JPH05288786A - Method and device for measuring high-frequency leakage of gap part - Google Patents

Abstract

PURPOSE:To simplify measurement of high-frequency leakage characteristics and improve the accuracy by connecting a power measuring instrument to an open terminal of a DC brake directly through a measuring cable. CONSTITUTION:An internal conductor 21a is taken out by cutting coating at the tip of a measuring cable 21 which is connected to a power measuring instrument 20. The tip is connected nearly vertically to the outer-peripheral surface of one external conductor 3b at the peripheral part of an open edge 6a of a DC brake 1. Also, an external conductor 21b of the cable 21 is connected to the open tip of a large-diameter edge part 3a1 of the other external conductor 3a at the peripheral part of the open edge 6a of the brake 1, thus measuring an input power Pi which is supplied to the brake 1 by a feeder measuring instrument 13 and measuring a high-frequency leakage power P1 which is leaked from an outer gap 6 of the brake 1 by the measuring instrument 20 highly accurately without any electromagnetic shielding. After the measured value is multiplied by the characteristic impedance or the cable 21, it us divided by a vibration impedance of outer space, and then the obtained value is used as a high-frequency leakage power which is leaked externally from the gap part.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-frequency leak measuring method for a gap portion, which is suitable for measuring high-frequency power leaking from a gap such as a DC break of a high-frequency heating apparatus for plasma to the external space and high-frequency leakage characteristics. The present invention relates to an apparatus, and more particularly, to a method and apparatus for measuring high-frequency leakage in a gap portion, which simplifies the method for measuring high-frequency leakage and improves the accuracy of measured values.

[0002]

2. Description of the Related Art Generally, a plasma high-frequency heating device such as an ion cyclotron heating device heats the plasma in a tokamak vacuum container by high frequency, for example, but prevents the penetration of low-frequency impulses due to potential fluctuations in the tokamak vacuum container. Therefore, a gap called DC break is provided in the middle of the transmission line connected to the antenna of the high frequency heating device to insulate low frequency signals.

An example of this DC break is applied to a coaxial feeder line as shown in FIG. 4, for example. The DC break 1 cuts the coaxial cable 2 in the diametrical direction and divides it into a pair of left and right outer conductors 3a and 3b and a pair of left and right inner conductors 4a and 4b coaxially built therein. The small-diameter end 4a1 of the conductor 4a is radially inserted into the opening end of the inner conductor 4b on the right side, and the large-diameter end 3a1 of the left outer conductor 3a is inserted into the opening of the right outer conductor 3b. The inner gap 5 and the outer gap 6 are provided by being inserted into the tip portion.

Since these inner and outer gaps 5 and 6 are coupled at a high frequency through a distributed capacitor, they have no effect on the high frequency transmission characteristics and are almost the same as no gaps. Also, although it must be so configured, low frequency signals are isolated by this DC break 1.

By the way, one of the major problems in the DC break 1 is that the leaked high frequency wave 7 leaking from the open end 6a of the outer gap 6 to the external space acts as electromagnetic noise on other devices and equipment around it. It is a point that disturbs the control measurement system, causes an unmeasurable state, or malfunctions.

[0006] In particular, in the case of using a high-frequency power of MW class for high-frequency heating, in a coaxial feed line of a coupling portion where a large standing wave stands between an antenna and an impedance matching device, as in an ion cyclotron heating device. Tens of MW
Since a high frequency reaching up to 1 appears, the high frequency leaking from the outer gap 6 to the outside must be suppressed to be extremely small. For example, when the high frequency leakage characteristic of the DC break 1 is expressed in decibels of the ratio of the leakage power Pl to the input power Pi, it may be necessary to suppress it to -90 dB or less.

As an example of the conventional method for measuring the high frequency leaked from the gap of the DC break 1 as described above, there is a method shown in FIG. In this, a pair of upper and lower reducers 8a and 8b are connected to both ends of the DC break 1, and a high frequency source 11 is connected to one reducer 8b via a power supply cable 10 with a directional coupler 9 interposed therebetween. A power supply measuring device 13 is connected to the sex coupler 9 via a measuring cable 12.

Further, a dummy resistor 14 is connected to the other reducer 8a as a high frequency non-reflection end.

The electric field strength meter 15 is provided at a position separated from the DC break 1 thus constructed by a predetermined distance.
Install the half-wave dipole antenna 16 connected to
The electric field E is measured by the electric field strength meter 15, and the leakage power Pl is calculated by the following equation (1).

[0010]

[Equation 1] However, Zw is a radiation impedance. Further, the integration is performed on the entire surface area of the radiation pattern of the electromagnetic wave from the outer gap 6, but the distribution of the electric field strength is regarded as substantially spherical symmetry, and the above equation (1) is simplified as the following equation (2). To do.

[0011]

[Equation 2] Here, d is the distance from the central axis of the DC break 1 to the half-wave dipole antenna 16. Zw is equal to the wave impedance of space, and 377Ω
And

On the other hand, since the input power Pi supplied to the DC break 1 can be measured by the directional coupler 9,
The high frequency leakage characteristic can be calculated by the following equation (3).

[0013]

[Formula 3] Ld = 10log10 (Pl / Pi) (3)

FIG. 6 shows an example of the measurement result of the high frequency leakage of the DC break 1 measured by such a conventional method. In the figure, the horizontal axis is the distance d from the center of the DC break 1 to the half-wave dipole antenna 16, and the vertical axes are (2) and (3) above.
The high-frequency leakage characteristics obtained by the equations are respectively shown, and the measurement frequencies are two types of 110 MHz and 130 MHz.

What is characteristic of this measurement result is that the high frequency leakage Ld increases along the distance from the DC break 1. The cause of this is the scattered wave 1 of the electromagnetic wave scattered by the side wall 17 of the structure such as the building shown in FIG.
It is thought that this is because it interferes with 8.

[0016]

However, such a conventional high-frequency leakage measuring method has a problem that the measurement accuracy of the high-frequency leakage power is not necessarily high and the measuring method is not easy.

That is, originally, since the high frequency leakage leaking from the DC break 1 is designed and manufactured so as to be as small as possible (ideally, the high frequency leakage is eliminated),
With a high frequency power source of about 100 W prepared at the time of test inspection, the leakage power has a very small value and is easily affected by other high frequency power sources. For example, the high frequency leakage characteristic is -90 dB.
It can be seen that the leakage power when the input to the DC break 1 is 100 W is 0.1 μW, which is extremely small.

Further, unless otherwise specially designed, the high frequency leakage from the high frequency source itself (the high frequency radiated from other than the output end) is usually quite large, so the high frequency leakage leaking from the DC break 1 is concealed (masked). There are many things.

For this reason, it is very troublesome to measure the high frequency leakage characteristic of the DC break 1 by the conventional measuring method, and it is also difficult to obtain an accurate measured value.

Therefore, the present invention has been made in view of the above circumstances, and an object thereof is a high-frequency leakage measuring method for a gap portion and a device therefor capable of measuring the high-frequency leakage characteristic of a DC break easily and with high accuracy. To provide.

[0021]

According to the present invention, a measuring cable of a power measuring instrument is electrically connected directly to an open end 6a of a DC break 1 and is constructed as follows.

The invention according to claim 1 of the present application (hereinafter, referred to as the first
In the method of measuring a high frequency leak of a gap part for measuring a high frequency leaking from a gap part which insulates a low frequency signal with a gap, a power measuring instrument is electrically connected to the open end of the gap via a measuring cable. Connected to each other, multiply the measured value measured by this power measuring device by the characteristic impedance of the measurement cable, and divide by the wave impedance of the external space, and the value thus obtained is transferred from the gap part to the external space. It is characterized in that it is the high frequency leakage power value that leaks.

The invention according to claim 2 of the present application (hereinafter referred to as the second invention) includes a gap portion for insulating low frequency signals with a gap, and a measurement cable at the open end of the gap portion. An electrically connected power measuring device and a measurement value measured by this power measuring device are multiplied by the characteristic impedance of the measurement cable, and the value obtained by dividing by the wave impedance of the external space is obtained by the gap portion. And a calculation means for calculating as a high frequency leakage power value that leaks to the external space.

[0024]

[Function] Since the power measuring device is electrically connected directly to the open end of the gap through the measuring cable, the high frequency that leaks from the open end of the gap to the outside is very small. However, most of them can be captured and measured. Therefore, the accuracy of the measured value can be increased.

Further, since the power measuring device is directly electrically connected to the open end of the gap portion through the measuring cable,
There is no risk that this power measuring device will detect and measure high frequencies leaking from other devices such as high frequency sources other than the open end of the gap.

Therefore, unlike the conventional example, there is no need to detect high-frequency leakage points such as a high-frequency source other than the open end of the gap and to provide electromagnetic shielding to these, and the measurement becomes very simple.

[0027]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the first invention of the present application. In FIG. 1, the same parts as those shown in FIGS. 4 and 5 are designated by the same reference numerals.

In FIG. 1, a DC break 1 divides the coaxial cable 2 in the middle in the diametrical direction to form a pair of left and right outer conductors 3a and 3b, and a pair of left and right inner conductors 4a and 4b coaxially built therein. The inner conductor 4 on the left side of the figure
The small-diameter end 4a1 of a is inserted into the opening tip of the right inner conductor 4b, and the large-diameter end 3a1 of the left outer conductor 3a is inserted into the opening tip of the right outer conductor 3b. An inner gap 5 and an outer gap 6 are provided. Of these, the outer gaps 5 and 6 are coupled at a high frequency through a distributed capacitor, so that they have no effect on the high-frequency transmission characteristics and are almost equivalent to the absence of a gap, but at low frequencies. The signal is isolated at this DC break 1.

The DC break 1 has a pair of reducers 8a and 8b connected to both ends thereof, and one reducer 8b.
Is connected to a high-frequency source 11 via a power supply cable 10 with a directional coupler 9 interposed therebetween, the directional coupler 9 is connected to a power supply measuring device 13 via a measurement cable 12, and the other reducer 8a is connected. A dummy resistor 14 is connected as a high frequency non-reflective terminal.

Further, in this embodiment, the insulating jacket at the tip of the measuring cable 21 made of a coaxial cable connected to the power measuring device 20 is cut off so that the inner conductor 21a extends beyond the tip of the insulating jacket. Make a DC break 1 at the extended end.
One around the open end 6a (right side in FIG. 1)
Is connected to the outer peripheral surface of the outer conductor 3b substantially perpendicularly.

Further, the outer conductor 21b of the measuring cable 21
At the periphery of the open end 6a of the DC break 1 is electrically connected to the open end of the large-diameter end 3a1 of the other (left in FIG. 1) outer conductor 3a.

Therefore, the power supply measuring device 13
The input power Pi supplied to the break 1 can be measured, and the high frequency leakage power Pl leaking from the outer gap 6 of the DC break 1 can be measured by the power meter 20.

Further, the characteristic impedance Zo of the measurement cable 21 and the input impedance Zi of the power measuring device 20 are matched, and most of the high frequency leaked from the open end 6a of the DC break 1 is transmitted to the measurement cable 21. Therefore, it can be considered approximately that the open end 6a of the outer high frequency wave 6 is terminated with ZoΩ.

Therefore, the equivalent circuit of this DC break 1 has the first, second and third transmission lines 30, 3 as shown in FIG.
It can be represented as a combination of 1,32. The first transmission line 30 corresponds to the outer gap 6, its characteristic impedance is Zl, the second transmission line 31 corresponds to the inner gap 5, its characteristic impedance is Z2, and the third transmission line 32 is internal. The characteristic impedance is Z3 corresponding to the coaxial portions formed by the conductors 4a and 4b and the outer conductors 3a and 3b, respectively.

Since Rd33 represents the dummy resistor 14,
Naturally, Rd = Z3. R134 means a load connected to the open end 6a of the outer gap 6,
When the measurement cable 21 is connected, Rl = ZoΩ, and when a high frequency is radiated into space, Rl = ZwΩ. X35
Is the reactance assumed to be present at one end of the inner gap 5.

The circuit of the outer gap 6 is R134.
Since it is the first transmission line 30 having the characteristic impedance Zl which is terminated by the load, it is understood that the high frequency power absorbed by the load Rl34 at the open end 6a of the outer gap 6 is generally inversely proportional to the terminating resistance Rl.

Therefore, by using the high frequency power Pl (Zo) measured by directly connecting the measurement cable 21 to the open end 6a of the outer gap 6, the high frequency power Pl (Zw) used for radiating a high frequency to the space is obtained. It can be expressed as follows.

[0039]

[Equation 4]

The leakage power Pl with respect to the input power Pi
When the high frequency leakage characteristic is represented by the ratio of, the following equation (5) can be obtained by substituting equation (4) into Pl of equation (3).

[0041]

[Equation 5]

Further, since the input impedance of the power measuring device 20 is usually 50Ω, Zo = 50Ω and Zw = 3.
If it is 77Ω, the following expression (6) is established.

[0043]

[Equation 6]

That is, the value obtained by subtracting 8.77 dB from the ratio of the high frequency leakage power Pl to the input power Pi is the high frequency leakage characteristic of DC break 1.

Therefore, high sensitivity (about 100 dB)
If there is a network analyzer of, it is possible to measure with a circuit configuration as shown in FIG.

That is, the output from the high-frequency oscillator built in the network analyzer 22 is fed to the power feeding cable 10
To the DC break 1, and connect the measurement cable 23 connected to the other end of the DC break 1 to the network analyzer 2
The measurement cable 21 connected to the reference signal input terminal 2 and connected to the open end 6a of the outer gap 6 of the DC break 1.
The signal received by is applied to the input terminal of the network analyzer 22. With this configuration, the comparator (not shown) inside the network analyzer 22 automatically calculates the first term on the right side of the equation (6), and by subtracting 8.77 from the calculated value, the high frequency leakage characteristic can be obtained. ..

Therefore, according to this embodiment, since the open end 6a of the DC break 1 through which high frequency leaks to the external space is directly connected via the measuring cable 21 of the power measuring device 20 or the network analyzer 22, the DC break 1 Since most of the leaked high frequency leaked from the open end to the external space can be introduced into the power measuring device 20 or the network analyzer 22 through the measurement cable 21, even if the leaked high frequency power is a very small value, other electromagnetic waves can be emitted. Accurate measurement is possible without being affected by noise.

For this reason, in the present embodiment, the accuracy of measurement of the leakage high frequency power and the high frequency leakage characteristic is improved, and measures such as electromagnetic shielding of the high frequency source 11 and other devices that may leak high frequencies are omitted. Therefore, the measurement method can be simplified.

[0049]

As described above, according to the present invention, the power meter is directly connected to the open end of the gap portion where high frequency is leaked to the external space through the measuring cable. Most of the high frequencies leaked into the space can be captured and measured by the power meter.

Therefore, the accuracy of measurement or calculation of the high frequency leaking from the gap portion and the high frequency leak characteristic can be improved, and in addition to the peripheral portion other than the gap portion, high frequency leakage is electromagnetically shielded. Since it is not necessary to take measures such as doing so, the measurement method is correspondingly simplified.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a configuration for carrying out an embodiment of a first invention of the present application.

FIG. 2 is an equivalent circuit diagram of the DC break shown in FIG.

FIG. 3 is a configuration diagram of an embodiment of the second invention of the present application.

FIG. 4 is a perspective view showing a general configuration of a DC break of a coaxial feeder in a partial vertical section.

FIG. 5 is a diagram showing a conventional leakage high frequency measuring method.

6 is a graph showing an example of a result measured by the conventional method shown in FIG.

[Explanation of symbols]

 1 DC break 2 Coaxial cables 3a, 3b Pair of outer conductors 4a, 4b Pair of inner conductor 5 Inner gap 6 Outer gap 6a Open end 8a, 8b Pair of reducer 9 Directional coupler 10 Feed line 11 High frequency source 13 Supply power measurement Instrument 20 Power meter 21, 23 Measurement cable 21a Inner conductor 21b Outer conductor 22 Network analyzer

Claims (2)

[Claims] 1. A method for measuring high frequency leakage of a gap part for measuring a high frequency leaking from a gap part for insulating a low frequency signal with a gap, wherein an electric power measuring device is electrically connected to an open end of the gap via a measuring cable. Connected to the, and the measured value measured by this power measuring device is multiplied by the characteristic impedance of the measurement cable and divided by the wave impedance of the external space, and the value obtained by this is transferred from the gap part to the external space. A high frequency leak measuring method for a gap portion, which is characterized in that a high frequency leak power value is used. 2. A gap part for insulating low-frequency signals with a gap, a power measuring device electrically connected to an open end of the gap part through a measuring cable, and a measurement measured by the power measuring device. And a calculation means for multiplying the value by the characteristic impedance of the measurement cable and calculating a value obtained by dividing by the wave impedance of the external space as a high-frequency leakage power value leaking from the gap portion to the external space. The high-frequency leak measuring device of the characteristic gap part.