JP2007074597A - Rf transponder for air-core coil and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an air-core coil type transponder having an accurate resonant frequency. <P>SOLUTION: An RF air-core coil type transponder includes a rotatable carrier like a hard reel (12). A coil (14) is wound around the reel (12), and a body (16) which is located inside the coil and operates upon at least one of electric and magnetic fields, is supported by the reel (12). Since the reel (12) is hard, the coil (14) can keep its shape and in particular, when a wire winding machine forms the coil (14), an accurate distance between winding wires can be guaranteed. Adjusting the angular position, shape, component, dimension and/or surface area of the body (16) is effective for adjusting a resonant frequency. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an RF transponder, and more particularly to an RF air-core coil transponder and a method of manufacturing the same.

  In an RF frequency identification system, the transponder resonant frequency is one of the most important factors in the transponder reading performance. If the resonant frequency of the transponder is accurate, it will contribute to quality assurance of the electrical function of the product.

  Often, transponders with varying reading performance are found, but this variation is often due to variations in resonant frequency. This may depend on the technology used. For example, air-core coil technology is typically used for low frequency transponders such as 125 kHz transponders and mid-frequency transponders such as 13.56 MHz transponders.

  In general, when manufacturing an air-core coil transponder, the air-core coil is typically made from a self-welding conventional single wire insulated wire. When a self-welding electric wire is used, the coil becomes hard and it becomes difficult to bend as the number of turns increases. On the other hand, if the number of turns of the electric wire is as small as about 1 to 50, the coil is flexible and can be bent easily. If the coil is deformed, the coil impedance changes.

  In addition, the coil is associated with inductance, resistance, and parasitic capacitance. If the distance between the windings of the wire and the winding process varies from transponder to transponder, the internal parasitic capacitance will also vary, resulting in a change in coil impedance at each transponder. This leads to a difference in resonance frequency.

  In order to adjust the resonant frequency of the transponder, it has been found that the capacitance and / or inductance of the resonant circuit of the transponder can be changed.

  A resonant circuit with a very high Q factor (quality factor) is particularly effective for extracting high energy from the reader and retransmitting energy to the reader, especially in longer reading ranges. On the other hand, a circuit with a high Q value cannot have a wide resonance frequency. This is because, when the frequency is different, the coupling of energy from the reader to the transponder changes greatly, and the energy transmitted from the transponder to the reader decreases. This not only reduces the maximum reading distance, but also causes variations in the maximum reading distance between transponders.

  For this reason, a more accurate resonant frequency is required for a high Q resonant circuit to increase the read distance and minimize the difference between transponders.

  In addition to the problem that the resonant frequency cannot be controlled due to variations caused by differences between the transponder coils, there are also problems that arise as a result of variations in the associated electronic components. That is, for example, the capacitor included in the adopted IC (integrated circuit) affects the resonance frequency, and also causes a variation in tolerance between the capacitor ICs, thereby causing a variation in the resonance frequency of the transponder.

  Variations caused by variations in coil electrical parameters and / or electrical component tolerances require an effective way of adjusting the resonant frequency before, during or after manufacture.

  One object of the present invention is to provide an RF air core coil with accurate impedance and to provide a method of manufacturing it.

  It is a further object of the present invention to provide a method for adjusting the resonant frequency of an RF air coiled transponder during and / or after manufacture of the transponder.

  According to one aspect of the present invention, a hard carrier such as a hard reel can be used to reduce the impedance tolerance of the air core coil. A stiff carrier allows for uniform winding of the coil.

  According to another aspect of the invention, a body is provided that includes a material that acts on a magnetic and / or electric field. The shape, dimensions, components, and position of this body can be adjusted to change the inductance and internal parasitic capacitance of the coil, thereby adjusting the resonant frequency of the transponder resonant circuit.

  Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings.

  Referring now to the drawings, and particularly to FIGS. 1 and 2, a rotatable in the form of a case 11 and a rigid reel 12 containing a suitable electrically insulating material, for example a plastic such as PPS, installed in the case 11. An RF air core transponder 10 with a simple carrier is shown. Like the reel 12, the case 11 can also include a plastic such as PPS. As an advantageous method, the hardness required for the reel 12 can be achieved by making the reel 12 solid. The coil 14 is wound around the reel 12. At least one body 16, which may be an electric field or a magnetic field but acting on the field, is installed inside the coil 14 on the reel 12. In this embodiment, the body 16 is cylindrical, but the body 16 may be of any shape and can include any suitable material that acts on the field, such as magnetic metal or ferrite. Aluminum has been found to be an effective material. Furthermore, although only one body 16 is shown, one or more bodies 16 acting on the field can be mounted on the reel 12 in practicing the present invention. Another body 17 acting on the field is fixed to the lower half 11 a of the case 11. As with the body 16, the body 17 can be any shape and can include any suitable material, such as aluminum. An IC (integrated circuit) 18 including electrical components of the transponder 10 is fixed to the reel 12.

  Referring to FIG. 3, an equivalent circuit 20 of the coil 14 is shown. The equivalent circuit 20 includes an inductor 22 that represents the inductance of the coil 14, a resistor 24 that represents the internal resistance of the coil 14, and capacitors 26 and 28 that represent the internal parasitic capacitance of the coil 14. The inductor 22, the resistor 24, and the capacitors 26 and 28 constitute the impedance of the coil 14.

  The resonant frequency of coil 14 is a function of the individual values of inductor 22 and capacitors 26 and 28, among others. These values are then a function of, inter alia, the distance between the windings of the coil 14 and the shape of the coil 14 as is well known. Therefore, if the distance between the windings of the coil 14 of each transponder 10 is the same and the coil shape is the same, the values of the inductor 22 and the capacitors 26 and 28 of the coil 14 of each transponder are essentially the same, and the resonance frequency. Will be the same. Unfortunately, prior art transponder designs and their manufacture have not provided uniform values. However, the present invention achieves such a uniform value.

  That is, if the reel 12 is hard, especially when the winding machine forms a coil, the coil 14 can keep its shape and ensure an accurate distance between the windings. This in turn keeps the values of inductance and parasitic capacitance constant, which in turn leads to a constant resonance frequency.

  As mentioned above, the bodies 16 and 17 act on magnetic and / or electric fields and thus affect the overall impedance and resonant frequency of the coil 14.

  The ability of the bodies 16 and 17 to act on the magnetic and electric fields not only depends on the type of material constituting the bodies 16 and 17 and their shape, in particular their surface area, but also the angle of the body 16 as described above. It also depends on the position.

  In accordance with the present invention, the shapes and components of bodies 16 and 17 are selected to achieve the desired resonant frequency. The resonant frequency of the transponder 10 is then tested with suitable test equipment 30 as shown in FIG. If the test results indicate that the transponder 10 under test does not have the desired resonance frequency, the angular position of the body 16 is changed by rotating the carrier.

  Referring to FIGS. 5a-5d, several angular positions of the body 16 are shown. Changing the angle of the body 16 changes the impedance of the resonance circuit 20 and, as a result, changes the resonance frequency of the transponder 10. Specifically, by changing the position of the body 16 with respect to the body 17, the connection surface area of the bodies 16 and 17 changes. When the connection surface area changes, the impedance of the coil 14 changes. More specifically, the impedance increases as the connection surface area increases. That is, the connecting surface area of the bodies 16 and 17 in FIG. 5b is wider than in FIG. 5a. As a result, the resonant circuit of the transponder 10 of FIG. 5b has a higher impedance than the resonant circuit 20 of the transponder 10 of FIG. 5a and thus has a lower resonant frequency. Similarly, the resonant circuit 20 of the transponder 10 of FIG. 5c has a higher impedance than the transponder 10 of FIG. 5b and thus has a lower resonant frequency. The position of the body 16 shown in FIG. 5d gives the maximum coupling surface area, so that the resonant circuit 20 of FIG. 5d will have a higher impedance than the resonant circuit of FIGS. It will have a resonant frequency. In this way, by rotating the position of the body 16 clockwise, the resonance frequency of the transponder 10 is reduced compared to the original position.

  Although the invention has been described with reference to specific embodiments thereof, many variations and modifications and other uses will become apparent to those skilled in the art. Accordingly, the invention should be limited only by the following claims and not by the specific disclosure provided herein.

FIG. 3 is a developed view of a transponder with parts omitted for clarity to emphasize certain features of the invention. The top view which shows the cross section of the carrier which comprises some transponders of FIG. FIG. 2 is an equivalent circuit diagram of a coil constituting a part of the transponder of FIG. 1. FIG. 2 is a block diagram illustrating a transponder under test for determining a resonant frequency. a to d are cross-sectional views showing different orientations of transponder carriers corresponding to different resonance frequencies;

Explanation of symbols

10 transponder 11 case 12 carrier (reel)
14 Coil 16, 17 Body 18 Integrated circuit 20 Coil equivalent circuit (resonance circuit)
22 Inductor 24 Resistance 26, 28 Capacitor 30 Test equipment

Claims (32)

RF transponder (10),
A rotatable carrier (12);
A coil (14) wound around the carrier (12);
At least one body (16) acting on a field supported by the carrier (12) inside the coil (14), the angular position, shape, component, dimension and / or of the body (16) The RF transponder (10) including a body (16) having a surface area that affects a resonant frequency of the transponder (10).   The RF transponder according to claim 1, wherein the angular position of the body (16) affects the resonant frequency of the transponder (10).   The RF transponder according to claim 1, wherein the shape of the body (16) affects the resonance frequency of the transponder (10).   2. The RF transponder according to claim 1, wherein a component of the body (16) influences a resonance frequency of the transponder (10).   The RF transponder according to claim 1, wherein the size of the body (16) affects the resonant frequency of the transponder (10).   The RF transponder according to claim 1, wherein the surface area of the body (16) affects the resonant frequency of the transponder (10).   The RF transponder according to claim 1, comprising an electrical component (18) supported by the carrier.   8. The RF transponder according to claim 7, wherein the electrical component is an integrated circuit (18).   5. The RF transponder according to claim 4, wherein the body (16) includes a magnetic material.   The RF transponder according to claim 9, wherein the magnetic material is aluminum. RF transponder (10),
Case (11),
A carrier (12) installed inside the case (11) and rotatable relative to the case;
A coil (14) wound around the carrier;
At least one first body (16) acting on a field supported by the carrier (12) inside the coil (14);
At least one second body (17) acting on the field, fixed to the case (11);
An RF transponder comprising:   12. The RF transponder according to claim 11, comprising an electrical component (18) supported by a carrier (12).   13. The RF transponder according to claim 12, wherein the electrical component is an integrated circuit (18).   12. The RF transponder (10) according to claim 11, wherein the first and second bodies (16, 17) comprise a magnetic material.   12. The RF transponder (10) according to claim 11, wherein each of the first and second bodies (16, 17) comprises aluminum. An RF transponder,
Case (11),
A coil (14) installed inside the case (11);
At least one movable body (16) inside the coil (14) and acting on the field;
At least one fixed body (17) acting on the field, fixed to the coil;
An RF transponder comprising: A method of manufacturing an RF transponder (10) comprising:
Providing a hard and rotatable carrier (12);
Winding a coil (14) around the carrier (12);
Including said method.   18. A method according to claim 17, wherein the carrier is a reel (12). A method of manufacturing an RF transponder (10) comprising:
Providing a rotatable carrier (12);
Winding a coil (14) around the carrier (12);
Providing at least one body acting on the field (16) supported by the carrier (12) inside the coil (14), the angular position, shape, component, dimensions of the body (16) , And / or the surface area affects the resonant frequency of the transponder (10);
Including said method.   20. The method according to claim 19, wherein the angular position of the body (16) affects the resonant frequency of the transponder (10).   20. A method according to claim 19, wherein the shape of the body (16) affects the resonant frequency of the transponder (10).   20. A method according to claim 19, wherein a component of the body (16) affects the resonant frequency of the transponder (10).   20. A method according to claim 19, wherein the dimensions of the body (16) influence the resonant frequency of the transponder (10).   20. A method according to claim 19, wherein the surface area of the body (16) affects the resonant frequency of the transponder (10).   20. A method according to claim 19, comprising connecting an electrical component (18) to the carrier.   26. The method according to claim 25, wherein the electrical component (18) is an integrated circuit (18).   20. A method according to claim 19, wherein the body (16) comprises a magnetic material.   28. The method of claim 27, wherein the magnetic material is aluminum. A method for adjusting a resonance frequency of an RF transponder (10) to a desired value, wherein the RF transponder includes a rotatable carrier (12) and a coil (14) wound around the carrier (12). And at least one body (16) acting on the field supported by the carrier (12), the method comprising:
Measuring the resonant frequency of the transponder (10);
Adjusting the angular position of the body (16) so that the transponder (10) has a desired resonance frequency when the resonance frequency is not a desired value;
Including said method.   30. The method according to claim 29, wherein the carrier (12) is rotatable and the angular position of the body (16) can be changed by rotating the carrier (12). A method for adjusting a resonance frequency of an RF transponder (10) to a desired value, wherein the RF transponder (10) includes a case (11), a coil (14) installed in the case (11), At least one movable body (16) acting on the field and acting on the field, and at least one body (17) acting on the field fixed to the coil (14), The method is
Measuring the resonant frequency of the transponder (10);
Changing the position of at least one movable body (16) acting on a field when the resonant frequency is not a desired value so that the transponder (10) has a desired resonant frequency;
Including said method.   26. The method of claim 25, wherein the at least one movable body (16) is mounted on the rotatable carrier (12) and the at least one movable body (16). The method of claim 1, wherein the position of is changed by rotating the carrier (12).