JP3292640B2 - Electromagnetic radiation measurement device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic radiation measuring device used for measuring electromagnetic radiation from printed circuit boards and circuit devices.

[0002]

2. Description of the Related Art In recent years, regulations have been established in many countries in order to minimize interference caused by unnecessary radiation generated from various electronic devices. For example, overseas, FCC (United States Federal Communications Commission), Standards such as CISPR (International Special Committee on Radio Interference) and VDE (German Institute of Electrical Engineers) have been established. In Japan as well, the voluntary standards of VCCI (Voluntary Council for Prevention of Interference with Information Processing Equipment) have been determined, and electronic device manufacturers are taking measures to suppress unnecessary radiation generated from various electronic devices. . These unnecessary radiation regulations are generally established for each frequency over a wide range from 30 MHz to 1 GHz. In addition, the measurement method measures the electric field strength at a position separated by a predetermined distance from the electronic device that is a source of unnecessary radiation, and the measurement environment and measuring instruments are special, so costs are generally low. It becomes bulky. Also, the measurement technique requires considerable expertise.

Recently, in order to reduce the time and cost for measuring unnecessary radiation and taking countermeasures for electronic equipment as described above, recently, the intensity of a nearby electromagnetic field radiated from a printed circuit board or similar circuit device of the electronic equipment has been reduced. A simple electromagnetic radiation measuring device for measuring the temperature is used. In these simple electromagnetic radiation measuring devices, a large number of means for detecting electromagnetic radiation are arranged in order to identify a portion (print pattern) having a high electromagnetic radiation level on a printed circuit board, and these are electronically connected. A method of sequentially selecting and measuring is adopted.

Conventionally, such an electromagnetic radiation measuring device detects electromagnetic radiation by a wire loop antenna having a printed pattern formed on a multilayer printed circuit board, as described in Japanese Patent Publication No. 5-67184. The signal is converted into an electric signal, and is sequentially switched electronically by a diode and applied to the transmission line. Also,
By arranging a large number of rows of electromagnetic radiation detectors constituted by a large number of wire loop antennas and one transmission line, and selecting the respective transmission line outputs in the signal selection unit, about 1000 wire loop antennas are provided. Some are configured to switch electronically sequentially, so that the electromagnetic radiation level at an arbitrary position on a printed circuit board can be measured.

FIG. 4 is a diagram showing a configuration of a conventional electromagnetic radiation measuring apparatus. In FIG. 4, a wire loop antenna 1 composed of a copper foil pattern of about 6 to 7 mm formed on a printed circuit board, a transmission line 2 formed in an inner layer of the printed circuit board, and a switching surface-mounted on a surface layer of the printed circuit board. The diode 3 forms an electromagnetic radiation detecting section row 4. One electromagnetic radiation detector row 4
Usually has 20 units of electromagnetic radiation detection composed of a combination of the wire loop antenna 1 and the switching diode 3.
Approximately 40 are arranged. The electromagnetic radiation detected by the wire loop antenna 1 is converted into an electric signal and applied to the transmission line 2 via the switching diode 3. The switching diode 3 is turned on by applying a voltage to the Y-direction control signal terminal 5. Then, only the wire loop antenna 1 at the selected position in the Y direction is electrically connected to the transmission line 2. Similarly, another Y-direction position can be selected by applying a voltage to another Y-direction control signal terminal. The terminating element 6 terminates the transmission line 2 at the characteristic impedance of the transmission line 2 (typically 50 ohms). The output of each electromagnetic radiation detector row 4 is output from the output terminal 7 to the signal selector 19. In the signal selection section 19, the output terminal 7 of each electromagnetic radiation detection section row 4 and the output terminal 7 of each electromagnetic radiation detection section row 4 of the transmission line 21 arranged orthogonally to each electromagnetic radiation detection section row 4 are connected. Switching diodes 20 are connected to the closest positions by switching diodes 20. One of the switching diodes 20 as many as the number of the electromagnetic radiation detection unit rows 4 is turned on, and all other switching diodes are turned off. By doing so, the output of one electromagnetic radiation detector array 4 is selected, and the output is guided to the output terminal 22 of the device.

As described above, in the prior art, one transmission line orthogonal to the electromagnetic radiation detector row is used as a signal selector for selecting each output of the many electromagnetic radiation detector rows. A diode is connected between the output terminal of each electromagnetic radiation detection unit and the position closest to each output terminal of the orthogonal transmission line, and a diode is connected to the output terminal of each electromagnetic radiation detection unit. Had been.

[0007]

However, in the above prior art, for example, one switching diode 20 is used.
When a is on, all the other switching diodes 20 in the signal selection unit 19 are off, so that the range indicated by A is closer to the device end than the switching diode 20a on the transmission line 21, ie, A. One end operates as an open transmission line. As a result, the impedance becomes low at the frequency where λg, where λg = 4 × A, is set as the wavelength on the printed circuit board, and the transmission frequency characteristic of the signal selection unit 19 that selects the output of the electromagnetic radiation detection unit array 4 and leads the output to the device Had deteriorated. Therefore, the frequency at which λg is the wavelength on the printed circuit board is the highest measurement frequency of this electromagnetic radiation measurement device, and limits the measurable position range and frequency band.

If it is desired to increase the maximum measurable frequency, it is necessary to shorten the entire length of the transmission line 21.
If the measurable position range is limited and the measurable position range is to be widened, it is necessary to lengthen the entire length of the transmission line 21, so that there is a problem that the measurable frequency band is limited. For example, when the total length of the transmission line 21 is 300 mm, the maximum length of the transmission line whose one end is open is approximately 150 mm. Therefore, the maximum frequency that can be measured on a general printed circuit board having a relative dielectric constant is approximately 230 MHz.
Becomes However, in general, the regulation range of the unnecessary radiation, which is the measurement frequency of the electromagnetic radiation measurement device, is 30 MHz to 1 GHz.
, The maximum measurement frequency is 1
When the frequency is selected to be GHz, the total length of the transmission line 21 is about 70 mm.
Therefore, there is a problem that a sufficient measurement range for measuring the electromagnetic radiation intensity distribution on a printed circuit board of a general electronic device cannot be obtained.

In the prior art, the signal selecting unit 1
Since the output of the device is directly extracted from a part of the transmission line 21 of the transmission line 9, the overall frequency characteristics of the wire loop antenna, the transmission line of the electromagnetic radiation detection unit row 4 and the signal selection unit 19 cannot be corrected, and There is a problem that it is difficult to obtain stable detection sensitivity over a frequency range.

According to the present invention, there is provided a circuit for improving the frequency characteristic of a signal selecting section for selecting an electromagnetic radiation detecting section row and for correcting the frequency characteristic between the output of the signal selecting section and the output terminal of the apparatus. Accordingly, an object of the present invention is to provide an electromagnetic radiation measuring device having stable detection sensitivity over a wide frequency band.

[0011]

According to the present invention, in order to achieve the above object, the output of each of the electromagnetic radiation detecting sections is selected by a switching diode, for example, in a first signal selecting section. Then, the output is output to a smaller number of output terminals than the number of columns, the output is selected by a switching diode via a transmission line in a second signal selector, and is output to a second output terminal. The selector is configured to select a switching diode via a transmission line, output the selected output to a third output terminal, and finally output the output to the output terminal of the device. Further, a circuit for correcting frequency characteristics is connected to the final output terminal of the device.

Therefore, according to the present invention, it is possible to prevent one end of the transmission line of the signal selection unit from being opened, so that the frequency characteristics of the signal selection unit can be improved, and the frequency characteristic correction circuit can be provided. Providing an electromagnetic radiation measurement device having stable detection sensitivity over a wide frequency band because the provision can correct the overall frequency characteristics of the small antenna element, the transmission line of each electromagnetic radiation detection unit, and the signal selection unit. Can be.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention according to claim 1 of the present invention is directed to a plurality of small antenna elements comprising a conductor pattern, a transmission line for transmitting an electric signal detected by the small antenna element, and a plurality of small antenna elements. And a switching means for electronically selecting the small antenna elements sequentially and connecting them to the transmission line. A first signal selection unit for selecting an output of each electromagnetic radiation detection unit by a first-stage switching element and outputting the output to an output contact having less than the number of columns, as means for selecting an electric output of the detection unit; The output of the first signal selector is connected to the
A second signal selecting section for selecting by a two-stage switching element and outputting less than the number of inputs to an output contact connected to the second-stage switching element; and a second signal selecting section similar to the second signal selecting section. A signal selector having a required number of stages is provided, and the outputs of the plurality of rows of electromagnetic radiation detectors are guided to a final output contact by following a single path with the output contact of each signal selector as a crossroad. Electromagnetic radiation detector connected to the output contact of
And a frequency characteristic correction circuit that corrects the overall frequency characteristic of the signal selection unit. One end of the transmission line of the signal selection unit can be prevented from being open. Therefore, the frequency characteristics of the signal selection unit can be improved.

According to a second aspect of the present invention, the first signal selecting section includes a first switching element having one end connected to an output terminal of the first electromagnetic radiation detecting section on the device end side. , The first
One end is connected to the output terminal of the second electromagnetic radiation detecting unit adjacent to the electromagnetic radiation detecting unit, and the other end is connected to the other end of the first switching element. and a second switching element connected to the first output terminal, the second signal selection unit, the first signal selector first output terminal <br/> is connected at one end to the other A first transmission line having one end connected to one end of the third switching element, and one end connected to the other end of the third switching element and to a first output terminal of the second signal selection unit; It is, and a fourth switching element whose other end is connected to one end of the second transmission line, the other end of the second transmission line
Is connected to another output terminal of the first signal selection unit, and it is possible to prevent one end of the transmission line of the signal selection unit from being open, so that the frequency characteristics of the signal selection unit Can be improved.

According to a third aspect of the present invention, an output terminal of each electromagnetic radiation detecting section and one output of the first signal selecting section are provided.
Two or more switching elements are connected between the first and second terminals, and two or more switching elements are connected between the plurality of output terminals of the first signal selector and one output terminal of the second signal selector. And can correspond to various printed circuit boards.

The invention according to a fourth aspect of the present invention is characterized in that a diode is used as a switching element, and the device can be reduced in size and power consumption.

[0017]

[0018]

(Embodiment 1) FIG. 1 is a block diagram showing a configuration of an electromagnetic radiation measuring apparatus according to a first embodiment of the present invention, and is generally on a multilayer printed circuit board having a thickness of about 4 mm. Formed. In FIG. 1, a wire loop antenna 1 formed of a copper foil pattern of about 6 to 7 mm formed on a printed circuit board, a transmission line 2 formed in an inner layer of the printed circuit board, and a switching surface-mounted on a surface layer of the printed circuit board. The diode 3 forms an electromagnetic radiation detecting section row 4. An electromagnetic radiation detection unit row 4 usually has two electromagnetic radiation detection units each composed of a combination of the wire loop antenna 1 and the switching diode 3.
About 0 to 40 pieces are arranged. The electromagnetic radiation detected by the wire loop antenna 1 is converted into an electric signal and applied to the transmission line 2 via the switching diode 3. The switching diode 3 is turned on by applying a voltage to the Y-direction control signal terminal 5. Then, only the wire loop antenna 1 at the selected position in the Y direction is electrically connected to the transmission line 2. Similarly, another Y-direction position can be selected by applying a voltage to another Y-direction control signal terminal. The terminating element 6 terminates the transmission line 2 at the characteristic impedance of the transmission line 2 (typically 50 ohms).

Next, the operation of the electromagnetic radiation measuring apparatus configured as described above will be described. An electromagnetic radiation detecting section 4 composed of a wire loop antenna 1, a transmission line 2, and a switching diode 3 is usually arranged in about 50 rows in the X direction, and an electromagnetic radiation detecting unit composed of a combination of the wire loop antenna 1 and the switching diode 3 is provided. 1000 to 2000 pieces are arranged in a matrix in the XY direction. The electromagnetic radiation intensity distribution of an object to be measured such as a printed circuit board can be measured by electronically sequentially selecting these electromagnetic radiation detection units and measuring the electromagnetic radiation level.

Here, the output terminal 7 of the electromagnetic radiation detecting section 4
Are arranged in about 50 columns in the X direction. These outputs are selected by the signal selection units 8, 11, and 15 and output from the output terminal 18 of the device to an external level meter or the like.

In the first signal selection section 8, the cathode of a switching diode 9a is connected to the output terminal 7 output from each electromagnetic radiation detection section row 4, and two anodes adjacent in sequence to the anode of the switching diode 9a. The output terminals of the radiation detection unit row 4 are connected to the anodes of the other switching diodes 9b and 9c whose cathodes are connected, respectively, and output as the output contact 10a of the first signal selection unit 8. One end of the transmission line 12a of the second signal selection unit 11 is connected to the output contact 10a of the first signal selection unit 8,
The other end of the transmission line 12a is connected to the switching diode 1
Connect to cathode of 3a. The anode of this switching diode 13a is connected to the anode of another switching diode 13b whose cathode is connected to another adjacent output contact 10b of the first signal selection unit 8, and the cathode is connected to another adjacent transmission line 12b. The other switching diode 13 c is connected to the other switching diode 13 c, and the signal is output as the output contact 14 of the second signal selector 11. Further, a third signal is connected to the output contact 14 of the second signal selection unit 11.
One end of the transmission line 16 of the signal selection unit 15 is connected, the other end of the transmission line 16 is connected to the cathode of the switching diode 17a, and an assode of the switching diode 17a is adjacent to the second signal selection unit 11. The third signal selection unit connects the anode of another switching diode 17b having a cathode connected to another output contact and the anode of another switching diode 17c having a cathode connected to another adjacent transmission line. Fifteen
And output to the output terminal 18 of the apparatus.

As described above, according to the first embodiment, the transmission lines of the signal selection units 8, 11, and 15 are:
Since the output of the electromagnetic radiation detector array 4 can be guided to the output terminal 18 of the device by following a single path with each of the output contacts 10 and 14 as a branch, any of the electromagnetic radiation detector arrays 4 is selected. Therefore, the transmission line characteristic of the signal selection unit is improved because a part of the transmission line does not become open at one end, and it is difficult to achieve a wide measurable range and a wide measurable frequency band in the related art. Can be solved.

In the first embodiment,
The output contact of the third signal selector 15 is connected to the output terminal 1 of the device.
8, the number of stages of the signal selection unit is increased,
That is, by providing the fourth, fifth,..., N-th signal selection units and connecting their outputs to the output terminal 18 of the device, the number of the electromagnetic radiation detection unit arrays 4 arranged in the X direction can be set to an arbitrary number. It is possible to respond. Further, in the first embodiment, the output contacts 10 of each of the signal selection units 8, 11, and 15,
Although the number of switching diodes commonly connected to the switching circuit 14 is three, the number is not limited to this, and is within a range in which the printed circuit board pattern length for the switching diode can be ignored with respect to the wavelength of the highest measurement frequency. , The number of which can be increased or decreased. Further, the signal switching element of the signal selection unit is not limited to a switching diode, and the same effect can be obtained by, for example, a high frequency switching element using a field effect transistor.

(Embodiment 2) FIG. 2 is a block diagram showing a configuration of an electromagnetic radiation measuring apparatus according to a second embodiment of the present invention. In FIG. 2, the multilayer printed circuit board 23 is
An antenna which constitutes an electromagnetic radiation detecting section and a signal selecting section in the first embodiment shown in FIG. 1 and is held by a housing 24 of the electromagnetic radiation measuring apparatus and detects electromagnetic radiation from an object 25 to be measured. Act as a unit. In the second embodiment, the output terminal 18 of the signal selection unit of the multilayer printed circuit board 23 is input to the input terminal 27 of the frequency characteristic correction circuit 26, and the frequency characteristic correction circuit 26 The total frequency characteristics of the electromagnetic radiation detecting section and the signal selecting section are corrected, and the corrected output 31 is output to an external measuring instrument via the output terminal 32 of the housing 24 of the electromagnetic radiation measuring apparatus. Is configured.

[0026] In the second embodiment, the frequency characteristic correcting circuit 26, amplified in the first stage from the input terminal 27 28
The signal input to is amplified by a flat gain over a wide frequency band in a practical frequency range, and the output is input to a filter circuit 29, and the frequency characteristics obtained by combining a low-pass filter and a high-pass filter are used to obtain a multilayer print. The electromagnetic amplifier is operated so as to reversely correct the total frequency characteristics of the electromagnetic radiation detecting section and the signal selecting section formed on the substrate 23, and the output thereof is amplified by the subsequent power amplifier 30 with flat gain over a wide frequency band. It is configured to output.

FIG. 3 is a graph showing how the frequency characteristic correction circuit 26 corrects the total frequency characteristics of the electromagnetic radiation detection section and the signal selection section. The horizontal axis corresponds to the frequency, and the vertical axis corresponds to the output level of each section. I do. In FIG. 3, the solid line 33
3 is a graph showing an output level versus frequency characteristic of an output terminal 18 of an electromagnetic radiation detection unit and a signal selection unit configured on the multilayer printed circuit board 23 in FIG. At this time, in the object 25 to be measured, electromagnetic radiation is generated by flowing a constant current (about 10 μA) at each frequency through a constant printed circuit board pattern, and the electromagnetic radiation is generated on the multilayer printed circuit board 23. The level detected and output by the detection unit and the signal selection unit is measured. As shown in the example of the solid line 33, in this type of electromagnetic radiation measuring apparatus, 6
The output of the near magnetic field detection by a wire loop antenna of about 7 to 7 mm is directly connected to a transmission line of constant impedance and transmitted, so that at a relatively low frequency of about 10 to 100 MHz, about 6 dB / oct. The output increases in proportion to the frequency with the slope of. At frequencies above about 200 MHz,
Due to the characteristics of the transmission line and the effects of the off-state capacitance and stray capacitance of the switching diode, the frequency characteristics become almost flat. In the example of FIG. 3, the practical frequency range is up to about 1500 MHz , and this practical frequency range is wide. Band
Over the frequency characteristics. This is the case of the configuration of the signal selection unit in the first embodiment (FIG. 1) of the present invention. In the example of FIG. 4 in the related art, although it depends on the size and type of the device, generally, since the influence of the transmission line one open end of the signal selector, the practical upper limit
Frequency is suppressed to about 800MHz.

It is necessary to measure the level of such a weak output signal in a wide frequency band having an amplitude range of 30 dB or more using an external measuring instrument (level detector, generally a receiver or a spectrum analyzer). Because there is
The amplifier having a frequency characteristic correction function in the path of outputting the output to the outside, by performing <br/> wideband amplification with correcting the frequency characteristics, has a stable detection sensitivity cotton a wide frequency band And the performance of the entire electromagnetic radiation system can be improved.

In FIG. 3, a dotted line 34 shows an example of a result obtained by amplifying the output of the solid line 33 through the frequency characteristic correction circuit 26 together with the frequency characteristic correction. The gain is set so as to have a frequency characteristic in a range of about 18 to 40 dB, and the output level is stabilized in a fluctuation range of about 10 dB around about -70 dBm.

The configuration of the frequency characteristic correction circuit 26 is not limited to the one described in the above embodiment, and other configurations can correct the total frequency characteristics of the electromagnetic radiation detection section and the signal selection section. A similar effect can be obtained.

[0031]

According to the present invention, as is apparent from the above embodiment, it is possible to prevent one end of the transmission line of the signal selection unit from being open, so that the frequency characteristics of the signal selection unit can be improved. In addition, by providing a frequency characteristic correction circuit, it is possible to correct the overall frequency characteristics of the small antenna element, the transmission line of each electromagnetic radiation detection unit row, and the signal selection unit, so that it is stable over a wide frequency band in a practical frequency range. An electromagnetic radiation measuring device having improved detection sensitivity can be provided.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an electromagnetic radiation measuring device according to a first embodiment of the present invention.

FIG. 2 is a block diagram illustrating a schematic configuration of an electromagnetic radiation measurement device including a frequency characteristic correction circuit according to a second embodiment of the present invention.

FIG. 3 is a characteristic diagram showing an output level versus frequency characteristic according to the second embodiment of the present invention.

FIG. 4 is a block diagram showing a configuration of an electromagnetic radiation measuring device according to the related art.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Wire loop antenna 2 Transmission line 3 Switching diode 4 Electromagnetic radiation detection part row 5 Y direction control signal terminal 6 Termination element 7 Output terminal 8 First signal selection part 9a, ... Switching diode 10a, ... of the first signal selection part Output contact 11 Second signal selector 12a,... Transmission line 13a,... Switching diode 14a,... Output contact of second signal selector 15 Third signal selector 16 Transmission line 17a,. terminal 19 signal selection unit 20 switching diode 21 transmission line 22 device output terminal 23 MLB 24 electromagnetic radiation measuring apparatus of the casing 25 the measurement object 26 the frequency characteristic correcting circuit 27 input terminal 28 amplifier 29 filter circuit 30 power Amplifier 31 Output terminal 32 Electromagnetic radiation measurement system Graph showing the output terminal 33 Output level versus frequency characteristic systems out (uncorrected) 34 a graph showing an output level versus frequency characteristic (corrected)

Claims (4)

(57) [Claims] 1. A plurality of small antenna elements formed of a conductor pattern, a transmission line for transmitting an electric signal detected by the small antenna elements, and a plurality of small antenna elements electronically sequentially selected and transmitted. In an electromagnetic radiation measuring device having a plurality of rows of electromagnetic radiation detectors provided on a multilayer printed circuit board and having a switching unit connected to a line, each of the electromagnetic radiation detectors is provided as means for selecting an electric output of the plurality of rows of electromagnetic radiation detectors. A first signal selection unit that selects an output of the detection unit by the first-stage switching element and outputs the output to an output contact having less than the number of columns, and an output of the first signal selection unit via a transmission line. A second signal selecting section for selecting by a two-stage switching element and outputting less than the number of inputs to an output contact connected to the second-stage switching element; and a second signal selecting section similar to the second signal selecting section. With configuration The required number of stages, the output of the plurality of rows of electromagnetic radiation detectors is guided to a final output contact by following a single path with the output contact of each signal selector as a crossroad, and the final output An electromagnetic radiation measuring device, comprising: a frequency characteristic correction circuit connected to a contact for correcting an overall frequency characteristic of an electromagnetic radiation detection unit and a signal selection unit. 2. A first signal selector, comprising: a first signal selector on a device end side;
A first switching element having one end connected to the output terminal of the electromagnetic radiation detecting section, and a second switching element adjacent to the first electromagnetic radiation detecting section.
One end is connected to the output terminal of the electromagnetic radiation detecting section, and the other end is connected to the other end of the first switching element.
And a second switching element connected to a first output terminal of the signal selection section, wherein the second signal selection section has one end connected to a first output terminal of the first signal selection section. A first transmission line having the other end connected to one end of the third switching element, and a first output terminal of the second signal selection section having one end connected to the other end of the third switching element. And a fourth switching element having the other end connected to one end of the second transmission line,
The electromagnetic radiation measuring device according to claim 1, wherein the other end of the second transmission line is connected to another output terminal of the first signal selector. 3. Two or more switching elements are connected between an output terminal of each electromagnetic radiation detection unit and one output terminal of the first signal selection unit, and a plurality of switching elements are connected to the plurality of output terminals of the first signal selection unit. The electromagnetic radiation measuring apparatus according to claim 2, wherein two or more switching elements are connected to one output terminal of the second signal selector. 4. The electromagnetic radiation measuring apparatus according to claim 1, wherein a diode or a transistor is used as the switching element.