JP2002168945A - Instrument for measuring relative distance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To correct a temperature by on-line to measure a distance precisely. SOLUTION: An FM-CW signal is output from a voltage-controlled oscillator 22 by a sweep voltage E0. The FM-CW signal is distributed by a first RF circuit 23 to be transmitted to a transceiving antenna 14, and the FM-CW signal is mixed with a received signal propagated through a route of a measuring object from the transceiving antenna 14 to output a beat signal E1. A radio wave propagation distance is found by a computer 20 based on the beat signal E1 to measure the relative distance. The FM-CW signal is distributed concurrently by a second RF circuit 33 to be transmitted to a cable 40, and the FM-CW signal is mixed with a signal returned from the cable to output a second beat signal E2. Variations of a phase and a frequency of the second beat signal E2 caused by temperature change are detected to change the sweep voltage E0 in response to the change.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an object which changes relative to a predetermined distance by transmitting a radio wave such as VHF, UHF, microwave, millimeter wave band of 100 MHz or more along a path to be measured. The present invention relates to a device for measuring a temporal change amount or a spatial change amount of a distance, and is applied to, for example, a road surface shape measuring device for non-contactly measuring a flatness of a pavement road surface which affects a ride comfort and a traffic vibration when a vehicle is traveling. The present invention relates to a relative distance measuring device which can be used, and more particularly to an improvement in temperature characteristics of the relative distance measuring device.

[0002]

2. Description of the Related Art A conventional relative distance measuring apparatus will be described below by taking as an example a case of measuring the flatness of a pavement road surface. Conventionally, as a device for measuring the flatness of a pavement road surface, there are two types of devices, a contact type and a non-contact type. As the contact type, a measuring wheel is put out from the center of a 3 m linear ruler supported by wheels. A 3 m profile meter for measuring the unevenness of the road surface by bringing the measurement wheel into contact with the road surface has been put to practical use. On the other hand, 3
Attach a detection unit using laser light in the center of the m straight line ruler, distance to the road surface using the relationship that the reflection angle of the reflected light when illuminating the road surface with the laser light corresponds to the unevenness of the road surface,
That is, a laser profiler (for example, Japanese Patent Publication No. 5-644 and Japanese Patent Publication No. 5-43249) for measuring the flatness of a road surface has been put to practical use.

[0003] However, in such a conventional contact-type device, since the measurement wheel is in contact with the road surface, there are problems such as generation of an error due to wear or slip of the wheel. On the other hand, in the non-contact type device, since the measurement is performed using laser light, the problem of the above-mentioned contact type device has been solved, but the distance from the laser light source to the road surface to reach the optical sensor by triangulation. Therefore, if the optical axis is deviated, there is a problem that an error increases and it is difficult to adjust the error. Furthermore, since the beam width of the laser beam is extremely narrow and is sensitively affected by holes and small irregularities on the road surface as a reflector, data averaging processing is required, making high-speed measurement difficult. is there. In particular, on a porous asphalt pavement road having good drainage characteristics, there is a problem that the reflected light of the irradiated laser beam cannot be stably received because the road surface has a relatively large hole.

In order to solve such a problem, the applicant of the present invention disclosed in Japanese Patent Application No. 11-177511 (hereinafter referred to as the prior application) a high-speed, high-precision, high-precision radio wave such as a microwave. A relative distance measuring device capable of measuring a temporal or spatial change amount of a target distance with a distance resolution has been proposed. According to the present invention, when a radio wave such as a microwave is used, the beam width is appropriately wide, so that the signal representing the average distance can be stabilized without being affected by the distribution of the holes and minute irregularities of the reflector. Therefore, the averaging process does not need to be separately performed, and high-speed measurement can be performed.

[0005]

In the apparatus according to the above-mentioned prior application, in order to perform distance measurement with higher accuracy, it is necessary to consider the influence of a change in characteristics due to a change in temperature.
For example, in the device according to the above-mentioned prior application, a voltage-controlled oscillator is provided in a transmission / reception module in order to generate a transmission signal subjected to frequency modulation over a wide band, but the oscillation frequency of the voltage-controlled oscillator changes depending on temperature. As a result, there is a problem that characteristics are changed.

In order to improve the temperature characteristics, there are two methods of improving the temperature characteristics of the module itself or using the device at a constant temperature. However, the method of improving the temperature characteristics of the module has a problem that it costs a great deal of money, and the method of using the module at a constant temperature requires a heat-up time, which wastes time. However, when the power source is a battery, there is a problem that a large one is required.

As another method, a method of preparing a correction table by performing a temperature test in advance and performing temperature correction using this correction table is also conceivable, but this increases the cost and increases the temperature characteristics. In the case of a change, it is necessary to change and re-create the correction table, and there is a problem that it takes time and effort.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a relative distance measuring device capable of performing temperature correction online and performing highly accurate distance measurement.

[0009]

According to the first aspect of the present invention, there is provided an apparatus for transmitting a radio wave such as a VHF, UHF, microwave, millimeter wave band or the like having a frequency of 100 MHz or more along a path to be measured. A relative distance measuring device that measures a temporal change amount or a spatial change amount of a target distance that changes minutely relative to a predetermined distance by generating a transmission signal that has undergone frequency modulation over a wide band. Modulating means, transmitting means for radiating radio waves by the transmission signal along a path to be measured, receiving means for receiving radio waves radiated from the transmitting means and propagated on the path, and transmission from the frequency modulating means. A first transmitting / receiving circuit that mixes the signal and the signal received from the receiving means and outputs a beat signal having a frequency and a phase corresponding to the radio wave propagation distance, which is a low frequency component thereof; A relative distance change amount calculating means for measuring a temporal change amount or a spatial change amount of the target distance based on the beat signal, a cable for transmitting the transmission signal, a transmission signal from the frequency modulation means, And a second transmission / reception circuit that outputs a second beat signal having a frequency and a phase corresponding to the propagation distance of the cable, which is a low-frequency component thereof, and a period of the second beat signal. And temperature correction means for changing the frequency modulation of the frequency modulation means in accordance with at least one of the phase changes.

The first transmission / reception circuit mixes the frequency-modulated transmission signal with the reception signal that has propagated along the path to be measured, and outputs a beat signal. Since the beat signal depends on the radio wave propagation distance, the radio wave propagation distance can be obtained from the beat signal information, and the relative distance can be measured.

On the other hand, the second transmission / reception circuit also mixes the frequency-modulated transmission signal with the reception signal transmitted through the cable, and outputs a second beat signal. Since the propagation distance through the cable is constant, the second beat signal should always be constant, but at least one of the phase and the frequency of the second beat signal changes due to a temperature change. Therefore, by changing the frequency modulation according to this change, the temperature can be corrected on-line, and highly accurate distance measurement can be performed. The length of the cable may be substantially the same as the predetermined distance,
They can be different and can be of any fixed length. Preferably, the length of the cable is such that the waveform of the second beat signal is about 1/2 wavelength or more in order to reliably detect a change in the phase and frequency of the second beat signal. good.

According to a second aspect of the present invention, the frequency modulating means according to the first aspect comprises a sweep voltage generating means for generating a sweep voltage, and a voltage control oscillating means for outputting a frequency corresponding to the sweep voltage. It is characterized by having.

According to a third aspect of the present invention, in the second aspect, the temperature correction means changes the sweep voltage. By changing the sweep voltage, changes in the phase and frequency of the second beat signal can be corrected, and therefore, the relative distance can be measured using the beat signal without being affected by temperature.

According to a fourth aspect of the present invention, in the third aspect, the temperature correction means changes a slope voltage of the sweep voltage when a cycle of the second beat signal changes. When the position of the second beat signal is changing, the base voltage of the sweep voltage is changed. The base voltage and the slope voltage can be changed according to changes in the position and the frequency of the second beat signal, respectively.

[0015] The invention according to claim 5 provides the invention according to claims 2 to 4.
The sweep voltage generating means according to any one of the above,
It is characterized by comprising an integrator that integrates a slope base voltage and an adder that adds a base voltage to an output of the integrator. A smooth sweep voltage can be generated by adding the base voltage to the value obtained by integrating the slope base voltage with the integrator.

[0016]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing one embodiment of the relative distance measuring device of the present invention.

In the figure, 3 m with eight supporting wheels
The measuring unit 12 is attached to the center of the straight ruler 10 of FIG. The transmitting / receiving antenna 14 is connected to the measuring unit 12, and the microwave is radiated from the transmitting / receiving antenna 14 toward the road surface 5, and the signal reflected from the road surface 5 is received by the transmitting / receiving antenna 14. While moving the device on the road surface 5 by the wheels, the measuring unit 12 transmits a transmission signal (hereinafter, referred to as an FM-CW signal) that has been frequency-modulated over a wide band to the transmission / reception antenna 14 as described later. Using the FM-CW signal, the transmitting / receiving antenna 1
The flatness of the road surface 5, that is, the spatial change of the road surface, is detected by detecting the phase change of the received signal from the road surface 4.

FIG. 2 shows the transmitting / receiving antenna 14 and the measuring section 12.
The detailed block diagram of FIG. The measuring unit 12 is roughly divided into an attenuator 17, circulators 15, 16, an RF amplifier 2
1, FM-CW module 18, computer 20, D
/ A converter 28 and A / D converters 30 and 38. The FM-CW module 18 further includes a voltage-controlled oscillator 22, a first RF circuit 23, and a first RF circuit 23. A 2RF circuit 33 is provided.

The first RF circuit 23 comprises a power divider 24 and a smoothing circuit 26. The smoothing circuit 26 has diodes D and D connected to the power divider 24 with opposite polarities.
And a capacitor C and a resistor R connected in parallel. Similarly, the second RF circuit 33 includes a power divider 34 and a smoothing circuit 36. The smoothing circuit 36 has diodes D and D connected to the power divider 34 with opposite polarities.
And a capacitor C and a resistor R connected in parallel.

The power divider 24 of the first RF circuit 23
Attenuator 17 and RF through circulator 16
The attenuator 17 and the RF amplifier 21 are connected to the transmitting / receiving antenna 1 via the circulator 15.
4 is connected. D / A connected to computer 20
The converter 28 is connected to the voltage controlled oscillator 22. The first RF circuit 23 and the second RF circuit 33 are connected to the computer 20 via A / D converters 30 and 38, respectively. Further, the computer 20 has a display 32.
Is connected.

The power divider 34 of the second RF circuit 33
Is connected to one end of a cable 40. Cable 40
The other end of the cable 40 is grounded and short-circuited.
In this embodiment, the length is approximately equal to a predetermined distance d which is a reference for measurement. However, the length of the cable 40 can be any length. Preferably, the length of the waveform of a beat signal E2 to be described later is １ ／ wavelength or more, and more preferably, it is long enough to enter one wavelength or more.

The operation of the above configuration will be described. First, when a sweep voltage signal is output as a digital signal from the computer 20, the sweep voltage signal is converted into an analog signal by the D / A converter 28, and the output sweep voltage E0 is applied to the voltage control oscillator 22. And the voltage-controlled oscillator 22 generates an FM-CW signal frequency-modulated according to the sweep voltage E0. FIG. 3 shows a waveform example of the sweep voltage E0. In this example, the sweep voltage E0 changes by 2 V to 8 V in 3 ms, and the base voltage (sweep start voltage)
Is 2V and the slope voltage is 6V. In response to this, the voltage controlled oscillator 22 sets its frequency f to 9.25G.
And outputs an FM-CW signal swept by 10 Hz to 10.75 GHz.

The FM-CW signal from the voltage controlled oscillator 22 is applied to a reference signal e0 by a power divider 24 of a first RF circuit 23.
After being adjusted to an appropriate transmission level by the attenuator 17, the transmission signal e1 is converted into a microwave from the transmission / reception antenna 14 and radiated toward the road surface 5. The signal reflected by the road surface 5 is received by the transmission / reception antenna 14, amplified by the RF amplifier 21, and received by the reception signal e2.
Is input to the power divider 24 of the first RF circuit 23 and is combined with the transmission signal e1. Here, the transmission signal e1 is

[0024]

(Equation 1) Then, the received signal e2 becomes

[0025]

(Equation 2) It is expressed as Here, a is the received signal level, τ is FM-CW
The delay time before exiting the module 18 and returning. Assuming that the distance between the transmitting / receiving antenna 14 and the road surface 5 is d, the delay time for reciprocating the d is τ ₁ , the fixed delay time in the circuit is τ ₀ , and the speed of light is c,

[0026]

(Equation 3) It is expressed as Therefore, equation (2) is

[0027]

(Equation 4) Becomes Therefore, in the power divider 24, the input signal e2 of Expression (4) and the reference signal e0 are combined, so that e0 = e
If it is set to 1, the output from the power distributor 24 is (1)
From the equation and the equation (4),

[0028]

(Equation 5) However, when the low frequency component is extracted as the beat signal E1 from the power divider 24, the first term can be ignored,

[0029]

(Equation 6) Is obtained. Here, if the sweep voltage E0 is swept as shown in FIG.

[0030]

(Equation 7) It can be expressed as. Here, B is the frequency sweep width, T
Is the frequency sweep time, and f ₀ is the center frequency. Substituting equation (7) into equation (6) and rearranging,

[0031]

(Equation 8) Becomes here,

[0032]

(Equation 9) Where f _b is the beat frequency and λ is the wavelength of the microwave.

Note that the fixed phase term 2πf in the equation (8)
_{Since 0} τ ₀ can be expressed as 2nπ (n is an integer) without loss of generality,

[0034]

(Equation 10) It can be expressed as.

The equation (10) shows that the transmission signal e1 and the reception signal e2
Can be regarded as a beat signal which is a low-frequency component obtained by mixing the signals, and the phase of the beat signal is a change amount Δd of the distance d between the transmitting antenna 14 and the receiving antenna 16 and the road surface 5 is a half wavelength (λ / Each time 2) is exceeded, 2π, that is, 36
It can be seen that it changes by 0 degrees.

Here, as a specific example, the frequency sweep time T =
3 ms, frequency sweep width B = 1.5 GHz, center frequency f
_{When 0} = 10 GHz, d = 15 cm, and a fixed delay time τ ₀ = 2 ns in the circuit, the beat frequency f _b and the wavelength λ are given by the following equations (9).

[0037]

[Equation 11] Becomes Also, the phase of the beat signal in equation (10) is the distance d
But,

[0038]

(Equation 12) If it changes only, it will change 360 degrees. Therefore, if the phase change of the beat signal E1 in the equation (10) is measured, the change amount Δd from d = 15 cm, that is, the flatness of the road surface 5 can be measured. Although a function of the beat frequency f _b is also d, the variation Δd of d is as long as about a half wavelength, believed change in the beat frequency f _b is negligible, the beat frequency f _b is constant.

The beat signal E1 output from the first RF circuit 23 is sent to the computer 2 via the A / D converter 30.
After that, digital processing is performed in the computer 20. Of course, the A / D converter 30
Instead of conversion and processing by the computer 20, it is also possible to perform analog processing.

As shown in FIG. 4, the computer 20 has a bandpass filter (BPF) 42, 4
3. Reference waveform output unit 48, phase output unit 49, relative distance change amount calculation unit 56, wave number change amount detection unit 58, cycle / zero cross detection unit 60, temperature correction unit 64, and reference sweep voltage generation unit 66 Can be. Further, the phase output unit 49 further includes multiplication units 44 and 46, an addition unit 50,
52, and a dividing unit 54.

The processing in each section will be described below.

First, assuming that the beat signal E1 is A / D converted by the A / D converter 30 at a sampling interval Δt, the beat signal E1 is

[0043]

(Equation 13) Is converted into a digital signal (hereinafter, referred to as an AD signal). Since the frequency of this signal is f _b = 1.5 kHz, if the above-mentioned AD signal is passed through a band-pass filter (BPF) 42 having the beat frequency f _b as a center frequency, the noise and the reflection other than the road surface 5 are reflected. The beat signal due to the body is removed, and the measurement accuracy is improved. Since the beat frequency f _b is fixed at d = 15 cm, a narrow band filter can be used as the band pass filter (BPF) 42.

FIG. 5A shows this band-pass filter 42.
7 is a waveform of a beat signal that has passed through. The effect of the filter remains immediately after the input, but after 0.5 ms, it settles down to a steady state, and the waveform of equation (13) is obtained. Therefore, in the future, in FIG. 5A, the processing will be performed using three waves of 0.5 ms and later that provide a beautiful waveform. In order to measure the change amount Δd of the distance d from the phase term of the equation (13), first, two signals having three waves at m = 0 to N and orthogonal to each other,

[0045]

[Equation 14] As a reference waveform, a reference waveform output unit 48
Prepare in advance. This reference waveform may be stored in a memory as a table, or may be calculated and output each time. As shown in FIG. 4, when the multiplication units 44 and 46 multiply the expression (13), their outputs are as follows.

[0046]

(Equation 15) here,

[0047]

(Equation 16) In other words, if Δt is selected so that the frequency of the reference waveform becomes the beat frequency f _{b in} Expression (13), Expressions (16) and (17) become as follows.

[0048]

[Equation 17] FIG. 5B illustrates two reference waveforms of the reference waveform output unit 48, each of which includes three waveforms within 2 ms. Also, since the outputs of the multiplication units 44 and 46 are expressed by the equations (19) and (20), the result of executing the multiplication for 2 ms where the reference waveform exists is as follows:
The result is as shown in FIG. In FIG. 5C, the vibration component is superimposed on the offset. This offset component corresponds to the DC component of the second term in the equations (19) and (20), and is the component to be obtained. . On the other hand, the vibration component
The vibration term of the first term in equations (19) and (20),
Since it is an unnecessary component, it must be removed. Therefore, FIG.
The oscillation terms are removed by calculating the sum of the multiplication results in the adders 50 and 52. That is, taking the sum of equation (19),

[0049]

(Equation 18) In the sum, the sum of the first term is exactly six waves in the oscillation period between m = 1 to N, so it is canceled to be 0 and removed.

[0050]

[Equation 19] Is obtained. If the sum is similarly calculated for equation (20),

[0051]

(Equation 20) Becomes Next, if the division unit 54 calculates the ratio of the expressions (22) and (23),

[0052]

(Equation 21) Is obtained, and the change amount Δd of the distance d can be obtained from this equation as follows. For convenience, d = d ₀ + Δ
d and

[0053]

(Equation 22) Equation (24) gives the following equation:

[0054]

(Equation 23) So, if we take tan ^-1 ,

[0055]

(Equation 24) Because

[0056]

(Equation 25) It is. In the relative distance change amount calculation unit 56, (28)
The change amount Δd can be calculated by performing the calculation of the equation.
However, in equation (27), tan ^-1 is determined by considering the positive and negative polarities of SumSin and SumCos.

[0057]

(Equation 26) Is in the range

[0058]

[Equation 27] Δd can be directly obtained from the equation (28).

In this example, since λ = 3 cm,

[0060]

[Equation 28] Can be determined by equation (28).
Thus, the change in the relative distance can be obtained in the range of ± λ / 4.

In the relative distance change amount calculating section 56, if the unevenness of the road surface 5 exceeds the range of the equation (31),
Using the fact that the wave number of the beat signal AD [m] (the number of waves falling within a unit time) in (a) changes at a constant rate for each λ / 4 of the boundary value of equation (30), the measurement range of Δd is changed. Can be expanded. For example, the frequency sweep width during the frequency sweep time T is B, and the wave number w of the beat signal entering during the frequency sweep time T is obtained from the equation (9).

[0062]

(Equation 29) Where the wave number when the change in τ is Δτ is

[0063]

[Equation 30] Only change. In this example, the frequency sweep width B during 2 ms
Is B = 1 GHz. The change .DELTA.w of the wave number w of the beat signal falling within this 2 ms is due to the fact that the distance d to the road surface 5 is now .DELTA.
Assuming that d = λ / 4, Δτ = λ / 2c
Therefore, by substituting λ = 3 cm and B = 1 GHz into the equation (33),

[0064]

(Equation 31) Becomes That is, a change of Δd = λ / 4 results in a change of 0.05 wave number. Therefore, in the wave number change amount detection unit 58,
The amount of change in the wave number is measured, and every time the wave number changes by 0.05, +1 is added when the wave number increases, and -1 is added when the wave number decreases. The change phase is added to the value of Δd obtained by equation (28),

[0065]

(Equation 32) By the formula, the measurable variation width of the road surface unevenness can be expanded to about 2 to 3 cm which is practically necessary. The wave number change amount detection unit 58 may be any unit that measures the wave number or the frequency, and may be configured by, for example, an FFT (Fast Fourier Transformer).

The continuous recording of the variation Δd obtained by the equation (35) immediately indicates the flatness of the road surface 5.
Further, in order to express the flatness numerically, the standard deviation and variance of the recording of Δd can be obtained.

When the temperature changes, the oscillation frequency of the voltage controlled oscillator 22 changes, and the beat signal E1 of the first RF circuit 23 changes. FIG. 6 shows the FM-C
This graph shows the temperature characteristics of the W module 18, where the ordinate represents the oscillation frequency and the abscissa represents the sweep voltage. Ideally, a proportional relationship should be established between the two, but if there is a change in temperature, the oscillation frequency fluctuates as shown in the figure even if the sweep voltage is the same, and the center frequency An error occurs in the measurement because f ₀ also deviates.

To correct this error, the second RF circuit 3
3 is used. The second RF circuit 33 includes the first R
Similarly to the F circuit 23, the FM-
The CW signal is sent to the power divider 34, which splits the CW signal into two waves, a reference signal e 0 and a transmission signal e 3, and the transmission signal e 3 propagates in the cable 40. Since the other end of the cable 40 is short-circuited, the transmission signal e3
Is returned after being totally reflected at the other end, input to the power divider 34 of the second RF circuit 23, and combined with the reference signal e0. Therefore, the above equations (1) to (10) hold as they are, and the beat signal represented by the equation (10) is obtained. However, in the equation (10), d is a constant value determined by the length of the cable 40. That is, since the distance d is constant, if there is no change in the temperature, the beat signal (hereinafter, referred to as beat signal E2) is also constant.

However, the second RF circuit 33
It has basically the same configuration as the first RF circuit 23,
The beat signal E2 output from the F circuit 33 is affected by the same temperature as the beat signal E1, and its cycle and phase change. The beat signal E2 is converted into a digital signal (hereinafter, referred to as a second AD signal) by an A / D converter 38, taken into the computer 20, and has a beat frequency f
band pass filter (BPF) 43 with _b as center frequency
After that, it is input to the period / zero-cross detection unit 60. The cycle / zero-cross detector 60 detects a zero-cross point and a cycle from the second AD signal. The temperature correction unit 64 detects a difference between the zero-cross point and the cycle at a predetermined reference temperature and the zero-cross point and the cycle detected by the cycle / zero-cross detection unit 60, respectively. The reference base voltage and the reference slope voltage generated from the voltage generator 66 are corrected, and the corrected base voltage and slope voltage are calculated.

[0070] For example, a frequency sweep width B is narrowed when the oscillation frequency due to the influence of temperature changes down, (9) beat the beat frequency f _b becomes small, the detected beat period of the beat signal E2 is at the reference temperature by formula Larger than the period. In such a case, the slope voltage is corrected to be larger, and B is returned to the original value.

Further, the base voltage, that is, the relationship between the sweep start voltage and the oscillation frequency also changes depending on the temperature. When the sweep start frequency changes, the phase of the beat signal E2 also changes, and the zero cross point changes. Correction is performed so that the zero-cross point is constant.

FIG. 3 shows an example of the corrected sweep voltage by a two-dot chain line. Thus, the temperature correction unit 64 outputs a sweep voltage signal based on the corrected base voltage and the corrected slope voltage, and outputs this sweep voltage signal to D / D.
By supplying the voltage-controlled oscillator 22 via the A-converter 28 to the voltage-controlled oscillator 22,
2 can be made constant. The correction can be performed by any method such as proportional feedback control or on / off control. With the simple configuration as above,
In addition, temperature correction can be performed online, and highly accurate distance measurement can be performed.

FIGS. 7 and 8 show a modification of the above embodiment, and are diagrams showing the configuration of the sweep voltage generating means. In the example of FIG. 2, the corrected sweep voltage signal generated from the temperature correction unit 64 is supplied to the voltage controlled oscillator 22 via the D / A converter 28. The output is jagged, and there is a possibility that a stable sweep voltage E0 cannot be obtained. Therefore, in this modification, the corrected slope base voltage signal and the corrected base voltage signal output from the computer 20 are converted into analog signals by the D / A converters 72 and 74, respectively, and then the slope base voltage is converted. The integration is performed by the integrator 76. The integrator 76 starts the integration at the rising (or falling) of the sweep gate, and the falling (or rising) of the sweep gate.
Clear the integration with. After the integrated value of the integrator 76 and the base voltage are added by the adder 78, they are amplified by the amplifier 80 and output. Thus, a stable sweep voltage E0 (FIG. 8)
(D)) can be output.

FIG. 9 is a diagram showing a second embodiment of the present invention. In this embodiment, the first RF circuit 23
Is composed of a power distributor 24 and a mixer 25,
The RF circuit 33 includes a power divider 34 and a mixer 35, and the power divider 34 of the second RF circuit 33
The other end of the cable 40 is connected to the mixer 35. The length of the cable 40 is different from that of the first embodiment in that it is approximately twice as long as a predetermined distance which is a reference for measurement and 2d. However, the length of the cable 40 can be an arbitrary length as described above.

FIG. 10 is a diagram showing a third embodiment of the present invention. This embodiment is different from the second embodiment in having a transmitting antenna 14 'and a receiving antenna 14 ".

In the second embodiment, the second RF circuit 33
Are configured in the same manner as the first RF circuit 23, and also in the third embodiment, the second RF circuit 33 is configured in the same manner as the first RF circuit 23. The second RF circuit 33 obtains a second beat signal of the transmission signal and the signal that has returned through the cable 40, and performs temperature correction using the second beat signal. The same can be applied.

Further, D / D in the second and third embodiments
It is a matter of course that the modification shown in FIG. 7 can be used instead of the A converter 28.

[0078]

As described above, according to the present invention,
By changing the frequency modulation of the transmission signal in accordance with at least one of the phase and frequency of the second beat signal obtained at the same time when measuring the relative distance, the effect of temperature is removed, so that the temperature is corrected online, Highly accurate distance measurement can be performed.

[Brief description of the drawings]

FIG. 1 is an overall schematic diagram showing an embodiment of a relative distance measuring device according to the present invention.

FIG. 2 is a detailed block diagram of a measurement unit in FIG. 1;

FIG. 3 is a waveform diagram of a sweep voltage input to the voltage controlled oscillator of FIG.

FIG. 4 is a functional block diagram showing the operation of the computer shown in FIG. 2;

FIG. 5A is a waveform diagram of a beat signal output from a first RF circuit 23 of FIG. 2 and passed through a band-pass filter;
(B) is a waveform diagram of two reference waveforms in FIG. 4, and (c) is a waveform diagram showing an output of the multiplication unit in FIG.

FIG. 6 is a graph showing temperature characteristics of the FM-CW module 18 of FIG.

FIG. 7 is a block diagram illustrating a modified example of the sweep generation unit.

8 is a timing chart of the sweep generation means of FIG. 7, wherein (a) shows a sweep gate, (b) shows a base voltage, (c) shows a slope base voltage, and (d) shows a sweep voltage.

FIG. 9 is a diagram corresponding to FIG. 2, showing a second embodiment of the relative distance measuring device according to the present invention.

FIG. 10 is a diagram corresponding to FIG. 2 showing a third embodiment of a relative distance measuring device according to the present invention.

[Explanation of symbols]

14 transmitting / receiving antenna (transmitting means, receiving means) 14 'transmitting antenna (transmitting means) 14 "receiving antenna (receiving means) 22 voltage controlled oscillator 23 first RF circuit (first transmitting / receiving circuit) 33 second RF circuit (second transmitting / receiving circuit) 40 Cable 56 Relative distance change amount calculation unit (Relative distance change amount calculation unit) 64 Temperature correction unit (Temperature correction unit) 76 Integrator 78 Adder

Claims (5)

[Claims] 1. 100 MH along a path to be measured
A relative distance measuring device that measures a temporal change amount or a spatial change amount of a target distance that changes minutely relative to a predetermined distance by transmitting a radio wave of VHF, UHF, microwave, millimeter wave band or the like of z or more. Frequency modulation means for generating a transmission signal subjected to frequency modulation over a wide band; transmission means for radiating radio waves by the transmission signal along a path to be measured; and transmission path radiated from the transmission means. Receiving means for receiving a radio wave propagated through, a signal transmitted from the frequency modulation means, and a signal received from the receiving means is mixed, and has a frequency and a phase according to a radio wave propagation distance that is a low-frequency component thereof A first transmission / reception circuit that outputs a beat signal; a relative distance change amount calculating unit that measures a temporal change amount or a spatial change amount of the target distance based on the beat signal; A signal for transmitting a signal, a transmission signal from the frequency modulation means, and a signal mixed with the signal propagated through the cable, and having a frequency and a phase corresponding to the propagation distance of the cable, which is a low-frequency component thereof. A second transmission / reception circuit that outputs a 2-beat signal; and a temperature correction unit that changes frequency modulation of the frequency modulation unit in accordance with at least one of a change in a cycle and a phase of the second beat signal. Relative distance measuring device. 2. The frequency modulation unit according to claim 1, further comprising: a sweep voltage generation unit configured to generate a sweep voltage; and a voltage controlled oscillation unit configured to output a frequency corresponding to the sweep voltage. Relative distance measurement device. 3. The relative distance measuring device according to claim 2, wherein said temperature correcting means changes said sweep voltage. 4. The temperature correction means changes a slope voltage of the sweep voltage when the cycle of the second beat signal changes, and when the phase of the second beat signal changes, 4. The relative distance measuring device according to claim 3, wherein a base voltage of the sweep voltage is changed. 5. The sweep voltage generating means includes an integrator for integrating a slope base voltage, and an adder for adding a base voltage to an output of the integrator. The relative distance measuring device according to claim 1.