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An antenna generating an electromagnetic field for an electromagnetic transponder and a terminal provided with such an antenna. The antenna comprises a first inductive element designed to be connected to two terminals employing an energizing voltage, and a parallel resonant circuit coupled with the

An antenna generating an electromagnetic field for an electromagnetic transponder and a terminal provided with such an antenna. The antenna comprises a first inductive element designed to be connected to two terminals employing an energizing voltage, and a parallel resonant circuit coupled with the first inductive element.

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1. An apparatus comprising: an antenna for generating an electromagnetic field for an electromagnetic transponder, the antenna comprising: a first inductive element operative to connect to two terminals of application of an excitation voltage; anda parallel resonant circuit coupled with the first in

1. An apparatus comprising: an antenna for generating an electromagnetic field for an electromagnetic transponder, the antenna comprising: a first inductive element operative to connect to two terminals of application of an excitation voltage; anda parallel resonant circuit coupled with the first inductive element to extend a range of an electromagnetic field emitted by the first inductive element, andwherein the parallel resonant circuit comprises a second inductive element and a control switch connected to the second inductive element. 2. The antenna of claim 1, wherein the control switch is connected in parallel with the second inductive element. 3. The antenna of claim 1, wherein the control switch is connected in series with the second inductive element. 4. An apparatus comprising: an antenna for generating an electromagnetic field for an electromagnetic transponder, the antenna comprising: a first inductive element operative to connect to two terminals of application of an excitation voltage; anda parallel resonant circuit coupled with the first inductive element to extend a range of an electromagnetic field emitted by the first inductive element,wherein the parallel resonant circuit comprises a second inductive element and a control switch connected to the second inductive element,wherein the first inductive element is formed of several inductances organized in a network, andwherein the several inductances comprise seven planar windings. 5. The antenna of claim 4, wherein the seven windings are distributed in a honeycomb formation, such that each side of one planar winding of the seven planar windings is adjacent to a single side of each of the other six planar windings of the seven planar windings. 6. An apparatus comprising: an antenna for generating an electromagnetic field for an electromagnetic transponder, the antenna comprising: a first inductive element operative to connect to two terminals of application of an excitation voltage; anda parallel resonant circuit coupled with the first inductive element to extend a range of an electromagnetic field emitted by the first inductive element,wherein the parallel resonant circuit comprises a second inductive element and a control switch connected to the second inductive element,wherein the first inductive element and the second inductive element are formed of planar windings, andwherein a value of the second inductive element is greater than a value of the first inductive element. 7. An apparatus comprising: an antenna comprising: a first inductive element configured to connect to an excitation signal; anda resonant circuit to extend a range of an electromagnetic field emitted by the first inductive element, the resonant circuit being configured to inductively couple to the first inductive element, the resonant circuit comprising a second inductive element and a control switch connected to the second inductive element,wherein the first inductive element and the second inductive element each comprise a planar winding,wherein a plane of the first inductive element and a plane of the second inductive element are substantially parallel, andwherein the first inductive element comprises a plurality of planar windings. 8. The antenna of claim 7, wherein the planar winding of the second inductive element has a substantially same planar shape and size as a planar shape and size of a perimeter of the plurality of planar windings. 9. The antenna of claim 7, wherein at least one planar winding of the plurality of planar windings has a substantially hexagonal geometry. 10. The antenna of claim 7, wherein the plurality of planar windings includes seven planar windings, each winding of the seven planar windings having a substantially hexagonal geometry. 11. The antenna of claim 10, wherein the seven planar windings are distributed in a honeycomb formation, such that each side of one planar winding of the seven planar windings is adjacent to a single side of each of the other six planar windings of the seven planar windings. 12. An apparatus comprising: an antenna comprising: a first inductive element configured to connect to an excitation signal; anda resonant circuit to extend a range of an electromagnetic field emitted by the first inductive element, the resonant circuit being configured to inductively couple to the first inductive element, the resonant circuit comprising a second inductive element and a control switch connected to the second inductive element,wherein the first inductive element and the second inductive element each comprise a planar winding,wherein a plane of the first inductive element and a plane of the second inductive element are substantially parallel,wherein the resonant circuit further comprises a first capacitor, and wherein the first capacitor is connected in parallel to the second inductive element, andwherein a value of the first capacitor and a value of the second inductive element define a natural frequency approximately equal to a frequency of the excitation signal. 13. An apparatus comprising: an antenna comprising: a first inductive element configured to connect to an excitation signal; anda resonant circuit to extend a range of an electromagnetic field emitted by the first inductive element, the resonant circuit being configured to inductively couple to the first inductive element, the resonant circuit comprising a second inductive element,wherein the first inductive element and the second inductive element each comprise a planar winding,wherein a plane of the first inductive element and a plane of the second inductive element are substantially parallel,wherein the resonant circuit further comprises a first capacitor, and wherein the first capacitor is connected in parallel to the second inductive element, andwherein the resonant circuit further comprises a switch. 14. The antenna of claim 13, wherein the switch is in parallel with the second inductive element. 15. The antenna of claim 13, wherein the switch is in series with the second inductive element. 16. An apparatus comprising: an antenna comprising:a first inductive element configured to connect to an excitation signal; anda resonant circuit to extend a range of an electromagnetic field emitted by the first inductive element, the resonant circuit being configured to inductively couple to the first inductive element, the resonant circuit comprising a second inductive element and a control switch connected to the second inductive element,wherein the first inductive element and the resonant circuit are disposed on a same substrate. 17. An apparatus comprising: an antenna comprising:a first inductive element configured to connect to an excitation signal; and a resonant circuit to extend a range of an electromagnetic field emitted by the first inductive element, the resonant circuit being configured to inductively couple to the first inductive element, the resonant circuit comprising a second inductive element and a control switch connected to the second inductive element,wherein the first inductive element and the resonant circuit are disposed on a same substrate wherein the first inductive element comprises a plurality of planar windings. 18. The antenna of claim 17, wherein the second inductive element comprises a planar winding, and wherein the planar winding of the second inductive element has a substantially same planar shape and size as a planar shape and size of a perimeter of the plurality of planar windings. 19. The antenna of claim 17, wherein at least one planar winding of the plurality of planar windings has a substantially hexagonal geometry. 20. The antenna of claim 17, wherein the plurality of planar windings includes seven planar windings, each winding of the seven planar windings having a substantially hexagonal geometry. 21. The antenna of claim 20, wherein the seven planar windings are distributed in a honeycomb formation, such that each side of one planar winding of the seven planar windings is adjacent to a single side of each of the other six planar windings of the seven planar windings. 22. An apparatus comprising: an antenna comprising: a first inductive element configured to connect to an excitation signal; anda resonant circuit to extend a range of an electromagnetic field emitted by the first inductive element, the resonant circuit being configured to inductively couple to the first inductive element, the resonant circuit comprising a second inductive element and a switch connected to the second inductive element,wherein the first inductive element and the resonant circuit are disposed on a same substrate,wherein the resonant circuit further comprises a first capacitor, and wherein the first capacitor is connected in parallel to the second inductive element, andwherein a value of the first capacitor and a value of the second inductive element define a natural frequency approximately equal to a frequency of the excitation signal. 23. The antenna of claim 22, wherein the switch is in parallel with the second inductive element. 24. The antenna of claim 22, wherein the switch is in series with the second inductive element. 25. A terminal for generating a high-frequency electromagnetic field for at least one transponder entering this field, the terminal comprising: an antenna for generating an electromagnetic field for the at least one transponder, the antenna comprising: a resonant circuit and an excitation circuit magnetically coupled to the resonant circuit, the excitation circuit including a first inductive element and having no capacitive element, said resonant circuit including a second inductive element and a control switch connected to the second inductive element, a value of which is chosen to be greater than a value of the first inductive element with a ratio depending on a desired field amplification for extending a range of an electromagnetic field emitted by the excitation circuit. 26. The terminal of claim 25, further comprising a current transformer connected to the resonant circuit. 27. The terminal of claim 25, further comprising a current transformer connected to the excitation circuit. 28. The terminal of claim 25, wherein the first inductive element comprises seven planar windings. 29. The terminal of claim 28, wherein the seven windings are distributed in a honeycomb formation, such that each side of one planar winding of the seven planar windings is adjacent to a single side of each of the other six planar windings of the seven planar windings. 30. The terminal of claim 25, wherein the control switch is connected in series with the second inductive element. 31. The terminal of claim 25, wherein the control switch is connected in parallel with the second inductive element. 32. The terminal of claim 25, wherein the resonant circuit is formed of the second inductive element and of a capacitive element in parallel, and is tuned to the frequency of an excitation signal of the first inductive element.