JP5373534B2 - Phase difference measuring method and phase difference measuring apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a device and a method for accurate measurement of a minute phase change. <P>SOLUTION: The method includes: a step of forming a reference signal of a predetermined frequency; a step of forming an input signal used for formation of an electromagnetic wave to be irradiated on a measurement object based on the reference signal; a first step of irradiating the measurement object with the electromagnetic wave based on the input signal; a second step of receiving a measurement signal whose phase has changed for the electromagnetic wave by the measurement object; a third step of forming the input signal using the measurement signal; and a fourth step of determining a phase difference using the reference signal and the measurement signal subsequent to predetermined times of repetitions of the first step, second step and third step. <P>COPYRIGHT: (C)2011,JPO&amp;INPIT

Description

  The present invention relates to a phase difference measuring method and a phase difference measuring apparatus for irradiating a measurement object with an electromagnetic wave and measuring a phase difference between a measurement signal whose phase is changed by the measurement object and the irradiated electromagnetic wave.

In recent years, concrete deterioration has become a problem in concrete objects such as concrete buildings, floor slabs of concrete bridges, highway slabs, and the like that use steel materials such as reinforcing bars.
As a cause of deterioration of the concrete object, salt content in the concrete object can be mentioned. Salinity is contained in sand used when manufacturing concrete objects. In addition, salt may enter the concrete object after production. The salt in the concrete object corrodes the steel material such as a reinforcing bar, which causes the steel material such as the reinforcing bar to expand, and cracks and peeling occur in the concrete.
In order to ensure the safety of the concrete object, it is necessary to measure the salt concentration in the concrete object before the deterioration of the concrete progresses.

  In order to examine information on the salinity concentration of a concrete object, a four-pole method is known in which the electrical conductivity of a concrete object is measured in a frequency range of 0 to 1 MHz. This method utilizes the fact that the higher the salt concentration in the concrete object, the higher the electrical conductivity. However, this method requires the electrode to be driven deeply into the concrete object. Therefore, the salinity concentration cannot be measured without destroying the concrete object.

  In addition, a plurality of concrete specimens with different salt concentrations are mixed in a concrete material with the same composition as the concrete to be inspected, and an electromagnetic wave signal is incident on each specimen to determine the amplitude attenuation and propagation speed per unit distance. Measure the temperature of the test piece, find the relational expression with the amplitude attenuation, propagation velocity and temperature as independent variables and the salinity concentration as the dependent variable from the measured values for each test piece, and input the electromagnetic wave signal to the target concrete and unit A method is known in which the amplitude attenuation, propagation velocity and temperature of a specimen are measured per distance, and the salt concentration in the target concrete is detected by substituting the amplitude attenuation, propagation velocity and temperature into the relational expression (Patent Literature). 1).

  However, in this method, it is necessary to produce a plurality of concrete specimens classified by salt concentration in which a predetermined concentration of salt is mixed into a concrete material having the same composition as the concrete to be inspected. Therefore, when concrete manufactured several tens of years ago is used as an inspection target, it is difficult to produce a sample that reproduces a concrete material having the same composition. In addition, this method has a problem that it is necessary to measure the propagation speed, and the measurement becomes complicated.

Moreover, the method of calculating | requiring the salt concentration of a concrete target object by irradiating the surface of a concrete target object with electromagnetic waves and measuring the energy loss coefficient of electromagnetic waves is known (nonpatent literature 1).
In this method, the salinity concentration of a concrete object is obtained from the imaginary component of the complex dielectric constant of the concrete.

JP 2004-125570 A

“Microwave reflection and Dielectric Properties of Mortar Subjected to Compression Force and Cyclically Exposed to Water and Sodium Chloride Solution”, Shanup Peer, IEEE Trans. Instrumentation and Measurement, Vol.52, No.1, Feb.2003, p111

  In the conventional method of irradiating the surface of a concrete object with electromagnetic waves and measuring the energy loss coefficient of the electromagnetic waves, the salinity concentration of the concrete object cannot be obtained with sufficient accuracy. This is because the phase of the reflected wave reflected from the concrete object changes depending on the magnitude of the salinity of the concrete object, but this phase change is very small and it is difficult to directly measure the phase change of the reflected wave. .

  Therefore, an object of the present invention is to provide a phase difference measuring method and a phase difference measuring apparatus that can accurately measure a minute phase change.

  In order to solve the above-described problem, the phase difference measurement method of the present invention provides a phase difference between a measurement signal whose phase has changed with respect to the electromagnetic wave by the measurement object and the electromagnetic wave when the measurement object is irradiated with the electromagnetic wave. A phase difference measurement method for measuring, comprising: generating a reference signal having a predetermined frequency; generating an input signal used for generating an electromagnetic wave to be irradiated on the measurement object based on the reference signal; and A first step of irradiating the measurement object with an electromagnetic wave based on a signal; a second step of receiving a measurement signal whose phase is changed by the measurement object with respect to the electromagnetic wave; and the input using the measurement signal. A third step of generating a signal, a first step, a second step, and a third step are repeated a predetermined number of times, and then the phase signal is generated using the reference signal and the measurement signal. And having a fourth step of obtaining a.

  The third step generates the input signal by generating a single pulse signal at a timing when the input signal exceeds a predetermined threshold and passing the signal having the frequency of the reference signal. Preferably comprising the steps of:

  Further, in the second step, as the measurement signal, a signal whose phase is changed with respect to the electromagnetic wave by the reflection of the electromagnetic wave by the measurement object is received, and the phase difference measurement method includes the measurement object. It is preferable to have a step of adjusting the amplitude of the measurement signal based on the amplitude attenuation rate of the electromagnetic wave reflected in step.

  Further, when each of a plurality of different set frequencies is set to the predetermined frequency, the fourth step includes a step of obtaining a phase difference of the measurement signal with respect to the reference signal for each set frequency, and the reference signal and the measurement Preferably, the step of obtaining the phase difference of the measurement signal with respect to the electromagnetic wave by using a phase difference resulting from a difference in path length with the signal.

  The fourth step is a phase difference obtained by minimizing the variance of the phase difference of the measurement signal with respect to the reference signal at the set frequency, and the path length of the reference signal and the measurement signal is It is preferable to obtain the phase difference of the measurement signal with respect to the electromagnetic wave using a phase difference caused by the difference.

In order to solve the above-described problem, the phase difference measurement apparatus of the present invention irradiates a measurement object with an electromagnetic wave, and the phase difference between the measurement signal and the electromagnetic wave whose phase is changed with respect to the electromagnetic wave by the measurement object. A phase difference measuring apparatus for measuring
A reference signal generator for generating a reference signal of a predetermined frequency;
An input signal generation unit for generating an input signal used for generating an electromagnetic wave to irradiate the measurement object;
Based on the input signal, an electromagnetic wave irradiation unit that irradiates the measurement object with an electromagnetic wave;
A receiving unit for receiving a measurement signal whose phase is changed with respect to the electromagnetic wave by the measurement object;
An arithmetic unit for obtaining the phase difference using the reference signal and the measurement signal;
A switch circuit that outputs the reference signal generated by the reference signal generation unit at a predetermined timing, and
The phase difference measuring apparatus repeats generation of the input signal, irradiation of the electromagnetic wave, and reception of the measurement signal until the number of receptions of the measurement signal received by the receiving unit by irradiation of the electromagnetic wave reaches a predetermined number. Configured as
When the number of receptions is zero, the input signal generation unit generates the input signal using the reference signal output from the switch circuit and supplied to the input signal generation unit, and the number of receptions is one time. At the time described above, the input signal generation unit is configured to generate the input signal using the measurement signal most recently received by the reception unit .

  Further, the input signal generation unit passes a signal having a frequency of the reference signal by passing a waveform shaping circuit that generates a single pulse signal at a timing when the input signal exceeds a predetermined threshold value, A band-pass filter for generating an input signal.

  Further, the receiving unit receives, as the measurement signal, a signal whose phase has changed with respect to the electromagnetic wave as a result of the electromagnetic wave being reflected by the measurement object, and the phase difference measuring device is configured to receive the measurement object. It is preferable to provide an amplitude adjustment unit that adjusts the amplitude of the measurement signal based on the amplitude attenuation rate of the electromagnetic wave reflected in step (b).

  The reference signal generation unit generates the reference signal by setting each of a plurality of different set frequencies as the predetermined frequency, and the calculation unit corresponds to the reference signal obtained for each set frequency. Using the phase difference of the measurement signal, using the phase difference resulting from the difference in path length until the reference signal and the measurement signal are supplied to the arithmetic unit, the position of the measurement signal with respect to the electromagnetic wave It is preferable to obtain the phase difference.

  Further, the calculation unit is a phase difference obtained such that variance of the phase difference of the measurement signal with respect to the reference signal at the set frequency is minimized, and the reference signal and the measurement signal are the calculation unit. It is preferable to obtain the phase difference of the measurement signal with respect to the electromagnetic wave using a phase difference resulting from a difference in path length until the signal is supplied to the electromagnetic wave.

  According to the phase difference measuring method and the phase difference measuring apparatus of the present invention, a minute phase change can be accurately measured.

It is a figure which shows schematic structure of the phase difference measuring apparatus of 1st Embodiment. (A) is a figure which shows an example of the signal supplied to a switch circuit, (b) is a figure which shows an example of the signal which a switch circuit outputs. (A) is a figure which shows an example of the signal supplied to a waveform shaping circuit, (b) is a figure which shows an example of the signal which a waveform shaping circuit outputs, (c) is a figure which shows a band pass filter. It is a figure which shows an example of the signal to output. It is a figure which shows an example of a structure of a calculating part. It is a flowchart of the phase difference measuring method of 1st Embodiment. (A) is a figure which shows an example of the electromagnetic wave irradiated to a measuring object, (b) is a figure which shows an example of a measurement signal. (A) is a figure which shows an example of a reference signal, (b) is a figure which shows an example of a measurement signal, (c) is a figure which shows an example of a reference signal. It is a figure which shows schematic structure of the phase difference measuring apparatus of 2nd Embodiment. It is a figure which shows an example of a structure of an amplitude adjustment part. (A) is a figure which shows an example of the electromagnetic wave irradiated to a measuring object, (b) is a figure which shows an example of a measurement signal with a large amplitude, (c) is a figure of a measurement signal with a small amplitude. It is a figure which shows an example. It is a flowchart of the phase difference measuring method of 2nd Embodiment. It is a flowchart of the phase difference measuring method of 3rd Embodiment. (A) is a diagram plotting the phase difference Z _i measured for the different frequencies, (b) are a diagram showing the relationship between the dispersion and the delay time.

Hereinafter, an apparatus and a method for irradiating a measurement object with an electromagnetic wave and measuring a phase difference of a measurement signal with respect to the irradiated electromagnetic wave will be described based on embodiments.
<First Embodiment>
In the present embodiment, an apparatus and a method for measuring the salinity concentration in concrete as an object to be measured by applying the phase difference measuring apparatus of the present invention will be described.

(Configuration of phase difference measuring device)
First, the schematic configuration of the phase difference measuring apparatus of the present embodiment will be described with reference to FIG. FIG. 1 shows an example of a schematic configuration of a phase difference measuring apparatus according to the present embodiment. The phase difference measuring apparatus according to the present embodiment irradiates concrete as a measurement object with an electromagnetic wave, receives a reflected wave reflected by the measurement object, and obtains a measurement signal. Furthermore, the electromagnetic wave produced | generated based on the input signal is repeatedly irradiated to concrete by producing | generating the input signal used for the production | generation of the electromagnetic wave irradiated to concrete based on a measurement signal. Even when the phase difference of the reflected wave with respect to the electromagnetic wave irradiated on the concrete is extremely small, the phase difference can be measured by repeating the irradiation of the electromagnetic wave.

  As shown in FIG. 1, the phase difference measurement apparatus according to the present embodiment includes a control unit 100, a reference signal generation unit 110, a power splitter 112, a switch circuit 114, a power combiner 116, and an input signal generation unit 120. An electromagnetic wave irradiation unit 130, a reception unit 132, a directional coupler 134, a calculation unit 140, and an output unit 160.

  The control unit 100 controls the reference signal generation unit 110, the switch circuit 114, the reference signal generation circuit 122, and the calculation unit 140. Specifically, the control unit 100 controls the frequency of the reference signal generated by the reference signal generation unit 110. In addition, the control unit 100 controls the timing at which the switch circuit 114 outputs a signal and the period during which the signal is output. In addition, the control unit 100 controls the reference signal generation circuit 122 in order to control the magnitude of the reference signal output from the waveform shaping circuit 124. In addition, the control unit 100 supplies the calculation unit 140 with a trigger signal indicating the timing at which the calculation unit 140 calculates the phase difference of the measurement signal with respect to the electromagnetic wave irradiated on the measurement target T.

  The reference signal generation unit 110 generates a reference signal that serves as a reference for generating an electromagnetic wave to be applied to the measurement target T. The reference signal generator 110 is, for example, a voltage controlled oscillator (VCO). The frequency of the reference signal generated by the reference signal generation unit 110 is controlled by the control unit 100. The reference signal is, for example, a sine wave signal, and the frequency of the reference signal is, for example, 1.5 GHz to 10 GHz. The reference signal generated by the reference signal generation unit 110 is supplied to the power splitter 112.

  The power splitter 112 distributes the reference signal supplied from the reference signal generation unit 110 and supplies the reference signal to the switch circuit 114 and the calculation unit 140. The power splitter 112 supplies the reference signal to the switch circuit 114 and the calculation unit 140 in order to obtain the phase difference between the measurement signal supplied from the directional coupler 134 to the calculation unit 140 and the reference signal, as will be described later. This is because it is used as a standard.

The switch circuit 114 outputs the signal supplied from the power splitter 112 only for a predetermined period. The timing at which the switch circuit 114 outputs a signal and the period during which the signal is output are controlled by the control unit 100. The switch circuit 114 is, for example, an FET switch circuit. The signal output from the switch circuit 114 is supplied to the power combiner 116.
Here, a signal output from the switch circuit 114 will be described with reference to FIG. FIG. 2A shows an example of a signal supplied from the power splitter 112 to the switch circuit 114. FIG. 2B shows an example of a signal output from the switch circuit 114. As shown in FIG. 2B, the switch circuit 114 outputs the signal supplied to the switch circuit 114 only during the period of time t _{0 to} t ₁ . Therefore, the switch circuit 114 outputs an AC signal having a predetermined frequency for a certain period. The period of time _t 0 ~t ₁ is, for example, is about 50ns. As described above, since the frequency of the reference signal is, for example, 1.5 GHz to 10 GHz, the wave number existing in the period from time t _{0 to} t ₁ is, for example, 75 to 500.

Returning to FIG. 1, the power combiner 116 will be described. The power combiner 116 combines the signal supplied from the switch circuit 114 and the signal supplied from the directional coupler 134. The signal synthesized by the power combiner 116 is supplied to the input signal generator 120.
The timing at which the switch circuit 114 outputs a signal so that the signal is not supplied from the directional coupler 134 to the power combiner 116 during the period in which the signal is supplied from the switch circuit 114 to the power combiner 116, The period during which the signal is output is controlled by the control unit 100. Therefore, the power combiner 116 supplies the signal supplied from the switch circuit 114 to the input signal generation unit 120 and supplies the signal from the directional coupler 134 during a period in which the signal is supplied from the switch circuit 114. The signal supplied from the directional coupler 134 is supplied to the input signal generator 120.

The input signal generation unit 120 generates an input signal for generating an electromagnetic wave to be applied to the measurement target T based on the signal supplied from the power combiner 116. As shown in FIG. 1, the input signal generation unit 120 includes a reference signal generation circuit 122, a waveform shaping circuit 124, and a bandpass filter 126.
As will be described later, the reference signal generation circuit 122 supplies the waveform shaping circuit 124 with a reference signal having a certain size to be compared with the magnitude of the signal input from the power combiner 116 to the waveform shaping circuit 124. The size of the reference signal output from the waveform shaping circuit 124 is controlled by the control unit 100.

The waveform shaping circuit 124 generates a single pulse signal every time the signal supplied from the power combiner 116 exceeds a predetermined threshold (reference signal). The pulse signal generated by the waveform shaping circuit 124 is supplied to the band pass filter 126.
The band-pass filter 126 receives the pulse signal supplied from the waveform shaping circuit 124, passes the signal having the frequency of the reference signal, and generates an input signal for generating an electromagnetic wave that irradiates the measurement target T. The input signal generated by the band pass filter 126 is supplied to the electromagnetic wave irradiation unit 130.

  Here, the input signal generated by the input signal generation unit 120 will be described with reference to FIG. FIG. 3A is a diagram illustrating an example of a signal supplied to the waveform shaping circuit 124. As shown in FIG. 3A, the waveform shaping circuit 124 is supplied with the reference signal from the reference signal generation circuit 122 and the signal from the power combiner 116. In FIG. 3A, the reference signal is set to a value smaller than the amplitude of the signal supplied from the power combiner 116. FIG. 3B is a diagram illustrating an example of a pulse signal output from the waveform shaping circuit 124. As shown in FIG. 3B, the waveform shaping circuit 124 generates a single pulse signal every time the signal supplied from the power combiner 116 exceeds the reference signal. Therefore, when the signal supplied from the power combiner 116 is a sine wave signal, the waveform shaping circuit 124 generates a pulse signal with the same cycle as that of the sine wave signal. FIG. 3C is a diagram illustrating an example of a signal (input signal) output from the bandpass filter 126. As shown in FIG. 3C, the input signal is ideally a sine wave signal having the same frequency as the signal supplied to the waveform shaping circuit 124. However, when the signal from the power combiner 116 has a plurality of frequency components, the input signal is a signal obtained by superimposing sine wave signals having a plurality of frequencies.

The input signal generation unit 120 of the present embodiment generates a pulse signal using the waveform shaping circuit 124 and generates an input signal using this pulse signal. However, the input signal generation unit 120 does not use a pulse signal. It is also possible to generate an input signal based on a signal (measurement signal) supplied from the directional coupler 134 to the power combiner 116. However, in order to effectively suppress the distortion of the waveform of the measurement signal as the number of times the generation of the input signal based on the measurement signal is repeated, the input signal generation unit 120 is powered from the directional coupler 134. It is preferable to generate a pulse signal based on a signal (measurement signal) supplied to the combiner 116.
In the present embodiment, the waveform shaping circuit 124 generates a pulse signal based on the signal supplied from the power combiner 116, and the bandpass filter 126 generates an input signal based on the pulse signal. Therefore, it is possible to suppress the generation of the input signal based on the measurement signal in which the waveform is distorted.

Returning to FIG. 1, the electromagnetic wave irradiation unit 130 will be described. The electromagnetic wave irradiation unit 130 irradiates the measurement target T with electromagnetic waves based on the input signal generated by the input signal generation unit 120. The electromagnetic wave irradiation unit 130 is, for example, an antenna that radiates electromagnetic waves.
The receiving unit 132 receives the measurement signal whose phase is changed with respect to the electromagnetic wave by the measurement target T. More specifically, the receiving unit 132 receives a measurement signal whose phase has been changed by the electromagnetic wave irradiated from the electromagnetic wave irradiation unit 130 being reflected by the measurement target T. The receiving unit 132 is, for example, an antenna that receives electromagnetic waves. The measurement signal received by the receiving unit 132 is supplied to the directional coupler 134.
Both the electromagnetic wave irradiation unit 130 and the reception unit 132 are preferably highly directional antennas.

  The directional coupler 134 separates the measurement signal supplied from the reception unit 132 and supplies the measurement signal to the power combiner 116 and the calculation unit 140. The measurement signal supplied from the receiving unit 132 is supplied to the power combiner 116 because, as will be described later, the input signal generation unit 120 generates an input signal using the measurement signal and irradiates the measurement target T with electromagnetic waves. Is to repeat. The reason why the measurement signal supplied from the reception unit 132 is supplied to the calculation unit 140 is that the calculation unit 140 calculates the phase difference of the measurement signal with respect to the electromagnetic wave irradiated to the measurement target T, as will be described later. is there.

The calculation unit 140 obtains the phase difference of the measurement signal with respect to the electromagnetic wave irradiated on the measurement target T using the reference signal supplied from the power splitter 112 and the measurement signal supplied from the directional coupler 134. Information on the phase difference obtained by the calculation unit 140 is supplied to the output unit 160.
The output unit 160 outputs the phase difference information supplied from the calculation unit 140. The output unit 160 is, for example, a display device.
Note that the phase difference between the reference signal and the measurement signal caused by the difference in path length is appropriately corrected by the calculation unit 140.

  Here, the configuration of the calculation unit 140 will be described with reference to FIG. As shown in FIG. 4, the arithmetic unit 140 includes a power splitter 142, a 90 ° hybrid 144, mixers 146 and 148, IF filters / amplifiers 150 and 152, an A / D converter 154, and a signal processing unit. 156.

The power splitter 142 distributes the measurement signal supplied from the directional coupler 134 and supplies it to the mixer 146 and the mixer 148.
The 90 ° hybrid 144 divides the reference signal supplied from the power splitter 112 into two signals, and shifts the phase of one of the two divided signals by 90 °. In the example shown in FIG. 4, one of the signals divided by the 90 ° hybrid 144 is a signal whose phase is not shifted, and this signal is supplied to the mixer 146. The other of the signals divided by the 90 ° hybrid 144 is a signal whose phase is advanced by 90 °, and this signal is supplied to the mixer 148.

The mixers 146 and 148 multiply the signal supplied from the 90 ° hybrid 144 and the measurement signal supplied from the power splitter 142. The signal multiplied by the mixer 146 is supplied to the IF filter / amplifier 150. The signal multiplied by the mixer 148 is supplied to the IF filter / amplifier 152.
The IF filters / amplifiers 150 and 152 filter and amplify the signals supplied from the mixers 146 and 148. Specifically, the IF filters / amplifiers 150 and 152 remove high frequency components from the signals supplied from the mixers 146 and 148, and amplify the signals from which the high frequency components have been removed. The signals filtered and amplified by the IF filters / amplifiers 150 and 152 are supplied to the A / D converter 154.

The A / D converter 154 converts the signals supplied from the IF filters / amplifiers 150 and 152 into digital signals. The A / D converter 154 is supplied with a trigger signal indicating the timing for calculating the phase difference of the measurement signal with respect to the electromagnetic wave irradiated to the measurement target T from the control unit 100. The digital signal generated by the A / D converter 154 is supplied to the signal processing unit 156.
The signal processing unit 156 uses the signal supplied from the A / D converter 154 to obtain the phase difference of the measurement signal with respect to the electromagnetic wave irradiated on the measurement target T. Further, the signal processing unit 156 calculates the salinity concentration in the concrete that is the measurement target T using the phase difference. The signal processing unit 156 is mainly composed of a CPU and a memory. Information on the phase difference obtained by the signal processing unit 156 is supplied to the output unit 160.

(Phase difference measurement method)
Next, a phase difference measuring method using the phase difference measuring apparatus according to the first embodiment will be described with reference to FIG. FIG. 5 is a flowchart of the phase difference measurement method of the present embodiment.
First, the reference signal generation unit 110 generates a reference signal having a predetermined frequency (step S101). The reference signal generated by the reference signal generation unit 110 is supplied to the power splitter 112. The power splitter 112 distributes the reference signal supplied from the reference signal generation unit 110 and supplies the reference signal to the switch circuit 114 and the calculation unit 140.
The switch circuit 114 outputs the signal supplied from the power splitter 112 only for a predetermined period. Therefore, as described above, the switch circuit 114 outputs the signal shown in FIG. 2B to the power combiner 116, for example. The power combiner 116 supplies the signal supplied from the switch circuit 114 to the input signal generation unit 120.

Next, the input signal generation unit 120 generates an input signal for generating an electromagnetic wave irradiated to the measurement target T based on the reference signal (step S102). Specifically, the signal supplied from the power combiner 116 is input to the waveform shaping circuit 124. As described with reference to FIG. 3, the waveform shaping circuit 124 generates a single pulse signal every time the signal supplied from the power combiner 116 exceeds the reference signal. The pulse signal generated by the waveform shaping circuit 124 is supplied to the band pass filter 126.
As described with reference to FIG. 3, the control unit 100 controls the reference signal generation circuit 122 so that the reference signal is smaller than the amplitude of the signal supplied from the power combiner 116.

  The band-pass filter 126 receives the pulse signal supplied from the waveform shaping circuit 124, passes the signal having the frequency of the reference signal, and generates an input signal for generating an electromagnetic wave that irradiates the measurement target T. The input signal generated by the band pass filter 126 is supplied to the electromagnetic wave irradiation unit 130.

Next, the electromagnetic wave irradiation unit 130 irradiates the measurement target T with an electromagnetic wave based on the input signal (step S103).
Next, the receiving unit 132 receives a measurement signal whose phase is changed with respect to the irradiated electromagnetic wave by the measurement target T (step S104). The measurement signal received by the receiving unit 132 is supplied to the directional coupler 134.

Here, with reference to FIG. 6, the relationship between the electromagnetic wave irradiated by the electromagnetic wave irradiation unit 130 and the measurement signal received by the reception unit 132 will be described. 6A shows an example of an electromagnetic wave that the electromagnetic wave irradiation unit 130 irradiates the measurement object T, and FIG. 6B shows an example of a measurement signal that the reception unit 132 receives.
In the present embodiment, the electromagnetic wave applied to the concrete that is the measurement target T is reflected by the measurement target T. The phase of the reflected electromagnetic wave (measurement signal) slightly changes with respect to the phase of the electromagnetic wave irradiated to the measuring object T. In the example shown in FIG. 6, the phase of the measurement signal is delayed by Δθ with respect to the electromagnetic wave irradiated to the measurement target T. Although the phase difference Δθ is clearly shown in FIG. 6 for convenience of explanation, since the actually measured phase difference Δθ is extremely small, it is difficult to directly measure the phase difference Δθ from the measurement signal.

Next, the directional coupler 134 supplies the measurement signal supplied from the reception unit 132 to the power combiner 116 and the calculation unit 140. The signal supplied from the directional coupler 134 to the power combiner 116 is supplied to the input signal generation unit 120, and the input signal generation unit 120 generates an input signal using the measurement signal. Thereafter, steps S102 to S104 described above are repeated a predetermined number of times. In the following description, for the sake of convenience of explanation, an example in which the number of repetitions is set to 5 will be described. The control unit 100 controls the timing of outputting the trigger signal so that the trigger signal is supplied to the calculation unit 140 after repeating steps S102 to S104 a predetermined number of times.
Note that the number of repetitions may be counted by, for example, a bit counter (not shown).

  When steps S102 to S104 described above are repeated a predetermined number of times, the control unit 100 controls the reference signal generation circuit 122 so that the magnitude of the reference signal is higher than the amplitude of the signal supplied from the power combiner 116. Thereby, the repetition of steps S102 to S104 described above ends.

  Here, with reference to FIG. 7, it will be described that the phase difference is accumulated by repeating steps S102 to S104 described above. 7A is a diagram illustrating an example of a reference signal, FIG. 7B is a diagram illustrating an example of a measurement signal, and FIG. 7C is a diagram illustrating an example of a reference signal. . As shown in FIG. 7, every time the above steps S102 to S104 are repeated, the phase difference between the reference signal and the measurement signal increases by Δθ. That is, when steps S102 to S104 described above are repeated n times, the phase difference between the reference signal and the measurement signal becomes nΔθ. Therefore, even when Δθ is extremely small and it is difficult to directly measure the phase difference Δθ of the measurement signal with respect to the electromagnetic wave irradiated to the measurement target T, the above-described steps S102 to 104 are repeated to perform the reference. The phase difference nΔθ between the signal and the measurement signal can be measured.

Next, the calculation unit 140 obtains the phase difference Δθ of the measurement signal with respect to the electromagnetic wave using the reference signal and the measurement signal (step S105). Hereinafter, a method for calculating the phase difference Δθ by the calculation unit 140 will be specifically described.
The reference signal generated by the reference signal generation unit 110 is assumed to be cos (ωt). ω is the angular frequency of the reference signal. Steps S102 to S104 described above are repeated n times, and the signal supplied from the directional coupler 134 to the calculation unit 140 is cos (ωt + nΔθ). For this reason, the output of the mixer 146 and the output of the mixer 148 are expressed as Expression (1) and Expression (2), respectively.

Note that the signal transmission delay and the electromagnetic wave propagation delay are separately adjusted and are not considered here.

Next, the high frequency components of the expressions (1) and (2) are removed by the IF filters / amplifiers 150 and 152. If the output of the IF filter / amplifier 150 is x and the output of the IF filter / amplifier 150 is y, x and y are expressed as follows.

The outputs x and y of the IF filters / amplifiers 150 and 152 are converted into digital signals by the A / D converter 154 and supplied to the signal processing unit 156. The signal processing unit 156 uses the signals x and y supplied from the A / D converter 154 to obtain the phase difference Δθ based on the following equation.

Next, the signal processing unit 156 calculates the salinity concentration in the concrete that is the measurement target T using the obtained phase difference Δθ. Since the magnitude of the phase difference Δθ also changes depending on the magnitude of the salinity concentration in the concrete, the magnitude of the salinity concentration in the concrete can be obtained by obtaining the phase difference Δθ.

  As described above, according to this embodiment, a minute phase change can be accurately measured. Therefore, the salinity concentration of the concrete object can be obtained by a simple method.

  In the present embodiment, the example in which the phase difference with respect to the input signal is measured when the phase of the measurement signal reflected by the measurement object changes has been described. However, the present invention is not limited to this. For example, the present invention can also be applied when the phase of a measurement signal that has passed through a measurement object changes. Examples of cases where the phase of the measurement signal that has passed through the measurement object changes include the measurement of extremely low dielectric constants such as gases, and the case where the salinity concentration is measured with higher accuracy using a sampled concrete specimen. is there.

<Second Embodiment>
(Configuration of phase difference measuring device)
Next, a schematic configuration of the phase difference measuring apparatus according to the second embodiment will be described with reference to FIG. Since the basic configuration of the phase difference measuring apparatus of the present embodiment is the same as that of the first embodiment described above, description of overlapping parts is omitted.
As shown in FIG. 8, the phase difference measurement apparatus according to the present embodiment includes an amplitude adjustment unit 170 in addition to the configuration described in the first embodiment. The measurement signal received by the receiving unit 132 is supplied to the amplitude adjusting unit 170. The amplitude adjustment unit 170 adjusts the amplitude of the measurement signal supplied from the reception unit 132. Specifically, the amplitude adjustment unit 170 adjusts the amplitude of the measurement signal supplied from the reception unit 132 so that the amplitude of the signal input to the waveform shaping circuit 124 is constant.

  Next, a detailed configuration of the amplitude adjustment unit 170 will be described with reference to FIG. As shown in FIG. 9, the amplitude adjustment unit 170 includes a control voltage generator 172 and a variable gain amplifier 174. The control voltage generator 172 supplies a control voltage for adjusting the gain of the variable gain amplifier 174 to the variable gain amplifier 174 based on the signal supplied from the control unit 100. The variable gain amplifier 174 adjusts the gain of the measurement signal supplied from the receiving unit 132 based on the control voltage supplied from the control voltage generator 172. The variable gain amplifier 174 can be constituted by, for example, a PIN diode attenuator and an RF amplifier.

  Here, with reference to FIG. 10, the error of the phase difference caused by the difference in the amplitude of the measurement signal will be described. FIG. 10A is a diagram illustrating an example of an electromagnetic wave irradiated to the measurement target T, FIG. 10B is a diagram illustrating an example of a measurement signal having a large amplitude, and FIG. It is a figure which shows an example of the measurement signal with small amplitude.

  In general, when the measurement target T is irradiated with electromagnetic waves, the amplitude of the measurement signal received by the reception unit 132 depending on the surface shape of the measurement target T, the reflectance, the distance from the electromagnetic wave irradiation unit 130 to the measurement target T, and the like. Will change. As shown in FIGS. 10B and 10C, when a measurement signal having a large amplitude is input to the waveform shaping circuit 124, a timing at which the measurement signal having a large amplitude exceeds the reference signal, and a measurement signal having a small amplitude. Is input to the waveform shaping circuit 124, the timing at which the measurement signal having a small amplitude exceeds the reference signal is different. Thus, if the amplitudes of the measurement signals input to the waveform shaping circuit 124 are different, it is difficult to accurately measure the phase difference.

In the present embodiment, as will be described later, the amplitude attenuation rate of the measurement signal (hereinafter referred to as “amplitude attenuation”) caused by the surface shape, reflectance, the distance from the electromagnetic wave irradiation unit 130 to the measurement object T, and the like. Called "rate") in advance. In addition, the amplitude adjustment unit 170 adjusts the amplitude of the measurement signal based on the amplitude attenuation rate.
According to this embodiment, the amplitude of the signal input to the waveform shaping circuit 124 can be kept constant. Therefore, even when it is difficult to make the distance from the electromagnetic wave irradiation unit 130 to the measurement target T constant, the phase difference can be measured more accurately at a plurality of different positions of the measurement target T. .

(Phase difference measurement method)
Next, a phase difference measuring method using the phase difference measuring apparatus of the second embodiment will be described with reference to FIG. FIG. 11 is a flowchart of the phase difference measurement method of the present embodiment.
First, the phase difference measuring device measures an amplitude attenuation rate (step S201). Specifically, the electromagnetic wave irradiation unit 130 irradiates the measurement target T with electromagnetic waves. Next, the reception unit 132 receives the measurement signal, and supplies the measurement signal to the arithmetic unit 140 via the directional coupler 134 without adjusting the amplitude by the amplitude adjustment unit 170.

Next, the calculation unit 140 obtains the amplitude attenuation rate using the measurement signal and the reference signal supplied via the directional coupler 134. Here, assuming that the amplitude attenuation rate is r (r <1), the outputs x and y of the IF filters / amplifiers 150 and 152 are respectively expressed as follows.

Accordingly, the calculation unit 140 obtains the amplitude attenuation rate r based on the following equation.

The above is the measuring method of the amplitude attenuation rate r shown in step S201. The measured amplitude attenuation rate r is recorded in a memory included in the signal processing unit 156 of the calculation unit 140 described with reference to FIG.

Next, the reference signal generation unit 110 generates a reference signal having a predetermined frequency (step S202). Next, the input signal generation unit 120 generates an input signal used for generating an electromagnetic wave irradiated to the measurement target T based on the reference signal (step S203). Next, the electromagnetic wave irradiation unit 130 irradiates the measurement target T with an electromagnetic wave based on the input signal (step S204). Next, the receiving unit 132 receives a measurement signal whose phase is changed with respect to the electromagnetic wave by the measurement target T (step S205).
Since steps S202 to S205 are the same as steps S101 to S104 described in the first embodiment, detailed description thereof is omitted.

  Next, the amplitude adjustment unit 170 adjusts the amplitude of the measurement signal supplied from the reception unit 132 based on the amplitude attenuation rate r measured in step S201 (step S206). Specifically, first, the control unit 100 reads the value of the amplitude attenuation rate r recorded in the calculation unit 140. Next, the control unit 100 controls the amplitude adjustment unit 170 so that the amplitude adjustment unit 170 multiplies the amplitude of the measurement signal supplied from the reception unit 132 by 1 / r. More specifically, the control unit 100 controls the control voltage generated by the control voltage generator 172. Thereby, the amplitude of the signal input to the waveform shaping circuit 124 can be kept constant.

  Thereafter, steps S203 to S206 described above are repeated a predetermined number of times. When steps S203 to S206 described above are repeated a predetermined number of times, the control unit 100 controls the reference signal generation circuit 122 so that the reference signal becomes higher than the amplitude of the signal supplied from the power combiner 116. Thereby, the repetition of steps S203 to S206 described above ends. Next, the calculation unit 140 obtains the phase difference Δθ of the measurement signal with respect to the electromagnetic wave using the reference signal and the measurement signal (step S207). Since step S207 is the same as step S105 described in the first embodiment, detailed description thereof is omitted.

  As described above, according to the present embodiment, the amplitude of the signal input to the waveform shaping circuit 124 can be kept constant. Therefore, even when it is difficult to make the distance from the electromagnetic wave irradiation unit 130 to the measurement target T constant, the phase difference can be measured more accurately at a plurality of different positions of the measurement target T. .

<Third Embodiment>
Next, a phase difference measuring apparatus and a phase difference measuring method according to the third embodiment will be described. The basic configuration of the phase difference measuring apparatus of this embodiment is the same as that of the first or second embodiment described above.

  The calculation unit 140 according to the present embodiment obtains the phase difference of the measurement signal corresponding to the reference signal for each of a plurality of different frequencies (set frequencies). In addition, the calculation unit 140 uses the phase difference caused by the difference in path length until the reference signal and the measurement signal are supplied to the calculation unit 140, and the level of the measurement signal with respect to the electromagnetic wave irradiated on the measurement target T. Find the phase difference. Here, the path length includes the distance from the electromagnetic wave irradiation unit 130 to the reception unit 132 via the measurement target T, the length of the cable in the circuit, and the like. Further, the calculation unit 140 supplies the calculation unit 140 with the reference signal and the measurement signal obtained so that the variance of the phase difference of the measurement signal corresponding to the reference signals of a plurality of different frequencies (set frequencies) is minimized. The phase difference resulting from the difference in the path length until it is determined is obtained.

With reference to FIG. 12, the phase difference measuring method of the present embodiment will be described. FIG. 12 is a flowchart of the phase difference measurement method of the present embodiment.
First, the phase difference measuring apparatus measures a phase difference with respect to a plurality of frequencies (set frequencies) by the method described in the first embodiment or the second embodiment (step S301). Specifically, first, the control unit 100 controls the frequency of the reference signal by the reference signal generator 110 generates the f _1. Then, the phase difference measuring device measures the phase difference corresponding to a frequency f _1. Let Z ₁ represent this phase difference in a complex number. Next, the control unit 100 controls the frequency of the reference signal by the reference signal generator 110 generates the f _2. Then, the phase difference measuring device measures the phase difference corresponding to a frequency f _2. Those representing the phase difference by a complex number and Z _2. Thereafter, similarly, the phase difference measuring device measures to a phase difference corresponding to a frequency f _N. Those representing the phase difference by a complex number and Z _N. N is preferably 10 or more and 20 or less. Z _i is standardized as | Z _i | = 1 (1 ≦ i ≦ N).

Next, the calculation unit 140 calculates a delay time that minimizes the variance of Z _{i in} which the measured phase difference is displayed as a complex number (step S302). Next, the phase difference Δθ of the measurement signal with respect to the electromagnetic wave irradiated on the measuring object T is obtained using the delay time that minimizes the dispersion of Z _i that displays the measured phase difference as a complex number (step S303).

Hereinafter, first, step S302 described above will be specifically described.
When the phase difference caused by the difference in path length of the reference signal and the measurement signal which is input to the arithmetic unit 140 is known in advance, the phase difference measured when the frequency of the reference signal is a f _i, previously known The phase difference Δθ of the measurement signal with respect to the electromagnetic wave irradiated on the measuring object T can be obtained from the phase difference caused by the difference in the path length of the reference signal and the measurement signal.
However, when the distance from the electromagnetic wave irradiation unit 130 to the measurement target T is unknown, the phase difference due to the difference in the path length between the reference signal input to the calculation unit 140 and the measurement signal is not known, and thus the reference signal from the phase difference measured when the frequency is f _i, it is impossible to determine the phase difference Δθ of the measurement signal for the irradiated electromagnetic wave measurement target T.

Here, when the frequency is f _i, the phase difference due to the difference in path length of the reference signal and the measurement signal input to the arithmetic unit 140 and theta _i. Also, let τ be the delay time resulting from the difference in path length between the reference signal input to the calculation unit 140 and the measurement signal. At this time, the following relational expression holds.

The delay time tau, is a constant that does not depend on the frequency f _i.

When the phase difference Z _i displayed as a complex number is corrected in consideration of the delay time τ, the average value of the phase difference after correction and the variance σ are expressed by the following equations (10) and (11), respectively. Is done.

The delay time τ can be obtained from the condition that minimizes the variance σ expressed by the equation (11).

Hereinafter, the results of the measurement of the phase difference Z _i for a plurality of frequencies f _i, concretely explaining the method of obtaining the delay time tau.
First, varying by 0.1GHz frequency _{f i} to 1.6GHz～2.0GHz, for each frequency _{f i,} measuring the phase difference _{Z i.} Table 1 below shows an example of measurement results.

  When the measurement results shown in Table 1 are plotted on the complex plane, the result is as shown in FIG. As shown in FIG. 13A, the measurement result shown in Table 1 includes the delay time τ caused by the difference in the path length between the reference signal input to the calculation unit 140 and the measurement signal. The phase difference Δθ of the measurement signal with respect to the electromagnetic wave cannot be obtained directly from the measurement result.

  In the present embodiment, the delay time τ that minimizes the dispersion σ is obtained using the measurement result shown in Table 1 and the equation (11). FIG. 13B is a diagram showing the relationship between the dispersion σ and the delay time τ obtained by substituting the measurement result shown in Table 1 into the equation (11). In the present embodiment, the dispersion σ is minimized at τ = 2.62 ns. By using the delay time τ that minimizes the dispersion σ, the phase difference Δθ of the measurement signal with respect to the electromagnetic wave can be obtained from the equation (10).

  As described above, in the present embodiment, the phase difference of the measurement signal corresponding to the reference signal is obtained for each of a plurality of different frequencies, and the difference in path length until the reference signal and the measurement signal are supplied to the calculation unit 140. Is used to obtain the phase difference Δθ of the measurement signal with respect to the electromagnetic wave irradiated to the measurement target T. Therefore, even when the distance from the electromagnetic wave irradiation unit 130 to the measurement target T is unknown, the delay time τ caused by the difference between the path length of the reference signal input to the calculation unit 140 and the measurement signal is obtained. Thus, the phase difference caused by the delay time τ can be corrected.

  Although the phase difference measuring apparatus and method of the present invention have been described in detail above, the present invention is not limited to the above-described embodiment, and various improvements and modifications may be made without departing from the spirit of the present invention. Of course.

100 control unit 110 reference signal generation unit 112 power splitter 114 switch circuit 116 power combiner 120 input signal generation unit 122 reference signal generation circuit 124 waveform shaping circuit 126 band pass filter 130 electromagnetic wave irradiation unit 132 reception unit 134 directional coupler 140 calculation unit 142 Power splitter 144 90 ° hybrid 146, 148 Mixer 150, 152 IF filter / amplifier 154 A / D converter 156 Signal processing unit 160 Output unit 170 Amplitude adjustment unit 172 Control voltage generator 174 Variable gain amplifier T Measurement object

Claims (10)

A phase difference measurement method for measuring a phase difference between a measurement signal having a phase changed with respect to the electromagnetic wave by the measurement object and the electromagnetic wave when the measurement object is irradiated with an electromagnetic wave,
Generating a reference signal of a predetermined frequency;
Generating an input signal used for generating an electromagnetic wave to irradiate the measurement object based on the reference signal;
A first step of irradiating the object to be measured with electromagnetic waves based on the input signal;
A second step of receiving a measurement signal having a phase changed with respect to the electromagnetic wave by the measurement object;
A third step of generating the input signal using the measurement signal;
And a fourth step of obtaining the phase difference using the reference signal and the measurement signal after repeating the first step, the second step, and the third step a predetermined number of times. Measuring method. The third step is
Generating a single pulse signal at a timing when the input signal exceeds a predetermined threshold;
Generating the input signal by passing a signal having a frequency of the reference signal; and
The phase difference measuring method according to claim 1, comprising: In the second step, as the measurement signal, a signal whose phase is changed with respect to the electromagnetic wave as a result of reflection of the electromagnetic wave by the measurement object is received,
The phase difference measurement method according to claim 1, wherein the phase difference measurement method includes a step of adjusting an amplitude of the measurement signal based on an amplitude attenuation rate of the electromagnetic wave reflected from the measurement object. When each of a plurality of different set frequencies is the predetermined frequency,
The fourth step is
Obtaining a phase difference of the measurement signal with respect to the reference signal for each set frequency;
Determining the phase difference of the measurement signal relative to the electromagnetic wave using a phase difference resulting from a path length difference between the reference signal and the measurement signal;
The phase difference measuring method according to claim 1, comprising:   The fourth step is a phase difference obtained by minimizing the dispersion of the phase difference of the measurement signal with respect to the reference signal at the set frequency, and the difference in path length between the reference signal and the measurement signal. The phase difference measurement method according to claim 4, wherein the phase difference of the measurement signal with respect to the electromagnetic wave is obtained using the resulting phase difference. A phase difference measuring device that irradiates a measurement object with an electromagnetic wave, and measures a phase difference between the measurement signal and the electromagnetic wave whose phase has changed with respect to the electromagnetic wave by the measurement object,
A reference signal generator for generating a reference signal of a predetermined frequency;
An input signal generation unit for generating an input signal used for generating an electromagnetic wave to irradiate the measurement object;
Based on the input signal, an electromagnetic wave irradiation unit that irradiates the measurement object with an electromagnetic wave;
A receiving unit for receiving a measurement signal whose phase is changed with respect to the electromagnetic wave by the measurement object;
An arithmetic unit for obtaining the phase difference using the reference signal and the measurement signal;
A switch circuit that outputs the reference signal generated by the reference signal generation unit at a predetermined timing, and
The phase difference measuring apparatus repeats generation of the input signal, irradiation of the electromagnetic wave, and reception of the measurement signal until the number of receptions of the measurement signal received by the receiving unit by irradiation of the electromagnetic wave reaches a predetermined number. Configured as
When the number of receptions is zero, the input signal generation unit generates the input signal using the reference signal output from the switch circuit and supplied to the input signal generation unit, and the number of receptions is one time. At this time, the input signal generation unit is configured to generate the input signal using the measurement signal most recently received by the reception unit. The input signal generator is
A waveform shaping circuit that generates a single pulse signal at a timing when the input signal exceeds a predetermined threshold; and
A band-pass filter that generates the input signal by passing a signal having a frequency of the reference signal;
The phase difference measuring apparatus according to claim 6, comprising: The receiving unit receives, as the measurement signal, a signal whose phase has changed with respect to the electromagnetic wave due to the electromagnetic wave being reflected by the measurement object,
The phase difference measuring device includes:
The phase difference measuring apparatus according to claim 6, further comprising an amplitude adjusting unit that adjusts an amplitude of the measurement signal based on an amplitude attenuation rate of the electromagnetic wave reflected from the measurement object. The reference signal generation unit generates the reference signal by setting each of a plurality of different set frequencies as the predetermined frequency;
The calculation unit uses a phase difference of the measurement signal corresponding to the reference signal obtained for each set frequency, and a difference in path length until the reference signal and the measurement signal are supplied to the calculation unit. The phase difference measuring apparatus according to claim 6, wherein the phase difference of the measurement signal with respect to the electromagnetic wave is obtained using a phase difference caused by the electromagnetic wave.   The calculation unit is a phase difference obtained by minimizing a variance of the phase difference of the measurement signal with respect to the reference signal at the set frequency, and the reference signal and the measurement signal are supplied to the calculation unit The phase difference measurement device according to claim 9, wherein the phase difference of the measurement signal with respect to the electromagnetic wave is obtained using a phase difference caused by a difference in path length until the phase difference.