JPH0477273B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a radar signal transmission system for an air route surveillance radar and its transmitting/receiving device.

[Prior Art] In the air route monitoring radar system currently in operation, radar signals from fixed targets, moving targets, etc. of the primary radar are processed by predetermined sweep video signals or a portion of the sweep video signals that include the radar signals. The swept video signal is sampled at a sweep interval of , and the sampled swept video signal is time-expanded and band-compressed, then subjected to residual sideband modulation and transmitted over an analog communication line. (Tokuko Showa 54
-23238) On the receiving side, after receiving and demodulating, time compression is performed.
The extracted sweep video signal is interpolated to reproduce the radar signal and display it on the radar indicator.

However, in recent years, communication lines have been shifting from analog communication lines to digital communication lines, and it is now necessary to transmit radar signals of air route monitoring radars using digital communication lines as well.

[Problems to be Solved by the Invention] In this way, since the swept video signal containing the radar signal is extracted at predetermined sweep intervals and transmitted, the thinned-out swept video signal is not transmitted, so that was a cause of radar signal deterioration.

On the other hand, if the analog band compression signals that are currently transmitted over analog communication lines are to be digitized and transmitted as is, the amount of information to be transmitted is extremely large, especially for fixed target video signals. This requires a high-speed digital communication line, which poses problems such as higher line usage fees.

In this invention, a moving target video signal with a small amount of information can be transmitted in real time over a low-speed digital communication line, and a fixed target video signal with a large amount of information can be transmitted at a lower transmission speed over a low-speed digital communication line. The purpose of this invention is to provide a transmission system and its transmitting/receiving device that can reduce line usage charges.

[Means for Solving the Problems] The present invention separates a radar signal of a surveillance radar into a fixed target video signal caused by a fixed target and a moving target video signal caused by a moving target, and then converts each into a digital signal. The digitized fixed target video signal is transmitted by adding an antenna angle signal and time stretching to reduce the transmission speed, and the digitized moving target video signal is transmitted by adding an antenna angle signal and a distance signal. It uses a time-based transmission method.

Also, the radar signal of the surveillance radar is separated into a fixed target video signal and a moving target video signal, and is converted into a digital signal. , extracted every predetermined number of sweeps, time-expands each extracted swept video signal, adds an antenna angle signal to it, and transmits it. In the next scan, the transmitted swept video signal is shifted by one. The sweep video signal located next to the extracted sweep video signal is sequentially extracted every predetermined number of sweeps and transmitted in one scan time in the same manner as above, and the entire sweep video corresponding to one scan is generated. By transmitting all the signals, the transmission rate of the fixed target video signal is reduced.

On the other hand, the digitized moving target video signal is
A method is adopted in which a distance signal and an antenna angle signal are added to transmit a full sweep video signal for one scan in one scan time.

Furthermore, the fixed target video signal and the moving target video signal are separated and digitally converted, an antenna angle signal is added to the swept video signal including the fixed target video signal, and this signal is stored in a memory corresponding to the antenna angle signal. After sequentially storing the sweep video signals in the memory, the sweep video signals stored in the memory are sequentially read out and transmitted using a reading angle signal that is sufficiently slower than the antenna angle signal, thereby reducing the transmission speed.

On the other hand, a method is adopted in which a distance signal and an antenna angle signal are added to a sweep video signal including a digitized moving target video signal and transmitted in one scanning time.

[Operation] The fixed target video signal has a large amount of information, and the moving target video signal has a small amount of information. Therefore, after separating the primary radar signal into a fixed target video signal and a moving target video signal, each signal is A/D converted.

For information-rich fixed target video signals,
A gate signal for extracting a swept video signal with an angle gate generator using the integrated antenna angle signal obtained by integrating the antenna angle signal from the primary radar with an angle integrator and a trigger signal indicating the transmission time. Using this gate signal, a sweep video signal extractor extracts every predetermined number of sweeps from all the sweep video signals including the fixed target, time-stretches this extracted sweep video signal, and integrates it with this signal. By combining the obtained antenna angle signals with a signal combiner and sending them out via a multiplex transmitter, the transmission speed becomes lower and a low-speed digital communication line can be used.

Alternatively, the antenna angle signals integrated by the angle stacker are added to the full sweep video signal including the fixed target video signal, and the signals are sequentially stored in addresses corresponding to the antenna angle signals in the memory.

Information in this memory is slowly read out using a sufficiently slow reading angle signal and sent out via a multiplex transmitter to reduce the transmission speed.

On the other hand, after the moving target video signal is A/D converted, a signal at a certain level is detected by a signal detector. The signals are combined by a signal combiner and sent to a low-speed digital communication line via a multiplex transmitter.

In the receiving device, the multiplex receiving device receives the signal, sorts it into a fixed target video signal and a moving target video signal, and stores the fixed target video signal for one scan, that is, the full sweep video signal, in a memory corresponding to the antenna angle signal. do. The information stored in this memory is sequentially read out using a reproduction trigger/angle signal based on the antenna angle signal to reproduce a fixed target video signal.

On the other hand, the signal selected as a moving target video signal is separated into an antenna angle signal, a distance signal, and a moving target detection signal, and is reproduced based on the trigger/angle signal for reproduction.

The respectively reproduced fixed target video signal and moving target video signal are combined and displayed on the radar indicator.

[Example] An example of the present invention will be described in detail based on FIGS. 1 and 2.

Generally, the reception signal of an air route surveillance radar is a fixed target video signal (hereinafter referred to as
The moving target video signal (hereinafter referred to as the MTI signal) from the moving target is broadly divided into the NOR signal) and the moving target video signal (hereinafter referred to as the MTI signal) from the moving target.

In the case of the PPI display of an air route monitoring radar, a series of reflected waves of the NOR signal are received every sweep at approximately 0.1 degree intervals, so the amount of information is extremely large, and a wide occupied frequency band is required. Therefore, in order to transmit the digital NOR signal as it is in real time,
High-speed digital communication lines are required.

On the other hand, the MTI signal is a radar signal that selects only the reflected waves from moving targets, so the amount of information is
It is much smaller than NOR signals and can be transmitted in real time over low-speed digital communication lines.

Moreover, since MTI signals are used for constant control, they must be transmitted in real time, but NOR
The signals are not normally used for direct air traffic control, but are used to confirm from a fixed target whether the air route monitoring radar system is operating normally, so there is no need to transmit it in real time. do not have. Therefore, since almost the same NOR signal is received every scan, the inventor extracted the entire sweep video signal for one scan including the NOR signal at appropriate time intervals and transmitted it over time. We focused on the fact that by storing one scan's worth of signals in memory on the receiving side and updating the contents, digital communication lines with low transmission speeds can be used.

Below, as an example, one scan can be done in 10 minutes.
The method of transmitting the NOR signal will be explained.

Assume that the sweep interval of the surveillance radar is 0.1 degree, the total sweep video for one scan is 3600 sweeps, and the time for one scan is 10 seconds.

Figure 1 shows a method for extracting a swept video signal to be transmitted. Assuming that the displayed radar signal is not delayed, the swept video signal is extracted every P=60 sweeps, that is, every 6 degrees. It shows.

1 is a sweep video signal that was transmitted 10 seconds ago, and 2 is a sweep video signal that is currently being transmitted, which is transmitted after being extended for 60 sweeps, that is, 1/6 second. 3 is
Sweep video signal 4 to be transmitted after 10 seconds is located next to sweep video signal 2 currently being transmitted, that is, at the 60th sweep, and is a sweep video signal to be extracted after 1/6 second. Like the sweep video signal 2, it is transmitted after being expanded in time by 1/6 seconds.

In this way, every 60 sweeps the swept video signal 2,
4... are extracted and transmitted in one scanning time of 10 seconds.

In the next scan, counting from the sweep video signal 3 that follows the sweep video signal 2, it is extracted every 60 sweeps (signal 5) and transmitted in the same manner as above, so that one scan time is 10 seconds. Because it is
A full sweep video signal of 3600 sweeps is transmitted in 10 minutes.

Note that the transmission time for one scan is not limited to the above example.
You can set it to any time you like, whether it's 20 minutes or 5 minutes.
It is sufficient to set the time so that the displayed radar signal is not delayed.

FIG. 2 shows a block diagram of a surveillance radar system using the transmission method according to the present invention. 11 is the primary radar, and the analog NOR signal 12 which receives the reflected wave from the fixed target and the signal from the moving target. Analog MTI in which only the reflected waves of
An antenna angle signal 13 indicating the direction of the antenna and a trigger signal 14 determining the transmission time are output.

The NOR signal 12 from the primary radar 11 is an A/D
It is converted into a digital signal by a converter 16 and sent to a swept video extractor 17. The antenna angle signal 13 is integrated by an angle integrator 19, and an angle gate generator 20 using the obtained antenna angle signal and trigger signal 14 converts the swept video signal into 60
Generates a gate signal for extraction every sweep.

The gate signal from the angle gate generator 20 is input to a sweep video extractor 17, which extracts a digitized NOR signal 12 every 60 sweeps using the gate signal. These extracted sweep video signals 1, 4...
and the antenna angle signal integrated by the angle integrator 19 are combined by the signal combiner 18 and sent to the digital communication line 26 via the multiplex transmitter 25.

In the receiving device, it is received by the multiplex receiving device 27,
The signal is separated into a signal selected as a NOR signal and a signal selected as an MTI signal.

The signal selected as a NOR signal is separated into a sweep video signal and an antenna angle signal by a first signal separator 28, and a memory 29 that can store the NOR signal for one scan (3600 sweeps of the entire sweep video signal)
Sweep video signals are stored at addresses corresponding to the antenna angles within. On this occasion,
The memory 29 is empty for the first 10 minutes, but after 10 minutes all the memories 29 are filled with sweep video signals.

The fixed target signal regenerator 30 sequentially reads out the information stored in the memory 29 and converts it into an analog signal.
The NOR signal 12 is reproduced, and the timing of this readout uses a trigger/angle signal corresponding to the antenna angle signal generated by the trigger/angle generator 31 based on information from the MTI signal.

On the other hand, the MTI signal 15 is a signal in which only reflected waves from moving targets such as aircraft are selected, and the amount of information thereof is much smaller than that of the NOR signal 12. Therefore, it is possible to digitize the MTI signal 15, add an antenna angle signal and a distance signal to the reflected wave from one target object, and transmit the resultant signal over a low-speed digital communication line.

Therefore, the MTI signal 15 from the primary radar 11
is converted into a digital signal by the A/D converter 22, and a signal higher than the set level is detected by the signal detector 23. This detected signal is combined with the distance signal obtained from the trigger signal 14 by the distance integrator 21 and the integrated antenna angle signal obtained by the angle integrator 19, and the signal synthesizer 24 combines the distance signal obtained from the trigger signal 14 with the integrated antenna angle signal obtained by the angle integrator 19. The data is sent out to the digital communication line 26 via the digital communication line 26.

On the receiving side, it is received by the multiplex receiver 27,
The signal selected as the MTI signal is separated by the second signal separator 32 into an antenna angle signal, a distance signal, and a moving target detection signal.

The trigger/angle generator 31 generates a trigger/angle signal corresponding to the antenna angle signal separated by the signal separator 32.
Create an angle signal. In the moving target signal regenerator 33,
Based on the trigger/angle signal from the trigger/angle generator 31, an analog signal is generated from the moving target detection signal.
Regenerate MTI signal 15.

In this way, the respectively reproduced analog NOR signal 12 and MTI signal 15 are combined,
It is displayed on the radar indicator 34.

As will be described later, in this embodiment, signal processing is relatively easy, and the overall device The configuration of can be simplified.

Here, according to the inventor's calculations, the transmitting NOR
Assuming that the signal strength of the signal is 4 bits, the repetition frequency of the surveillance radar is 360pps, the range bin is 1/8 nm, that is, the radius of the PPI display of the surveillance radar is 200 nm, and this is sampled at 1/8 nm, NOR
Since 1600 signals are sampled, the amount of information on one screen of the surveillance radar is 23.04 Mbit. NTT
To transmit this as is using the line
A high-speed digital communication line of 6Mbps is required.

Therefore, if the amount of information for one screen is transmitted over 10 minutes as described in the above embodiment, it is sufficient to send 38.4 Kbits per second. In reality, assuming that the amount of information of control signals such as frame signals and parity signals that indicate signal divisions is 0.1 times the amount of information for one screen, the amount of information when digitally transmitting a NOR signal is 38.4 × 1.1 = 42.3Kbps, which significantly reduces the amount of information, and the digital communication line used can use a lower-speed line, making line usage fees much cheaper.

Also, assuming that there is no remaining MTI signal,
Only signals reflected by aircraft within a radius of 200 nm are present. Therefore, we used 100 conventional aircraft, the number of pulse hits per aircraft was 13, the range bins of the integrated antenna angle signal and distance signal were 12 bits and 11 bits, respectively, and the sweep video signal was 4 bits.
Assuming that the pulse width is 3 μ and 3 range bins are required, the amount of information in the MTI signal for one screen is 100 x 13 (12 + 11 + (4 x 3)) = 45.5 Kbit. To transmit this information with one scan time of 10 seconds, it will be approximately 5 Kbits per second or more, so a communication line with this transmission speed can be used.

FIG. 3 shows another embodiment of the present invention, in which a memory 42 is used in the transmitting device.
This is designed to reduce the transmission speed of the fixed target video signal, and as in the first embodiment, the primary radar 11 transmits the NOR signal 12 and the MTI signal 1.
5, an antenna angle signal 13 and a trigger signal 14 are output.

The NOR signal 12 is converted into a digital signal by the first A/D converter 41 and sent to the memory 42.

The antenna angle signal from the primary radar 11 is integrated by an angle integrator 44. The integrated antenna angle signal and the trigger signal 14 for timing are read into the memory 42. The memory 42 has 1
It can store 12 NOR signals for scanning.
The swept video signal including the NOR signal from the A/D converter 41 is temporarily stored in the address corresponding to the antenna angle signal in the memory 42 using the integrated antenna angle signal and the trigger signal.

The information stored in the memory 42 is read out by the signal extractor 43, but the timing of this readout is based on the sufficiently slow angle signal generated by the angle generator 45 with respect to the antenna angle signal 13 from the primary radar 11. is used. This sufficiently slow reading angle signal is input to the signal extractor 43,
The information stored in the memory 42 is slowly read out and sent to the digital communication line 26 via the multiplex transmitter 25.

Regarding the MTI signal 15, the transmitting device and receiving device are the same as in the first embodiment.

In addition, in the currently operated air route monitoring radar system, in addition to the fixed target and moving target video signals of the primary radar as described above, there is an SSR signal from the secondary radar, but this SSR signal is not a moving target video signal. Like signals, the amount of information is small.

Therefore, in this invention, in addition to the antenna angle signal and distance signal, the aircraft identification number and flight altitude information are added to the SSR signal, and the SSR signal is transmitted over a real-time, low-speed digital communication line in the same way as a moving target video signal. It is transmitted using

[Effects of the Invention] This invention separates the radar signal of a surveillance radar into a fixed target video signal based on a fixed target and a moving target video signal based on a moving target, and then converts the signals into digital signals respectively. The video signal is transmitted after time expansion by adding an antenna angle signal, while the digitized moving target video signal is transmitted in real time by adding the antenna angle signal and distance. There is no signal deterioration. Furthermore, since the transmission speed of the fixed target video signal, which has a large amount of information, is reduced, it is possible to use a low-speed digital communication line in the same way as for the moving target video signal, making it possible to significantly reduce line usage charges. I can do it.

In addition, the video signal of the surveillance radar is separated into a fixed target video signal and a moving target video signal, and the fixed target video signal is obtained by extracting the full sweep video signal for one scan every predetermined number of sweeps. Each extracted swept video signal is time-stretched, an antenna angle signal is added to it, and transmitted in one scanning time, and in the next scanning, the transmitted swept video signal is shifted by one to generate the extracted swept video signal. By sequentially extracting every predetermined number of sweeps from the next swept video signal and transmitting it in one scanning time in the same manner as above, all the sweep video signals corresponding to one scanning are transmitted. The transmission speed of the fixed target video signal is reduced, while the moving target video signal is transmitted by adding a distance signal and an antenna angle signal to transmit a full sweep video signal for one scan in one scan time. In this case, signal processing is relatively easy, and the configuration of the entire device can be simplified.

[Brief explanation of the drawing]

1 and 2 show an embodiment of the present invention, in which FIG. 1 is an explanatory diagram showing a fixed target video signal extraction method, and FIG. 2 is a block diagram for implementing the extraction method shown in FIG. 1. 3 are block diagrams showing other embodiments of the present invention. 1...Sweep video signal transmitted 10 seconds ago, 2
...Sweep video signal currently being transmitted, 3...
Sweep video signal transmitted after 10 seconds, 4... Sweep video signal transmitted next to sweep video signal 2,
5... Sweep video signal transmitted next to sweep video signal 3, 11... Primary radar, 12... Fixed target video signal, 13... Antenna angle signal, 14
...Trigger signal, 15...Moving target video signal,
16...first A/D converter, 17...sweep video extractor, 18...first signal synthesizer, 19...
Angle integrator, 20... Angle gate generator, 21...
...Distance integrator, 22...Second A/D converter, 2
3... Signal detector, 24... Second signal synthesizer,
25...Multiple transmitter, 26...Digital communication line, 27...Multiple receiver, 28...First signal separator, 29...Memory, 30...Fixed target signal regenerator, 31...Trigger/ Angle generator, 32...
Second signal separator, 33... Moving target signal regenerator, 34... Radar indicator, 41... First A/
D converter, 42... memory, 43... signal extractor, 44... angle integrator, 45... angle generator.

Claims (1)

[Claims] 1. Separating the radar signal of the surveillance radar into a fixed target video signal based on a fixed target and a moving target video signal based on a moving target, and converting each into a digital signal, and converting the digitized fixed target video into a digital signal. The radar signal is characterized in that the signal is transmitted after time expansion by adding an antenna angle signal, and the digitized moving target video signal is transmitted in real time with the antenna angle signal and the distance signal added. Transmission method. 2. After separating the radar signal of the surveillance radar into a fixed target video signal and a moving target video signal, converting each into a digital signal, and converting the full sweep video signal for one scan including the digitized fixed target video signal, In addition to extracting every predetermined number of sweeps, each extracted sweep video signal is time-expanded, an antenna angle signal is added, and the signals are sequentially transmitted in one scanning time. After one scanning, the swept video signal to be transmitted is Shifting by one, sequentially extracting each predetermined number of sweeps from the sweep video signal located next to the previously extracted sweep video signal, and transmitting in one scanning time in the same manner as above is repeated. , transmitting the full sweep video signal corresponding to one scan, and adding a distance signal and an antenna angle signal to the digitized moving target video signal.
2. The radar signal transmission method according to claim 1, wherein a full sweep video signal for one scan is transmitted in one scan time. 3. A primary radar that separates a fixed target video signal and a moving target video signal and outputs an antenna angle signal and a trigger signal that determines a transmission time, and digitally converts the fixed target video signal and the moving target video signal, respectively. first and second A/D converters for converting into signals; an angle integrator for integrating the antenna angle signal; and generating a gate signal using the antenna angle signal integrated by the angle integrator and the trigger signal. an angular gate signal generator that performs an angular gate signal generator; a swept video signal extractor for extracting a swept video signal from the angle loader; a first signal combiner for combining the integrated antenna angle signal from the angle loader and the extracted swept video signal; a distance integrator that integrates and generates a distance signal; a signal generator that detects a signal of a predetermined level or higher of the digitized moving target video signal from the second A/D converter; a second signal synthesizer that combines the obtained integrated distance signal, the integrated antenna angle signal obtained by the angle integrator, and the moving target video signal detected by the signal detector; 1. A transmitting device comprising: a multiplex transmitting device for sending signals from two signal combiners to a digital communication line; 4. A multiplex receiving device that receives the multiplexed signal from the transmitting device, selects it into a fixed target video signal and a moving target video signal, and outputs the selected signal; The antenna angle signal is separated into the first
a signal separator, and stores the extracted swept video signals including the fixed target video signal sent from the transmitting device in addresses corresponding to the antenna angle signals to generate fixed target video signals for one scan. a second signal separator for separating a moving target video signal, the antenna angle signal and a distance signal from the screened moving target video signal; a trigger/angle generator for generating a trigger/angle signal corresponding to the antenna angle signal from the separator; and a trigger/angle generator for generating a fixed target video signal stored in the memory with the trigger/angle signal from the trigger/angle generator. a fixed target signal generator that sequentially reads out the swept video signals including; a moving target signal generator that reproduces the moving target video signal according to the trigger/angle signal; and a moving target signal generator that synthesizes the reproduced moving target video signal and fixed target video signal, respectively. A receiving device comprising: a radar indicator that displays a radar indicator; 5 After separating the radar signal of the surveillance radar into a fixed target video signal and a moving target video signal, converting each into a digital signal and converting the radar signal into a full sweep video signal for one scan including the digitized fixed target video signal. , antenna angle signals are added and sequentially stored in memories corresponding to the antenna angle signals, and the swept video signals are sequentially read out from the memory using a reading angle signal that is sufficiently slower than the antenna angle signals, and transmitted, and digital 2. The radar signal transmission method according to claim 1, wherein a distance signal and the antenna angle signal are added to a sweep video signal including the converted moving target video signal and transmitted in one scanning time. 6 a primary radar that separates a fixed target video signal and a moving target video signal and outputs an antenna angle signal and a trigger signal that determines a transmission time; and digitally converts the fixed target video signal and the moving target video signal, respectively. first and second A/D converters that convert the signal into signals; an angle integrator that integrates the antenna angle signal; and stores the swept video signal at an address corresponding to the integrated antenna angle signal, respectively. a memory for storing a full sweep video signal including one scan of a fixed target video signal; and a memory for reading out the sweep video signal from the memory sufficiently slow relative to the antenna angle signal from the primary radar. an angle generator that generates an angle signal; a signal extractor that sequentially extracts the sweep video signal stored in the memory using the reading angle signal; and a distance integration unit that integrates the trigger signal to generate a distance signal. a signal detector for detecting a signal of a predetermined level or higher of the digitized moving target video signal from the second A/D converter; and an integrated distance signal obtained by the distance integrator; a signal synthesizer for synthesizing the integrated antenna angle signal obtained by the angle integrator and the moving target video signal detected by the signal detector; and digitally converting the signals from the signal extractor and the signal synthesizer. A transmitting device comprising: a multiplex transmitting device for sending data to a communication line;