JP2000111598A - Linear coupling transmission line cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a linear coupling transmission line cell which eliminates multiple reflection and widens used frequency zone by generating frequency window with large Q. SOLUTION: A line cell has external conductors 4, 5 and 6 provided with a taper part coupled in one on both sides center, connector means 10, 11, 12 and 13, internal conductor, internal conductor support means 17 and 18, and an open/close means where an electromagnetic wave shield window is formed. The internal conductor is placed in internal space so as to be isolated from the external conductors 4, 5 and 6 and constituted of an upper side first internal conductor plate 7 positioning in line with the connector means 10 and 12 and a lower side second internal conductor plate 8 positioning in line with the connectors 11 and 13 and forming a parallel plane facing to the upper first internal conductor plate 7.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a coupled transmission line (Co).
When transmitting power in opposite directions inside an upled transmission line, low impedance electromagnetic waves (magnetic fields) are generated at points where they meet in phase, and high impedance electromagnetic waves (electric fields) are generated at points with a phase difference of 180 °. Electromagnetic immunity (EMS: Electromagnetic)
Tic Susceptibility and Electromagnetic Interference (EMI: Electr)
The present invention relates to a linear coupled transmission line cell for generating a standard electromagnetic wave that is always required in fields such as omagnetic interference (Magnetic Interference) measurement, electromagnetic field probe calibration, and wireless device sensitivity measurement.

[0002]

2. Description of the Related Art In general, TEM cell devices include a Crawford TEM cell, a Giga-Hertz TEM cell (GTEM cell),
Triple TEM cell (TTEM cell), wire TEM cell (Wire TEM cell: WTEM cell), improved GTEM cell, TEM cell for automatic measurement, 6
There are various types such as terminal TEM cells.
They can be broadly classified into species. "One-end TEM cell" having an input / output terminal at one end like a GTEM cell, WTEM cell, TTEM cell, improved GTEM cell, etc .; Crawford TEM cell (one name, also called symmetric TEM cell); asymmetric Type TEM cell, TEM cell for automatic measurement,
It can be classified as a "double-ended TEM cell" having input / output terminals at both ends, such as a 6-terminal TEM cell. Both of these are used for unnecessary electromagnetic wave measurement, electromagnetic wave immunity measurement, antenna calibration, etc., but the former can only perform tests in the far field, and the latter should support far-field and near-field tests. They differ in that they can be

[0003] The above-mentioned double-sided TEM cell can be further divided into two types. That is, Crawford TEM
TEM cells that support only vertical polarization, such as cells, asymmetric TEM cells, coupled transmission line cells, etc .;
TEM that supports both vertical and horizontal polarization such as M cell, TEM cell for automatic measurement, rotating cylindrical TEM cell, etc.
Can be divided into cells.

[0004] In general, a coupled transmission line cell, which is one of the TEM cells that support only vertical polarization, has approximately four times higher electromagnetic wave uniformity and approximately twice as good power as existing facilities. I have.

[0005] However, the conventional coupled transmission line cell, for example, the coupled transmission line cell disclosed in Japanese Patent No. 137576 of the present applicant has the characteristics that the electromagnetic wave uniformity is extremely high and the power utility is excellent. As shown in the figure, the upper and lower inner conductors 101 and 102 have a bent structure in which the distance between both ends is gradually narrowed from both ends of the DUT region 201 to the coaxial connector connection portions on both sides. Therefore, even if the angle error is small, the upper and lower inner conductors 10
There is a problem that an error with respect to the position of the terminal 103 of the first and the second 102 is large and impedance matching is troublesome.

The reflection 105 caused by multiple points such as the upper and lower inner conductors 101 and 102 on both sides of the DUT 201 induces the reflection of a traveling wave or the reflection on the wall of the outer conductor 104. Occurs and Q (Quality Facto
There is a technical problem that r) becomes smaller. This is shown in FIG.
Since the standing wave in the range of 149 MHz to 200 MHz is high as shown in FIG.
w) cannot be used, and the available frequency band is reduced, and angular waves are generated at the bent portions of the upper and lower inner conductors 101 and 102, and the angular waves are generated in an area where the device under test is placed. The electromagnetic field probe for measuring whether a mobile phone is harmful to the human body has been acting as a problem of distorting the standard electromagnetic wave in the uniform field area.
Calibration in such a direction should always be performed in order to measure the electric field while being fixed horizontally with respect to the traveling direction of most radio waves.Calibration of such a position in an electromagnetic field probe is very important. is there.

[0007] The calibration of the electromagnetic field probe used in the field of research on the effects of electromagnetic waves on the human body requires calibration at a high point in the measurement frequency band. Therefore, the calibration is performed using a small coupled transmission line cell. When trying to use transmission line cells in the field probe calibration field,
Since the power supply N-type connector of the outer conductor is close and dense, there is a problem that calibration cannot be performed so that the probe is positioned parallel to the traveling direction of the radio wave.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to provide upper and lower inner conductors in a coupled transmission line in parallel so as not to bend horizontally. In addition, by installing the power supply terminals at a predetermined distance from each other, impedance matching can be easily realized, multiple reflections can be eliminated, and a frequency window with a large Q can be generated, thereby expanding the frequency band used. It is to provide a transmission line cell.

[0009]

In order to achieve the above object, the present invention provides an internal space for locating a device under test, and a tapered portion integrally connected to both sides of a central portion. An outer conductor provided with end portions formed to face each other so as to block the end portions of the tapered portions on both sides, and an outer conductor provided at an upper and lower position of one end portion of the outer conductor, a predetermined distance therebetween. First and second connector connection means arranged to have a separation distance, and third and third connector connection means provided at upper and lower positions of the other end of the outer conductor and arranged to have a predetermined separation distance therebetween. And an upper conductor plate provided in an internal space of the connector so as to be separated from the external conductor and positioned in line with the first and third connector connection means, and the second and fourth connectors. Straight line with connecting means An inner conductor consisting of lower conductor plate while located, forming the upper conductor plate parallel surface opposed to,
An inner conductor supporting means for fixing the inner conductor to the inside of the outer conductor; and a predetermined size for observing the state of the device under test, which is provided to be openable and closable on one side surface of the central outer conductor. The present invention provides a linear coupled transmission line cell including an opening / closing means having an electromagnetic wave shielding window.

[0010]

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

The linear coupled transmission line cell according to the present invention has Q
The present invention is embodied in such a manner that a large resonance is exhibited to give a better broadband characteristic, and that the electromagnetic field probe can be calibrated for a vertical component in the traveling direction of the electromagnetic wave. In the present invention, as shown in FIGS. A test object region 1 on which a test object is mounted, a coaxial connector connection portion 3 for connecting a coaxial cable connector to an external main body, and a taper connecting the test object region 1 and the coaxial connector connection portion 3 And an area 2.

Here, the test object region 1 includes a center outer conductor 4 having an inner space, a first inner conductor 7 and a second
And an internal conductor 8. Each of the first and second inner conductors has a planar shape in which the width is narrowed toward the center at both ends, and the front shape is linear. The first internal conductor 7 and the second internal conductor 8 have a structure in which they are installed vertically inside the center external conductor 4.

The center outer conductor 4 of the test object region 1 has a door 15 with a shielding window 16 for observing the state of the test object on one side surface, and a body 15 on the bottom surface. There is provided a support base 14 on which wheels are mounted so as to support the whole and to make it movable. Here, the shielding window may be formed by coating a transparent material such as glass or plastic with a thin coating of gold or silver, or by using a thin metal mesh wire mesh to shield electromagnetic waves.

The first inner conductor 7 is supported by a first support 17 so as to be suspended on the inner upper surface of the center outer conductor 4, and the second inner conductor 8 stands upright from the inner bottom surface of the center outer conductor 4. It is supported by the second support base 18.

The coaxial connector connecting portion 3 includes connectors 10 to 13 for supplying power to both ends of the first and second inner conductors 7 and 8, and a connector for supporting the respective connectors and connecting them to an external body. A first outer conductor 6 is provided. At this time, the first to fourth connectors 1 are separated from each other by a predetermined distance on the upper and lower surfaces of the first outer conductors 6 on both sides, respectively.
It has a structure with 0, 11, 12, and 13 attached,
The tapered region 2 is provided with a second external conductor 5 for connecting the central external conductor 4 of the device under test region 1 and the first external conductor 6 of the coaxial connector connection portion 3 at a predetermined gradient.

Therefore, as shown in the front sectional view of the coupled transmission line cell in FIG. 3, the first inner conductor 7 is horizontally aligned with the left end first connector 10 and the right end third connector 12. And the second inner conductor 8
Similarly, the second connector 11 and the fourth connector 13 are connected while being located in a straight line.

On the other hand, in such a test object region 1,
The uniform field region where the DUT is located, that is, the 1/3 center region between the inner conductor and the outer conductor (IEC10 which is an international standard)
00-4-3, IEC: International Electrotechnic
al Commission) as much as possible, enabling measurement of electromagnetic interference and immunity to various test objects, and field uniformity to enable the generation of high-quality standard electromagnetic waves in a uniform field region. provide.

The uniformity in the uniform field region has better characteristics than the conventional TEM cell. Because the conventional T
In the case of an EM cell, the internal electromagnetic field distribution is based on the first outer conductor 6 on both sides.
The uniformity is destroyed by the influence of the electromagnetic field formed by the potential difference between the inner conductor and the inner conductor. However, the inner conductor is placed vertically in parallel with the structure of the present invention, and the voltage is simultaneously supplied from both ends. And the magnetic field component formed in the vertical direction of such an electric field are cancelled.

Therefore, in order to satisfy the conditions that the maximum uniformity (field uniformity) must be provided to enable measurement of electromagnetic wave interference and electromagnetic wave immunity, etc., and the generation of high-quality standard electromagnetic waves in a uniform field region. The first and second inner conductors 7 and 8 can be installed close to the upper and lower wall surfaces of the center outer conductor 4 to spread the uniform field area, but closer to the side wall of the first outer conductor 6, which is Since the electromagnetic wave is abandoned on the wall surface of the first outer conductor 6 to break the uniformity, the uniformity of the electromagnetic wave is deteriorated.

When the horizontal and vertical lengths of the central outer conductor 4 are determined, the uniformity of the uniform field region (CISPR24 specifies that the electric field should be within 6 dB deviation, and IEC
In the case of 1000-4-3, the first and second inner conductors 7 and 8 are as far as possible within a range satisfying the requirement that the occupied area ratio does not secure 75% or more.
It is necessary to set the structure so that impedance matching is performed while widening the space between them.

In the present embodiment, in consideration of the above points, as shown in FIG. 5, the width of the first and second inner conductors 7 and 8 of the region under test 1 is changed to the side wall of the first outer conductor 6. The structure is such that a wider uniform field region can be secured by installing the inner outer conductor 4 close to the upper and lower surfaces of the inner wall within a limit where the electromagnetic waves are not abandoned.

The first and second inner conductors 7, 8 are both the characteristic impedance of a general coaxial cable.
Since the positions of the first and second inner conductors 7 and 8 are fixed, the width of the first and second inner conductors 7 and 8 must also be determined. Must be changed to That is, in the case of a model produced for EMI / EMS,
The first and second inner conductors 7 and 8 are configured to supply power so as to have the same magnitude of input voltage and 180 ° phase difference in order to produce a sophisticated operation.
It is preferable to determine the characteristic impedance _Z0o matching structure by supplying power.

If the first internal conductor 7 and the second internal conductor 8 have a phase difference of 180 ° and the same voltage in the test object region 1, they have a magnitude at the center of the test object region. Although they are the same and form magnetic fields in mutually opposite directions, they cancel each other. On the other hand, electric power is supplied so that the traveling directions of radio waves are opposite to each other. Has the value of

At this time, if the voltage at one end is adjusted, any radio wave impedance (37
(7Ω or more) can be realized. For example, in the present invention, at the time of impedance matching of the first and second inner conductors 7 and 8, the first and second connectors 10, 11 or the third and fourth connectors 12, 13 located on one of the first outer conductors 6 are provided.
In contrast, when feeding odd mode power as the opposite phase,
The formed characteristic impedance has the characteristic impedance of the third and fourth connectors 12 and 13 or the first and second connectors 10 and 11 to be connected.

Also, the first to fourth power supply terminals
To minimize reflections at the connector 10, 11, 12, 13, and feeding only one of the terminals, it is preferable to determine the characteristic impedance Z ₀ matching structure as one terminal feeding system for all the remaining termination.

If the first internal conductor 7 and the second internal conductor 8 have the same phase difference with the outer conductor and the same voltage in the DUT region 1, respectively, Electric fields are formed at the center of the same magnitude and opposite to each other. It has twice the value.

At this time, if the voltage at one end is adjusted, any radio wave impedance (37
(7Ω or less) is possible. That is, the specific impedance determined as the even mode power supply, which is a method of supplying power so that the input voltage has the same magnitude and the same phase difference, is Z _0e
In this case, since the relationship of Z ₀ = √ (Z _0o Z _0e ) always holds, the internal structure is preferably set so that the characteristic impedance Z ₀ is 50Ω.

When the phase difference between the first inner conductor 7 and the second inner conductor 8 is 180 ° and the voltages are the same (odd mode power supply), the characteristic impedance to be formed is Z _0o . Then, the first inner conductor 7 and the second inner conductor 8
When the phase difference between them is the same and the magnitude of the voltage is the same (even mode power supply), the characteristic impedance is _defined as Z _0e . According to the present invention, the geometrical average value Z ₀ = √ (Z _0o Z _0e ) of these characteristic impedances Z _0o and Z _0e is calculated based on the values of the connectors 10, 11, 12, and 1 attached to the outer conductors on both sides.
3 was implemented to have the same value as the characteristic impedance (normally 50Ω).

The coaxial connector connection section 3 has one end in addition to the first to fourth connectors 10, 11, 12, 13 and the first external conductor 6, and one end at the first to fourth connectors 10, 11, 1, 1.
2 and 13 and a third inner conductor 9 connected at the other end to ends of the first and second inner conductors 7 and 8. The inside of the third internal conductor 9 is filled with a non-conductive dielectric 21 such as Teflon having a low dielectric constant so that the first and second internal conductors 7 and 8 can be fixed. All of these structures should be designed so that impedance matching is maintained.

The tapered region 2 is a region having a taper in order to maintain the size of the device region 1 under test. The cross-sectional shape is the same as that of the device region 1. It has a tapered structure that becomes gradually narrower as it goes to the part 3 side.

Such a tapered structure has a very close relationship with the usable frequency together with the structure of the DUT region 1, and the smaller the size and the length of the tapered region 2, the smaller the space of the DUT. Becomes smaller, but the range of applied frequencies becomes wider. Therefore, in such a tapered region, an appropriate size should be maintained and the effective length should be reduced.

On the other hand, if the taper length increases, the effective length increases and the resonance frequency decreases. Therefore, the taper region 2 should be kept as short as possible without causing electromagnetic wave distortion.

In this embodiment, the tapered region 2 connected to the coaxial connector connecting portion 3 and the test object region 1 are connected to each other so that impedance matching can be performed most appropriately within an allowable limit. The taper region 2 has a structure in which the inclination with respect to the maximum width is 45 °. The test object region 1, the tapered region 2, and the coaxial connector connection portion 3 are assembled and connected by a spiral so that they can be separated and manufactured.

On the other hand, in another embodiment of the present invention, FIG.
FIG. 9 to FIG. 9 present a linear coupled transmission line cell structure for calibrating an electromagnetic field probe. The configuration of the present embodiment is the same as the configuration of the above-described embodiment of FIGS. 2 to 5 as illustrated, but the central portion of one of the first outer conductors 6 of the coaxial connector connection portion 3 is shown. The first probe hole 19a penetrates through to the center outer conductor 4 and is large enough to allow the electromagnetic field probe to enter, so that the position where the electromagnetic field probe is placed horizontally with respect to the direction in which radio waves travel can be calibrated. Like that.

At this time, the first hole 19a is connected to the hollow tube 19 whose length is longer than the radius in order to facilitate observation of the electromagnetic field probe and the internal measurement object. Also,
It is mounted on one surface of the central outer conductor 4 of the DUT region 1 so as to be located in a direction perpendicular to the first probe hole 19a, and a second hole 20a is formed at the center thereof so as to penetrate. Door 20 is provided. Therefore, in this embodiment, the electromagnetic field probe can be calibrated in all directions.

Here, the first and second probe holes 19 are formed.
a, 20a keep their radii less than the depth of the hole and minimize electromagnetic wave leakage based on the waveguide principle. Also, the first and second probe holes 1 inside
Positions 9a and 20a are areas where the electromagnetic field keeps the minimum value.
This is a position where electromagnetic wave leakage hardly occurs during the electromagnetic field probe test. Moreover, the coupled transmission line cell has two first and second inner conductors 7 and 8 located inside,
Since the magnitude of the first cutoff frequency (TE ₁₀ mode) is generated in a band approximately 1.4 times higher than that of the existing symmetric and asymmetric TEM cells, the band is higher than that of the existing TEM cell for electromagnetic field probe calibration. Can be used up to.

As described in the present invention, in order to measure electromagnetic interference and electromagnetic wave immunity, and to perform tests such as probe calibration, it is very important to maintain uniformity higher than each frequency band in the test object region 1 first. Is important.

The standing wave ratio (VSWR) and uniformity evaluation results measured for the existing coupled transmission line cell and the model directly produced for the linear coupled transmission line cell according to the present invention are shown in FIGS. As shown in FIG.

The conventional coupled transmission line cell shown in FIG. 10 has such characteristics that the standing wave ratio is high and the impedance matching is poor in a frequency window between 149 MHz and 200 MHz. This indicates a phenomenon caused by multiple point reflection at the end of the tapered region as described in the section of the prior art in this specification. The linear coupled transmission line cell according to the present invention shown in FIG. 11 has a frequency window between 198 MHz and 255 MHz,
This indicates that the standing wave ratio has a low value. This indicates that the impedance matching is correctly performed. Therefore, in the above-mentioned band, it is possible to measure the electromagnetic wave interference and the electromagnetic wave resistance in a band excluding only the frequency at which resonance appears.

Further, it can be seen that the linear coupling transmission line cell of the present invention shown in FIG. 13 has much improved electric field uniformity as compared with the conventional coupling transmission line cell shown in FIG. The measurement points in FIGS. 12 and 13 are based on the international standard CIS.
This is a result measured in a 1/3 center region as a uniform field region required by PR and EN. The conventional coupled transmission line cell uses a 9-point measurement method, and the present invention uses a 12-point measurement method. Show.

The present invention described above is not limited by the above-described embodiments and the accompanying drawings, and various substitutions, modifications, and changes can be made without departing from the technical idea of the present invention. Some will be apparent to those of ordinary skill in the art to which this invention pertains.

As described above, according to the present invention, the first and second inner conductors are formed in a linear shape, and the electromagnetic wave distortion phenomenon caused by the angular wave caused by the bending of the inner conductor of the conventional coupled transmission line cell is reduced. By removing, the effect of increasing the uniformity of the electromagnetic wave, enabling accurate measurement of electromagnetic wave resistance and electromagnetic wave interference, and measurement of electromagnetic field probe calibration is achieved. In addition, since the first and second inner conductors do not have horizontal bending, they can be manufactured easily and can be manufactured precisely, and a frequency window between resonance frequencies can be utilized. Has broadband frequency characteristics compared to existing facilities. In addition, the linear coupling transmission line cell of the present invention has the first cut-off frequency (TE ₁₀ mode) of about 1.4 times higher than the existing TEM cell by arranging two inner conductors. In the case of utilizing it to produce an electromagnetic field probe calibration, there is an effect that a higher band can be used than an existing electromagnetic probe TEM cell of the same size.

[0043]

As described above, in the present invention, the upper and lower inner conductors in the coupled transmission line are provided in parallel so as not to bend horizontally, and the power supply terminals are separated by a predetermined distance. By providing such a circuit, it is possible to provide a linear coupling transmission line cell that can easily realize impedance matching, eliminate multiple reflections, generate a frequency window with a large Q, and widen the frequency band used.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing a configuration of a conventional coupled transmission line cell.

FIG. 2 is a perspective view schematically showing a linear configuration for EMI / EMC measurement according to an embodiment of the present invention.

FIG. 3 is a cross-sectional view of the coupled transmission line cell of FIG.

FIG. 4 is a sectional view taken along line AA ′ of the coupled transmission line cell of FIG. 3;

FIG. 5 is a sectional view of the coupled transmission line cell taken along line BB ′ of FIG. 4;

FIG. 6 is a perspective view showing a configuration of a linear coupling transmission line cell for electromagnetic field probe calibration according to another embodiment of the present invention.

FIG. 7 is a cross-sectional view of the coupled transmission line cell of FIG.

FIG. 8 is a cross-sectional view taken along the line CC ′ of the coupled transmission line cell of FIG. 7;

FIG. 9 is a sectional view taken along the line DD ′ of the coupled transmission line cell of FIG. 7;

FIG. 10 is a graph showing a standing wave of a coupled transmission line cell according to the related art.

FIG. 11 is a graph showing standing waves of the EMI / EMC measurement linear coupling transmission line cell according to the present embodiment.

FIG. 12 is a graph showing the evaluation results of the uniformity of each frequency of the coupled transmission line cell according to the related art.

FIG. 13 is a graph showing the evaluation results of the uniformity of each frequency of the linear coupled transmission line cell for EMI / EMC measurement according to the present embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 DUT area | region 2 Tapered area | region 3 Coaxial connector connection part 4 Center outer conductor 5 2nd outer conductor 6 1st outer conductor 7 1st inner conductor 8 2nd inner conductor 9 3rd inner conductor 10 1st connector 11th 2 Connector 12 Third Connector 13 Fourth Connector 14 Support 15, 20 Door 16 Shielding Window 17 First Internal Conductor Support 18 Second Internal Conductor Support 19 Hollow Tube 21 Dielectric

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI Theme coat ゛ (Reference)

Claims (9)

[Claims] An internal space for positioning a device under test is formed therein, and a tapered portion integrally connected to both sides of a central portion and both side ends of the tapered portion are cut off. An outer conductor having an end portion formed opposite to the first end portion, and a first and a second portion provided at upper and lower positions of one end portion of the outer conductor and arranged so as to have a predetermined distance therebetween. 2 connector means, 3rd and 4th connector means provided at the upper and lower positions of the other end of the outer conductor and arranged so as to have a predetermined separation distance therebetween, and to be separated from the outer conductor An upper first internal conductor plate, which is provided in the internal space thereof and is located in line with the first and third connector means, and is located in line with the second and fourth connector means, and 1 Opposed to the internal conductor plate An inner conductor comprising a lower second inner conductor plate forming a parallel surface; an inner conductor supporting means for fixing the inner conductor to the inside of the outer conductor; Prepared for
Opening / closing means having an electromagnetic wave shielding window of a predetermined size for observing a state of the device under test. 2. The linear coupled transmission line cell according to claim 1, further comprising a hollow tube provided at the one end of the outer conductor and communicating with the inside of the outer conductor. 3. The outer conductor includes a central portion having opposing upper / lower surfaces and front / rear surfaces forming a quadrangular cylindrical shape, and is coupled to both sides of the central portion. Are formed so that the taper angle of the front and rear surfaces is larger than the tapered angle of the upper and lower surfaces, and provided at the ends of the left and right taper portions. 3. The method according to claim 1, further comprising the left and right ends.
A linear coupled transmission line cell as described. 4. The linear coupled transmission line according to claim 1, further comprising a supporting means installed upright on the inner upper and lower surfaces of the outer conductor and supporting the inner conductor. cell. 5. The width of the first and second inner conductor plates in the inner space is set close to upper and lower surfaces of the inner wall of the outer conductor, as long as electromagnetic waves are not discarded on the side wall of the outer conductor. 3. The linear coupled transmission line cell according to claim 1, wherein 6. The first and second inner conductor plates in the inner space have opposite phases to the connector means located at the one end of the outer conductor, and have the same magnitude. 3. The linear coupled transmission line cell according to claim 1, wherein a characteristic impedance formed when a voltage is supplied has a characteristic impedance of the connected connector means. 7. An opposite phase to said connector means located at said one end of said outer conductor, and
_Let Z _0o be the characteristic impedance formed when supplying the same magnitude of applied voltage, and apply the same magnitude and the same magnitude to the connector means located at the one end of the outer conductor. The characteristic impedance formed when supplying a voltage is represented by Z _0e, and the geometric average value √ (Z _0o Z _0e ) is the same value as the characteristic impedance of the connector means. Item 3. A linear coupled transmission line cell according to Item 2. 8. A first electrode penetrating from the center of the end portion of the outer conductor, on which the connector means is arranged, to the inner space side so that the electromagnetic field probe can be calibrated.
3. The linear type according to claim 1, further comprising a hole, and a door mounted on one surface of the outer conductor in the central portion and having a second hole penetrating the central portion. Coupled transmission line cell. 9. The tapered portion connected to the connector means has a tapered structure that gradually tapers toward the connector means so that impedance matching is performed most appropriately within an allowable limit. 3. The linear coupled transmission line cell according to claim 1, wherein an inclination between a minimum width and a maximum width of the tapered portion connected to the central portion is 45 degrees.