Patent Application
20150219704
The present invention relates to an electromagnetic wave visualization device.
Various electronic devices supporting social infrastructure are speeding up as becoming highly functional, and the devices are required to be designed so that electromagnetic noise emitted from the devices does not cause electromagnetic interference on wireless communications devices, which will be further introduced. In the case where electromagnetic interference occurs, a rapid survey on site is required, and a device for visualizing a source of such electromagnetic noise in real time is required.
PTL 1 (JP 2011-53055 A) and PTL 2 (JP 2000-214198 A) disclose a technique for visualizing an electromagnetic wave. PTL 1 states that “two pairs of antennas, i.e. four antennas, disposed on an X axis and a Y axis which are orthogonal to each another, or three antennas sharing one antenna, an image camera for capturing scenery of a measurement target region, a detection unit for detecting an antenna signal, a signal processor/analysis unit, and a display unit are included. The signal processor/analysis unit measures time differences Δtx and Δty of electromagnetic waves arriving at the antenna pairs disposed on the X axis and the Y axis, and specifies a divided region obtained by dividing the measurement target region based on the values of Δtx and Δty. The display unit displays the specified divided region by superimposing the region on scenery captured by the image camera.”
Also, PTL 2 states that “a displacing unit 19 for displacing a magnetic field probe 4 in the vicinity of a target to be measured, a magnetic field detection unit 6, and a calibration unit for calibrating a direction of the magnetic field probe 4, in which its directivity is maximum, to a direction of a magnetic field to be detected are included. The calibration unit includes a probe deflector 27 for changing a direction of a magnetic field probe, a unit for generating a magnetic field for calibration 5, and a control unit 7 for controlling an operation of the probe deflector. The control unit 7 changes a direction of the magnetic field probe 4 in a magnetic field for calibration by operating the probe deflector 27, and detects a direction of directivity of the magnetic field probe 4 from output of the magnetic field detection unit 6 at the time”.
PTL 1: JP 2011-53055 A
PTL 2: JP 2000-214198 A
In the technique described in PTL 1, an arrival direction is calculated by using an arrival time difference of electromagnetic waves at an antenna pair. Therefore, in the case where there are multiple wave sources, an appropriate time difference may not be detected, and an arrival direction may not be specified. Also, in the technique described in PTL 2, a sensor scans a surface of a target to be measured. Therefore, a source of electromagnetic noise in a device is easily found. On the other hand, due to the scan, the electromagnetic noise is not found in real time. Therefore, there is a problem that electromagnetic noise emitted at a burst may not easily be found.
As described above, it is hard to visualize multiple sources of electromagnetic noise in real time by the techniques described in PTL 1 and PTL 2.
Also, in actual measurement of electromagnetic noise, after an object emitting noise is specified by a distant electromagnetic field measuring device, an electromagnetic field is often measured in detail by using a near electromagnetic field measuring device to specify which part of the object is a cause of electromagnetic radiation. However, especially a large scale device cannot be installed in the near electromagnetic field measuring device. Also, even if a part of the large scale device is taken out and analyzed by the near electromagnetic field measuring device, a noise source in an operating environment cannot be specified since an actual operating environment of the device is different.
Therefore, the present invention provides an electromagnetic wave visualization device in which multiple sources of electromagnetic noise can be visualized in real time under an operating environment of the device in a far field and a near field.
A first representative configuration of the invention is as follows: An electromagnetic wave visualization device includes a sensor configured to detect an electromagnetic wave and output a detection signal of intensity depending on energy level of the detected electromagnetic wave, a variable resistance connected to the sensor, and a resistance adjustment unit configured to adjust a resistance value of the variable resistance connected to the sensor. An electromagnetic wave is visually measured by adjusting the resistance value of the variable resistance at the adjustment unit.
According to the present invention, a source of an electromagnetic wave in a far field and a near field can be visualized in real time.
A configuration of an electromagnetic wave visualization device according to an embodiment of the present invention will be described with reference to
As illustrated in
Each of the sensors in the sensor unit 2 is signal-connected to the signal processor/result display unit 5 via a transmission line 201a. The camera unit 4 is signal-connected to the signal processor/result display unit 5 via a transmission line 401a. The antenna unit 7 is signal-connected to the wave impedance calculation unit 8 via a transmission line 701a. The wave impedance calculation unit 8 is signal-connected to the resistance adjustment unit 3 via a transmission line 801a. The resistance adjustment unit 3 is signal-connected to the sensor unit 2 via a transmission line 301a.
The lens 1 converges an electromagnetic wave entering the lens, and changes an emission direction and an emission position of an electromagnetic wave emitted from the lens, depending on an arrival direction of the electromagnetic wave entering the lens. Electromagnetic waves of multiple arrival directions are converged at different positions so as to be focused. Multiple sensors are disposed in the sensor unit 2. The multiple sensors detect energy of electromagnetic waves emitted from the lens 1 and output detection signals of intensity depending on level of the detected energy. Therefore, a sensor at a position corresponding to a converging position (focus) of an electromagnetic wave entering the lens outputs a detection signal. More specifically, a sensor to output a detection signal differs depending on a converging position of an electromagnetic wave entering the lens.
Herein, a principle of electromagnetic wave measurement by each of the sensors in the sensor unit 2 according to the present invention will be described.
If the distance between the target to be measured 6 and the sensor unit 2 is shorter than the above, a wave impedance differs depending on a form of a wave source of the target to be measured. If a resistance value of the sensor unit 2 and a wave impedance differ, reflection occurs on a sensor surface, and an electromagnetic wave is hard to measure. Therefore, a resistance value of the sensor unit 2 needs to be conformed to a wave impedance. If the resistance is equal to a wave impedance of an electromagnetic wave, the electromagnetic wave is absorbed at the sensor unit 2 without reflecting.
As a configuration for conforming the above resistance value to a wave impedance value, a variable resistance 31 is provided among the sensors in the present invention. A wave impedance is calculated from a value measured at the antenna unit 7, and the variable resistance 31 is adjusted so as to be equal to a wave impedance value obtained from a result of the calculation. As a result, reflection of an electromagnetic wave on a sensor surface caused by a difference between a resistance value of the sensor unit 2 and a wave impedance is suppressed, and highly accurate real-time measurement of an electromagnetic wave becomes possible.
Next, configurations of the sensor unit 2 and the antenna unit 7 will be described in detail with reference to
The low-reflective electromagnetic field sensor according to the embodiment is, for example, realized by a periodic structure of mushroom-shaped metal. The periodic structure of mushroom-shaped metal is widely used because an electrical capacity and inductance for realizing low reflection can be controlled by a mushroom size.
As illustrated in
Each of the metal patches 21 is sufficiently small with respect to a wavelength λ of an electromagnetic wave to be measured, and the length of one side of the metal patch 21 is equal to or shorter than ( 1/10)λ. For example, in the case where a frequency of an electromagnetic wave to be measured is 2.4 GHz, one side of the metal patch 21 is assumed to be equal to or shorter than 12.5 mm. The metal patch 21 is not necessarily square although a square metal plate is used in the embodiment.
On the same surface as the metal patch 21, a micro loop antenna 71 and a micro dipole antenna 72 respectively measure a magnetic field and an electric field. A ratio between the magnetic field and the electric field is a wave impedance on a surface of the metal patch 21. Although the micro loop antenna 71 and the micro dipole antenna are arranged side by side in the embodiment, a distance between the antennas is preferably as small as possible and the antennas are preferably positioned so as not to interfere within a range of a variable resistance which changes depending on a required wave impedance. The antennas may be arranged anywhere as long as the above two conditions are satisfied.
Also, although two types of antennas, i.e., the micro loop antenna 71 and the micro dipole antenna 72 are used in the embodiment, the number of antennas is not limited to two. One antenna may be used as long as it can measure both of a magnetic field and an electric field.
As illustrated in
The voltage sensor 27 detects a voltage induced at both ends of the variable resistance 31 through the via for a voltage sensor 26. The voltage sensor 27, for example, includes an amplifier, an AD converter, and a voltage measuring instrument. When any of the metal patches 21 included in the low-reflective electromagnetic field sheet is irradiated with an electromagnetic wave, a voltage is induced only to a resistance 25 connected to the metal patch 21 irradiated with the electromagnetic wave. Therefore, an arrival direction of the electromagnetic wave can be specified from a location of the voltage sensor 27 connected to the resistance 25.
At this point, if the resistance 25 is at 377Ω which is equal to a wave impedance, impedances of a space and the sensor unit 2 are matched, the electromagnetic wave does not reflect, and energy of the electromagnetic wave is absorbed by the sensor unit 2.
The dielectric 20 includes the micro loop antenna 71 and the micro dipole antenna 71 in addition to the sensor unit 2. If an area of the micro loop antenna is denoted by s, a magnetic field H is calculated by [Formula 1] from a voltage v induced at the loop antenna.
Herein, μ0 denotes a dielectric constant in vacuum, ω denotes an angular frequency of a target to be measured. Also, an electric field E is calculated by [Formula 2] from a voltage v induced at a micro dipole antenna of effective length l.
A wave impedance Z0 is calculated by [Formula 3] from the obtained magnetic field H and electric field E, and the variable resistance 31 is adjusted at the resistance adjustment unit 3 so that the wave impedance Z0 and the variable resistance 31 become equal.
A magnetic field detection unit 711 of a micro loop antenna and an electric field detection unit 721 of a micro dipole antenna detect a voltage induced at each of the antennas, and a wave impedance is calculated at the wave impedance calculation unit 8 based on the voltage value.
For example, a digital potentiometer as illustrated in
The signal processor/result display unit 5 can receive a detection signal from each of multiple sensors of the sensor unit 2. When receiving the detection signal from any of the sensors of the sensor unit 2, the signal processor/result display unit 5 outputs a display signal including location information of the sensor, which has sent the detection signal, and intensity information of the received detection signal. Also, the signal processor/result display unit 5 has received an image signal of an image captured by the camera unit 4, and prepares and outputs a display signal in which a signal including sensor location information and information on intensity of the detection signal is superimposed on the image signal.
The signal processor/result display unit 5 can display a location of each of the multiple sensors of the sensor unit 2. When receiving a display signal, the signal processor/result display unit 5 displays, for example, on a liquid crystal display (LCD), locations of the sensors and intensity of a detection signal based on sensor location information and information on intensity of the detection signal, which are included in the display signal. Also, an image captured by the camera unit 4 is displayed at the same time.
In this manner, in the signal processor/result display unit 5, information including location information on a sensor, which has output a detection signal, and information on intensity of the detection signal is displayed by being superimposed on a measurement target image captured by the camera unit 4. For example, an electromagnetic field map in which a color display is changed depending on intensity of a detection signal may be displayed on a camera image. Also, in the case where the intensity of a detection signal is equal to or greater than a predetermined value, location information corresponding to a sensor with a predetermined value or more may be displayed by being superimposed on a measurement target image captured by the camera unit 4.
Cases of measuring a far field and a near field of an electromagnetic wave in the present invention will be described next.
First, the case of measuring a far field of an electromagnetic wave will be described. A far field of an electromagnetic wave is measured by the configuration illustrated in
The signal processor/result display unit 5 recognizes a location (number) of a sensor, which has output the detection signal, and intensity of the detection signal. The signal processor/result display unit 5 internally includes a table associating the sensor location (number) with an arrival angle of an electromagnetic wave, and obtains the arrival angle of an electromagnetic wave with reference to the table based on the location information of the sensor which has output the detection signal. Also, the signal processor/result display unit 5 has received an image signal of an image captured by the camera unit 4. The signal processor/result display unit 5 realizes visualization of an electromagnetic wave by preparing a display signal in which a signal including sensor location information and information on intensity of the detection signal is superimposed on the image signal, and displaying a location of the noise source 7 of the target to be measured 6 and noise level on the image captured by the camera unit 4.
Next, the case of measuring a near field of an electromagnetic wave will be described. A near field is measured by the configuration in which the lens 1 is removed as illustrated in
In the sensor unit 2, a sensor, in which incident energy is induced, outputs a detection signal of intensity depending on level of the induced energy. The signal processor/result display unit 5 recognizes a location (number) of a sensor, which has output the detection signal, and intensity of the detection signal. The signal processor/result display unit 5 internally includes a table associating the sensor location (number) with an arrival angle of an electromagnetic wave, and obtains the arrival angle of an electromagnetic wave with reference to the table based on the location information of the sensor which has output the detection signal.
Also, the signal processor/result display unit 5 has received an image signal of an image captured by the camera unit 4. The signal processor/result display unit 5 realizes visualization of an electromagnetic wave by preparing a display signal in which a signal including sensor location information and information on intensity of the detection signal is superimposed on the image signal, and displaying a location of the noise source 7 of the target to be measured 6 and noise level on the image captured by the camera unit 4. A near field may be measured first by removing the sensor unit 2 and capturing a target to be measured by the camera unit 4, and then detecting an electromagnetic field after the sensor unit 2 is assembled, and displaying the electromagnetic field on an image in the signal processor/image display unit 5. Also, although the antenna unit 7 and the sensor unit 2 are provided on the same substrate in the embodiment, they may be provided separately. For example, an electromagnetic field map in which a color display is changed depending on intensity of a detection signal may be displayed on a camera image. Also, in the case where the intensity of a detection signal is equal to or greater than a predetermined value, location information corresponding to a sensor with a predetermined value or more may be displayed by being superimposed on a measurement target image captured by the camera unit 4.
As described above, according to the present invention, a sensor for detecting an electromagnetic field highly accurately detects and visualizes arrival and intensity of an electromagnetic wave depending on an arrival direction of the electromagnetic wave. Accordingly, an electromagnetic wave measurement with improved real-time performance becomes possible. Also, a wave impedance is obtained by a micro dipole antenna and a micro loop antenna, and an electromagnetic wave can be measured in real time by conforming a variable resistance of the sensor to the wave impedance.
A second embodiment of the present invention will be described with reference to
For example, as illustrated in
As a result, the variable resistance 31 can be adjusted corresponding to change in a wave impedance on the low-reflective electric field sheet, and a non-reflecting state of an electromagnetic wave on the low-reflective electric field sheet can be maintained. In the embodiment, although the antenna unit 7 is disposed on a low-reflective electric field sheet, the antenna unit 7 may be disposed separately from the low-reflective electric field sheet.
As described above, according to the present invention, a sensor for detecting an electromagnetic field highly accurately detects and visualizes arrival and intensity of an electromagnetic wave depending on an arrival direction of the electromagnetic wave. Accordingly, an electromagnetic wave measurement with improved real-time performance becomes possible. Also, a wave impedance of each block is obtained from a micro dipole antenna and a micro loop antenna, and an electromagnetic wave can be measured in real time by conforming a surrounding variable resistance to the wave impedance.
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2012/072100 | 8/31/2012 | WO | 00 | 2/11/2015 |
