JP2003329769A - Method and sensor for detecting interruption of microwave - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method and its sensor for detecting the interruption of microwaves capable of estimating an object, to some degree, intruding between a transmission antenna and a reception antenna, and heightening a function as a sensor for accurately specifying the size of the intruding object. <P>SOLUTION: Oscillation output of a microwave oscillator 1 is transmitted from a transmission antenna 2 and received by a reception antenna 3 opposite to the transmission antenna 2 to detect the size of an object 9 passing in-between. A reception signal received by the reception antenna 3 is mixed by a local oscillator 4 and a mixer 5 to create an intermediate frequency signal. The phase of the intermediate frequency signal is detected by a phase detector 8 with reference to the phase of a reference oscillator 6. A PLL circuit for controlling the local oscillator 4 via a phase comparator 7 in such a way that the frequency of the intermediate frequency signal becomes equal to the frequency of the reference oscillator 6 is formed. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave in a case where a transmitting antenna and a receiving antenna for microwaves are opposed to each other in order to guard against the invasion of a suspicious person by the microwave, and the like. The present invention relates to a cutoff sensor and a microwave cutoff detection method. More specifically, the present invention relates to a microwave cutoff sensor and a detection method thereof that can detect the magnitude of microwaves to know what they are.

[0002]

2. Description of the Related Art As a conventional method for detecting an intrusion into a dangerous area, an intrusion into a building, an intrusion into a defense facility, a light emitting element and a light receiving element are opposed to each other and a light beam is used. When a suspicious person crosses the gap, a method of detecting by a light receiving element by blocking light is used. Further, if there is a device that uses a microwave instead of light and similarly blocks a transmission antenna and a reception antenna so as to oppose each other, a part of the received microwave is cut off and becomes smaller, which is detected. Methods have also been used.

When light is used, since the beam spot is small, the detection area is very limited, and it is difficult to detect the size of an object that blocks the light beam.
For example, there is a problem that even if a tree leaf falls, it is detected as much as a human being passes. On the other hand, when a microwave is used, the beam width is wide, and if the size of the object that blocks the transmission antenna and the reception antenna is large, the amount of attenuation increases, and the size of the blocked object can be estimated to some extent. be able to.

That is, as shown in FIG. 2, when objects P, Q, W having different sizes enter between the transmitting antenna 21 and the receiving antenna 22, they exit the transmitting antenna 21 and enter the receiving antenna 22. Microwave beam B
Has a spread, so that both the small object P and the large object W block microwaves according to their sizes. If the microwave is cut off in a large area, the microwave received by the receiving antenna 22 will be attenuated substantially in proportion to its cross-sectional area. Therefore, by detecting the magnitude of the power (intensity) of the received signal, , The intruding object is P, Q, W
You can know which of these.

[0005]

As described above, according to the cutoff sensor using the microwave, the size of the intruder can be known to some extent by the electric power received by the receiving antenna. However, in this method, the absolute value of the power received by the receiver is used for judgment, but in the long-term range, the transmission power of the microwave oscillator and the reception sensitivity of the receiver generally decrease and fluctuate. However, maintaining long-term stability is a problem, misidentification due to multiple reflections is likely to occur, and misidentification is likely to occur if there is something that easily absorbs microwaves due to rain, etc. There is. Therefore, it is unreliable in terms of accurately detecting the size of the object and has not been put to practical use.

On the other hand, if it is possible to know the size of an object that enters between the transmitting antenna and the receiving antenna, for example, in the case of detecting an intrusion into a house or the like, it is an intrusion of a human or an invasion of a dog or a cat. If it is possible to know whether or not this is the case, it is possible to become a highly effective sensor as it becomes more sophisticated as a sensor without issuing an unnecessary alarm.

The present invention has been made in view of such a situation, and even if the output of the microwave oscillator fluctuates,
By accurately specifying the size of an intruding object between the transmitting antenna and the receiving antenna, the intruding object can be guessed to some extent to enhance the function as a sensor. It is intended to provide a sensor.

[0008]

The present inventor has conducted extensive studies in order to accurately detect the size of an object penetrating between a transmitting antenna and a receiving antenna, and as a result, as described above,
Depending on the size of the intruder, the microwave is blocked and the amount of microwave received by the receiving antenna is reduced,
At the same time, the microwave transmitted from the transmitting antenna is shown in FIG.
As indicated by an arrow A, the object 9 which bypasses the invading object arrives at the receiving antenna 3, and the detoured microwave reaches the receiving antenna with a phase delay. Since the distance increases, the phase delay also increases, and it was found that the size of the intruding object can be predicted by detecting the magnitude of this phase delay.

The microwave cutoff detection method according to the present invention comprises:
A method of detecting a device that opposes a transmitting antenna and a receiving antenna for microwaves to cut off between the transmitting antenna and the receiving antenna, and has a reference oscillator that oscillates at a constant frequency, and reception by the receiving antenna. A signal is mixed with a local oscillation signal to generate an intermediate frequency signal having the same frequency as that of the reference oscillator, and the phase of the intermediate frequency signal is detected by using the phase of the reference oscillator as a reference. It is characterized by detecting the size of an object that blocks the space between the antennas.

Here, the reference oscillator means, for example, a crystal oscillator that constantly oscillates at a constant frequency with almost no change over time.

According to this method, since the phase change which depends only on the existence of the object is detected, only the information of the object can be detected without being affected by the decrease in the output of the microwave oscillator and the decrease in the sensitivity of the receiver. You can Moreover, since the oscillation frequency of the local oscillator is adjusted so that the frequency of the intermediate frequency signal matches the oscillation frequency of the reference oscillator, even if the oscillation frequency of the microwave oscillator drifts,
The frequency change can be completely removed, and information that depends only on the phase of the intruding object can be detected. Further, since the amount of change in the phase information varies depending on the size of the object penetrating between the transmitting antenna and the receiving antenna, it is possible to accurately detect the size of the object that blocks the microwave. As a result, it is possible to completely eliminate the changes over time of the measuring system, changes due to external conditions such as multiple reflections and the environment, and to detect the information of only the intruding object, and to know the size of the intruding object accurately. You can

In order to match the frequency of the intermediate frequency signal with the oscillation frequency of the reference oscillator, a PLL for controlling the oscillation frequency of the local oscillator is constructed by comparing the phases of the intermediate frequency signal and the reference oscillator. It is preferable to do so because even if the oscillation frequency of the microwave oscillator shifts due to drift or the like, it does not affect the phase change due to the intruding object to be measured.

A microwave cutoff sensor according to the present invention is provided with a microwave oscillator, a transmitting antenna for transmitting an oscillation output of the microwave oscillator, a signal transmitting from the transmitting antenna, the signal being transmitted from the transmitting antenna. A reception antenna for receiving, a local oscillator capable of electronic tuning for generating an intermediate frequency signal of a reception signal received by the reception antenna, an oscillation signal of the local oscillator and a reception signal received by the reception antenna are mixed. A mixer for generating an intermediate frequency signal, a reference oscillator for generating a signal of a constant frequency, the oscillation frequency of the reference oscillator and the frequency of the intermediate frequency signal generated by the mixer are compared, and both frequencies are compared. Generated by a phase comparator that sends a control signal to the local oscillator so that there is no difference, and the mixer with the phase of the reference oscillator as a reference It consists a phase detector for detecting the phase of the intermediate frequency signal.

The presence and size of an intruding object can be detected by both the phase and the signal strength (amplitude) by further including a signal strength detector for detecting the signal strength of the intermediate frequency signal generated by the mixer. Therefore, it is preferable because the accuracy can be further ensured.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION Next, a microwave cutoff sensor of the present invention and a detection method thereof will be described with reference to the drawings. In the microwave cutoff sensor according to the present invention, the oscillation output of the microwave oscillator 1 is transmitted to the transmission antenna 2 as shown in the block diagram of the configuration example of the embodiment in FIG.
And the size of an object 9 passing therebetween is detected by the receiving antenna 3 provided facing the transmitting antenna 2. The received signal received by the receiving antenna 3 is mixed by the local oscillator 4 and the mixer 5 to generate an intermediate frequency signal which is the difference between the frequencies of the two,
The phase of the intermediate frequency signal is detected by the phase detector 8 with reference to the phase of the reference oscillator 6. P which controls the local oscillator 4 via the phase comparator 7 so that the frequency of the intermediate frequency signal becomes the same as the frequency of the reference oscillator 6.
An LL circuit is formed.

The oscillating output of the microwave oscillator 1 is transmitted by the transmitting antenna 2, and the received signal received by the receiving antenna 3 is mixed with the signal of the local oscillator 4 by the mixer 5 to generate the intermediate frequency signal IF. The configuration for processing is similar to that of the conventional radar device. In the present invention, a VCO (voltage controlled oscillator) is used as the local oscillator 4.
An electronically tunable oscillator such as a cillator) is used, and the PLL circuit is configured so that the frequency of the intermediate frequency signal IF becomes the same as the frequency of the reference oscillator 6 that oscillates at a stable frequency such as a crystal oscillator. The frequency of the intermediate frequency signal is kept constant and the phase change is detected by the phase detector 8.

That is, the mixer 5 generates an intermediate frequency signal having a frequency difference between the received signal and the local oscillator 4, and the intermediate frequency signal IF is amplified by the IF amplifier 10,
The oscillation signal of the crystal oscillator 6 is input to the phase comparator 7, and the phase comparator 7 compares the frequencies of the two and feeds them back to the local oscillator 4 so that the frequencies match, thereby oscillating the local oscillator 4. A loop is formed whose frequency is adjusted. This is because when the oscillation frequency of the microwave oscillator 1 or the local oscillator 4 changes, the phase also changes due to the change of the frequency, so that the phase change of the received signal cannot be accurately grasped.

For example, the oscillation frequency of the microwave oscillator 1 is set to 10.525 GHz, the oscillation frequency of the local oscillator 4 is set to 10.515 GHz, and the oscillation frequency of the crystal oscillator, which is the reference oscillator 6, is 10 MHz. In this case, if the respective frequencies are maintained as they are, the frequency of the intermediate frequency signal is 10 MHz, which is the same as the oscillation frequency of the reference oscillator 6. However, the reference oscillator 6
Although the oscillating frequency does not substantially change even if the ambient environment such as the temperature changes, the microwave oscillator 1 and the local oscillator 4, which are transmitters, change in frequency depending on the ambient temperature and the operating time. Therefore, for example, when the frequency of the intermediate frequency signal, which is the difference between the two, is 9 MHz, which is lower than the oscillation frequency of the reference oscillator 6, the phase comparator 7 lowers the oscillation frequency of the local oscillator 4. Control. As a result, the frequency of the intermediate frequency signal increases, and if this relationship is reversed, the oscillation frequency of the local oscillator 4 is controlled to increase, and the PLL repeats this operation to set the frequency of the intermediate frequency signal to the reference oscillator 6 Match the frequency of.

The phase detector 8 is a general phase detection IC.
Can be used to detect the phase change of the intermediate frequency signal by measuring the phase of the intermediate frequency signal with reference to the phase of the reference oscillator 6, that is, the change of the phase due to the intruded object 9 of the transmission signal. is there.

As is clear from the above description of the apparatus,
The microwave cutoff detection method according to the present invention, in the case where the microwave transmission antenna 2 and the microwave reception antenna 2 are opposed to each other and a substance that enters and blocks between them is detected,
By using the PLL circuit, the frequency of the intermediate frequency signal is matched with the oscillation frequency of the reference oscillator 6 serving as a reference, and the phase of the intermediate frequency signal is detected by the phase detector 8 using the phase of the reference oscillator as a reference. The feature is that the size of the object is detected.

That is, if there is no obstacle between the transmitting antenna 2 and the receiving antenna 3, the distance between the transmitting antenna 2 and the receiving antenna 3 is constant, so the phase associated with the distance is always constant. However, as described above, when the object 9 enters between the transmitting antenna 2 and the receiving antenna 3, the transmission signal is reflected by the object 9 and a part thereof is indicated by an arrow A in FIG. Thus, the object 9 is bypassed to reach the receiving antenna 3. Therefore, due to this detour, the phase is delayed, and the received signal is delayed in phase according to the size of the object 9. This phase delay increases as the size of the intruding object 9 increases and the detour distance increases. The relationship between this phase change and the size of the intruding object is clear if measured in advance.For example, when a cat crosses vertically between the transmitting antenna and the receiving antenna, the phase change is about several radians. Yes, when a person crosses vertically, it becomes about several tens of radians, which is easily distinguishable. The phase delay of the received signal is maintained as it is even if it is an intermediate frequency signal.

As a result, by measuring the phase of the intermediate frequency signal with reference to the phase of the reference oscillator, it is possible to know the rate at which the distance traveled is longer than that in the case where the received signal travels in a straight line. The detour distance, and thus the size of the intruding object, can be detected, and the intruding object can be predicted. Moreover, this phase change has nothing to do with the decrease in the output of the microwave oscillator and the sensitivity of the receiver.
Since the influence of the frequency change of the microwave oscillator or the local oscillator is always removed by the PLL circuit, only the change caused by the intruding object can be detected.

As described above, according to the present invention, the size of the object passing between the transmitting antenna and the receiving antenna is detected by the phase change of the received signal, so that the size of the microwave oscillator or the like is reduced. Even if the reception level changes due to a decrease in output, a change with time, a decrease in sensitivity of the receiver, or the like, the size of the intruding object can be accurately grasped regardless of the change. As a result, it is possible to accurately grasp whether a small object such as a dog or a cat has entered or a large object such as a human has entered.

According to the present invention, the size of the intruding object is detected by detecting the phase change of the received signal. In addition to the phase change, the amplitude change of the conventional received signal, that is, the received signal is detected. If the magnitude (strength) of the is also detected, the reliability of the detection can be further improved.
The change in the magnitude of the received signal can be easily known by detecting a part of the output of the intermediate frequency signal IF with a detector and measuring the magnitude thereof, as in the conventional case.

[0025]

According to the present invention, in the case of monitoring the intrusion of a suspicious person or the like in an area of a specific interval such as an intrusion warning device,
Not only the presence or absence of the intruding object, but also the size of the intruding object can be accurately grasped, so that it is possible to recognize the discrimination from an unaffected object such as a dog or a cat, which is extremely reliable. You can be vigilant.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a microwave cutoff sensor according to the present invention.

FIG. 2 is a diagram illustrating an example in which the size of an object is different when an intruding object is detected by microwaves.

[Explanation of symbols]

1 microwave oscillator 2 transmitting antenna 3 receiving antenna 4 Local oscillator 5 mixer 6 Reference oscillator 7 Phase comparator 8 Phase detector

Claims (4)

[Claims] 1. A method for detecting what cuts between the transmission antenna and the reception antenna by facing a transmission antenna and a reception antenna for microwaves, having a reference oscillator oscillating at a constant frequency, By generating an intermediate frequency signal having the same frequency as the reference oscillator by mixing the received signal by the receiving antenna with a local oscillation signal, the phase of the intermediate frequency signal is detected by using the phase of the reference oscillator as a reference. A method for detecting microwave blocking, comprising detecting the size of an object that blocks between the transmitting antenna and the receiving antenna. 2. A PLL for controlling the oscillation frequency of the local oscillator by comparing the phases of the intermediate frequency signal and the reference oscillator in order to match the frequency of the intermediate frequency signal with the oscillation frequency of the reference oscillator. The detection method according to claim 1, which is performed by configuring. 3. A microwave oscillator, a transmitting antenna for transmitting an oscillation output of the microwave oscillator, a receiving antenna provided to face the transmitting antenna and receiving a signal transmitted from the transmitting antenna, An electronically tunable local oscillator for generating an intermediate frequency signal of a reception signal received by a reception antenna, and an intermediate frequency signal by mixing an oscillation signal of the local oscillator and a reception signal received by the reception antenna The mixer, a reference oscillator for generating a signal of a constant frequency, the oscillation frequency of the reference oscillator and the frequency of the intermediate frequency signal generated by the mixer, and the local part so that there is no difference between the two frequencies. A phase comparator for sending a control signal to the oscillator, and a unit for detecting the phase of the intermediate frequency signal generated by the mixer with reference to the phase of the reference oscillator. A microwave cutoff sensor consisting of a phase detector. 4. The microwave cutoff sensor according to claim 3, further comprising a signal strength detector that detects a signal strength of the intermediate frequency signal generated by the mixer.