JPH02208583A - Moving-target-signal transmitting system and its transceiver - Google Patents

Abstract

PURPOSE:To reduce the capacity of transmission and to make it possible to prevent deterioration of signals by selecting one sweeping signal having the maximum output value among the moving target signals which are detected by suppressing fixed clutters. CONSTITUTION:A radar signal is converted into a digital signal in an A/D converter 2. Fixed clutters in said signal are suppressed with a canceller 3, and only a moving target signal 6 is outputted. N pieces of sweeping signals which are determined in consideration of bearing accuracy and the like among the signals are sequentially inputted into N pieces of doppler filter 4. One signal having the maximum output value and including the target among said signals is selected in a filter selector 5. The signal is outputted from a primary radar 1. Then, the signal higher than a specified level among said signals 6 is detected in a signal detector 10. An antenna angle signal 8 which is computed in an angle computer 12 and a distance signal which is obtained by computing a trigger signal 9 in a distance computer 11 are synthesized in a signal synthesizer 13. The result is sent into a digital communications circuit 15 through a multiplex communications device 14. At this time, the amount of the transmitted data of the signals 6 becomes 1/N, and the allowance for the circuit capacity of the circuit 15 becomes large. Since A/D conversion is performed in the radar only once, the signals are not deteriorated.

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.

[Conventional technology] Currently operating air route monitoring radar systems, etc.
For radar signals from fixed targets, moving targets, etc. of the primary radar, a sweep signal or a part of the sweep signal including the radar signal is extracted at a predetermined sweep interval, and the extracted sweep signal is time-expanded and band-compressed. After that, it is subjected to residual sideband modulation and transmitted over an analog communication line. (Tokuko 1977
-23238) On the receiving side, after being received and demodulated, the time-compressed and extracted sweep signal is 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 predetermined sweep intervals, so the thinned out sweep signal is not transmitted, which causes deterioration of the radar signal on the receiving side. Ta.

In addition, 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. be.

As shown in FIG. 2, the analog radar signal (MTI video signal 58
) is converted into a digital signal by an A/D converter 52, fixed clutter is suppressed by an eraser 53, and only the moving target signal from the moving target 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, a filter selector 55, one sweep signal having the maximum value output containing the target is selected from among the N outputs for each range bin.

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

On the other hand, communication lines in recent years have been transitioning 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 fixed target signal will reduce the amount of information transmitted. is extremely large,
This requires a high-speed digital communication line with a higher transmission rate, which poses problems such as higher line usage charges.

Here, radar signals such as air route monitoring radar are generally classified into fixed target signals from fixed targets and moving target signals from moving targets, but in the case of PPI display such as air route monitoring radar, etc. Since the fixed target signal receives a series of reflected waves every sweep at intervals of about 0.1 degrees, the amount of information becomes 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 not normally used. 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 proposed that the entire sweep signal for l scans including the fixed target signal be extracted at appropriate time intervals and transmitted 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 charges by storing l scanning worth of signals in memory and updating the contents. I applied.

(Japanese Patent Publication No. 63-306943) That is, as shown in FIG. 3, an analog fixed target signal 60 with a large amount of information from the primary radar 51 is converted into a digital signal by an A/D converter 61. On the other hand, primary radar 5
A gate signal for extracting a sweep signal is generated by an angle gate generator 65 using an antenna angle signal obtained by integrating the antenna angle signal 62 from 1 with an angle integrator 63 and a trigger signal 64 indicating the transmission time. It will be done. By this gate signal, the fixed target signal is extracted every predetermined number of sweeps from among all the sweep signals including the fixed target by the sweep signal extractor 66, 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 6 from the primary radar 51
9 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 from the distance integrator 72 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 via a multiplex transmitter 68. 74.

In the receiving device, the signal is received by the multiplex receiving device 75 and separated into a fixed target signal and a moving target signal, and then sent to a signal separator 76.
The antenna angle signal is separated, and 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 signal selected as a moving target signal is separated into an antenna angle signal, a distance signal, and a moving target signal by a signal separator 80, and a moving target signal regenerator 81 separates the signal into an antenna angle signal, a distance signal, and a moving target signal. An analog moving target signal 69 is reproduced from the moving target signal detected based on the trigger/angle signal.

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

[Question 8 to be solved by the invention] As described above, regarding moving target signals with a small amount of information,
The invention previously filed by the inventor employs a method that converts it into a digital signal and transmits it as is in real time over a digital communication line, but the moving target signal may vary depending on the number of target aircraft and the number of aircraft remaining. Since it is not possible to accurately calculate the amount of information, the amount of information is set empirically and a margin is given to this value to determine the line capacity of the digital communication line to be used. 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.

In this way, analog-to-digital conversion is repeated several times, which increases signal deterioration and requires a large number of analog-to-digital converters.

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. , a radar signal transmission method in which an antenna angle signal is added to the antenna angle signal, time-stretched and transmitted, the moving target signal is converted to a digital signal, an antenna angle signal and a distance signal are added, and the radar signal is transmitted in real time. After converting the signal into a digital signal, only the moving target signal is detected by suppressing the fixed clutter, and the desired N sweep signals of the moving target signal are input to each of the N Doppler filters. By selecting one sweep signal having the maximum output from the N outputs of the puller filter and transmitting the digitized moving target signal with a transmission information amount of 17N, the transmission capacity can be reduced and the digital communication line can be used. There is sufficient margin for line capacity.

[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 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 l/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. The amount of transmitted information of the moving target signal at this time is 17H, 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, so signal deterioration is reduced accordingly.

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 signal selected as a moving target signal is separated into an antenna angle signal, a distance signal, and a moving target signal by a signal separator. digital signal is played back. N sweep signals are created from this one sweep signal, smoothed by a smoothing processor, converted to an analog signal by a D/A converter, combined with the reproduced fixed target signal, and displayed on the radar indicator. be done.

[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 system 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, the fixed target signal (N
The LOG system outputs the OR signal) and the moving target signal (MTI
The signal is processed separately from the MTI system that outputs the signal.

In the MTI system, the analog radar signal is converted into a digital signal by the A/D converter 2.

The fixed clutter is suppressed by the eraser 3 and only the MTI 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. Therefore, it can be separated using Doppler filter 4.

Therefore, when N sweep signals are processed at once, N Doppler filters 4 are also required. In this way, if the N sweep signals of the 1MTl signal are sequentially input to the N Doppler filters 4 that separate the Doppler frequencies, the N sweep signals from the Doppler filters 4 are
The N outputs are each 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 information transmitted is 1
/N, which is sent from the primary radar l to the transmission system.

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

A digital MTI signal 6 with a transmission information amount of 1/N of this
is sent from the primary radar 1 to the transmission system.

On the other hand, the primary radar 1 sends out to the transmission system an analog NOR signal 7, an antenna angle signal 8 indicating the antenna angle, and a trigger signal 9 determining the transmission time.

In the transmission system, the digital MTI signal 6 is detected at a predetermined level or higher set by the signal detector 10. 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 a integrator 12 are combined by the signal combiner 13, and the multiplex transmitter 14 is The data is then sent out to the low-speed digital communication line 15 via the digital communication line 15.

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. In the angle gate generator 18, the antenna angle signal 8
Using the antenna angle signal integrated by the angle integrator 12 and the trigger signal 9, a gate signal for extracting a sweep signal every predetermined sweep is output.

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 the signal combiner 19 and sent to the digital communication line 15 via the multiplex transmission device ff114.

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

A trigger/angle generator 22 generates a trigger/angle signal corresponding to the antenna angle signal separated by the signal separator 21. In the moving target signal regenerator 23, the trigger/angle generator 2
Based on the trigger/angle signal from 2, the detected MT
A digital MTI signal for one sweep is reproduced from the I signal.

The smoothing processor 24 accumulates N digital MTI signals for one sweep to create the original N sweep signals.
The signal is converted into an analog MTI signal 6 by the A converter 25, combined with an analog NOR signal 7 to be described later, and displayed on the radar indicator 26.

On the other hand, the signal received by the multiplex receiver 20 and selected as a NOR signal is separated into a sweep video signal and an antenna angle signal by a signal separator 27. The signals are stored in the memory 28 at addresses corresponding to the respective antenna angles.

The fixed target signal regenerator 29 sequentially reads the information stored in the memory 28 and regenerates the analog NOR signal 7, but the timing of this readout is
Trigger/angle generator 22 based on information from the TI signal
A trigger/angle signal corresponding to the antenna angle signal generated by the antenna angle signal is used.

The analog NOR signal 7 reproduced in this way is
As described above, it is combined with the MTI signal 6 and displayed on the radar indicator 26.

In addition, in the air route monitoring radar system currently in operation, 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.
The R signal has a small amount of information, similar to the moving target signal.

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 same real-time and low-speed digital communication line as the moving target signal is used. 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 signals are inputted 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 or the like.

Furthermore, the moving target signal is detected by an MT for detecting only the moving target signal from the analog radar signal received by the primary radar.
The I processing converts the signal into a digital signal, sends it as is to the transmission system, and converts it to an analog signal on the receiving side, so the number of analog-to-digital conversions is reduced, which reduces signal deterioration and reduces the overall configuration of the device. can be simplified.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG.
FIG. 3 shows 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. l ・ ・ ・ 2 ・ Reference ・ 3 II ・ ・ 4 ・ φ ・ 511 ・ ・ 611 ・ ・ 7 ・ ・ ・ 8 ・ ・ ・ 9 ・ ・ Φ 10・Electronic number primary radar A/D converter canceler Doppler filter Filter selector Moving target signal Fixed target signal Antenna Angle signal Trigger signal Signal detector 1 l ・ 12 ・ l 3 ・ l 4 ・ 15 fist 20 ・ 2 l ・ 22 ・ 23 ・ 24 ・ 25 ・ 26 ・ ・Distance integrator・Angle integrator, signal synthesizer, multiplex transmitter, digital communication line red multiplex receiver, signal separator, trigger/angle generator Φ Moving target signal regenerator, smoothing processor, D/A converter, radar indicator

Claims (3)

[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 it. In a radar signal transmission method in which the moving target signal is transmitted with time expansion, the moving target signal is converted into a digital signal, and an antenna angle signal and a distance signal are added and transmitted in real time, the radar signal is converted into a digital signal. After that, the fixed clutter is suppressed to detect only the moving target signal, and the desired N sweep signals of the moving target signals are input to each of the N Doppler filters, and from the N outputs of the Doppler filters. A moving target signal transmission system characterized in that one sweep signal having a maximum output value is selected and the amount of transmission information of the digitized moving target signal is reduced to 1/N and transmitted. (2) an A/D converter that converts the radar signal of the surveillance radar into a digital signal; an eraser that suppresses fixed clutter and outputs only the moving target signal; and an A/D converter that converts the radar signal of the surveillance radar into a digital signal; N Doppler filters that separate Doppler frequencies, and N
a filter selector that selects one sweep signal having a maximum value output that includes a target from among the outputs, and outputs an antenna angle signal indicating an antenna angle and a trigger signal determining a transmission time. a primary radar; a signal detector that detects a signal of a predetermined level or higher from a moving target signal with a transmission information amount of 1/N from the filter selector; and an angle integrator that integrates the antenna angle signal from the primary radar; a distance integrator that integrates trigger signals from the primary radar to generate a distance signal; a distance signal integrated by the distance integrator; an antenna angle signal integrated by the angle integrator; and the signal detector. Claim (1) characterized by comprising: a signal synthesizer for synthesizing the 1/N moving target signal detected by the signal synthesizer; and a multiplex transmitter for sending the signal from the signal synthesizer to a digital communication line. ) Transmitting device described. (3) a multiplex receiver that receives a multiplexed signal from a transmitter, selects it into a fixed target signal and a moving target signal, and outputs the selected signal; and the antenna angle signal and the distance from the selected moving target signal. a signal separator for separating the signal from the antenna; a trigger/angle generator for generating a trigger/angle signal corresponding to the antenna angle signal from the signal separator; and a trigger/angle generator for generating the trigger/angle signal from the trigger/angle generator. a moving target signal regenerator that reproduces one sweep worth of digital signals regarding the moving target as a reference; a smoothing processor that creates N sweep signals from the one sweep worth of digital signals regarding the moving target and performs smoothing processing; A D/A converter that converts the smoothed digital signal regarding the moving target into an analog signal, and a radar indicator that synthesizes and displays the reproduced moving target signal and fixed target signal. The receiving device according to claim (1).