Rfid tags having ferromagnetic patches
AssigneeSRI International
InventorsXiao-Dong Xiang, Zhi-Gang Yu, Huan-Hua Wang
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Abstract
RFID tags and devices disclosed herein make use ferromagnetic films to store information. The tags include patches of ferromagnetic materials, each patch having a particular ferromagnetic resonance frequency determined by the composition of the ferromagnetic film. When stimulated, the patches emit microwave or RF signals at their resonance frequencies and at intensities proportional to the patch sizes. The signals are read and the frequency spectrum of the tag may be determined by using a FFT. Identity and other information may be provided by the spectrum.
Claims26
An RFID tag comprising:
- (a) at least one permanent magnet providing a substantially homogeneous magnetic field to a region of the RFID tag;
- and
- (b) one or more ferromagnetic patches provided in the region of substantially homogeneous magnetic field;
- wherein each patch has a defined ferromagnetic resonance frequency and size such that when exposed to microwave or radio frequency stimulation;
- it emits a signal at the defined resonance frequency at an intensity proportional to the size.
An RFID communication system comprising:
- a) a station having a receiver and a transmitter;
- and
- b) an RFID tag configured to communicate with the station;
- the RFID tag comprising:
- (i) at least one permanent magnet providing a substantially homogeneous magnetic field to a region of the RFID tag;
- and
- (ii) one or more ferromagnetic patches provided in the region of substantially homogeneous magnetic field;
- wherein each patch has a defined ferromagnetic resonance frequency and size such that when exposed to microwave or radio frequency stimulation;
- it emits a signal at the defined resonance frequency at an intensity proportional to the size.
A method of identifying an object comprising:
- a) sending a broadband signal to an RFID tag attached to the object to excite ferromagnetic patches on the tag;
- b) receiving resonance signals associated with the patches;
- and
- c) determining a frequency spectrum of the tag.
Dependencies are inferred from the claim text.