Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Electrical signal parameter measurement system
Reexamination Certificate
1999-02-24
2001-11-20
Grimley, Arthur T. (Department: 2852)
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Electrical signal parameter measurement system
C702S075000, C702S076000, C702S117000
Reexamination Certificate
active
06321169
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to technology of analyzing circuit constants of inductance element. More specifically, the present invention relates to equivalent circuits of inductance element that are also suitable in the case that ferrite material is used, methods of analyzing circuit constants of the same, and simulator and record media of the same.
BACKGROUND OF THE INVENTION
There are many electronic appliances wherein an inductance element is installed, ferrite material is used for the electric signal line and the power line thereof, to prevent electromagnetic interference. FIG.
20
(A) shows a model circuit of such electronic appliances. In FIG.
20
(A), an inductance element
12
connects to the output end of inverter IC
10
whereto a voltage of 5 volts is placed, and line(cable)
14
connects to the output end of inductance element
12
. Inverter IC
16
connects to the output end of line
14
. FIG.
20
(B) shows a frequency characteristic of the inductance element
12
. In FIG.
20
(B), Z, R, and X represent impedance, resistance part, and reactance part, respectively. As FIG.
20
(B) shows, reactance component X decreases and resistance component R increases as the frequency becomes higher. When a pulse signal is input into such an electric signal line stated above, signals with wave forms as shown in FIG.
20
(C) are read at the measurement point PD.
It is a common practice to depend on measured values in selecting an inductance element, and confirming what are the effects caused by the inserted element, and the like. However, if it is made possible to obtain results equivalent to measured values by simulations, measurement will no longer be necessary, and the time for reviewing may be shortened. Thus, to support this assumption, creating an equivalent circuit that demonstrates characteristics of the inductance element well is under study.
Generally, LsCpRp parallel equivalent circuit as shown in FIG.
21
(A) is well known as the equivalent circuit stated above. This is a circuit wherein inductance Ls, capacitance Cp, and resistance Rp are in parallel connection. If circuit constants of an inductance element that has the same frequency characteristic as shown in FIG.
20
(B) are determined by using such an equivalent circuit, the process is as follows.
First, impedance Z that represents the impedance of the whole equivalent circuit shown in FIG.
21
(A) is given by the equation, Z=R+jX. In this equation, “R”, “X”, and “j” represents resistance component (real number), reactance component, and imaginary unit, respectively. Then, resistance component R and reactance component X are given by Expressions 1 and 2, respectively, as follows:
R
=
(
2
π
f
·
Ls
)
2
/
Rp
(
1
-
(
2
π
f
)
2
Ls
·
Cp
)
2
+
(
2
π
f
·
Ls
)
2
/
Rp
2
Expression
1
X
=
2
π
f
·
Ls
(
1
-
(
2
π
f
)
2
Ls
·
Cp
)
(
1
-
(
2
π
f
)
2
Ls
·
Cp
)
2
+
(
2
π
f
·
Ls
)
2
/
Rp
2
Expression
2
In these expressions, “f” represents frequency. In the frequency domain wherein resistance component R is small and the expression Z≈jX holds, Expression 3 holds. When the frequency is 1 MHz, reactance component X measures 85 &OHgr;. Substituting this value of X in Expression 3 yields Ls=13. 5 &mgr;H.
X=27&pgr;f·Ls Expression 3
Secondly, at the resonance point, Expression 4 holds.
Expression 4
1=(2&pgr;f)
2
LsCp, R=Rp
With this Expression, Rp (measured value of resistance component R at the resonance point)=640 &OHgr; is selected. Regarding Cp, substituting the values R=200 &OHgr; (measured value of resistance component R at 1 G Hz), Ls=13.5 &mgr;H, and Rp=640 &OHgr; Expression 1 yields Cp=0.37 pF. Applying the selected values of circuit constants Ls=13.5 &mgr;H, Rp=640 &OHgr;, and Cp=0.37 pF to the equivalent circuit of FIG.
21
(A) gives the impedance characteristic as shown in FIG.
21
(B).
Comparing FIG.
21
(B) that shows a simulation result by making use of an equivalent circuit with FIG.
20
(B) that shows measured values clearly indicates that there is a big difference between the two graphs, and that the equivalent circuit in FIG.
21
(A) does not make an accurate analysis of the measured values. Especially, values of reactance component X at around 7.5 MHz are too large in FIG.
21
(B). This indicates that structuring a simulator with the equivalent circuit in FIG.
21
(A) does not bring about sufficiently accurate results.
Next, we are going to select circuit constants of an inductance element that has the same impedance frequency characteristic as shown in FIG.
22
(A), by using the equivalent circuit of FIG.
21
(A). Just as in the case of comparing FIG.
21
(B) with FIG.
20
(B), the value Ls=0.96 &mgr;H is selected because a measured value of reactance component X at 10 MHz is 60 &OHgr;. At the resonance point, the expressions 1=(2&pgr;f)
2
LsCp and R=Rp hold. Therefore Rp (a measured value of resistance component R at the resonance point)=1170 &OHgr; is selected. The value Cp=0.094 pF is found by substituting the values R=530 &OHgr; (an actual value of “R” at 1.8 GHz), Ls=0.96 &mgr;H, and Rp=1170 &OHgr; in the said Expression 1.
Applying the selected values of circuit constants Ls=0.96 &mgr;H, Rp=1170 &OHgr;, Cp=0.094 pF to the equivalent circuit of the FIG.
21
(A) yields the impedance characteristic as shown in FIG.
22
(B). There is a significant difference between FIG.
22
(A) and FIG.
22
(B). This indicates that the equivalent circuit of FIG.
21
(A) does not make an accurate analysis of measured values. Especially, a value of reactance component X at around 200 MHz is too large in FIG.
22
(B). In addition, in FIG.
22
(B), the value of reactance component X is the largest at around 100 MHz, and values of resistance component R are smaller up to around 40 MHz. These are also differences from FIG.
22
(A). This also indicates that the equivalent circuit in FIG.
21
(A) does not make an accurate analysis of measured values.
These inconveniences is attributed to the fact that the frequency characteristic of the ferrite material used in inductance element
12
can not be demonstrated by the equivalent circuit of FIG.
21
(A). It is well known that each ferrite material has its specific resonance frequency, and brings about phenomenon of magnetic resonance in the frequency domain above the level of the said specific resonance frequency. Therefore, permeability temporally decreases (when considering it as an inductance element, value decrease of reactance component X occurs), or increases at the specific oscillation frequency.
SUMMARY OF THE INVENTION
The present invention focuses attention on the above mentioned points, and has purposes of providing an equivalent circuit with high accuracy that well demonstrates characteristics of an inductance element, circuit constants, analysis methods of the same, and simulator of the same. Another purpose is to provide equivalent circuit of inductance element suitable for inductance element wherein ferrite material is used, analysis methods of the same, a simulator and record medium of the same.
An equivalent circuit of inductance element of the present invention comprises a parallel circuit whereto an inductance, a capacitance, and a resistance are connected in parallel. And the present invention features that said inductance is magnetically coupled to closed circuits comprising a resistance and other inductance. A circuit constant analysis method of inductance element of the present invention features obtainment of the desired impedance frequency characteristic of an inductance element by adjusting the circuit constants of said closed circuit.
The above and other objects,
Grimley Arthur T.
Le John
McDermott & Will & Emery
Taiyo Yuden Co. Ltd.
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