JP2003043142A - Microwave sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately recognize the moving direction of an object to an MW sensor for detecting the object by using a plurality of microwaves different in a frequency without requiring complicated processing operation such as arithmetically processing a large number of position data on the object. SOLUTION: Two kinds of microwaves different in the frequency are transmitted to a detecting area, and these XNOR waveforms are formed with two IF signal waveforms obtained by a reflected wave as a rectangular wave. A relative phase lead degree of the mutual respective IF signal waveforms is recognized by detecting values of the respective rectangular waves when switching the XNOR waveforms. When the IF signal waveforms obtained by the microwaves having a low frequency advances more than the IF signal waveforms obtained by the microwaves having a high frequency, it is discriminated that the object moves in the approaching direction, and in an inverse case, it is discriminated that the object moves in the going-away direction.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave sensor (hereinafter referred to as "MW sensor") which is an active sensor using an electromagnetic wave having a lower frequency than visible light.
In particular, the present invention relates to an improvement of an MW sensor that detects an object using a plurality of microwaves having different frequencies.

[0002]

2. Description of the Related Art Conventionally, as one of the crime prevention devices, a microwave is transmitted toward a detection area, and when a human body is present in the detection area, a reflected wave from the human body (modulated by the Doppler effect is modulated. An MW sensor that receives a microwave) to detect a human body (intruder) is known (for example, Japanese Patent Laid-Open No. 7-37176).

Further, as one type of MW sensor, there is known a type in which a plurality of microwaves having different frequencies are used to measure a distance to an object. This type of sensor transmits, for example, two types of microwaves having different frequencies toward a detection area, and two types of microwaves based on the respective reflected waves are transmitted.
The phase difference between the two IF signals is detected. This phase difference has a correlation with the distance to the target (object such as a human body), and the phase difference tends to increase as the distance to the target increases. That is, it is possible to measure the distance to the target by obtaining this phase difference. Hereinafter, the phase difference detection operation of the IF signal in this type of sensor will be described.

An IF signal based on reflected waves of two kinds of microwaves having different frequencies is a sine wave I as shown in FIG.
In the case of Fout1 and IFout2 (having a phase difference according to the distance to the target), rectangular waves A and B formed from these IF signals are as shown in FIG. 4B, respectively. Then, the distance to the target can be measured by detecting the phase difference between the rectangular waves A and B (the phase difference Δt at the rising portion of the rectangular wave in the figure).

[0005]

By the way, when this type of sensor is used as a security device, there is a demand not only to recognize the distance to an intruder but also to recognize the intrusion route or the escape route. For that purpose, it is necessary to recognize the moving direction of the intruder in the detection area.

In the above-mentioned one that detects the phase difference of the IF signal, it is possible to measure the distance from the sensor to the intruder. Therefore, the distance from the sensor to the intruder is continuously measured, and this is obtained. It is possible to recognize the intrusion route and the escape route based on the obtained large number of measurement data. That is, it is possible to obtain the intrusion route and the escape route by a calculation process such as calculating the amount of change in the distance to the intruder that changes moment by moment and estimating the moving direction of the intruder.

However, this not only requires acquisition of a large number of measurement data (intruder position (distance from the sensor) data), but also a complicated processing operation such as comparison calculation processing of these many measurement data. You will need it. That is, hitherto, no technology has been constructed to directly recognize the moving direction of the intruder by the MW sensor.

The present invention has been made in view of the above points, and its object is to detect an object by utilizing a plurality of microwaves having different frequencies.
An object of the present invention is to enable a sensor to accurately recognize the moving direction of an object without requiring a complicated processing operation such as arithmetic processing of a large number of position data of the object.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a relative phase of a plurality of IF signals based on reflected waves of each microwave transmitted to a detection area. The moving direction of the target can be recognized by recognizing the degree of progress.

-Solution means-Specifically, according to the present invention, a plurality of microwaves having different frequencies are transmitted toward a detection area, and when an object exists in the detection area, reflection of each microwave by the object. It is premised on a microwave sensor that detects an object by receiving waves. In this microwave sensor, by recognizing the relative phase advance degree of a plurality of IF signal waveforms obtained by the reflected waves of each microwave, the direction in which the object in the detection area is moving toward or away from It is equipped with a moving direction discriminating means for discriminating whether or not it is moving.

As a specific movement direction determining operation of the object by the movement direction determining means, an IF obtained by a reflected wave of a microwave having a low frequency among a plurality of IF signal waveforms is used.
When the signal waveform is ahead of the IF signal waveform obtained by the reflected wave of the high frequency microwave, it is determined that the object in the detection area is moving in the approaching direction, and the reflection of the high frequency microwave The IF signal waveform obtained by the wave is the IF obtained by the reflected wave of the low frequency microwave.
If it is ahead of the signal waveform, it is determined that the object in the detection area is moving away.

The relationship between the microwave and the Doppler signal based on the reflected wave when the object is moving in the direction approaching the sensor and in the direction moving away from the sensor is as follows.

When transmitting two types of microwaves to the detection area, the respective frequencies are f1 and f2, the Doppler signals are V1 and V2, the Doppler frequency is fd, the distance to the object is R, and the speed of light is C. When the object is moving in the approaching direction, the following equations (1) and (2) are established, and when f1 <f2, the phase of V1 leads the phase of V2.

V1 = sin (2π · fd · t-4π · f1 · R / C) (1) V2 = sin (2π · fd · t-4π · f2 · R / C) (2) Conversely, When the object is moving away, the following (3) and (4) hold, and when f1 <f2, V
The phase of 2 leads the phase of V1.

V1 = sin (−2π · fd · t−4π · f1 · R / C) = − sin (2π · fd · t + 4π · f1 · R / C) (3) V2 = sin (−2π · fd) -T-4 (pi) * f2 * R / C) =-sin (2 (pi) * fd * t + 4 (pi) * f2 * R / C) ... (4) This principle is utilized and in this invention, several IF signal waveforms are relative. By recognizing the degree of phase advance,
The moving direction of the object within the detection area can be determined.

Then, as a configuration for identifying which IF signal waveform leads the phase of other IF signal waveforms, the following configurations are listed.

That is, a plurality of IF signal waveforms are shaped as a rectangular wave, and an XOR (exclusive logical sum) waveform or an XNOR (exclusive negative logical sum) waveform of the rectangular waveforms of these IF signals are shaped, and this rectangular waveform is shaped. By detecting the value of the rectangular wave of each IF signal at the time of switching between Hi and Lo, the relative phase advance degree of each IF signal waveform is recognized.

Hi of the above XOR waveform or XNOR waveform
The values of the rectangular waves of the IF signals are different at the time of switching between the IF signal and the Lo signal. By detecting the values of the rectangular waves of the IF signals, the relative degree of phase advance between the IF signal waveforms can be recognized. . That is, the moving direction of the object in the detection area can be determined by the above principle.

Specifically, for example, the NXOR waveform (FIG. 2) of the rectangular wave (two waveforms in the upper stage in FIG. 2) of each IF signal is used.
Waveform (bottom waveform) in the lower edge (from Hi to Lo
When the rectangular wave (waveform B in FIG. 2) of the IF signal waveform obtained by the reflected wave of the high frequency microwave is Lo, the The rectangular wave (waveform A in FIG. 2) of the obtained IF signal waveform is the timing at which Lo is switched to Hi (timing II in FIG. 2), or the IF signal waveform obtained by the reflected wave of the high frequency microwave is When the rectangular wave B is Hi, the rectangular wave A of the IF signal waveform obtained by the reflected wave of the low frequency microwave is Hi.
In the case of the timing of switching from Low to Lo (timing I in FIG. 2), I generated by the microwave having a low frequency is used.
It can be recognized that the rectangular wave A of the F signal waveform leads the phase of the rectangular wave B of the IF signal waveform due to the high frequency microwave. Accordingly, it can be determined that the object in the detection area is moving in the direction approaching the sensor.

On the contrary, at the down edge of the NXOR waveform of the rectangular wave of each IF signal (at the time of switching from Hi to Lo), the rectangular wave of the IF signal waveform obtained by the reflected wave of the low frequency microwave (see FIG. When the waveform A) in FIG. 3 is Lo, the rectangular wave (waveform B in FIG. 2) of the IF signal waveform obtained by the reflected wave of the microwave having a high frequency is switched from Lo to Hi (timing in FIG. 3). IV) or when the rectangular wave A of the IF signal waveform obtained by the reflected wave of the low frequency microwave is Hi, I obtained by the reflected wave of the high frequency microwave
When the rectangular wave B of the F signal waveform is at the timing of switching from Hi to Lo (timing III in FIG. 3), the rectangular wave B of the IF signal waveform of the high frequency microwave is the IF signal of the low frequency microwave. It can be recognized that the phase is ahead of the rectangular wave A of the waveform. This allows
It can be determined that the object in the detection area is moving away from the sensor.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. Here, a case will be described in which the MW sensor is used as a crime prevention sensor and the moving direction of an object (intruder or the like) is determined by using two types of microwaves having different frequencies.

-Description of MW Sensor Configuration- FIG. 1 shows a circuit configuration of the MW sensor 1 according to the present embodiment. As shown in this figure, the MW sensor 1 includes an RF module 2 and a signal processing unit 3.

The RF module 2 includes an oscillator 21 for oscillating a microwave, a modulator 22 for switching the frequency of the microwave oscillated from the oscillator 21, and an oscillator 21.
A transmitting antenna 23 for transmitting the microwave oscillated from the antenna to the detection area, a receiving antenna 24 for receiving the reflected wave of the microwave reflected by an object such as a human body, the received microwave and the voltage waveform of the oscillator 21. Is provided with a mixer 25 for mixing and outputting. In other words, the microwave transmitted from the transmitting antenna 23 toward the detection area is received by the receiving antenna 24 when the frequency of the reflected wave from the human body is modulated by the Doppler effect when the human body exists in the detection area. To be done. The received reflected wave is mixed with the voltage waveform of the oscillator 21 by the mixer 25, and then output from the RF module 2 to the signal processing unit 3 as an IF output signal (IFout0).

On the other hand, the signal processing section 3 includes a transmitting antenna 23.
A first output line L1 and a second output line L2 are provided corresponding to each microwave of each frequency transmitted from. The power sources 31, 32, 33, and
The IF amplifiers 34 and 35 and the comparators 36 and 37 are provided, and the output sides of the comparators 36 and 37 are a moving direction discriminating unit 38 as a moving direction discriminating means which is a feature of this embodiment.
Is provided.

Each IF amplifier 34, 35 is connected to the output side of the RF module 2 via the first switch SW1. The first switch SW1 connects to the first output line L1 when one of the two types of microwaves is transmitted from the transmitting antenna 23, and the other microwave is transmitted from the transmitting antenna 23. If so, it is switched to connect to the second output line L2.
That is, the IF output signal (IFout1) related to the reflected wave reflected by the human body or the like during the transmission of one microwave is output to the first output line L1 and reflected by the human body or the like during the transmission of the other microwave. The IF output signal (IFout2) related to the wave is output to the second output line L2.

Further, each of the power sources 31 and 32 is connected to the RF through the second switch SW2 which is interlocked with the first switch SW1.
It is connected to the input side of module 2. The second switch SW2 is also adapted to switch the connection state to the power sources 31 and 32 depending on which microwave of the two types of microwaves is transmitted from the transmitting antenna 23. That is, the second switch SW2 is connected to the one power source 3
The modulator 22 switches the frequency of the microwave depending on whether it is connected to the power source 1 or the power source 32 on the other side, whereby the frequency of the microwave transmitted from the transmitting antenna 23 is switched. Has become.

In this way, the switches SW1 and SW
In accordance with the switching operation of 2, the microwave of one frequency is transmitted from the transmitting antenna 23 toward the detection area, and the IF output signal (IFout1) based on the reflected wave is output to the first output line L1 of the signal processing unit 3. The first processing operation of outputting and performing signal processing on the first output line L1 and the microwave of the other frequency are transmitted from the transmitting antenna 23 toward the detection area, and I based on the reflected wave is transmitted.
The F output signal (IFout2) is output to the second output line L2 of the signal processing unit 3 and the second processing operation in which the signal processing is performed on the second output line L2 has a predetermined time interval (for example, several msec). It can be switched. Then, in each processing operation, the IF output signal output from the RF module 2 is amplified by the IF amplifiers 34 and 35, and the outputs from the IF amplifiers 34 and 35 are shaped into rectangular waves by the comparators 36 and 37. It is adapted to be output to the moving direction discriminating section 38.

Further, each processing operation will be described in detail. When no human body is present in the detection area,
Since the frequencies of the microwaves transmitted from the transmitting antenna 23 and the microwaves received by the receiving antenna 24 are equal, the IF in the output signals from the IF amplifiers 34 and 35 is
The frequency becomes “0”, and no signal is output from the comparators 36 and 37. On the other hand, when a human body or the like exists in the detection area, the microwave received by the receiving antenna 24 is modulated with respect to the frequency of the microwave transmitted from the transmitting antenna 23, so that the comparator 3
The output signal waveforms of Nos. 6 and 37 change, and this rectangular wave is output to the moving direction determination unit 38.

-Processing Operation of Moving Direction Discriminating Section 38- Next, a processing operation of the moving direction discriminating section 38 which receives output signal waveforms from the comparators 36 and 37 will be described.

The moving direction discriminating section 38 compares the rectangular waves A and B of the two types of IF signal waveforms received from the comparators 36 and 37, and recognizes the relative phase advance degree of these IF signal waveforms. Thus, it is determined whether the object in the detection area is moving in the direction approaching the MW sensor 1 or in the direction moving away from the MW sensor 1. When the IF signal waveform obtained by the reflected wave of the low frequency microwave out of the two IF signal waveforms is ahead of the IF signal waveform obtained by the reflected wave of the high frequency microwave, the detection area is detected. It is determined that the object inside is moving toward the MW sensor 1. on the other hand,
When the IF signal waveform obtained by the reflected wave of the microwave having a high frequency is ahead of the IF signal waveform obtained by the reflected wave of the microwave having a low frequency, the object in the detection area moves away from the MW sensor 1. It is designed to determine that it is moving in the direction. Hereinafter, this determination operation will be described in detail.

Now, the rectangular waves of the two types of IF signal waveforms received from the comparators 36 and 37 are the waveforms A and B shown in FIG.
It was assumed that And XNOR of these waveforms
A waveform (the waveform at the bottom of FIG. 2) is shaped. At the time of switching between Hi and Lo of this XNOR waveform,
At the time of switching from Hi to Lo (eg, arrow I,
The values of the rectangular waves A and B of each IF signal at the time of attaching II) are detected. In the case of FIG. 2, at the time of switching from Hi to Lo (two respective times indicated by arrows I and II), if the rectangular wave B is Lo, the rectangular wave A is L.
It is the timing of switching from o to Hi (arrow II),
When the rectangular wave B is Hi, the rectangular wave A is changed from Hi to Lo.
This is the timing (arrow I) for switching to. When this state is detected, the IF caused by the low frequency microwave
The rectangular wave A of the signal waveform is I due to the high frequency microwave.
It can be recognized that the phase is ahead of the rectangular wave B of the F signal waveform. In this case, the moving direction determination unit 38 determines that the object in the detection area is moving in the direction approaching the MW sensor 1. In this case, the XNOR waveform changes from Hi to L
At the time of switching to o, the rectangular wave B always remains in the Lo or Hi state, and the rectangular wave A changes from Hi to Lo or L.
Since it is the timing to switch from o to Hi,
It is also possible to determine that the object in the detection area is moving toward the MW sensor 1 by detecting the state of either of the rectangular waves A and B.

On the other hand, the rectangular waves of the two types of IF signal waveforms received from the comparators 36 and 37 are the waveforms A and A shown in FIG.
In the case of B, the XNOR waveforms of these waveforms are as shown at the bottom of FIG. And, Hi and L of this XNOR waveform
The values of the rectangular waves A and B of each IF signal at the time of switching from Hi to Lo (for example, the time points indicated by arrows III and IV in FIG. 3) are detected. In the case of FIG. 3, this time point of switching from Hi to Lo (arrow II
At each of the two time points labeled I and IV), a square wave A
When Lo is Lo, the rectangular wave B is a timing (arrow IV) at which Lo is switched to Hi (arrow IV), and when the rectangular wave A is Hi, a timing at which the rectangular wave B is switched from Hi to Lo (arrow III). Is. By detecting this state, it can be recognized that the rectangular wave B of the IF signal waveform of the microwave having a high frequency is in advance of the phase of the rectangular wave A of the IF signal waveform of the microwave of a high frequency. In this case, the moving direction determination unit 38 determines that the object in the detection area is M
It is determined that it is moving in a direction away from the W sensor 1. In addition, at the time when the XNOR waveform in this case is switched from Hi to Lo, the rectangular wave A is always in the Lo or Hi state, and the rectangular wave B is from Hi to Lo or Lo to H.
Since it is the timing to switch to i, it is determined that the object in the detection area is moving in the direction away from the MW sensor 1 by detecting the state of either of the rectangular waves A and B. You can also

As described above, in the present embodiment, the moving direction of the object is recognized by recognizing the relative degree of phase advance of a plurality of IF signals based on the reflected waves of each microwave transmitted to the detection area. can do. That is, it is possible to quickly and accurately recognize the moving direction of an object without acquiring a lot of object position data and performing a complicated processing operation such as a comparison calculation processing of these data. As a result, it is possible to provide the MW sensor 1 capable of directly recognizing the moving direction of the intruder, which has not been constructed so far.

-Other Embodiments-In the above-described embodiment, the moving direction discriminating section 38 shapes the XNOR of the rectangular wave of the two kinds of IF signal waveforms received from the comparators 36 and 37, and the waveform Hi and Hi. At the time of switching to Lo and at the time of switching from Hi to Lo, the value of the rectangular wave of each IF signal is detected to recognize the relative phase advance degree between the two types of IF signal waveforms. Was there. The present invention is not limited to this, and XNO
Each IF at the time when the R waveform switches from Lo to Hi
The value of the rectangular wave of the signal may be detected. Also,
The XOR (exclusive OR) of the rectangular waves of the two types of IF signal waveforms received from the respective comparators 36 and 37 is formed, and the rectangular wave value of each IF signal at the time of switching between Hi and Lo of this waveform is calculated. You may make it detect.

Further, in the above embodiment, the MW sensor 1 has been described in which two types of microwaves having different frequencies are used to determine the moving direction of the object. The present invention is not limited to this, and the moving direction of the object may be determined using three or more types of microwaves having different frequencies.

[0036]

As described above, according to the present invention, the reflection of each microwave transmitted to the detection area is reflected by the MW sensor which detects an object using a plurality of microwaves having different frequencies. The moving direction of the object can be recognized by recognizing the relative degree of phase advance of a plurality of IF signals based on the waves. Therefore, it is possible to quickly and accurately recognize the moving direction of the object without acquiring a lot of object position data and performing a complicated processing operation such as comparison calculation processing of these data.

Further, a plurality of IF signal waveforms are shaped as a rectangular wave, and the XOR waveform or X of the rectangular waves of these IF signals is formed.
A NOR waveform is shaped, and by detecting the value of a rectangular wave of each IF signal at the time of switching between Hi and Lo of this waveform, the relative phase advance degree of each IF signal waveform is recognized. In this case, the operation of recognizing the degree of phase advance of these waveforms can be performed easily and quickly.

[Brief description of drawings]

FIG. 1 is a diagram showing a circuit configuration of an MW sensor according to an embodiment.

FIG. 2 is a diagram showing two types of IF signal waveform rectangular waves received from each comparator and a XNOR waveform thereof when an object approaches a sensor.

FIG. 3 is a diagram showing two types of rectangular waveforms of IF signal waveforms received from each comparator and a XNOR waveform thereof when an object moves away from a sensor.

FIG. 4 is a diagram showing each IF signal and a rectangular wave obtained thereby in a conventional example.

[Explanation of symbols]

1 Microwave sensor 38 Movement Direction Discriminating Section (Movement Direction Discriminating Means)

Continued front page    F-term (reference) 2G005 DA04                 5C084 AA02 AA07 AA13 BB33 CC16                       CC19 DD06 DD08 EE02 GG03                       GG07 GG09 GG18 GG24 GG37                       GG55 GG56 GG57 GG61 GG71                       GG74                 5J070 AB15 AB21 AC15 AE09 AF01                       AK13 AK31 BA01

Claims (3)

[Claims] 1. An object is detected by transmitting a plurality of microwaves having different frequencies toward a detection area and receiving a reflected wave of each microwave when the object is present in the detection area. In the microwave sensor, by recognizing the relative phase advance degree of the plurality of IF signal waveforms obtained by the reflected waves of the above microwaves, the object in the detection area is moved toward or away from the approaching area. A microwave sensor, characterized in that it is provided with a moving direction judging means for judging whether or not it is moving. 2. The microwave sensor according to claim 1, wherein the moving direction determination means is a plurality of IF signal waveforms, and the IF signal waveform obtained by the reflected wave of the microwave having a low frequency is a microwave of a high frequency. IF obtained by reflected wave
If it is ahead of the signal waveform, it is judged that the object in the detection area is moving in the approaching direction, and the IF signal waveform obtained by the reflected wave of the high frequency microwave is reflected by the low frequency microwave. A microwave sensor configured to determine that an object in a detection area is moving away from the IF signal waveform obtained by the wave. 3. The microwave sensor according to claim 1 or 2, wherein the moving direction discriminating means shapes a plurality of IF signal waveforms as rectangular waves, and XOR (exclusive OR) waveforms of the rectangular waves of these IF signals. Alternatively, an XNOR (exclusive NOR) waveform is shaped, and the relative phase of each IF signal waveform is detected by detecting the value of the rectangular wave of each IF signal at the time of switching between Hi and Lo of this waveform. A microwave sensor characterized by being configured to recognize the degree of progress.