The invention relates to a method of reading RF transponders disposed in one and the same magnetic interrogation field, in which a magnetic coupling of the transponders is ensured with a passive resonant circuit during reading. The method is distinguished in that the passive antenna of the resonant circuit is associated with at least one transponder antenna, and the passive resonant circuit is tuned in such a way that the resonant frequency resulting from the association corresponds to one of the frequencies of the emission side bands of the transponder to be read. The invention also relates to the system corresponding to the method, a transponder structure and an object containing the transponder, in particular a travel document.

The RFID sensor tag may include normal RFID circuits and functions (such as rectifier, modulator, logic and memory) as well as a resonator-based clock generator or oscillator. The oscillator is a stable resonator-based oscillator having a high Q value. The resonator-based oscillator is loaded with a sensor element which tunes the oscillation frequency, i.e. the oscillation frequency is sensitive to the measured quantity. Thereby, a passive RFID sensor with a resonator-based oscillator and a sensor element is provided, wherein the oscillation frequency can be made dependent on the sensor element if sensing is required. The concept is compatible for existing RFID tags and can enable the possibility to measure external quantities with-out reducing the read-out distance.

RFID tags are used for many purpose including tracking RFID interrogators are used to retrieve information from tags. In many applications, RFID interrogators and RFID tags remain stationary during interrogation. Regions of low energy due to interference from either additional antenna or reflections from RFID tags and objects can impede or prohibit the reading of RFID tags residing in such regions. Stirring of the generated electromagnetic field is a method of moving around the regions of low energy, where tags can not be read, during the interrogation process. Mechanical stirring is accomplished by introducing a conductor into the electromagnetic field and moving it about in the field. Solid state stirring is accomplished by introducing a variable conductor into the field and varying the conductivity of the variable conductor. Mathematical stirring is accomplished by use of a plurality of antenna and controlling the phase difference between the antenna in a configuration known as phased antenna arrays.

RFID tags are used for many purpose including tracking. RFID interrogators are used to retrieve information from tags. In many applications, a plurality of RFID interrogators are required. Synchronization between interrogators in the same theatre of operation is critical to ensure that their broadcasts do not interfere with each other. In fixed RFID interrogator applications, RFID interrogators can be wired together allowing a channel to synchronize the transmissions of the RFID interrogators. Methods described herein can ensure that synchronization is maintained in the event of the failure of a synchronizing master. Furthermore, additional methods for synchronizing RFID interrogators in wireless applications are described allowing synchronization in the absence of wired connections between interrogators.

RFID tags are used for many purpose including tracking. RFID interrogators are used to retrieve information from tags. In many applications, a plurality of RFID interrogators are required. Synchronization between interrogators in the same theatre of operation is critical to ensure that their broadcasts do not interfere with each other. In fixed RFID interrogator applications, RFID interrogators can be wired together allowing a channel to synchronize the transmissions of the RFID interrogators. Methods described herein can ensure that synchronization is maintained in the event of the failure of a synchronizing master. Furthermore, additional methods for synchronizing RFID interrogators in wireless applications are described allowing synchronization in the absence of wired connections between interrogators.

A breakaway RFID tag is configured such that it comprises part of a Printed Circuit Board Assembly (PCB). Thus, the breakaway RFID tag can be used to track the PCB as it migrates through a manufacturing process. In one embodiment, the RFID tag can be assembled first and then used to track the PCB as it is populated with components and installed into larger assemblies and ultimately into the end device. Once the PCB is installed into a larger assembly or the end device, the breakaway RFID tag is configured such that it can be broken off and attached to the outside of the larger assembly or end device.

RFID tags are used for many purpose including tracking. RFID interrogators are used to retrieve information from tags. In many applications, a plurality of RFID interrogators are required. Synchronization between interrogators in the same theatre of operation is critical to ensure that their broadcasts do not interfere with each other. In fixed RFID interrogator applications, RFID interrogators can be wired together allowing a channel to synchronize the transmissions of the RFID interrogators. Methods described herein can ensure that synchronization is maintained in the event of the failure of a synchronizing master. Furthermore, additional methods for synchronizing RFID interrogators in wireless applications are described allowing synchronization in the absence of wired connections between interrogators.

RFID tags are used for many purpose including tracking. RFID interrogators are used to retrieve information from tags. In many applications, a plurality of RFID interrogators are required. Synchronization between interrogators in the same theatre of operation is critical to ensure that their broadcasts do not interfere with each other. In fixed RFID interrogator applications, RFID interrogators can be wired together allowing a channel to synchronize the transmissions of the RFID interrogators. Methods described herein can ensure that synchronization is maintained in the event of the failure of a synchronizing master. Furthermore, additional methods for synchronizing RFID interrogators in wireless applications are described allowing synchronization in the absence of wired connections between interrogators.

A breakaway RFID tag is configured such that it comprises part of a Printed Circuit Board Assembly (PCB). Thus, the breakaway RFID tag can be used to track the PCB as it migrates through a manufacturing process. In one embodiment, the RFID tag can be assembled first and then used to track the PCB as it is populated with components and installed into larger assemblies and ultimately into the end device. Once the PCB is installed into a larger assembly or the end device, the breakaway RFID tag is configured such that it can be broken off and attached to the outside of the larger assembly or end device.

The invention relates to a method of reading RF transponders disposed in one and the same magnetic interrogation field, in which a magnetic coupling of the transponders is ensured with a passive resonant circuit during reading. The method is distinguished in that the passive antenna of the resonant circuit is associated with at least one transponder antenna, and the passive resonant circuit is tuned in such a way that the resonant frequency resulting from the association corresponds to one of the frequencies of the emission side bands of the transponder to be read. The invention also relates to the system corresponding to the method, a transponder structure and an object containing the transponder, in particular a travel document.