JP3768511B2 - Distance measuring device, distance measuring method, and distance measuring program - Google Patents

Description

  The present invention relates to a distance measuring device, a distance measuring method, and a distance measuring program, and more specifically, a distance measuring device and a distance measuring method for measuring a distance from an electromagnetic wave radiated to an object to be measured from the object to be measured. And a distance measurement program.

  Current distance measurement methods using a microwave that are widely used are broadly classified into an FMCW (frequency modulation continuous wave) method and a pulse radar method.

  The FMCW system transmits a continuous wave that has been swept in frequency, and obtains the distance to the object to be detected from the frequency difference between the radiation signal and the reflected signal (for example, see Patent Document 1).

  On the other hand, the pulse radar system is a method for obtaining a distance to an object to be detected by measuring a time from when a pulse signal is transmitted until it is reflected by a measurement object and returned (for example, Patent Document 2).

  Each of the above two measurement methods has high measurement accuracy, but has the following problems.

  First, for the FMCW method, the measurement accuracy is determined by the sweep width of the radiation frequency as expressed by the relational expression of measurement accuracy = light speed / (2 × frequency sweep width). Need to use a wide bandwidth. However, in the frequency band of 24.15 GHz that is normally used by the distance measuring device and is classified by the Radio Law for mobile object detection sensors, due to the regulation of specific low power radio, the bandwidth is effective frequency 24.1. The use is limited to 0.1 GHz of 24.2 GHz. For this reason, when using the FMCW microwave level meter outdoors, there is a limit in measurement accuracy because it is not possible to obtain a sufficient bandwidth, and it becomes difficult to measure short distances. Become.

  Next, regarding the pulse radar system, in order to generate a very short electric pulse in the radiator, a wide radio wave bandwidth is required in terms of components. For example, the bandwidth required to generate an impulse of 2n seconds is 2 GHz. Accordingly, in this case as well, the use in the outdoors is restricted due to the limitation of the bandwidth defined by the Radio Law, and it becomes difficult to measure near distances because a shorter electrical pulse cannot be used.

  Therefore, in order to solve these problems, it is necessary to satisfy the radio wave band and radiation gain specified by the Radio Law, and to maintain high measurement accuracy even in close-range measurement, regardless of the measurement distance. Needed.

  In the above two measurement methods, since the use bandwidth is wide, it cannot be used as a specific low power radio classified by the Radio Law, but it can be used as a weak power radio with reduced output power. . However, since the power of the reflected signal becomes very small by reducing the output power of the radiation signal, there is a problem that it is easily affected by noise when measuring a long distance.

  Furthermore, recently, a distance measuring device having high measurement accuracy even at a short distance has been proposed (see, for example, Patent Document 3).

  FIG. 14 is a schematic block diagram showing the configuration of the distance measuring device proposed in Patent Document 3. As shown in FIG.

Referring to FIG. 14, the distance measuring device emits a transmission source 60 that outputs a signal of a predetermined frequency, a transmission unit 70 that emits an electromagnetic wave having the same frequency as the output signal of transmission source 60, and a transmission unit 70. In order to detect the amplitude of the standing wave S formed by interference between the reflected electromagnetic wave (hereinafter also referred to as traveling wave D) and the reflected wave R reflected by the measurement objects M _{1 to} M _n (n is a natural number). And a signal processing unit 90 that calculates a distance from the detection signal of the detection unit 80 to the measurement object M _k (k is a natural number equal to or less than n).

  The transmission source 60 includes a transmission unit 62 and a frequency control unit 64. The transmitter 62 outputs a signal having a constant frequency f controlled by the frequency controller 64 to the transmitter 70. The frequency control unit 64 also outputs information regarding the frequency f sent to the transmission unit 62 to the signal processing unit 90.

  Here, the principle of the measurement method in the distance measuring apparatus of FIG. 14 will be briefly described.

First, as shown in FIG. 14, the traveling wave D emitted from the transmission unit 70 interferes with the reflected wave R reflected by the measurement object M _k , thereby causing the transmission unit 70 and the measurement object M _k to interfere with each other. A standing wave S is formed in the propagation medium.

At this time, the received power signal p (f, x) obtained by observing the standing wave S with the detection unit 80 provided at the observation point xs on the x axis is a sine wave with respect to the frequency f of the traveling wave D. Function (cos function). In particular, when there are reflections from a plurality of measurement objects, a plurality of sine waves having different periods are combined corresponding to each measurement object. The period of each sine wave is inversely proportional to the distance from the observation point to the measurement object _Mk . The distance measuring device of FIG. 14 measures the distance to the measuring object _Mk using this property.

  That is, the traveling wave D emitted from the transmitter 70 is

If the distance to each measurement object is d _k , the reflected wave R by each measurement object M _k can be expressed as follows.

Here, c is the speed of light, f is the transmission frequency, A is the amplitude level of the traveling wave D, and d _k is the distance to the measurement object M _k . Γ _k is the magnitude of the reflection coefficient of the measurement object M _k and includes a propagation loss. φ _k is a phase shift amount in reflection.

  The standing wave S is generated by additive synthesis of the traveling wave D and the reflected wave R, and the power signal p (f, x) is obtained from the equations (1) and (2):

It is represented by In general, the level of the reflected wave R is very small compared to the traveling wave D, and it is considered that γ _k << 1. Therefore, the second and higher order terms of γ _k can be regarded as almost 0 and ignored. Therefore, the received power signal p (f, x) is expressed as follows:

FIG. 15 is a waveform diagram of the received power signal p (f, 0) observed at a position where x = x _s = 0 when one measurement object is located at a distance d.

  Referring to FIG. 15, the received power signal p (f, 0) is periodic with respect to the frequency f, and the period is c / 2d, which is inversely proportional to the distance d. Accordingly, if the received power signal p (f, 0) is Fourier-transformed to extract period information, the distance d to the measurement object can be obtained. Note that the Fourier transform formula is applied to the received power signal p (f, 0) in equation (3).

A profile P (x) obtained by applying is given by Equation (6).

However,

f ₀ is the intermediate frequency of the transmission frequency band, and f _W is the bandwidth of the transmission frequency.

As described above, in the distance measuring apparatus of FIG. 14, the distance to the measurement object M _k depends only on the fluctuation period of the received power signal with respect to the traveling wave transmission frequency, and after transmitting the electromagnetic wave by the transmitting unit 70. Since it is not affected by the time until it returns to the detection unit 80, it can measure with higher accuracy even at a short distance than the conventional FMCW method and pulse radar method.
JP 7-159522 A JP-T 8-511341 Japanese Patent No. 3461498

Here, in the conventional distance measuring apparatus shown in FIG. 14, the received power signal p (f, 0) of the standing wave S is Fourier-transformed by the equation (6), so that in the transmission frequency bandwidth f _W If the received power signal does not have a periodicity of one cycle or more, accurate cycle information cannot be extracted.

FIG. 16 shows that the distance d _k of the measuring object M _k varies between 0 m and 5 m under the conditions of f ₀ = 24.0375 GHz, f _W = 75 MHz, γ _k = 0.1 and φ _k = π. The size of the profile | P (x) | when obtained is obtained by numerical calculation using equations (4) and (6). Note that p (f, 0) -A ² obtained by subtracting the level A ^{2 of the} traveling wave is Fourier-transformed, so the first term of Equation (4) is removed.

Referring to FIG. 16, the profile size | P (x) | corresponds to the region where x is positive and x corresponds to the component of the second term and the component of the third term of Equation (6). Waveforms each having a maximum value in the negative region. In the conventional distance measuring apparatus, since the measurement object M _k is always located in a region where x is positive, the maximum value of one region (x> 0) of this waveform is extracted and corresponds to the maximum value. The value of x to be used is the position of the measuring object _Mk .

However, when the distance d is small, as shown in FIG. 16, the peak of the profile | P (x) | does not indicate the exact position of the measuring object _Mk . This is because, as the distance d becomes smaller, the two maximum values interfere with each other, thereby disturbing the waveform. In the case of FIG. 16, it can be seen that the distance can be accurately measured when the distance d is 2 m or more, but a correct measurement value is not obtained when the distance d is 2 m or less.

FIG. 17 is a diagram illustrating the relationship between the distance (measured value) to the measurement object _Mk derived from the profile of FIG. 16 and the actual distance to the measurement object _Mk .

Referring to FIG. 17, when the distance to measurement object _Mk is 2 m or more, the measurement value exactly matches the distance to actual measurement object _Mk. It turns out that it is remarkably inferior. This is due to the disturbance of the profile at a short distance shown in FIG. 16, and suggests that 2 m is the limit of the distance that can be measured.

Specifically, when the distance d = 2 m, the period of the reception power signal p (f, 0) is c / (2 × 2) = 75 MHz, so that the transmission frequency bandwidth f _W = 75 MHz is just the reception power. This corresponds to a band for one period of the signal. Therefore, since a correct measurement value can be obtained if the distance is longer than the shorter period, the minimum detection distance d _min is

It can be expressed as

  Here, as described above, when the distance measuring device is used as the specific low-power radio, the usable frequency bandwidth is limited by the domestic radio law. For example, in the “moving body detection sensor”, if the frequency band in the 24.15 GHz band is used, the allowable value of the occupied frequency bandwidth is defined as 76 MHz. Therefore, as in the case of FIG. 16, a large error occurs in the measurement result in the position measurement at a short distance of about 2 m or less.

  The measurement error described above is a problem peculiar to a short distance in which the received power signal is 1 period component or less, but in the case of a distance (medium distance and long distance) including a periodicity of 1 period component or more. Even if there is, an error of several centimeters occurs in the measurement result.

FIG. 18 is a diagram illustrating the relationship between the measurement value obtained from the profile when the distance to the measurement object _Mk is a medium distance level and the distance to the actual measurement object _Mk .

Referring to FIG. 18, when the position of measurement object M _k is changed every 2 mm in the interval from distance d = 4.9 m to d = 5.0 m, which is a medium distance level, the measurement result is about ± 2. It can be seen that an error of about 5 cm occurs.

FIG. 19 is a diagram illustrating a measurement error when the position of the measurement object _Mk is further changed to the far distance level (d = 10 m).

As is apparent from FIG. 19, measurement is performed even when the measurement object M _k is far from the distance measuring device and is located at a distance d = 10 m where a sufficient periodic component can be seen in the received power signal. The result has an error of about ± 5 cm.

  As a means for reducing the measurement error, first, when the received power signal is subjected to Fourier transform, a signal range including at least one period component is extracted from the received power signal and subjected to Fourier transform. It is possible to repeat the calculation over a range of components or more and obtain the sum of each time domain from the Fourier transformed data.

  Secondly, the use bandwidth of the transmission frequency is the same, and the Fourier transform of the received power signal obtained by slightly shifting the initial frequency to be transmitted is repeated at least in the range of the half period component or more. It is possible to obtain the sum of each time domain from each Fourier transformed data.

  FIG. 20 shows the processing result when the received power signal is multiplexed according to such means. As apparent from FIG. 20, the error seen in the measurement result is improved to about ± 1 cm in the range where the distance d reaches 10 m.

  However, since such multiple processing includes a plurality of Fourier transform processes, it takes a considerable amount of time for the processing, and thus has a problem that it is not suitable for applications that require quick response.

Furthermore, the distance measuring apparatus of FIG. 14 has a problem that an error occurs in the measurement result even when the measurement object _Mk is moving on the measurement axis (x-axis) at a constant speed.

Specifically, when the measurement object M _k is moving, in the reception power signal of the standing wave S detected by the detection unit 80, the reception frequency changes with time in the propagation medium with respect to the transmission frequency f. A Doppler shift occurs that shifts by a proportional frequency. The shift amount at this time acts in the direction of decreasing the reception frequency when the measurement object _Mk approaches, and in the direction of increasing the reception frequency when the measurement object _Mk moves away.

FIG. 21 is a diagram illustrating an example of a measurement result when the measurement object M _k is moving on the x axis at a constant speed. In the measurement of FIG. 21, for example, it is assumed that the measurement object M _k located at a distance d = 5 m is moving forward and backward at a speed of 2.0 m / sec from a stationary state. As for the transmission frequency, it is assumed that an upward sweep that sweeps while increasing within the use bandwidth and a downward sweep that sweeps while decreasing within the use bandwidth are performed.

Referring to FIG. 21, the measurement results show that the actual measurement object M increases as the moving body speed of the measurement object _Mk increases both during the upward sweep (corresponding to the solid line) and during the downward sweep (corresponding to the dotted line). It can be seen that the error with respect to the position of _k (5 m) increases. It should be noted that, at any time of sweeping, the measurement result shows a waveform folded at 0 m, which is due to the conventional distance measurement method that extracts only the positive result among the FFT processing results.

  As means for reducing such a measurement error, a measurement result (hereinafter also referred to as first position information) obtained by Fourier-transforming a reception power signal obtained by increasing and sweeping the transmission frequency, and decreasing the transmission frequency By obtaining a measurement result (hereinafter also referred to as second position information) obtained by performing Fourier transform on the received power signal obtained by sweeping, and performing a correction process for averaging the first and second position information And a method for detecting the position of the moving measurement object.

The result of correction processing according to this method is indicated by a thick solid line in FIG. In the sweep time of 20 ms, 5 m, which is the correct position of the measuring object _Mk , is calculated in the range where the moving body speed is less than ± 0.8 m / s.

FIG. 22 is a diagram illustrating an example of a measurement result when the sweep time is further shortened in the measurement of FIG. The measurement in FIG. 22 is performed by setting the distance (d = 5 m) of the measurement object M _k and the moving body speed to the same conditions as in FIG. 21 and shortening only the sweep time from 20 milliseconds to 10 milliseconds. .

Referring to FIG. 22, the error in the measurement result increases as the moving object speed of measurement object _Mk increases both in the upward sweep (corresponding to the solid line) and in the downward sweep (corresponding to the dotted line). . This tendency is common to the result of the sweep time of 20 ms shown in FIG. Furthermore, when the above correction processing is performed on these measurement results, the result indicated by the thick solid line in FIG. 22 is obtained.

As is apparent from the result of this correction processing, by shortening the sweep time, the range of the moving body speed at which the correct position of the measurement object _Mk can be obtained is less than ± -1.5 m / s, and the measurement object that can be corrected It can be seen that the speed range of the object _Mk is widened.

However, in such a method, since the speed range of the measurement object _Mk that can be corrected depends on the transmission frequency sweep time, when the measurement object _Mk moving at high speed is targeted, the sweep time Therefore, it is necessary to provide a new oscillator that can be varied at high speed stably.

  Therefore, an object of the present invention is to provide a distance measuring device, a distance measuring method, and a distance measuring program capable of accurately measuring a short distance even in a narrow radiation frequency band.

  Another object of the present invention is to provide a distance measuring device, a distance measuring method, and a distance measuring program capable of accurately measuring even a moving measurement object.

According to an aspect of the present invention, there is provided a distance measuring device that measures a distance to an object to be measured, a transmission source that outputs a signal having a predetermined transmission frequency and a predetermined bandwidth, and a signal having the same frequency as the signal. A transmitter that generates an electromagnetic wave and radiates the object to be measured; a detector that detects a power signal of a standing wave formed between the object to be measured by the electromagnetic wave and the reflected wave of the electromagnetic wave; A signal processing unit that calculates a distance to the measurement object by calculating a relationship between the power signal of the standing wave and the transmission frequency. The detection unit is arranged corresponding to each of a plurality of observation points provided on the detection axis with the traveling direction of the electromagnetic wave as a detection axis, and detects a power signal of a standing wave at each corresponding observation point. Includes multiple detectors. The signal processing unit includes a plurality of detectors in the plurality of detected constant component from the power signal of the standing wave, an analysis signal generating means for generating an analysis signal to calculate the amplitude change component and a phase change component, the analytic signal calculating the profile by converting Fourier, and a Fourier transform means for obtaining a distance from the maximum value of the profile to the measurement object.

  Preferably, the plurality of observation points are provided on arbitrary positions between the transmission unit and the measurement object on the detection axis.

  Preferably, the number of measurement objects is at least one.

  Preferably, the transmission source sweeps up the predetermined transmission frequency by increasing the predetermined bandwidth at a predetermined step in a predetermined step and the predetermined transmission frequency by decreasing the predetermined transmission frequency by a predetermined step. And descending sweep means. The signal processing unit uses the distance to the measurement object obtained by the Fourier transform unit according to the ascending sweep means as the first position information, and the distance to the measurement object obtained by the Fourier transform means according to the descending sweep means. It further includes means for holding the distance as the second position information, and correction means for averaging the held first and second position information to derive the distance to the true measurement object.

According to another aspect of the present invention, there is provided a distance measuring method for measuring a distance to a measurement object, the step of outputting a signal having a predetermined transmission frequency and a predetermined bandwidth, and a signal having the same frequency as the signal. Generating an electromagnetic wave and radiating the electromagnetic wave to the measurement object; detecting a standing wave power signal formed between the electromagnetic wave and the reflected wave of the electromagnetic wave; and the detected standing wave Calculating a distance to the measurement object by calculating a relationship between the wave power signal and the transmission frequency. The step of detecting the power signal of the standing wave uses the traveling direction of the electromagnetic wave as a detection axis, and the corresponding observation is performed by a plurality of detectors arranged corresponding to each of the plurality of observation points provided on the detection axis. Detecting a standing wave power signal at the point. The step of calculating the distance to the measurement object includes a step of calculating a constant component, an amplitude change component, and a phase change component from a plurality of standing wave power signals detected by a plurality of detectors, and generating an analysis signal. calculates a profile analysis signal into Fourier, and determining the distance from the local maximum of profile to the measurement object.

  Preferably, the plurality of observation points are provided on arbitrary positions between the transmission unit and the measurement object on the detection axis.

  Preferably, the number of measurement objects is at least one.

  Preferably, the step of outputting a signal having a predetermined transmission frequency and a predetermined bandwidth includes a step of increasing the predetermined transmission frequency by a predetermined step with a predetermined bandwidth, and sweeping the predetermined transmission frequency. And sweeping down in a predetermined step with a bandwidth of. The step of calculating the distance to the measurement object uses the distance to the measurement object obtained by the Fourier transform when the up sweep is performed as the first position information, and the measurement object obtained by the Fourier transform when the down sweep is performed. The method further includes the step of holding the distance to the object as the second position information, and the step of deriving the distance to the true measurement object by averaging the held first and second position information.

According to another aspect of the present invention, there is provided a distance measurement program for measuring a distance to an object to be measured, the step of outputting a signal having a predetermined transmission frequency and a predetermined bandwidth to a computer, A step of generating an electromagnetic wave of the same frequency and radiating it to a measurement object; a step of detecting a power signal of a standing wave formed between the measurement object by the electromagnetic wave and a reflected wave of the electromagnetic wave; and detection The step of calculating the distance to the measurement object is performed by calculating the relationship between the power signal of the standing wave and the transmission frequency. The step of detecting the power signal of the standing wave uses the traveling direction of the electromagnetic wave as a detection axis, and the corresponding observation is performed by a plurality of detectors arranged corresponding to each of the plurality of observation points provided on the detection axis. comprising the step of detecting a power signal of the standing wave at the point. The step of calculating the distance to the measurement object includes a step of calculating a constant component, an amplitude change component, and a phase change component from a plurality of standing wave power signals detected by a plurality of detectors, and generating an analysis signal. calculates a profile analysis signal into Fourier, and determining the distance from the local maximum of profile to the measurement object.

  Preferably, the plurality of observation points are provided on arbitrary positions between the transmission unit and the measurement object on the detection axis.

  Preferably, the number of measurement objects is at least one.

  Preferably, the step of outputting a signal having a predetermined transmission frequency and a predetermined bandwidth includes a step of increasing the predetermined transmission frequency by a predetermined step with a predetermined bandwidth, and sweeping the predetermined transmission frequency. And causing the computer to execute a step of descending and sweeping in a predetermined step with a bandwidth of. The step of calculating the distance to the measurement object uses the distance to the measurement object obtained by the Fourier transform when the up sweep is performed as the first position information, and the measurement object obtained by the Fourier transform when the down sweep is performed. And causing the computer to further execute a step of holding the distance to the object as the second position information and a step of deriving a distance to the true measurement object by averaging the held first and second position information. .

  According to the present invention, it is possible to realize a distance measuring apparatus capable of measuring a measurement object from a distance of 0 m with high measurement accuracy even in a limited transmission frequency bandwidth.

  In addition, even when the measurement object is moving at high speed, it is possible to accurately measure the distance without depending on the sweep time by applying correction processing to the measurement result obtained by sweeping the transmission frequency up and down. Can do.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same reference numerals indicate the same or corresponding parts.

[Embodiment 1]
1 is a circuit diagram showing a basic configuration of a distance measuring apparatus according to Embodiment 1 of the present invention.

Referring to FIG. 1, the distance measuring device includes a transmission source 10 that transmits a signal having a constant transmission frequency f, a transmission unit 20 that emits an electromagnetic wave having the same frequency f as the transmitted signal, and a transmission unit 20. A standing wave S formed by interference between an output electromagnetic wave (hereinafter also referred to as traveling wave D) and an electromagnetic wave (hereinafter also referred to as reflected wave R) reflected from measurement objects M _{1 to} M _n is detected. a detection unit 30 that the reception power signal of the standing wave S detected by the detection unit 30 and arithmetic processing, a signal processing unit 40 for calculating the distance d ₁ to d _n between the measurement object M ₁ ~M _n Is provided.

  The transmission source 10 includes a transmission unit 12 that outputs a signal having a constant frequency f, and a frequency control unit 14 that controls the frequency f of the signal output from the transmission unit 12.

  The transmission unit 12 is configured by, for example, a voltage controlled oscillation circuit (VCO: Voltage Controlled Oscillator), and outputs a signal having a predetermined transmission frequency f based on a control signal from the frequency control unit 14.

  The frequency control unit 14 is composed of, for example, a phase detector, detects the phase difference between the reference oscillation signal from the signal processing unit 40 and the feedback signal fed back from the transmission unit 12, and increases or decreases the oscillation frequency of the VCO. Output a control signal.

  In the transmission unit 12, the VCO receives this control signal and adjusts the oscillation frequency, so that a signal whose frequency and phase coincide with the reference oscillation signal and controlled to a predetermined transmission frequency f is output. .

The transmission unit 20 is constituted by an antenna, for example, and has the same frequency f as the output signal of the transmission unit 12 in a propagation medium such as air or water or in a vacuum existing between the antenna and the measurement objects M _{1 to} M _n. Are emitted in the measurement axis (x-axis) direction.

The detection unit 30 includes a plurality of detectors such as an antenna and an amplitude detector. Each detector is arranged for each of a plurality of observation points (for example, x = 0, x ₁ , x ₂ ) provided on the x axis. The plurality of detectors receive the reception power signals p (f, 0), p (f, x ₁ ), p (f, x) of the standing wave S at the corresponding observation points (x = 0, x ₁ , x ₂ ). ₂ ) is detected.

The signal processing unit 40 is connected to the detection unit 30 and receives reception power signals p (f, 0), p (f, x ₁ ), and p (f, x ₂ ) detected at each observation point.

The signal processing unit 40 includes an analysis signal generation unit 42 that generates an analysis signal from a plurality of received power signals p (f, 0), p (f, x ₁ ), and p (f, x ₂ ), and the generated analysis And a Fourier transform unit 44 that calculates a profile P (x) by Fourier transforming the signal. The analysis signal generation unit 42 and the Fourier transform unit 44 are integrally configured by, for example, a digital signal processor (DSP). Thereby, the arithmetic processing in each unit is executed in software according to a program stored in advance.

  As described above, the configuration of the distance measuring device according to the present embodiment is the same as the basic configuration of the conventional distance measuring device shown in FIG. However, it differs from the conventional distance measuring device in that a plurality of detectors are provided corresponding to a plurality of observation points in the detection unit 30 and that the analysis signal generation unit 42 is included in the signal processing unit 40. . Below, the distance measuring method according to the present embodiment will be described in detail, and the effects brought about by the above differences will be clarified.

  First, the measurement principle of the distance measurement method according to the present embodiment will be described.

  In the distance measuring device shown in FIG. 1, the standing wave received power signal p (f, x) detected at a certain observation point x is similar to the received power signal equation (4) in the conventional distance measuring device.

It is represented by The received power signal p (f, x) obtained by modifying this equation (8) is

However,

It becomes.

  Here, assuming that the reference observation point is x = 0, the received power signal p (f, 0) at x = 0 is

It is. In the received power signal p (f, 0), an analysis signal pa (f, 0) obtained by calculating the amplitude change component m (f) and the phase change component θ (f) is

It is represented by

  Therefore, the profile P (x) of the received power signal p (f, 0) is obtained by performing Fourier transform on the analysis signal pa (f, 0) of the equation (11).

It becomes. Compared with the profile P (x) obtained by the conventional distance measuring device shown in the expression (6), the expression (12) is composed of a single term component and does not include a plural term component. . This is because the cos function in the equation (6 ⁾ is replaced with the complex sine wave function ^{ejθ (f)} by calculating the phase change component θ (f).

Here, as a method for deriving the complex sine wave function e ^{jθ (f)} from the cos function, the Hilbert transform is generally known. According to this, a complex sine wave function ^{ejθ (f)} is obtained by obtaining a sin function orthogonal to the cos function. However, in order to generate a complex sine wave function by the Hilbert transform, it is necessary that the basic cos function includes sufficient periodicity. Therefore, it can be said that the Hilbert transform is difficult to apply when the distance d is short and sufficient cosine function is not recognized as in the present embodiment.

On the other hand, in this embodiment, the complex sine wave function e ^{jθ (f)} is obtained by converting the received power signal p (f, 0) into an analysis signal pa (f, 0) whose components are known. To derive. According to this method, since it is not necessary for the cosine function to include periodicity, the profile P (x) can be obtained from Fourier transform even at a short distance where periodicity is not observed.

  Further, the profile magnitude | P (x) | obtained by Fourier transforming the analytic signal pa (f, 0) including the complex sine wave function is a single maximum value as is apparent from the equation (12). Have Thereby, the profile disturbance caused by the interference between the second term component and the third term component, which is seen in the region where the distance d in FIG. 16 is small, can be avoided, and the measurement error at a short distance can be reduced.

  Therefore, in the present embodiment, a plurality of observation points of the standing wave S are provided, and the amplitude change component m (f) and the phase change component θ (f) are obtained from the received power signal detected at each observation point. An analysis signal pa (f, 0) is generated and Fourier-transformed to realize a distance measurement method having no error even at a short distance.

Specifically, the received power signals p (f, x ₁ ) and p (f, x ₂ ) at two observation points x = x ₁ , x ₂ newly added to the reference observation point x = 0 are: Respectively,

It becomes. From the equations (11), (13), and (14), the phase change component θ (f) is

However,

  The amplitude change component m (f) is

Are calculated respectively.

Furthermore, the constant component A ² is not necessary directly for the construction of the analysis signal.

Is calculated by

  When the amplitude change component m (f) and the phase change component θ (f) are obtained by the equations (15) and (16), the analysis signal pa (f, 0) shown in the equation (11) is generated. The analysis signal pa (f, 0) is Fourier transformed to obtain a profile P (x) shown in Expression (12).

  FIG. 2 is a flowchart showing an operation for realizing the measurement principle described above in the distance measuring apparatus of FIG.

Referring to FIG. 2, first, prior to measurement, frequency conditions are set in frequency control unit 14 of FIG. Specifically, the center frequency f _{0 of the} electromagnetic wave emitted from the transmission unit 20, the transmission frequency range f _W , and the frequency step Δf to be swept are set (step S01).

When the frequency condition is set, the frequency control unit 14 sets f = f ₀ −f _W / 2 as the transmission frequency f at the start of the sweep. The frequency control unit 14 outputs a control signal for controlling the oscillation frequency of the VCO of the transmission unit 12 to the transmission frequency f (step S02).

The transmission unit 12 adjusts its own oscillation frequency to the transmission frequency f in accordance with the control signal from the frequency control unit 14, and outputs a signal having the transmission frequency f (step S03). The transmitter 20 emits an electromagnetic wave having the same frequency f as the output signal to the measurement object _Mk .

Next, the detection unit 30 detects the standing wave S generated by the traveling wave D of the transmission frequency f and the reflected wave R reflected by the measurement object. At this time, in the detection unit 30, the received power signals p (f, 0) and p (f (f) of the standing wave S are detected by detectors arranged at three observation points (x = 0, x ₁ , x ₂ ), respectively. , X ₁ ) and p (f, x ₂ ) are detected (step S04).

The detection operation shown in steps S03 and S04 is performed by increasing the transmission frequency f by the frequency step Δf (step S06). The series of operations described above is repeated until the transmission frequency f finally reaches the frequency f ₀ + f _W / 2 at the end of the sweep (step S05).

In step S05, when the detection of the received power signal in the predetermined frequency range f _W is completed, the analysis signal generating unit 42 in the signal processing unit 40 receives the received power signals p (f, 0), p (f, x ₁ ), P (f, x ₂ ), the analysis signal pa (f, 0) = m (f) e ^{jθ (f)} is calculated (step S07).

  The obtained analysis signal pa (f, 0) is subjected to Fourier transform in the Fourier transform unit 44. Thereby, the profile P (x) is derived (step S08).

  Finally, by extracting the maximum value of the profile P (x), the distance dk of the measurement object Mk can be obtained (step S09).

_{3, f 0 = 24.0375GHz, f W} = 75MHz, under the conditions of _{γ k = 0.1, φ k =} π, the distance _{d k} of the measuring object _{M k} of 0 m ≦ _{d k} ≦ 5 m of When the distance is changed in the range, the profile | P (x) | of the received power signal profile is obtained by numerical calculation in the distance measuring apparatus of FIG. Three observation points (0, x ₁ , x ₂ ) were set to (0, −2 mm, −5 mm), respectively, and a Hamming window was used as a window function at the time of Fourier transform.

As is clear from FIG. 3, the profile P (x) has a maximum value at the position of the period of the received power signal in the entire range where the distance d _k to the measurement object M _k satisfies 0 m ≦ d _k ≦ 5 m. It is a function.

FIG. 4 is a diagram showing the relationship between the distance d _k (measured value) of the measurement object M _k obtained from the profile P (x) shown in FIG. 3 and the distance to the actual measurement object.

As shown in FIG. 4, the distance d _k of the measurement object obtained from the profile P (x) and the distance to the actual measurement object have a one-to-one relationship in the entire range of 0 m ≦ d _k ≦ 5 m. Is obtained. As a result, it is possible to measure even in a region where the distance that is conventionally impossible to measure is 2 m or less, and in particular, it is possible to measure the distance from d = 0 m.

FIG. 5 is a diagram illustrating an extracted measurement result at a medium distance level (4.0 m ≦ d _k ≦ 5.0 m) in the distance d _k to the measurement object in the relationship illustrated in FIG. 4.

As shown in FIG. 5, the distance d _k of the measuring object M _k does not change as shown in the figure, and the error is very small. Therefore, the measurement error can be reduced even for the measurement object M _k located at a medium distance or more.

FIG. 6 shows a case where the measurement object is the first measurement object M _k , and the second measurement object M _{k + 1} fixed at the position of x = 10 m is added to the distance measurement device of FIG. It is a figure which shows the profile obtained.

  According to FIG. 6, it can be seen that the profile independently has local maxima corresponding to the first and second measurement objects, respectively.

7, the relationship between the distance to the first measurement object M _k distance d _{k (measured} value) and the actual first measuring object M _k obtained from profile P (x) shown in FIG. 6 FIG. Further, FIG. 8, and the distance to the object of measurement M _{k + 1} profile P (x) from the second measurement object M _{k + 1} obtained distance d _{k + 1 (measured} value) and the actual second shown in FIG. 6 It is a figure which shows a relationship.

  Referring to FIGS. 7 and 8, it can be seen that even when there are two measurement objects, each position is accurately measured without including an error component. Needless to say, it is possible to measure each object independently even with respect to two or more measurement objects.

  As described above, according to Embodiment 1 of the present invention, it is possible to realize a distance measuring apparatus capable of measuring a measurement object from a distance of 0 m with high measurement accuracy even in a limited transmission frequency bandwidth. .

[Embodiment 2]
In the previous embodiment, a distance measuring device capable of accurately measuring a distance from a distance of 0 m was proposed. According to the distance measuring device of the present invention, it is also possible to measure the distance of the moving measuring object, which has been regarded as a problem in the past, with high accuracy. In the present embodiment, distance measurement of a moving measurement object using the distance measurement device of the present invention will be described in detail.

  First, in the distance measuring device according to the present invention, the distance measurement of the moving measuring object is basically performed in the same procedure as that described in the conventional distance measuring device (see FIGS. 21 and 22).

Specifically, first, the sweep direction of the transmission frequency f is increased in the range of the frequency bandwidth f _W (corresponding to Δf> 0), and the profile P (x) is calculated from the obtained received power signal. The maximum value is extracted from the obtained profile, the distance is measured, and the first position information of the measuring object _Mk indicating the correlation between the measurement result and the moving speed is _obtained .

Next, the sweep direction of the transmission frequency f is lowered within the range of the frequency bandwidth f _W (corresponding to Δf <0), and the profile P (x) is calculated from the obtained reception power signal. The maximum value is extracted from the obtained profile P (x), the distance is measured, and the second position information of the measurement object M _k indicating the correlation between the measurement result and the moving speed is _obtained .

Finally, correction processing for averaging the obtained first position information and second position information is performed, and position information of the true measurement object _Mk is obtained.

  FIG. 9 is a circuit diagram showing a basic configuration of a distance measuring apparatus according to the second embodiment of the present invention.

  Referring to FIG. 9, the distance measurement device adds a correction processing unit 46 that performs correction processing of the first position information and the second position information to signal processing unit 40 of the distance measurement device of the first embodiment. It is a thing. Therefore, only the signal processing unit 40 will be described, and description of other common parts will not be repeated.

  The signal processing unit 40 is obtained from an analysis signal generation unit 42 that generates an analysis signal from the received power signal, a Fourier transform unit 44 that Fourier transforms the analysis signal to calculate a profile P (x), and a profile P (x). And a correction processing unit 46 that corrects the obtained position information and obtains true position information.

  The analysis signal generation unit 42 calculates the amplitude change component m (f) and the phase change component θ (f) from the received power signal obtained for each of the rising sweep and the falling sweep of the transmission frequency f, and the analysis signal pa (f, 0) is generated.

The Fourier transform unit 44 performs a Fourier transform on the obtained analysis signal to calculate a profile P (x). At the time of ascending sweep, the distance d _k that gives the maximum value of the profile P (x) is acquired as the first position information. Similarly, during the downward sweep, the distance d _k that gives the maximum value of the profile P (x) is acquired as the second position information.

The correction processing unit 46 performs a correction process that halves, that is, averages, the sum of the first position information and the second position information. The distance d _{k as the} processing result is acquired as the true position information of the measurement object M _k .

  Hereinafter, the relationship between the first and second position information and the true position information obtained from the information will be described based on the measurement results.

10 and 11 show the received power detected by the distance measuring device when the measuring object M _k located at the distance d _k = 5 m is moving at a moving body speed of 2.0 m / sec at a constant speed back and forth. It is a figure which shows the detection result of a signal. Note that the transmission frequency sweep time in the distance measuring device is 20 milliseconds.

Specifically, FIG. 10 shows a result obtained by numerical calculation of the magnitude | P (x) | of the received power signal profile of the measurement object M _k obtained when the transmission frequency f is swept down.

Referring to FIG. 10, during the downward sweep, the size of the profile is within a range in which the moving speed is negative (corresponding to approach of measurement object _Mk ) to positive (corresponding to separation of measurement object). P (x) | indicates a maximum value over a distance from positive to negative.

On the other hand, FIG. 11 shows the result of numerical calculation of the magnitude | P (x) | of the received power signal profile of the measurement object M _k obtained when the transmission frequency f is swept up.

  Referring to FIG. 11, during the upward sweep, the profile size | P (x) | shows the maximum value over the distance from negative to positive in the range where the moving speed is from negative to positive.

  FIG. 12 is a diagram showing the relationship between the distance (measured value) obtained from the profiles shown in FIGS. 10 and 11 and the moving speed of the measurement object.

  Referring to FIG. 12, the measurement result (corresponding to the solid line in the figure) at the time of the upward sweep reflects the profile of FIG. 11, and monotonously increases from negative to positive in the range where the moving speed is from negative to positive. The measurement result during the upward sweep is held as the first position information.

  On the other hand, the measurement result (corresponding to the dotted line in the figure) during the downward sweep reflects the profile of FIG. 10 and monotonously decreases from positive to negative within the range in which the moving speed is from negative to positive. The measurement result during the downward sweep is held as second position information.

  The measurement result obtained by the correction process for averaging the first and second position information accurately maintains the distance 5 m regardless of the moving speed of the measurement object, as indicated by the thick solid line in the figure. is doing.

  Comparing the above measurement results with the conventional measurement results shown in FIGS. 21 and 22, since the conventional distance measurement device cannot measure a negative distance, the measurement result is a waveform folded at 0 m. On the other hand, in the present embodiment, both the first and second position information maintain the linearity without being folded back even if the measurement result reaches a negative value. For this reason, the measurement result obtained by the correction process does not show an error even when the moving speed is high. Therefore, according to the present embodiment, it is possible to accurately measure the position of a moving measurement object without depending on the sweep time.

  FIG. 13 is a flowchart for explaining the measuring operation in the distance measuring apparatus shown in FIG.

Referring to FIG. 13, first, prior to measurement, frequency conditions are set in frequency control unit 14 of FIG. Specifically, the center frequency f _{0 of the} electromagnetic wave emitted from the transmitter 20, the transmission frequency range f _W , and the frequency step Δf to be swept are set (step S 10). In the following, the first and second position information are detected by increasing the transmission frequency f at each frequency step Δf (corresponding to upward sweep) or decreasing at every frequency step Δf (corresponding to downward sweep). Is done.

First, in the upward sweep, when the frequency condition is set, the frequency control unit 14 sets f = f ₀ −f _W / 2 as the transmission frequency f at the start of the sweep. The frequency control unit 14 outputs a control signal for controlling the oscillation frequency of the VCO of the transmission unit 12 to the transmission frequency f (step S11).

  The transmission unit 12 adjusts its own oscillation frequency to the transmission frequency f in accordance with the control signal from the frequency control unit 14, and outputs a signal having the transmission frequency f (step S12). The transmitter 20 emits an electromagnetic wave having the same frequency f as the output signal to the measurement object Mk.

Next, the detection unit 30 detects the standing wave S generated by the traveling wave D of the transmission frequency f and the reflected wave R reflected by the measurement object Mk. At this time, in the detection unit 30, the received power signals p (f, 0) and p (f (f) of the standing wave S are detected by detectors arranged at three observation points (x = 0, x ₁ , x ₂ ), respectively. , X ₁ ) and p (f, x ₂ ) are detected (step S13).

The detection operation shown in steps S12 and S13 is performed by increasing the transmission frequency f by the frequency step Δf (step S15). The series of operations described above are repeated until the transmission frequency f finally reaches the frequency f ₀ + f _W / 2 at the end of the sweep (step S14).

In step S14, the detection of the reception power signal of a predetermined frequency range _{f W} is completed, the analysis signal generating unit 42 in the signal processing unit 40, the received power signal p (f, 0), p (f, x 1 ), P (f, x ₂ ), the analysis signal pa (f, 0) = m (f) e ^{jθ (f)} is calculated (step S16).

  Further, the obtained analysis signal pa (f, 0) is subjected to Fourier transform in the Fourier transform unit 44. Thereby, the profile P (x) is derived (step S17).

Finally, by extracting the maximum value of the profile P (x), the distance d _k of the measuring object M _k can be obtained (step S18). The detected distance d _k is sent to the correction processing unit 46 as first position information.

Next, in the downward sweep, when the frequency condition is set, the frequency control unit 14 sets f = f ₀ + f _W / 2 as the transmission frequency f at the start of the sweep. The frequency control unit 14 outputs a control signal for controlling the oscillation frequency of the VCO of the transmission unit 12 to the transmission frequency f (step S21).

The transmission unit 12 adjusts its own oscillation frequency to the transmission frequency f in accordance with the control signal from the frequency control unit 14 and outputs a signal having the transmission frequency f. The transmitter 20 emits an electromagnetic wave having the same frequency f as the output signal to the measurement object _Mk (step S22).

Next, the detection unit 30 detects the standing wave S generated by the traveling wave D of the transmission frequency f and the reflected wave R reflected by the measurement object _Mk . At this time, in the detection unit 30, the received power signals p (f, 0) and p (f (f) of the standing wave S are detected by detectors arranged at three observation points (x = 0, x ₁ , x ₂ ), respectively. , X ₁ ) and p (f, x ₂ ) are detected (step S23).

The detection operation shown in steps S22 and S23 is performed by reducing the transmission frequency f by the frequency step Δf (step S25). The series of operations described above are repeated until the transmission frequency f finally reaches the frequency f ₀ −f _W / 2 at the end of the sweep (step S24).

In step S24, the detection of the reception power signal of a predetermined frequency range _{f W} is completed, the analysis signal generating unit 42 in the signal processing unit 40, the received power signal p (f, 0), p (f, x 1 ), P (f, x ₂ ), the analysis signal pa (f, 0) = m (f) e ^{jθ (f)} is calculated (step S26).

  The obtained analysis signal pa (f, 0) is subjected to Fourier transform in the Fourier transform unit 44. Thereby, the profile P (x) is derived (step S27).

Finally, by extracting the maximum value of the profile P (x), the distance d _k of the measurement object M _k can be obtained (step S28). The detected distance d _k is sent to the correction processing unit 46 as second position information.

When the first and second position information is sent in steps S18 and S28, the correction processing unit 46 averages these two position information (step S29). The obtained result is acquired as the true position information of the measuring object _Mk (step S30).

In the distance measuring apparatus according to the present embodiment, the observation point (0, x ₁ , x ₂ ) is a connection part from the transmission source 10 to the transmission part 20, that is, a coupling or connection on the printed wiring board. Although the coupling on the cable (coaxial cable) is shown, it can be detected in the same manner even if it is provided in the waveguide of the transmission unit 20 or between the measurement object M _{1 to} M _n from the transmission 20 unit. That is, in principle, measurement points can be provided at arbitrary positions.

Also, if known by the DC component is some means received power signal, for constant component A ² is known, it becomes possible to configure the number of observation points at two points, is possible to simplify the apparatus it can.

  As described above, according to the second embodiment of the present invention, even when the measurement object is moving at a high speed, the measurement result obtained by performing the upward sweep and the downward sweep on the transmission frequency is subjected to correction processing. The distance can be measured accurately without depending on the sweep time.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

It is a circuit diagram which shows the basic composition of the distance measuring device according to Embodiment 1 of this invention. It is a flowchart for demonstrating the measurement operation | movement in the distance measuring device of FIG. It is a figure which shows the result of having calculated | required the magnitude | size | P (x) | of the profile of the received power signal of the measuring object _Mk by numerical calculation. It is a figure which shows the relationship between the distance _dk (measurement value) of the measuring object _Mk calculated | required from the profile P (x) shown in FIG. 3, and the distance to an actual measuring object. Of the relationship shown in FIG. 4, the distance _{d k} to the object of measurement is a diagram showing by extracting the measurement result in the intermediate distance level _{(4.0m ≦ d k ≦ 5.0m)} . It is a figure which shows profile P (x) of the reception power signal of _1st measurement object _Mk and 2nd measurement object _{Mk + 1} . Is a diagram showing the relationship between the distance to the first measurement object M _k distance d _{k (measured} value) and the actual first measuring object M _k obtained from profile P (x) shown in FIG. 6 . It is a figure which shows the relationship between distance _{dk + 1} (measurement value) of 2nd measurement object _{Mk + 1} calculated | required from profile P (x) shown in FIG. 6, and the distance to actual 2nd measurement object _{Mk + 1} . . It is a circuit diagram which shows the basic composition of the distance measuring device according to Embodiment 2 of this invention. It is a figure which shows the result of having calculated | required the magnitude | size | P (x) | of the profile of the received power signal of the measuring object _Mk obtained at the time of upward sweep by numerical calculation. It is a figure which shows the result of having calculated | required the magnitude | size | P (x) | of the profile of the received power signal of the measuring object _Mk obtained at the time of a descending sweep by numerical calculation. It is a figure which shows the relationship between the distance (measurement value) obtained from the profile shown to FIG. 10 and FIG. 11, and the moving speed of a measuring object. It is a flowchart for demonstrating the measurement operation | movement in the distance measuring apparatus shown in FIG. It is a schematic block diagram which shows the structure of the distance measuring device proposed by patent document 3. FIG. FIG. 6 is a waveform diagram of a received power signal p (f, 0) observed at a position where x = x _s = 0 when a measurement object M _k is located at a distance d _k . Distance d _k is the profile size in the range from 0m to 5m of the measuring object M _k | is a diagram showing a calculation result | P (x). It is a figure which shows the relationship between the distance (measurement value) to the measuring object _Mk derived | led-out from the profile of FIG. 16, and the distance to the actual measuring object _Mk . It is a figure which shows the relationship between the measured value obtained from the profile when the distance to the measuring object _Mk is a middle distance level, and the distance to the actual measuring object _Mk . It is a figure which shows the measurement error when changing the position of the measuring object _Mk to a long distance level. It is a figure which shows the measurement result obtained by carrying out multiple processing of the received power signal. It is a figure which shows an example of a measurement result when the measuring object _Mk is moving on the x-axis at constant speed. It is a figure which shows an example of the measurement result when sweeping time is further shortened for the measurement of FIG.

Explanation of symbols

10, 60 transmission source, 12, 62 transmission unit, 14, 64 frequency control unit, 20, 70 transmission unit, 30, 80 detection unit, 40, 90 signal processing unit, 42 analysis signal generation unit, 44, 92 Fourier transform unit 46 Correction processing unit, M _{1 to} M _n measurement objects.

Claims (12)

A distance measuring device for measuring a distance to a measurement object,
A source for outputting a signal having a predetermined transmission frequency and a predetermined bandwidth;
A transmitter that generates an electromagnetic wave having the same frequency as the signal and radiates the electromagnetic wave to the measurement object;
A detection unit for detecting a power signal of a standing wave formed between the measurement object and the electromagnetic wave and a reflected wave of the electromagnetic wave;
A signal processing unit that calculates a distance to the measurement object by calculating a relationship between the detected power signal of the standing wave and the transmission frequency;
The detector is
A plurality of detection signals, each of which is arranged corresponding to each of a plurality of observation points provided on the detection axis with the traveling direction of the electromagnetic wave as a detection axis, and each detects a power signal of the standing wave at the corresponding observation point. Including detectors,
The signal processing unit
Analysis signal generating means for calculating a constant component, an amplitude change component and a phase change component from the plurality of standing wave power signals detected by the plurality of detectors, and generating an analysis signal;
The analysis signal into Fourier calculates the profile, and a Fourier transform means for obtaining a distance to the measurement object from the maximum value of the profile, the distance measuring device.   The distance measuring device according to claim 1, wherein the plurality of observation points are provided at arbitrary positions on the detection axis and between the transmission unit and the measurement object.   The distance measuring device according to claim 2, wherein at least one measurement object is provided. The source is
Ascending sweep means for sweeping up the predetermined transmission frequency by increasing the predetermined bandwidth in a predetermined step;
Down sweep means for sweeping down the predetermined transmission frequency in a predetermined step at a predetermined bandwidth;
The signal processing unit
The distance to the measurement object obtained by the Fourier transform means according to the ascending sweep means is the first position information, and the measurement object obtained by the Fourier transform means according to the descending sweep means Means for holding the distance as second position information;
The distance measuring apparatus according to claim 3, further comprising a correction unit that averages the held first and second position information to derive a true distance to the measurement object. A distance measurement method for measuring a distance to a measurement object,
Outputting a signal having a predetermined transmission frequency and a predetermined bandwidth;
Generating an electromagnetic wave having the same frequency as the signal and radiating the electromagnetic wave to the measurement object;
Detecting a standing wave power signal formed between the measurement object and the electromagnetic wave and the reflected wave of the electromagnetic wave;
Calculating a distance to the measurement object by calculating a relationship between the detected power signal of the standing wave and the transmission frequency, and
Detecting the standing wave power signal comprises:
In a plurality of detectors arranged corresponding to each of a plurality of observation points provided on the detection axis with the traveling direction of the electromagnetic wave as a detection axis, the power signal of the standing wave at the corresponding observation point Including the step of detecting
Calculating the distance to the measurement object,
Calculating a constant component, an amplitude change component, and a phase change component from the plurality of standing wave power signals detected by the plurality of detectors, and generating an analysis signal;
Calculating a profile the analysis signal into Fourier, and determining a distance to said object of measurement from the maximum value of the profile, the distance measurement method.   The distance measuring method according to claim 5, wherein the plurality of observation points are provided at arbitrary positions on the detection axis and between the transmission unit and the measurement object.   The distance measuring method according to claim 6, wherein the number of measurement objects is at least one. Outputting a signal having the predetermined transmission frequency and a predetermined bandwidth,
Sweeping up the predetermined transmission frequency in a predetermined step with the predetermined bandwidth; and
Sweeping down the predetermined transmission frequency in a predetermined step at a predetermined bandwidth; and
Calculating the distance to the measurement object,
The distance to the measurement object obtained by the Fourier transform when the upward sweep is performed is the first position information, and the distance to the measurement object obtained by the Fourier transform when the downward sweep is performed is the first position information. 2 as position information of 2;
The distance measurement method according to claim 7, further comprising: averaging the held first and second position information to derive a true distance to the measurement object. A distance measurement program for measuring the distance to a measurement object,
On the computer,
Outputting a signal having a predetermined transmission frequency and a predetermined bandwidth;
Generating an electromagnetic wave having the same frequency as the signal and radiating the electromagnetic wave to the measurement object;
Detecting a standing wave power signal formed between the measurement object and the electromagnetic wave and the reflected wave of the electromagnetic wave;
Calculating a distance to the measurement object by calculating a relationship between the detected power signal of the standing wave and the transmission frequency; and
Detecting the standing wave power signal comprises:
In a plurality of detectors arranged corresponding to each of a plurality of observation points provided on the detection axis with the traveling direction of the electromagnetic wave as a detection axis, the power signal of the standing wave at the corresponding observation point Including the step of detecting
Calculating the distance to the measurement object,
Calculating a constant component, an amplitude change component, and a phase change component from the plurality of standing wave power signals detected by the plurality of detectors, and generating an analysis signal;
The analysis signal into Fourier calculates the profile, and determining the distance from the maximum value of the profile up to the measurement target, a distance measuring program.   The distance measurement program according to claim 9, wherein the plurality of observation points are provided at arbitrary positions on the detection axis and between the transmission unit and the measurement object.   The distance measurement program according to claim 10, wherein the number of measurement objects is at least one. Outputting a signal having the predetermined transmission frequency and a predetermined bandwidth,
Sweeping up the predetermined transmission frequency in a predetermined step with the predetermined bandwidth; and
Causing the computer to execute a step of sweeping down the predetermined transmission frequency by a predetermined step with the predetermined bandwidth,
Calculating the distance to the measurement object,
The distance to the measurement object obtained by the Fourier transform when the upward sweep is performed is the first position information, and the distance to the measurement object obtained by the Fourier transform when the downward sweep is performed is the first position information. 2 as position information of 2;
The distance measurement program according to claim 11, further causing the computer to execute the step of averaging the held first and second position information and deriving a true distance to the measurement object.

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