JPH0555822B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a moving target signal transmission system such as an air route monitoring radar and an airport monitoring radar, and its transmitting/receiving device.

[Prior Art] In currently operating air route monitoring radar systems, etc., radar signals from fixed targets, moving targets, etc. of the primary radar are converted into a sweep signal containing the radar signal, or a portion of the sweep signal is The swept signal is extracted at sweep intervals, and after time expansion and band compression, the signal is subjected to vestigial sideband modulation and transmitted over an analog communication line. (Japanese Patent Publication No. 54-23238) On the receiving side, after being received and demodulated, the time-compressed and extracted sweep signals are interpolated to reproduce the radar signal, which is displayed on the radar indicator.

In this way, the sweep signal containing the radar signal is extracted and transmitted at a predetermined sweep interval, so the thinned out sweep signal is not transmitted, so on the receiving side, there is no risk of deterioration of the radar signal. Ta.

In addition, some of the latest airway monitoring radar systems employ HMTI (High Performance MTI), which uses a Doppler filter to detect targets in moving clutter, in order to detect moving targets. .

This is achieved by the primary radar 51 as shown in FIG.
The analog radar signal (MTI video signal 58) received at only is output. Among these moving target signals, N sweep signals that do not deteriorate the azimuth accuracy are collectively input into N Doppler filters 54 in order, and from the N outputs of the Doppler filters 54, the filter selector N per range bin by 55
Among the outputs, one sweep signal having the maximum value output containing the target is selected.

N sweep signals are regenerated by the smoothing processor 56 from this single sweep signal having the maximum value output,
After smoothing processing is performed to give a change in signal level that approximates the antenna pattern, this sweep signal is converted into an analog signal by a D/A converter 57 and sent as a primary moving target signal (MTI signal) 59. It is sent out from the radar 51 to the transmission system and transmitted via an analog communication line.

On the other hand, communication circuits in recent years have shifted from analog communication lines to digital communication lines, and it is now necessary to transmit radar signals such as air route monitoring radar using digital communication lines.

Therefore, if the analog band compression signals that are currently transmitted over analog communication lines are digitized and transmitted as is, the problem of radar signal deterioration will be solved, but the amount of information transmitted for fixed target signals will be reduced. Since it is extremely large, a high-speed digital communication line with a correspondingly high transmission rate is required, leading to problems such as high line usage fees.

Here, in general, radar signals such as air route monitoring radar include a fixed target signal from a fixed target,
It is broadly divided into moving target signals from moving targets.
In the case of PPI display such as air route monitoring radar, fixed target signals receive a series of reflected waves 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, a high-speed digital communication line is required to transmit digital fixed target signals as they are in real time.

On the other hand, since a moving target signal is a radar signal that selects only the reflected waves from a moving target, its amount of information is much smaller than that of a fixed target signal, and its occupied frequency bandwidth is correspondingly smaller, making it suitable for low-speed digital communication. It can be transmitted in real time over the line.

Furthermore, since moving target signals are used for constant air traffic control, they must be transmitted in real time, whereas fixed target signals are usually not used for direct air traffic control, and systems such as air route monitoring radars are required to operate normally. Since it is used to confirm whether or not the data is being used with a fixed target, there is no need to transmit it in real time.

Therefore, since almost the same fixed target signal is received in each scan, the inventor decided to extract the entire sweep signal for one scan including the fixed target signal at appropriate time intervals and transmit it over time. On the receiving side, we have developed a radar signal transmission method that allows the use of digital communication lines with low transmission speeds and reduces line usage fees by storing one scan's worth of signals in memory and updating the contents. I applied.
(Special Publication No. 63-306943) In other words, as shown in FIG. 3, the analog fixed target signal 60 with a large amount of information from the primary radar 51
is converted into a digital signal by the A/D converter 61. On the other hand, an angle gate generator 65 extracts a sweep signal using an antenna angle signal obtained by integrating the antenna angle signal 62 from the primary radar 51 by an angle integrator 63 and a trigger signal 64 indicating the transmission time. A gate signal is created. Based on this gate signal, the fixed target signal is extracted by the sweep signal extractor 66 from all the sweep signals including the fixed target every predetermined number of sweeps, and after the extracted sweep signal is time-stretched, it is combined with this signal. The integrated antenna angle signals are combined by a signal combiner 67 and sent out via a multiplex transmitter 68.

On the other hand, the analog moving target signal 69 from the primary radar 51 is converted into a digital signal by the A/D converter 70, and then a signal of a certain level is detected by the signal detector 71. The integrated distance signal and the integrated antenna angle signal from the angle integrator 63 are combined by a signal combiner 73 and sent to a low-speed digital communication line 74 via a multiplex transmitter 68.

In the receiving device, it is received by the multiplex receiving device 75,
After being sorted into fixed target signals and moving target signals,
The antenna angle signal is separated by a signal separator 76,
The fixed target signal for one scan, that is, the entire sweep signal, is stored in the memory 77 corresponding to the antenna angle signal. The information stored in this memory 77 is read out sequentially by trigger/angle signals for reproduction based on the antenna angle signal from the trigger/angle generator 79, and is read out sequentially by the trigger/angle signal for reproduction based on the antenna angle signal from the trigger/angle generator 79. Signal 60 is played back.

On the other hand, the signals selected as moving target signals are
The signal separator 80 separates the antenna angle signal, distance signal,
The analog moving target signal 69 is recovered from the moving target signal detected by the moving target signal regenerator 81 based on the trigger/angle signal for reproduction from the trigger/angle generator 79.

The analog fixed target signal 60 and moving target signal 69 thus reproduced are combined and displayed by the radar indicator 82.

[Problems to be Solved by the Invention] As described above, regarding moving target signals with a small amount of information, the inventor previously applied for a method in which the signals are converted into digital signals and transmitted as they are in real time over a digital communication line. However, since it is not possible to accurately calculate the amount of information for a moving target signal due to the number of target aircraft and the number of aircraft remaining, we set the amount of information empirically and calculated this value. The line capacity of the digital communication line to be used is determined by giving a margin to the line capacity. However, in the case of special meteorological conditions such as a typhoon, the amount of unused data increases, and there is a risk that the capacity of the digital communication line in use may be exceeded.

Furthermore, the analog radar signal received by the primary radar 51 is converted to digital in order to detect only the moving target signal, further converted to analog and sent to the transmission system, where it is converted to digital again. The signal is then transmitted and converted back into an analog signal by the receiving device.

Since analog-to-digital conversion is performed several times in this way, signal deterioration increases accordingly, and a large number of analog-to-digital converters are required.

The present invention provides a moving target signal transmission method that can reduce the amount of transmitted information of a moving target signal to ensure sufficient line capacity of a digital communication line, has little signal deterioration, and has a simple equipment configuration. The purpose is to provide a transmitting/receiving device.

[Means for Solving the Problem] The present invention separates a radar signal of a surveillance radar into a fixed target signal from a fixed target and a moving target signal from a moving target, and then converts the fixed target signal into a digital signal. , in a radar signal transmission method in which an antenna angle signal is added to the antenna angle signal and transmitted after time expansion, the moving target signal is converted to a digital signal, and an antenna angle signal and a distance signal are added and transmitted in real time. After converting the radar signal into a digital signal, it suppresses fixed clutter and detects only the moving target signal.
Of these moving target signals, desired N sweep signals are input to N Doppler filters, and one sweep signal having the maximum value output is selected from the N outputs of the Doppler filters. By reducing the transmission information amount of the digitized moving target signal to 1/N and transmitting it, the transmission capacity is reduced and a sufficient margin is provided for the line capacity of the digital communication line.

[Operation] The radar signal of the surveillance radar is converted into a digital signal by an A/D converter, fixed clutter is suppressed by an eraser, and only a moving target signal is output. Among these output moving target signals, N sweep signals determined in consideration of azimuth accuracy, etc. are collectively input to N Doppler filters that separate the Doppler frequencies, respectively. From the N outputs of the filter, one sweep signal having the maximum value output and containing the target is selected by the filter selector and output from the primary radar. The primary radar further outputs a fixed target signal, an antenna angle signal indicating the antenna angle, and a trigger signal that determines the transmission time.

In the transmission system, the moving target signal, which is extracted from the filter selector and has a transmission information amount of 1/N, is detected by a signal detector at a predetermined level or higher, and is integrated with the antenna angle signal, A distance signal obtained by integrating trigger signals from the primary radar is combined and sent to a digital communication line via a multiplex transmitter. At this time, the amount of transmitted information of the moving target signal becomes 1/N, and the margin of line capacity of the digital communication line becomes large.

A/D conversion is performed only once for MTI processing (moving target detection processing) within the primary radar, and is sent as a digital signal to the transmission system, which reduces signal deterioration.

For fixed target signals with a large amount of information from the primary radar, an angle gate generator generates a sweep signal using the antenna angle signal obtained by integrating the antenna angle signals from the primary radar and a trigger signal indicating the transmission time. A gate signal is created to extract the . The fixed target signal is generated by this gate signal.The sweep signal extractor extracts a signal every predetermined number of sweeps from among all the sweep signals including the fixed target.After this extracted sweep signal is time-stretched, and the integrated antenna angle signal are combined by a signal combiner and sent out via a multiplex transmitter, thereby reducing the transmission speed of the fixed target signal and making it possible to use a low-speed digital communication line.

In the receiving device, after being received by the multiplex receiving device and sorted into fixed target signals and moving target signals, the fixed target signal for one scan, that is, the entire sweep signal, is stored in a memory corresponding to the antenna angle signal. . The information stored in this memory is sequentially read out using a reproduction trigger/angle signal based on the antenna angle signal, and the fixed target signal is reproduced.

On the other hand, the signals selected as moving target signals are
A signal separator separates the signal into an antenna angle signal, a distance signal, and a moving target signal, and a moving target signal regenerator reproduces a digital signal for one sweep based on the trigger/angle signal for reproduction. In the smoothing processor,
From this digital signal for one sweep, N sweep signals are created, smoothed, converted to analog signals by a D/A converter, combined with the reproduced fixed target signal, and displayed on the radar indicator. .

[Example] An example of the present invention will be described in detail based on FIG.

FIG. 1 shows a block diagram of an air route monitoring radar system using the moving target signal transmission method according to the present invention, in which an analog radar signal received by the primary radar 1 is converted into an intermediate frequency signal. After that, they are processed separately into a LOG system that outputs a fixed target signal (NOR signal) and an MTI system that outputs a moving target signal (MTI signal).

In the MTI system, analog radar signals are converted to digital signals by A/D converter 2, and then
Fixed clutter is suppressed by eraser 3 and MTI
Only the signal is detected.

Here, it is considered that reflected wave pulses from a certain position (a certain direction and distance) occur continuously for a certain number of sweep signals, so the Doppler frequency shift remains the same during this period. Therefore, when performing Doppler filter processing to detect a moving target signal, if signal sequences are extracted in the azimuth direction while keeping the distance constant for a certain number of sweep signals, these signal sequences will have the same Doppler component. can be separated using Doppler filter 4.

Therefore, if N sweep signals are processed at once, N Doppler filters 4 are also required. In this way, if the N sweep signals of the MTI signal are sequentially input to the N Doppler filters 4 that separate the Doppler frequencies,
The N outputs from this Doppler filter 4 are
Each is separated into N Doppler frequencies. Therefore, the filter selector 5 selects the sweep signal having the maximum value output and including the target from the N outputs of the Doppler filter 4. This selected output is a digitized MTI signal,
The amount of transmitted information is 1/N, and this is sent from the primary radar 1 to the transmission system.

In reality, based on experience, the number of consecutive sweep signals is about 13 reflected pulses, and an appropriate value for N is 6 to 8, as long as the azimuth accuracy does not deteriorate. .

Digital data transmission with 1/N of this amount of information
The MTI signal 6 is sent from the primary radar 1 to the transmission system.

On the other hand, from primary radar 1, analog NOR
Antenna angle signal 8 indicating signal 7 and antenna angle
and a trigger signal 9 that determines the transmission time are sent to the transmission system.

In the transmission system, the digital MTI signal 6 is
A signal of a predetermined level or higher set by the signal detector 10 is detected. This detected signal, the distance signal obtained from the trigger signal 9 by the distance integrator 11, and the antenna angle signal integrated by the angle integrator 12 are combined by the signal combiner 13, and then transmitted via the multiplex transmitter 14. Low speed digital communication line 15
sent to.

At this time, since the amount of transmitted information of the MTI signal 6 is 1/N, the line capacity margin of the digital communication line 15 is large.

On the other hand, the NOR signal 7 sent to the transmission system as an analog signal from the primary radar 1 is converted into a digital signal by the A/D converter 16 and sent to the sweep video extractor 17. Angle gate generator 1
8, the antenna angle signal 8 is integrated by the angle integrator 12 and the trigger signal 9 is used to output a gate signal for extracting a sweep signal every predetermined sweep.

The gate signal from the angle gate generator 18 is input to the sweep video extractor 17, and the gate signal extracts the digitized NOR signal every predetermined sweep. The extracted sweep signal and the antenna angle signal integrated by the angle integrator 12 are combined by a signal combiner 19 and sent to the digital communication line 15 via the multiplex transmitter 14.

On the receiving side, it is received by the multiplex transmitter 20,
The signal selected as an MTI signal is detected as an antenna angle signal and a distance signal by the signal separator 21.
Separated into MTI signal.

The trigger/angle generator 22 generates a trigger/angle signal corresponding to the antenna angle signal separated by the signal separator 21.
Create an angle signal. In the moving target signal regenerator 23,
Based on the trigger/angle signal from the trigger/angle generator 22, a digital MTI signal for one sweep is reproduced from the detected MTI signal.

In the smoothing processor 24, one sweep of digital
The original N sweep signals from the MTI signal are created, smoothed, converted into an analog MTI signal 6 by the D/A converter 25, and combined with an analog NOR signal 7, which will be described later. displayed on the indicator 26.

On the other hand, the signal received by the multiplex receiver 20 and selected as a NOR signal is sent to the signal separator 27.
After being separated into a swept video signal and an antenna angle signal, each swept video signal is divided into one scanning portion.
The NOR signals are stored in the memory 28 at addresses corresponding to the respective antenna angles.

The fixed target signal regenerator 29 sequentially reads out the information stored in the memory 28 and generates an analog signal.
The NOR signal 7 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 22 based on information from the MTI signal.

The analog NOR signal 7 thus reproduced is combined with the MTI signal 6 and displayed on the radar indicator 26, as described above.

In addition, in the currently operated air route monitoring radar system, in addition to the fixed target and moving target signals of the primary radar as described above, there is an SSR signal from the secondary radar, but this SSR signal is similar to the moving target signal. The amount of information is small.

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

[Effects of the Invention] In the present invention, after separating the radar signal of a surveillance radar into a fixed target signal from a fixed target and a moving target signal from a moving target, the fixed target signal is converted into a digital signal, and the fixed target signal is converted into a digital signal. In the radar signal transmission method, an angle signal is added and transmitted after time expansion, a moving target signal is converted to a digital signal, and an antenna angle signal and a distance signal are added and transmitted in real time. After converting it into a signal, fixed clutter is suppressed to detect only the moving target signal, and N desired sweep signals of the moving target signal are input to N Doppler filters, respectively. By selecting one sweep signal with the maximum value output from N outputs, the amount of information to be transmitted of the digitized moving target signal is reduced to 1/N, so the amount of information to be transmitted is reduced to 1/N, so the digital communication being used The margin of line capacity is increased. Therefore, there is no danger that the line capacity will be exceeded due to an increase in unused data due to special weather conditions.

In addition, the moving target signal is converted into a digital signal by MTI processing to detect only the moving target signal from the analog radar signal received by the primary radar, and then sent as is to the transmission system and converted to an analog signal on the receiving side. Since the number of analog-to-digital conversions is small, signal deterioration is reduced accordingly, and the configuration of the entire device can be simplified.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of this invention.
2 and 3 show a conventional example. FIG. 2 is a block diagram showing moving target signal processing within the primary radar, and FIG. 3 is a block diagram showing the entire device. 1...Primary radar, 2...A/D converter, 3...
... Eraser, 4 ... Doppler filter, 5 ... Filter selector, 6 ... Moving target signal, 7 ... Fixed target signal, 8 ... Antenna angle signal, 9 ... Trigger signal, 10 ... Signal detection 11...Distance integrator, 12...Angle integrator, 13...Signal synthesizer,
14...Multiple transmitter, 15...Digital communication line, 20...Multiple receiver, 21...Signal separator, 22...Trigger/angle generator, 23...Moving target signal regenerator, 24...Smoothing Processor, 25...
D/A converter, 26...radar indicator.

Claims (1)

[Claims] 1. After separating the radar signal of the surveillance radar into a fixed target signal from a fixed target and a moving target signal from a moving target, the fixed target signal is converted into a digital signal, and an antenna angle signal is added to the fixed target signal. The moving target signal is converted into a digital signal and transmitted after time expansion.
In a radar signal transmission method in which an antenna angle signal and a distance signal are added and transmitted in real time, after converting the radar signal into a digital signal,
Fixed clutter is suppressed to detect only the moving target signal, and N desired sweep signals of the moving target signal are input to N Doppler filters, and from the N outputs of the Doppler filters. A method for transmitting a moving target signal, characterized in that the amount of transmitted information of the moving target signal is reduced to 1/N by selecting one sweep signal having a maximum value output, digitizing it, and transmitting it. 2 After separating the radar signal of the surveillance radar into a fixed target signal from a fixed target and a moving target signal from a moving target, the fixed target signal is converted into a digital signal, and an antenna angle signal is added to it for time expansion. and transmit the moving target signal, converting the moving target signal into a digital signal,
A radar signal transmitting device that adds an antenna angle signal and a distance signal and transmits them in real time, comprising an A/D converter that converts the radar signal of the monitoring radar into a digital signal, and an A/D converter that suppresses fixed clutter and transmits the an eraser that outputs only the moving target signal; N Doppler filters that separate Doppler frequencies from the N sweep signals of the moving target signal; 1 with the maximum output value
a primary radar having a filter selector that selects a sweep signal and outputs an antenna angle signal indicating an antenna angle and a trigger signal that determines a transmission time; and an amount of information transmitted from the filter selector 1/ a signal detector that detects a signal of a predetermined level or higher from the N moving target signals; an angle integrator that integrates antenna angle signals from the primary radar; and generates a distance signal by integrating the trigger signal from the primary radar. a distance integrator that combines the distance signal integrated by the distance integrator, the antenna angle signal integrated by the angle integrator, and the 1/N moving target signal detected by the signal detector. A transmitter comprising: a signal synthesizer; and a multiplex transmitter that sends signals from the signal synthesizer to a digital communication line. 3 After separating the radar signal of the surveillance radar into a fixed target signal from a fixed target and a moving target signal from a moving target, the fixed target signal is converted into a digital signal, and an antenna angle signal is added to it for time expansion. The amount of transmitted information of the moving target signal is reduced to 1/N, and this is converted into a digital signal, and an antenna angle signal and a distance signal are added to receive the radar signal transmitted in real time. The receiving device receives the multiplexed signal from the transmitting device, and
a multiplex receiver that selects and outputs the fixed target signal and a moving target signal with a transmission information amount of 1/N; and a signal separation device that separates the antenna angle signal and the distance signal from the selected moving target signal. a trigger/angle generator for generating a trigger/angle signal corresponding to the antenna angle signal from the signal separator; a moving target signal regenerator that reproduces a digital signal for a sweep; a smoothing processor that generates N sweep signals from the digital signal for one sweep related to the moving target and performs smoothing processing; and a smoothing processor that performs smoothing processing. A receiving device comprising: a D/A converter that converts a digital signal related to a target into an analog signal; and a radar indicator that combines and displays the reproduced moving target signal and fixed target signal.