Data processing: structural design – modeling – simulation – and em – Electrical analog simulator – Of electrical device or system
Reexamination Certificate
1998-02-03
2001-02-06
Teska, Kevin J. (Department: 2763)
Data processing: structural design, modeling, simulation, and em
Electrical analog simulator
Of electrical device or system
C703S005000
Reexamination Certificate
active
06185517
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an electromagnetic field intensity computing apparatus for computing the intensity of the electromagnetic field of an electric circuit device based on the moment method.
2. Description of the Related Art
Since an unnecessary electric wave emitted by an electric circuit device interferes with TV, radio, or other electric waves, various strict restrictions have been put in place in many countries. For example, Japan has issued the VCCI Standard, the U.S. has issued the FCC Standard, and Germany has issued the VDE Standard.
To meet such electric wave restrictions, various actions should be taken using shielding technologies, filtering technologies, etc. Accordingly, it is necessary to quantitatively simulate these actions to determine the extent to which extent the electric wave can be reduced. Since the simulation of the electromagnetic analysis requires a long process time using a computer, it is necessary to prepare a high-speed and high-precision computing apparatus to compute the intensity of the electromagnetic field of an electric circuit device.
In a method of computing the electromagnetic field intensity, the electromagnetic field intensity of an object can be easily computed by a well-known logic equation, given a current flowing through each portion of the object. The current value can be logically obtained by solving the Maxwell equations (electromagnetic wave equations) under given conditions. However, no exact solution has been obtained by equations under complicated boundary conditions on an object of an optional shape.
Therefore, any solution for obtaining the current used by the electromagnetic field intensity computing apparatus refers to, more or less, an approximation. A typical approximate computation can be a small loop antenna approximation, a distributed constant line approximation, or a 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. In this approximation, the current through the loop is assumed to be flat and computed by the method of computing the concentrated constant circuit.
FIGS. 1A and 1B
illustrate the small loop antenna approximation.
FIG. 1A
shows a circuit model comprising a driver
10
that is a wave source circuit; a receiver
11
that is a load circuit; a wiring
14
connecting the driver
10
to the receiver
11
, and a dielectric portion
12
inserted between the grounding wire layer
13
and wiring
14
.
In
FIG. 1A
, the distance between the driver
10
and receiver
11
is l and the distance between the wiring
14
and the grounding wire layer
13
is h.
FIG. 1B
is a diagram showing the equalizing circuit of the circuit model shown in FIG.
1
A.
In
FIG. 1B
, the driver
10
is represented by an equalizing circuit comprising a power source V, resistor R
1
, and capacitor C
1
. The receiver
11
can be represented by an equalizing circuit comprising a capacitor C
2
.
A line current I flows as a loop as shown in FIG.
1
B. The area of the loop is represented by S (=lh). The straight line below the line current I shown at the upper portion in
FIG. 1B
indicates that the line current I is constant (flat) regardless of the position of the line.
The line current I can be computed through a concentrated constant circuit comprising the equalizing circuit of the driver
10
and receiver
11
by the following equation (1).
I
=
C
2
C
1
+
C
2
1
R
+
jω
C
1
C
2
C
1
+
C
2
ω
=
2
π
f
:
angular
frequency
f
:
frequency
(
1
)
Then, using the line current I computed by the above equation (1), a radial electromagnetic field E is computed by the following approximation (2).
E
=
A
S
I
f
2
r
A
-
1.32
×
10
15
:
constant
r
:
distance
up
to
the
observation
point
(
2
)
As described above, the computation according to the small loop antenna approximation involves a very simple equation, and the computation can be performed at a high speed.
However, since the line current I is assumed to be constant on the line, the current distribution on the line varies when the frequency f refers to a high frequency, thereby considerably lowering the precision.
Thus, the computation using the small loop antenna approximation is the simplest method of all the above listed approximations, but in practice it is not used at all because it is inferior in precision if the size of the loop cannot be ignored when compared with the wave length of the electromagnetic wave.
The distributed constant circuit approximation refers to a method of considering the current distribution to improve the precision.
The distributed constant circuit approximation refers to a method of obtaining a current value by applying the equation of the distributed constant line to an object to be represented as a one-dimensional structure by an approximation.
The computation can be easily done in this method. The computation time and storage capacity are increased in proportion to the number of analysis elements. Furthermore, the analysis is made including the reflection and resonance of a line, etc. Therefore, in the distributed constant circuit approximation, a high-speed and high-precision analysis can be made on an object to which a one-dimensional approximation can be applied.
FIGS. 2A and 2B
show the above described distributed constant line approximation.
The circuit model shown in
FIG. 2A
is the same as that shown in
FIG. 1A
, and the detailed description is omitted here.
FIG. 2B
shows the equalizing circuit of the circuit shown in FIG.
2
A.
In
FIG. 2B
, the equalizing circuit of the driver
10
and receiver
11
is the same as that shown in FIG.
1
B.
When the frequency f becomes high and the wave length &lgr; becomes shorter than the line length l in
FIG. 2A
, a standing wave current flows through the line and the distribution of the current varies with the line position. In
FIG. 2B
, for instance, the value of the line current I is larger on the driver
10
side while the value of the line current I is smaller on the receiver
11
side. The value of the line current I at a certain point is represented by I(x) while the voltage at a certain point is represented by V(x), where x indicates a variable representing the distance from the receiver
11
, that is, the origin (x=0). The driver
10
refers to (x=L).
In
FIG. 2B
, “Zo” indicates a characteristic impedance in a distributed constant line. “Z
L
” indicates a characteristic impedance at the receiver
11
. ‘&bgr;’ indicates a wave number and is represented by (&bgr;=&ohgr;/c=2&pgr;/&lgr;). The wave length &lgr; is represented by (&lgr;=c/f). The ‘c’ indicates the velocity of light.
The current distribution I(x) of the line can be obtained by the following equation (3).
I
(
x
)
=
V
(
L
)
Z
o
×
Z
o
cos
β
x
+
j
Z
L
sin
β
x
Z
L
cos
β
L
+
j
Z
o
sin
β
L
(
3
)
As described above, the computation done using the distributed constant line approximation allows a high-speed and high-precision analysis to be made on an object to be processed as a one-dimensional structure by an approximation.
However, some objects that cannot be processed as one-dimensional structures by an approximation are not analyzed.
The moment method is one of the solutions of an integral equation derived from the Maxwell electromagnetic wave equations, and can process a 3-dimensional object. In this method, an object is divided into small elements to co
Mukai Makoto
Ohtsu Shinichi
Fujitsu Limited
Jones Hugh
Staas & Halsey
Teska Kevin J.
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