What is claimed is:
1. A circuit for demodulating a signal transmitted by an electromagnetic transponder, comprising:
a sensor (7) of a variable which is a function of the load formed by the transponder on an oscillating circuit (L1, C1);
a phase demodulator (6) and an amplitude demodulator (22) at least functionally in parallel and receiving a signal coming from said sensor;
a summer (29) of the results provided by said demodulators; and
a delay element (31) in series with a first one of said demodulators, to compensate for a possible propagation time difference therebetween.
2. The circuit of claim 1, further comprising a regulator (50) of the delay introduced by said delay element (31) according to the signal provided by said summer (29).
3. The circuit of claim 1, wherein said first demodulator to which the delay element (31) is associated is the amplitude demodulator (22).
4. The circuit of claim 1, wherein said regulator (50) comprises:
a rectifying element (53) having its input connected to the summer output (29);
a comparator (54) having a first input receiving the signal provided by said filter and having a second input receiving a reference signal (ENT), the comparator output controlling said delay element (31).
5. The circuit of claim 1, wherein said delay element (31) is formed of a controllable resistive element (51) in series with said first demodulator (22), and of a capacitive element (52) connecting a terminal of the resistive element to a reference voltage.
6. The circuit of claim 5, wherein said resistive element (51) is formed of a field-effect transistor, a gate of which receives a regulation signal provided by said regulator (50) and which conditions its series resistance.
7. The circuit of claim 1, wherein said demodulators (6, 22), summer (29), delay element (31), and regulator (50) are made in the form of a digital signal processor.
8. The circuit of claim 1, wherein said sensor (7) measures the current (I) in the oscillating circuit (L1, C1), or the voltage across one or several of its elements.
9. A terminal (20) of generation of an electromagnetic field capable of communicating with at least one transponder (10) when said transponder enters this field, comprising the demodulation circuit (21) of any of claims 1 to 8.
10. A method for demodulating a signal transmitted by an electromagnetic transponder consisting of:
measuring a variable which is a function of the load formed by the transponder on an oscillating circuit (L1, C1);
demodulating in phase the measured signal;
demodulating in amplitude the measured signal;
delaying a first result of at least one of the demodulations with respect to the other;
summing up the results of the two demodulations; and
regulating the delay brought to said first demodulation result according to the result of the sum integration.
11. The method of claim 10, implemented by digital processing means.
12. The method of claim 10, implemented by analog circuits.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. to 17. (canceled)
18. A method of producing a coil component, comprising the steps of forming a coil section having a through hole, and forming a package member by covering the coil section with a package member and causing terminals connected to the coil section to project from the package member, wherein
in the step of forming the coil section, a plurality of ring sections formed of a metallic flat plate disposed in a plane and connected to each other by ring connecting sections are formed, and the ring sections are bent at the ring connecting sections and placed one on top of another, and
each ring section is formed of an arc-shaped portion having a slit formed by cutting a part of the ring section, each ring connecting section is formed at an end section of the arc-shaped portion of the ring section where the ring sections are connected to each other, and each terminal is formed at an end section of the arc-shaped portion of the ring section where the ring sections are not connected to each other.
19. The method of producing the coil component according to claim 18, wherein in the plurality of the ring sections formed of a metallic flat plate disposed in a plane, a sum of an angle formed by center lines each connecting centers of the ring sections adjacent to each other and connected by the ring connecting section, and angles each formed by the center line of the ring section connected to the terminal and an extension line extending from the center of the ring section toward the end section formed with the terminal is approximately 180\xb0.
20. The method of producing a coil component according to claim 18, wherein each terminal is provided on an extension line extending from a center of the ring section toward the end section formed with the terminal.
21. The method of producing a coil component according to claim 18, wherein each ring connecting section is formed with a groove for bending.
22. The method of producing a coil component according to claim 21, wherein each groove is formed in a direction perpendicular to a center line connecting centers of the ring sections adjacent to each other and connected by the ring connecting section.
23. The method of producing a coil component according to claim 18, wherein a projection extending toward the slit is formed at each end section of the arc-shaped portion of the ring section where the ring sections are connected to each other.
24. The method of producing a coil component according to claim 18, wherein the ring sections have substantially equal outside diameters.
25. The method of producing a coil component according to claim 18, wherein peripheral edge portions of the ring sections are chamfered.
26. The method of producing a coil component according to claim 18, wherein a step is formed on each terminal provided at the end section of the arc-shaped portion of the ring section where the ring sections are not connected to each other, and the steps formed on one terminal and the other terminal are arranged to be in such directions that the terminals approach each other when the ring sections are placed one on top of another in a same phase.
27. The method of producing a coil component according to claim 18, wherein each ring section, excluding the ring connecting section, is provided with an insulating coating layer.
28. The method of producing a coil component according to claim 18, wherein a length of the ring connecting section formed at one end section of the arc-shaped portion of the ring section is greater than a length of the ring connecting section formed at the other end section.
29. The method of producing a coil component according to claim 18, wherein the package member has an outside shape of a prism, each ring connecting section is disposed at a corner portion of the package member, and each terminal is disposed between the corner portions of the package member.
30. The method of producing a coil component according to claim 18, wherein the plurality of ring sections formed of a metallic flat plate disposed in a plane are formed by etching or die-cutting.
31. The method of producing a coil component according to claim 18, wherein the package member forming step comprises:
mixing a binder including thermosetting resin and magnetic powder in a non-heated state so that the thermosetting resin does not set completely, and pressure forming the mixed binder to provide two compacted powder bodies; and
forming each compacted powder body to include a low hardness portion having such a hardness that the compacted powder body loses its shape, re-pressure forming each compacted power body to cover the coil sections, and heating the re-pressure formed compacted powder body so that the thermosetting resin is completely set, thereby to form the package member.
32. The method of producing a coil component according to claim 18, wherein in the re-pressure forming, each compacted powder body is formed to include a high hardness portion having such a hardness that the compacted powder body does not lose its shape and a low hardness portion having such a hardness that the compacted powder body loses its shape, and in forming the package member, the high hardness portion of the compacted powder body supports one face of the coil.
33. The method of producing a coil component according to claim 18, wherein the package member forming step comprises setting a thickness of a skin encapsulating the coil section to be smaller than a diameter of the through hole of the coil section, and setting a density of an upper face portion of the package member corresponding to an upper portion of the coil section and a density of a lower face portion of the package member corresponding to a lower portion of the coil section at higher values than that of a density of an intermediate portion of the package member corresponding to a height portion of the coil section.