JP2000111638A - Radar system, object detecting method and record medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect an object even when a time change in an external factor is large and an attenuation quantity of an electromagnetic wave on the basis of it is large. SOLUTION: Radar devices 11, 12 transmit electromagnetic wave pulses of the same frequency of a millimeter wave band in the same output. An amplitude comparator 3 compares receiving levels of the electromagnetic wave pulses received by the radar devices 11, 12. Pulse detectors 13, 14 compare phases of the electromagnetic wave pulses transmitted/received by the radar devices 11, 12. A signal processor 15 judges that there is an object between the radar devices 11, 12 when judged that there is a difference between the receiving levels by the amplitude comparator 3, and judges that there is an object between the radar devices 11, 12 when judged that there is a difference between phases of the electromagnetic wave pulses transmitted/received by the pulse detectors 13, 14 even when judged that there is no difference between the receiving levels by the amplitude comparator 3. The signal processor 15 supplies a detecting result to an output unit 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radar device, an object detection method, and a recording medium, and more particularly, to transmitting and receiving electromagnetic waves with a set of radar devices and comparing received electromagnetic waves with one set of radar devices. The present invention relates to a radar device, an object detection method, and a recording medium that can detect an object existing between devices.

[0002]

2. Description of the Related Art Conventionally, as a method for detecting whether or not an object exists on a predetermined straight line, a method using a pair of opposed measuring devices is well known. However, this method may erroneously detect an object due to external factors such as rain, fog, snow, and dust.

[0003] The applicant of the present invention has disclosed in Japanese Patent Application Laid-Open No. 7-221623 a method of detecting an object by using a set of opposing measuring devices, setting a threshold value for the reception level of the measuring devices by a predetermined method. Proposed earlier.

[0004]

However, in the method proposed above, when the temporal change due to external factors such as rain, fog, snow, and dust is small, and the attenuation of electromagnetic waves due to such factors is small, Although there is not much problem, there is a possibility that an object may be erroneously detected when external factors have a large temporal change and the amount of electromagnetic wave attenuation based on them is large.

The present invention has been made in view of such a situation, and it is an object of the present invention to accurately detect an object even when an external factor has a large temporal change and an attenuation amount based on the external factor is large. .

[0006]

According to a first aspect of the present invention, there is provided a radar system comprising: first transmitting / receiving means for transmitting / receiving electromagnetic waves;
A second transmitting / receiving means for transmitting / receiving electromagnetic waves, a comparing means for comparing the electromagnetic waves received by the first transmitting / receiving means and the second transmitting / receiving means, and the second transmitting / receiving means based on a result compared by the comparing means. It is characterized by comprising a detecting means for detecting an object existing between the first transmitting / receiving means and the second transmitting / receiving means.

According to a seventh aspect of the present invention, in the method for detecting an object of a radar apparatus comprising a first transmitting / receiving device and a second transmitting / receiving device for transmitting / receiving an electromagnetic wave.
A first transmitting / receiving step of transmitting / receiving electromagnetic waves by the transmitting / receiving device, a second transmitting / receiving step of transmitting / receiving electromagnetic waves by the second transmitting / receiving device, and the first transmitting / receiving step and the second transmitting / receiving step. A comparing step of comparing electromagnetic waves, and the first transmitting / receiving apparatus and the second transmitting / receiving apparatus based on a result of the comparison in the comparing step.
Detecting an object existing between the transmitting and receiving devices.

A first transmitting / receiving step of transmitting / receiving an electromagnetic wave by the first transmitting / receiving apparatus to / from a radar apparatus comprising a first transmitting / receiving apparatus and a second transmitting / receiving apparatus for transmitting / receiving electromagnetic waves. And a second transmitting / receiving step of transmitting / receiving electromagnetic waves by the second transmitting / receiving device; a comparing step of comparing the electromagnetic waves received in the first transmitting / receiving step and the second transmitting / receiving step; A computer-readable program for executing a process including a detection step of detecting an object existing between the first transmission / reception device and the second transmission / reception device based on the performed result is recorded. It is characterized by.

In the radar system according to the first aspect, an object existing between the first and second transmitting / receiving units is detected based on a comparison result of the electromagnetic waves received by the first and second transmitting / receiving units. Is done.

[0010] In the object detection method according to the seventh aspect and the recording medium according to the eighth aspect, the first and the second transmission / reception devices are provided based on a comparison result of the electromagnetic waves received by the first and second transmission / reception devices. An object existing between the transmitting and receiving devices is detected.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The embodiments of the present invention will be described below. In order to clarify the correspondence between each means of the invention described in the claims and the following embodiments, The features of the present invention are described as follows by adding the corresponding embodiment (however, an example) in parentheses after each means. However, of course, this description does not mean that each means is limited to those described.

A radar system according to a first aspect of the present invention includes a first transmitting / receiving means for transmitting / receiving electromagnetic waves (for example, the radar apparatus 1 in FIG. 1) and a second transmitting / receiving means for transmitting / receiving electromagnetic waves (for example, the radar in FIG. 1). The apparatus 2) is compared with an electromagnetic wave received by the first transmission / reception means and the second transmission / reception means (for example, the amplitude comparator 3 in FIG. 1), and based on a result compared by the comparison means. , Detecting means for detecting an object existing between the first transmitting / receiving means and the second receiving means (for example, the output unit 4 in FIG. 1).

FIG. 1 is a block diagram showing a configuration example of a radar system to which the present invention is applied. The radar apparatus 1 and the radar apparatus 2 are installed facing each other, and transmit electromagnetic waves of the same frequency in the millimeter wave band with the same output. The radar apparatus 1 and the radar apparatus 2 are arranged such that the direction of the electromagnetic field having the maximum intensity of the transmitted electromagnetic wave is directed to the radar apparatus 2 and the radar apparatus 1, respectively.

The amplitude comparator 3 compares the amplitudes of the respective electromagnetic waves received by the radar device 1 and the radar device 2 and outputs the comparison result to the output device 4. Output unit 4 is LC
D, a speaker, a display device, and the like, and detects the presence or absence of an object existing between the radar device 1 and the radar device 2.

Next, the operation of the radar system of FIG. 1 will be described with reference to the flowchart of FIG. In step S1, the radar device 1 and the radar device 2 each sense an object. That is, the radar apparatus 1 and the radar apparatus 2 transmit electromagnetic waves having the same frequency in the millimeter wave band with the same output. Therefore, the radar device 1 receives the electromagnetic wave transmitted by the radar device 1, and the radar device 2 receives the electromagnetic wave transmitted by the radar device 1. Each of the radar devices 1 and 2 detects the reception level (amplitude) of the received electromagnetic wave, and supplies the detection result to the amplitude comparator 3.

In step S2, the amplitude comparator 3
The amplitudes (hereinafter, also referred to as reception levels) of the electromagnetic waves received by the radar devices 1 and 2 are compared.

In step S2, the amplitude comparator 3
It is determined whether there is a difference between the reception levels of the compared electromagnetic waves. If the amplitude comparator 3 determines in step S2 that there is no difference between the reception levels, the process returns to step S1, and
The sensing process is repeated until a difference occurs in the reception level.

When there is no object between the radar apparatus 1 and the radar apparatus 2, since the radar apparatus 1 and the radar apparatus 2 transmit electromagnetic waves of the same frequency and the same output, the radar apparatus 1 and the radar apparatus 2 Receive the same level of electromagnetic waves.

For example, the distance between the radar device 1 and the radar device 2 is 10 m, the output of the electromagnetic wave transmitted from the radar device 1 and the radar device 2 is 10 dBm, and the attenuation factor (propagation) due to external factors such as molecules existing in the atmosphere. Loss) 0.1 dB / m
As a result, the reception level of the electromagnetic waves transmitted from the radar device 2 and the radar device 1 in the radar device 1 and the radar device 2 is 9 dB.

The reception levels of electromagnetic waves received by the radar device 1 and the radar device 2 when an object exists between the radar device 1 and the radar device 2 will be described with reference to FIG. The horizontal axis in FIG. 3 indicates the distance of the object from the radar device 1, and the vertical axis indicates the radar device 1 and the radar device 2.
Indicates the reception level of the received electromagnetic wave. In FIG. 3, it is assumed that the object has no size, the reflection loss of the electromagnetic wave by the object is 3 dB, and all the reflected electromagnetic waves are received by the radar device 1 or the radar device 2.

Under such an assumption, the radar device 1
The reception level of the electromagnetic wave received by the following is as follows. That is, when the object is located at a position 0 m from the radar device 1 (virtually the position of the radar device 1), the reflection level of the electromagnetic wave received by the radar device 1 is 3 dB because the reflection loss of the electromagnetic wave by the object is 3 dB. 7 dB. Then, as the position of the object gradually moves away from the radar device 1, the reception level attenuates at an attenuation rate of 0.1 dB / m, and the object moves to the midpoint between the radar device 1 and the radar device 2, that is, the radar device. When the distance from 1 is at a position of 5 m, the electromagnetic wave propagates a distance of 10 m in a round trip, so that the reception level is 6 dB. Further, as the distance from the radar device 1 to the object increases, the reception level decreases by 0.1 dB.
When the object is located at a position 10 m from the radar device 1 (virtually the position of the radar device 2), the propagation distance of the electromagnetic wave is 20 m in a round trip, and the reception level of the electromagnetic wave is 5 dB. .

Similarly, the reception level of the electromagnetic wave received by the radar device 2 is as follows. That is, when the object is located at a position 0 m from the radar device 2 (virtually the position of the radar device 2 and 10 m from the radar device 1), the reflection loss of the object is 3 dB, so that the object is received by the radar device 2. The reception level of the electromagnetic wave becomes 7 dB. Then, as the position of the object gradually moves away from the radar device 2 (approaching gradually to the radar device 1), the reception level is attenuated at an attenuation rate of 0.1 dB / m, and the object moves between the radar device 2 and the radar device 1. When the intermediate point between the radar apparatuses is located at a distance of 5 m from the radar apparatus 2 (radar apparatus 1), the reception level is 6 dB. Further, as the distance from the radar apparatus 2 increases (the distance to the radar apparatus 1 approaches), the reception level attenuates at an attenuation rate of 0.1 dB / m, and the object is positioned 10 m from the radar apparatus 2 (virtual position of the radar apparatus 1). If present in
The reception level of the electromagnetic wave becomes 5 dB.

As described above, the radar device 1 and the radar device 2
Radar device 1 except when an object exists at the midpoint between
And a difference occurs in the reception level of the electromagnetic wave in the radar device 2. Therefore, the amplitude comparator 3 is the radar device 1
And the reception level of the electromagnetic wave received by the radar device 2, and outputs the comparison result to the output device 4.

When there is a difference between the reception levels of the electromagnetic waves received by the radar device 1 and the radar device 2 in step S3, the output device 4 determines that there is an object between the radar device 1 and the radar device 2, If there is no difference, it is determined that there is no object between the radar device 1 and the radar device 2.

As described above, according to the radar system shown in FIG. 1, electromagnetic waves are respectively transmitted by the pair of radar apparatuses 1 and 2, and electromagnetic waves are respectively received by the radar apparatus 1 and the radar apparatus 2. The reception levels of the received electromagnetic waves are compared, and if there is a difference, it is determined that there is an object. If there is no difference, it is determined that there is no object. It is possible to determine the presence or absence of an object to perform.

According to the radar system of FIG. 1, the frequency of the electromagnetic wave transmitted and received by the radar device 1 and the radar device 2 is set to the frequency in the millimeter wave band.
False detection of an object due to external factors such as snow and dust can be suppressed.

In the radar system shown in FIG. 1, electromagnetic waves are transmitted and received by the radar apparatus 1 and the radar apparatus 2. However, electromagnetic waves may be transmitted and received, and the reception levels of the received electromagnetic waves may be compared.

FIG. 4 shows another example of the configuration of a radar system to which the present invention is applied. The radar system of FIG.
Although the object at the midpoint between the radar devices 1 and 2 could not be detected, the radar system of FIG. 4 can not only detect the object at the midpoint between the radar devices but also determine the distance to the object. Can also be measured. FIG.
In this radar system, radar devices 11 and 12 are provided in place of the radar devices 1 and 2 of the radar system of FIG. 1, and further, pulse detectors 13 and 14 and a signal processor 15 are provided.

The radar device 11 and the radar device 12
An electromagnetic pulse is transmitted and received. The pulse detector 13 and the pulse detector 14 detect the phase difference between the electromagnetic wave pulse transmitted by the radar device 11 and the electromagnetic wave pulse received by the radar device 12, respectively. The signal processor 15 comprehensively determines the presence or absence of an object based on the information supplied from the amplitude comparator 3, the pulse detector 13, and the pulse detector 14.

Next, the operation of the radar system of FIG. 4 will be described with reference to the flowchart of FIG. In step S11, the radar device 11 and the radar device 12
Perform sensing of each object. That is, the radar device 11 and the radar device 12 transmit electromagnetic wave pulses of the same frequency in the millimeter wave band with the same output. Then, the radar device 11 receives the electromagnetic wave pulse reflected by the object or the radar device 12. Similarly, the radar device 12 receives the electromagnetic wave pulse reflected by the object or the radar device 11. The radar device 11 and the radar device 12 supply a signal corresponding to the level of the received electromagnetic wave pulse to the amplitude comparator 3 and also outputs a signal corresponding to the transmission timing and the reception timing of the electromagnetic wave pulse to the pulse detector 13.
And to the pulse detector 14.

The amplitude comparator 3 compares the reception levels (amplitudes) of the electromagnetic wave pulses received from the radar devices 11 and 12, and outputs the comparison result to the signal processor 15. In step S12, the signal processor 15
It is determined from the output of the amplitude comparator 3 whether there is a difference between the reception levels of the electromagnetic wave pulses received by the radar devices 11 and 12, and if it is determined that there is a difference, the process proceeds to step S
Proceed to 14 to output an object detection signal. The operation in this case is the same as the operation in the radar system of FIG.

If there is no difference between the amplitudes of the received electromagnetic wave pulses, the signal processor 15 outputs the electromagnetic wave transmitted from the output of the pulse detector 13 or the pulse detector 14 by the radar device 11 or the radar device 12 in step S13. It is determined whether there is a difference between the phase of the pulse and the phase of the received electromagnetic wave pulse. If it is determined in step S13 that there is a difference in the phase of the electromagnetic wave pulse, the process proceeds to step S14.
When it is determined that there is no difference between the phases of the electromagnetic wave pulses, the process returns to step S11.

Here, steps S11 to S1
The processing in 3 will be described with reference to FIGS. 6 to 8 for the case where there is no object between the radar apparatus 11 and the radar apparatus 12 and the case where there is an object.

FIG. 6 shows a radar device 11 and a radar device 12.
FIG. 7 is a diagram for explaining transmission and reception of the radar device 11 when there is no detection object during the period. As shown in FIG. 6A, the radar apparatus 11 has an initial phase (time) of γ and a cycle of L / C.
(L is the distance between the radar device 11 and the radar device 12,
C is the speed of light (velocity of the electromagnetic wave), and transmits an electromagnetic wave pulse of 3 × 10 ⁸ m / s. That is, the radar device 1
1 transmits the next electromagnetic wave pulse when the previously transmitted electromagnetic wave pulse arrives at the radar device 12.

The electromagnetic wave pulse transmitted from the radar device 11 is reflected by the radar device 12 and, as shown in FIG. 6B, at the timing when the electromagnetic wave pulse has propagated a total distance of 2L, that is, the phase 2 × (L / C ) + Γ, which is received by the radar device 11. The level of the received electromagnetic wave pulse is lower than that of the transmitted electromagnetic wave pulse because the electromagnetic wave pulse is attenuated during propagation and at the time of reflection. The radar device 12 has the same timing as the radar device 11 (the initial phase is γ,
Since the electromagnetic wave pulse transmitted from the radar device 12 is adjusted in advance so that the electromagnetic wave pulse is transmitted so that the period becomes L / C), the electromagnetic wave pulse transmitted from the radar device 12 is
As shown in (C), the initial time L / C + γ and the period L / C
In, is received. At this time, since the propagation distance is L and there is no reflection, the reception level at this time is higher than the reception level of the reflected wave of the electromagnetic wave pulse transmitted by the radar device 11 by itself as shown in FIG.

After all, the radar device 11 transmits and receives the electromagnetic wave pulse at the initial time L / C + γ and the period L / C as shown in FIG. 6D.

FIG. 7 shows a radar device 11 and a radar device 12.
FIG. 8 is a diagram illustrating a case where an object 20 exists at a position at a distance x from the radar device 11 during the transmission. FIG. 8 is a diagram illustrating transmission and reception of electromagnetic waves in the radar device 11 in that case. In addition, as the object 20, like a metal flat plate,
Electromagnetic waves are reflected, but their magnitude is assumed to be negligible.

As shown in FIG. 8A, the radar device 11 has an initial phase γ, as in the case of FIG.
An electromagnetic pulse having a period of L / C is transmitted. The transmitted electromagnetic wave pulse is reflected by the object 20, and the reflected electromagnetic wave pulse is, as shown in FIG.
Thus, the data is received at the initial time (2x / C) + γ and the cycle L / C.

Of the electromagnetic wave pulses transmitted from the radar device 11, those not reflected by the object 20 are reflected by the radar device 12 and are reflected by the radar device 11.
Then, as shown in FIG. 8C, the initial time 2 × (L / C) +
γ, received at cycle L / C. Among the electromagnetic wave pulses transmitted from the radar device 12, the electromagnetic wave pulse not interrupted by the object 20 is received by the radar device 11 at the initial time L / C + γ and the period L / C as shown in FIG. Is done.

Accordingly, as shown in FIG. 8 (E), the radar device 11 generally obtains the time (2x / C) +
The electromagnetic wave pulse is received at the timing of γ, time (L / C) + γ, time (2x / C) + (L / C) + γ, and time 2 × (L / C) + γ. Of these, the electromagnetic wave pulse received at time (2x / C) + γ and time (2x / C) + (L / C) + γ
This is due to reflection at the object 20.

That is, the object 20 is located between the radar devices 11 and 12.
Exists, the electromagnetic wave pulse is received at a time other than the time n × (L / C) + γ (n is a natural number). Therefore, when the electromagnetic wave pulse is received at a time other than the time n × (L / C) + γ, it can be detected that the object 20 is present. Then, the position of the object 20 from the radar device 11 can be determined by calculating backward from the detected time.

Although the transmission and reception of electromagnetic wave pulses in the radar device 11 have been described with reference to FIGS. 6 to 8, the same can be said for the transmission and reception of electromagnetic wave pulses in the radar device 12.

The pulse detectors 13 and 14 detect the timing (time) of the above-described electromagnetic wave pulse, and supply the detection result to the signal processor 15. The signal processor 15 determines the presence or absence of an object based on the supplied detection result. That is,
If there is no difference in the reception level but there is a phase difference in the transmission and reception timing of the electromagnetic wave pulse, the signal processor 15 determines in step S14 that there is an object. Such a state occurs when the object is at the midpoint between the radar device 11 and the radar device 12. Thus, in this system,
The presence or absence of two objects equidistant from the radar device 11 and the radar device 12 can also be detected.

In step S14, the signal processor 15 determines the presence or absence of an object as described above, and if there is an object, supplies a detection result including the position to the output device 14.

As described above, from the difference between the phases of the electromagnetic wave pulses transmitted and received by the radar device 11 or the radar device 12, if there is a difference in phase, it is determined that there is an object. Since it is determined that there is no object, the presence or absence of the object can be determined, and the distance from the radar device 11 or the radar device 12 to the object can be measured.

In the radar system of FIG. 4, the electromagnetic wave pulse is a rectangular wave, but may be a sine wave or a cosine wave.

Further, in the radar system of FIG. 4, the reception pulse in the time zone near the timing of transmitting the electromagnetic wave pulse by the radar device 11 and the radar device 12, for example, 30% of the time L / C is used. You may ignore it. Thereby, it is possible to clearly distinguish between the reflection of the electromagnetic wave on the object and the reflection of the electromagnetic wave on the radar devices 11 and 12.

Further, in the radar system of FIG. 4, the electromagnetic wave pulses are transmitted and received by the radar device 11 and the radar device 12. However, electromagnetic waves without pulse demultiplexing are transmitted and received, and the phase of the transmitted electromagnetic wave and the phase of the received electromagnetic wave are changed. May be compared.

In the above, the radar device 1 (radar device 11) and the radar device 2 (radar device 12) are arranged so as to face each other, but as shown in FIG.
And the radar device 1 (radar device 11) and the radar device 2 (radar device 12) may be arranged obliquely with respect to the wall 30 so that electromagnetic waves can be transmitted and received from oblique directions. In this case, the electromagnetic waves are transmitted from the radar apparatus 1 (radar apparatus 11) and the radar apparatus 2 (radar apparatus 12), and the reception level difference (reception level difference and phase difference) of the received electromagnetic waves is compared. Can be determined. The output levels of the radar device 1 (radar device 11) and the radar device 2 (radar device 12) may be different as long as they are known.

In the above description, the electromagnetic wave (electromagnetic wave pulse) in the millimeter wave band is transmitted and received. However, the electromagnetic wave in the millimeter wave band or more, for example, light and infrared light may be transmitted and received.

In the present specification, a recording medium for providing a user with a computer program for executing the above processing includes an information recording medium such as a magnetic disk and a CD-ROM, and a network such as the Internet and a digital satellite. Transmission media is also included.

[0052]

As described above, according to the radar system according to the first aspect, the object detection method according to the seventh aspect, and the recording medium according to the eighth aspect, the first and second transmission / reception means , The electromagnetic waves transmitted and received by the first and second electromagnetic waves are compared.
And an object existing between the second transmitting / receiving means can be accurately detected.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration example of a radar system to which the present invention has been applied.

FIG. 2 is a flowchart illustrating an operation of the radar system of FIG. 1;

FIG. 3 is a diagram illustrating reception levels of the radar devices 1 and 2;

FIG. 4 is a block diagram showing another configuration example of a radar system to which the present invention is applied.

FIG. 5 is a flowchart illustrating an operation of the radar system of FIG. 4;

FIG. 6 is a diagram illustrating electromagnetic wave pulses transmitted and received from the radar devices 11 and 12;

FIG. 7 is a diagram illustrating the position of an object 20.

FIG. 8 is another diagram illustrating electromagnetic wave pulses transmitted and received from the radar devices 11 and 12.

FIG. 9 is a diagram illustrating another arrangement of the radar devices 1 and 2 (11, 12).

[Explanation of symbols]

 1, 2, 11, 12 radar device, 3 amplitude comparator, 4 output device, 13, 14 pulse detector, 15 signal processor, 20 objects, 30 wall

Claims (8)

[Claims] A first transmitting / receiving means for transmitting / receiving electromagnetic waves; a second transmitting / receiving means for transmitting / receiving electromagnetic waves; and a comparing means for comparing electromagnetic waves received by the first transmitting / receiving means and the second transmitting / receiving means. And a detecting means for detecting an object existing between the first transmitting / receiving means and the second transmitting / receiving means based on a result of the comparison by the comparing means. 2. The radar system according to claim 1, wherein the electromagnetic waves transmitted and received by the first transmitting / receiving means and the second transmitting / receiving means have the same frequency and level. 3. The apparatus according to claim 1, wherein the first transmitting / receiving means and the second transmitting / receiving means are arranged to face each other so as to receive the other transmitted electromagnetic wave. Radar system. 4. The apparatus according to claim 1, wherein said comparing means compares a difference between amplitudes of electromagnetic waves received by said first transmitting / receiving means and said second transmitting / receiving means. Radar system. 5. The electromagnetic wave is an electromagnetic wave pulse, and the comparing means compares the phase difference between the electromagnetic wave pulse transmitted by the first transmitting / receiving means or the second transmitting / receiving means and the received electromagnetic wave pulse. The radar system according to any one of claims 1 to 4, wherein: 6. The radar system according to claim 1, wherein the frequency of the electromagnetic wave is a frequency equal to or higher than a millimeter wave band. 7. A method for detecting an object in a radar apparatus comprising a first transmitting / receiving apparatus and a second transmitting / receiving apparatus for transmitting / receiving electromagnetic waves, wherein: a first transmitting / receiving step of transmitting / receiving electromagnetic waves by the first transmitting / receiving apparatus; A second transmitting / receiving step of transmitting / receiving electromagnetic waves by the second transmitting / receiving device, a comparing step of comparing the electromagnetic waves received in the first transmitting / receiving step and the second transmitting / receiving step, and a result compared in the comparing step. A detection step of detecting an object existing between the first transmission / reception device and the second transmission / reception device based on the information. 8. A radar device comprising a first transmitting / receiving device and a second transmitting / receiving device for transmitting / receiving electromagnetic waves, a first transmitting / receiving step of transmitting / receiving electromagnetic waves by the first transmitting / receiving device, and a second transmitting / receiving device A second transmitting / receiving step of transmitting / receiving electromagnetic waves according to: a comparing step of comparing the electromagnetic waves received in the first transmitting / receiving step and the second transmitting / receiving step; based on a result compared in the comparing step, A recording medium recording a computer-readable program for executing a process including a detecting step of detecting an object existing between a first transmitting / receiving device and the second transmitting / receiving device.