JP2006038759A - Radio wave absorption characteristic measuring instrument and its method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To continuously measure radio wave absorption characteristics over a wide range of frequency band including a frequency band of 1 GHz or less by using one instrument, to dispense with a large measuring object, in particular, and further, to perform radio wave absorption characteristic measurement with a simplified instrument and signal processing. <P>SOLUTION: A radio wave inputted from an opening 1 by a signal generator 11 is divided into two with opposite phases, respectively, by a magic tee 12, and two radio waves obtained by the two-dividing are outputted through openings 2 and 3, respectively, in the magic tee 12. Further, the outputted radio waves are reflected by a metallic plate 30 that closes an end part of a waveguide 21 connected to the opening 2 in the magic tee 12 and by a measuring object 40 that closes an end part of a waveguide 22 connected to the opening 3, respectively. A mixed radio wave of two reflected radio waves severally returned to the openings 2 and 3 by the reflection, is outputted through an opening 4, and the outputted radio wave is measured by means of a signal receiver 14. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a radio wave absorption characteristic measuring apparatus and method for measuring a radio wave absorption characteristic of a measurement object.

As wireless communication devices such as mobile phones, wireless LANs, and ETCs (automatic toll collection systems) become widespread and the use of radio waves spreads, the demand for radio wave absorbers has increased. In connection with this, development of the technique which measures the radio wave absorption characteristic of a radio wave absorber efficiently is desired.
Non-Patent Document 1 (especially, pages 6 to 7) and the like show that there are methods shown in the following (a) to (d) as conventional methods for measuring (evaluating) radio wave absorption characteristics.
(A) Method of paying attention to the Q value This is because the Q value is measured for each of the case where the measurement object (absorbing material) is not placed and the case where the measurement object is placed in the housing, and the difference between the Q values is noticed. It evaluates (measures) the degree of radio wave absorption of the measurement object.
(B) Method focusing attention on input / output characteristics This is the case of the input / output characteristics of radio waves (electromagnetic fields) with respect to the inside of the case (the amount of power attenuation) for each of the cases where the measurement object is not placed in the case and the case where it is placed. ) And the radio wave absorption degree of the measurement object is evaluated from the difference between the input and output characteristics of the two.
(C) Method focusing attention on coupling characteristics This is basically the same principle as in (b) above, except that a minute loop antenna for input and output of radio waves is provided in place of the housing, and the minute loop is provided. Measure the input / output characteristics of the micro-loop antenna, which varies depending on the coupling characteristics of both micro-loop antennas, and evaluate the degree of radio wave absorption of the object to be measured, with and without the measurement object placed close to the antenna. Is.
(D) Method of paying attention to transmission characteristics This is because of the transmission characteristics (passage characteristics of high-frequency signals) in the strip line when the measurement object is not provided between the strip line conductor and the ground plane conductor. The degree of radio wave absorption of the measurement object is evaluated from the change.
Supervised by Osamu Hashimoto, “Technology and Application Development of Next-Generation Wave Absorber” (Electronic Materials and Technology Series), CMC Publishing, published in March 2003

However, in the above (A) “Method focusing on the Q value”, the absorption characteristic can be measured for the radio wave in the resonance frequency band of the housing accommodating the measurement object, but the Q value is obtained for the radio wave in other frequency bands. Therefore, it is impossible to measure the radio wave absorption characteristics continuously over a wide frequency band with a single device.
Similarly, in (B) “Method focusing on input / output characteristics”, the radio wave in the resonance frequency band of the casing has a large energy accumulated in the casing and a small output power. It is possible to detect a change in output power due to a relatively high resolution. However, for radio waves outside the resonance frequency band of the housing, the energy stored in the housing is reduced and the output power is increased. The evaluation accuracy of characteristics deteriorates. For this reason, there has been a problem that it is impossible to measure the radio wave absorption characteristics continuously over a wide frequency band with a single device.
In (C) “Method focusing on coupling characteristics”, the propagation state of the radio wave between the two minute loop antennas changes depending on the presence or absence of the measurement object. There is a problem that the signal processing for evaluating the radio wave absorption characteristic becomes complicated because the signal difference cannot be evaluated simply by comparing the signal differences.
Further, the above (D) “Method focusing on transmission characteristics” has a problem that a large measurement object (sample) is required for radio waves of 1 GHz or less. In addition, in the case of a measurement object in which a radio wave absorber film is formed on the surface of a metal member, the metal member approaches the strip line between the strip line conductor and the ground plane conductor in the strip line. Since the signal propagation mode changes, there is a problem that measurement becomes difficult.
Accordingly, the present invention has been made in view of the above circumstances, and its object is to continuously measure radio wave absorption characteristics over a wide frequency band including a frequency band of 1 GHz or less with one apparatus. An object of the present invention is to provide a radio wave absorption characteristic measuring apparatus and method that do not require a particularly large measurement object and that are simple in apparatus and signal processing.

In order to achieve the above-described object, the present invention provides two openings (second outputs) each of which outputs a radio wave input from one opening (first opening) of a magic tee having four openings in opposite phases. (Aperture and Third Aperture) Each of them is applied as an apparatus for measuring the radio wave absorption characteristics of a measurement object with a simple configuration in which a waveguide is provided, and a measurement method thereof.
That is, by inputting a radio wave from the magicty signal input opening (first opening), the radio wave is split into two in opposite phases by the function of the magic tee, and each of the branched radio waves is Output is made to the waveguide connected to the opening (first waveguide) and the waveguide connected to the third opening (second waveguide). As a result, the output radio wave is reflected and returned to each of the radio wave reflecting member and the member having the object to be measured, which block one of the waveguides (the side opposite to the connection end with the magic tee). (Reflected and input to each of the second opening and the third opening). Then, since the combined radio wave of the two reflected radio waves that has returned is output to the fourth opening by the function of the magic tee, the output synthetic radio wave is received and measured. Here, the member having the measurement object includes the measurement object itself and a member provided with the measurement object (such as a measurement object disposed on the surface of a radio wave reflection member).
Such measurement does not depend on the resonance of the housing that houses the object to be measured, nor does it use a strip line, so that radio waves in the frequency band that can be transmitted by Magicty and waveguides are used. , One device can continuously measure radio wave absorption characteristics over a wide frequency band including a frequency band of 1 GHz or less.
Moreover, it is sufficient to prepare a measurement object having a size enough to block one of the waveguides or less, and a particularly large measurement object is not required.
Further, the apparatus is simple, and the signal level (also referred to as amplitude or power) of the synthesized radio wave is the same as that of the two radio waves before synthesis. This represents the difference in the amount of radio wave absorption between the reflecting member (metal plate, etc.) and the measurement object, and the radio wave absorption characteristics of the measurement object can be evaluated by very simple signal processing.
Here, if the radio wave input to the magic tee is generated by frequency sweep, the frequency characteristic of radio wave absorption of the measurement object can be easily measured.
Further, when a member having the measurement object that closes one of the waveguides (second waveguide) is replaced with the radio wave reflecting member (that is, both the two waveguides are closed with the reflecting member). The signal level of the synthetic radio wave output from the fourth opening of the magic tee is substantially zero. That is, the two reflected radio waves before the synthesis of the synthesized radio waves are in opposite phases.
As a result, the signal level (also referred to as amplitude or power) of the synthetic radio wave when the object to be measured is provided on one side of the waveguide and the reflection member is provided on the other is the reflection member (metal plate or the like). Approximates the total reflection of the radio wave, it directly represents the radio wave absorption of the measurement object.
For example, the dimension from the opening (second opening) to the reflecting member in one of the two waveguides (first waveguide) and the opening (first in the other (second waveguide) If the dimensions from the aperture 3) to the measurement object are substantially the same, the signal level of the synthesized radio wave represents the radio wave absorption amount of the measurement object itself.

Further, if a mechanism (member moving means) for moving the position of the reflecting member or the position of the measurement object in the waveguide (first waveguide or second waveguide) is provided, it is more versatile. Measurement is possible.
For example, it is possible to perform pre-calibration so that the signal level of the combined radio wave is substantially zero in a state where the reflection member is provided in both of the two waveguides.
As a measurement procedure in that case, first, the opposite side of each of the two waveguides (the first waveguide and the second waveguide) with respect to the connection end with the magic tee was closed with the reflecting member. In one state, radio waves are input to the first opening of the magic tee so that the level of the synthesized radio wave output from the fourth opening of the magic tee is approximately zero. The position of the reflecting member in the wave tube (first waveguide) is adjusted (preliminary calibration).
Next, the reflecting member in the other waveguide (second waveguide) is replaced with an object to be measured from the state adjusted as described above, and in this state, radio waves are transmitted to the first of the magic tee. Input to the opening. Furthermore, the level of the synthetic radio wave output from the fourth opening of the magic tee may be measured thereby, and the radio wave absorption characteristic of the measurement object may be evaluated based on the measurement result.
As another example, the opposite side of each of the two waveguides (the first waveguide and the second waveguide) with respect to the connection end with the magic tee is the reflection member and the measurement object. The radio wave is input to the first opening of the magic tee in a state where it is blocked by a member having a shape, and one or both of the position of the reflecting member and the position of the member having the measurement object in each of the waveguides is set. It is also conceivable to sequentially move, thereby measuring the level of the synthetic radio wave output from the fourth opening of the magic tee, and evaluating the radio wave absorption characteristics of the measurement object based on the measurement result.
In addition, if the radio wave input to the first opening of the magic tee is generated by frequency sweep, the radio wave absorption characteristics can be continuously measured over a desired frequency band.

  According to the present invention, a simple device including a magic tee and a waveguide connected to the magic tee absorbs radio waves continuously over a wide frequency band including a frequency band of 1 GHz or less. Characteristic can be measured, and no large measuring object is required. Further, the signal level of the synthesized radio wave output from the magic tee, that is, the signal level of the synthesized radio wave of the reflected radio wave with respect to the reflecting member of the radio wave and the reflected radio wave with respect to the measurement object corresponds to the radio wave absorption amount of the measurement object. Because it is a level, the radio wave absorption characteristics can be evaluated with simple signal processing.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings so that the present invention can be understood. The following embodiment is an example embodying the present invention, and does not limit the technical scope of the present invention.
FIG. 1 is a diagram showing a schematic configuration of the radio wave absorption characteristic measuring device X1 according to the first embodiment of the present invention, and FIG. 2 is a schematic configuration of the radio wave absorption characteristic measuring device X2 according to the second embodiment of the present invention. FIG. 3 is a perspective view of the magic tee.

(First embodiment)
First, a radio wave absorption characteristic measuring apparatus X1 (hereinafter referred to as measuring apparatus X1) according to a first embodiment of the present invention will be described with reference to FIG.
As shown in FIG. 1, the measuring apparatus X1 includes a signal generator 11 that generates radio waves (high-frequency signals), a magic tee 12, a signal receiver 13 that receives radio waves, and two connected to the magic tee 12. Waveguides 21 and 22 are provided.
The signal generator 11 is capable of generating radio waves by continuously changing the frequency by frequency sweeping (an example of radio wave generating means).
A perspective view of the magic tee 3 is shown in FIG.
The magic tee 3 has four openings (1 to 4), and the radio wave input from the opening (1) is bifurcated in opposite phases and is output to each of the opening (2) and the opening (3). Further, when radio waves are input from the opening (2) and the opening (3), the synthesized radio wave is output to the opening (4).

Returning to FIG. 1, the waveguide 21 (first waveguide) is connected to the opening (2) in the magic tee 12, and the metal plate 30 whose opposite side to the connection end is a radio wave reflection member. It is blocked by
In addition, the waveguide 22 (second waveguide) is connected to the opening (3) in the magic tee 12, and the opposite side to the connection end is closed by the measurement object 40 having radio wave absorption characteristics. Yes. The waveguide 22 is configured so that the measurement object 40 can be attached and detached. Instead of the measurement object 40, the metal plate 30 which is a radio wave reflection member can be attached.
With such a configuration, in the magic tee 12, the radio wave input from the aperture (1) by the signal generator 11 is bifurcated in opposite phases, and each of the bifurcated radio waves is separated into the aperture (2) and the aperture. Output to each of (3). Further, the output radio wave is reflected to the outside of the magic tee 12, that is, to each of the measurement object 40 that closes the end of the waveguide 22 and the metal plate 30 that closes the end of the waveguide 21. Then, a combined radio wave of both reflected radio waves input (returned) to each of the aperture (2) and the aperture (3) by the reflection is output to the aperture (4).

The signal receiver 13 is a radio wave measuring unit that receives the synthesized radio wave output from the opening (4) in the magic tee 12 and measures the reception level (reception power). The reception level of the synthesized radio wave measured by the signal receiver 13 is input to a computer or the like (not shown), and processing for converting the reception level into the radio wave absorption amount of the measurement object by the computer or the like, that is, radio wave Absorption characteristics are evaluated.
Here, the two waveguides 21 and 22 are made of the same material with the same dimensions (the same length), and their end portions (end portions opposite to the connection end with the magic tee 12). The metal plate 30 and the measurement object 40 are provided on the substrate. That is, the dimension from the opening (2) to the metal plate 30 in one of the two waveguides (21, first waveguide) and the opening in the other (22, second waveguide) The dimensions from (3) to the measurement object 40 are the same.
As a result, in the magic tee 12, radio waves that are input from the opening (1), branched into two and output to the opening (2) and the opening (3) in opposite phases are respectively transmitted to the metal plate 30. And the object to be measured 40 and when they return to the openings (1) and (3), they are configured to maintain mutually opposite phases.
Therefore, when the measurement object 40 that closes the waveguide 22 (second waveguide) is replaced with the metal plate 40 (reflection member), the output from the opening (4) of the magic tee 12 is performed. The signal level of the synthesized radio wave is 0 (zero).
Therefore, in a state where the metal plate 30 is provided at the end of the waveguide 21 and the measurement object 40 is provided at the end of the waveguide 22 (the state shown in FIG. 1), the signal receiver 13 Since the signal level of the synthetic radio wave to be measured can be approximated to that the metal plate 30 totally reflects the radio wave, it directly represents the amount of radio wave absorption of the measurement object 40, which is very simple signal processing. The radio wave absorption characteristics of the measurement object 40 can be evaluated. .
Although it is preferable in terms of measurement accuracy that the signal level is completely “0”, it is not necessary to set it to “0” as long as it does not greatly affect the measurement result. 0).

Further, since the measuring device X1 does not depend on the resonance of the housing that accommodates the measurement object 40 and does not use a strip line, the magic tee 12 and the waveguides 21 and 22 are used. As long as it is a radio wave in a frequency band that can be transmitted, it is possible to measure the radio wave absorption characteristics continuously over a wide frequency band including a frequency band of 1 GHz or less with one measuring device X1.
Further, it is sufficient to prepare a measuring object 40 that is large enough to block one of the waveguides 22 or smaller, and does not require a particularly large object to be measured.
Further, if the frequency of the generated radio wave is changed continuously (in multiple steps) by the signal generator 11 and the frequency of the generated radio wave is changed, the frequency characteristics of radio wave absorption of the measurement object 40 can be easily measured.

(Second Embodiment)
Next, a radio wave absorption characteristic measurement device X2 (hereinafter referred to as measurement device X2) according to a second embodiment of the present invention will be described with reference to FIG.
In addition to the configuration of the measurement device X1, the measurement device X2 has one waveguide 21 (first waveguide) in which the position of the metal plate 30 (reflection member) in the waveguide 21 is changed. A slide mechanism 50 (an example of a reflecting member moving means) that moves in the longitudinal direction of the waveguide 21 is provided.
Hereinafter, a procedure for measuring the radio wave absorption characteristics using the measuring device X2 will be described.
<Adjustment process>
First, the state opposite to the connection end with the magic tee 12 in both the waveguides 21 and 22 is closed with the metal plate 40 (reflecting member) (the measurement object 40 in FIG. In the replaced state), the signal generator 11 inputs radio waves to the opening (1) of the magic tee 12.
Then, the longitudinal direction of the waveguide 21 (first waveguide) is caused by the slide mechanism 50 so that the level of the synthetic radio wave output from the opening (4) of the magic tee 12 becomes zero. The position of the metal plate 30 is adjusted.

<Measurement process>
Next, the metal plate provided at the end of the waveguide 22 (second waveguide) from the state adjusted by the adjusting step (the state in which the slide mechanism 50 is positioned). 40 is replaced with the measurement object 40, and in this state, the signal generator 11 inputs radio waves to the opening (1) of the magic tee 12.
Thus, the level of the synthetic radio wave output from the opening (4) of the magic tee 12 is measured by the signal receiver 13, and the radio wave absorption characteristic of the measurement object 40 is evaluated based on the measurement result. .
Thereby, it is possible to prevent a measurement error from occurring due to a difference in the opposite phase state of the reflected radio waves returning to each of the openings (2) and (3) due to a difference in the shape of the measurement object 40, an attachment error, and the like. .
Further, for example, when the amount of radio wave absorption of the measurement object 40 is small, the measurement object 40 is disposed on the end portion of the waveguide 22 and the side wall portion inside thereof as shown in FIG. For example, the amount of radio wave absorption can be increased and the measurement sensitivity can be increased. However, in this case, the substantial internal dimension in the waveguide 22 is different from the internal dimension of the waveguide 21. In such a case, the adjustment process described above is performed in a state in which a metal member having the same shape (same size) as the measurement object 40 is provided on the end portion of the waveguide 22 and the inner side wall portion thereof. If so, the phase of the reflected radio wave returning to each of the apertures (2) and (3) can be adjusted, and measurement errors can be prevented from occurring.

It is also conceivable to perform measurement by sequentially moving the position of the metal plate 30 in the waveguide 21.
That is, in the state where the opposite side of each of the two waveguides 21 and 22 with respect to the connection end with the magic tee is closed with the metal plate 30 (reflecting member) and the measurement object 40, the signal generator 11 A radio wave is input to the opening (1) of the magic tee 12, and the metal plate 30 in the waveguide 21 is sequentially moved by the slide mechanism 50, whereby the opening (4) of the magic tee 12 is moved. Is measured by the signal receiver 13 and the radio wave absorption characteristic of the measuring object 40 is evaluated based on the measurement result.
In this case, for example, with respect to the level of the synthetic wave radio wave obtained when the metal plate 30 is sequentially moved, it is conceivable to evaluate the radio wave absorption characteristic using the minimum level, the average level, or the like.
In the second embodiment shown in FIG. 2, the slide mechanism 50 that can move the position of the metal plate 30 in the waveguide 21 is provided. Instead, the same configuration is provided in the waveguide. It is also possible to provide a mechanism that enables the position of the measurement object 40 in the tube 22 to be moved. Further, a configuration in which the slide mechanism 50 is provided in both the waveguides 21 and 22 is also conceivable.

  The present invention can be used for a radio wave absorption characteristic measuring apparatus.

The figure showing the schematic structure of the electromagnetic wave absorption characteristic measuring apparatus X1 which concerns on 1st Embodiment of this invention. The figure showing schematic structure of the electromagnetic wave absorption characteristic measuring apparatus X2 which concerns on 2nd Embodiment of this invention. FIG.

Explanation of symbols

X1, X2 ... Radio wave absorption characteristic measuring devices 1 to 4 ... Magicty opening 11 ... Signal generator 12 ... Magicty 13 ... Signal receivers 21 and 22 ... Waveguide 30 ... Metal plate (radio wave reflection member)
40 ... Measurement object (electromagnetic wave absorber)
50 ... Slide mechanism

Claims (8)

It has four apertures. The radio wave input from the first aperture by the radio wave generation means is bifurcated in opposite phase and output to each of the second aperture and the third aperture, and the output radio wave is reflected outside. A magic tee for outputting a combined radio wave of both reflected radio waves input to each of the second aperture and the third aperture to the fourth aperture;
A first waveguide that is connected to the second opening in the magic tee and whose opposite side to the connection end is blocked by the radio wave reflecting member;
A second waveguide that is connected to the third opening in the magic tee and whose side opposite to the connection end is closed by a member having a measurement object of radio wave absorption characteristics;
Comprising
A radio wave absorption characteristic measuring apparatus, wherein the radio wave absorption characteristic of the measurement object is measured based on the synthetic radio wave output from the fourth opening in the magic tee.   The radio wave absorption characteristic measuring apparatus according to claim 1, wherein the radio wave generating means generates radio waves by frequency sweeping.   When the member having the measurement object that closes the second waveguide is replaced with the reflecting member, the signal level of the synthetic radio wave output from the fourth opening of the magic tee is approximately zero. The radio wave absorption characteristic measuring apparatus according to claim 1 or 2.   The dimension from the second opening to the reflecting member in the first waveguide is substantially the same as the dimension from the third opening to the measurement object in the second waveguide. The radio wave absorption characteristic measuring apparatus according to any one of 1 to 3.   5. The apparatus according to claim 1, further comprising a member moving unit that moves a position of the reflecting member in the first waveguide and / or a position of the measurement object in the second waveguide. The radio wave absorption characteristic measuring device described. 4 openings are provided, the radio waves input from the first opening are bifurcated in opposite phases and output to the second opening and the third opening, respectively, and the output radio waves are reflected outside and the first A magic tee that outputs a combined radio wave of both reflected radio waves input to each of the second aperture and the third aperture to the fourth aperture, and is connected to each of the second aperture and the third aperture in the magic tee. A radio wave absorption characteristic measuring method for measuring a radio wave absorption characteristic of an object to be measured using a first waveguide and a second waveguide,
A radio wave is input to the first opening of the magic tee in a state where the opposite side of the first waveguide and the second waveguide with respect to the connection end with the magic tee is covered with the radio wave reflecting member. As a result, the position of the reflecting member in the first waveguide and / or the second guide is set so that the level of the synthetic radio wave output from the fourth opening of the magic tee becomes substantially zero. An adjusting step of adjusting the position of the reflecting member in the wave tube;
The radio wave is input to the first opening of the magic tee in a state where the reflecting member in the second waveguide is replaced with a member having the measurement object from the state adjusted by the adjusting step. A measurement step of evaluating the radio wave absorption characteristics of the measurement object based on the result of measuring the level of the synthetic radio wave output from the fourth opening of the magic tee,
A method for measuring radio wave absorption characteristics, comprising: 4 openings are provided, the radio waves input from the first opening are bifurcated in opposite phases and output to the second opening and the third opening, respectively, and the output radio waves are reflected outside and the first A magic tee that outputs a combined radio wave of both reflected radio waves input to each of the second aperture and the third aperture to the fourth aperture, and is connected to each of the second aperture and the third aperture in the magic tee. A radio wave absorption characteristic measuring method for measuring a radio wave absorption characteristic of an object to be measured using a first waveguide and a second waveguide,
In each of the first waveguide and the second waveguide, the side opposite to the connection end with the magic tee is covered with the radio wave reflecting member and the member having the measurement object, and the radio wave is transmitted. And the position of the reflecting member in the first waveguide and / or the position of the reflecting member in the second waveguide are sequentially moved, thereby the magic. A radio wave absorption characteristic measuring method comprising: evaluating a radio wave absorption characteristic of the measurement object based on a result of measuring a level of the synthetic radio wave output from the fourth opening of the tee.   The radio wave absorption characteristic measuring method according to claim 6 or 7, wherein the radio wave input to the first opening of the magic tee is generated by a frequency sweep.

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