JP2009115644A - Electric field probe, electric field measurement apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric field probe and an electric field measurement apparatus having an isotropic directional characteristic, and the high electric field detection sensitivity. <P>SOLUTION: The electric field probe 20 includes: three electric field sensors (10x, 10y, 10z) disposed so as to be oriented in three orthogonal directions; three filters (21x, 21y, 21z) for attenuating an image frequency component from high frequency signals generated in power supplying sections (13x, 13y, 13z) of three electric field sensors; three mixers (22x, 22y, 22z) for converting the high frequency signals with the attenuated image frequency component into intermediate frequency signals by using an oscillation signal generated from a local oscillator (23); and three connectors (24x, 24y, 24z) for outputting the converted intermediate frequency signals. The electric field measurement apparatus 100 has the electric field probe 20. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an electric field probe and an electric field measurement device used for measuring the intensity of electromagnetic waves radiated from an electronic device or a radio station. In particular, the present invention relates to an electric field probe and an electric field measurement device having equal electric field detection sensitivity in all directions in a frequency band of 3 GHz or more.

  An electric field probe 90 that can be used in a frequency band of 3 GHz or higher will be described with reference to FIG. 11 (see, for example, Non-Patent Document 1). The electric field probe 90 is a so-called conical dipole antenna, and includes two conical radiating elements 91 and 91 ′, a balun 92, and a coaxial line 93. The cone radiating elements 91 and 91 ′ are arranged at positions that form an angle of 180 degrees with each other, and a gap is provided between the cone radiating elements 91 and 91 ′. The coaxial line 93 feeds the electric field probe 90 in the gap. A balun 92 is provided in the power feeding portion to prevent unbalanced current.

An electric field probe used for measuring the intensity of electromagnetic waves such as unnecessary electromagnetic waves needs to have a wide frequency range such as 3 GHz to 6 HGz. For this reason, the electric field probe 90 expands the frequency range by using conical cone radiating elements 91 and 91 ′ instead of the columnar radiating elements.
The Institute of Electronics, Information and Communication Engineers, “Antenna Engineering Handbook”, first edition, Ohm Co., Ltd., January 25, 2001, p. 39

Since the electric field probe 90 of the prior art is a kind of dipole antenna, its directivity characteristic is a figure 8 shape and is not isotropic. Further, when measuring the intensity of a high frequency electromagnetic wave of 3 GHz or higher, a high frequency signal of 3 GHz or higher passes through the coaxial line 93 as it is, so that there is a problem that the loss of the cable increases and the electric field detection sensitivity decreases. .
An object of the present invention is to provide an electric field probe and an electric field measuring device that have isotropic directivity and high electric field detection sensitivity.

  The electric field probe according to claim 1 is generated in the power feeding section of the three electric field sensor elements using three electric field sensor elements arranged in three directions orthogonal to each other and an oscillation signal oscillated from the local oscillator. Three mixers for converting each high-frequency signal into an intermediate frequency signal, and three connectors for outputting each converted intermediate frequency signal, respectively.

  The electric field measuring apparatus according to claim 5 is an electric field probe for obtaining electric field strengths in three directions from an electric field probe and an intermediate frequency signal output from the electric field probe, and obtaining electric field strengths at the position of the electric field probe from these obtained electric field strengths. An intensity calculating means and a helically wound coaxial line connecting the electric field probe and the electric field intensity calculating means are provided.

  The electric field measuring apparatus according to claim 7 is provided with three electric field sensor elements arranged in three directions orthogonal to each other, light emitting means for emitting light, and each high frequency generated in a power feeding portion of the three electric field sensor elements. By modulating the light based on the signals, the three Mach-Zehnder optical modulators that convert and output each high-frequency signal to an optical signal, and the optical signals output by the three Mach-Zehnder optical modulators are converted into electrical signals. Using the light receiving means for conversion, the mixer device that lowers the frequency of the electric signal using the oscillation signal oscillated from the local oscillator, the electric field strength in three directions is obtained from the electric signal whose frequency is lowered, and these are obtained. Electric field strength calculating means for obtaining the electric field strength at the position of the electric field probe from the measured electric field strength.

  By arranging three electric field sensor elements in three directions orthogonal to each other, the directivity characteristic of the electric field probe becomes isotropic. By converting the high-frequency signal generated in the power supply section of the electric field sensor element into an intermediate frequency signal and outputting it, or by converting the high-frequency signal generated in the power supply section of the electric field sensor element into an optical signal and outputting it, the cable Loss can be reduced, and the electric field detection sensitivity can be increased.

[First embodiment]
The electric field probe 20 and the electric field measurement apparatus 100 according to the first embodiment will be described with reference to FIGS.
The electric field measurement apparatus 100 includes an electric field probe 20, coaxial lines 31x, 31y, and 31z, and an electric field strength calculation unit 40.

  In this example, the electric field probe 20 is formed based on a rectangular parallelepiped metal box 12 as illustrated in FIG. An x-axis electric field sensor element 10x, a y-axis electric field sensor element 10y, and a z-axis electric field sensor element 10z are provided on three surfaces of the rectangular parallelepiped metal box 12. Hereinafter, the direction in which the x-axis electric field sensor element 10x is directed is the x-axis direction, the direction in which the y-axis electric field sensor element 10y is directed is the y-axis direction, and the direction in which the z-axis electric field sensor element 10z is directed is z. Axial direction. The x-axis direction, the y-axis direction, and the z-axis direction are orthogonal to each other.

  As illustrated in FIG. 3, a hole is formed in the central portion of the metal plate 12 x that is one of the surfaces of the metal box 12. The x-axis cone radiating element 11x is arranged at the position where the hole is formed so as not to contact the metal plate 12x. The central axis of the x-axis cone radiating element 11x is substantially orthogonal to the metal plate 12x. The metal plate 12x functions as a reflecting plate. The x-axis cone radiating element 11x is connected to an inner conductor of a coaxial line (not shown), and the metal plate 12x is connected to an outer conductor of the coaxial line. The coaxial line is connected to the x-axis filter 21x. In this way, the x-axis electric field sensor element 10 is configured in which the position where the hole is formed is the power feeding portion 13x. Thus, in this example, a conical monopole antenna having a conical radiation element is used as the electric field sensor element.

The y-axis electric field sensor element 10y and the z-axis electric field sensor element 10z are configured similarly to the x-axis electric field sensor 10x. The z-axis electric field sensor element 10z is arranged in a direction perpendicular to the paper surface of FIG. FIG. 1 is a top view of the electric field probe 20 illustrated in FIG.
A high-frequency signal generated in the power feeding unit 13x of the x-axis electric field sensor element 10x is sent to the x-axis filter 21x through a coaxial line. The x-axis filter 21 is provided to prevent image reception, and attenuates an image frequency component from the high-frequency signal. The high-frequency signal having the image frequency component attenuated is output to the x-axis mixer 22x.

For example, when the frequency of the electric field to be measured is 3 GHz to 6 GHz and the oscillation frequency of the local oscillator 23 is 2.9 GHz, the x-axis filter 21 is a high-pass filter having a cutoff frequency of 2.9 GHz. To do.
Similarly to the x-axis filter 21x, the y-axis filter 21y and the z-axis filter 21z are connected to the y-axis electric field sensor element 10y and the z-axis electric field sensor element 10z, and attenuate the image frequency component from the high-frequency signal. Output to the y-axis mixer 22y and the z-axis mixer 22z.
The local oscillator 23 generates an oscillation signal having a predetermined oscillation frequency and sends it to the x-axis mixer 22x, the y-axis mixer 22y, and the z-axis mixer 22z. The oscillation frequency is, for example, 2.9 GHz.

The x-axis mixer 22x converts the high-frequency signal output from the x-axis filter 21x into an intermediate frequency signal using the oscillation signal oscillated by the local oscillator 23, and outputs the intermediate frequency signal to the x-axis IF output connector 24x. Specifically, an intermediate frequency signal is generated by multiplying the oscillation signal and the high frequency signal. _Assuming that the frequency of the high-frequency signal generated in the power feeding section of the x-axis electric field sensor element 10x is f _{RF —} x and the frequency of the oscillation signal is f _L , the frequency of the intermediate frequency signal output from the x-axis mixer 22 x is f _{IF — x} as follows: It is expressed in
f _{IF_x} = f _{RF_x} -f _L

  Similarly to the x-axis mixer 22x, the y-axis mixer 22y and the z-axis mixer 22z use the oscillation signal oscillated by the local oscillator 23 to convert the high-frequency signals output from the y-axis filter 21y and the z-axis filter 21z into intermediate frequency signals. The data is converted and output to the y-axis IF output connector 24y and the z-axis IF output connector 24z.

The frequency of the high-frequency signal generated in the power feeding part of the y-axis electric field sensor element 10y is f _{RF_y} , the frequency of the high-frequency signal generated in the power feeding part of the z-axis electric field sensor element 10z is f _{RF_z} , and the frequency of the oscillation signal is f _L , y When the frequency of the intermediate frequency signal frequency of the intermediate frequency signal axis mixer 22y outputs the _{f IF_Y} and z-axis mixer 22z outputs and _{f IF_z, f IF_y} and _{f IF_z} is expressed as follows.
f _{IF_y} = f _{RF_y} −f _L
f _{IF_z} = f _{RF_z} −f _L
The x-axis IF output connector 24 x outputs the intermediate frequency signal generated by the x-axis mixer 22 x from the electric field probe 20. The same applies to the IF output connector 24y and the z-axis IF output connector 24z.

The coaxial line 31x connects the x-axis IF output connector 24x and the electric field strength calculation unit 40, and sends the intermediate frequency signal output from the x-axis IF output connector 24x to the electric field strength calculation unit 40. The same applies to the coaxial line 31y and the coaxial line 31z.
The electric field intensity calculation unit 40 determines the electric field intensity in the direction in which the x-axis electric field sensor element 10x, the y-axis electric field sensor element 10y, and the z-axis electric field sensor element 10z are directed from the three intermediate frequency signals output from the electric field probe 20. E _x , E _y , and E _z are obtained, and the electric field strength E at the position of the electric field probe 20 is obtained from the obtained electric field strengths E _x , E _y , and E _z . FIG. 4 illustrates a functional configuration of the electric field intensity calculation unit 40.

When the antenna coefficient of the x-axis electric field sensor element 10x is AF _cx [dB / m], the insertion loss of the filter of the x-axis filter 21x is L [dB], and the conversion gain of the x-axis mixer 22x is G _mix [dB], x The total antenna coefficient AF _x of the axial electric field sensor element 10x can be expressed as follows.
AF _x [dB / m] = AF _cx [dB / m] + L [dB] −G _mix [dB]
Therefore, the electric field intensity E _x in the x-axis direction can be expressed as follows, where V _x [dBV] is a voltage generated in the x-axis IF output connector 24x.
E _x [dBV / m] = AF _x [dB / m] + V _x [dBV] (1)
x-axis field strength calculation unit 41x, based on the equation (1), by calculating the electric field strength E _x in the x-axis direction, and sends to the overall field strength calculation unit 42.

Similarly, assuming that the antenna coefficient of the y-axis electric field sensor element 10y is AF _cy [dB / m] and the antenna coefficient of the z-axis electric field sensor element 10z is AF _cz [dB / m], the overall antenna of the y-axis electric field sensor element 10y. The coefficient AF _y and the total antenna coefficient AF _z of the z-axis electric field sensor element 10z are as follows.
AF _y [dB / m] = AF _cy [dB / m] + L [dB] −G _mix [dB]
AF _z [dB / m] = AF _cz [dB / m] + L [dB] −G _mix [dB]

Therefore, the electric field intensity _E y in the y-axis direction, the electric field strength _{E z} in the z-axis direction, a voltage generated in the y-axis IF output connector 24y _V y [dBV], the voltage generated in z-axis IF output connector 24z V Assuming _z [dBV], it can be expressed as follows.
E _y [dBV / m] = AF _y [dB / m] + V _y [dBV] (2)
E _z [dBV / m] = AF _z [dB / m] + V _z [dBV] (3)
The y-axis field strength calculation unit 41y and the z-axis field strength calculation unit 41z calculate the field strength E _{y in the y-} axis direction and the field strength E _z in the z-axis direction based on the above formulas (2) and (3). To the total electric field strength calculation unit 42.

Since the x-axis direction, the y-axis direction, and the z-axis direction are orthogonal to each other, the electric field intensity E at the position of the electric field probe 20 can be expressed as follows.
E ² = E _x ² + E _y ² + E _z ²
E = (E _x ² + E _y ² + E _z ² ) ^1/2 (4)
The total electric field strength calculation unit 42 calculates the electric field strength E based on the above formula (4).

As described above, the electric field probe 20 has three electric field sensor elements (x-axis electric field sensor element 10x, y-axis electric field sensor element) oriented in three directions (x-axis direction, y-axis direction, and z-axis direction) orthogonal to each other. 10y, z-axis electric field sensor element 10z), the electric field strengths E _x , E _y , E _z in each direction can be obtained. Then, by obtaining the electric field intensity E at the position of the electric field probe 20 from the electric field intensity E _x , E _y , E _z in each direction, the electric field can be measured isotropically. The electric field probe 20 is an isotropic electric field probe.

  Further, by converting the high frequency signal generated at the power feeding portion of each electric field sensor element 10x, 10y, 10z into an intermediate frequency signal and outputting the intermediate frequency signal from the electric field probe 20, the coaxial lines 31x, 31y, 31z The loss of the cable can be reduced, and the electric field detection sensitivity can be increased.

[Second Example]
The second embodiment differs from the first embodiment in that a slot antenna is used as an electric field sensor element instead of a conical monopole antenna having a conical radiation element. Further, the second embodiment is different from the first embodiment in that a filter for attenuating the image frequency component signal is not provided. Other points are the same as in the first embodiment.
With reference to FIGS. 5 to 6, the electric field probe 20 ′ and the electric field strength measuring apparatus 101 of the second embodiment will be described. The same parts as those in FIG. The same applies to the other drawings.

  The electric field probe 20 ′ is formed based on a rectangular parallelepiped metal box 12 as illustrated in FIG. 6, and an x-axis electric field sensor which is a butterfly-shaped slot antenna on each of three surfaces of the rectangular parallelepiped metal box 12. An element 10x ′, a y-axis electric field sensor element 10y ′, and a z-axis electric field sensor element 10z ′ are provided. In this example, the frequency characteristics of the electric field sensor element are made flatter by making the shape of the slot a butterfly shape and a bow tie shape.

The x-axis electric field sensor element 10x ′ is supplied with power at the center of the slot. Specifically, a pair of protrusions are provided on the inner side of the slot so that the width of the slot becomes narrower toward the center, and the ends of the pair of protrusions are located at the center of the slot via a gap. Facing each other. By connecting one conductor of the coaxial line to the tip of one protrusion and connecting the other conductor of the coaxial line to the tip of the other protrusion, the x-axis electric field sensor element 10x ′ is fed. The coaxial line is connected to the x-axis mixer 22x.
The y-axis electric field sensor element 10y ′ and the z-axis electric field sensor element 10z ′ are also fed in the same manner as the x-axis electric field sensor element 10x ′.

The slot antenna has a property of reducing a signal having a low frequency outside the design frequency. Here, when the oscillation frequency of the local oscillator 23 is lower than the frequency of the electric field to be measured, since the image frequency is lower than the oscillation frequency, the image frequency component signal is attenuated by the slot antenna. Therefore, the electric field probe 20 ′ and the electric field measurement device 101 of the second embodiment can prevent image reception even if the x-axis filter 21x, the y-axis filter 21y, and the z-axis filter 21z are not provided.
In the second embodiment, the same effects as in the first embodiment can be obtained.
In this example, a butterfly slot antenna is used as the electric field sensor, but any slot antenna other than the butterfly may be used.

[Third embodiment]
As illustrated in FIG. 7, the electric field measurement apparatus 102 according to the third embodiment includes helically wound coaxial lines 32 x, 32 y, and 32 z as coaxial lines that connect the electric field probe 20 and the electric field strength calculation unit 40. It differs from the electric field measuring apparatus 100 of the first embodiment in that it is used. Other points are the same as those of the electric field measuring apparatus 100 of the first embodiment.

  The self-inductance can be increased by making the coaxial lines 32x, 32y, and 32z spiral. The reactance increases due to the increase of the self-inductance, and the impedance of the coaxial lines 32x, 32y, 32z increases. Due to this increase in impedance, the common mode current can be reduced. By reducing the common mode current, it is possible to reduce the influence of disturbance caused by the coaxial line on the electric field of the frequency to be measured. Thereby, the intensity of the electric field at the frequency to be measured can be measured more accurately.

The pitch p, which is the winding interval of the coaxial lines 32x, 32y, 32z, may be constant or variable.
When the pitch p that is the winding interval of the coaxial lines 32x, 32y, and 32z is made constant, the pitch p is selected so that the impedance of the coaxial lines 32x, 32y, and 32z is sufficiently high in the range of the frequency to be measured. The
In the example shown in FIG. 7, the electric field probe 20 of the first embodiment is used as the electric field probe, but the electric field probe 20 ′ of the second embodiment may be used. Only one or two of the coaxial lines 32x, 32y, and 32z may be helically wound.

[Fourth embodiment]
As illustrated in FIG. 8, the fourth embodiment is a third embodiment in that the pitch of the helically wound coaxial lines 33x, 33y, 33z is not a constant pitch but a logarithmic period. Is different. Other points are the same as in the third embodiment.

  By making the pitch of the helically wound coaxial lines 33x, 33y, and 33z logarithmic, the frequency range in which the impedance of the coaxial lines 33x, 33y, and 33z increases is wider than when the pitch is made constant. can do. Thereby, the common mode current can be reduced in a wider frequency range, and the electric field strength of the frequency to be measured can be measured more accurately.

  To make the pitch of a helically wound coaxial line logarithmic period, a plurality of frequencies are selected in a logarithmic period in a frequency range in which the common mode current is to be reduced, and the selected plurality of frequencies (hereinafter, A plurality of pitches are determined based on the frequency of interest) so that the helically wound coaxial line has at least the plurality of pitches.

For example, when the frequency range to be measured is 3 GHz to 50 GHz, the frequency of interest is 3 GHz, 4 GHz,..., 8 GHz, 9 GHz, 10 GHz, 20 GHz, 30 GHz, 40 GHz, 50 GHz. Then, a plurality of pitches are obtained so as to be inversely proportional to these frequencies of interest. That is, the frequency of interest _{f i (i = 1, ...} , n), as an arbitrary constant a, a plurality of pitch _{p i,} determined as p _i = a / _f i. In the above example, n = 12. The helically wound coaxial line has a plurality of pitches p _i (i = 1,..., N). That is, the pitch of the portion of the coaxial line is in the helical shape is p _1, the pitch of another part is p _2, the pitch of a further moiety is p _3, ..., yet another portion the pitch is _{p n.}

FIG. 8 illustrates a case where the coaxial lines 33x, 33y, and 33z have at least three different pitches p ₁ , p ₂ , and p ₃ . In this example, only one pitch is continued, the pitch p ₁ is next to the pitch p ₂ , and the pitch p ₂ is the pitch p _3. However, a plurality of pitches may be continued. . That is, a plurality of pitches p ₁ may be followed by a plurality of pitches p ₂ , followed by a plurality of pitches p ₃ .

The frequency of interest and the constant a are determined experimentally so that the electric field strength of the frequency to be measured can be measured more accurately.
In the example shown in FIG. 8, the electric field probe 20 of the first embodiment is used as the electric field probe, but the electric field probe 20 ′ of the second embodiment may be used. Only one or two of the coaxial lines 33x, 33y, 33z may be wound in a logarithmic cycle pitch.

[Fifth Example]
In the fifth embodiment, as illustrated in FIG. 9, the electric field probe 20 ″ includes Mach-Zehnder type optical modulators 52x, 52y, and 52z, and the high-frequency signal generated in the power feeding section of each electric field sensor element is an optical signal. This is different from the first embodiment in that it is converted into and output. Other points are the same as in the first embodiment.

The light emitting means 51 includes three laser diodes (x-axis laser diode 51x, y-axis laser diode 51y, z-axis laser diode 51z).
The x-axis laser diode 51x is a light source of an x-axis Mach-Zehnder optical modulator 52x described later, and emits a continuous wave that is not modulated in amplitude and phase. The emitted light passes through the x-axis first optical fiber cable 61x and enters the x-axis Mach-Zehnder optical modulator 52x.

  Similarly to the x-axis laser diode 51x, the y-axis laser diode 51y and the z-axis laser diode 51z also pass through the y-axis first optical fiber cable 61y and the z-axis first optical fiber cable 62z. Light is emitted to the z-axis Mach-Zehnder optical modulator 52z.

  The electric field probe 20 ″ includes an x-axis Mach-Zehnder type optical modulator 52 x that converts a high-frequency signal generated by the power feeding unit 13 x of the x-axis electric field sensor element into an optical signal and outputs the optical signal. In the power feeding unit 13x, one electrode of the x-axis Mach-Zehnder optical modulator 52x is connected to the x-axis conical radiation element 11x, and the other electrode is connected to the metal plate 12x. The x-axis Mach-Zehnder optical modulator 52x modulates the light emitted from the x-axis laser diode 51 in accordance with the high-frequency signal generated by the power feeding unit 13x of the x-axis electric field sensor element. The modulated light passes through the x-axis second optical fiber cable 62x and enters the x-axis photodiode 53x.

The electric field probe 20 ″ includes a y-axis Mach-Zehnder optical modulator 52y and a z-axis Mach-Zehnder optical modulator 52z similar to the x-axis Mach-Zehnder optical modulator 52x.
The light receiving means 53 includes three photodiodes (x-axis photodiode 53x, y-axis photodiode 53y, and z-axis photodiode 53z).

  The x-axis photodiode 53x converts the optical signal output from the x-axis Mach-Zehnder optical modulator 52x into an electrical signal. Specifically, the light intensity modulated wave emitted from the x-axis Mach-Zehnder type optical modulator 52x is detected, and a current including the frequency component of the high-frequency signal generated at the power feeding portion of the x-axis electric field sensor element 10x is output.

  Similarly to the x-axis photodiode, the y-axis photodiode 53y and the z-axis photodiode 53z convert the optical signals output from the y-axis Mach-Zehnder optical modulator 52y and the z-axis Mach-Zehnder optical modulator 52z into electrical signals.

  The x-axis mixer 22x uses the oscillation signal oscillated by the local oscillator 23 to lower the frequency of the electrical signal output by the x-axis photodiode 53x so that the electric field intensity calculation unit 40 can calculate the electric field intensity. To do. Specifically, the oscillation signal and the electric signal are multiplied and output to the electric field strength calculation unit 40. The y-axis mixer 22y and the z-axis mixer 22z are the same as the x-axis mixer 22x.

The electric field strength calculation unit 40 obtains the electric field strengths in the three directions from the electric signals output from the x-axis mixers 22x, 22y, and 22z, and obtains the electric field strength at the position of the electric field probe from these obtained electric field strengths. . In the electric field intensity calculation unit 40 of the fourth embodiment, only the definition formulas of AF _x [dB / m], AF _y [dB / m], and AF _z [dB / m] described below are different. Other parts are the same as those described in the first embodiment with reference to FIG.

The antenna coefficient of the x-axis electric field sensor element 10x is AF _cx [dB / m], the conversion gain of the x-axis Mach-Zehnder optical modulator 52x is G _m [dB], and the conversion gain of the x-axis photodiode 53x is G _f [dB]. If the conversion gain of the x-axis mixer 22x is G _mix [dB], the total antenna coefficient AF _x of the x-axis electric field sensor element 10x can be expressed as follows.
AF _x [dB / m] = AF _cx [dB / m] −G _m [dB] −G _f [dB] −G _mix [dB] (5)
x-axis field strength calculation unit 41x, the above equation (5), based on the above equation (1) described in the first embodiment, calculates the electric field intensity E _x in the x-axis direction, overall field strength calculation Send to part 42.

Similarly, the antenna coefficient of the y-axis electric field sensor element 10y is AF _cy [dB / m], the antenna coefficient of the z-axis electric field sensor element 10z is AF _cz [dB / m], and the conversion gain of the y-axis Mach-Zehnder optical modulator 52y. G _m [dB], the conversion gain of the z-axis Mach-Zehnder optical modulator 52z is G _m [dB], the conversion gain of the y-axis photodiode 53y is G _f [dB], and the conversion gain of the z-axis photodiode 53z is G _When the conversion gain of _f [dB], the y-axis mixer 22y is G _mix [dB], and the conversion gain of the z-axis mixer 22z is G _mix [dB], the total antenna coefficient AF _y , z-axis of the y-axis electric field sensor element 10y The total antenna coefficient AF _z of the electric field sensor element 10z can be expressed as follows.
AF _y [dB / m] = AF _cy [dB / m] −G _m [dB] −G _f [dB] −G _mix [dB] (6)
AF _z [dB / m] = AF _cz [dB / m] −G _m [dB] −G _f [dB] −G _mix [dB] (7)

The y-axis electric field strength calculation unit 41y calculates the electric field strength E _y in the y-axis direction based on the above formula (6) and the above formula (1) described in the first embodiment, thereby calculating the total electric field strength calculation. Send to part 42.
The z-axis electric field strength calculation unit 41z calculates the electric field strength E _z in the z-axis direction based on the above formula (7) and the above formula (1) described in the first embodiment, thereby calculating the total electric field strength calculation. Send to part 42.
The total electric field strength calculation unit 42 calculates the electric field strength E based on the above formula (4) as in the first embodiment.

  If a metal wire is used for the power supply line of the electric field probe as in the first to fourth embodiments, a common mode current may be generated and the electric field distribution may be disturbed. However, as in the fifth embodiment, by using an optical fiber cable for the feed line of the electric field probe, disturbance of the electric field distribution can be prevented and accurate electric field strength can be measured.

  The electric field probe 20 '' and the electric field measuring device 104 of the fifth embodiment are isotropic because they have three electric field sensor elements oriented in three directions orthogonal to each other, as in the first embodiment. is there. Furthermore, by converting each high-frequency signal generated in the power supply portion of the electric field sensor element into an optical signal and outputting it, the loss of the cable can be reduced and the electric field detection sensitivity can be increased.

  In this example, the electric field sensor elements of the first embodiment (x-axis electric field sensor element 10x, y-axis electric field sensor element 10y, z-axis electric field sensor element 10z) are used as the electric field sensor elements of the electric field probe 20 ′ ″. However, the electric field sensor elements of the second embodiment (x-axis electric field sensor element 10x ′, y-axis electric field sensor element 10y ′, z-axis electric field sensor element 10z ′) may be used.

[Sixth embodiment]
In the sixth embodiment, as illustrated in FIG. 10, the light emitting means 51 is composed of one laser diode 510, the light receiving means 53 is composed of one photodiode 530, and the electric field probe 20 ′ ″ is the first optical switch 71. The second embodiment is different from the fifth embodiment in that the second optical switch 72 and the control unit 73 are provided. The other points are the same as in the fifth embodiment.

The laser diode 510 is a light source of the x-axis Mach-Zehnder optical modulator 52x, the y-axis Mach-Zehnder optical modulator 52y, and the z-axis Mach-Zehnder optical modulator 52z, and emits a continuous wave that is not modulated in amplitude and phase. . The emitted light passes through the optical fiber cable 61 and enters the first optical switch.
The first optical switch 71 emits the incident light to any one of the x-axis Mach-Zehnder optical modulator 52x, the y-axis Mach-Zehnder optical modulator 52y, and the z-axis Mach-Zehnder optical modulator 52z. As the first optical switch 71, any optical switch such as a mechanical type, a MEMS type, and a waveguide type can be used.

Of the x-axis Mach-Zehnder optical modulator 52x, the y-axis Mach-Zehnder optical modulator 52y, and the z-axis Mach-Zehnder optical modulator 52z, the Mach-Zehnder optical modulator that receives light from the first optical switch 71 is an electric field sensor. The light is modulated in accordance with the high-frequency signal generated in the power feeding portion of the element and emitted to the second optical switch 72. That is, the high frequency signal is converted into an optical signal and output to the second optical switch 72.
The second optical switch 72 outputs an optical signal output from any of the x-axis Mach-Zehnder optical modulator 52x, the y-axis Mach-Zehnder optical modulator 52y, and the z-axis Mach-Zehnder optical modulator 52z to the photodiode 530.

  Specifically, the second optical switch 72 is linked to the first optical switch 71 and is connected to a Mach-Zehnder optical modulator to which the first optical switch 71 is connected. For example, when the first optical switch 71 is connected to the x-axis Mach-Zehnder optical modulator 52x, the second optical switch 72 is also connected to the x-axis Mach-Zehnder optical modulator 52x. Control of the interlocking between the first optical switch 71 and the second optical switch 72 is performed by the control unit 73.

  Thereby, the second optical switch 72 emits the light emitted from the Mach-Zehnder optical modulator connected to the first optical switch 71 to the photodiode 530. As the second optical switch 72, any optical switch such as a mechanical type, a MEMS type, and a waveguide type can be used.

The control unit 73 sequentially switches between the first optical switch 71 and the second optical switch 72. As a result, the optical signals corresponding to the three electric field sensor elements (the x-axis electric field sensor element 10x, the y-axis electric field sensor element 10y, and the z-axis electric field sensor element 10z) are time-divided and output to the photodiode 530.
The photodiode 530 converts the input optical signal into an electrical signal and outputs the electrical signal. In other words, the time-division optical signal is converted into a time-division electric signal and output.

  The mixer 22 uses the oscillation signal oscillated by the local oscillator 23 to lower the frequency of the electric signal output from the photodiode 530 so that the electric field intensity calculator 40 can calculate the electric field intensity. Specifically, the oscillation signal and the electric signal are multiplied and output to the electric field strength calculation unit 40.

In the same manner as in the fifth embodiment, the electric field intensity calculation unit 40 determines the electric field intensities E _x , E _y , E _{z in the} x-axis direction, the y-axis direction, and the z-axis direction from the input time-divided electric signal. And the electric field strength E at the position of the electric field probe 20 ′ ″ is obtained from these obtained electric field strengths.

  In the sixth embodiment, the number of parts is reduced compared to the fifth embodiment by using one laser diode constituting the light emitting means 51 and one photodiode constituting the light receiving means 52. There is an advantage that can be done. Also, in the sixth embodiment, similarly to the fifth embodiment, by using an optical fiber cable for the feed line of the electric field probe, disturbance of the electric field distribution can be prevented and accurate electric field strength can be measured. it can.

  The electric field probe 20 ″ and the electric field measuring device 104 of the sixth embodiment are also isotropic because they have three electric field sensor elements oriented in three directions orthogonal to each other, as in the first embodiment. is there. Furthermore, by converting each high-frequency signal generated in the power supply portion of the electric field sensor element into an optical signal and outputting it, the loss of the cable can be reduced and the electric field detection sensitivity can be increased.

In this example, the electric field sensor elements of the first embodiment (x-axis electric field sensor element 10x, y-axis electric field sensor element 10y, z-axis electric field sensor element 10z) are used as the electric field sensor elements of the electric field probe 20 ′ ″. However, the electric field sensor elements of the second embodiment (x-axis electric field sensor element 10x ′, y-axis electric field sensor element 10y ′, z-axis electric field sensor element 10z ′) may be used.
Needless to say, other modifications are possible without departing from the spirit of the present invention.

The figure which shows the electric field measuring apparatus of a 1st Example. The perspective view which shows the outline of the electric field probe of 1st Example. The figure which shows the x-axis electric field sensor element of a 1st Example. The figure which shows the function structure of the electric field measuring apparatus of a 1st Example. The figure which shows the electric field measuring apparatus of a 2nd Example. The perspective view which shows the outline of the electric field probe of 2nd Example. The figure which shows the electric field measuring apparatus of a 3rd Example. The figure which shows the electric field measuring apparatus of 4th Example. The figure which shows the electric field measuring apparatus of 5th Example. The figure which shows the electric field measuring apparatus of 6th Example. The figure which shows the electric field probe of a prior art.

Explanation of symbols

10x axis electric field sensor element, 10y axis electric field sensor element, 10z axis electric field sensor element, 12 metal box, 13x power feeding part, 20 electric field probe, 21x x axis filter, 21y y axis filter, 21z z axis filter, 22x x axis mixer, 22y y-axis mixer, 22z z-axis mixer, 23 local oscillator, 24x output connector, 24y output connector, 24z output connector, 31x coaxial line, 31y coaxial line, 31z coaxial line, 40 electric field strength calculation unit, 41x x-axis electric field strength calculation Unit, 41y y-axis field strength calculation unit, 41z z-axis field strength calculation unit, 42 total field strength calculation unit, 51 light emitting means, 51x x-axis laser diode, 51y y-axis laser diode, 51z z-axis laser diode, 52 light receiving means , 52x x-axis Mach-Zehnder optical modulator 52y y-axis Mach-Zehnder light modulator, 52z z-axis Mach-Zehnder light modulator, 53 light receiving means, 53x x-axis photodiode, 53y y-axis photodiode, 53z z-axis photodiode, 71 first optical switch, 72 second light Switch 73 control unit 100 electric field measuring device

Claims (9)

Three electric field sensor elements arranged in three directions orthogonal to each other;
Using an oscillation signal oscillated from a local oscillator, three mixers for converting each high-frequency signal generated in the power feeding section of the three electric field sensor elements into an intermediate frequency signal;
Three connectors for outputting each of the converted intermediate frequency signals,
Electric field probe comprising: The electric field probe according to claim 1,
Each of the three electric field sensor elements is a butterfly-shaped slot antenna.
An electric field probe characterized by that. The electric field probe according to claim 1,
Three filters for attenuating image frequency components from the respective high-frequency signals generated in the power feeding portions of the three electric field sensor elements are provided.
The three mixers are three mixers that convert each high-frequency signal having the image frequency component attenuated into an intermediate frequency signal using an oscillation signal transmitted from a local oscillator.
An electric field probe characterized by that. The electric field probe according to claim 3,
Each of the three electric field sensor elements is a conical monopole antenna comprising a conical radiating element.
An electric field probe characterized by that. The electric field probe according to any one of claims 1 to 4,
Electric field strength calculation means for obtaining each electric field strength in the three directions from the intermediate frequency signal output by the electric field probe, and obtaining the electric field strength at the position of the electric field probe from the obtained electric field strength;
A helically wound coaxial line connecting the electric field probe and the electric field strength calculating means,
An electric field measuring apparatus comprising: In the electric field measuring apparatus according to claim 5,
The pitch of the coaxial line is a logarithmic period,
An electric field measuring apparatus characterized by that. Three electric field sensor elements arranged in three directions orthogonal to each other;
A light emitting means for emitting light;
Three Mach-Zehnder optical modulators that convert the high-frequency signals into optical signals and output the optical signals by modulating the light based on the high-frequency signals respectively generated in the power feeding units of the three electric field sensor elements;
A light receiving means for converting each optical signal output from the three Mach-Zehnder optical modulators into an electrical signal;
A mixer device that lowers the frequency of the electrical signal using an oscillation signal oscillated from a local oscillator;
Electric field strength calculating means for obtaining electric field strengths in the three directions from the electric signal with the frequency lowered, and obtaining electric field strengths at the position of the electric field probe from the obtained electric field strengths;
An electric field measuring apparatus comprising: In the electric field measuring device according to claim 7,
The light emitting means is three laser diodes each emitting light,
The light receiving means is three photodiodes that respectively convert the optical signals output from the three Mach-Zehnder optical modulators into electrical signals.
An electric field measuring apparatus characterized by that. In the electric field measuring device according to claim 7,
The light emitting means is one laser diode that emits light,
The light receiving means is one photodiode that converts each optical signal output from the three Mach-Zehnder optical modulators into an electrical signal,
A first optical switch for emitting light emitted from the laser diode to any one of the three Mach-Zehnder optical modulators;
A second optical switch for outputting an optical signal output from any of the three Mach-Zehnder optical modulators to the photodiode;
Control means for sequentially switching the first optical switch and the second optical switch in order to sequentially obtain electrical signals corresponding to the electric field sensor elements;
An electric field measuring device further comprising:

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