JP2003240841A - Distance measuring equipment and distance measuring method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide distance measuring equipment manufacturable at a lower cost. <P>SOLUTION: In this distance measuring equipment, a first switch 14 is kept on for a VCO 13 to output its signals only when pulse signals outputted by a pulse generating circuit 11 are at the H level, the frequency is monotonically increased and then radiated from a transmission antenna 15 for reflection from an object of measurement, reflected waves arriving in a specified time period reckoned from radiation initiation are received while the pulse signals are at the H level, the received waves are mixed in a mixer 18 with signals being outputted by the VCO 13 for the synthesis of a beat, a rectifying circuit 20 outputs signals of a specified voltage while the beat is being outputted, the signals are integrated, and the distance to the object of measurement is determined based on the mean power of the integrated signals. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a distance measuring device and a distance measuring method which are mounted on a vehicle or the like and measure the distance between the vehicles.

[0002]

2. Description of the Related Art As an on-vehicle radar, a radar device has been developed for measuring the distance to an object near the vehicle. Conventionally, many of such radar devices employ a so-called pulse system. That is, by radiating a pulse signal of a predetermined frequency, receiving the reflected wave of the pulse signal reflected by the object, and multiplying the received reflected wave by the radiated pulse signal, the pulse signal and its reflection The propagation delay time with the wave is measured, and the distance to the object is measured based on the propagation delay time.

[0003]

However, the conventional radar device described above has the following problems. That is, for example, in the case of an on-vehicle radar, it is usual to narrow the pulse width of the transmission pulse in order to separate a plurality of objects existing around the vehicle. However, when the transmission pulse width is narrowed, the peak power of the transmission pulse is limited. The reduction of the peak power leads to the reduction of the effective transmission power, and as a result, the accuracy of detecting the object deteriorates. As a method for solving this problem, there is a radar device disclosed in Japanese Patent Laid-Open No. 2001-42029. However, according to the method described in the publication, a waveform shaping circuit for a high frequency signal is required, and it is difficult to obtain a waveform shaping circuit with high performance as the frequency in the microwave or millimeter wave band often used in radar increases. It becomes expensive.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a distance measuring device and a distance measuring method which can reduce the manufacturing cost.

[0005]

DISCLOSURE OF THE INVENTION The present invention for solving the above-mentioned problems of the prior art is, in a distance measuring device, a means for radiating a signal whose frequency monotonously increases or monotonically decreases with time, and the signal is measured. A means for receiving a reflected wave that is reflected by an object and arriving, and measuring a state of difference in frequency between the radiated signal and the reflected wave within a predetermined time from the start of radiation of the signal; It has a feature.

Further, here, a means for radiating a distant monitoring signal and a reflected wave that arrives after the distant monitoring signal is reflected by the object to be measured are received, and the object to be measured is utilized by using the reflected wave. And a means for calculating relationship information including at least a distance to

In these cases, it is also preferable to calculate the distance to the object to be measured based on the difference in frequency between the radiated signal and the reflected wave.

According to another aspect of the present invention, there is provided a distance measuring method, wherein a signal whose frequency monotonously increases or monotonically decreases with time is emitted, and the signal is reflected by an object to be measured and receives a reflected wave. However, it is characterized in that the state of difference in frequency between the radiated signal and the reflected wave is measured within a predetermined time from the start of radiation of the signal.

Here, it is also preferable to calculate the distance to the object to be measured based on the state of difference in frequency between the radiated signal and the reflected wave.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION [First Embodiment] The first embodiment of the present invention
Embodiments will be described with reference to the drawings. The distance measuring device according to the present embodiment, as shown in FIG.
Pulse generation circuit 11, control voltage generation circuit 12, VC
O13, the first switch 14, the transmitting antenna 15,
The receiving antenna 16, the second switch 17, and the mixer 18
, Bandpass filter (BPF) 19, and shaping circuit 2
0 and the distance detection circuit 21 are included.

As shown in FIG. 2A, the pulse generation circuit 11 periodically generates a pulse signal which is in the "H" state and which is in the "L" state after a lapse of a certain time, and outputs the pulse signal. The control voltage generation circuit 12 outputs a voltage signal that monotonically increases (or monotonically decreases) from when the pulse signal output from the pulse generation circuit 11 is in the “H” state to the “L” state. The VCO 13 outputs a signal having a frequency corresponding to the voltage signal input from the control voltage generation circuit 12. Therefore, as shown in FIG. 2B, the VCO 13 has a frequency f1 from when the pulse signal output from the pulse generating circuit 11 is in the "H" state to when it is in the "L" state.
A signal having a frequency that monotonically increases (or monotonically decreases) from to f2 is output.

The first switch 14 is a pulse generating circuit 11
While the pulse signal output by is in the "H" state, it is on, and while it is in the "L" state, it is off. Transmitting antenna 1
5 is connected to the VCO 13 via the first switch 14, and the VCO 13 is connected while the first switch 14 is on.
Emit the signal input from.

The radiated signal is reflected by the object to be measured and arrives at the receiving antenna 16 with a delay time corresponding to the distance (path length) to the object to be measured. The arriving signal (reflected wave) is, as shown in FIG.
The signal becomes a signal having a frequency that monotonically increases (or monotonically decreases) after being delayed by the delay time τ with respect to the signal output from 13. The receiving antenna 16 receives and outputs this signal. The second switch 17 is turned on while the pulse signal output from the pulse generation circuit 11 is in the “H” state,
The signal output from the receiving antenna 16 is output to the mixer 18. The mixer 18 outputs the signal output from the VCO 13 and the second
The signal output from the receiving antenna 16 is combined via the switch 17 and output.

Therefore, the signal output from the mixer 18 is VC
This is a signal obtained by synthesizing the signal currently output by O13 (FIG. 2B) and the signal currently received by the receiving antenna 16 (FIG. 2C). The low-frequency signal has a frequency corresponding to the difference (beat frequency). The BPF 19 selectively extracts, from the signal output from the mixer 18, a band including the difference between the peaks of the frequencies output by the VCO 13 and the frequency corresponding to the absolute value of f2f1.
Note that this bandwidth is wider than the absolute value of the difference of f2f1 in consideration that the frequency of the combined signal may be larger than the absolute value of the difference of f2f1 due to the Doppler effect. Is preferred. In addition, the DC component due to the sneak signal from the transmitting antenna 15 is generated by the mixer 18.
However, since this DC component (a signal whose frequency is “0”) is not necessary for calculating the distance, it is preferable to set it in a frequency band capable of cutting the DC component.

The shaping circuit 20, as shown in FIG. 2 (d), is during the period when the BPF 19 is outputting a signal (while the beat signal is being obtained by the mixer 18) and when the signal is not being output. Output signals with different voltages. The distance detection circuit 21 time-integrates the voltage signal output from the shaping circuit 20, and outputs the result as an average power. This average power is related to the delay time τ and increases as the delay time decreases. Therefore, based on this average power, the delay time τ
Can be calculated, and the distance from the delay time τ to the measurement object can be calculated.

The distance measuring device according to the present embodiment has the above-mentioned configuration, and outputs a high frequency signal whose frequency changes in a predetermined manner with time from the VCO 13, and the high frequency signal is predetermined by the first switch 14. Emit only within the set time of. This high frequency signal is reflected by the object to be measured and arrives at the receiving antenna 16 as a reflected wave. This reflected wave is taken in by the second switch 17 only within a predetermined time, and the taken-in signal is output by the mixer 18 to the current VC.
It is combined with the signal output by O13. The frequency of the signal output from the VCO 13 changes over time, so that the combined signal is in a frequency difference state (frequency difference in this case) between the delay times from transmission to reception. It becomes a beat signal of the corresponding frequency. Shaping circuit 2
0 outputs a voltage signal that takes a constant voltage while the beat signal is being output, and the distance to the measurement object is calculated based on the average power obtained by time integration of this voltage signal.

Since the low-frequency signal obtained by the synthesis of the mixer 18 is processed to measure the distance to the object to be measured in this way, expensive high-frequency parts are not required and the manufacturing cost can be reduced. Further, by limiting the transmission / reception time with the switches 14 and 17, it is possible to accurately detect only the target object within the target distance range even when there are a plurality of measurement target objects in the vicinity. Furthermore, while the low-frequency signal obtained by combining by the shaping circuit 19 is output, a signal of a constant voltage is output regardless of the frequency, and the distance is determined by the average power of the voltage signal within a predetermined time. The distance can be measured with a simple circuit for calculation, and the manufacturing cost can be further reduced.

In the present embodiment, since the measurement is performed by the frequency difference, when there are two or more vehicles as the measurement object, for example, the reflections reflected by the two or more vehicles respectively arrive. The waves are mixed and received. In this case, a signal corresponding to the frequency difference between the two or more reflected waves is generated, and the detection accuracy of the frequency difference is reduced. Therefore, the second switch 17 outputs only the signal within a predetermined time to the mixer 18, and ignores the signal coming from a relatively distant (that is, a large delay time) signal. By adjusting the timing at which the second switch 17 is turned off, only the reflected wave from only the measurement object closest to the mixer 18 is output to the mixer 18, and the detection accuracy is improved.

Although an example in which the first switch 14 and the second switch 17 are configured to be turned on / off in synchronization has been described here, they do not need to be synchronized, and for example, the second switch may be used.
The first switch 14 may be turned on / off after a delay of a predetermined time from the turning on / off of the switch 17. Similarly, here, the start timing of the change in the frequency of the signal output from the VCO 13 is also synchronized with the ON state of the first switch 14 by the pulse generation circuit 11, but these need not necessarily be synchronized. You can be late.

Further, in the above description, the first switch 14 outputs the output of the VCO 13 to the mixer 1 as shown in FIG.
It is arranged immediately before the transmitting antenna 15 after being branched to 8. That is, the structure shown in FIG. 3 (a) is partially extracted, but instead of FIG.
As shown in (b), the first switch 14 may be arranged immediately after the output of the VCO 13 and before being branched to the mixer 18. In this case, the mixer 18 is the VCO 13
The second switch 17 is not always necessary if the configuration is such that no signal is output unless there is an input from. Furthermore, the VCO 13 itself turns ON / OFF the signal output.
If it is possible to perform FF, the first switch 14
Is unnecessary.

Further, although the transmission antenna 15 and the reception antenna 16 are shown separately here, one antenna may serve as both the transmission antenna 15 and the reception antenna 16 by using a circulator.

[Second Embodiment] In the first embodiment, the amount related to the delay time τ (that is, the amount related to the distance to the object to be measured) is measured using the average power. However, since the delay time from the start of signal emission to the reception of the reflected wave may be directly measured, the distance measurement according to the second embodiment in which the delay time is directly measured next is performed. The device will be described.

As shown in FIG. 4, the distance measuring device of this embodiment has a pulse generating circuit 11 and a control voltage generating circuit 1.
2, the VCO 13, the first switch 14, the transmitting antenna 15, the receiving antenna 16, the mixer 18, and the BPF.
19 and a distance detection circuit 31.
It should be noted that parts having the same configurations as those according to the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

The distance detection circuit 31 according to this embodiment is
It has a timer (not shown), and after the pulse signal output from the pulse generation circuit 11 is in the “H” state, the BPF 19
Detects the time until the signal starts to be output as the delay time τ, and calculates the distance to the measurement object based on this delay time τ.

Also in this embodiment, the start timing of the change in the frequency of the signal output from the VCO 13 is synchronized with the ON state of the first switch 14 by the pulse generation circuit 11, but these are synchronized. You don't have to be. Further, although the transmitting antenna 15 and the receiving antenna 16 are shown separately here, one antenna may serve as both the transmitting antenna 15 and the receiving antenna 16 by using a circulator.

The first switch 14 is provided from the following point of view in order to clarify the signal output start point. That is, generally, the VCO 13 does not perform stable output immediately after the voltage signal is input from the control voltage generation circuit 12. Therefore, after the stable output is obtained, the first switch 14 is provided from the viewpoint of clarifying the output start time of the signal and sharpening the rising edge of the signal output from the BPF 19. Of. Therefore, the first switch 14 is not necessarily required if the VCO 13 can immediately output a stable signal when the control voltage is supplied.

[Third Embodiment] Furthermore, the average power,
Since the distance to the measurement object can be measured not only by measuring the delay time but also by using the frequency counter to measure the frequency difference, hereinafter, the distance to the measurement object is measured using the frequency difference. A distance measuring device according to the embodiment will be described.

The distance measuring device according to this embodiment is shown in FIG.
As shown in FIG. 3, the pulse generation circuit 11, the control voltage generation circuit 12, the VCO 13, the first switch 14, the transmission antenna 15, the reception antenna 16, and the second switch 17 are included.
And a mixer 18, a BPF 19, and a distance detection circuit 41. It should be noted that parts having the same configurations as those according to the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

The distance detection circuit 41 is a frequency counter, detects the frequency of the signal output from the BPF 19, and calculates the distance to the object to be measured based on the frequency.
That is, since the frequency of the radiated signal monotonically increases with time, the difference between the frequency of the signal output by the VCO 13 at a certain time and the frequency of the reflected wave received at that time is: The larger the delay time, the larger the delay time. In other words, since the frequency difference between these signals changes according to the delay time, the distance to the measurement object can be detected by the frequency difference.

[Modification] In the distance measuring devices according to the first to third embodiments, the voltage signal output by the control voltage generating circuit 12 has a voltage that monotonically increases or decreases with time. However, it is also possible to use a triangular-wave voltage signal that is a combination of monotonous increase and monotonic decrease.

Further, the transmitting antenna 15 and the receiving antenna 16 are configured to include a plurality of antenna elements, and each antenna element has a switch for turning on / off the radiation (or reception) of the signal at each antenna element. In the case of the array antenna provided, these switches may be used as the first switch 14 and the second switch 17. That is, the switch for each antenna element in the array antenna may be controlled based on the pulse signal output from the pulse generation circuit 11. According to this, the first switch 1
4 and the second switch 17 do not need to be separately provided, and the manufacturing cost can be further reduced.

[Fourth Embodiment] Furthermore, these first
-Since the distance measuring device according to the third embodiment may be combined with a device for measuring a distance to a measurement object that is relatively far away, the fourth embodiment of the present invention will be described below.
A distance measuring device according to the embodiment will be described. Note that, here, a case will be specifically described where the distance measuring device according to the first embodiment is combined with a device that measures a distance to a measurement object that is relatively far away.

The distance measuring device according to this embodiment is shown in FIG.
As shown in FIG. 3, the pulse generation circuit 11, the control voltage generation circuit 12, the VCO 13, the first switch 14, the transmission antenna 15, the reception antenna 16, and the second switch 17 are included.
, Mixer 18, changeover switch 51, and BPF 19
, Shaping circuit 20, distance detection circuit 52, FMCW
The signal processing circuit 53 for (FM Continuous Wave), the object detection circuit 54, and the mode switching signal generation circuit 55 are included. It should be noted that parts having the same configurations as those in the first embodiment are designated by the same reference numerals, and detailed description thereof will be omitted.

In the present embodiment, based on a predetermined condition, the mode switching signal output from the mode switching signal generation circuit 55 adjusts the distance to the object to be measured, and at least the remote monitoring having different properties is performed. Signal and proximity monitoring signal (VCO in the first to third embodiments)
, Which is a signal output by 13) is selected. Here, for simplicity,
A case where either one of the two signals, that is, the distant monitoring signal and the proximity monitoring signal is selected will be described.

In the present embodiment, the pulse generating circuit 11 receives the mode switching signal from the mode switching signal generating circuit 55, and the mode switching signal (mode switching signal for outputting the distance monitoring signal). In the case of the remote monitoring mode signal), the "H" level signal is always output. Further, the mode switching signal is a mode switching signal for outputting the proximity monitoring signal (proximity monitoring mode signal).
If so, the same operation as in the first to third embodiments is performed.

The control voltage generating circuit 12 receives a mode switching signal from the mode switching signal generating circuit 55 and outputs a voltage signal corresponding to either the distant monitoring signal or the proximity monitoring signal based on the mode switching signal. Output. Specifically, when the control voltage generating circuit 12 receives the remote monitoring mode signal, the control voltage generating circuit 12 outputs a triangular wave-shaped voltage signal having a relatively long period as shown in FIG. 7A. Further, when the control voltage generating circuit 12 receives the proximity monitoring mode signal, it outputs the same signal as in the first to third embodiments, as shown in FIG. 7B.

Therefore, while the mode switching signal generating circuit 55 is outputting the distance monitoring mode signal, the VCO 13 is
A signal (distance monitoring signal) that repeats a frequency rising section (up phase) and a frequency falling section (down phase) in a relatively long cycle is output. Further, while the proximity monitoring mode signal is being output, like the signals according to the first to third embodiments, the frequency monotonically increases or decreases monotonically in a shorter cycle, or like the distance monitoring radar, the monotonous The signal that repeats the increase and the monotonic decrease is output.

The change-over switch 51 receives the input of the mode change-over signal from the mode change-over signal generating circuit 55 and the input of the signal output from the mixer 18, and outputs the signal input from the mixer 18 to the BPF 19 and the FMCW. The signal is selectively output to one of the signal processing circuits 53 based on the mode switching signal. That is, if the mode switching signal is the distant monitoring mode signal, the signal input from the mixer 18 is output to the FMCW signal processing circuit 53, and if the input mode switching signal is the proximity monitoring mode signal,
The signal output from the mixer 18 is output to the BPF 19. The distance detection circuit 52 performs the same processing as the distance detection circuit 21 according to the first embodiment, and outputs information regarding the detected distance to the object detection circuit 54.

The FMCW signal processing circuit 53 is an FFT.
(Fast Fourier Transform) and other widely known FMCW radar processing (for example, Japanese Patent Laid-Open No. 2001-91639).
The processing described in “FMCW radar device” or the like) detects the distance to the measurement object, the speed of the measurement object, the azimuth in which the measurement object exists, etc., and outputs it to the object detection circuit 54. The object detection circuit 54 receives the information on the distance from the distance detection circuit 51 to the object to be measured, executes a predetermined process based on the information, and sends the information about the distance detection result to the mode switching signal generation circuit 55. Output. Further, the object detection circuit 54 receives the information about the distance and azimuth from the FMCW signal processing circuit 53 to the measurement object and the relative speed with respect to the measurement object and performs a predetermined process, and at the same time, performs the measurement. Information on the distance to the object is output to the mode switching signal generation circuit 55. Here, the predetermined processing is to recognize the target object by using both the information input from the FMCW signal processing circuit 53 and the information input from the distance detection circuit 51 (for each measurement target object). Widely known processes such as processes for recognizing distance, relative speed, direction, etc., and processes for warning of collision are included.

A characteristic feature here is that either the distant monitoring signal or the proximity monitoring signal is detected by the mode switching signal generation circuit 55 based on the information on the distance to the measurement object input from the object detection circuit 54. Is output, and a mode switching signal corresponding to the determination is output. Specifically, this mode switching signal generation circuit 55
The processing performed by will be described with reference to FIG. In the following description, the mode switching signal generation circuit 55
Is equipped with a timer (not shown).

The mode switching signal generation circuit 55 initializes a timer when the power is turned on (S1), and initially outputs a remote monitoring mode signal (S2). Then, receiving information about the distance to the measurement object, which is input from the object detection circuit 54, whether or not the measurement object is within a preset distance (measurement object within a predetermined vicinity area) (S3), if there is no (N)
If it is o), it is determined whether or not the time measured by the timer has passed a predetermined time set in advance (S4),
If the predetermined time has not passed (if No), the process S
Return to 3 and continue processing.

Further, in the process S3, when the object to be measured is included in the predetermined vicinity area (Yes),
Alternatively, in the process S4, if the time measured by the timer has exceeded the preset predetermined time (Yes), the proximity monitoring mode signal is output (S5). Then, the mode switching signal generation circuit 55 determines whether or not the measurement object is included in the predetermined vicinity area (S6). If the measurement object is included (Yes), the process returns to the process S6 to repeat the process.
The neighborhood area in process S3 and the neighborhood area in process S6 do not necessarily have to be in the same distance range.

During this time, the object detection circuit 54 detects that the object to be measured is in the vicinity. For example, in the case of a distance measuring device mounted on a vehicle, the possibility of collision is referred to by the previous measurement result or the like. However, if it is determined that the possibility of collision is high, processing such as issuing an alarm is performed.

On the other hand, in the process S6, when the mode switching signal generating circuit 55 determines that the measurement object does not enter the predetermined vicinity area (if No), the process returns to the process S1 to continue the process. Further, although it is assumed here that either the distant monitoring mode or the near field monitoring mode is selected, if there are three or more modes, a plurality of distance threshold values to be determined in step S3 may be provided.

That is, according to the present embodiment, for example, in the case of a vehicle-mounted distance measuring device, the FMCW signal as a distance monitoring signal is processed in a normal state, and the FMCW signal is processed within a predetermined neighborhood area set in advance. When another vehicle as a measurement target comes in, a simple measurement process is performed by the distance detection circuit 51 using the average power. That is, in the present embodiment, not only distance but also information such as relative speed and azimuth is acquired by the distant monitoring signal, and it is possible to separately acquire these pieces of information for a plurality of measurement objects.
While processing such as FMCW signal processing is performed in a long cycle, for proximity monitoring signals, the sweep cycle of the transmission signal is shortened and only the distance is measured. By performing simple processing, the time required for one measurement is shortened, the measurement cycle is shortened, and when there is an object to be measured in the vicinity, accurate measurement can be performed by performing more measurements. I am able to do it.

Further, if the frequency width extracted by the BPF 19 is narrowed, the measurement object can be narrowed down only to the measurement object closer to it. For example, by narrowing down the measurement object to only one, the measurement accuracy is further improved. it can. Further, in the present embodiment, in consideration of the interruption immediately before the own vehicle, even if the other vehicle is not in the predetermined vicinity area, the processing using the proximity monitoring signal is performed at a predetermined timing, for example, periodically. .

In the above description, the FMC
Although the case where the distance measuring method of the W method is used has been described as an example, the same can be realized by using the distance measuring method of the pulse Doppler method.

Further, here, the case where the distance measuring device according to the first embodiment is combined with the device for distance monitoring has been described as an example, but the distance measuring device may be combined with the second and third embodiments. . In that case, the shaping circuit 20 is omitted, and the distance detection circuit 52 replaces the operation (detection by average power) of the distance detection circuit 21 of the first embodiment with the second and third embodiments. The distance detection circuits 31 and 41 (detection by the delay time and the frequency counter) may be operated.

[0049]

According to the present invention, a signal of a predetermined frequency is radiated intermittently, the signal is reflected by an object to be measured, a reflected wave that arrives is received, and a predetermined wave is received only while the reflected wave is received. Of the voltage signal is output, the average power of the voltage signal is calculated within a predetermined time from the start of signal emission, and the distance measuring device calculates the distance to the measurement object based on the magnitude of this average power. Since the distance is measured by the average power without performing high frequency processing, the manufacturing cost can be reduced.

[Brief description of drawings]

FIG. 1 is a configuration block diagram of a distance measuring device according to a first embodiment of the present invention.

FIG. 2 is a timing chart diagram illustrating an example of a state of a signal output by each unit of the distance measuring device according to the first embodiment of the present invention.

FIG. 3 is an explanatory diagram illustrating a modified example of the distance measuring device according to the first embodiment of the present invention.

FIG. 4 is a configuration block diagram of a distance measuring device according to a second embodiment of the present invention.

FIG. 5 is a configuration block diagram of a distance measuring device according to a third embodiment of the present invention.

FIG. 6 is a configuration block diagram of a distance measuring device according to a fourth embodiment of the present invention.

FIG. 7 is an explanatory diagram illustrating an example of a distance monitoring signal and a near signal.

FIG. 8 is a flowchart showing an example of processing of a mode switching signal generation circuit of a distance measuring device according to a fourth embodiment of the present invention.

[Explanation of symbols]

11 pulse generation circuit, 12 control voltage generation circuit, 13
VCO, 14 first switch, 15 transmitting antenna,
16 receiving antenna, 17 2nd switch, 18 mixer, 19 BPF, 20 shaping circuit 21, 31, 4
1,52 Distance detection circuit, 51 Changeover switch, 53
FMCW signal processing circuit, 54 object detection circuit, 55
Mode switching signal generation circuit.

Claims (5)

[Claims] 1. A means for radiating a signal whose frequency monotonously increases or monotonically decreases with time, and a reflected wave which arrives after the signal is reflected by an object to be measured, and a predetermined period is set from the time when the radiation of the signal is started. Means for measuring the difference in frequency between the radiated signal and the reflected wave in time, and a distance measuring device. 2. The distance measuring device according to claim 1, wherein the means for radiating a distant monitoring signal and a reflected wave that arrives after the distant monitoring signal is reflected by an object to be measured, A means for calculating relational information including at least a distance to a measurement object using a reflected wave, and a distance measuring device. 3. The distance measuring device according to claim 1, wherein the distance to the object to be measured is calculated based on a state of difference in frequency between the radiated signal and the reflected wave. measuring device. 4. A signal whose frequency monotonously increases or monotonically decreases with time is radiated, and a reflected wave arriving when the signal is reflected by an object to be measured is received, and within a predetermined time from the time when the radiation of the signal is started. (3) A distance measuring method characterized by measuring a difference state of frequencies between the radiated signal and the reflected wave. 5. The distance measuring method according to claim 4,
A distance measuring method, comprising calculating a distance to the object to be measured based on a difference in frequency between the radiated signal and the reflected wave.