequenced order of the matched data tags and bibs. In a preferred embodiment, when participants register for the event, they are assigned an ID number and a bib printed with that number and having attached to the bib one or more data tag encoded in the tags memory the ID number or a calculated derivative thereof. Before the start of the event, the athlete pulls the data tag from the bib and attaches it to their shoe. Antennas suitably designed and adapted for use with the data tags in participative athletic events are used to communicate with the data tags.

The invention belongs to the technical field of wireless communications, and relates to a signal receiving method for a backscatter communication system. The signal receiving method provided by the invention is used for a traditional system with a communication system and an environment backscatter communication system coexisted, and detecting signals sent by the two systems at a joint receiver. A signal transmitted to the joint receiver by a label is modulated by taking a signal from a radio frequency source as a carrier wave; the label comprises one backscatter antenna; the antenna is connected with a load impedance switch and a radio frequency energy collection module; and the radio frequency energy collection module can collect energy from environmental signals. In order to transmit information bits to a reader through backscatter modulation, the label switches an antenna impedance switch, so as to change the amplitude and/or phase of backscattered signals to modulate received carrier signals, and finally, the backscattered signals are received and decoded by the joint receiver.

A communication device having radio frequency identification capabilities including an adapter of existing transmission and reception circuitry for transmitting an interrogation signal and receiving a backscatter modulated return signal. The device can be further modified to retransmit the backscatter modulated return signal, display the same to a user through an interface, or process the same in the device, or a combination of the foregoing. A communication device is also provided having RFID and other communication capabilities and software drivers are utilized to control operation of the device in an RFID interrogation mode.

An integrated passive radio frequency identification transponder chip includes a backscatter modulator for communication with a backscattering principle, a tag oscillator generating a backscattering modulation frequency, and a reference load, preferably a reference resonator. Either the reference load or at least one pair of an internal or external resonator and an external sensor element can be selectively connected to load the tag oscillator. Each external sensing element is arranged to sense a predetermined variable. The tag oscillator is capable of generating any one of nominal backscattering modulation frequencies defined for a respective RFID system, when the reference load is connected to load the tag oscillator. The tag oscillator is arranged to generate a predetermined one of nominal backscattering modulation frequencies, when the at least one pair of the internal or external resonator and the external sensor element is connected to load the tag oscillator.

Systems and methods for using a multimodal handheld reader are described. The reader can be used to read non electronic labels, passive RFID tags using backscatter modulation techniques and battery based active RFID tags using a single handheld. The reader deploys a multiplexed antenna design and thereby contains a method to read a group of passive RFID tags and at the same time the reader can isolate a single passive RFID tag from amongst a group of passive RFID tags within close proximity. All such passive RFID tags use backscatter modulation techniques and are in the readers own RF zone.

The invention relates to the radio frequency automatic identification technology of the field of the backscattering communication system, discloses an RFID read-write system capable of enhancing RFID read-write distance and a read-write method thereof, and solves the problems in the prior art that a passive RFID system is short in read-write distance. The RFID read-write method comprises the following steps that a. a reader-writer transmits a pilot signal to a tag; b. the tag backscatters the pilot signal; c. the reader-writer receives the pilot signal backscattered by the tag; d. the reader-writer estimates a backscattering channel; e. the reader-writer transmits an energy beam forming signal to the tag; f. the tag collects radio frequency signal energy; g. the reader-writer transmits an unmodulated carrier signal; h. and the tag transmits information back to the reader-writer through backscattering modulation by utilizing the collected energy. The read-write range of the RFID reader-writer can be greatly enhanced without increasing energy consumption of the transmitting end or increasing complexity of the tag so that the severe defect of restriction of short read-write distance of the RFID system can be effectively solved, and thus the RFID read-write system and the read-write method are suitable for realization of long-distance RFID read-write.

A radio frequency identification (RFID) reader sequentially carries out inventory rounds with passive RFID sensor tags. Each RFID sensor tag has at least one sensing element arranged to sense a predetermined quantity. The reader reads one value of the predetermined quantity based on a backscattering modulation frequency used by the passive RFID sensor tag during each inventory round and releases the RFID sensor tag prior to reading next value of the predetermined quantity based on a backscattering modulation frequency used by the passive RFID sensor tag during a subsequent inventory round. If the passive RFID sensor comprises two or more sensing elements having different sensor characteristics, the reader reads one of the sensing elements of the passive RFID tag during one inventory round and releases the passive RFID sensor tag prior to reading another one of the sensing elements of the passive RFID sensor tag during a subsequent inventory round.

The invention belongs to the technical field of automatic identification and in particular relates to a radio frequency identification system. The radio frequency identification system consists of a PC (Personal Computer) terminal, a reader, a reader antenna, a label antenna and a label chip, wherein the eigenfrequencies of a receiving module and a transmitting module of the reader are different, the transmitting carrier frequency of the reader is set as f0, and the backscatter carrier frequency of a label is set as F(sum0), wherein F indicates a certain function relationship. The transmitting carrier of the reader is subjected to simple transformation by using the label to obtain carriers with different frequencies so as to carry out backscatter modulation. According to the harmonic radio frequency identification system, self-interference and multipath interference of the radio frequency identification system can be greatly reduced, and therefore the sensitivity of the reader and the radio frequency identification system is improved.

The invention discloses an interception prevention method which adopts the backscatter modulation technology in the RF identification system and belongs to the RF identification technical field in the wireless communication; the technical proposal includes that when the reader-writer sends an instruction to the label, the fixed frequency of the carrier signal is changed to be changeable frequency, or the fixed phase of the carrier signal is changed to be changeable phase; when the reader-writer receives the label reply and sends a signal to the label, the fixed frequency of the carrier signal is changed to be changeable frequency, or the fixed phase of the carrier signal is changed to be changeable phase; meanwhile, the constant amplitude of the carrier signal is changed to be changeable amplitude. The communication mode of the reader-writer and the label is improved to prevent the third party receiver from demodulating the correct signal and realize the encryption in the transmission process of the RF identification system so that the interception prevention capability of the RF identification system is improved effectively and the safety of the RF identification system is enhanced.

The invention, which belongs to the technical field of the internet of things information system, provides a cross-protocol communication platform based on a passive sensing technology comprising a radio frequency front section, a receiver, a transmitter, a microcontroller and sensing equipment. The receiver is used for decoding the received signal, specifically comprises a detector, a peak valuediscovering device, a threshold value setting circuit and a comparator which are connected in sequence. The transmitter is used for transmitting communication signals of different protocols to achievecross-platform communication, adjustment is conducted by controlling digital transmission signals output by a microcontroller and impedance of a matching network, and modulation modes adopted by different platform communication protocols are output; according to the invention, multiple modulation modes are realized on one device through the backscatter modulation technology, the platform can adaptively communicate with multiple devices according to needs, and signals are generated only through the backscatter modulation technology, thereby playing a positive role in finally improving the mutual communication between different devices of the Internet of Things.

Two ambient backscatter modulation methods and embodiments are disclosed, pseudo FSK and shifted BPSK. Embodiments of a receiver of signals for those modulations are also disclosed. Both methods disclosed allow for frequency-based networking of multiple backscatter devices when signals from an ambient, modulated radio frequency (RF) source are used for illumination. Disclosed method and apparatus exploit the inherent variation of the ambient modulated illuminating signal and offers performance improvement. Aspects of the disclosed invention also provide methods for passive jamming of full duplex transceivers and methods for assisting RF source localization.

The invention provides a passive RFID tag utilizing visible light communication, which comprises an optical receiver, a decision circuit, a digital baseband, a numerical control switch, an RF backscattering modulation circuit and a power supply management circuit, wherein the optical receiver, the decision circuit, the digital baseband, the numerical control switch and the RF backscattering modulation circuit are sequentially connected, the digital baseband is further connected with a storage, the power supply management circuit is used for providing a stable supply voltage to the optical receiver, the decision circuit, the digital baseband, the storage, the numerical control switch and the RF backscattering modulation circuit, an output end of the RF backscattering modulation circuit is connected with an RF antenna, a power supply input end of the power supply management circuit is connected with a photocell, and an output end of the photocell is further connected with the optical receiver through a capacitor. According to the Passive RFID tag, a light source of an optical communication transmitter is used for providing energy to the tag, and the defect of being harmful to human body due to large electromagnetic radiation of the ordinary passive RF tag is effectively overcome; the emitter adopts RF backscattering modulation and the RF antenna, and the defects that the power consumption of the emitter in visible light communication is high and LED is hard to integrate can be overcome; and the overall power consumption of the tag is further reduced, and the chip integration of the tag is improved.

The invention relates to a wireless sensor suitable for health monitoring of a concrete structure. The wireless communication comprises a communication antenna, an energy extracting antenna, a variable matching network, a demodulator, a backscattering modulator, a controller, a physical energy extracting module, a memory and a sensor. The wireless sensor has the characteristics that the whole circuit is supplied with electric energy by the energy extracting antenna and the physical energy extracting type, a built-in power source is not needed, the difficulty in failure to replace the battery in the later period is avoided, and the manufacturing cost and later maintenance cost are greatly reduced; the variable matching network can complete the power matching at different input signal frequency according to the digital signal adjusting center frequency obtained by a frequency digital converter, so as to improve the reliability of the wireless sensor in working under the complicated concrete environment; the backscattering modulator is based on the radar backscattering principle, the zero-power consumption modulation is realized, and the circuit structure is simple.

In a RFID sensor tag, a sensing element is connected to an oscillator such that an oscillation frequency of the oscillator is dependent on a value of a predetermined variable sensed by the sensing element. The oscillation frequency of the oscillator is a harmonic multiple N of a modulation frequency required for a backscattering modulator. A frequency divider is arranged at the output of the oscillator to produce the modulation frequency from the oscillation frequency. The oscillator can be designed and dimensioned such that a high sensitivity is obtained with all sensor values, and the desired modulation frequency is derived resulting oscillation frequency by selecting a suitable division ratio N.