JP2001060818A - Antenna circuit constant calculation method and storage medium recorded with antenna circuit constant calculation program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an antenna circuit constant calculation method capable of calculating mutual inductance between a plurality of antennas and the self- inductance of each antenna even when the winding number of a coil is large in a short time and performing highly accurate calculation even when distance between a plurality of antennas is large, and also provide a storage medium on which an antenna circuit constant calculation program is recorded. SOLUTION: In this method for calculating the self-inductance or mutual inductance of an antenna circuit capable of being connected by electromagnetic induction whose shape and magnitude are preliminarily decided, a set of line segments with which the layout of an antenna circuit is subjected to broken line approximation is obtained from the shape of a decided antenna circuit, and the element inductance of each line segment is obtained from a preliminarily prepared algebraic analysis expression on the basis of the mutually positional relation of a plurality of calculated line segments, then the self-inductance or mutual inductance of the antenna circuit is calculated on the basis of the element inductance of each line segment approximating the antenna circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention records an antenna circuit constant calculation method and an antenna circuit constant calculation program which can be used for designing an antenna used for a wireless tag, a non-contact IC card, an IC card reader, and the like. It relates to a recording medium.

[0002]

2. Description of the Related Art For example, a wireless tag or a non-contact IC card has a built-in antenna for wireless communication. In this type of wireless device, a relatively low frequency of about 1 GHz or less is often used as a carrier. Also,
In the case of a non-contact IC card, optimization of the antenna circuit is an important theme because it is necessary to simultaneously perform non-contact power supply and signal transmission and reception by electromagnetic induction using the antenna circuit.

That is, antennas provided in both a non-contact IC card and an IC card reader / writer for reading and writing data from and to the IC card are determined according to the distance and arrangement between the two antennas and the shape of each antenna. 2
Mutual inductance between two antennas and self-inductance of each antenna greatly change. Therefore, the shape and arrangement of the antenna have a great effect on power supply and signal transmission / reception by electromagnetic induction, and operability of the IC card,
That is, usable conditions such as the distance to the IC card reader / writer and the arrangement state are determined.

[0004] Therefore, when designing a system using a non-contact IC card or the like, it is required that the mutual inductance of the antennas facing each other and the self-inductance of each antenna be examined in advance by simulation. When the inductance of such an antenna coil is simulated by a computer, a general-purpose electromagnetic field simulator can be used. That is, 3
A three-dimensional antenna circuit structure object is divided into small solids in a finite element manner, and an electromagnetic field over all elements of many small solids is obtained as a large-scale matrix problem.

[0005]

However, when a general-purpose electromagnetic field simulator is used, if the shape of the object becomes complicated, the number of elements increases, so that it is inevitable that the time required for calculation becomes enormous. In practice, it takes about 30 minutes to calculate, for example, for a single-turn antenna coil, and when the number of turns is 5, typically 3 minutes.
It takes more than time, and when the number of turns is 10, practical simulation is difficult from the viewpoint of calculation time and calculation scale.

Therefore, it is not efficient to optimize the design of an antenna coil using a general-purpose electromagnetic field simulator, and it has been impossible to perform calculations depending on the shape of the coil.
In addition, since the result obtained by such an electromagnetic field simulation is a scattering coefficient (S parameter), in order to obtain the inductance, the result of the electromagnetic field simulation is further applied to a coil model coupled by electromagnetic induction and recalculated. Needed. Further, when the distance between the antennas is larger than the size of the antenna, there is a disadvantage that a calculation error increases.

For example, in a wireless device such as a non-contact IC card or a wireless tag, the number of turns of an antenna coil is usually about 5 or more. In the case of the proximity type, which is under discussion of standardization by the ISO committee, the distance between the antenna coils may be about 70 cm. Considering these, it is not appropriate to use the conventional electromagnetic field simulator for designing an antenna for a non-contact IC.

According to the present invention, the mutual inductance between a plurality of antennas and the self-inductance of each antenna can be calculated in a short time even when the number of turns of the antenna coil is large, and the calculation can be performed with high accuracy even when the distance between the plurality of antennas is large. It is an object of the present invention to provide a method for calculating an antenna circuit constant and a recording medium on which an antenna circuit constant calculation program is recorded.

[0009]

SUMMARY OF THE INVENTION An antenna coil used as an antenna circuit in a wireless device such as a non-contact IC card or a wireless tag is generally formed of a wiring which is sufficiently thin compared to the size of its external shape. . Therefore, in the present invention, this antenna coil is treated as a line having no cross section.

For example, if the two antenna coils 20 and 30 shown in FIG. 3 are regarded as an antenna circuit composed of a line having no cross section, the mutual inductance Mab between the antenna coils 20 and 30 is calculated from the following Neumann's formula. It can be expressed by equation (1).

(Equation 1) Here, Ca: an integration path along the shape of the antenna coil 20 Cb: an integration path along the shape of the antenna coil 30 ds (i): a minute line segment vector constituting a part of the antenna coil 20 ds (j): an antenna coil A minute line segment vector constituting a part of 30: d: distance between ds (i) and ds (j) Equation (1) can be applied to antenna coils of various shapes. Moreover, since the numerical calculation is performed for the double integral of the scalar quantity, the calculation can be performed at a higher speed than when a conventional general-purpose electromagnetic field simulator is used.

By the way, the integration paths Ca,
Even if Cb is divided into a plurality of elements, the respective inductances between the elements are obtained, and the results are combined, the self inductance and the mutual inductance of the entire antenna coil can be obtained. If all the divided elements are only linear line elements, the element inductances between the respective line elements can be calculated algebraically from their relative positions. Further, by calculating the sum of the plurality of obtained element inductances, the self inductance and the mutual inductance of the entire antenna coil can be obtained. That is, since the self-inductance and the mutual inductance can be obtained analytically without performing the numerical integration as in the equation (1), the calculation can be further speeded up.

For example, the antenna coils 20 and 30 shown in FIG.
In the case of, the element can be divided into a plurality of elements at division positions as shown in FIG. However, only the division at each division position shown in FIG. 4 includes a curved part in each element. Therefore, in the present invention, as shown in FIG. 5, an element including a curved portion is approximated by a polygonal line and is represented by a plurality of line segment elements. In the example of FIG.
The antenna coil 20 has p segment elements dS (1) to dS (p).
And the antenna coil 30 is composed of q line segment elements dS
It is divided into (p + 1) to dS (p + q).

In this case, each divided line segment element dS
When the element inductance between (i) and dS (j) is represented by m (i, j), the mutual inductance Mab between the antenna coils 20 and 30 is represented by the following equation (2). It is obtained as the sum of m (i, j).

(Equation 2) Here, Ci: an integration path along the shape of each line element dS (i) Cj: an integration path along the shape of each line element dS (j) dx: a minute line constituting a part of the line element dS (i) Segment vector dy: A minute line segment vector constituting a part of the line segment element dS (j) When the self-inductance La of the antenna coil 20 is obtained, the antenna coil for obtaining the two integration paths in the equation (1) is used. What is necessary is just to make it equal to a shape. That is,
In equation (2), i and j may be determined as one element of the same one antenna coil for obtaining the self-inductance. For example, the self-inductance La is expressed by the following equation (4).

(Equation 3) Here, the element inductance for all combinations between all the line segment elements dS (1) to dS (p + q) is expressed by the following (5)
It can be represented in a matrix format as in an equation.

(Equation 4) In addition, the sum of the elements of the partial matrix of the four regions separated by the dotted line in the expression (5) is La in the following expression (6).
a, Lbb, Mab, Mba, the equation (5) is
It can be expressed by equation (7).

(Equation 5) Here, Laa: the self-inductance of the antenna coil 20 (Laa
= La) Lbb: self-inductance of the antenna coil 30 Mba: mutual inductance (Mba = Mab) Accordingly, each element inductance m (i, j) shown in the matrix of the expression (5) is calculated, and the expression (6) is obtained. By combining the element inductances m (i, j) as described above, the self-inductance and the mutual inductance can be calculated simultaneously. Since the mutual inductance Mba is equal to Mab, only one of Mab and Mba needs to be calculated in the actual calculation.

Although the case has been described here where the self-inductance and the mutual inductance of the two antenna coils are obtained at the same time, only the self-inductance of one antenna coil may be calculated. Assuming the case of a non-contact IC card and an antenna circuit used for the reader / writer, there is a possibility that a plurality of non-contact IC cards are simultaneously inserted into the electromagnetic field generated by the reader / writer. There is also. In such cases, the mutual inductance between the reader / writer and the non-contact IC
C force will have an effect. However, the influence is usually negligible as compared with the mutual inductance value and the self-inductance value of the two antenna coils of interest.

Further, even when there are three or more antenna coils, the calculation can be performed in the same manner as described above. That is, all combinations of the antenna coils to be calculated may be calculated.

For example, three antenna coils (a, b,
c), all the element inductances m (i, j) associated with the combination of each line element of the antenna coil (a), each line element of the antenna coil (b), and each line element of the antenna coil (c). ) Can be obtained and can be represented by the same matrix as in the above-mentioned formula (5). This matrix can be expressed by the following equation (8).

(Equation 6) Where, Laa: self-inductance of antenna coil (a) Lbb: self-inductance of antenna coil (b) Lcc: self-inductance of antenna coil (c) Mab, Mba: mutual inductance between antenna coils (a, b) Mac, Mca : Mutual inductance between antenna coils (a, c) Mbc, Mcb: Mutual inductance between antenna coils (b, c) As described above, in the present invention, a polygonal line approximation is performed. DS (1) to dS (p + q) shown in FIG.
It becomes a straight line like Therefore, each element inductance m can be obtained by algebraic analysis from the relative position between the element lines.

However, the calculation of the element inductance (element self-inductance) m between the same line segment elements that becomes (i = j) in the equation (3) cannot be performed because the integration result is diverged. Therefore, in the case of (i = j), the cross section of the wire constituting the antenna coil has a circular or rectangular shape with a certain size,
The element inductance m can be obtained as follows by assuming that the current is distributed uniformly in the cross section or the surface.

For example, assuming that the cross-sectional shape of the antenna coil is a circle having a radius r and the current distribution is assumed to be uniform in cross-section, if the length of each line segment element is represented by k, the element inductance when i = j m can be obtained from the following equation (9).

The cross-sectional shape of the antenna coil is defined by a radius r.
Assuming that the current distribution is uniform on the surface,
The element inductance m when i = j can be obtained from the following equation (10). Further, assuming that the cross-sectional shape of the antenna coil is a rectangle having a width w and a height h, and assuming that the current distribution is uniform, the element inductance m at the time of i = j is obtained from the following equation (11). be able to.

(Equation 7) In the case other than (i = j), the element inductance m of Expression (3) is a set of line segment elements dS (i) and dS of interest.
It is uniquely determined according to the relative position of (j). here,
As a specific example, a method of calculating the element inductance m in the general arrangement shown in FIG. 7 will be described. In the example of FIG. 7, the line segment element dS (i) is located on the plane X1, and the line segment element dS (j) is located on the plane X2. The two planes X1 and X2 are parallel to each other. Plane X
The distance between 1 and X2 is d. Further, the line segment element dS
(i) and dS (j) are oriented differently so as to be twisted with each other. The coordinates of the end points of the line element dS (i) are Pa1 and Pb1, and the coordinates of the end points of the line element dS (j) are Pa2 and Pb2.

The lengths of the line segment elements dS (i) and dS (j) are k1 and k2, respectively. In order to define the direction of integration, the direction from the end point Pa1 to the end point Pb1 and the direction from the end point Pa2 to the end point Pb2 are defined as positive directions. Here, let the coordinates Pa2 'and Pb2' be the coordinates obtained by projecting the coordinates Pa2 and Pb2 of the end point of the line segment element dS (j) on the plane X2 onto the plane X1. Therefore, the angle θ formed by the extension line between the line segment element dS (i) and the line connecting the coordinates Pa2 ′ and Pb2 ′ is
It is equal to the angle formed by the extension of the line segment elements dS (i) and dS (j).

In FIG. 7, a line segment element dS (i) and coordinates Pa2 ',
The point where the extension line intersects with the line segment connecting Pb2 'is represented by P01, and the point obtained by projecting this point P01 on the plane X2 is represented by P02. The distance between the point P01 and the end point Pa1 is indicated by α, and the distance between the point P02 and the end point Pa2 is indicated by β.

As shown in FIG. 8, the distances between the end points of the line segment elements dS (i) and dS (j) are R1, R2, R3, R
Represented by 4. The distance between the end points Pb1, Pb2 is R1, and the end points Pb1, Pb1,
The distance between Pa2 is R2, the distance between end points Pa1 and Pa2 is R3,
The distance between the end points Pa1 and Pb2 is R4. Under the conditions shown in FIGS. 7 and 8, the element inductance m of the line segment elements dS (i) and dS (j) is expressed by the following equation (12).

(Equation 8) Therefore, a first aspect of the present invention is to calculate an antenna circuit constant for calculating at least one of a self-inductance of one antenna circuit and a mutual inductance of a plurality of antenna circuits which are preliminarily determined in shape and size and can be coupled by electromagnetic induction. A method for determining a set of line segments that approximates the layout of the antenna circuit in a polygonal line from the determined shape of the antenna circuit, based on the obtained relative positional relationship of the plurality of line segments, from an algebraic analysis formula prepared in advance. Determining an element inductance of each line segment, and calculating at least one of a self-inductance of one antenna circuit and a mutual inductance of the plurality of antenna circuits based on the element inductances of the plurality of line segments approximating the antenna circuit. I do.

According to the first aspect, since the mutual inductance of the plurality of antenna circuits and the self-inductance of each antenna circuit can be calculated by an algebraic analysis formula as described above, a conventional general-purpose electromagnetic field simulator is used. The calculation result can be obtained in a shorter time than in the case. According to a second aspect of the present invention, in the method of calculating an antenna circuit constant according to the first aspect, a plurality of types of algebraic analysis expressions are prepared in advance as a function table, and the determined relative arrangement pattern of the plurality of line segment elements is prepared. The type is identified, one algebraic analysis formula is selected from the function table based on the identified arrangement pattern, and the element inductance of each line is obtained using the selected algebraic analysis formula.

Even when the relative position between the line segment elements changes variously, the element inductance m can be obtained by calculating using the above-mentioned equation (12). However, when the relative position between the line segment elements satisfies special conditions, a part or all of the calculation terms in the equation (12) are deleted, so that the calculation can be simplified.

According to the second aspect, one algebraic analysis formula is selected from a function table prepared in advance according to the type of the relative arrangement pattern of a plurality of line segments and is used for calculation. It can be further shortened. Claim 3 is a recording medium that records an antenna circuit constant calculation program for calculating at least one of a self-inductance of one antenna circuit and a mutual inductance of a plurality of antenna circuits that can be coupled by electromagnetic induction by a computer, An input procedure for inputting at least information on the shape and size of the antenna circuit determined in advance, a polygonal line approximation procedure for obtaining a set of line segments that approximate the layout from the input antenna circuit shape, Based on the relative positional relationship between the plurality of line segments, an element inductance calculation procedure for obtaining the element inductance of each line segment from an algebraic analysis formula prepared in advance, and an antenna based on the element inductance of the plurality of line segments approximating the antenna circuit. Circuit self-inductance and the mutual Characterized by providing a matrix calculation procedure for calculating at least one of the inductance.

By executing the program recorded on the recording medium of the third aspect by a predetermined computer, the method of calculating the antenna circuit constant of the first aspect can be implemented. Claim 4 is a recording medium storing an antenna circuit constant calculation program for calculating at least one of a self-inductance of one antenna circuit and a mutual inductance of a plurality of antenna circuits that can be coupled by electromagnetic induction, An input procedure for inputting information on a plurality of line segments that approximates the layout of each antenna circuit in a polygonal line based on at least a predetermined shape of the antenna circuit, based on a relative positional relationship of the input line segments, Based on the element inductance calculation procedure for obtaining the element inductance of each line from the algebraic analysis formula prepared in advance, and the self inductance of the antenna circuit and the mutual inductance of the plurality of antenna circuits based on the element inductance of the plurality of lines approximating the antenna circuit. Matrix for calculating at least one of Characterized by providing a procedure.

By executing the program recorded on the recording medium according to the fourth aspect on a predetermined computer, the method for calculating the antenna circuit constant according to the first aspect can be implemented. According to a fifth aspect of the present invention, in the recording medium storing the antenna circuit constant calculation program according to the third or fourth aspect, fixed data of a function table including a plurality of types of algebraic analysis formulas and relative values of a plurality of selected line segments are provided. An arrangement pattern identification procedure for identifying a type of the arrangement pattern; and an algebraic analysis equation selection procedure for selecting one algebraic analysis equation from the function table based on the arrangement pattern identified by the arrangement pattern identification procedure, It is characterized in that the element inductance of each line is obtained using the algebraic analysis formula selected by the algebraic analysis formula selection procedure.

By executing the program recorded on the recording medium according to the fifth aspect on a predetermined computer, the method for calculating the antenna circuit constant according to the second aspect can be implemented.

[0029]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) One embodiment of a method for calculating antenna circuit constants and a recording medium on which an antenna circuit constant calculation program is recorded according to the present invention will be described with reference to FIG. I do. This form is defined in claims 1 to
This corresponds to claims 3 and 5.

FIG. 1 is a flowchart showing the contents of the processing of the program of this embodiment. In this embodiment, claim 3
The input procedure, the polygonal line approximation procedure, the element inductance calculation procedure, and the matrix calculation procedure are respectively performed in step S1.
0, S11, S15 and S17. Further, the fixed data, the arrangement pattern identification procedure and the algebraic analysis expression selection procedure of claim 5 correspond to the function table 10, the step S
13 and S14.

The processing in FIG. 1 can be executed using a general-purpose personal computer or workstation. The program and data for the processing shown in FIG. 1 can be recorded on a recording medium such as a CD-ROM and distributed. That C
By reading the program and data from the D-ROM into a personal computer or a workstation, the processing in FIG. 1 can be executed using various computers.

Function table 1 included in this program
In 0, a plurality of algebraic analysis expressions are held as fixed data. Specifically, the formula (12) and the following formula (13)
Expressions to (18) are held in the function table 10.

(Equation 9) The contents of each step shown in FIG. 1 will be described below. In the first step S10, information on the shape and size of each of the two antennas to be calculated and the relative positions of the two antennas are input.

Actually, by using an input support tool such as CAD, the shape and size of each antenna and the relative position of two antennas can be determined in advance by a relatively simple operator operation. Information such as numerical values determined by the processing is input to this program in step S10. In the case of a planar antenna, image data representing an antenna shape pattern may be input instead of a numerical value or the like, and the antenna shape may be read from this image data.

In step S11, the division position is determined based on the shape of each antenna input in step S10, and the broken line approximation of the antenna pattern is performed. For example, when the antenna coils 20 and 30 having the shapes shown in FIG. 3 are to be calculated, the positions close to the corners of the rectangle (boundary with the curved portion) are determined as the division positions as shown in FIG. Then, as shown in FIG. 5, the curved parts of the divided elements are replaced with straight lines, and the line segment elements dS (1) to dS
Determine (p + q).

In the case of calculation for a spiral antenna, for example, a region on the antenna can be divided as shown in FIG. 20, and line segment elements can be determined by polygonal line approximation. The procedure of the division in FIG. 20 is as follows. The area of the upper half circumference from the start point of the innermost circumference of the antenna is divided at every fixed angle (15 degrees in this example) around the center point Oa. In addition, the lower half of the area is divided at a fixed angle (15 degrees in this example) with the point Ob shifted from the center point Oa by half the pitch δ as a new center.

By repeating the above processing, all the regions of the spiral can be divided. Each area divided in this manner is replaced with a line segment from a curve. In step S12 of FIG. 1, a set of line segment elements dS (1) to dS (p +
A set of line segment elements dS (i) and dS (j) is selected from q).

In step S13, the relative positional relationship between the set of line segment elements dS (i) and dS (j) selected in step S12 is identified. Specifically, it is determined whether or not any of the conditions shown in FIGS. 9 to 17 is satisfied. In the example of FIG. 9, two line segment elements dS (i) and dS (j) are arranged on the same plane. In the example of FIG. 10, two line segment elements dS (i), d
S (j) are arranged in parallel. In the example of FIG. 11, two line segment elements dS (i) and dS (j) are arranged perpendicular to each other. In the examples of FIGS. 12 and 13, the two line segment elements dS (i) and dS (j) are arranged such that the coordinates of one start point and the other end point coincide with each other.

Further, in the example of FIG. 14, two line segment elements d
S (i) and dS (j) are arranged such that the coordinates of the starting point coincide, and in the example of FIG. 15, they are arranged such that the coordinates of the ending points of the two line segment elements dS (i) and dS (j) coincide. Have been. In the examples of FIGS. 16 and 17, two line segment elements dS (i), dS (i)
S (j) is arranged on the extension of the same straight line.

In step S14 of FIG. 1, step S1
One algebraic analysis expression associated with the identification result of No. 3 is selected from the function table 10 and input. The conditions shown in FIGS. 9 to 17 and the algebraic analysis expressions of Expressions (13) to (18) are associated in advance as follows. FIG. 9 (on the same plane): Equation (13) FIG. 10 (parallel): Equation (14) FIG. 11 (vertical): Equation (15) FIG. 12 (start point and end point coincide): Equation (16) FIG. 13 (start point and end point coincide): Equation (16) FIG. 14 (two start points coincide): Equation (17) FIG. 15 (two end points coincide): Equation (17) FIG. (On the line): Expression (18) FIG. 17 (on the same straight line): Expression (18) In the case where none of the conditions in FIGS. 9 to 17 is satisfied, the expression (12) is selected. .

In step S15 of FIG. 1, step S1
Using one algebraic analysis formula selected in step 4, one element inductance m of the above formula (3) is calculated. As described above, in the case of (i = j), the calculation of the element inductance m is exceptionally performed by using any one of the expressions (9) to (11). Steps S12 to S15 are (i = 1 to p +
The processing is executed for all combinations of (q, j = 1 to p + q). When the element inductance m is obtained for all combinations, steps S16 to S1
Go to 7. At this point, all the element inductances m included in the matrix of the above formula (5) are complete.

In step S18, the calculation of each partial matrix of the above formula (5) is performed, and the self-inductance and the mutual inductance of each antenna are calculated. That is,
Calculate Laa, Lbb, Mab (or Mba) shown in equation (6). The result of this calculation is displayed in the next step S18. Note that all the parameters shown in FIGS. 7 to 17 and Expressions (12) to (18) have two line segment elements d.
It can be obtained by calculation based on the coordinate values of both ends of S (i) and dS (j).

(Second Embodiment) Another embodiment of a recording medium storing an antenna circuit constant calculation program and an antenna circuit constant calculation program according to the present invention will be described.
This will be described with reference to FIG. This embodiment corresponds to claims 1, claim 2, claim 4, and claim 5. FIG. 2 is a flowchart showing the contents of the processing of the program of this embodiment. This embodiment is a modification of the first embodiment. FIG.
1 are denoted by the same step numbers as in FIG.

In FIG. 2, step S10 of FIG.
Step S10B is provided instead of S11. That is, in this embodiment, before executing the processing of FIG. 2, a set of line segments approximating the determined antenna shape is generated,
Information of each line segment or information of boundary coordinates between the line segments is input in step S10B. The processing of the broken line approximation for generating a set of line segments may be performed in the same manner as in step S11 of FIG. 1 using another program.

In the calculation method used in the processing shown in FIGS. 1 and 2, only the analytical calculation is performed, so that the processing is relatively simple. In addition, the total calculation amount is smaller than that of a commonly used electromagnetic field simulator. Therefore, a general language and operating system can be used for the computer system construction, and high-speed operation can be expected even when the system is constructed on a computer with low processing capacity. In order to confirm such advantages of the present invention, an experiment described below was performed.

(Experiment 1) As an antenna to be calculated,
Antennas 2 and 3 shown in FIG. 6 were prepared. These antennas 2 and 3 have antenna coils 22 and 32 formed on substrates 21 and 31, respectively. The material of the antenna coil wirings 22, 32 of both the antennas 2, 3 is copper, the thickness is 18 microns, and the line width is 0.5 mm. The wirings 22, 32 were formed on a glass epoxy substrate having a thickness of 1 mm by lithography and wet etching.

Further, the two antennas 2 and 3 were arranged so as to face each other in parallel so that the respective centers of the antenna circuits were aligned, and the inductance was actually measured while changing the distance d between the antenna coils. For this measurement, frequency 1
A 3.56 MHz sine wave was used. Further, the inductances of the antennas 2 and 3 were obtained by calculation using a program for executing the processing shown in FIG. The antenna 3 was approximated by a polygonal line at intervals of 15 degrees as in FIG. For this calculation, EWS (HP-260KE) manufactured by Hewlett-Packard Company is used as the computer hardware, and UNIX (HP-HP) is used as the operating system.
-UX 10.20) was used. In the program of FIG. 1, the kernel is described in C language, and the graphical user interface unit is Tcl / Tk.

The measured and calculated values of the experimental results are shown in FIG.
9. As shown in FIG. 19, the measured value and the calculated value matched with an error of less than 2%. That is, it can be seen that the error caused by the processing such as the broken line approximation adopted in the present invention is small enough to cause no practical problem. Also,
The time required to calculate the inductance in the process of FIG. 1 was 2 seconds. Under the same conditions, when the inductance was calculated using a general-purpose electromagnetic field simulator (em manufactured by Sonnet), it took 30 minutes.
That is, by adopting the present invention, the calculation of the inductance can achieve a speedup of 1000 times.

(Experiment 2) The self-inductance was calculated for the antenna 4 as shown in FIG. 18 using the same hardware and software as in the above Experiment 1. In the antenna 4 shown in FIG. 18, a spiral wiring 42 is formed on a substrate 41. Single antenna 4
Is calculated in step S10 of FIG.
Only information for one antenna was entered. In this example, the number of spiral turns of the antenna 4 is 20. The calculated self-inductance was 3.52822e-4 (H).

(Experiment 3) Using the same hardware and software as in Experiment 1 described above, calculation of mutual inductance was performed when two antennas 4 shown in FIG. 18 were used. In this example, the two antennas 4 face each other in parallel with their centers aligned, and are arranged at intervals of 70 cm. The calculated mutual inductance is 2.442340e-6.
(H).

(Experiment 4) Using the same hardware and software as in Experiment 1, the antenna 2 shown in FIG.
The calculation of the mutual inductance when two were used was performed. In this example, the distance between the centers of the antenna coils of the two antennas 2 is set to 20 mm, and the antenna coils are arranged so as to face each other at an angle of 30 degrees in the long side direction of the antenna coils.
The calculated mutual inductance is 1.01472e-7.
(H).

When calculating the self-inductance and the mutual inductance in the calculation method of the present invention, the conductor is approximately regarded as a linear conductor having a cross-sectional area of zero. It is assumed that the position of the linear conductor is the center position of the cross section of the actual conductor. Further, when calculating the self-inductance, it is assumed that the current distribution is uniform on the surface.

However, in an actual antenna coil, as the frequency increases, the current distribution concentrates on the conductor surface due to the skin effect, and the effect of the parasitic capacitance also increases. Therefore, when an antenna used in a high frequency region is to be calculated, an error may increase. FIG.
1 shows an example of an actually measured value and a calculated value of the impedance-frequency characteristic of the coil. The impedance Z on the vertical axis of the calculated value in FIG. 21 is a result obtained by the following equation from the self-inductance L (L = 3.37586e-7) calculated in the present invention.

Z = 2π · f · L (19) As shown in FIG. 21, the measured value and the calculated value match in the low frequency region, but the value is shifted in the high frequency region. . This difference is because the effect of the parasitic capacitance generated in the high frequency region cannot be calculated by the present invention. In the low frequency region,
Since there is no influence of the parasitic capacitance, the measured value matches the calculated value.

Actually, since the parasitic capacitance value differs depending on the shape and material of the coil, the present invention can be applied to a system using a high frequency of about several GHz, or 200 MHz.
Even at a frequency of about z, the calculation error of the present invention may increase. However, in the case of a layout of an antenna coil used for a non-contact IC chip or the like, the influence of the parasitic capacitance can be neglected in a region of about 500 MHz or less.

Therefore, if the coil used is a relatively low frequency band, such as a non-contact IC power supply or a transformer,
The present invention can be sufficiently applied. In the above description, the calculation is performed only for the antenna coil having a planar shape. However, the shape of the antenna coil to be calculated in the present invention does not necessarily have to be a planar layout. Even in the case of an antenna having a three-dimensional layout, the self-inductance and the mutual inductance can be obtained by using the same calculation method by approximating as a set of line segments in the same manner as described above.

The method of determining the division position when dividing the curved portion of the antenna shape into line segments and the angle at which the circular or spiral area is divided may be changed as necessary.

[0057]

As described above, when the present invention is used, the self-inductance and the mutual inductance of the antenna circuit can be calculated in a short time, which is effective for improving the antenna design efficiency.

In particular, since the antenna coil is approximated to a line segment and calculated by algebraic analysis, even an antenna coil having a large number of turns can be calculated in a short time, and the calculation is difficult in the past. The present invention can be applied to calculation of inductance of various coils such as contact IC force and transformer.

[Brief description of the drawings]

FIG. 1 is a flowchart showing the contents of processing of a program according to a first embodiment.

FIG. 2 is a flowchart illustrating processing of a program according to a second embodiment;

FIG. 3 is a plan view showing an example of an antenna coil shape to be calculated.

FIG. 4 is a plan view showing an example of division of each antenna coil.

FIG. 5 is a plan view showing an example of a line segment element of each antenna coil.

FIG. 6 is a plan view showing an example of an antenna coil shape to be calculated.

FIG. 7 is a perspective view showing an arrangement example (general form) of two line segment elements.

FIG. 8 is a plan view showing an arrangement example of two line segment elements.

FIG. 9 is a perspective view showing an arrangement example (on the same plane) of two line segment elements.

FIG. 10 is a plan view showing an arrangement example (parallel) of two line segment elements.

FIG. 11 is a perspective view showing an arrangement example (vertical) of two line segment elements.

FIG. 12 is a plan view showing an example of the arrangement of two line segment elements (one start point and the other end point coincide).

FIG. 13 is a plan view showing an example of the arrangement of two line segment elements (one starting point and the other end point coincide).

FIG. 14 is a plan view showing an example of the arrangement of two line segment elements (the starting points coincide).

FIG. 15 is a plan view showing an example of arrangement of two line segment elements (end points coincide).

FIG. 16 is a plan view showing an arrangement example (on the same straight line) of two line segment elements.

FIG. 17 is a plan view showing an arrangement example (on the same straight line) of two line segment elements.

FIG. 18 is a plan view showing an example of an antenna coil shape to be calculated.

FIG. 19 is a graph showing measured values and calculated values of experimental results.

FIG. 20 is a plan view showing an example of a polygonal approximation of a spiral antenna.

FIG. 21 is a graph showing examples of measured and calculated values of impedance-frequency characteristics of a coil.

[Explanation of symbols]

 2,3,4 Antenna 10 Function table 20,30 Antenna coil 21,31,41 Substrate 22,32,42 Wiring

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masaaki Tomizawa 2-3-1 Otemachi, Chiyoda-ku, Tokyo Within Nippon Telegraph and Telephone Corporation (72) Inventor Shimichi Shibata 2-chome Otemachi, Chiyoda-ku, Tokyo No. 1 Inside Nippon Telegraph and Telephone Corporation

Claims (5)

[Claims] An antenna circuit constant calculation method for calculating at least one of a self-inductance of one antenna circuit and a mutual inductance of a plurality of antenna circuits, the shape and size of which are predetermined and coupleable by electromagnetic induction, A set of line segments that approximates the layout of the antenna circuit in a polygonal line is obtained from the determined antenna circuit shape, and the element inductance of each line is calculated from an algebraic analysis formula prepared in advance based on the obtained relative positional relationship of the multiple line segments. And calculating at least one of the self-inductance of one antenna circuit and the mutual inductance of the plurality of antenna circuits based on the element inductances of a plurality of line segments approximating the antenna circuit. Method of calculation. 2. The method for calculating antenna circuit constants according to claim 1, wherein a plurality of types of algebraic analysis expressions are prepared in advance as a function table, and the type of the relative arrangement pattern of the determined plurality of line segment elements is determined. Identifying, selecting one algebraic analysis expression from the function table based on the identified arrangement pattern, and obtaining an element inductance of each line using the selected algebraic analysis expression, calculating an antenna circuit constant. Method. 3. A recording medium storing an antenna circuit constant calculation program for calculating at least one of a self-inductance of one antenna circuit and a mutual inductance of a plurality of antenna circuits that can be coupled by electromagnetic induction, using a computer. An input procedure for inputting at least information on the shape and size of the antenna circuit determined in advance, a polygonal line approximation procedure for obtaining a set of line segments for linearly approximating the layout from the input antenna circuit shape, Based on the relative positional relationship of the plurality of line segments, an element inductance calculating procedure for calculating the element inductance of each line segment from an algebraic analysis formula prepared in advance, and an antenna based on the element inductance of the plurality of line segments approximating the antenna circuit. Circuit self-inductance and multiple antenna circuits Each other inductance of the recording medium which records an antenna circuit constant calculation program, characterized by comprising a matrix calculation procedure for calculating at least one. 4. A recording medium storing an antenna circuit constant calculation program for calculating at least one of a self-inductance of one antenna circuit and a mutual inductance of a plurality of antenna circuits that can be coupled by electromagnetic induction, using a computer. Based on an input procedure for inputting information on a plurality of line segments that approximates the layout of each antenna circuit in a polygonal line based on at least a predetermined shape of the antenna circuit, based on a relative positional relationship of the input plurality of line segments, An element inductance calculating procedure for obtaining an element inductance of each line from a previously prepared algebraic analysis formula; Matrix that calculates at least one of A recording medium storing an antenna circuit constant calculation program, characterized by comprising a calculation procedure. 5. A recording medium storing the antenna circuit constant calculation program according to claim 3 or 4, wherein a fixed data of a function table including a plurality of types of algebraic analysis formulas and a relative value of a selected plurality of line segments. An arrangement pattern identification procedure for identifying a type of the arrangement pattern; and an algebraic analysis equation selection procedure for selecting one algebraic analysis equation from the function table based on the arrangement pattern identified by the arrangement pattern identification procedure, A recording medium recording an antenna circuit constant calculation program, wherein an element inductance of each line is obtained using an algebraic analysis formula selected by an algebraic analysis formula selection procedure.