JPH08304493A - Calculation device of intensity of electromagnetic field - Google Patents

Abstract

PURPOSE: To prevent the deterioration of accuracy due to digit dropping in the impedance calculation and to calculate with high accuracy at a high speed in terms of an electromagnetic field intensity calculation device which calculates an electromagnetic field intensity that an electric circuitry device emits by utilizing a moment method. CONSTITUTION: The title device comprises a first calculation operation section 12 that calculates a mutual impedance by using an approximation equation wherein a part of an exponential function is equivalent to a constant in the integration of a monopole and a second calculation operation section 13 that calculates the mutual impedance by using a normal equation. An adopting condition on the basis of an electric length of an element subjected to the calculating of the mutual impedance and an electric length of a distance between the elements is judged by means of a calculation method selection section 11 so that determination is made as to which of the first calculation operation section 12 or second calculation section 13 is selected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic field intensity calculation device for calculating the electromagnetic field intensity radiated by an electric circuit device based on the method of moments, and more particularly to an electromagnetic field intensity calculation device capable of calculating the electromagnetic field intensity at high speed and with high accuracy. And an electromagnetic field strength calculation device.

Radio waves unwantedly radiated from electric circuit devices are
Due to interference with other radio waves such as televisions and radios, it has recently come to be strictly regulated in each country. As a standard of such regulation, in Japan, there is VCCI standard,
There is an FCC standard in the United States and a VDE standard in Germany.

In order to satisfy such radio wave regulations, it is necessary to use various countermeasure techniques such as a shield technique and a filter technique, and it is possible to quantitatively determine how much these countermeasure techniques reduce radio waves. Simulation technology is required. Since such a simulation of electromagnetic wave analysis requires a huge amount of computer processing time, a device for calculating the electromagnetic field intensity radiated by an electric circuit device at high speed and with high accuracy is required.

[0004]

2. Description of the Related Art The strength of an electromagnetic field emitted from an object of an arbitrary shape can be easily calculated by using a known theoretical formula if the current flowing through each part of the object is known. This current value is
Theoretically, it can be obtained by solving Maxwell's electromagnetic wave equations under given boundary conditions, but direct mathematical solutions under complex boundary conditions for arbitrarily shaped objects are currently known. Has not been done.

Therefore, the solutions used to calculate the currents used in the current electromagnetic field strength calculation devices are all approximate, although they are difficult. At present, three representative methods of this approximate solution are known: the minute loop antenna approximation method, the distributed constant line approximation method, and the moment method.

In the small loop antenna approximation method, the wiring connecting the wave source circuit and the load circuit is treated as a loop antenna, and it is assumed that the current on the loop is flat. It is a method of seeking In Figure 9,
The configuration of this small loop antenna approximation method is illustrated.

The calculation by the small loop antenna approximation method is the simplest, but it is rarely used in reality because the accuracy is extremely lowered under the condition that the size of the loop is not negligible compared with the wavelength of the electromagnetic wave.

The distributed constant line approximation method is a method for obtaining the current by applying the equation of the distributed constant line to an object that can be approximated as a one-dimensional structure. The calculation is relatively simple, and the calculation including the phenomena such as line reflection and resonance can be performed only by increasing the calculation time and storage capacity in proportion to the number of analysis elements. For objects, high-speed and high-precision analysis is possible. FIG. 10 illustrates the configuration of this distributed constant line approximation method.

The calculation by the distributed constant line approximation method is 1
For an object that can be approximated as a three-dimensional structure,
Although high-precision analysis is possible, there is a problem that it cannot analyze objects that cannot be approximated.

On the other hand, the method of moments is one of the solutions of the integral equation derived from Maxwell's electromagnetic wave equation, and can handle a three-dimensional arbitrary shape object. Specifically, the current is calculated by dividing the object into smaller elements.

As described above, since the moment method can handle a three-dimensional arbitrarily shaped object, the electromagnetic field strength calculation apparatus
It is effective to use the method of moments to calculate the electromagnetic field intensity radiated by an electric circuit device.

In the method using the moment method, when handling a metal object, the metal part is meshed as an analysis object, the mutual impedance Z _ij between the divided metals is obtained, and the mutual impedance Z _ij and the wave source V _i are calculated. , The current I _i flowing in the divided metal is solved to solve the simultaneous equations [Z _ij ] [I _i ] = [V _i ] of the method of moments to obtain the current I _i, and the electromagnetic field radiated from this result The method of calculating strength is adopted. here,
"[]" Represents a matrix.

In order to realize a high-speed calculation when using such a moment method, in a conventional electromagnetic field strength calculation device, the mutual impedance Z _ij for forming the simultaneous equations of this moment method is usually Calculated by calculation using double precision real numbers.

The following references are available as to the method of moments. [References] HN Wang, JHRichmond and MC Gilreat
h: “Sinusoidal reaction formulation for radiatio
n and scattering from conducting surface ”IEEE TRA
NSACTIONS ANTENNAS PROPAGATION vol.AP-23 1975

[0015]

However, in the method of calculating the double-precision real number, since the lower significant digits are lost during the product operation, the mutual impedance Z _ij is calculated using the method of calculating the double-precision real number. As a result, when the electrical length of the metal mesh (the length on the basis of the wavelength of the radiated electromagnetic wave) becomes short, a digit cancellation occurs, so that the mutual impedance Z _ij cannot be accurately calculated. .

Therefore, the present inventors have filed Japanese Patent Application No. 6-953.
In No. 62, the calculation method of the mutual impedance for calculating the electromagnetic field strength is prepared by the calculation method of the normal calculation and the calculation method of the high precision calculation, and the wavelength, the length of the element and the distance are checked, and the digit If there is a possibility that a drop may occur, we have proposed a method that uses high-precision calculation means.

Here, there are two types of high-precision calculations, that is, a calculation using a multiple-precision real number and a multiple-precision integer calculation. In either case, the number of digits to be calculated increases, so that the calculation time is significantly increased. Will increase.

According to the present invention, in the electromagnetic field strength calculating apparatus by the method of moments, the calculation is performed with a small element (wire or surface patch) having a length of 0.001λ (λ: wavelength) or less and the distance is far. Occurs, the calculation accuracy becomes extremely poor, and if high-precision calculation is performed so that digit cancellation does not occur, the calculation time becomes enormous. It is an object of the present invention to provide an electromagnetic field strength calculation device that can calculate

[0019]

FIG. 1 is a block diagram showing the principle of the present invention. In the figure, 1 is a processing device including a CPU, a memory, and the like, and is a device for calculating the electromagnetic field intensity radiated by an electric circuit device to be analyzed based on the method of moments. The data input unit 10 is an input means for inputting structural information of an electric circuit device to be analyzed.

When calculating the electromagnetic field intensity radiated by the electric circuit device to be analyzed based on the method of moments, the calculation method selection unit 11 calculates the electrical length of the element for which the mutual impedance is to be calculated and the distance between the elements. Is used to select whether to use the first calculation processing unit 12 or the second calculation processing unit 13 for calculating the mutual impedance. For example, the calculation method selection unit 11 selects the first calculation processing unit 12 when the element length of the monopole is approximately 0.05λ (λ is the wavelength) or less and the distance is approximately 10 times the element length or more. In other cases, the second calculation processing unit 13 is selected to calculate the mutual impedance.

When calculating the mutual impedance forming the simultaneous equations of the method of moments, the first calculation processing unit 12 obtains based on the characteristic of the mutual impedance calculation target that the electric length of the element is short and the distance is long. It is a processing means for calculating the mutual impedance based on a predetermined approximate expression of the obtained mutual impedance.

The second calculation processing unit 13 calculates the mutual impedance by a usual formula that does not use the above approximation formula when the condition that the target of the mutual impedance calculation is that the electrical length of the element is short and the distance is long. It is a processing means to do.

Specifically, in the equation for calculating the mutual impedance between monopoles in the method of moments, e
Computation element of xp (-jkr) / r (where j = (-1)
^The mutual impedance is calculated by using an approximate expression obtained from an expression obtained by assuming that ( ^1/2 , k is the wave number and r is the distance between monopoles) is constant in the integration interval of the monopole and is out of the integration.

More specifically, the first monopole and the first monopole
Z is the mutual impedance of two monopoles₀₀, The first model
The length of Nopole is d₁= | Z₁-Z₀｜ (however z₁so
Current distribution is 0, z₀The current distribution is 1), and the second monopole
The length of the le is d₂= | T₁-T ₀│ (t₁With current
Cloth is 0, t₀, Current distribution is 1), distance is r, wave number is k,
The angle between the first monopole and the second monopole is ψ
When the monopole length d ₁, D₂Is small enough for the wavelength
And the distance r is the monopole length d₁, D₂Against
Z on the condition that₀₀= (Η / 4πsin kd₁sin kd₂) × (1 / k
r) × [sin (kr) [cos ψ [1-cos k (z₀-Z
₁)] [1-cos k (t₀-T₁)]-Sin k (z₀−
z₁) Sin k (t₀-T₁)] + J cos (kr) [cos
ψ [1-cos k (z₀-Z₁)] [1-cos k (t₀−
t₁)]-Sin k (z₀-Z₁) Sin k (t₀−
t₁)]] (Where η = (μ₀/ Ε₀)^1/2, Μ₀: Vacuum permeability
Rate, ε₀: Dielectric constant of vacuum)
And calculate the mutual impedance.

The current calculator 14 is a processing means for calculating the current flowing through each part of the electric circuit device by solving the simultaneous equations of the moment method derived from the obtained mutual impedance. The electric field / magnetic field calculation unit 15 is the current calculation unit 1
It is a processing means for calculating the electromagnetic field intensity radiated by the electric circuit device from the calculation result of 4 and outputting the result.

[0026]

[Operation] In the calculation of mutual impedance used in the simultaneous equations of the method of moments, if the length of the monopole is a minute element (wire or surface patch) of 0.001λ (λ: wavelength) or less, and if the distance is increased, The precision loss in the calculation is due to the exp in the integral of the monopole.
One of the main causes is that the exponential function of (-jkr) / r is included. This also causes the calculation time to be long.

In the present invention, paying attention to this point, exp (-j
A first calculation processing unit 12 which calculates kr) / r as a constant in the integration section and a second calculation processing unit 13 which performs other normal calculation are prepared, and these calculation means are used for the element length. The most important feature is that they are used properly according to the application conditions regarding the distance and the distance. As a result, even if a normal double-precision calculation is performed, high-speed calculation can be performed without reducing the calculation accuracy.

An approximate expression in which the exponential function part of exp (-jkr) / r is considered to be constant in the integration section will be described below with reference to the example of FIG. 2 (A). In FIG. 2, 20,
Reference numeral 21 represents a monopole, and 22 and 23 represent current distributions of the monopole. The mutual impedance Z ₀₀ between them shall be determined. The symbols are defined as follows.

Length of monopole 20: d ₁ = | z ₁ −z ₀ | (where z ₁ is current distribution 0 and z ₀ is current distribution 1), length of monopole 21 is d ₂ = | t ₁ −t ₀ | (where t ₁ has a current distribution of 0 and t ₀ has a current distribution of 1), distance: r = (z ² + t ² −2zt cos ψ + h ² ) ^1/2 (a plane including the monopole 20 There are two parallel planes that include the monopole 21. h is the distance between the two planes.)

As is well known, the strict formula for impedance between monopoles shown in FIG. 2A is as follows. (1) Exact formula of mutual impedance (normal formula) Z ₀₀ = (jωμ / 4πs in kd ₁ sin kd ₂ ) × [∫∫
sin k (−z + z ₁ ) sin k (−t + t ₁ ) cos ψ ×
(Exp (−jkr) / r) dzdt−∫∫cos k (−z +
z ₁ ) cos k (−t + t ₁ ) × (exp (−jkr) / r)
dzdt] Here, ∫∫ represents the integration from t ₀ to t ₁ and z ₀ to z ₁ . (2) Approximation conditions If the (exp (-jkr) / r) in the integral can be regarded as almost constant in the above rigorous formula, it can be output outside the integral.

Here, k = 2π / λ, k: wave number, λ: wavelength. It is assumed that the monopole lengths d ₁ and d ₂ are sufficiently small with respect to the wavelength λ, and the distance r is sufficiently large with respect to the monopole lengths d ₁ and d ₂ . Then, changes of z z _{0 to} z ₁ and t
The change of (exp (-jkr) / r) is small with respect to the change of t _{0 to} t ₁ , and can be taken out of the integral as being almost constant. (3) Approximate expression of mutual impedance Z ₀₀ ≈ (jωμ / 4πsin kd ₁ sin kd ₂ ) × (exp
(−jkr) / r) × [cos ψ∫∫sink (−z +
z ₁ ) sin k (−t + t ₁ ) dzdt−∫∫cos k (−
z + z ₁ ) cos k (−t + t ₁ ) dzdt] The integration can be simplified by the integration formula as follows.

∫∫sin k (−z + z ₁ ) sin k (−t + t ₁ ) dzdt = ∫ _z0 ^z1 sin k (−z + z ₁ ) dz∫ _t0 ^t1 sin k (−t + t ₁ ) dt = | (1 / k) cos k (z−z ₁ ) | _z0 ^z1 × | (1 / k) cos k (t−t ₁ ) | _t0 ^t1 = (1 / k ² ) [1-cos k (z ₀ −z ₁ )] × [1-cos k (t ₀ −t ₁ )] Further, ∫∫cos k (−z + z ₁ ) cos k (−t + t ₁ ) dzdt = ∫ _z0 ^z1 cos k (−z + z ₁ ) dz∫ _t0 ^t1 cos k ( _{-t + t 1) dt = |} (1 / k) sin k (z-z 1) | z0 z1 × | (1 / k) sin k (t-t 1) | t0 t1 = (1 / k 2) sin k _{(z 0 -z 1) sin k} (t 0 -t 1) from now, finally impedance Z ₀₀ can be approximated as follows.

Z ₀₀ ≈ (jωμ / 4πsin kd ₁ sin kd ₂ ) × (1 / k ² ) × (exp (−jkr) / r) × [cos ψ [1-cos k (z ₀ −z ₁ )] _{[1-cos k (t 0} -t 1)] - sin k (z 0 -z 1) sin k (t 0 -t 1)] = (jωμ / 4πsin kd 1 sin kd 2) × (1 / k 2 ) × (1 / r) × [cos (kr) [cos ψ [1-cos k (z ₀ −z ₁ )] × [1−cos k (t ₀ −t ₁ )] − sin k (z ₀ − z ₁ ) sin k (t ₀ −t ₁ )] − j sin (kr) [cos ψ [1−cos k (z ₀ −z ₁ )] × [1−cos k (t ₀ −t ₁ )] − sin k (z ₀ −z ₁ ) sin k (t ₀ −t ₁ )]] = (η / 4πsin kd ₁ sin kd ₂ ) × (1 / kr) × [sin (kr) [cos ψ [1-cos k (z ₀ −z ₁ )] × [1−cos k (t ₀ −t ₁ )] − sin k (z ₀ −z ₁ ) sin k (t ₀ −t ₁ )] + j cos (kr) [ cos ψ [1-cos k (z ₀ −z ₁ )] × [1-cos k (t ₀ −t ₁ )] − sin k (z ₀ −z ₁ ) sin k (t ₀ −t ₁ )]] Z ₀₁ , Z ₁₀ and Z ₁₁ shown in (B), (C) and (D) of FIG.
The same applies to.

An approximate expression of impedance can be obtained from the condition that the elements are short and the distance is long as described above. It was confirmed that this approximate expression is effective when the element length is 0.05λ or less and the distance is 10 times or more the element length. Therefore, not only when the element length is 0.001λ or less and the digit cancellation occurs, but this approximate expression can be applied to other than the minute element, and thus the calculation speed can be increased.

The current calculator 14 derives simultaneous equations of the moment method from the mutual impedances thus obtained, and calculates the current flowing through the electric circuit device. The electric field / magnetic field calculation unit 15 calculates the electromagnetic field intensity radiated by the electric circuit device from the calculation result, and outputs the calculated electromagnetic field intensity, for example, in the form of a diagram.

[0036]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIGS. 3 and 4 show a processing flowchart of an embodiment of the present invention. In the figure, 30 is an input data file for managing the structural information of the meshed electric circuit device to be analyzed, 31 is a judgment table, which is a judgment used to select the calculation method of the mutual impedance. Data is managed and 32 is an output data file, which stores the calculated electromagnetic field strength.

The judgment table 31 shows the representative values of the electrical lengths of the two metal elements whose mutual impedances are to be calculated,
It holds information for determining whether to use the first calculation processing unit 12 or the second calculation processing unit 13 shown in FIG. 1 by using the electric length of the distance between two metal elements as a search key. is there. Further, when the first calculation processing unit 12 uses both the strict formula and the approximate formula for the calculation of the mutual impedance, the first calculation processing unit 12 also holds information for deciding which one to use. Instead of using the judgment table 31, the calculation method may be judged by comparing the electric length and the distance with a predetermined threshold value. The typical value of the electrical length of two metal elements is 2
One with a smaller electric length, the average of two electric lengths, or 2
The square root of the product of the two electrical lengths is used. Here, the electrical length is a length with the wavelength λ of the electromagnetic wave as a scale.

When the electromagnetic field strength calculation device is activated, as shown in the process flow of FIGS. 3 and 4, first, in step ST1, the structure information of the electric circuit device meshed from the input data file 30. Read in and set metal elements and other data (frequency, etc.) as structures and arrays.

Next, in step ST2, the processed frequencies are counted to determine whether or not the processing has been completed for all the registered frequencies. When the processing is completed, the electromagnetic field strength calculation processing is ended, and when there is an unprocessed frequency, one frequency to be processed next is selected from the unprocessed frequencies, and this selection is made in the subsequent step ST3. Calculate the wavelength λ of the frequency.

Then, in order to successively calculate the mutual impedance Z _ij , the element i (i) is selected from among the m metallic elements by the loop judgment processing in steps ST4 and ST5.
= 1 to m) and the element j (j = 1 to m) are selected, and the processing from step ST6 onward is repeated for all combinations thereof.

In step ST6, the electric length of the distance between the two metal elements selected as the calculation target of the mutual impedance Z _ij is specified, and the representative value of the electric lengths of the two metal elements is calculated to calculate the two electric values. By searching the determination table 31 using the length and the representative value as the search keys, it is determined whether the mutual impedance Z _ij is calculated by the normal formula or the approximate formula proposed by the present invention.

In the case of calculation by the usual formula, step S
Proceeding to T7, the mutual impedance Z _ij is calculated by a double precision real number using the usual formula. On the other hand, in the case of calculation using an approximate expression, the process proceeds to step ST8, and the mutual impedance Z _ij is calculated using the approximate expression described above.

For one of the elements i, 1 to m of the element j
After repeating steps ST6 to ST8, the process moves to the next element i and the same process is repeated. All elements i
When the calculation is completed for (i = 1 to m), the process proceeds to step ST9.

In step ST9, using the calculated mutual impedance Z _ij and the wave source V _i read from the input data file 30, simultaneous equations of the moment method [Z _ij ] in which the current I _i flowing through the metal element is an unknown number. [I _i ] = [V _i ] is derived and solved to obtain a current I flowing through the metal element.
ask for _i .

Then, in the subsequent step ST10, it is determined whether or not the processing has been completed for all the registered observation points by counting the processed observation points. If the processing has been completed, the process returns to step ST2. , Repeat the process for the next frequency. If the processing has not been completed for all the observation points, the process proceeds to step ST11 to calculate the electromagnetic field strength that the calculated current I _i brings to the observation points according to a prescribed calculation formula. After the calculation result is stored in the output data file 32, the process returns to step ST10 to calculate the electric field / magnetic field at all the observation points.

Regarding the method of calculating the current in step ST9 and the method of calculating the electric field and magnetic field in step ST11,
Since a conventionally known method can be used,
Detailed description here is omitted.

As described above, in the present invention, the mutual impedance Z _ij used in the simultaneous equations of the moment method is calculated by focusing on the characteristic of the mutual impedance calculation target that the electrical length of the element is short and the distance is long. Since the mutual impedance is calculated based on the predetermined approximate expression of the obtained mutual impedance, it is possible to prevent the calculation time from increasing. If this approximate expression is used, there is no calculation part corresponding to exponential integration, so that the occurrence of precision loss is reduced and the deterioration of accuracy is also prevented. Moreover, even if the calculation using this approximation formula is performed with high precision calculation using multiple precision real numbers or multiple long integers, the formula is simplified as compared with the conventional high precision calculation. Speed up is possible.

The approximation formulas used to calculate the mutual impedance between the monopoles in each of the cases (A) to (D) shown in FIG. 2 are as follows. As the conditions for applying these equations, if the lengths of the monopoles are d ₁ and d ₂ ,
The distances r >> d ₁ and d ₂ and the wavelengths λ >> d ₁ and d ₂ .

The monopole (z ₀ − shown in FIG.
For the mutual impedance Z ₀₀ between z ₁ ) 20 and the monopole (t ₀ −t ₁ ) 21, the following approximate expression described in the section “Action” is used.

[Strict expression] Z ₀₀ = (jωμ / 4πsin kd ₁ sin kd ₂ ) × [∫∫
sin k (−z + z ₁ ) sin k (−t + t ₁ ) cos ψ ×
(Exp (−jkr) / r) dzdt−∫∫cos k (−z +
z ₁ ) cos k (−t + t ₁ ) × (exp (−jkr) / r)
dzdt] Here, ∫∫ represents the integration from t ₀ to t ₁ and z ₀ to z ₁ .

[Approximate Formula] Z ₀₀ ≈ (η / 4π sin kd ₁ sin kd ₂ ) × (1 / k
r) × [sin (kr) [cos ψ [1-cos k (z ₀ −z
₁ )] × [1-cos k (t ₀ −t ₁ )] − sin k (z ₀
−z ₁ ) sin k (t ₀ −t ₁ )] + j cos (kr) [co
s ψ [1-cos k (z ₀ −z ₁ )] × [1-cos k (t
_{0 -t 1)] - sin k} (z 0 -z 1) sin k (t 0 -t
₁ )]] The mutual impedance Z ₀₁ between the monopole (z ₀ -z ₁ ) 20 and the monopole (t ₀ -t ₁ ) 21 shown in FIG. 2 (B).
Similarly, the following approximate expression is used.

[Strict expression] Z ₀₁ = (jωμ / 4πsin kd ₁ sin kd ₂ ) × [∫∫
sin k (−z + z ₁ ) sin k (t−t ₀ ) cos ψ × (ex
p (−jkr) / r) dzdt + ∫∫cos k (−z +
z ₁ ) cos k (t−t ₀ ) × (exp (−jkr) / r) d
zdt] Here, ∫∫ represents the integration from t ₀ to t ₁ and from z ₀ to z ₁ .

[Approximate Expression] Z ₀₁ ≈ (η / 4π sin kd ₁ sin kd ₂ ) × (1 / k
r) × [sin (kr) [cos ψ [1-cos k (z ₀ −z
₁ )] × [1-cos k (t ₁ −t ₀ )] − sin k (z ₀
−z ₁ ) sin k (t ₁ −t ₀ )] + j cos (kr) [co
s ψ [1-cos k (z ₀ −z ₁ )] × [1-cos k (t
_{1 -t 0)] - sin k} (z 0 -z 1) sin k (t 1 -t
₀ )]] The mutual impedance Z ₁₀ between the monopole (z ₀ -z ₁ ) 20 and the monopole (t ₀ -t ₁ ) 21 shown in FIG. 2 (C).
Similarly, the following approximate expression is used.

[Strict expression] Z ₁₀ = (jωμ / 4π sin kd ₁ sin kd ₂ ) × [∫∫
sin k (z−z ₀ ) sin k (−t + t ₁ ) cos ψ × (ex
p (−jkr) / r) dzdt−∫∫cos k (z−z ₀ )
cos k (−t + t ₁ ) × (exp (−jkr) / r) dzd
t] Here, ∫∫ represents the integration from t ₀ to t ₁ and z ₀ to z ₁ .

[Approximation Formula] Z ₁₀ ≈ (η / 4π sin kd ₁ sin kd ₂ ) × (1 / k
r) × [sin (kr) [cos ψ [1-cos k (z ₁ −z
₀ )] × [1-cos k (t ₀ −t ₁ )] − sin k (z ₁
−z ₀ ) sin k (t ₀ −t ₁ )] + j cos (kr) [co
s ψ [1-cos k (z ₁ -z ₀ )] × [1-cos k (t
_{0 -t 1)] - sin k} (z 1 -z 0) sin k (t 0 -t
₁ )]] The mutual impedance Z ₁₁ between the monopole (z ₀ -z ₁ ) 20 and the monopole (t ₀ -t ₁ ) 21 shown in FIG. 2 (D).
Similarly, the following approximate expression is used.

[Strict expression] Z ₁₁ = (jωμ / 4πsin kd ₁ sin kd ₂ ) × [∫∫
sin k (z−z ₀ ) sin k (t−t ₀ ) cos ψ × (exp
(−jkr) / r) dzdt−∫∫cos k (z−z ₀ ) c
os k (t−t ₀ ) × (exp (−jkr) / r) dzd
t] Here, ∫∫ represents the integration from t ₀ to t ₁ and z ₀ to z ₁ .

[Approximate Expression] Z ₁₁ ≈ (η / 4π sin kd ₁ sin kd ₂ ) × (1 / k
r) × [sin (kr) [cos ψ [1-cos k (z ₁ −z
₀ )] × [1-cos k (t ₁ −t ₀ )] − sin k (z ₁
−z ₀ ) sin k (t ₁ −t ₀ )] + j cos (kr) [co
s ψ [1-cos k (z ₁ -z ₀ )] × [1-cos k (t
₁ −t ₀ )] − sin k (z ₁ −z ₀ ) sin k (t ₁ −t
₀ )]] In the above equation, η is (μ ₀ / ε ₀ ) ^1/2 .

For the dipole model as shown in FIG. 5, the results calculated by normal calculation and conventional high-precision calculation (multiple precision real number or multiple precision integer) and the calculation using the approximation formula proposed by the present invention are shown. , FIG. 6, FIG. 7, and FIG. 8, respectively. This calculation result shows that the frequency is 30MHz, that is, λ
It is a calculation example when = 10 m. Monopole 20,
The length of 21 was 0.0001 m in both cases. Mutual impedance Z between two metal wire dipoles m and n
_mn is a _{Z 00 + Z 01 + Z 10} + Z 11.

FIG. 6 shows the calculation result of the normal calculation by the double precision real number using the conventional exact formula. The time required for the calculation shown in FIG. 6 was 6 seconds. When r was 0.05 m or more, digit loss occurred and the accuracy deteriorated.

Further, the calculation result by the high-precision calculation using the fixed-point multiple-precision integer using the conventional exact formula is shown in FIG.
It was as shown in. The accuracy was good, but the time required for the calculation was 380 seconds.

On the other hand, when the distance r is 0.001 m or more, the result calculated by using the above-mentioned approximate expression is as shown in FIG.
It was as shown in. Since exponential integration is not used, there is no deterioration in precision due to precision loss, and the calculation time was 4 seconds, showing a considerable improvement.

Needless to say, the present invention can be applied not only when the moment method is used for all parts of the electric circuit device, but also when the moment method is used for only part of the electric circuit device.

[0063]

As described above, according to the present invention,
In calculating the electromagnetic field intensity radiated by an electric circuit device based on the method of moments, a predetermined mutual impedance obtained based on the characteristic of the mutual impedance calculation target that the electric length of the element is short and at a long distance is calculated. By calculating the mutual impedance based on the approximate expression, the electromagnetic field intensity radiated by the electric circuit device can be calculated at high speed and with high accuracy.

[Brief description of drawings]

FIG. 1 is a principle configuration diagram of the present invention.

FIG. 2 is an example of a processing flow executed by the present invention.

FIG. 3 is a processing flowchart of an embodiment of the present invention.

FIG. 4 is a processing flowchart of an embodiment of the present invention.

FIG. 5 is a diagram illustrating a calculation example of a mutual impedance between two dipoles.

FIG. 6 is a diagram showing an example of a calculation result by a conventional normal calculation of the model shown in FIG.

FIG. 7 is a diagram showing an example of calculation results obtained by conventional high-precision calculation of the model shown in FIG.

FIG. 8 is a diagram showing an example of calculation results obtained by approximation calculation of the model shown in FIG. 5 to which the present invention is applied.

FIG. 9 is an explanatory diagram of a small loop antenna approximation method.

FIG. 10 is an explanatory diagram of a distributed constant line approximation method.

[Explanation of symbols]

 1 Processing Device (CPU / Memory) 10 Data Input Section 11 Calculation Method Selection Section 12 First Calculation Processing Section 13 Second Calculation Processing Section 14 Current Calculation Section 15 Electric Field and Magnetic Field Calculation Section

Claims (4)

[Claims] 1. An electromagnetic field intensity calculation device for calculating the electromagnetic field intensity radiated by an electric circuit device using the method of moments, comprising: data input means for inputting structural information of an electric circuit device to be analyzed; When calculating the mutual impedance that forms the simultaneous equations, the mutual impedance is calculated based on the predetermined approximate expression of the mutual impedance obtained based on the characteristic of the mutual impedance calculation target that the electrical length of the element is short and at a long distance. A first calculation processing means for calculating, and a mutual impedance is calculated by an ordinary formula that does not use the above approximation formula when the condition that the target of the mutual impedance calculation has a short electrical length of the element and a long distance is not satisfied. The first calculation unit based on the second calculation processing unit and the electrical length and the inter-element distance of the element for which the mutual impedance is calculated. Whether the calculation processing means of
The calculation method selecting means for selecting whether to use the calculation processing means, the simultaneous calculation equation of the moment method using the calculated mutual impedance, and the current calculation unit for calculating the current flowing through each element, and the calculated current An electromagnetic field strength calculation device comprising: an electric field magnetic field calculation unit that calculates an electromagnetic field strength based on a value. 2. The electromagnetic field intensity calculation device according to claim 1, wherein the approximate expression used for calculating the mutual impedance in the first calculation processing means is exp (-jkr) / r.
(Where j = (− 1) ^1/2 , k is the wave number, r
Is an approximate expression obtained from an equation that is taken out of the integral by regarding the distance between monopoles) as constant in the integration interval of the monopole. 3. The electromagnetic field strength calculating device according to claim 1, wherein the approximate expression used for calculating the mutual impedance in the first calculation processing means is a first monopole and a second monopole.
Monopole mutual impedance Z _00, a first monopole length _{d 1 = | z 1 -z 0} | ( provided that z ₁ in the current distribution is 0, z ₀ in the current distribution is 1), second The length of the monopole of d ₂ = | t ₁ −t ₀ | (where the current distribution is 0 at t ₁ and the current distribution is ₁ at t ₀ ), the distance is r, the wave number is k, and the first monopole is When the angle between the second monopoles is ψ, the monopole lengths d ₁ and d ₂ are sufficiently small with respect to the wavelength, and the distance r is sufficiently large with respect to the monopole lengths d ₁ and d ₂ . Z ₀₀ = (η / 4πsin kd ₁ sin kd ₂ ) × (1 / k
r) × [sin (kr) [cos ψ [1-cos k (z ₀ −z
_{1)] [1-cos k} (t 0 -t 1)] - sin k (z 0 -
z ₁ ) sin k (t ₀ −t ₁ )] + j cos (kr) [cos
ψ [1-cos k (z ₀ −z ₁ )] [1-cos k (t ₀ −
t ₁ )] − sin k (z ₀ −z ₁ ) sin k (t ₀ −
t ₁ )]] (where η = (μ ₀ / ε ₀ ) ^1/2 , μ ₀ : vacuum permeability, ε ₀ : vacuum permittivity) Calculator. 4. The electromagnetic field intensity calculation device according to claim 1, claim 2, or claim 3, wherein the calculation method selection means has a monopole element length of approximately 0.05λ (λ is a wavelength) or less, An electromagnetic field strength calculation device, wherein when the distance is approximately 10 times or more the element length, the first calculation processing means is selected to calculate the mutual impedance.