Enhancing magneto-impedance modulation using magnetomechanical resonance

1. A security tag, comprising:

a marker comprising magnetostrictive material having magnetomechanical and magnetoimpedance properties, said marker configured to generate a modulated reply signal in response to a first excitation signal and a modulation signal, said marker to receive a second excitation signal to cause said marker to resonate at a resonant frequency, with said resonance causing an increase in gain of said modulated reply signal when said magnetostrictive material resonates at said resonant frequency.

2. The security tag of claim 1 , wherein said first excitation signal comprises a microwave signal.

3. The security tag of claim 1 , wherein said first excitation signal comprises one of a 2.45 GigaHertz microwave signal and 915 MegaHertz microwave signal.

4. The security tag of claim 1 , wherein said magnetostrictive material is formed by annealing.

5. The security tag of claim 1 , wherein said resonant frequency comprises approximately 58 KiloHertz.

6. The security tag of claim 1 , wherein said magnetostrictive material has a composition of at least one of Fe 81 B 13.5 Si 3.5 C 2 and Fe 40 Co 40 B 18 Si 2 .

7. The security tag of claim 1 , wherein said magnetostrictive material is annealed at 410 centigrade for 30 seconds in a saturation magnetic field across a width of said material.

8. The security tag of claim 1 , wherein said first excitation signal is an electromagnetic first signal within a first frequency range Δf 1 , and said modulation signal is a magnetic second signal within a second frequency range Δf 2 , where Δf 1 >>Δf 2 , and said modulated reply signal is an electromagnetic third signal composed by said first signal, an amplitude of which is modulated by said second signal.

9. The security tag of claim 1 , wherein said first excitation signal is an electromagnetic first signal within a first frequency range Δf 1 , and said modulation signal is a magnetic second signal within a second frequency range Δf 2 , where Δf 1 >>Δf 2 , and said modulated reply signal is an electromagnetic third signal composed by said first signal, a frequency of which is modulated by said second signal.

10. A system, comprising:

a first transmitter to transmit an excitation signal within a surveillance zone;

a security tag to receive said excitation signal, said security tag comprising a magnetoimpedance marker positioned within said security tag body, said magnetoimpedance marker comprising magnetostrictive material configured to resonate at a resonant frequency, said marker to receive a first excitation signal and modulation signal to generate a modulated reply signal, and a second excitation signal to cause said marker to resonate at said resonant frequency, with said resonance to cause said modulated reply signal to have an increase in gain;

a receiver to receive said modulated reply signal; and

a controller to detect said security tag within said surveillance zone and output a detect signal.

11. The system of claim 10 , further comprising an alarm system to couple to said controller, said alarm system to receive said detect signal and generate an alarm in response to said detect signal.

12. The system of claim 10 , wherein said first excitation signal comprises a microwave signal.

13. The system of claim 10 , wherein said first excitation signal comprises one of a 2.45 GigaHertz microwave signal and a 915 MegaHertz microwave signal.

14. The system of claim 10 , wherein said magnetostrictive is formed by annealing.

15. The system of claim 10 , wherein said resonant frequency comprises approximately 58 KiloHertz.

16. The system of claim 10 , wherein said magnetostrictive material has a composition of at least one of Fe 81 B 13.5 Si 3.5 C 2 and Fe 40 Co 40 B 18 Si 2 .

17. The system of claim 10 , wherein said magnetostrictive material is annealed at 410 centigrade for 30 seconds in a saturation magnetic field across a width of said material.

18. The system of claim 10 , wherein said first excitation signal is an electromagnetic first signal within a first frequency range Δf 1 , and said modulation signal is a magnetic second signal within a second frequency range Δf 2 , where Δf 1 >>Δf 2 , and said modulated reply signal is an electromagnetic third signal composed by said first signal, an amplitude of which is modulated by said second signal.

19. The system of claim 10 , wherein said first excitation signal is an electromagnetic first signal within a first frequency range Δf 1 , and said modulation signal is a magnetic second signal within a second frequency range Δf 2 , where Δf 1 >>Δf 2 , and said modulated reply signal is an electromagnetic third signal composed by said first signal, a frequency of which is modulated by said second signal.

20. A method, comprising:

receiving a first excitation signal at a marker;

generating a reply signal in response to said first excitation signal;

receiving a modulation signal at said marker;

modulating said reply signal in response to said modulation signal to form a modulated reply signal; and

receiving a second excitation signal at said marker, said second excitation signal to cause said marker to resonate at a resonant frequency, with said resonance causing an increase in gain of said modulated reply signal.

21. The method of claim 20 , wherein said first excitation signal has a higher frequency than said second excitation signal.

22. The method of claim 20 , wherein said first excitation signal is a microwave signal.

23. A security tag, comprising:

a marker comprising magnetostrictive material having magnetomechanical and magnetoimpedance properties, said marker configured to generate a modulated reply signal in response to an excitation signal and a modulation signal, said modulation signal to cause said marker to resonate at a resonant frequency, with said resonance causing an increase in gain of said modulated reply signal when said magnetostrictive material resonates at said resonant frequency.

24. The security tag of claim 23 , wherein said excitation signal comprises a microwave signal.

25. The security tag of claim 23 , wherein said excitation signal comprises one of a 2.45 GigaHertz microwave signal and 915 MegaHertz microwave signal.

26. The security tag of claim 23 , wherein said resonant frequency comprises approximately 58 KiloHertz.