Resumen
Label, system and method for the detection of long-distance objects. The present invention describes a label comprising a magnetic element in the form of a microwire of 80-250 microns with a giant magnetoimpedance that, when attached to an object, allows its wireless detection by modulating the micrail's reflectivity. The detection is performed using a system that emits an electromagnetic wave of frequency between 1 and 20 ghz and a magnetic field of low frequency (0.01 - 50 hz) and detects the modulation of the reflectivity of the microwire. In this way, objects are detected at distances greater than 1 m. (Machine-translation by Google Translate, not legally binding)
Reivindicaciones
1. A tag comprising a magnetically soft microwire (active element) with a diameter between 80 and 250 microns, with giant magnetoimpedance properties, with a non-bistable hysteresis loop with transverse anisotropy between 10 and 20 Oe, a coercive field between 1 and 5 Oe for a low frequency exciter field with frequencies from 10 to 50,000 mHz and an amplitude between 0 and 25 Oe and the electric resonance frequency in high frequency thereof being conditioned by the geometric parameters thereof for excitation frequencies between 1 and 20 GHz. 2. The tag according to claim 1, which preferably comprises another magnetically hard element in the form of a magnetic wire with a diameter greater than 100 microns or a magnetic tape or a magnetic powder, the remanence of which is such that, in the proximity of the magnetically soft microwire, it creates a magnetic field around the coercive field thereof at the frequency of the exciter field. 3. The tag according to claim 2, wherein the hard magnetic element acts as a deactivator of the tag because, once the tag is used, the state of magnetization thereof can be modified by applying an intense magnetic field and the tag can be deactivated. 4. The tag, according to the preceding claims, wherein the microwire can be an extended microwire or a closed microwire, for example in the form of a ring, square or rectangle, with one or more turns. 5. The tag according to claim 4, wherein the dimensions of the microwire are comprised between 30 and 1 cm, the diameter of the ring between 0.5 and 10 cm, the side of the rectangle between 0.5 and 10 cm or the length of the powder microwires between 1 and 5 mm. 6. The tag according to the preceding claims, wherein the length of the microwire is 5 cm for a frequency of 3 GHz and 10 cm for a frequency of 1.5 GHz. 7. The tag according to the preceding claims, wherein the coercive field of the microwire increases as the frequency of the low frequency exciter field increases and the maximum variation of the reflectivity is produced for low frequency fields associated with coercive fields of the microwire between 1 and 20 Hz. 8. The tag according to claim 1, wherein the composition of the microwire is based on iron and cobalt with an amorphous or crystalline structure. 9. The tag according to claim 8, wherein the microwire has a composition of Fe<x> Co<a-x-y> Ni<y> Si<z> B<w> M<t> (where a+z+w+t=100, 70≤a-x-y≤75, 0≤x+y≤5, 0≤z+w≤25, 0≤t≤3, M=Nb, Mo, Hf). 10. The tag according to claims 8 and 9, wherein the magnetoimpedance of the microwire between 20 and 50% is controlled by the nanocrystallization percentage thereof, between 0 and 10%. 11. The tag, according to claims 8 to 10, wherein the microwire has a magnetostriction constant that is virtually null, the values of which are comprised between -1 ppm and -0.05 ppm, with an anisotropy field of no less than 10 Oe and no greater than 20 Oe, with a diameter of the metal core of a value comprised between 30 and 250 microns and a coercive field between 0.5 and 250 Oe (for frequencies of a low frequency exciter field of 0.01 and 50 Hz) and an electric resonance frequency of these geometries is conditioned by the geometric parameters thereof at the frequency interval between 1 and 20 GHz. 12. A use of the tag claimed for the detection of objects. 13. The use according to claim 12 for the detection of objects at a distance greater than 2 meters. 14. A system for the long-distance detection of objects wherein the object has the claimed tag and which comprises: - A transmitting sensor connected to a transmitting antenna that transmits a wave with a frequency between 1 and 20 GHz. - A generator system generating low frequency signals comprised between 10 and 50,000 mHz for the creation of a magnetic field with low frequency alternating modulation with which a continuous field in the area of detection is superposed. - The receiver system which collects the variations in the reflectivity of the microwire of the tag, modulated by the superposition of the continuous and low frequency magnetic fields, respectively. - A controller system connected to the transmitting device, to the receiver and to the low frequency signal generator. 15. The detection system according to claim 14, which comprises a first electric circuit fed by a low frequency sinusoidal signal with which another direct current (DC) is superposed which feeds a coil, able to be camouflaged with the floor, which generates a magnetic field lower than the anisotropy field of the microwire used. Said current allows for periodic magnetization and demagnetizaion of the soft magnetic microwire placed on the tag. The system comprises a second circuit for transmitting and receiving, by means of both transmitting and receiving antennas, a high frequency signal such that the frequency coincides with the electric resonance frequency of the chosen microwire. Furthermore, the system comprises means for processing the signal, establishing a detection threshold. 16. The detection system according to claim 14 and 15 wherein the frequency of the low frequency magnetic field to be used is determined by the evolution with the frequency of the coercive field of the magnetic microwire to be detected. 17. The detection system, according to claims 14 to 16, wherein the generation of the low frequency magnetic field is done by means of coils that are camouflaged with the floor. 18. The detection system, according to claims 14 to 16, wherein the generation and the detection of the waves is done by means of coils that are camouflaged with the floor. 19. A method for the long-distance detection of objects using the claimed system, the detection of which is done by modulating the reflectivity of the microwire by means of the superposition of the continuous and low frequency magnetic fields which comprises: - Transmitting an electromagnetic wave with a frequency between 1 and 20 GHz. - Creating an alternating low frequency magnetic field, which has a frequency between 10 and 5000 mHz and an amplitude between 0 and 25 Oe. - Superposing a direct current (DC) with the alternating low frequency magnetic field which generates a magnetic field below the anisotropy field of the microwire used. - Measuring the reflectivity of the microwire as a function of time and frequency of the low frequency field. 20. The method according to claim 19, wherein the modulation of the reflectivity of the microwire involves the modulation of the GHz wave in the presence of said microwire and the detection thereof is done by means of an antenna by the modulated wave in GHz in the presence of a magnetic active element subjected to a low frequency magnetic field. 21. The method, according to claim 19, wherein maximum detection is produced for the smallest possible frequency of the low frequency field.
