JP2018179634A - Drone detection system and method for detecting drone - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a drone detection system and a method for detecting a drone that can accurately detect a flying drone.SOLUTION: A drone detection system 10 detects a drone 91 on the basis of whether a received reception wave includes a reflection wave that Doppler-shifted vertically to the frequency of a search wave. The drone detection system can thus distinguish the drone 91 from swinging trees, electric wires, or flying birds and can detect the drone 91 without fail.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a drone detection system and a drone detection method for detecting a drone flying with a propeller.

  In recent years, small-sized drone flying with a propeller has rapidly spread, and along with it, many drone flying prohibited areas have been provided by ordinances, decrees, etc. (see, for example, Patent Document 1).

JP 2017-052389 (FIG. 1)

  However, since the drone is smaller than an airplane or a helicopter, it can not be accurately detected by the radar, and it is difficult to monitor whether the drone has entered a no-fly area.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a drone detection system and a drone detection method capable of accurately detecting a drone in flight.

  The invention according to claim 1 made to achieve the above object is a drone detection system for detecting a drone flying with a propeller, wherein the frequency includes a reflected wave of a search wave transmitted from a transmission device. A receiving apparatus for receiving a band wave as a receiving wave, and whether or not the receiving wave includes reflected waves of first and second frequencies which are Doppler-shifted up and down with respect to the frequency of the search wave It is a drone detection system which has a judgment part which judges.

  The invention of claim 2 includes a plurality of transmission devices for transmitting the search wave, and a synchronization control unit for controlling the plurality of transmission devices to transmit the search waves synchronized with each other. It is a drone detection system given in 1.

  The invention according to claim 3 is that the search wave is intermittently transmitted from the transmission device, and the received wave is sampled and held every predetermined period, and is taken into the determination unit. The drone detection system according to claim 1, comprising:

  The invention according to claim 4 is the drone detection system according to claim 3, wherein a carrier wave forming a pulse wave intermittently transmitted from a radar transmitter as the transmission device is used as the search wave.

  The invention according to claim 5 includes a spectrum operation unit for calculating the frequency spectrum of the received wave, and the determination unit has a spectrum intensity equal to or greater than a predetermined reference value in the frequency spectrum, and the search wave The waves of two frequencies shifted by the same shift amount within a predetermined tolerance above and below the frequency are determined as the reflected waves of the first and second frequencies. A drone detection system according to any one of the claims 1 to 4.

  The invention according to claim 6 has an image rejection mixer for mixing the local wave having the same frequency as the search wave and the reception wave, and an intermediate wave based on the reception wave on the higher frequency side than the search wave, and the search wave 6. The drone detection system according to claim 5, further comprising: a signal processing unit that divides into an intermediate wave based on a reception wave on a lower frequency side and applies the intermediate wave to the spectrum calculation unit.

  The invention according to claim 7 comprises a mixer for mixing the local wave shifted from the frequency of the search wave by the shift amount of the frequency due to the Doppler shift and the reception wave, and the reflection of the first and second frequencies. The drone detection system according to claim 5, further comprising: a signal processing unit that applies, to the spectrum calculation unit, an intermediate wave that may also include a wave.

  The invention according to claim 8 is a phase adjuster for changing the phase of the received wave or the local wave, and a phase at or near a phase at which the change of the beat of the intermediate wave becomes maximum with respect to the change of the phase. 8. The drone detection system according to claim 6, further comprising: a phase control unit configured to control the phase adjuster such that the phase of the received wave or the local wave is fixed to the calculated phase. .

  The invention of claim 9 further comprises noise removing means for storing the frequency spectrum of the received wave received in advance without a drone as a noise spectrum and subtracting the noise spectrum from the frequency spectrum of the received wave. 8. A drone detection system according to any one of the preceding claims.

  The invention according to claim 10 is a drone detection method for detecting a drone flying with a propeller, wherein a reflected wave of a search wave transmitted from a transmission apparatus is raised and lowered with respect to the frequency of the search wave. It is a drone detection method which judges the existence of the said drone based on whether the reflected wave of the 1st and 2nd frequency which carried out Doppler shift was contained.

  The invention according to claim 11 is the drone detection method according to claim 10, wherein a plurality of transmission devices are disposed apart from one another and the search waves synchronized with each other are transmitted from the transmission devices.

  When the search wave transmitted from the transmission device is reflected by the rotating propeller of the drone and received by the reception device, the reflected wave reflected by the propeller rotating to the side closer to the reception device is The Doppler wave is shifted to the side where the frequency is higher than the search wave, and the reflected wave reflected by the propeller rotating in the direction away from the wave receiving device is Doppler shifted to the side where the frequency is lower than the search wave. On the other hand, in the drone detection system and the drone detection method according to claims 1 and 10, the received wave includes reflected waves of the first and second frequencies which are Doppler-shifted up and down with respect to the frequency of the search wave. Since the presence or absence of the drone is determined based on whether or not the drone is present, the drone and the others can be clearly distinguished, and the drone can be accurately detected.

  The presence or absence of the reflected wave of the first and second frequencies may be determined from the change of the wave height of the received wave, and the frequency spectrum of the received wave may be determined as in the drone detection system of claim 5 It may be judged by spectral intensity.

  As in the inventions of claims 2 and 11, by synchronizing the search waves transmitted from the plurality of transmission devices, interference between the search waves is prevented, and the search waves from any transmission device are prevented. Can be used to detect drone. This allows for extensive detection of drone.

  The search wave may be intermittently transmitted from the transmission device. Here, when the wave receiving period of the search wave is extremely short with respect to the entire received wave, the judging section judges the reflected waves of the first and second frequencies which are Doppler shifted up and down with respect to the frequency of the search wave. It is difficult to detect from On the other hand, such a problem is solved by providing the sample hold unit which samples and holds the reception wave every predetermined fixed period and takes it into the determination unit as in the configuration of claim 3. The drone detection system may be configured to include a transmission device that intermittently outputs a search wave. For example, a carrier wave that forms a pulse wave intermittently transmitted from a radar transmitter is used as the search wave. (The invention of claim 4).

  In the drone detection system according to claim 9, the hum noise component can be suppressed from the frequency spectrum of the received wave, and the drone detection accuracy is enhanced.

Block diagram of drone detection system according to the first embodiment of the present invention (A) Frequency spectrum of hum noise, (B) Frequency spectrum of hum noise and reflected wave, (C) Frequency spectrum of hum noise and reflected wave (A) Frequency spectrum of the intermediate wave on the high frequency side, (B) Frequency spectrum of the intermediate wave on the low frequency side Conceptual diagram showing the change of the aspect of the received wave Conceptual diagram of the drone detection system of the second embodiment Conceptual diagram of the drone detection system of the third embodiment Conceptual diagram showing the change of the aspect of the received wave Block diagram of the drone detection system of the fourth embodiment Conceptual diagram of the signal from the radar transmitter

First Embodiment
Hereinafter, an embodiment of the present invention will be described based on FIGS. 1 to 4. FIG. 1 shows a drone detection system 10 according to the present embodiment and an example of a drone 91 to be detected. The drone 91 is, for example, a widely used type, and has four or more propellers 15 having a diameter of 15 to 25 [cm] which horizontally swing. Then, for example, the propeller 90 can be rotated at 1500 to 2000 [rpm] to move at a maximum speed of 50 [km / h].

  The drone detection system 10 includes, for example, a horn antenna 15 for both transmission and reception. A transmitter 11 is connected to the antenna 15 via an amplifier 12, a distributor 13, and a circulator 14. The transmitter 11 is, for example, a VCXO and is controlled by the microcomputer 22 to continuously output an AC signal of a constant frequency of 10 to 25 GHz (for example, 10 GHz). It is amplified by the amplifier 12, passes through the distributor 13, and is applied to the antenna 15 from the first port of the circulator 14 through the second port. Thereby, microwaves (electromagnetic waves) of a fixed frequency (for example, 10 [GHz]) are transmitted from the antenna 15 as a search wave. Then, a wave in a frequency band including the reflected wave of the search wave is received by the antenna 15 as a received wave, and is amplified by the amplifier 18 from the second port of the circulator 14 through the third port, and further, a phase adjuster The image rejection mixer 21 captures the image data through the number 19.

  Here, when the search wave is reflected by the drone 91 in flight, as shown in FIG. 4, it is reflected to a portion in rotational movement toward the side closer to the antenna 15 in the propeller 90, thereby Doppler-shifting to a higher frequency side than the search wave. The reflected wave (10 [GHz] + f reflected wave in FIG. 4) and the reflected wave that is Doppler-shifted to a lower frequency side than the search wave by reflecting to the part rotating in the direction away from the antenna 15 in the propeller 90 A reception wave including both of the 10 [GHz] -f (reflected wave) of FIG. 4 is taken into the image rejection mixer 21.

  The image rejection mixer 21 takes in an AC wave of a constant frequency (for example, 10 [GHz]) output from the transmitter 11 as a local wave through the distributor 13 and the amplifier 17 and combines the two local waves with a 90 degree phase difference. It distributes and mixes with each received wave to generate an intermediate wave W1 and an intermediate wave W2. Specifically, the image rejection mixer 21 splits the received wave into two in phase, a first splitter 23, splits the local wave into two 90 degrees out of phase, and splits the first wave. A first mixer 25 for mixing the one received wave and one local wave distributed by the second distributors 23 and 24 to generate an intermediate wave W1, and the first and second distributors 23 and 24. A second mixer 26 is provided which mixes the other distributed reception wave with the other local wave to generate an intermediate wave W2. Then, the intermediate waves W1 and W2 are taken into the microcomputer 22 through the A / D converter 27.

  Signal processing in the microcomputer 22 is shown as a block diagram in FIG. That is, the microcomputer 22 executes a predetermined program to shift the phase of the intermediate wave W1 by 90 degrees, a 90-degree phase shifter 29, and the intermediate wave W1 and the intermediate wave W2 whose phases are shifted by 90 degrees. It functions as an adder 31 that calculates a sum and a subtractor 32 that calculates a difference.

  Here, in the drone detection system 10 of the present embodiment, as described above, since the local wave having the same frequency as the search wave is used to down convert the received wave to the intermediate waves W1 and W2, as shown in FIG. An intermediate wave (hereinafter, simply referred to as “upper intermediate wave Wu”) of the received wave on the higher frequency side than the search wave and an intermediate wave (hereinafter, referred to as “lower intermediate wave Wd”) of the received wave on the lower frequency side than the search wave. Overlap with That is, when one of the upper intermediate wave Wu and the lower intermediate wave Wd is a desired wave, the other is an image wave (inhibition wave).

  On the other hand, in the drone detection system 10 of the present embodiment, as described above, the upper intermediate wave Wu is suppressed as an image wave and the lower intermediate wave Wd is calculated by calculating the sum of the intermediate waves W1 and W2 by the adder 31. The desired wave can be extracted, and by calculating the difference between the intermediate waves W1 and W2 by the subtractor 32, the lower intermediate wave Wd can be suppressed as an image wave, and the upper intermediate wave Wu can be extracted as a desired wave. .

  Further, the microcomputer 22 functions as an FFT 40, a hum noise removing unit 41, and a drone determining unit 42 (corresponding to a "determining unit" according to the present invention) by executing a predetermined program. Then, the frequency spectrum of the lower intermediate wave Wd and the upper intermediate wave Wu is obtained by the FFT 40 (corresponding to the “spectrum calculation unit” according to the present invention). Here, FIG. 2 (A) shows the frequency spectrum of the upper intermediate wave Wu in the absence of the drone 91, and FIG. 2 (B) shows the upper intermediate in the presence and absence of the drone 91. The frequency spectrum of the wave Wu is shown superimposed. Further, FIG. 2C shows the frequency spectrum of the lower intermediate wave Wd in the presence and absence of the drone 91 in a superimposed state. As in this example, the frequency spectrum of the upper intermediate wave Wu includes hum noise of a constant frequency.

  The hum noise removing unit 41 (corresponding to the “noise removing means” according to the present invention) removes the hum noise. Therefore, based on the received wave acquired in the absence of the drone 91, for example, the ham noise removing unit 41 previously obtains and stores the frequency spectrum of the upper intermediate wave Wu and the lower intermediate wave Wd as a ham noise spectrum. Then, processing is performed to remove the hum noise spectrum from the frequency spectrum of the lower intermediate wave Wd and the upper intermediate wave Wu. FIG. 3A shows an example of the frequency spectrum of the upper intermediate wave Wu from which the hum noise spectrum is removed, and FIG. 3B shows the frequency spectrum of the lower intermediate wave Wd from which the hum noise spectrum is removed. An example is shown.

  In the drone discrimination unit 42, in the frequency spectrum of the lower intermediate wave Wd and the upper intermediate wave Wu from which the hum noise spectrum is removed, the spectral intensity of the reference value K1 or more predetermined in the frequency band of the predetermined reference range R1 is respectively determined. It is determined whether or not there is a wave (hereinafter referred to as a “discrimination target wave”) having Then, as shown in FIG. 3A and FIG. 3B, when the discrimination target waves L1 and L2 exist in the frequency spectrum of both the lower intermediate wave Wd and the upper intermediate wave Wu, for example, for example, When the difference between the median of the frequency of one discrimination target wave L1 and the median of the frequency of the other discrimination target wave L2 is a predetermined tolerance Δf, it is judged that the drone 91 exists, and the micro The alarm 43 connected to the computer 22 is operated.

  Here, the reference range R1 can be determined based on the rotation speed that can be taken by the propeller 90 of the drone 91 to be detected and the radius of the propeller 90. In the present embodiment, the reference range R1 is set to, for example, 100 to 400 Hz. Further, the reference value K1 can be determined based on measurement experiments so that the white noise spectrum and the discrimination target wave can be distinguished. In the present embodiment, for example, the reference value K1 is set to 15 [dB]. There is. Furthermore, the above-mentioned tolerance delta f can be set up based on movement speed v which drone 91 can adopt.

  The magnitudes of the beats of the intermediate wave W1 and the intermediate wave W2 change depending on the phase difference between the reception wave and the local wave. In addition, when the beat is regarded as a signal, the beat signal is a sine wave that oscillates at the frequency difference between the received wave and the local wave, so the gradient becomes the largest at the zero crossing point. That is, the amount of change in the beat with respect to the change in the phase difference between the received wave and the local wave is the largest near the zero crossing point. Therefore, control is performed to adjust the phase of the received wave with the above-mentioned phase adjuster 19 so that the received wave is sampled by the local wave and an intermediate wave is generated in the vicinity of the zero crossing point of the sine wave of the beat signal. ing.

  Specifically, the microcomputer 22 functions as the phase control unit 34 by executing a predetermined program, detects the beat of the intermediate wave W2, and changes the phase of the received wave by a predetermined amount at the phase adjuster 19 Then, the phase when the change of the beat of the intermediate wave W2 becomes maximum with respect to the phase change is obtained by scanning. Then, the phase adjuster 19 is fixed to the phase.

  The description of the configuration of the drone detection system 10 according to the present embodiment is as described above. In the present embodiment, the “wave transmission device” according to the present invention is configured of the transmitter 11, the amplifier 12, the antenna 15, and the microcomputer 22. Further, the “reception device” according to the present invention is configured by the phase adjuster 19, the image rejection mixer 21, the microcomputer 22, and the A / D converter 27. Furthermore, the “signal according to the present invention from the 90 ° phase shifter 29, the adder 31 for computing the sum of the intermediate wave W1 and the intermediate wave W2 shifted in phase by 90 °, and the subtracter 32 for computing the difference "Processing unit" is configured.

  Next, the operation and effect of the drone detection system 10 will be described. In order to monitor the drone 91 not to enter the no-fly area, the search wave is transmitted from the antenna 15 of the drone detection system 10 toward the no-fly area. In this state, when the drone 91 enters the no-fly area, the search wave is reflected by the propeller 90 of the drone 91, and as described above, the reflected waves are respectively Doppler-shifted to the upper side and the lower side with respect to the frequency of the search wave. The received wave (see the upper part of FIG. 4) including the signal is taken into the drone detection system 10. Then, the frequency spectrum of the upper intermediate wave Wu down-converted from the received wave on the higher frequency side than the search wave (see FIG. 3A) and the lower intermediate wave down-converted from the received wave on the lower frequency side than the search wave Discrimination target waves L1 and L2 whose spectrum intensity is equal to or greater than the reference value K1 appear in the reference range R1 with the frequency spectrum of Wd (see FIG. 3B), and the discrimination target waves L1 and L2 The frequency difference of is the same within the tolerance Δf. Based on this, it is determined that the drone 91 has entered the no-fly area, and the annunciator 43 operates.

  As described above, the drone detection system 10 according to the present embodiment determines the presence or absence of the drone 91 based on whether or not the received wave received contains a reflected wave which is Doppler-shifted up and down with respect to the frequency of the search wave. Since the determination is made, for example, a tree swaying in the wind, an electric wire or the like, a bird flying in gliding, and the drone 91 can be distinguished reliably, and the drone 91 can be detected accurately. Here, when a bird flaps at a constant period, a reflected wave which is Doppler-shifted up and down with respect to the search wave may be generated, but the moving speed of the blade is sufficiently small compared to the moving speed of the propeller 90 The frequency spectrum of the wave does not fall within the aforementioned reference range R1. Further, a period in which the blades fly at a constant cycle is extremely shorter than a period in which the propeller 90 rotates at a constant cycle. As a result, there is no possibility that the flying bird is misdetected as the drone 91. In order to prevent erroneous detection of a bird more reliably, the presence or absence of the drone 91 may be determined on the condition that the same discrimination target waves L1 and L2 have been detected continuously for a predetermined period or more.

Second Embodiment
The drone detection system 10Z of this embodiment is shown in FIG. 5 and comprises a plurality of drone detection devices 10P arranged at intervals, and each drone detection device 10P is a drone detection system of the first embodiment. The configuration is substantially the same as 10. Then, one of the plurality of drone detection devices 10P is a master, and the master drone detection device 10P outputs a synchronization REF signal of 100 [MHz], and each drone detection device 10P receives this. Then, all the drone detection devices 10P transmit, for example, a search wave of 10 GHz, and the phase of the search wave also becomes "0" every time the phase of the synchronization REF signal becomes "0". Thus, the microcomputer 22 controls the transmitter 11. Thereby, mutual interference of the search wave is suppressed among the plurality of drone detection devices 10P, and each drone detection device 10P receives the reflected wave of the search wave transmitted from the other drone detection device 10P, and the drone 91 is received. Can be detected.

  Further, the detection results of the respective drone detection devices 10P are wirelessly transmitted to the master drone detection device 10P together with the position information of the drone detection devices 10P. This makes it possible to know where in the wide area the drone 91 has entered. In the present embodiment, as described above, the microcomputer 22 of each drone detection device 10P when controlling the transmitter 11 based on the phase of the synchronization REF signal is the “synchronization control unit” according to the present invention. Equivalent to.

Third Embodiment
The drone detection system 10V of the present embodiment is shown in FIG. 6 and is largely different from the drone detection system 10 of the first embodiment in that the image rejection mixer 21 is not provided. Specifically, the drone detection system 10V includes the transmitting antenna 15A and the receiving antenna 15B separately.

  The transmitting antenna 15A receives an AC wave of a fixed period (for example, 10 [GHz]) output from the first oscillation circuit 45A based on the crystal oscillator 44 through the isolator 46, and has a fixed frequency (for example, 10 [GHz] ] Is transmitted as a search wave. Then, a wave of a frequency band including a reflection wave of the search wave is received by the reception antenna 15B as a reception wave. Then, the received wave is mixed with the local wave at the mixer 21 V through the amplifier 18.

  Here, as the frequency of the local wave is conceptually shown in the upper part of FIG. 7, the frequency of the reflected wave (for example, 10 [GHz] + f) which is Doppler shifted to a higher frequency side than the search wave by the rotation of the propeller 90. ) The frequency is even higher. Specifically, in consideration of the fact that the frequency f which is higher than the search wave by the Doppler shift is approximately 100 to 400 GHz, the frequency of the local wave is 10.00001 GHz at 10 GHz +1. It is set to [KHz]). Thus, the intermediate wave generated by mixing the local wave and the received wave by the mixer 21V is an intermediate wave of the received wave on the higher frequency side than 10 [GHz] + 1 [KHz] as shown in the lower part of FIG. The wave and the intermediate wave of the reception wave on the lower frequency side than 10 [GHz] + 1 [KHz] overlap. The local wave of 10.00001 [GHz] is output from the second oscillation circuit 45B based on the above-described crystal oscillator 44.

  The reception wave generated by the mixer 21V is taken into the microcomputer 22 through the low pass filter 47 and the A / D converter 27, and the same processing as the drone detection system 10 of the first embodiment is performed. Specifically, the microcomputer 22 functions as the FFT 40, the hum noise removing unit 41V, and the drone determining unit 42V to execute a predetermined program. The FFT 40 calculates the frequency spectrum of the intermediate wave described above. Hum noise also overlaps the frequency spectrum as shown in FIG. 2 of the first embodiment. On the other hand, like the ham noise remover 41 of the first embodiment, the ham noise remover 41 V obtains and stores in advance a noise spectrum that is a frequency spectrum in a state where the drone 91 is not present. Then, processing is performed to remove the hum noise spectrum from the frequency spectrum of the intermediate wave.

  In the frequency spectrum of the intermediate wave from which the hum noise spectrum has been removed, the drone discrimination unit 42V has two discrimination target waves L1 having spectral intensities equal to or greater than the reference value K1 in the frequency band of the reference range R1 as in the first embodiment. , L2 is determined. Then, the difference between the median value of each frequency of the discrimination target waves L1 and L2 and 1 [KHz] is obtained as the Doppler shift amount, and the drone 91 is present when the difference between the Doppler shift amounts is the tolerance Δf. Then, the alarm 43 is operated.

  Also by the configuration of the present embodiment, the same effects as those of the first embodiment can be obtained. In addition, since the image rejection mixer 21 is not provided, it can be manufactured in a compact and inexpensive manner.

Fourth Embodiment
The drone detection system 10W of the present embodiment uses a signal transmitted from a radar transmitter provided at the air station of the airfield as a search wave. The radar transmitter comprises an SSR transmitter and an SLS transmitter, and the SSR transmitter transmits the A interrogation signal or the C interrogation signal at a constant cycle of 5 [msec], for example. The A interrogation signal is composed of two pulse waves (hereinafter referred to as “SSR pulse waves”) spaced by 8 [μsec] as shown in FIG. 9, and the C interrogation signal (not shown) is 21 It consists of two SSR pulse waves with an interval of [μsec]. In addition, the SLS transmitter outputs a pulse wave (hereinafter referred to as “SLS pulse wave” as appropriate) 2 [μsec] after the output timing of the first SSR pulse wave of the A inquiry signal and the C inquiry signal.

  Both the SSR pulse wave and the SLS pulse wave are modulated with a carrier wave of 1030 [MHz]. Also, the pulse width of the SLS pulse wave is 1 [μsec]. That is, since one wavelength of the carrier wave of 1030 [MHz] is about 1 [nsec], the SLS pulse wave of one pulse is composed of the carrier wave of about 1000 cycles. Then, the drone detection system 10W of the present embodiment uses a carrier wave of 1030 [MHz] constituting this SLS pulse wave as a search wave.

  The drone detection system 10W of the present embodiment is shown in FIG. 8, and the received wave received by the antenna 15 is taken into the image rejection mixer 21 through the amplifiers 18, 53, the distributor 50 and the phase adjuster 19. The same received wave is also taken into the gate control unit 51 and the search wave lock unit 52.

  The gate control unit 51 can detect the carrier wave of 1030 [MHz] constituting the SLS pulse wave with a resolution of ± 100 [nsec]. Then, the gate control unit 51 detects the leading portion of the SLS pulse wave directly received by the antenna 15 from the SLS transmitter, and outputs a gate signal every 1 [μsec] immediately after the detection. The gate control unit 51 has the same circuit configuration as that mounted on the “passive radar” sold by the applicant of the present application.

  The search wave lock unit 52 generates a local wave of 1030 [MHz] synchronized with the carrier wave of 1030 [MHz] intermittently transmitted from the SLS transmitter and continuously outputs the local wave to the image rejection mixer 21. In order to achieve the synchronization, the search wave lock unit 52 acquires a gate signal from the gate control unit 51.

  As in the first embodiment, the image rejection mixer 21 mixes the local wave and the reception wave to generate the intermediate waves W1 and W2. The intermediate waves W1 and W2 are sampled and held by the sample and hold unit 54 at a sampling period of 1 [μsec], and are taken into the microcomputer 22 via the A / D converter 27. Therefore, the sample hold unit 54 receives a gate signal from the gate control unit 51 every 1 [μsec]. Then, in the microcomputer 22, an upper intermediate wave Wu and a lower intermediate wave Wd having a length of 1 μsec are obtained from the intermediate waves W1 and W2 having a length of 1 μsec. Then, for each of the upper intermediate wave Wu and the lower intermediate wave Wd having a length of 1 [μsec], the presence or absence of the drone 91 is determined by the same processing as that of the first embodiment. Further, as in the first embodiment, the phase adjustment by the phase adjuster 19 based on the beat of the intermediate wave W2 is also performed.

  Here, in the configuration in which the search wave is intermittently transmitted as in the present embodiment, if the sample hold unit 54 described above is not provided, the wave reception period of the search wave is extremely short with respect to the entire reception wave. It becomes difficult to detect the reflected waves of the first and second frequencies which are Doppler-shifted up and down with respect to the frequency of the search wave from the entire received wave. On the other hand, in the drone detection system 10W of the present embodiment, the received wave is sampled and held for each fixed period, and the presence or absence of the drone 91 is determined for each received wave for the fixed period. The drone detection system 10W may be configured to include a transmission device that intermittently outputs the search wave.

[Other embodiments]
The present invention is not limited to the above-described embodiment, and various changes may be made without departing from the scope of the invention.

10, 10V, 10W, 10Z Drone detection system 19 phase adjuster 21 image rejection mixer 21V mixer 22 microcomputer 34 phase control unit 41, 41V hum noise removing unit (noise removing means)
42, 42 V Drone discrimination part 90 Propeller 91 Drone K1 reference value R1 reference range

Claims (11)

A drone detection system for detecting a drone flying with a propeller,
A wave receiver for receiving a wave of a frequency band including a reflection wave of a search wave transmitted from the transmission device as a reception wave;
The drone detection system which has a discrimination | determination part which discriminate | determines whether the reflected wave of the 1st and 2nd frequency which carried out the Doppler shift up and down with respect to the frequency of the said search wave is contained in the said received wave. A plurality of transmission devices for transmitting the search wave;
The drone detection system according to claim 1, further comprising: a synchronization control unit configured to control the plurality of transmission devices to transmit the search waves synchronized with one another. The search wave is intermittently transmitted from the transmission device,
The drone detection system according to claim 1, further comprising: a sample hold unit which samples and holds the received wave every predetermined fixed period and takes it into the determination unit.   The drone detection system according to claim 3, wherein a carrier wave forming a pulse wave intermittently transmitted from a radar transmitter as the transmission device is used as the search wave. A spectrum operation unit configured to operate the frequency spectrum of the received wave;
The determination unit has a spectrum intensity equal to or greater than a predetermined reference value in the frequency spectrum and shifts the same shift amount within a predetermined tolerance above and below the frequency of the search wave. The drone detection system according to any one of claims 1 to 4, wherein the two waves having the two frequencies are determined to be reflected waves of the first and second frequencies.   An image rejection mixer for mixing the local wave having the same frequency as the search wave and the reception wave, and an intermediate wave based on the reception wave on the higher frequency side than the search wave, and a reception wave on the low frequency side from the search wave The drone detection system according to claim 5, further comprising: a signal processing unit that divides the signal into intermediate waves based on the signal processing unit and applies the divided signals to the spectrum calculation unit.   An intermediate that has a mixer that mixes the local wave shifted from the frequency of the search wave by more than the shift amount of the frequency due to the Doppler shift and the received wave, and can include the reflected wave of the first and second frequencies together The drone detection system according to claim 5, further comprising a signal processing unit that applies a wave to the spectrum calculation unit. A phase adjuster that changes the phase of the received wave or the local wave;
The phase at or near the phase at which the change of the beat of the intermediate wave becomes maximum with respect to the change of the phase is obtained by scanning, and the phase of the received wave or the local wave is fixed to the obtained phase. The drone detection system according to claim 6, further comprising: a phase control unit that controls the phase adjuster.   9. A noise removing means according to any one of claims 5 to 8, further comprising noise eliminating means for storing the frequency spectrum of the received wave received in advance without a drone as a noise spectrum and subtracting the noise spectrum from the frequency spectrum of the received wave. A drone detection system according to claim. A drone detection method for detecting a drone flying with a propeller,
The drowning based on whether or not the reflected wave of the search wave transmitted from the transmission apparatus includes the reflected waves of the first and second frequencies which are Doppler-shifted up and down with respect to the frequency of the search wave. Drone detection method to determine the presence or absence of   11. The drone detection method according to claim 10, wherein a plurality of transmission devices are arranged apart from one another and the search waves synchronized with each other are transmitted from the transmission devices.