JP2006029813A - Electric field sensor and electric field strength measuring apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electric field sensor and an electric field strength measuring apparatus capable of wide-band electric field strength measurement. <P>SOLUTION: The electric field sensor 100 based on a sleeve antenna is constituted of a radiating element 101 in which at least one resistive element 105 is serially connected to a plurality of linear metals 104, a sleeve 103 in which a resistive element 106 is serially connected to a plurality of linear metals 107, and a coaxial feeder 102. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an electric field sensor used in an electric field intensity measuring apparatus that measures electric field intensity of a radio wave around a transmission antenna, and more particularly to an electric field sensor and an electric field intensity measuring apparatus having isotropic directivity characteristics in a wide band (wide frequency range).

  A dipole antenna as shown in FIG. 1 is used as an electric field sensor for measuring the electric field intensity around the transmission antenna. In addition, in order to make the directivity characteristic isotropic in the electric field strength measuring apparatus, three dipole antennas are used, and each dipole antenna is arranged in parallel to the orthogonal x-axis, y-axis, and z-axis. .

  In the electric field strength measuring apparatus, the length of each dipole antenna is set to ½ or less of the wavelength of the upper limit frequency used so that resonance does not occur. A coaxial cable is used as the feeder line. A balanced / unbalanced converter (balun) is used to connect the dipoles coaxially. Ferrite beads are used as the balance / unbalance converter.

  Of the background art described above, the electric field sensor is not known in the literature as far as the applicant knows at the time of filing.

  Further, the applicant has not been able to find prior art documents related to the present invention by the time of filing. Therefore, prior art document information is not disclosed.

  However, the background art described above has the following problems.

  There is a problem that the sensitivity of the electric field sensor decreases as the frequency decreases.

  In order to prevent this decrease in sensitivity, a dipole having a long element length is used. However, when the element length is increased, the resonance frequency is lowered. For this reason, there is a problem that a plurality of dipoles having different element lengths must be switched and used in order to perform a wide band measurement.

  Therefore, an object of the present invention is to provide an electric field sensor and an electric field strength measuring apparatus capable of measuring electric field strength in a wide band.

  In order to solve the above problems, an electric field sensor of the present invention is an electric field sensor including a sleeve antenna. The sleeve antenna includes a radiating element and a sleeve in which at least one resistance element and a plurality of linear metals are connected in series.

  With this configuration, the occurrence of resonance in a wide band can be reduced.

  The electric field strength measuring device of the present invention is an electric field strength measuring device including an electric field sensor. The electric field sensor includes a sleeve antenna, and the sleeve antenna includes at least one resistance element and a plurality of linear metals connected in series. A radiating element and a sleeve.

  With this configuration, the electric field strength can be measured without preparing a large number of electric field sensors for each frequency band.

  According to the embodiment of the present invention, it is possible to realize an electric field sensor and an electric field intensity measuring apparatus capable of measuring electric field intensity in a wide band.

Next, embodiments of the present invention will be described with reference to the drawings.
In all the drawings for explaining the embodiments, the same reference numerals are used for those having the same function, and repeated explanation is omitted.

  An electric field sensor according to a first embodiment of the present invention will be described with reference to FIG.

  The electric field sensor 100 according to the present embodiment is based on a sleeve antenna, and includes a radiating element 101, a sleeve 103, and a coaxial feeder 102.

The radiating element 101 includes a series connection of at least one resistance element 105 and a plurality of linear metals 104. For example, three linear metals and two resistive elements are connected in series in the order of the linear metal 104, the resistive element 105, the linear metal 104, the resistive element 105, and the linear metal 104. For example, the length L ₀ of the linear metal 104 is set as shown in Expression (1) with respect to the wavelength λ _min corresponding to the assumed upper limit of the measurement frequency.
0 <L ₀ ≦ λ _min / 4 (1)
Further, the entire length L of the radiating element 101 is set as shown in Expression (2) with respect to the wavelength λ _max corresponding to the assumed lower limit of the measurement frequency.
L ₀ <L ≦ λ _max / 4 (2)
The sleeve 103 has the same structure as the radiating element 101. That is, the sleeve 103 is configured by connecting at least one resistance element 106 and a plurality of linear metals 107 in series. For example, three linear metals and two resistive elements are connected in series in the order of the linear metal 107, the resistive element 106, the linear metal 107, the resistive element 106, and the linear metal 107.

  As described above, the resistance element 105 is inserted into the radiating element 101 and the sleeve 103, whereby the occurrence of resonance can be prevented and the measurement frequency range in the electric field strength measurement can be widened.

  Next, an electric field sensor according to a second embodiment of the present invention will be described with reference to FIG.

  The electric field sensor according to the present embodiment uses a cylindrical metal having a cylindrical shape as the linear metal in the electric field sensor described with reference to FIG. A cylindrical resistance element having a cylindrical shape is used as the resistance element.

  The electric field sensor 200 according to the present embodiment includes a radiating element 201 and a sleeve 203. The radiating element 201 includes a series connection of at least one cylindrical resistance element 205 and a plurality of cylindrical metals 204. For example, three cylindrical metals 204 and two cylindrical resistance elements 205 are arranged in the order of the cylindrical metal 204, the cylindrical resistance element 205, the cylindrical metal 204, the cylindrical resistance element 205, and the cylindrical metal 204. Connect in series.

  The sleeve 203 has the same structure as the radiating element 201. That is, the sleeve 203 is configured by connecting at least one cylindrical resistance element 207 and a plurality of cylindrical metals 206 in series. For example, three cylindrical metals 206 and two cylindrical resistance elements 207 are arranged in the order of the cylindrical metal 206, the cylindrical resistance element 207, the cylindrical metal 206, the cylindrical resistance element 207, and the cylindrical metal 206. Connect in series.

For example, the length L ₀ of the cylindrical metal 204 is set as shown in Expression (1) with respect to the wavelength λ _min corresponding to the assumed upper limit of the measurement frequency, and the entire length L of the radiating element 201 is assumed to be The wavelength λ _max corresponding to the lower limit of the measured frequency is set as shown in the equation (2). Further, by changing the diameters of the radiating element 201 and the sleeve 203, the measurement frequency bandwidth in the electric field strength measurement can be changed. For example, by increasing the diameters of the radiating element 201 and the sleeve 203, the measurement frequency bandwidth in the electric field strength measurement can be increased.

  Next, an electric field sensor according to a third embodiment of the present invention will be described with reference to FIG.

  The electric field sensor 300 according to the present embodiment includes a radiating element 301, a sleeve 303, a coaxial feeder 302, and a connection point between the sleeve 303 and the coaxial feeder 302, that is, an impedance converter 308 inserted in a feeding portion. The

  The radiating element 301 includes a series connection of at least one resistance element 305 and a plurality of linear metals 304. For example, three linear metals 304 and two resistive elements 305 are connected in series in the order of the linear metal 304, the resistive element 305, the linear metal 304, the resistive element 305, and the linear metal 304.

For example, the length L ₀ of the linear metal 304 is set as shown in Expression (1) with respect to the wavelength λ _min corresponding to the assumed upper limit of the measurement frequency.

Further, the entire length L of the radiating element 301 is set as shown in Expression (2) with respect to the wavelength λ _max corresponding to the assumed lower limit of the measurement frequency.

  The sleeve 303 has the same structure as the radiating element 301. That is, the sleeve 303 is constituted by a series connection of at least one resistance element 306 and a plurality of linear metals 307. For example, three linear metals 307 and two resistive elements 306 are connected in series in the order of the linear metal 307, the resistive element 306, the linear metal 307, the resistive element 306, and the linear metal 307.

  The characteristic impedance of the coaxial feeder 302 is about 50Ω to 70Ω. On the other hand, the lengths of the linear metals 304 and 307 of the radiating element 301 and the sleeve 303 are shorter than “wavelength / 4”. For this reason, the input impedance of the antenna composed of the radiating element 301 and the sleeve 303 becomes larger than 70Ω. Therefore, by providing the impedance conversion circuit 308, impedance matching between the antenna unit including the radiating element 301 and the sleeve 303 and the coaxial feeder 302 is obtained.

Next, the impedance converter 308 will be described with reference to FIG. The impedance converter 308 according to the present embodiment uses an active element such as a transistor. As an example, a case where an FET is used will be described. This circuit is based on a common source amplifier circuit. In order to obtain broadband characteristics, a resistive load _RD is used between the drain and the power supply + _VDS . Further, an output capacitor _CD is inserted between the drain and the coaxial feeder connection terminal connected to the coaxial feeder 302.

A resistor R _S and a bypass capacitor C _S are connected in parallel between the source and the ground terminal. An input capacitor _CG is inserted between the gate and the radiating element connection terminal connected to the radiating element 301. The sleeve connection terminal connected to the sleeve 303 is grounded.

A resistor R _S inserted in the source is provided to apply a negative voltage bias to the gate voltage. In order to further increase the input impedance, a common-drain amplifier circuit can be used. Furthermore, even in a junction transistor amplifier circuit, the input impedance can be increased by adopting a grounded collector type, and the same effect as an FET can be obtained.

  Next, an electric field sensor according to a fourth example of the present invention will be described with reference to FIG. The electric field sensor 300 according to the present embodiment supplies a bias power source necessary for the operation of the impedance converter from a coaxial feeder.

  As shown in FIG. 6A, the electric field sensor 300 according to the present embodiment is the same as the electric field sensor described with reference to FIG. 4, but a bias superposing circuit 309 at one end of the coaxial feeder 302 and a bias separating circuit 311 at the other end. Is provided. The bias superimposing circuit 309 and the bias separation circuit 311 constitute a power supply unit and supply power to the impedance conversion unit 308.

  Next, the configuration of the coaxial feeder 302, the bias superimposing circuit 309, and the bias separation circuit 311 will be described with reference to FIG.

Bias superimposing circuit 309 has one end provided with a choke coil L ₁ of the wide band connected to the coaxial feeder 302, the bias separation circuit 311 broadband choke coil L _2, which is inserted between the power supply + V _DS and the output capacitor C _D Is provided. The other end of the choke coil L ₁ constitutes the bias terminal. Impedance of each choke coil L ₁ and L ₂ are sufficiently higher than the characteristic impedance of the coaxial feeder. With this configuration, the bias superimposing circuit 309 can be supplied with the power required by the impedance converter 308 from the bias terminal.

  Next, an electric field sensor according to a fifth example of the present invention will be described with reference to FIG.

  The electric field sensor according to this example is a combination of three electric field sensors described with reference to FIG. 6 in order to obtain isotropic properties.

In the electric field sensor according to the present embodiment, the longitudinal directions of the _three radiating elements 301 ₁ , 301 _2, and 301 ₃ are parallel to the orthogonal x-axis, y-axis, and z-axis, respectively, as shown in FIG. Be placed.

On the output side, as shown in FIG. 7B, signals corresponding to the respective axes are output. The bias superimposing circuits 309 ₁ , 309 ₂ and 309 ₃ are arranged so that power can be supplied from the bias terminals to the impedance converters 310 ₁ , 310 ₂ and 310 ₃ with bias separation circuits.

By arranging in this way, the signal amplitudes received by the _three electric field sensors 300 ₁ , 300 _2, and 300 ₃ can be synthesized, and isotropic as a whole can be obtained.

  Next, an electric field strength measuring apparatus according to the sixth embodiment of the present invention will be described with reference to FIG.

The electric field strength measuring apparatus 400 according to the present invention includes the electric field sensor described with reference to FIG. 7, electric field sensor detection circuits 312 ₁ , 312 ₂ and 312 ₃ connected to the output terminal of the electric field sensor, And a voltage addition circuit 313 connected thereto.

Detector ₃₁₂ 1, 312 ₂ and 312 _3, for example, a diode, corresponding to the y-axis detectors 312 _2, and z-axis corresponding to x-axis detectors ₃₁₂ 1, y-axis corresponding to x-axis z comprising a shaft for detector 312 _3.

The voltage addition circuit 313 is configured using, for example, an operational amplifier. The voltage addition circuit 313 includes resistors R ₁ and R connected to the operational amplifier 314, the negative phase input terminal of the operational amplifier 314, and the x-axis detector 312 ₁ , the y-axis detector 312 _2, and the z-axis detector 312 _{3. 2} and R ₃ , a resistor R ₄ connecting the negative phase input terminal and the output terminal of the operational amplifier 314, and a resistor R ₅ connected between the positive phase input terminal of the operational amplifier 314 and the ground terminal.

Each detector 312 ₁ , 312 ₂ and 312 ₃ outputs a voltage proportional to the received power. Therefore, the output of the voltage addition circuit 313 is proportional to the power combined value of the signals received on the three axes. With such a configuration, it is possible to prevent the occurrence of resonance in a wide band and improve the measurement frequency band.

  In the embodiment described above, in order to solve the problem of the electric field sensor, a sleeve antenna composed of a resistance element and a linear metal is used as a dipole. Further, an impedance converter based on an active element such as a transistor circuit is used. With this configuration, an isotropic electric field sensor that can prevent resonance in a wide band and can improve the measurement frequency band can be realized. In the future, indoor wireless use is expected to have a very wide frequency range from the MHz band to the GHz band. In such a wireless usage environment, it is possible to measure the electric field intensity distribution without preparing a large number of electric field sensors for each frequency band.

  The electric field sensor according to the present invention can be applied to an electric field strength measuring apparatus that measures the electric field strength of radio waves around a transmission antenna.

It is a block diagram of an isotropic sensor. It is the schematic of the electric field sensor concerning one Example of this invention. It is the schematic of the electric field sensor concerning one Example of this invention. It is the schematic of the electric field sensor concerning one Example of this invention. It is a block diagram of the impedance converter concerning one Example of this invention. It is the schematic of the electric field sensor concerning one Example of this invention. It is the schematic of the electric field sensor concerning one Example of this invention. It is the schematic of the electric field strength measuring apparatus concerning one Example of this invention.

Explanation of symbols

100, 200, 300 Electric field sensor 400 Electric field intensity measuring device

Claims (10)

In an electric field sensor with a sleeve antenna:
The sleeve antenna is
A radiating element and a sleeve in which at least one resistance element and a plurality of linear metals are connected in series;
An electric field sensor comprising: The electric field sensor according to claim 1:
The resistance element includes a cylindrical resistance element having a cylindrical shape,
The electric field sensor, wherein the linear element includes a cylindrical metal having a cylindrical shape. The electric field sensor according to claim 1 or 2, wherein:
The linear metal is
An electric field sensor satisfying 0 <L ₀ ≦ λ _min / 4, where L _{0 is} a length of the linear metal and λ _min is a wavelength corresponding to an upper limit of an assumed measurement frequency. The electric field sensor according to claim 3:
The radiating element is:
An electric field sensor satisfying L ₀ <L ≦ λ _max / 4, where L is a length of the radiating element and λ _max is a wavelength corresponding to a lower limit of an assumed measurement frequency. 5. The electric field sensor according to claim 1, wherein:
Impedance conversion means for performing impedance matching between the radiating element and the sleeve and the coaxial feeder;
An electric field sensor comprising: The electric field sensor according to claim 5, wherein:
The electric field sensor, wherein the impedance conversion means includes an active element. The electric field sensor according to claim 5 or 6, wherein:
Power supply means for supplying power to the impedance conversion means;
An electric field sensor comprising: The electric field sensor according to claim 7:
An electric field sensor comprising three electric field sensors arranged in parallel to an x axis, a y axis, and a z axis orthogonal to each other. The electric field sensor according to claim 8, wherein:
Detection means for detecting the output of the electric field sensor corresponding to each axis;
Voltage adding means for adding the outputs of the detector;
An electric field sensor comprising: In an electric field strength measuring device equipped with an electric field sensor:
The electric field sensor comprises a sleeve antenna;
With
The sleeve antenna includes a radiating element and a sleeve in which at least one resistance element and a plurality of linear metals are connected in series;
An electric field strength measuring device comprising:

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