JP3428531B2 - 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 for detecting a microwave output from a measuring instrument by a modulated wave method or a non-modulated wave (continuous wave) method, and more specifically, a microwave detector. The present invention relates to the improvement of the structure of the discrimination circuit for discriminating whether the generated microwave is a modulated wave or an unmodulated wave.

[0002]

2. Description of the Related Art A microwave detector configured to detect an unmodulated (not pulse-modulated) microwave output from a radar type speed measuring instrument and generate an alarm is conventionally known. For example, in the case of distinguishing a microwave in the frequency band to be detected from other microwaves by the super-heterodyne method, the microwave received by the antenna or the like is subjected to a predetermined frequency mixing process, and then the FM.
The signal is detected by a detection circuit or the like, the signal based on the detected output is subjected to threshold value processing, and when it is equal to or higher than a predetermined threshold value, it is determined that the target microwave is received.

Recently, an H-type velocity measuring device (H system)
A system for intermittently emitting a pulse-modulated microwave (pulse-modulated wave), which is referred to as "," and detecting a predetermined vehicle on the basis thereof is also used as a vehicle speed measuring instrument.

Therefore, there is a need for a microwave detector capable of detecting both types of pulse-modulated and non-modulated microwaves. Furthermore, in a microwave detector of a type that detects both a modulated microwave and a non-modulated microwave, it is necessary to solve the following problems.

In other words, when the received microwave is a microwave based on a modulation method, it is highly likely that it is the target microwave, and since it is an intermittent pulse, the source is already generated when the alarm is issued. It is expected that it will be very close to, and it is necessary to take immediate action.

On the other hand, since the pulse-unmodulated microwave is output not only from the radar type speed measuring device but also from a person detecting device such as an automatic door, there are many microwaves for such an automatic door. When a vehicle is equipped with a radar-type speed measuring device in the city, an alarm is often issued based on microwaves for automatic doors, and alertness to the alarm may be paralyzed or microwaves that are important objectives may be generated. Even if it is detected, the user may be delayed in responding.

Therefore, as a microwave detector for solving such a problem, there is, for example, the invention disclosed in Japanese Patent Laid-Open No. 10-332812. That is, in the case of H wave,
Since radio waves are repeatedly turned on and off in a very short cycle, the radio wave transmission level of the entire transmission source is lower than that of normal waves. In the case of the H wave, the intermediate frequency becomes constant when the received electric field strength exceeds a certain level, and the amplitude of the detection output does not change. However, in the case of the normal wave, it is proportional to the increase of the received electric field strength. Then, the intermediate frequency also changes, and the amplitude of the detection output increases without being saturated. Therefore, FM
The output waveform of the detection circuit has a large amplitude h1 of the detection output signal of the normal wave when the received electric field strength is equal to or higher than a certain level (see FIG. 1).
The amplitude h2 of the H-wave detection output signal becomes smaller (see FIG. 2).

In each figure, (a) is the sweep voltage, (b) is the state of the detection output signal with respect to the sweep voltage, and (c) is the comparator for thresholding the detection output signal. The output of each is shown schematically.
Therefore, by setting a threshold value at a predetermined level between the amplitudes h1 and h2, they can be discriminated from each other.

In accordance with the above principle, the comparator detects the detection signal of the FM detection circuit in the superheterodyne type reception circuit section and compares it with the reference voltage (the level between h1 and h2) to receive the non-reception and the modulated wave. When it does (the comparator output is H), when it receives an unmodulated wave (the comparator output is L), it discriminates. Furthermore, FM
The S meter output of the detection circuit is monitored, and when the modulated wave is received, the S meter output becomes a certain level or higher, and when it is not received, the S meter output is naturally close to 0, and therefore the discrimination is performed.

When the pulse modulation / non-modulation can be discriminated in this manner, it becomes easy for the user to carefully drive the alarm by receiving the pulse-modulated microwave, which requires a prompt response.

[0011]

Although the above-mentioned conventional microwave detector can detect the non-modulated wave and the modulated wave by discriminating them, there is a problem that it is difficult to recognize them in the usage environment. That is, in a general super-heterodyne type microwave detector, the magnitude of the voltage output from the FM detection circuit is subtly changed in DC depending on the use environment (temperature change, etc.). If the amplitude changes due to temperature or the like (because it is not affected by the temperature or the like at the time of reception), the amplitudes h1 and h2 also change, which hinders the comparison with the threshold value.
Then, depending on the usage environment, there may occur a situation where the presence or absence of microwave reception is erroneously determined or not determined. Therefore,
It is necessary to adjust the threshold value by performing temperature compensation.

However, if an attempt is made to perform temperature compensation on the threshold level setting, it becomes difficult to adjust the level setting due to the individual difference of the microwave detector, and further, if this adjustment is not firm, the threshold value is set. The discrimination ability for discriminating whether the microwave exceeding the value belongs to the pulse modulation / non-modulation microwave is deteriorated.

The present invention has been made in view of the above background, and an object of the present invention is to solve the above problems and to detect whether or not a microwave to be detected has been received by the circuit temperature. It is an object of the present invention to provide a simple and inexpensive microwave detector that is hardly affected by changes and has improved accuracy in identifying whether a detected microwave is a modulated or unmodulated microwave.

[0014]

In order to achieve the above object, in a microwave detector according to the present invention, an antenna and a conversion means for converting a reception signal received through the antenna into an intermediate frequency signal are provided. , There is a detection means for detecting a microwave of a target frequency band from the intermediate frequency signal obtained by the conversion means, and a target microwave having a certain level or more based on the detection signal output from the detection means. And a detection means for detecting whether or not to detect whether the detection signal output from the detection means is due to reception of a modulation microwave or non-modulation microwave. An identification means, and an alarm means for outputting an alarm based on the detection signal,
The alarm means is a microwave detector capable of changing the alarm based on the output of the identification means, wherein the detection means includes a first detection system and a second detection system, and the first detection system includes the detection signal. A detection process is performed after passing through a noise removal filter that extracts a signal in a predetermined frequency band from the signal, the second detection system directly performs the detection process on the detected signal, and the identification means is the first detection system. Is configured so that the output of the alarm means can be changed based on whether the detection signal is output from the device and whether the detection signal is output from the second detection system (claim 1).

In this embodiment, the converting means is composed of both mixers 5 and 7, both local oscillators 4 and 6, a sweep control circuit 9 and the like. In addition, although the example of the double heterodyne system is shown in the embodiment, a single super heterodyne system may be used, and various kinds of concrete receiving circuits can be used. Further, the detection means corresponds to the FM detection circuit 8 and the detection means corresponds to the detection circuit 10 in the embodiment. The low-pass filter 20 is used as the noise removal filter in the embodiment, but the present invention is not limited to this, and a band-pass filter that passes only a predetermined low frequency region and other noise such that the received microwave is white noise. It is only necessary to prevent the noise from being buried or the like and to remove or reduce the noise. That is,
Even if it says noise removal, it is not necessary to remove 100%.

According to this structure, when the reception of the microwave to be detected is detected, it is discriminated which of the modulated and non-modulated microwaves exceeds the threshold of the detected microwave as in the conventional case. There is no need. Therefore, even if the output of the detection means slightly changes due to the temperature of the circuit, it is sufficient to set the threshold value so that the detection means can detect the microwave to be detected without affecting it. Fine adjustments for each circuit and microwave detector are not required. In short, as shown in the embodiment,
By identifying the type of microwave received by the AC identification method using the result obtained by processing the demodulation frequency component of the output of the FM detection circuit used as the detection means through the low-pass filter and the result obtained without processing it, By not checking how much the detection output exceeds the threshold value, it is not affected by the fluctuation of the DC component of the signal flowing through the circuit.

Preferably, the identifying means identifies that a non-modulation type microwave has been received when the detection signal is output from both the first detection system and the second detection system. (Claim 2).

Preferably, in addition to the configuration of claim 1 or claim 2, a signal output corresponding to the electric field intensity output from the detection means is acquired, and the signal output is not less than a predetermined magnitude. Then, the detection signal is output only from the first detection system, so that it is determined that the microwave of the modulation method is finally received (claim 3).

When the above structure is added to claim 1,
In the sweep type double super-heterodyne receiving circuit as in the embodiment, when the intermediate frequency signal is FM-detected using the intermediate-frequency amplifier capable of wideband detection, the demodulation frequency component appearing in the FM detection output at the time of the sweep stop is It is possible to effectively use the difference depending on the modulation method of the received radar wave. In other words, for example, an H-type speed measuring device, which is one of the detection targets, turns on / off radio waves at a very short cycle (about 330 kHz) called a kind of pulse modulation.
Since it is a radar wave that repeats FF, unless the low-pass filter is applied to the normal detection output, it is buried in the white noise component and the S-curve characteristic cannot be detected. However, the reception sensitivity of the non-modulated wave decreases even without the low-pass filter. The property of being able to detect the minimum of objects becomes easy to use.

Specifically, the demodulation frequency component that appears in the output of the FM detection circuit when the pulse-modulated wave is received and stopped by sweeping is almost changed because it is buried in the white noise component regardless of the strength of the received electric field strength. On the other hand, when the non-modulated wave is received, since only the carrier is present, the fact that the white noise component changes according to the received electric field strength is used. By doing so, it is possible to easily identify whether the currently received signal belongs to the pulse-modulated wave or the non-modulated wave by the existing inexpensive and simple circuit configuration such as the comparator. .

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a microwave detector according to the present invention will be described below. FIG. 3 is a block circuit diagram showing a main part of such a microwave detector. As shown in the figure, the circuit configuration of this microwave detector is such that, when a predetermined microwave is received, the receiving circuit section 1 that detects the microwave and outputs an alarm, and the receiving circuit section 1 outputs the microwave. A discrimination circuit section 2 is provided for discriminating the type of microwave received based on various signals, that is, whether it is a modulated wave or a non-modulated wave.

The receiving circuit section 1 includes a double superheterodyne type receiving circuit. That is, the reception signal received by the horn antenna 3 and the output of the first local oscillator 4 are frequency-mixed by the first mixer 5. The first intermediate frequency signal thus obtained and the output of the second local oscillator 6 are frequency-mixed by the second mixer 7, and the output is FM
It is input to the detection circuit 8.

Then, in the present embodiment, in order to receive the microwaves of both the X band and the K band, which are the output of the speed measuring device for the purpose of measuring the speed of the vehicle, the first method is adopted.
The conversion is performed so that the frequency of the intermediate frequency signal becomes 1.050 GHz and the frequency of the second intermediate frequency signal becomes 10.7 MHz. In addition, since the frequency of the second intermediate frequency signal is swept within a predetermined range based on the frequency, the second
The local oscillator 6 is configured by using a VCO (voltage controlled oscillator), and based on the control voltage from the sweep control circuit 9, 1.
The sweep is repeated from 0357 to 1.0643 GHz.

The timing of repeating this sweep may be continuous or may be intermittent at regular intervals. Furthermore, when the target microwave is detected, the sweep is temporarily stopped (sweep stop). In addition, the 1st local oscillator 5 used what output the sine wave of the frequency of 11.575 GHz (constant).

The FM detection circuit 8 amplifies and detects the second intermediate frequency signal. When the microwave of the predetermined frequency is not received, there is no output (white noise is output) and the microwave is detected. When received, the demodulation signal S1 showing a predetermined detection characteristic (S curve characteristic) is output to the detection circuit 10.

The detection circuit 10 monitors the output of the FM detection circuit 8 and detects whether or not there is a microwave reception signal during the detection output. When the detection circuit 10 identifies the reception of the microwave to be detected, the alarm circuit 11 is operated and the buzzer 11a is sounded. further,
It also has a function of generating various signals for identifying the type of the detected microwave and sending the signals to the identification circuit unit 2.

The specific structure of the detection circuit 10 is as shown in FIG. 4, and the demodulated signal S1 output from the FM detection circuit 8 is processed by two main and sub signal processing systems. I am trying to do it.

Main first signal processing system (first detection system)
Is a low-pass filter 20 (LPF) that cuts a signal of a predetermined frequency or higher (for example, 70 kHz or higher) from the demodulation signal S1 output from the FM detection circuit 8, and a predetermined waveform shaping to the demodulation signal S1a output through this filter. The first waveform shaping circuit 21a for performing the above and the first pulse detection circuit 22a for detecting whether or not a pulse having a predetermined pulse width or more is output to the first waveform shaping circuit 21a are connected in series. Then, the output of the first pulse detection circuit 22a becomes the first identification signal S2a, which is given to the alarm circuit 11 and the identification circuit unit 2.

The first waveform shaping circuit 21a is an amplifier having an extremely large gain, and makes a full swing of the input signal between positive and negative. This gain is adjusted so that even the white noise at the time of non-reception makes a full swing, and the output of the first waveform shaping circuit 21a becomes a square wave. When the input is white noise, the frequency becomes a dense square wave, and when the target microwave is received, the output of the FM detection circuit 8 has a large amplitude,
The period in which the positive or negative is maintained becomes long, and the pulse width of the pulse output from the first waveform shaping circuit 21a becomes long. Therefore, when the first pulse detection circuit 22a detects a pulse having a certain pulse width or more, it can be determined that the micro wave having the predetermined frequency is received.

On the other hand, the secondary second signal processing system (second detection system) includes a second waveform shaping circuit 21b for performing a predetermined waveform shaping on the demodulated signal S1 output from the FM detection circuit 8,
The second pulse shaping circuit 21b is provided with a second pulse detection circuit 22b for detecting whether or not the pulse width of the pulse output is equal to or longer than a certain time. The second waveform shaping circuit 21b and the second pulse detection circuit 22b can have the same configuration as the first waveform shaping circuit 21a and the first pulse detection circuit 22a, respectively. That is, the second signal processing system has the same circuit configuration as that of the first signal processing system except for the low-pass filter 2.
It is the one without 0. Then, the signal output from the second pulse detection circuit 22b becomes the second identification signal S2b and is provided to the identification circuit unit 2.

On the other hand, the discrimination circuit section 2 receives the received electric field intensity (S meter output) output from the FM detection circuit 8 and the signal detected by the detection circuit 10 (in the present embodiment, the first and second discrimination signals S2a, The type of the received microwave is specified based on (there are two signals of S2b). Then, the received electric field strength is converted into a digital value by the A / D converter 15 and then given to the CPU 18.

The first identification signal S2a is input from the detection circuit 10 to the microcomputer 18, and the second identification signal S2b passes through the determination circuit 19 in the identification circuit section 2 and then the second identification signal S2.
It is input to the microcomputer 18 as b '. The signal level converted into a digital signal through the A / D converter 15 is also given to the microcomputer 18.

By inputting this digital signal to the microcomputer 18, information on the electric field strength of the microwave received by the horn antenna 3 is taken into the microcomputer 18, and the determination circuit 1
When the second identification signal S2b 'and the first identification signal S2a output from 9 are given to the microcomputer 18, based on these identification signals and the electric field strength of the received signal given through the A / D converter 15, A judgment is made as to whether the received microwaves are of the non-modulation type or the modulation type, the judgment result is given to the alarm circuit 11, and the type of alarm is changed according to the difference of the methods. In addition,
The specific determination algorithm will be described later.

The determination circuit 19 to which the second identification signal S2b is input is equipped with a delay timer, and the second identification signal S2.
Even if 2b is input to the identification circuit section 2, the determination circuit 19 does not immediately output a signal to the microcomputer 18. Thereby, even if the second identification signal S2b is output from the second pulse detection circuit 22b due to noise or malfunction, the output of the determination circuit 19 does not change and malfunction is prevented. In other words, the determination circuit 19 sends an output to the microcomputer 18 only when the second pulse detection circuit 22b continuously outputs a predetermined output.

Specifically, the structure is as shown in FIG. As shown in the figure, it has a comparator 19a
The output of the pulse detection circuit 22b is applied to the inverting input terminal of the comparator 19a. The power supply voltage Vc is provided between the inverting input terminal and the second pulse detection circuit 22b.
A resistor R and a capacitor C connected in series between c and ground
The connection points of are connected. The voltage divided by the voltage dividing circuit of the resistors R1 and R2 is applied to the non-inverting input terminal of the comparator 19a as a reference voltage. As a result, when the state in which the second identification signal S2b is turned on continues, the output is inverted with a delay corresponding to the time constant of RC. Further, when the second identification signal S2b is momentarily turned on, the output of the determination circuit 19 is not inverted.

The determination circuit 19 does not necessarily have to have the above-described configuration, and the point is that the determination circuit 19 notifies the microcomputer 18 that the output of the second pulse detection circuit 22b is not continuously input for a predetermined time or more. It suffices if the 2 identification signal S2b 'is not output.

Further, the microcomputer 18 has a function of sending a detection signal to the sweep control circuit 9 when the detection circuit 10 detects the reception of microwaves and stops the sweep for a predetermined time. Further, when the sweep is sent intermittently, the timing signal at the start of the sweep is also sent from the microcomputer 18 to the sweep control circuit 9.

The principle of operation and action, which are the essential parts of the invention of the present embodiment, will be described below. FIG. 6 shows an example of the normal microwave (non-modulated wave) detection output of the non-modulation method, and FIG. 7 shows an example of the modulation method microwave (H wave) detection output. Both waveforms are detection outputs in one sweep for substantially the same received electric field strength, and the ranges of the vertical axis and the horizontal axis are the same.

As is clear from FIG. 6, in the case of the non-modulated wave, the S curve clearly appears. Therefore, the S-curve can be detected regardless of whether or not the low-pass filter is applied. That is, since the positive or negative state continues at the maximum or minimum portion of the S curve, the first and second
A pulse having a predetermined pulse width is output from the waveform shaping circuits 21a and 21b, and the first and second pulse detection circuits 22a and 2b are output.
At 2b, the pulse is detected.

On the other hand, as is apparent from FIG. 7, in the case of the H type, since the ON-OFF of the radio wave is repeated at a very short cycle (about 330 kHz) called a kind of pulse modulation, the detection output is white. It is buried in noise and the S curve does not appear neatly. That is, the detection signal is not output from the second pulse detection circuit 22a.

Then, when this detected output is passed through a low-pass filter, noise components are removed, so that an S curve appears. That is, the detection signal is output from the first pulse detection circuit 22a.

Further, the concrete measurement results are shown in FIG.
~ As shown in FIG. FIG. 8 shows a pulse-modulated (H-wave) of a size (referred to as “level 3” for convenience) in which the microwave detector according to the present embodiment has to practically and reliably detect the microwave to be detected. 2) shows a part of the signal processing performed in each signal processing system of the detection circuit 10 when the microwave of FIG. 3A to 3D are waveforms at the positions indicated by the corresponding symbols in the circuit shown in FIG.

As shown in FIG. 7A, the FM detection circuit 8
Since the demodulated signal S1 which is the output of 1 detects the pulse-modulated microwave which is intermittently received, its output waveform is buried in white noise.

Therefore, when the demodulated signal S1 is input to the secondary second signal processing system without passing through the low-pass filter 20, the second waveform shaping circuit 21b as shown in FIG.
The output of is a dense pulse train as a whole.

On the other hand, as shown in FIG. 6B, the demodulated signal S1 is passed through the low-pass filter 20,
There is a slight difference in level between when microwaves are being received and when microwaves are not being received. Therefore, by causing the first waveform shaping circuit 21a to fully swing the waveform of (b), the state of Low is maintained while the microwave is being detected as shown in FIG. When the pulse width is greater than the pulse width and is not detected, a dense pulse train is output.

On the other hand, when the pulse-unmodulated microwave (normal wave) is received, the waveform at each position of each signal processing system in the detection circuit 10 is as shown in FIG. As is clear from comparison between FIG. 9 and FIG. 8, the output of the FM detection circuit 8 before passing through the low-pass filter 9 ((a) in the same figure) holds High when the microwave is already detected. . Therefore, as shown in FIG. 7D, the low state is maintained even when the second waveform shaping circuit 21b side is also receiving the microwave. Therefore, the pulse can be detected not only by the first pulse detection circuit 22a but also by the second pulse detection circuit 22b.

As shown in FIG. 10, even in the case of a non-modulated normal wave, if the received electric field strength is small, only the signal passed through the low-pass filter 20 as in the modulated wave shown in FIG. That is, only the first signal processing system can detect the reception of microwaves.

The above experimental results are summarized in FIG. That is, in the first signal processing system, which is mainly used, whether the pulse-modulated or non-modulated microwave of an electric field intensity (level 1) is suspected as a true microwave to be detected even if reception is confirmed. Can also be detected with high accuracy. On the other hand, in the secondary second signal processing system, it is possible to detect only the unmodulated microwave of the electric field strength (level 3), which requires practical attention when reception is confirmed in practice. it can.

Therefore, when the microwave to be detected is received, the microcomputer 18 confirms the combination of the first and second identification signals S2a and S2b input from the detection circuit 10 to the identification circuit section 2, so that sufficient attention can be paid. It becomes possible to easily identify pulse modulation / non-modulation for a microwave having an electric field strength (level 3) that requires the above.

Therefore, in this embodiment, when the microwave is detected by the first signal processing system, the alarm is issued. As a result, the reception of microwaves can be reliably notified. Further, when the S meter output (reception electric field strength) is equal to or higher than a certain level and the detection signal is output from the second signal processing system by the AND function in the CPU 18,
The modulated wave detection signal is output to the alarm circuit 11.
Receiving this, the alarm circuit 11 switches to an alarm for modulated waves.

In the above-described embodiment, when the microwave reception is detected by the first signal processing system, that is, the detection processing based on the signal passed through the low-pass filter,
I want to output an alarm regardless of its type, and then
When the modulation / non-modulation can be discriminated, the type of alarm is switched according to need. However, the present invention is not limited to this, and the detection result of the first and second signal processing systems can be changed to CP.
It may be provided to a determination means such as U, and the corresponding alarm alarm may be output after the presence / absence of microwave reception and the type of microwave reception are identified.

[0052]

As described above, in the microwave detector according to the present invention, by configuring as in claim 1, the detection target of the modulation method and the non-modulation method is not affected by the temperature change of the circuit. The microwave can be detected accurately and the alarm can be divided according to the type of microwave. That is, since the determination is not based on the DC component as in the conventional case, it is not necessary to adjust the threshold value with high precision, and it is not necessary to finely adjust the threshold value with the temperature change of the circuit.

According to the second aspect or the third aspect, it is possible to discriminate whether the microwave currently received from the output of the detection circuit is the microwave based on the modulation system or the microwave based on the non-modulation system. Therefore, the alarm can be accurately divided by the identification. Further, the structure of the detecting means configured to obtain these effects is not particularly complicated as compared with the structure of the conventional microwave detector, and only a part of the known circuit structure is added, so that the microwave can be easily manufactured and is inexpensive. It becomes a detector.

[Brief description of drawings]

FIG. 1 is a waveform diagram showing how signal processing is performed when a conventional microwave detector receives a non-modulation type microwave.

FIG. 2 is a waveform diagram showing how signal processing is performed when a pulse modulation type microwave is received by a conventional microwave detector.

FIG. 3 is a block circuit diagram showing a main part of an embodiment of a microwave detector according to the present invention.

FIG. 4 is a circuit diagram for explaining a configuration of a detection circuit in the embodiment of the microwave detector according to the present invention.

FIG. 5 is a circuit diagram for explaining the configuration of the determination circuit in the embodiment of the microwave detector according to the present invention.

FIG. 6 is a waveform diagram showing an example of a detection signal of an unmodulated wave.

FIG. 7 is a waveform diagram showing an example of a detection signal of a modulated wave.

FIG. 8 is a diagram showing the waveform of each part in the detection circuit when the embodiment of the microwave detector according to the present invention receives a modulated wave having a large electric field strength.

FIG. 9 is a diagram showing a waveform of each part in the detection circuit when the embodiment of the microwave detector according to the present invention receives an unmodulated wave having a large electric field strength.

FIG. 10 is a diagram showing a waveform of each part in the detection circuit when the embodiment of the microwave detector according to the present invention receives an unmodulated wave having a small electric field strength.

FIG. 11 is a diagram for explaining types of microwaves that can be discriminated by the detection circuit in the embodiment of the microwave detector according to the present invention.

[Explanation of symbols]

3 horn antenna (antenna) 4 First local oscillator (conversion means) 5 First mixer (conversion means) 6 Second local oscillator (conversion means) 7 Second mixer (conversion means) 8 FM detection circuit (detection means) 9 Sweep control circuit (conversion means) 10 Detection circuit (detection means) 11 Alarm circuit (alarm means) 18 Microcomputer (identification means) 20 Low-pass filter (detection means, first detection system) 21a First waveform shaping circuit (detection means, first detection system) 21b Second waveform shaping circuit (detection means, second detection system) 22a First pulse detection circuit (detection means, first detection system) 22b Second pulse detection circuit (detection means, second detection system)

─────────────────────────────────────────────────── --- Continuation of the front page (56) References JP-A 63-5285 (JP, A) JP-A 5-291978 (JP, A) JP-A 11-160417 (JP, A) JP-A 7- 35845 (JP, A) JP 63-8575 (JP, A) JP 4-40387 (JP, A) JP 5-7666 (JP, B2) JP 3326363 (JP, B2) JP 3329744 (JP , B2) Patent 2503344 (JP, B2) (58) Fields investigated (Int.Cl. ⁷ , DB name) G01S ⁷ /00-7/42 G01S 13/00-13/95 G01R 29/08

Claims (3)

(57) [Claims] 1. An antenna, a conversion means for converting a reception signal received through the antenna into an intermediate frequency signal, and a microwave in a target frequency band is detected from the intermediate frequency signal obtained by the conversion means. Detection means, detection means for detecting whether or not a target microwave of a certain level or higher is present based on the detection signal output from the detection means, and the detection signal output from the detection means is a modulation method. And an alarming means for outputting an alarm based on the detection signal, and an alarming means for outputting an alarm based on the detection signal. Is a microwave detector capable of changing the alarm based on the output of the identification means, wherein the detection means includes a first detection system and a second detection system, The output system performs detection processing after passing through a noise removal filter that extracts a signal in a predetermined frequency band from the detected signal, the second detection system directly performs detection processing on the detected signal, and the identification means is A microwave detector, wherein the output of the alarm means can be changed based on whether the detection signals of the first detection system and the second detection system are output. 2. The identifying means identifies that a non-modulation type microwave is received when the detection signal is output from both the first detection system and the second detection system. The microwave detector according to claim 1. 3. A signal output according to the electric field intensity output from the detection means is acquired, and the signal output is not less than a predetermined level, and the detection signal is output only from the first detection system. The microwave detector according to claim 1 or 2, characterized in that it is finally determined that a modulation type microwave is received.