JP3326363B2 - Microwave detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a microwave detector, and more specifically, to a microwave detector which emits a microwave from a measuring instrument or the like using either a modulated wave system or an unmodulated wave (continuous wave) system. A microwave detector capable of receiving, a microwave detector having a function capable of discriminating which type of received microwave is emitted, and particularly a sweep type microwave. It relates to what is suitable for the detector.

[0002]

2. Description of the Related Art There has been conventionally known a microwave detector configured to detect a microwave emitted from a radar type speed measuring device and generate an alarm. In the case of a general traffic monitoring radar speed meter,
Microwaves in any of 10 GHz band (X band), 24 GHz band (K band), and 35 GHz band (Ka band) are used.

A microwave detector for detecting microwaves from this type of speed measuring device receives microwaves of each band by a superheterodyne receiving circuit, and the electric field strength of the received microwaves is constant. If the level is higher than the level, the target microwave is determined, and an alarm such as an alarm is output. The microwave conventionally used is an unmodulated continuous wave.

Recently, a system for intermittently emitting a pulse-modulated microwave (pulse-modulated wave) called an H-type speed measuring device (H system) and detecting a predetermined vehicle based on the intermittently emitted microwave has been proposed. There is also.

Therefore, in order to detect a target microwave, it is necessary to detect both a modulated microwave and an unmodulated microwave. By using a superheterodyne receiving circuit for detection and adjusting a threshold value for discriminating whether or not a target microwave is received, a pulse-modulated wave can be detected as it is.

[0006]

As described above, in the conventional microwave detector, a constant electric field intensity is maintained in a target frequency band regardless of whether the microwave is a modulation system or a non-modulation system. When the above-mentioned microwaves are present, they can be detected, but it cannot be discriminated whether or not they are based on the non-modulation method.

On the other hand, there are various types of measuring instruments that emit microwaves other than those described above. For example, there is a device for detecting a person at an automatic door. The frequency of the microwave used in such an apparatus is also in the X band described above.
As a result, conventionally, even if a microwave in a target frequency band is detected, whether or not it is a true target microwave such as an automatic door is discriminated based only on a received signal. I couldn't.

Accordingly, when a microwave in a target frequency band is detected, an alarm is issued. For example, while traveling in a city where a large number of microwaves for automatic doors are present, the target microwave is used. Often, alarms are issued based on microwaves for the automatic doors other than the above, and there is a risk that attention to the alarm may be paralyzed. Response may be delayed.

Therefore, the present inventor has proposed that a microwave for an automatic door uses a non-modulation type microwave, and that a target microwave uses both a modulation type and a non-modulation type. We focused on the current situation where many things are being used. That is, if the received microwave is a modulation method, it can be said that it is a target microwave. When the microwave is of a non-modulation type, there is a high possibility that the microwave is used for an automatic door or the like, but it can be said that the possibility of the intended microwave remains.

Therefore, if it is possible to discriminate whether a received microwave is based on a modulation method or a non-modulation method,
The reliability of the output alarm is increased. In addition, in the case of the modulation method, it is difficult to receive the signal due to the nature of the radio wave, and since the microwave is emitted intermittently, the vehicle travels even during the stop zone, so the reception of the modulation method microwave is not possible. In such a case, there is a possibility that the transmission source is already approaching, and it is necessary to take immediate action. Modulation /
It is preferable that the non-modulation method can be identified, and the performance of the microwave detector is improved.

SUMMARY OF THE INVENTION The present invention has been made in view of the above background, and an object of the present invention is to solve the above-described problem and to use a simple configuration to control whether a currently received signal is modulated or non-modulated. It is intended to provide a microwave detector capable of accurately discriminating whether or not the light is emitted by the method described above.

[0012]

In order to achieve the above object, in a microwave detector according to the present invention, a conversion means for converting a reception signal received via an antenna into an intermediate frequency signal, and the conversion means Detecting means for detecting a microwave in a target frequency band from the obtained intermediate frequency signal, and detecting means for determining that the target microwave having a predetermined level or more exists based on a detection signal output from the detecting means It is assumed that the microwave detector includes an alarm unit that outputs an alarm based on a detection signal output from the detection unit. And a detection unit that obtains a detection signal output from the detection unit, and compares the detection signal with a reference value .
It is smaller than the microwave detection output and
A signal identification circuit for setting a predetermined value larger than the detection output of the chromatic wave and discriminating whether the currently received microwave is based on the modulation method or the non-modulation method based on the output of the comparing means. (Claim 1).

Here, in the embodiment, the conversion means is constituted by both mixers 13 and 15, both local oscillators 12 and 14, a sweep control circuit 17, and the like. In the embodiment, the example of the double superheterodyne system has been described. However, a single superheterodyne system may be used, and various specific receiving circuits can be used. Further, the detecting means corresponds to the FM detecting circuit 16 in the embodiment, and the detecting means corresponds to the pulse detecting circuit 18. Further, the alarm means is realized by the alarm circuit 19 and the buzzer 19a. Further, the comparison means, which is a main configuration of the present invention, corresponds to the comparator 23 in the embodiment.

According to the present invention, for the unmodulated wave and the modulated wave,
Even with the same electric field intensity, the former has a higher detection output (because it does not saturate). Therefore, by comparing the detected signal with the reference value by the comparing means, it is possible to determine whether the received microwave is of the modulation method or of the non-modulation method. And to identify more reliably,
The configuration is as follows.

That is, when the output of the comparing means is continuously output as ON, the signal discriminating circuit judges the detected microwave to be of the non-modulation type (in the embodiment, the judging circuit 25). ) May be further provided (claim 2). That is, the output of the comparison means may change sporadically due to noise or other effects. However, if the output is based on a microwave reception signal, the pulse is periodically turned on continuously. Therefore, O
An object that has just reached N is determined not to be a target object, thereby suppressing erroneous determination. It should be noted that “continuously ON” does not mean that the ON state is continued, but that the state in which the pulse is ON within a certain predetermined period continues, and the period during which the pulse is ON is not necessarily constant.

[0016] The reference value to be given to the comparisons means comprises a predetermined level which can discriminate a modulation scheme and a non-modulation method only in the microwave receiver, the microwave non-reception level changes the discriminating operation of said reference value It is better not to do this (claim 3). In the embodiment, this is realized by the reference voltage generation circuit 24 that changes the reference voltage based on the received signal. By doing so, it is possible to make a determination only when microwaves are being received, and it is possible to minimize erroneous determination based on useless information.

Further, a signal output corresponding to the electric field intensity output from the detection means is obtained, and a final modulation method is determined based on the signal output and a determination result obtained based on the comparison means. The non-modulation method may be identified (claim 4). In the embodiment, the CPU 22 performs such identification.

In each of the above-described configurations, the alarm means issues a plurality of types of alarms, and the type of alarm differs depending on whether a result of identification by the signal identification circuit is a modulation method or a non-modulation method. (Claim 5). That is, in the case of the modulation method, it can be determined that the target microwave is used. In the case of the non-modulation method, it can be determined that the target microwave is not often used. Therefore,
By making the alarm different according to the possibility of the intended microwave, appropriate information can be given to the driver and the like, and the driver can take a smooth action based on the information. In addition, even if alarms are frequently generated based on unintended microwaves, the driver can be prevented from paralyzing to the alarms as much as possible.

[0019]

FIG. 1 shows a preferred embodiment of the present invention. As shown in FIG. 1, the circuit configuration of the microwave detector is divided into a receiving circuit section 10 and an identification circuit section 20, which will be described in detail below.

The receiving circuit section 10 includes a double superheterodyne receiving circuit. That is, the frequency of the reception signal received by the horn antenna 11 and the output of the first local oscillator 12 are mixed by the first mixer 13.
The first intermediate frequency signal thus obtained and the output of the second local oscillator 14 are frequency-mixed by the second mixer 15,
The output is input to the FM detection circuit 16. In the present embodiment, in order to receive both the X band and the K band, conversion is performed so that the frequency of the first intermediate frequency signal becomes 1.050 GHz and the frequency of the second intermediate frequency signal becomes 10.7 MHz. . In addition, the frequency of the second intermediate frequency signal sweeps within a predetermined range based on the frequency. Therefore, the first local oscillator 12 has a frequency of 11.575 GHz.
A device that outputs a sine wave having a frequency of z (constant) is used.
The second local oscillator 14 is configured using a VCO (Voltage Controlled Oscillator), and repeatedly sweeps from 1.0357 to 1.0643 GHz based on the control voltage from the sweep control circuit 17. The timing of repetition may be continuous or may be intermittently performed at regular intervals. Further, when a target microwave is detected, the sweep is temporarily stopped (sweep stop).

The FM detection circuit 16 amplifies and detects the second intermediate frequency signal. When the microwave of a predetermined frequency is not received, there is no output (white noise is output). When a microwave is received, a predetermined detection characteristic (S-curve characteristic) is output.

The pulse detection circuit 18 monitors the output of the FM detection circuit 16 and discriminates whether a microwave reception signal is present in the detection output. Specifically, for example, it can be constituted by a comparator or the like. The output of the FM detection circuit 16 is controlled by a threshold, and when the output is equal to or higher than the threshold, the pulse is turned ON, and it is determined that the microwave is detected. You can do so. In response to the pulse ON, the alarm circuit 19 is operated, and the buzzer 19a sounds. The configuration of the receiving circuit unit 10 is a conventionally known configuration.

The discriminating circuit section 20 first includes the FM detecting circuit 16
The S meter output (signal level output) is supplied to the CPU 22 via the A / D converter 21. As a result, the information on the electric field strength of the received signal becomes CP
It is taken in by U22.

The detection output of the FM detection circuit 16 is applied to one non-inverting input terminal of the comparator 23. A reference voltage generating circuit 24 is connected to an inverting input terminal of the comparator 23. Thus, the comparator 23 compares the reference voltage generated by the reference voltage generation circuit 24 with the detection output. And
When the detection output is higher than the reference voltage, the output becomes H. Further, the output of the comparator 23 is provided to the determination circuit 25.

The determination circuit 25 has a delay timer so that the output of the determination circuit 25 is not inverted immediately after the output of the comparator 23 falls from H to L. Thus, even if the output of the comparator 23 falls to L one-time due to noise or malfunction, the output of the determination circuit 25 does not change, thereby preventing malfunction. In other words, when the output of the comparator 23 continuously becomes L, the output of the determination circuit 25 determines.

The output of the determination circuit 25 is
The CPU 22 determines whether the received microwave is of the non-modulation type or the modulation type based on the output of the determination circuit 25 and the electric field strength of the reception signal supplied through the A / D converter 21. Judge whether it is due to
The result of the determination is given to the alarm circuit 19, and the type of alarm is changed according to the difference in the method.

Further, in this embodiment, the output of the pulse detection circuit 18 is supplied to the reference voltage generation circuit 24 and the CPU 22. That is, the reference voltage generating circuit 24 includes two resistors R1 and R2 for dividing the power supply voltage Vcc.
And a switch S connected in parallel to the ground-side resistor R2. The switch S is opened and closed based on the output signal of the pulse detection circuit 18. That is, when the output of the pulse detection circuit 18 is ON (microwave reception), the switch S is opened to apply a divided voltage as the reference voltage (threshold) of the comparator 23, and the output of the pulse detection circuit 18 is turned OFF ( In the case of no microwave, the switch S is closed, the resistor R2 is short-circuited, and the reference voltage of the comparator 23 is set to 0. The reason why the reference voltage is set to 0 is that the presence or absence of a signal is determined based on the lower peak of the detection signal, and conversely, the presence or absence of the signal is determined based on the upper peak. In such a case, for example, a switch S is attached in parallel with the resistor R1, and when no signal is received, the reference voltage is set to the power supply voltage.

The CPU 22 includes a pulse detection circuit 18
When the output is ON (microwave reception), a detection signal is sent to the sweep control circuit 17 to stop the sweep for a certain time. Further, when the sweep is intermittently transmitted, the timing signal at the start of the sweep is also set to C.
The signal is sent from the PU 22 to the sweep control circuit 17.

On the other hand, the internal structure of the decision circuit 25 is as shown in FIG. As shown in FIG.
a, and the output of the comparator 23 serving as the comparison means is supplied to the inverting input terminal of the comparator 25a. And, between this inverting input terminal and the comparator 23,
A connection point between the resistor R3 and the capacitor C connected in series between the power supply voltage and the ground is connected. Also, the comparator 25a
, A voltage divided by a voltage dividing circuit of resistors R4 and R5 is supplied as a reference voltage.

By appropriately setting the resistance ratio of the resistors R4 and R5, the output of the comparator 23 becomes H
, The output of the comparator 25a (judgment circuit 25) becomes L, and when the output of the comparator 23 becomes L, the comparator 25a
The output of (judgment circuit 25) becomes H. Further, in this embodiment, the capacitor C is connected between the input terminal of the comparator 25a and the ground.
Therefore, even if the comparator 23 falls to L, the terminal voltage of the capacitor C does not immediately become lower than the reference voltage formed by the resistors R4 and R5, and operates as follows.

That is, when the output of the comparator 23 is H, the capacitor C is charged. And the comparator 23
Falls to L, the capacitor C is discharged via the output terminal side of the comparator 23. And the capacitor C
, The output of the comparator 25a is inverted to H only after a predetermined amount of discharge. Then, as described later, even if a predetermined microwave is received, the output of the comparator 23 does not hold L, but falls to L for a very short time, and returns to H immediately thereafter. The capacitor C is not sufficiently discharged only when the output of the comparator 23 drops to L, so that the output of the determination circuit 25 does not reverse. Further, even if the output of the comparator 23 once drops to L for some reason and is discharged by a predetermined amount from the capacitor C, if the output of the comparator 23 subsequently holds H, the capacitor C
To return to the original fully charged state. Therefore,
The output of the determination circuit 25 is inverted to H for the first time when the output of the comparator 23 repeatedly falls to L within a certain period of time.

Further, in the present embodiment, the alarm circuit 19
Can output multiple types of alarms.
The alarm is switched according to a control signal based on the identification result given from U22. In other words, both are the same in that the buzzer 19a sounds, but by changing the volume or the frequency, it is possible to switch between the normal alarm and the emergency alarm.

Next, the operation principle and operation of the present embodiment will be described while giving a more detailed description of each of the above-described components. FIG. 3 shows an example of a detection output of a normal microwave (normal wave) of a non-modulation method, and FIG. 4 shows an example of a detection output of a microwave (H wave) of a modulation method. Both waveforms are detection outputs in one sweep for almost the same received electric field strength, and the ranges on the vertical and horizontal axes are the same.

In the case of the H wave, since the ON / OFF of the radio wave is repeated at a very short cycle, the entire radio wave oscillation level of the oscillation source is lower than that of the normal wave. In the case of the H wave, the intermediate frequency becomes constant when the reception electric field strength exceeds a certain level, and the amplitude of the detection output does not change.
In the case of a normal wave, the intermediate frequency changes in proportion to the increase in the received electric field strength, and the amplitude of the detection output increases without being saturated. Therefore, as is clear from both figures,
In the output waveform of the FM detection circuit, the amplitude of the detection output signal of the normal wave is large and the amplitude of the detection output signal of the H wave is small when the received electric field strength is equal to or more than a certain value.

FIG. 5 (normal wave) and FIG. 6 (H wave) respectively show the states of the detection output signal and the predetermined signal in the circuit. In addition, alphabets described in circles in the respective figures indicate signals at corresponding reference numerals described in FIG. As shown in FIG.
In the case of the normal wave, the step h1 at the time of the sweep stop saturates at a certain level (about 2 V), and the portion for outputting the reception signal extends downward in proportion to the reception electric field intensity. On the other hand, as shown in FIG. 6, in the case of the H wave, the step h2 at the time of the sweep stop is reduced by only about 1 V due to the modulation, and even if the received electric field strength increases, as in the case of the normal wave. It does not go down significantly.

Accordingly, the step h at the time of the sweep stop is obtained.
By setting the threshold to a predetermined level between 1 and h2, both can be distinguished. Further, both can be discriminated based on the size of the portion for outputting the received signal (the portion extending further below the step at the time of the sweep stop).

In this embodiment, since the lower peak of the detection output is detected, the output of the pulse detection circuit 18 becomes H in a steady state as shown in FIG. , Microwave (lower peak that outputs received signal)
Is detected, it becomes lower than the reference value, so that the output operates to fall to L.

* In the case of a normal wave, as shown in FIG.
The sweep is performed within a predetermined frequency range while the sweep stop is performed as shown by. Then, when a normal wave is received, the detection output signal output from the FM detection circuit 16 has a signal waveform as shown in FIG. On the other hand, the output of the reference voltage generation circuit 24 has a reference voltage of 0 V ((B) in FIG. 7) because the switch S is closed when there is no reception signal.

When the lower peak (received signal) of the detection signal is detected by the pulse detection circuit 18, the output of the pulse detection circuit 18 becomes L, the switch S is opened, and the output of the reference voltage generation circuit 24 becomes And the power supply voltage Vcc to the resistor R
A predetermined value obtained by dividing the pressure by R1 and R2 is output. Therefore, as shown in FIG. 7B, the reference voltage applied to the comparator 23 is normally 0 V, and a predetermined level of voltage is applied only when microwaves are being received.

Therefore, when a microwave of a predetermined level and frequency is not received, the reference voltage is 0 V, so that F
The output of the comparator 23 becomes H regardless of the output of the M detection circuit 16. As described above, when the microwave is not detected, the reference voltage is set to 0 V so that the determination is not performed, thereby preventing erroneous detection.

When a microwave is detected, the amplitude of a normal wave is large.
It exceeds the threshold value and becomes lower than the reference voltage. Therefore, the output of the comparator 23 falls to L. Since the output is H in the steady state, it is assumed that the output of the comparator serving as the comparison means is turned ON. Therefore, in the case of a normal wave,
While the normal wave is detected and the reception signal is being output, L
(ON), and the output is such that the other sections become H. However, the voltage at the output terminal of the comparator 23 does not immediately drop to L (0 V) because the capacitor C of the determination circuit 25 is provided at the subsequent stage as described above.
As shown in FIG. 7 (C), each time a received signal is output, the operation is performed so that the voltage drops stepwise.

On the other hand, the output of the comparator 23 is given to the decision circuit 25, and as described above, the output of the decision circuit 25 is basically the reverse of the output of the comparator 23, so that the decision circuit shown in FIG. 25 outputs (D)
Is L when no microwave is received. When the normal wave is received, the output (C) of the comparator 23 drops stepwise. Therefore, when this voltage becomes equal to or lower than the reference voltage of the comparator 25a in the determination circuit 25, the output of the determination circuit 25 is inverted to H for the first time. I do.

* In the case of H wave As shown in FIG. 9, when the H wave is not received, as in the case of the normal wave, the reference voltage is 0V.
3 becomes H, so that the output (D) of the decision circuit 25
Remains at L. When the microwave is received, the reference voltage (B) of the comparator 23 becomes a predetermined level. However, in the case of the H wave, the detection output (A) is small and does not drop below the threshold value. Therefore, the comparator output 23 is maintained at H regardless of the presence or absence of reception. Therefore, the output (D) of the determination circuit 25 is also kept at L.

As described above, the output (L
/ H), it is possible to discriminate whether the microwave being received is a modulation method or a non-modulation method. Further, an approximate determination can be made also from the output of the comparator 23.

* Final judgment by CPU 22 Since the output of the judgment circuit 25 becomes L when the H wave is received and when it is not receiving the microwave, the output of the judgment circuit 25 alone is H Incoming waves cannot be distinguished from non-receiving waves. That is, it cannot detect that the H wave is being received.

On the other hand, as shown in FIG. 10, when an S-meter output (G) of the FM detection circuit 16 receives a microwave, it changes according to the magnitude of the electric field intensity. That is,
When a microwave is not received, the level is a small level corresponding to white noise. Therefore, in order to determine whether a microwave of a predetermined intensity is received, a predetermined threshold value is set, and a threshold value and an S meter are set. By comparing with the output, it can be determined that the microwave is being received if the output is equal to or more than the threshold value.

In this embodiment, the CPU 22 acquires a value (digital value) corresponding to the output of the S meter and the output of the determination circuit 25, and the output of the S meter is equal to or higher than a certain level,
At the time of output from the determination circuit 25, it is determined that the H wave is being received, and a control signal is supplied to the alarm circuit 19. When receiving the control signal, the alarm circuit 19 issues an emergency alarm to notify the driver of the presence of the target microwave and to immediately take a predetermined process. In addition, when it is not the H wave, a normal warning is output to call attention to the driver.

The types of alarms are not limited to those that use one device as in the above-described embodiment and change the sound emitted from the buzzer, but include voice and light (LED).
Etc.), different devices can be prepared and the devices can be switched as appropriate, and various measures can be taken.

In the above embodiment, the CPU 2
2, a control signal is output when an H wave (modulated wave) is detected, but the present invention is not limited to this.
For example, the output of the determination circuit 25 may be provided to the alarm circuit 19 directly or via a predetermined circuit, and the operation of the alarm circuit 19 may be controlled by the output of the determination circuit.

In other words, as described above, the output of the determination circuit 25 cannot discriminate between reception of the H wave and non-reception of the signal, but it is determined that the normal wave (unmodulated wave) having a certain size is being received. it can. When a microwave is detected from the pulse detection circuit 18, a predetermined detection signal (pulse ON) is given to the alarm circuit 19.

Therefore, the state of the received signal can be identified from the outputs of the two circuits 18 and 25 as follows.

[0052]

[Table 1] Therefore, the alarm circuit 19 outputs an emergency alarm when there is a pulse detection signal and the output of the determination circuit is L, and outputs a normal alarm when the output of the determination circuit is H with the detection signal. Is also good.

[0053]

As described above, in the microwave detector according to the present invention, by appropriately combining the comparing means and other simple circuit components, the received signal currently being received can be modulated / unmodulated with a simple configuration. It is possible to accurately identify which method is used.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a preferred embodiment of a microwave detection circuit according to the present invention.

FIG. 2 is a diagram showing an internal structure of a determination circuit.

FIG. 3 is a waveform diagram showing an example of a detection signal of an unmodulated wave.

FIG. 4 is a waveform diagram illustrating an example of a detection signal of a modulated wave.

FIG. 5 is a diagram illustrating the timing of each waveform of an unmodulated wave.

FIG. 6 is a diagram illustrating the timing of each waveform of a modulated wave.

FIG. 7 is a diagram (part 1) illustrating an operation based on an unmodulated wave (normal wave).

FIG. 8 is a diagram (part 2) illustrating an operation based on an unmodulated wave (normal wave).

FIG. 9 is a diagram illustrating an operation based on a modulated wave (H wave).

FIG. 10 is a diagram illustrating an example of an S-meter output.

[Explanation of symbols]

 Reference Signs List 10 receiving circuit unit 11 horn antenna 12 first local oscillator 13 first mixer 14 second local oscillator 15 second mixer 16 FM detection circuit 17 sweep control circuit 18 pulse detection circuit 19 alarm circuit 19a buzzer 20 identification circuit unit 21 A / D Converter 22 CPU 23 Comparator 24 Reference voltage generation circuit 25 Judgment circuit

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01S ⁷ /00-7/42 G01S 13/00-13/95 G01R 29/08

Claims (5)

(57) [Claims] A converting means for converting a received signal received via an antenna into an intermediate frequency signal; a detecting means for detecting a microwave in a target frequency band from the intermediate frequency signal obtained by the converting means; Detecting means for determining whether or not a target microwave having a predetermined level or more exists based on a detection signal output from the detecting means, and an alarm for outputting an alarm based on the detection signal output from the detecting means in the microwave detector and means to obtain a detection signal output from said detecting means, further comprising a comparing means for comparing the detection signal with a reference value, the
The reference value is smaller than the unmodulated microwave detection output.
Higher than the detection output of the modulated wave microwave
The microwave further comprising a signal identification circuit for setting a predetermined value and discriminating, based on an output of the comparing means, whether the currently received microwave is based on a modulation method or a non-modulation method. Detector. 2. The signal discriminating circuit further comprises a judging means for judging that the detected microwave is of a non-modulation type when the output of the comparing means is continuously output as ON. The microwave detector according to claim 1. 3. The reference value given to the comparing means is a predetermined level at which a modulation method and a non-modulation method can be discriminated only during microwave reception, and the level of the reference value is changed and no discrimination operation is performed during microwave non-reception. The microwave detector according to claim 1, wherein: 4. A signal output corresponding to an electric field intensity output from the detection means is obtained, and a final modulation method is determined based on the signal output and a determination result obtained based on the comparison means. 4. A method according to claim 1, wherein the modulation method is identified.
The microwave detector according to any one of claims 1 to 4. 5. The alarm device according to claim 1, wherein a plurality of types of alarms are issued, and the type of the alarm is changed depending on whether the identification result of the signal identification circuit is a modulation system or a non-modulation system. The microwave detector according to any one of claims 1 to 4.