JP3068062B2 - Aircraft detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for detecting only signals of an aircraft or the like from radar video, converting the signals into data, and transmitting the data to an air traffic control station or the like at a remote location. And a signal detection device for detecting and outputting only necessary signals from an aircraft or the like.

[0002]

2. Description of the Related Art Conventionally, only signals from an aircraft or the like are detected from a radar video output from a radar apparatus by using a technique called DCC control. FIG. 8 shows the DCC control.
As shown in the basic principle, a threshold level for signal detection which is arbitrarily set is set in consideration of the S / N characteristic of radar video, and a signal above that level is detected and output. . As an example of the DCC method, there is a detection method as disclosed in JP-A-63-85383. As the video to be used, an MTI video in which a reflected signal of a mountain or the like is removed and only an aircraft flying at high speed is extracted is used.

In the case of an air route monitoring radar system, an MTI video, an azimuth signal and a radar trigger are input from the radar device. This radar system has 200
With NM coverage, the aerial rotates 360 degrees in 10 seconds. The azimuth signal includes an azimuth reference signal (ARP) output when the antenna is facing magnetic north once every 10 seconds, and an azimuth signal (A) that outputs 4096 pulses per rotation.
CP) is output. Trigger is about 300 pps
It is output at the timing of (output 300 pulses per second). Also, MTI video has a maximum amplitude of 2V and 200
The signal of the NM coverage is output.

[0004]

As described above, in the conventional air route monitoring radar system, the noise component other than the target is removed by the MTI process and the DCC control. There is also a limit, and a false signal, which is a remaining clutter, may be generated as in the example shown in FIG.

[0005] The cause of the false signal is that the level of the reflected signal (referred to as ground clutter) from a fixed object such as a mountain is too high to saturate and cannot be completely removed by the MTI process, or a rain cloud or the like. Reflected signal from a low-speed moving object (weather clutter)
Due to the mobility, there is a case where the data is output without being suppressed by the MTI process like the aircraft.

The false signal generally has a higher amplitude than the noise signal, and its level is higher than a threshold level. Therefore, even if DCC control is performed, the false signal is detected as a signal as in an aircraft. That is, as shown in FIG. 7, the aircraft is displayed as a line called a blip, and the false is displayed as a dot. However, in the case of DCC control, as shown in FIG. Will be done.

Therefore, it is conceivable to set the threshold level to a high level. However, if this is done, there is a possibility that the detection of the aircraft may not be performed, and the original purpose cannot be achieved.

[0008] The detected signals of the aircraft and the like are input to a computer at an air traffic control station in a remote place and processed, and the controller or the like displays a display as shown in FIG. However, since the false signal is also processed and displayed in the same manner, the controller may cause a false recognition (a false fall is recognized as an aircraft) or the like, which may cause confusion in the control operation.

Further, when a large number of false signals are generated, the false signals are inputted to a computer of a remote control station. In general, this computer is configured by predicting the number of airplanes in the control airspace and the like. Therefore, if a large number of false signals are input beyond the processing capability, overwork may occur in the computer processing capability, and a malfunction that may lead to a system down may also occur. In this case, since all the processes are stopped, no information is displayed and the business cannot be continued, which may lead to an accident.

Therefore, at present, the MTI processing of the radar device is appropriately adjusted and set in order to suppress a false signal. In this case, if the suppression by the MTI process is set strongly, the aircraft itself is also suppressed. Therefore, a trade-off is made between the aircraft detection probability, the number of false signals, and the computer processing ability.

However, the false signal changes as needed depending on the state of the reflected signal from the ground clutter and the weather clutter, and the reflected signal from each clutter also depends on the environment of spatial propagation. Even when the system is operated, there are cases where a large number of false occurrences occur.

[0012] For the radar device itself unmanned system,
It is impossible for a person to go to the radar site to perform resetting / adjustment every time the situation changes, and the radar signal side generates a false signal due to the limit of the MTI processing itself of the radar device. No further action is possible.

An object of the present invention is to provide a signal processing method for suppressing the detection of a false signal in view of the limitation of DCC control and the limitation of MTI processing capability.

[0014]

According to the present invention, only an aircraft is detected from an MTI video and an azimuth signal from an MTI video and an azimuth signal output from a radar device, and after detecting its position (distance and azimuth from the radar), In an aircraft detection device that outputs as aircraft detection information, attention is paid to correlation between sweep signals, and integration is performed between sweep signals of MTI video, and an unerased signal (called a false signal) of the MTI process existing in the sweep signal is generated. Sweep integration that suppresses and emphasizes and outputs only aircraft signals that remain in a high amplitude state even after sweep integration due to the number of hits (indicating that they have high amplitude over several sweeps) Means and also accumulates several MTI videos for several scans and performs scan integration between sweep signals in the same direction to form A scan integration means for outputting only the scan signal, the sweep signal of the sweep integrator means output (including a high amplitude aircraft signal and the suppressed false signal)
And a sweep signal (existing only a false signal) output from the scan integrator to remove the false signal by a differential effect, and output a sweep signal in a state where only the aircraft signal is detected (referred to as a differential signal). The video signal difference means and a differential signal for several sweeps are compared with each other at the same distance, and the amplitude of the signal is compared.
The azimuth signal output at the same time as the I-video detects the azimuth of the sweep having the maximum value, and the distance from the reference point of the sweep (0 NM is a normal reference, and the position of the radar device is 0 NM). Maximum position detection means for calculating the azimuth and the distance (maximum position) of the maximum value signal, and removes the false signal existing due to the MTI processing capacity limit of the radar apparatus to reduce the aircraft signal. It is characterized by outputting only a signal.

In the aircraft detection device according to the present invention, the MTI video output from the radar device is converted into a digital signal by A / D conversion means similar to the prior art, and is output in sweep units. (Hereinafter, this signal is referred to as a sweep signal.) This sweep signal is input to the sweep integration means and the scan integration means.

In the sweep integration means, integration processing is performed between the sweep signals, and the resulting sweep signal is output. Sweep integration indicates a process of adding a sweep signal in units of several sweeps and dividing by the added number of sweeps.
A so-called averaging process between sweep signals is performed. The sweep signal resulting from the sweep integration is input to the video difference means.

At the same time, the scan integration means performs a scan integration process between sweep signals in the same direction, and outputs a resultant sweep signal. This scan integration means has a memory that can store several scans. The scan integration is a so-called averaging process between scans, which indicates a process of adding sweeps in the same direction in units of several scans and dividing by the added number of scans. The sweep signal resulting from the scan integration is also input to the video difference means.

The video difference means performs a difference process between the sweep-integrated sweep signal and the scan-integrated sweep signal in the same direction, and removes only the false signal, resulting in a sweep signal (differential difference) resulting from only the aircraft signal. (Referred to as a signal) to the maximum value position detecting means.

The maximum value position detecting means compares the maximum value between signals of the same distance from the differential signals for several sweeps, and detects the azimuth of the sweep signal having the maximum amplitude.
As a reference signal for azimuth detection, a radar azimuth signal output from the radar device in the same manner as MTI video is used, and the azimuth of the sweep signal of the maximum value signal is detected. Further, similarly, using the trigger of the distance reference signal output from the radar device, the time from the trigger of the maximum value signal, that is, the distance from the radar device, is calculated.

As described above, the azimuth information and the distance information, which are the positions of the maximum values, are output to the data conversion means as aircraft information. The data conversion means can be realized using a conventional technique such as a microprocessor. The data is converted into data for computer processing at a remote control station and transmitted. Since the false signal is removed from the MTI video by the sweep integration means, the scan integration means and the video difference means, and becomes only the aircraft signal,
The data to be transmitted to the control station after data conversion does not include a false signal.

According to the present invention, the sweep integration is performed by paying attention to the inter-sweep correlation in which the spread existing in the azimuth direction differs between the aircraft existing on the MTI video and the false as shown in FIG. False signals produce a suppressed sweep signal, while between scans, the false is correlated, but because the aircraft does not stay at a fixed position, the aircraft signal amplitude is suppressed by performing the scan-to-scan integration. . Then, only the false signal is removed from the sweep signal in which the aircraft signal exists by subtracting the signal of only the false by the scan integration from the signal by the sweep integration.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram showing an embodiment of the present invention, and FIGS. The operation is performed digitally.
In FIG. 5, for the sake of simplicity, analog representation is used.

In FIG. 1, an MTI video in a sweep signal state output from a radar device is first converted into a digital signal by A / D conversion means and input to a sweep integration means 1 and a scan integration means 3. . Each input signal is conceptually shown in FIGS. 2A, 2B and 3A,
Shown as (b).

The sweep integration means 1 temporarily buffers the input sweep signal (FIG. 2A) and performs integration processing with the input sweep signal (FIG. 2B) at the next timing. Do it.

In the integration, the sweep signal shown in FIG.
The sweep signal of FIG. 2B is added to generate the added sweep signal (FIG. 2C). The added sweep signal is divided by the added number of sweeps to generate an averaged sweep signal (FIG. 2D).

That is, by the sweep integration, a false having no correlation in the sweep is suppressed to V2 / sweep integral number with respect to the amplitude of V2 at the time of input, but the correlation between the sweep of the aircraft signal is smaller than that of the false signal. Therefore, even if the sweep integration is performed, it is generated in the state of V2 without change.

In the present description, the number of additions and the number of divisions of the sweep signal are set to 2, but these values can be changed as appropriate and are not fixed. Since the actual aircraft is located at the same position (distance) over several sweeps (about 20 sweeps, but an arbitrary number depending on the beam width of the radar device), the number of additions / divisions Has a function set according to the characteristics of the articulated radar device. FIG. 9 shows an example of the width (the number of hits) in the azimuth direction of the aircraft signal on the MTI video.

The averaged sweep signal shown in FIG. 2D, which is an output signal from the sweep integration means 1, is input to the video difference means 5 via the signal line 2.

On the other hand, the scan integrator 3 is arranged as shown in FIG.
The sweep signal shown in FIG. 2A is temporarily stored, and a scan integration process is performed between the sweep signal and the sweep signal in the same direction in FIG. 3B in the next scan. That is, the sweep signals of FIGS. 3A and 3B are added,
An addition sweep signal (FIG. 3C) is generated.

The generated sweep signal shown in FIG. 3C is divided by the added number of scans to generate a sweep signal shown in FIG. 3D. The signal in FIG. 3D is a sweep signal averaged between the scans in FIGS. 3A and 3B.

The number of additions / divisions in the scan integrator 3 is also determined by the sweep integrator 1 as described above.
It is not fixed to 2 shown in the present description, but has a function that can be arbitrarily set based on characteristics such as the antenna rotation speed of the connected radar device.

The averaged sweep signal shown in FIG. 3D is compared with a threshold level set to a predetermined level, and only a false state is detected.
This is output as the sweep signal (f).

It has a function that the set value of the threshold level can be arbitrarily set according to the S / N characteristic of the connected radar device. For example, in an air traffic control radar, the signal amplitude is set to 2 V and the noise amplitude is set to less than 0.5 V on the radar device side. In this case, the threshold level is set to 0.5 V.

The sweep signal shown in FIG. 3F is input to the video difference means 5 through the signal line 4. Video difference means 5
Then, the sweep signal obtained by the sweep integration input through the signal line 2 (FIG. 4A) (the same signal as FIG. 2D)
And a sweep signal (FIG. 4)
(B)) (the same signal as in FIG. 3 (f)) is subjected to a difference process. That is, the difference signal (FIG. 4 (c)) is generated by subtracting the sweep signal of FIG. 4 (b) from the sweep signal of FIG. 4 (a).

A threshold of a certain level is set for the difference signal (FIG. 4C), and only a signal portion above the threshold level is extracted to extract an aircraft signal (FIG. 4C).
Output as (c). This threshold level is set arbitrarily according to the S / N characteristic of the MTI video of the radar device, as in FIG. 3 (e) described above.

An example of a method for extracting this portion will be described under the following conditions.

Aircraft signal amplitude: 2 V Noise signal amplitude: 0.4 V A / D conversion bit number: 4 bits The above amplitude uses the amplitude condition of MTI video of an air traffic control radar, but A / D conversion The number of bits is set to 4 bits so that the concept can be easily explained.

For a 4-bit A / D conversion, when representing up to 2 V, if it changes every 0.125 V, it changes one bit at a time (since 2V ÷ 16 = 0.125 V). The noise signal amplitude arbitrarily changes between 0 V and 0.4 V and is represented by the following bit pattern.

When the noise signal amplitude is 0 V: (MSB) 0000 (LSB) In the case of 0.125 V: 0001 In the case of 0.25 V: In the case of 0.375 V: 0011 Since the noise signal is less than 0.5 V, It is represented by any of the above four patterns.

On the other hand, since the aircraft signal is 0.5 V or more,
Data is displayed from the third bit (0100 to 111)
1) Therefore, in the case of this signal, the threshold level is set to 0.5 V, and only the signal having the data bit “1” from the third bit needs to be extracted. Also, the amplitude of this signal can be detected as it is with 4 bits.

As described above, the sweep signal (FIG. 4D) obtained by detecting only the aircraft signal is input to the maximum value position detecting means 7 through the signal line 6. As shown in FIG. 5, the maximum value position detecting means 7 compares amplitudes at the same distance between several sweeps and detects a sweep signal having a signal of the maximum value.

The determination of the maximum value is performed by the logic shown in FIG. That is, when an aircraft signal is detected at the same distance over a plurality of adjacent sweeps, the amplitude of the plurality of sweep signals is compared to determine the largest one.
In the case of FIG. 5, V2 of the sweep signal has the maximum value.

After detecting the maximum value, the azimuth of the sweep signal is detected and output as aircraft information. This aircraft information is converted into data by a data conversion circuit and transmitted to a computer of a remote control station via a digital line or the like.

The MTI video and the azimuth signal are input from the radar device at the timing shown in FIG. The timing shown in FIG. 5A is secured in each means, and the difference signal input to the maximum value position detecting means 7 also has the timing shown in FIG. Therefore, the direction of the sweep signal can be detected using the direction signal.

Further, a radar trigger (referred to as a trigger) similarly input from the radar apparatus operates the internal clock according to the present invention with the trigger as a starting point, whereby the position of the maximum value signal from the trigger, that is, the distance from the trigger. Information is obtained.

FIG. 6 shows an embodiment of the present invention to which the above connection relation of timing signals is added.

In the case of an air route monitoring radar system, an MTI video, an azimuth signal and a radar trigger are input from the radar device. This radar system has 200
With NM coverage, the aerial rotates 360 degrees in 10 seconds. The azimuth signal is an azimuth reference signal (ARP) output when the antenna is facing magnetic north once every 10 seconds,
An azimuth signal (ACP) that outputs 4096 pulses in one rotation is output. The trigger is output at a timing of about 300 pps. Also, MTI video has a maximum amplitude of 2V and 2
The signal of the 00NM coverage is output.

The aircraft detection device includes a sweep integration circuit 1,
It comprises a scan integration circuit 3, a video difference circuit 5, and a maximum value position detection circuit 7. The internal clock is 1.5 μs, which is the same as the system clock of the radar device.

Each integral number is a sweep integral number: 5,
The case where the number of scan integrals is 16 will be described.

The MTI video output from the radar system has an amplitude of 2 V at the maximum, and has information for 200 NM in synchronization with the radar trigger. In this video, there are receiver noise signals, aircraft signals and false signals.

The MTI video is digitized by an A / D conversion circuit, and the sampling clock is 4 μs in 1.5 μs.
Generate with bits. The digitized MTI video is input to the sweep integration circuit 1 and the scan integration circuit 3. The sweep integration circuit 1 and the scan integration circuit 3
Synchronous with the trigger (300 pps), M
Capture TI video.

In the sweep integration circuit 1, the sweep signals are sequentially stored for five sweeps, the sweep integration is performed between the five sweep signals, and the sweep signal subjected to the sweep integration on the signal line 2 is input to the video difference circuit 5. The concept of the sweep integration is the same as that of FIG. 2 (however, the integration number is 5 instead of 2), and the sweep signal shown in FIG.
Is input to

The scan integration circuit 3 has a scan memory for 360 degrees and sequentially stores sweep signals. The sweep signal of the next scan is added to the sweep signal of the previous scan, and when the 16 scans are added, division for 16 scans is performed.

Writing to the scan memory is stored in sweep units in synchronization with a trigger, and integration processing is performed between sweep signals of the same azimuth using azimuth signals. The concept of scan integration is the same as that of FIG. 3 (however, the number of integration is 16 instead of 2). A threshold of 0.5 V is set for the integrated sweep signal of FIG. Extract only. As a result, the sweep signal shown in FIG.

The video difference circuit 5 performs difference processing on the sweep signal of FIG. 4B obtained by scan integration of only the false signal from the sweep signal of FIG. 4A subjected to the sweep integration processing. A difference signal shown is generated.

The difference signal includes only the aircraft signal from which the false signal has been removed and the noise signal. A 0.5 V threshold level is set for the sweep signal, and the aircraft signal shown in FIG. To detect.

The maximum value position detection circuit 7 outputs the sweep signal shown in FIG. The maximum value position detection circuit 7 compares the 4-bit amplitudes of the aircraft signals at the same distance between the sweeps while detecting the azimuth of the sweep signal in FIG. 4D based on the azimuth signal.

The width in the azimuth direction for performing the maximum value comparison depends on the reception level in the azimuth direction of the aircraft processed by the air route monitoring radar. As shown in an example in FIG. 9, since there are approximately 20 sweeps, when the sweep integral number is 5,
In the sweep signal obtained as a result of the integration, the signal of the same aircraft exists for four sweeps.

For this reason, 4-bit data between 4 sweeps at the same distance is compared to detect the maximum value. The azimuth of the sweep signal where the signal having the maximum value exists is the azimuth where the aircraft is located.

The distance of the aircraft is determined by the number of clocks sampled with the internal clock of 1.5 μs from the signal of FIG. ) Is the distance from the radar.

From the above, the position (azimuth and distance) of the aircraft
Is calculated, and this information is converted into data by a data processing circuit constructed by a conventional technique (microprocessor or the like) and transmitted to a remote computer.

The output signal (signal line 4) from the scan integration circuit 3 shown in FIG. 4 (f) is output in parallel to provide a system for evaluating the MTI processing function of the radar device itself. Also available.

That is, the number of the detected false signals is counted, and the MTI processing is evaluated. In addition, as a result of the evaluation, if the number increases beyond a certain number, a function to output an alarm to the computer side shall be provided and used as a fail-safe function such as protecting the computer by shutting down the line before the system goes down. Can be.

When the output from the video difference circuit 5 is directly input to a conventional aircraft detection device, and the signal is detected by the conventional detection device under DCC control, it is configured to serve as a false elimination device. Is done.

[0065]

According to the present invention, since an aircraft detection process is performed after removing a false signal existing in an MTI video output from a radar device, an aircraft detection by DCC control is performed using the conventional MTI video as it is. Compared to the device, false detection and transmission of false signal information are eliminated, false information is not displayed together with aircraft information, and the controller may mistakenly recognize (falsely mistaken a false aircraft). Disappears.

Further, since only necessary aircraft information can be inputted to the computer of the control station, shutdown due to excessive computer processing capacity (overload) due to a false signal does not occur, and the reliability of the entire control system is improved. .

[0067]

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing the concept of sweep integration in the present invention.

FIG. 3 is a diagram showing the concept of scan integration in the present invention.

FIG. 4 is a diagram showing a difference concept in the present invention.

FIG. 5 is a diagram showing the concept of maximum value position detection in the present invention.

FIG. 6 is a block diagram showing another embodiment of the present invention.

FIG. 7 is a diagram showing a concept of radar video and a display on a control station side.

FIG. 8 is a diagram illustrating the concept of DCC detection in a conventional method.

FIG. 9 shows an aircraft signal and a false signal on the MTI video of the present invention.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 sweep integration means 2 signal line (sweep integration output) 3 scan integration means 4 signal line (scan integration output) 5 video difference means 6 signal line (difference signal) 7 maximum value position detection means

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G01S ⁷ /00-7/42 G01S 13/00-13/95

Claims (6)

(57) [Claims] 1. An MTI video signal and an azimuth signal output from a radar device, only an aircraft signal is detected on a sweep signal of the MTI video, and after detecting the position thereof,
In an aircraft detection device that outputs as aircraft detection information, a plurality of adjacent sweep signals of the MTI video are accumulated, and integration is performed between the accumulated plurality of sweep signals to output a sweep signal in which a false signal is suppressed. A sweep integrator, a scan integrator that accumulates the MTI video signal for a plurality of scans, and performs integration between the accumulated plurality of scan signals in the same direction to detect and output only a false signal; The difference processing is performed by inputting the output of the sweep integration means and the output of the scan integration means, and a video difference means for outputting a sweep signal from which the false signal has been removed, and a sweep signal from the video difference means, That maximum value position detecting means for determining and outputting the position of the aircraft is provided. Characteristic aircraft detection device. 2. The sweep integration means according to claim 1, further comprising means for adding a predetermined number of adjacent sweep signals, and means for dividing the added sweep signal by the predetermined number. An aircraft detection device as described in the above. 3. The scan integrating means includes means for adding a predetermined number of sweep signals of the same direction, and means for dividing the added sweep signal of the same direction by the predetermined number. The aircraft detection device according to claim 1, wherein 4. The video difference means for subtracting the output of the scan integration means from the output of the sweep integration means, and setting a constant level threshold for the subtracted sweep signal, 2. The aircraft detection apparatus according to claim 1, further comprising means for extracting and outputting only a signal portion having a hold level or higher. 5. The maximum value position detection means inputs a predetermined number of sweep signals output from the video difference means,
Means for comparing the amplitudes at the same distance between the predetermined number of sweep signals to detect a sweep signal having a maximum amplitude,
2. The aircraft detection apparatus according to claim 1, further comprising: means for detecting the direction of the sweep signal having the maximum amplitude; and means for outputting information detected by the two means as aircraft position information. 6. A means for inputting a signal output from the scan integration means, counting the number of the detected false signals, and outputting an alarm when the count value is equal to or more than a predetermined number. Claim 1 characterized by the following:
An aircraft detection device as described in the above.