JP2009052990A - Electromagnetic field measurement apparatus, measurement system, and electromagnetic field measurement method - Google Patents

Abstract

In an apparatus for three-dimensionally measuring an electromagnetic wave radiated from an electronic device, the measurement time becomes enormous with a single antenna, and the measurement accuracy deteriorates due to interference between antennas in simultaneous measurement using a plurality of antennas. .
A plurality of directional antennas (14a, 14b) for receiving electromagnetic waves radiated from a device under test (11) with a maximum sensitivity direction directed toward the device under test (11), and a device under test of the plurality of directional antennas (14a, 14b). Movable parts 20a and 20b that can change relative positions with respect to the object 11 are provided. The movable parts 20a and 20b can receive the electromagnetic waves radiated from the DUT 11 without being affected by the electromagnetic waves re-radiated by the other directional antennas 14b that have received the electromagnetic waves. The relative position with respect to the DUT 11 is changed so as to be in a position (a position that does not enter the region 35b having a predetermined beam width of the other directional antenna 14b).
[Selection] Figure 1

Description

  The present invention relates to an electromagnetic field measurement apparatus, a measurement system, and an electromagnetic field measurement method for measuring an electromagnetic wave radiated from an electronic device.

  In recent years, electronic devices have been reduced in size, increased in functionality, and digitized, and accordingly, the level of electromagnetic waves radiated from the electronic devices has increased, and countermeasures against unnecessary radiation have become difficult. In addition, the number of electronic devices that transmit and receive electromagnetic waves, such as telephones, TVs, and wireless LANs, has increased, and the need to measure the state of electromagnetic fields around electronic devices has increased.

  For measurement of electromagnetic waves radiated from electronic equipment, in the case of unnecessary radiation, a device that measures the far field in an electromagnetic anechoic chamber or open site and the electromagnetic field distribution near the electronic equipment or printed circuit board is used. In the wireless apparatus, the above-described electromagnetic anechoic chamber, electromagnetic field distribution measuring apparatus, and apparatus for measuring the distribution by changing the measurement position three-dimensionally are used. In particular, an apparatus for measuring a distribution by changing a measurement position three-dimensionally has a growing need for use in unnecessary radiation analysis as a measurement apparatus that complements between the characteristics of a far electromagnetic wave darkroom from the vicinity of an electronic device.

  A conventional example of an apparatus for measuring by changing the measurement position three-dimensionally will be described with reference to FIGS.

  FIG. 9 is a configuration diagram schematically showing a first conventional electromagnetic field measuring apparatus.

  In FIG. 9, a device under test 11 for measuring radiated electromagnetic waves is placed on a turntable 12 that rotates the device under test 11. An antenna 14 for measuring an electromagnetic wave radiated from the object to be measured 11 is arranged on a semicircular guide 33 having the center of the object to be measured 11 as an origin, and the movable unit 20 uses the antenna 14 as a guide 33. Move along.

  In the electromagnetic field measuring apparatus having such a configuration, the antenna 14 moves along the circumferential guide 33 while facing the center of the object to be measured 11, and the object to be measured 11 is rotated by the turntable 12 to be measured. Measurement is possible at an arbitrary position on the hemispherical surface with the object 11 as the center.

  Then, from the measurement results measured at a plurality of measurement positions, the distribution of the electromagnetic field radiated from the DUT 11 can be represented by a hemisphere on polar coordinates as shown in FIG. In addition, the dark part of FIG. 10 has shown the part with strong electromagnetic field intensity | strength.

  There is also an electromagnetic field measurement device that measures the electromagnetic field distribution on the surface of a rectangular parallelepiped around the object to be measured (see, for example, Patent Document 1).

  FIG. 11 is a configuration diagram schematically showing a second conventional electromagnetic field measuring apparatus for measuring the electromagnetic field distribution on a rectangular parallelepiped space around the object to be measured.

  In FIG. 11, reference numeral 13 denotes an object to be measured for measuring radiated electromagnetic waves, 15 denotes a turntable for rotating the object to be measured 13, 16 denotes an antenna for measuring electromagnetic waves radiated from the object to be measured 13, and 21 denotes an antenna 16. A stay to be fixed, 22 is an antenna mast that holds the height of the antenna 16, 23 is a movable part that moves the stay 21 in the Y-axis direction, and 24 is a position in the Z-axis direction by mounting the movable part 23 on the antenna mast 22. , A movable part 26 for moving the antenna mast 22 in the X-axis direction, and 27 a guide for moving the movable part 26 in the X-axis direction.

  In the electromagnetic field measuring apparatus having such a configuration, the stay 21 on which the antenna 16 facing the Y-axis direction is mounted and fixed is further movable in the Y-axis direction by the movable part 23 and in the Z-axis direction by the movable part 24. Each part 26 can be moved in the X-axis direction.

  It is possible to measure the electromagnetic field on the XZ plane (measurement surface 17) at an arbitrary position in the space between the device under test 13 and the antenna mast 22, and the device under test 13 as shown in FIG. The electromagnetic field distribution of the rectangular parallelepiped side surface (measurement surface 17) as the center can be represented. In FIG. 12, contour stripes indicate portions having the same electromagnetic field strength, and the central stripe portion indicates stronger electric field strength. Further, by rotating the turntable 15 by 90 degrees and measuring in the same manner, the electromagnetic field distribution on the other side face of the rectangular parallelepiped can be obtained.

  On the other hand, a proposal has been made to shorten the measurement time by performing simultaneous measurement using a plurality of antennas (see, for example, Patent Document 2).

  FIG. 13 is a configuration diagram schematically showing a third conventional electromagnetic field measuring apparatus configured to enable high-speed measurement of an electromagnetic field.

  In FIG. 13, an object to be measured 18 using an antenna that radiates radio waves is attached and fixed to the tip of a turntable 19 for rotating about the Z axis. The antenna group 28 for measuring the electromagnetic wave radiated from the device under test 18 is attached to the semicircular guide 29 at equal intervals. The semicircular guide 29 is provided with an absorber 34 for reducing electromagnetic wave reflection on the surface of the semicircular guide 29, and the center of the semicircular guide 29 is measured. Wheels 30 are provided to match the center of the object 18.

In the electromagnetic field measuring apparatus having such a configuration, the received signals received by the respective antennas of the antenna group 28 mounted on the semicircular guide 29 are modulated at different frequencies and then synthesized. Since the signals are transmitted as two measurement signals, the electromagnetic field can be measured at high speed almost in real time without switching the antenna group 28 for each measurement position.
JP 2000-230954 A JP 2006-234602 A (for example, FIG. 8)

  However, the conventional electromagnetic field measurement apparatus that three-dimensionally measures the electromagnetic waves radiated from the electronic device has a problem that the measurement time is enormous in the configuration using the single antenna. In addition, in the configuration using a plurality of antennas that perform simultaneous measurement, there is a problem that measurement accuracy deteriorates due to interference between antennas.

  That is, in the case of the configuration of the first conventional electromagnetic field measurement apparatus using the single antenna shown in FIG. 9, there are many measurement points for obtaining the electromagnetic field distribution, and the measurement takes a long time. For example, in FIG. 9, when measuring a hemisphere at intervals of 10 degrees, the movement along the guide 33 is 0 to 90 degrees and 10 places, and the rotation of the turntable 12 is 0 to 360 degrees and 35 places is totaled. Since it is necessary to move to 350 locations and perform measurement, even if the measurement time for one location is 30 seconds, approximately 3 hours are required for measurement.

  Also, in the second conventional electromagnetic field measurement apparatus using a single antenna shown in FIG. 11, there are many measurement points for obtaining the electromagnetic field distribution, and it takes an enormous amount of time for the measurement. Furthermore, in this case, since the measurement results are divided for each rotation angle of the turntable 15, there arises a problem that it takes time and effort to synthesize, and since the measurement direction of the antenna 16 faces the Y axis direction, There also arises a problem that it becomes difficult to measure the surface (XY plane).

  In such a configuration using a single antenna, when attempting to measure an electromagnetic field distribution with a small measurement interval, the number of measurement points increases and the measurement time further increases.

  In addition, when the directional antenna that measures the electromagnetic wave radiated from the object to be measured receives the electromagnetic wave that has arrived from the directional range that can be received with high sensitivity, the received electromagnetic wave is re-radiated toward the directional range. The Therefore, if another directional antenna for measurement exists within this directional range, an error occurs in the measured value of the electromagnetic wave radiated from the measurement object due to the re-radiation of the electromagnetic wave from the other directional antenna. End up.

  In the third conventional electromagnetic field measurement apparatus using a plurality of antennas as shown in FIG. 13 for shortening the measurement time, antennas arranged near both ends of the guide 29 in the antenna group 28 are mutually directed. Therefore, an error occurs in the measurement value of the electromagnetic wave in the antenna disposed near the end of the guide 29.

  Further, since the antenna affects the electromagnetic field around it due to its properties as a metal, if the antennas are arranged close to each other, an error occurs in the measured value of the electromagnetic field. Therefore, in the configuration of the antenna group 28 as shown in FIG. 13, mutual interference between adjacent antennas is unavoidable, and the measurement value error increases according to the number of antennas included in the antenna group 28.

  An object of the present invention is to provide an electromagnetic field measurement apparatus, a measurement system, and an electromagnetic field measurement method that can accurately measure an electromagnetic field in a short measurement time in consideration of the above-described conventional problems.

In order to solve the above-described problem, the first aspect of the present invention provides:
A plurality of directional antennas for receiving electromagnetic waves radiated from the device under test, with the maximum sensitivity direction directed toward the device under test;
A movable part capable of changing a relative position of the plurality of directional antennas with respect to the object to be measured;
The movable part is a position where each directional antenna can receive the electromagnetic wave radiated from the measurement object without being affected by the electromagnetic wave re-radiated by another directional antenna that has received the electromagnetic wave. , An electromagnetic field measuring apparatus for changing the relative position.

The second aspect of the present invention
The position where the electromagnetic wave can be received without being affected by the re-radiated electromagnetic wave is a position that does not fall within a predetermined beam width region of the other directional antenna,
In the electromagnetic field measurement apparatus according to the first aspect of the present invention, the predetermined beam width is an angle range in which an attenuation amount with respect to the maximum sensitivity of the other directional antenna is 20 dB or less.

The third aspect of the present invention
Each of the directional antennas is arranged on the same circumference centered on the center position, with the maximum sensitivity direction being directed to the center position to be measured.
The movable part maintains an angle formed by the maximum sensitivity directions of the directional antennas, and moves the directional antennas to measurement positions on the circumference.
Further, the measurement object is rotated about the axis passing through the center position with an axis perpendicular to the surface on which the measurement object perpendicular to the surface on which the circumference exists is placed. It is an electromagnetic field measuring device of the 2nd present invention provided with the measured object rotation part.

The fourth aspect of the present invention is
The angles formed by the directions of the adjacent measurement positions toward the center position are all the same predetermined angle,
The angle formed by each maximum sensitivity direction of each directional antenna is the electromagnetic field measurement apparatus according to the third aspect of the present invention, which is an integral multiple of the predetermined angle.

The fifth aspect of the present invention provides
When measuring the electromagnetic field distribution on a plurality of circumferences by moving each directional antenna on the circumference of a plurality of radii,
When the respective directional antennas are arranged on the circumference having the maximum radius among the plurality of circumferences, the predetermined beam width has an attenuation with respect to the maximum sensitivity of the other directional antennas of 20 dB or less. The electromagnetic field measurement apparatus according to the third aspect of the present invention is also applied when the determined predetermined beam width is also moved when each of the directional antennas is moved on the circumference of another radius. It is.

The sixth aspect of the present invention provides
The plurality of directional antennas are two,
The predetermined beam width of each directional antenna is less than 90 degrees;
In the electromagnetic field measuring apparatus according to the third aspect of the present invention, an angle formed by the maximum sensitivity directions of the two directional antennas is 90 degrees.

The seventh aspect of the present invention
The plurality of directional antennas are orthogonal to the rectangular parallelepiped so that the maximum sensitivity direction is oriented in a direction perpendicular to a surface where the electromagnetic field distribution is measured on a rectangular parallelepiped surface around the object to be measured. Two or three directional antennas arranged on two or three sides to be
The movable part is the electromagnetic field measurement apparatus according to the second aspect of the present invention, wherein the position of the two or three directional antennas is changed so as to move in the plane direction in which the movable parts are arranged.

In addition, the eighth aspect of the present invention
A plurality of directional antennas for receiving electromagnetic waves radiated from the device under test, with the maximum sensitivity direction directed toward the device under test;
A movable part capable of changing a relative position of the plurality of directional antennas with respect to the object to be measured;
The movable portion is configured such that each directional antenna can receive the electromagnetic wave without being affected by an adjacent directional antenna, and the shortest distance between the directional antennas is a predetermined distance or more. It is an electromagnetic field measurement device that changes the relative position.

The ninth aspect of the present invention provides
In the electromagnetic field measurement apparatus according to the eighth aspect of the present invention, the predetermined distance is 5 cm.

The tenth aspect of the present invention is
Each of the directional antennas is arranged on the same circumference centered on the center position, with the maximum sensitivity direction being directed to the center position to be measured.
The movable part maintains the shortest distance between the directional antennas to be equal to or greater than the predetermined distance, and moves the directional antennas to the measurement positions on the circumference.
Further, the measurement object is rotated about the axis passing through the center position with an axis perpendicular to the surface on which the measurement object perpendicular to the surface on which the circumference exists is placed. An electromagnetic field measuring apparatus according to an eighth aspect of the present invention, comprising an object rotating part.

The eleventh aspect of the present invention is
Each of the directional antennas is the electromagnetic field measuring apparatus according to the first or eighth aspect of the present invention, which can rotate at least 90 degrees with the maximum sensitivity direction as a rotation axis.

The twelfth aspect of the present invention is
An electromagnetic field measuring apparatus according to the first or eighth aspect of the present invention;
And a display unit that displays an electromagnetic field distribution obtained based on each electromagnetic field measurement value measured by each directional antenna receiving an electromagnetic wave.

The thirteenth aspect of the present invention is
A plurality of directional antennas that receive electromagnetic waves radiated from the device under test with the maximum sensitivity direction directed to the device under test, and each directional antenna received by another directional antenna that has received the electromagnetic waves. An antenna moving step for sequentially changing the relative position with respect to the measurement object at a position where the electromagnetic wave radiated from the measurement object can be received without being affected by the re-radiated electromagnetic wave;
An electromagnetic field measurement method comprising: an electromagnetic field measurement step in which each directional antenna receives an electromagnetic wave at the position and measures an electromagnetic field strength at each position sequentially changed by the antenna moving step. .

The fourteenth aspect of the present invention is
A plurality of directional antennas that receive electromagnetic waves radiated from the object to be measured with the maximum sensitivity direction directed to the object to be measured, and each directional antenna is not affected by an adjacent directional antenna. An antenna moving step in which the shortest distance between the directional antennas capable of receiving the electromagnetic wave is a predetermined distance or more, and sequentially changing the relative position with respect to the object to be measured;
An electromagnetic field measurement method comprising: an electromagnetic field measurement step in which each directional antenna receives an electromagnetic wave at the position and measures an electromagnetic field strength at each position sequentially changed by the antenna moving step. .

  The present invention can provide an electromagnetic field measurement apparatus, a measurement system, and an electromagnetic field measurement method that can accurately measure an electromagnetic field in a short measurement time.

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

(Embodiment 1)
FIG. 1 is a block diagram schematically showing an electromagnetic field measuring apparatus according to Embodiment 1 of the present invention. In addition, the same code | symbol is used for the same component as the 1st conventional electromagnetic field measuring apparatus shown in FIG.

  In FIG. 1, an object to be measured 11 for measuring radiated electromagnetic waves is placed on a turntable 12 that rotates the object to be measured 11. Antennas 14a and 14b for measuring electromagnetic waves radiated from the device under test 11 are arranged on a semicircular guide 33 with the center of the device under test 11 as the origin, and the movable parts 20a and 20b are connected to the antenna 14a. And 14 b are moved along the guide 33. The surface of the turntable 12 on which the device under test 11 is placed is a surface perpendicular to the surface formed by the semicircular shape of the guide 33 and is perpendicular to the surface of the turntable 12 and the surface of the device under test 11. The DUT 11 is rotated by the turntable 12 with the axis passing through the measurement center as the rotation axis.

  The antennas 14a and 14b are directional antennas having directivity with respect to the direction in which electromagnetic waves are received, and the broken line toward the device under test 11 shown in FIG. 1 indicates the maximum sensitivity direction of the antennas 14a and 14b. In addition, areas 35a and 35b shown by hatching in FIG. 1 indicate directivity ranges in which the antennas 14a and 14b can receive electromagnetic waves with high sensitivity. Here, the directivity ranges 35a and 35b of the antenna indicate ranges determined by the beam width α in which the attenuation amount with respect to the maximum sensitivity of each of the antennas 14a and 14b is 20 dB or less.

Further, as shown in FIG. 1, the antennas 14a and 14b are arranged at positions that do not exist in the directivity ranges 35b and 35a of the antennas. Further, the antennas 14a and 14b are disposed at positions where the shortest distance L _min is 5 cm or more. Here, the shortest distance L _min is the shortest distance between the metal portions of the antennas 14a and 14b.

  In the electromagnetic field measurement apparatus of the first embodiment having such a configuration, the movable parts 20a and 20b are arranged so that the antennas 14a and 14b are semicircular while maintaining the angle β between the maximum sensitivity directions toward the device under test 11. It moves along the guide 33 on the circumference. Then, at each measurement position where the antennas 14a and 14b are moved, the electromagnetic fields at the measurement positions are measured by the antennas 14a and 14b. The object to be measured 11 is rotated by a predetermined angle by the turntable 12, and similarly, the antennas 14a and 14b are moved by the movable portions 20a and 20b to measure the electromagnetic field at each rotated angular position. The hemispherical electromagnetic field distribution around the object 11 can be measured.

Since the antennas 14a and 14b do not enter the directivity ranges 35b and 35a of the antennas, and the electromagnetic field is measured at each measurement position where the shortest distance L _min between the antennas 14a and 14b is 5 cm or more, mutual interference Highly accurate measurement is possible with very little.

  Further, since the electromagnetic fields can be measured at the positions of the two antennas 14a and 14b at the respective measurement positions where the antennas 14a and 14b are both moved along the guide 33 on the semicircular circumference, the 1 shown in FIG. The electromagnetic field measurement distribution can be measured in a shorter time than a conventional electromagnetic field measuring apparatus that measures with one antenna 14.

  The process in which the movable parts 20a and 20b move the antennas 14a and 14b to the respective measurement positions is an example of the antenna moving step of the present invention. The process in which the antennas 14a and 14b measure the electromagnetic field at each measurement position is This is an example of the electromagnetic field measurement step of the invention.

  Here, in the electromagnetic field measurement apparatus according to the first embodiment, a positional relationship in which each antenna is arranged to enable high-precision measurement with a plurality of antennas will be described below.

  FIG. 2 shows the maximum signal level and floor noise level at each frequency. 2A shows the maximum signal level, FIG. 2B shows the floor noise level, and FIG. 2C shows the maximum signal level and the floor noise level.

  The acceptable level of noise for a signal is highly dependent on the maximum level of the signal at each frequency, the floor noise level of the measurement environment, and the measurement environment.

  The object 11 to be measured in the electromagnetic field measurement apparatus according to the first embodiment is a consumer electronics device or a high-frequency device, and as shown in FIGS. 2 (a) and 2 (b), the dynamic range is about 60 dB at the maximum, The measurement is assumed in an anechoic chamber where dark noise (= floor noise) is about 20 dB.

  Therefore, since a signal below the floor noise level is hidden behind the floor noise and cannot be discriminated, the difference between the maximum level of the signal and the floor noise level is an ideal attenuation, which is usually about 40 dB (1/10000). In addition, noise less than the difference (dynamic range) of the signal can be clearly distinguished from the signal. Therefore, in practice, an attenuation amount (20 dB) of about the dynamic range is sufficient as shown in FIG. It can be said that there is. The dynamic range of the signal varies greatly depending on the object to be measured and the frequency, but if it differs by 20 dB (1/100) or more, the influence on the measurement result is 0.004 dB as shown in Equation 1, which can be almost ignored. Measurement data can also be separated.

Next, the range in which a directional antenna affects other antennas will be described.

  FIG. 3A is a diagram for explaining a range affected by re-radiation of electromagnetic waves from an antenna having directivity.

  A range in which the influence from the antenna 40 is greater than −ndB is determined from the directivity characteristics of the antenna 40 having directivity and the circle having the influence from the antenna 40 around −ndB around the antenna 40. In FIG. 3A, a range surrounded by a straight line connecting the antenna 40 and the intersection of the directivity characteristic of the antenna 40 indicated by the broken line and the circle of −ndB where the influence from the antenna 40 is − The influence is in a range larger than -ndB. That is, the region with the beam width α centered on the main beam direction, which is indicated by hatching in FIG. 3A, is a region where the influence from the antenna 40 is greater than −ndB.

  FIG. 3B is a diagram showing a range that is affected by re-radiation of electromagnetic waves from the dipole antenna 41.

  When the dipole antenna 41 is used as an example, the directivity characteristic is circular as shown in FIG. 3B. Therefore, the range where the influence from the dipole antenna 41 is larger than −20 dB is the beam width α = 120 ° indicated by hatching. It becomes the area of.

  In other words, if another antenna is placed in the shaded area, the measured value of the electromagnetic field at that antenna will be affected. On the other hand, when another antenna is disposed outside this region, it can be said that there is no influence on the measured value of the electromagnetic field at that antenna.

  In the case of an antenna having a sharper directivity than a dipole antenna, the beam width α indicating a range in which the influence from the antenna is greater than −20 dB is an angle narrower than that in the case of a dipole antenna (120 °).

  As shown in FIG. 1, when a plurality of antennas 14a and 14b are arranged on a circumferential guide 33 having an equal distance from the device under test 11, when the same antenna having the same beam width α is used, 2 By setting the angle β formed by the maximum sensitivity directions of the two antennas 14a and 14b to be within the angle range represented by Formula 2, the antennas 14a and 14b are arranged so as not to enter the directivity ranges 35b and 35a of the antennas. be able to.

For example, when dipole antennas are used as the antennas 14a and 14b, the beam width α at this time is 120 ° as described with reference to FIG. The antennas 14a and 14b may be disposed.

  Further, when other antennas are close to each other, an error is caused in the measured value of the electromagnetic field due to the influence of the electromagnetic field radiated from the antenna.

  FIG. 4 is a diagram illustrating the strength of the electromagnetic field radiated from the minute dipole antenna. As shown in FIG. 4, the intensity of the electromagnetic field radiated to the observation point P (r, θ, φ) away from the minute dipole antenna by the distance r is given by the equation shown in Equation 3 using Maxwell's equations. It is done.

Furthermore, the amount of attenuation at the observation point P, which is a distance r away from the minute dipole antenna, can be obtained by the mathematical expression of Equation 4.

FIG. 5 is a graph showing the relationship between the distance from the antenna and the attenuation obtained from the mathematical expressions of Equations 3 and 4.

In the mathematical formula obtained by Equation 4, since E _r and E _θ are infinite at the center of the antenna (r = 0), R1 = 0.01 (1 cm) is assumed to be the electric field at the center of the antenna. We are looking for 5 graphs. This assumption is valid because the electric field in the conductor is constant.

  From the graph of FIG. 5, it can be seen that if the shortest distance between the antennas is about 2 cm, the attenuation is 10 dB, and if the shortest distance between the antennas is about 5 cm, the attenuation is 20 dB.

  In consideration of the fact that the electromagnetic wave radiated from the object to be measured has a sharper directivity than the small dipole antenna of FIG. 4 and the attenuation is larger than that of the graph of FIG. 5, in the first embodiment, the shortest distance between the antennas. Is 5 cm or more at which the attenuation is 20 dB or more. If the shortest distance between the antennas is less than 5 cm, an error may occur in the measured value of the electromagnetic field from the object to be measured due to the influence of the electromagnetic field radiated from the adjacent antenna.

  FIG. 6 is a configuration diagram schematically illustrating a specific arrangement example of antennas of the electromagnetic field measurement apparatus according to the first embodiment of the present invention. In addition, the same code | symbol is used for the same component as the electromagnetic field measuring apparatus shown in FIG.

  Antennas 36a and 36b for measuring electromagnetic waves radiated from the device under test 11 are attached to a semicircular guide 33 with the center of the device under test 11 as the origin, and the movable portions 38a and 38b are connected to the antenna 36a. And 36 b are moved along the guide 33.

  The antennas 36a and 36b are directional antennas having a directivity with a beam width α of 90 ° or less in a range where the attenuation with respect to the maximum sensitivity direction is 20 dB or less, and the maximum sensitivity of the antennas 36a and 36b toward the DUT 11 is measured. It arrange | positions so that the angle (beta) which a direction makes may be 90 degrees.

  From Equation 2, since the beam width α is 90 ° or less, by setting β = 90 °, the antennas 36a and 36b do not fall within the directivity ranges 37b and 37a of the mutual antennas.

  In the electromagnetic field measuring apparatus having such a configuration, the movable portions 38a and 38b are arranged so that the antennas 36a and 36b are arranged on a semicircular shape while maintaining an angle β = 90 ° between the maximum sensitivity directions toward the device under test 11. It moves along the guide 33. Then, at each measurement position where the antennas 36a and 36b are moved, the electromagnetic field at the measurement position is measured by the antennas 36a and 36b.

  When the antenna 36a performs measurement at each measurement position within a range of a quarter circumference (90 ° from the measurement center) of the guide 33, the antenna 36b is within another quarter circumference of the guide 33. Since the measurement at each measurement position in the range is simultaneously performed, the measurement is performed at each measurement position in the range within the half circumference (180 ° from the measurement center) of the guide 33 at that time.

  In the first embodiment, the two antennas 14a and 14b or the antennas 36a and 36b are provided on the guide 33. However, the antennas do not fall within the directivity range of other antennas, and If the minimum distance is 5 cm or more, three or more antennas are provided on the guide 33, and the antennas are moved on the guide 33 while maintaining the angle formed by the maximum sensitivity direction of the antennas. You may make it make it.

  As the number of antennas is increased, the number of measurement positions that can be measured simultaneously increases, so that the electromagnetic field distribution can be obtained in a shorter time.

  Further, when each measurement position on the guide 33 is set at a predetermined angle from the measurement center, the angle β formed by the maximum sensitivity direction of the antennas installed adjacent to each other is an angle that is an integral multiple of the predetermined angle. By doing so, measurement can be performed efficiently.

  For example, when the adjacent measurement positions on the guide 33 are positions at 5 ° intervals from the measurement center, the angle β formed by the maximum sensitivity directions of the two adjacent antennas is set to 60 ° which is an integral multiple of 5 °. When set, when the electromagnetic field is measured at the measurement position, which is one of the antennas, the measurement can be performed at a measurement position separated by 60 ° with the other antenna. That is, by moving the two antennas while maintaining the angle β formed by the maximum sensitivity directions of the two antennas, both antennas can be simultaneously moved to an effective measurement position.

  In addition, a plurality of hemispherical electromagnetic field distributions having different radii may be obtained for one object to be measured. In this case, the angle β formed by the maximum sensitivity directions of two adjacent antennas is set to the most radius. The angle β determined from the beam width α of each antenna at a large measurement position and the angle β determined there may be applied to measurement with a smaller radius. Since the angle β formed by the maximum sensitivity direction of two adjacent antennas needs to be increased as the radius increases, the angle β determined at the largest radius can be used to measure other antennas at any radius. It is possible to obtain an accurate measurement value having a small influence from the above.

  In the first embodiment, the beam width α of each antenna is determined on the assumption that the attenuation characteristic of the electromagnetic wave re-radiated when the antenna receives the electromagnetic wave from the object to be measured is equal to the attenuation characteristic of the received electromagnetic wave. did.

  As described above, a plurality of directional antennas are arranged at positions that do not fall within the directivity range of other antennas so that the shortest distance from the other directional antennas is 5 cm or more. By measuring the electromagnetic field by changing the relative position with respect to the object to be measured while maintaining the relative positional relationship, it is possible to perform highly accurate measurement with very little mutual interference between the antennas.

(Embodiment 2)
FIG. 7 is a schematic diagram showing the basic principle of the electromagnetic field measurement apparatus according to the second embodiment of the present invention.

  In FIG. 7, reference numeral 42 denotes an object to be measured for radiated electromagnetic waves, 43a to 43c are directional antennas for measuring the electromagnetic waves radiated from the object to be measured 42, and 44a to 44c are antennas 43a to 43c with high sensitivity to electromagnetic waves. The directivity range that can be received is shown. The directivity ranges 44a to 44c of the antennas 43a to 43c are simply displayed by being interrupted at the tip of the device under test 42, but are actually continuous to infinity, and the antennas 43a to 43c are In addition to receiving electromagnetic waves coming from the directivity ranges 44a to 44c with high sensitivity, the received electromagnetic waves are radiated toward the directivity ranges 44a to 44c.

  In such a configuration, the antennas 43a to 43c are arranged so as not to enter the directivity ranges 44a to 44c around the device under test 42 in a state where the measurement directions are orthogonal to each other, and the directivity ranges 44a to 44c. It has directivity for sensing electromagnetic waves coming from the direction 44c. That is, the angle γ formed by the maximum sensitivity direction of the antenna 43a and the antenna 43b, the angle φ formed by the maximum sensitivity direction of the antenna 43a and the antenna 43c, and the angle θ formed by the maximum sensitivity direction of the antenna 43b and the antenna 43c are both 90 °. It is arranged to be.

  For this reason, even if the electromagnetic waves radiated from the DUT 42 are re-radiated by the antennas 43a to 43c, the other antennas 43a to 43c do not exist in the directivity ranges 44a to 44c. In the high-speed measurement of the used electromagnetic wave, high-accuracy measurement with very little mutual interference between the antennas 43a to 43c is possible.

  FIG. 8 shows a configuration diagram of a rectangular parallelepiped electromagnetic field measuring apparatus according to the second embodiment of the present invention, which uses the basic principle of FIG. 7 in an orthogonal coordinate system.

  In FIG. 8, 51 is an object to be measured for radiated electromagnetic waves, 54a to 54c are directional antennas for measuring the electromagnetic waves radiated from the object to be measured 51, and 55a to 55c are antennas 54a to 54c with high sensitivity to electromagnetic waves. Receivable directivity ranges 53a to 53c indicate movable parts for moving the three-dimensional positions of the antennas 54a to 54c. The movable parts 53a to 53c are configured to move three-dimensionally by the same configuration as the conventional electromagnetic field measuring apparatus shown in FIG. 11, but are omitted in FIG. 8 for simplification. Yes.

  In such a configuration, the antennas 54a to 54c are arranged at positions on the surface of the rectangular parallelepiped in the space with the measured object 51 as the center of the bottom surface, and the measurement direction is perpendicular to the surface of the rectangular parallelepiped and directed to the inside of the rectangular parallelepiped. .

  Further, since the positions of the antennas 54a to 54c are controlled by the movable parts 53a to 53c so as not to enter the directivity ranges 55a to 55c, the electromagnetic waves radiated from the measurement object 51 are transmitted by the antennas 54a to 54c. Even when re-radiated, the other antennas 54a to 54c do not exist in the directivity ranges 55a to 55c, and the antennas 54a to 54c are mutually connected in high-speed measurement of rectangular parallelepiped electromagnetic waves using the plurality of antennas 54a to 54c. High-accuracy measurement with very little interference is possible.

  By moving the antennas 54a to 54c on the respective surfaces by the movable portions 53a to 53c and measuring the electromagnetic fields at the respective measurement positions, the electromagnetic field distribution on the three surfaces of the rectangular parallelepiped in which the antennas 54a to 54c are arranged. Can be requested.

  Then, the position of the DUT 51 is changed so that the other three surfaces of the rectangular parallelepiped that is not measured are directed to the antennas 54a to 54c, or the antennas 54a to 54c are placed at the positions of the other three surfaces of the rectangular parallelepiped that are not measured. By moving and measuring in the same manner, the electromagnetic field distribution as shown in FIG. 12 can be obtained for all six faces of the rectangular parallelepiped.

  Furthermore, in the electromagnetic field measurement apparatus according to the second embodiment, the distance between the antennas 54a to 54c and the DUT 51 is changed by the movable parts 53a to 53c, so that the distribution and size of the hemispherical electromagnetic fields with different radii are different. It is possible to measure a rectangular parallelepiped surface electromagnetic field distribution having different heights, and to measure the electromagnetic field distribution corresponding to the distance from the DUT 51 to the antennas 54a to 54c with high accuracy.

  In the electromagnetic field measurement apparatus according to the second embodiment shown in FIG. 8, the three antennas 54a to 54c are arranged on the three surfaces of the rectangular parallelepiped. The configuration may be such that two antennas are arranged one by one. In this case, when measuring the electromagnetic field distribution on the upper surface or the lower surface of the rectangular parallelepiped, it is only necessary to change the position of the device under test 51 so that the upper surface or the lower surface of the device under test 51 faces one of the antennas.

  Further, in the first embodiment, the orientation of the antennas 14a, 14b, 36a and 36b, the orientation of the antennas 54a, 54b and 54c in the second embodiment, and the respective measurement directions (maximum sensitivity directions) as rotational axes are at least 90. A mechanism capable of rotating may be provided. By providing such a rotation mechanism, it is possible to measure the electromagnetic field for vertical polarization and the electromagnetic field for horizontal polarization.

  Further, by connecting a computer and a display device to the electromagnetic field measurement apparatus of each embodiment, the electromagnetic fields at a plurality of measurement positions are automatically measured, and FIG. 10 and FIG. A measurement system that displays an electromagnetic field distribution as shown in FIG. 12 on a display device such as a display can be realized.

  As described above, by using the electromagnetic field measurement apparatus of the present invention, it becomes possible to reduce interference between antennas in high-speed simultaneous measurement using a plurality of antennas and prevent deterioration in measurement accuracy. Unnecessary radiation analysis efficiency of electronic equipment, which becomes difficult by obtaining accurate electromagnetic field distribution measurement, can be improved.

  An electromagnetic field measurement apparatus, a measurement system, and an electromagnetic field measurement method according to the present invention have an effect of accurately measuring an electromagnetic field in a short measurement time, and measure an electromagnetic field measurement apparatus that measures an electromagnetic wave radiated from an electronic device, It is useful as a measurement system and an electromagnetic field measurement method.

The block diagram which showed typically the electromagnetic field measuring device of Embodiment 1 of this invention (A) The figure which shows the maximum level of the signal in each frequency, (b) The figure which shows the floor noise level in each frequency, (c) The figure which shows the maximum level and the floor noise level in each frequency (A) The figure explaining the range affected by the re-radiation of the electromagnetic wave from the antenna having directivity, (b) The figure showing the range affected by the re-radiation of the electromagnetic wave from the dipole antenna A figure explaining the strength of the electromagnetic field radiated from a minute dipole antenna Graph showing the relationship between distance from antenna and attenuation The block diagram which showed typically the example of specific arrangement | positioning of the antenna of the electromagnetic field measuring apparatus of Embodiment 1 of this invention Schematic diagram showing the basic principle of the electromagnetic field measurement apparatus according to Embodiment 2 of the present invention. Configuration diagram of a rectangular parallelepiped electromagnetic field measurement apparatus according to Embodiment 2 of the present invention. Configuration diagram schematically showing a first conventional electromagnetic field measuring apparatus The figure which showed an example of the electromagnetic field distribution obtained with the 1st conventional electromagnetic field measuring device The block diagram which showed typically the 2nd conventional electromagnetic field measuring apparatus The figure which showed an example of the electromagnetic field distribution obtained with the 2nd conventional electromagnetic field measuring device Configuration diagram schematically showing a third conventional electromagnetic field measuring apparatus

Explanation of symbols

11, 13, 18, 42, 51 DUT 12, 15, 19 Turntable 14, 14a, 14b, 16, 36a, 36b, 40, 43a, 43b, 43c, 54a, 54b, 54c Antenna 17 Measurement surface 20, 20a, 20b, 38a, 38b, 53a, 53b, 53c Movable part 21 Stay 22 Antenna mast 23, 24, 26 Movable part 27, 29, 33 Guide 28 Antenna group 30 Wheel 34 Absorber 35a, 35b, 35c, 37a, 37b 44a, 44b, 44c, 55a, 55b, 55c Antenna directivity range 41 Dipole antenna

Claims (14)

A plurality of directional antennas for receiving electromagnetic waves radiated from the device under test, with the maximum sensitivity direction directed toward the device under test;
A movable part capable of changing a relative position of the plurality of directional antennas with respect to the object to be measured;
The movable part is a position where each directional antenna can receive the electromagnetic wave radiated from the measurement object without being affected by the electromagnetic wave re-radiated by another directional antenna that has received the electromagnetic wave. An electromagnetic field measuring apparatus for changing the relative position. The position where the electromagnetic wave can be received without being affected by the re-radiated electromagnetic wave is a position that does not fall within a predetermined beam width region of the other directional antenna,
The electromagnetic field measurement apparatus according to claim 1, wherein the predetermined beam width is an angle range in which an attenuation with respect to a maximum sensitivity of the other directional antenna is 20 dB or less. Each of the directional antennas is arranged on the same circumference centered on the center position, with the maximum sensitivity direction being directed to the center position to be measured.
The movable part maintains an angle formed by the maximum sensitivity directions of the directional antennas, and moves the directional antennas to measurement positions on the circumference.
Further, the measurement object is rotated about the axis passing through the center position with an axis perpendicular to the surface on which the measurement object perpendicular to the surface on which the circumference exists is placed. The electromagnetic field measuring apparatus according to claim 2, comprising a measured object rotating unit. The angles formed by the directions of the adjacent measurement positions toward the center position are all the same predetermined angle,
The electromagnetic field measurement apparatus according to claim 3, wherein an angle formed by each maximum sensitivity direction of each directional antenna is an integer multiple of the predetermined angle. When measuring the electromagnetic field distribution on a plurality of circumferences by moving each directional antenna on the circumference of a plurality of radii,
When the respective directional antennas are arranged on the circumference having the maximum radius among the plurality of circumferences, the predetermined beam width has an attenuation with respect to the maximum sensitivity of the other directional antennas of 20 dB or less. The electromagnetic field measurement apparatus according to claim 3, wherein the determined angle range is applied, and the determined predetermined beam width is also applied when each directional antenna is moved on a circumference of another radius. . The plurality of directional antennas are two,
The predetermined beam width of each directional antenna is less than 90 degrees;
The electromagnetic field measurement apparatus according to claim 3, wherein an angle formed by the maximum sensitivity direction of the two directional antennas is 90 degrees. The plurality of directional antennas are orthogonal to the rectangular parallelepiped so that the maximum sensitivity direction is oriented in a direction perpendicular to a surface where the electromagnetic field distribution is measured on a rectangular parallelepiped surface around the object to be measured. Two or three directional antennas arranged on two or three sides to be
The electromagnetic field measurement apparatus according to claim 2, wherein the movable unit changes the positions of the two or three directional antennas so as to move in the plane direction in which the movable parts are arranged. A plurality of directional antennas for receiving electromagnetic waves radiated from the device under test, with the maximum sensitivity direction directed toward the device under test;
A movable part capable of changing a relative position of the plurality of directional antennas with respect to the object to be measured;
The movable portion is configured such that each directional antenna can receive the electromagnetic wave without being affected by an adjacent directional antenna, and the shortest distance between the directional antennas is a predetermined distance or more. An electromagnetic field measurement device that changes the relative position.   The electromagnetic field measurement apparatus according to claim 8, wherein the predetermined distance is 5 cm. Each of the directional antennas is arranged on the same circumference centered on the center position, with the maximum sensitivity direction being directed to the center position to be measured.
The movable part maintains the shortest distance between the directional antennas to be equal to or greater than the predetermined distance, and moves the directional antennas to the measurement positions on the circumference.
Further, the measurement object is rotated about the axis passing through the center position with an axis perpendicular to the surface on which the measurement object perpendicular to the surface on which the circumference exists is placed. The electromagnetic field measuring apparatus according to claim 8, further comprising a measured object rotating unit.   The electromagnetic field measuring apparatus according to claim 1, wherein each of the directional antennas can rotate at least 90 degrees with the maximum sensitivity direction as a rotation axis. The electromagnetic field measurement apparatus according to claim 1 or 8,
A measurement system comprising: a display unit that displays an electromagnetic field distribution obtained based on each electromagnetic field measurement value measured by each directional antenna receiving an electromagnetic wave. A plurality of directional antennas that receive electromagnetic waves radiated from the device under test with the maximum sensitivity direction directed to the device under test, and each directional antenna received by another directional antenna that has received the electromagnetic waves. An antenna moving step for sequentially changing the relative position with respect to the measurement object at a position where the electromagnetic wave radiated from the measurement object can be received without being affected by the re-radiated electromagnetic wave;
An electromagnetic field measurement method comprising: an electromagnetic field measurement step in which each directional antenna receives an electromagnetic wave at the position and measures an electromagnetic field intensity at each position that is sequentially changed by the antenna moving step. A plurality of directional antennas that receive electromagnetic waves radiated from the object to be measured with the maximum sensitivity direction directed to the object to be measured, and each directional antenna is not affected by an adjacent directional antenna. An antenna moving step in which the shortest distance between the directional antennas capable of receiving the electromagnetic wave is a predetermined distance or more, and sequentially changing the relative position with respect to the object to be measured;
An electromagnetic field measurement method comprising: an electromagnetic field measurement step in which each directional antenna receives an electromagnetic wave at the position and measures an electromagnetic field intensity at each position that is sequentially changed by the antenna moving step.