JPH11326493A - Radar video transmission device, digital transmitter and receiver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To minimize a line maintenance cost by performing data compression processing on only a noise signal and a clutter signal by respectively separating a target signal, the noise signal and the clutter signal without degrading a quality (resolution of an aircraft) of a radar video. SOLUTION: In a signal requiring a high quality (resolution) among an aircraft signal, a noise signal and a clutter signal 30 contained in a radar video, the radar video is respectively separated into the aircraft signal, the noise signal and the clutter signal 30, and a data quantity of noise signal and clutter signal 30 part is compressed to reduce transmission capacity. Since the noise signal reduces resolution and is originally low amplitude, a superordinate bit becomes useless, the redundant element is compressed, and the cutter signal 30 is constituted so as to renew a signal according to a movement of a clutter without reducing resolution and without being transmitted in real time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for transmitting radar video to an air traffic control station in a remote place, and more particularly to a radar video transmission apparatus, a digital transmission apparatus, and a reception apparatus having a digital transmission function using a low transmission capacity line. About.

[0002]

2. Description of the Related Art When transmitting radar video through a digital line, an analog signal has been transmitted to a remote place via a coaxial cable or an optical cable. However, due to the trend of digitization of lines, it has become necessary to transmit radar video via digital lines.

In this case, in order to transmit radar video with the same quality as in analog transmission, it is necessary to carry out A / D conversion at the sampling clock frequency and the number of amplitude bits necessary for a system used in a remote place, and to perform digital transmission. .
In the case of an airline surveillance radar, the required capacity of the digital line is about 5 Mbps.

Various digital compression systems have been invented for TV images and the like. However, in the case of radar video, signal generation timing, level, generation period input / output interface, and fundamental properties of signals such as correlation are different. However, data compression is not possible with TV image compression. Also, radar video is used not only for display but also for other computer information processing such as target detection (aircraft position detection) existing in the video. , Does not stand use.

[0005] For this reason, a new scheme is required according to the nature of radar video.

[0006]

The problem is that when radar video is transmitted over a digital line, the cost of maintaining the line usage fee is too high due to the enormous transmission capacity. The reason will be described below. Figure 12 shows the outline of the radar video to be transmitted.

When digitally transmitting radar video to a remote place, it is necessary to perform A / D conversion on a sweep signal (scanning radially around a display point (radar)) unit shown in FIG. 12 and transmit the digital signal as a digital signal. There is. One screen on the display device is such that the sweep scans several thousand lines. The number of sweeps is determined by the transmission trigger repetition frequency (generally referred to as PRF) of the radar and the number of rotations of the radar antenna per revolution.
When F is 300 pps (transmitting 300 pulses per second) and the antenna makes one rotation in 10 seconds, the number of sweeps is 300 pps × 10 s = 3000.

[0008] The required transmission line capacity when digitizing this one-sweep signal and transmitting it in real time can be easily calculated. The calculation formula is shown below. However, this is merely an example, and is arbitrarily calculated based on the distance resolution, the video amplitude bit, and the coverage area.

Here, the following preconditions are set and calculated. Calculation conditions Coverage: 200 NM, distance resolution (synonymous with sampling clock frequency): 1/10 NM, video amplitude bit number: 8 bits In this case, the data amount when one sweep is digitized is (coverage / distance resolution) X number of video amplitude bits), when transmitting radar video in real time, it is obtained by multiplying the number of sweeps during one rotation and dividing by the antenna rotation time. Specifically, numerical values are as follows.

[0010] Radar video transmission capacity = (200NM ÷)
(1 / 10NM × 8 bits) × 3000 lines / 10 seconds = 4.
8 Mbps As described above, a line capacity of at least 4.8 Mbps is required, which is equivalent to 75 voice lines (64 kbps). It is clear that the maintenance cost is enormous because one type of radar video transmission line requires the same amount as the telephone line maintenance cost for 75 lines.

The present invention is an apparatus aimed at minimizing the line maintenance cost. Among the parameters shown in the above calculations, the distance resolution, the number of video amplitude bits, and the transmission time are all determined by the requirements of a system used in a remote place because the object is an aircraft. However, the radar video includes not only an aircraft signal (referred to as a target signal) but also a receiver noise signal and a clutter signal as shown in FIG. The noise signal is
Since the dynamic range (S / N ratio) needs to be increased, the amplitude is set lower than the target signal.

For example, when the target signal has a maximum of 2V, the noise signal is set to about 0.3V. Also, the distance resolution does not need to be as precise as an aircraft. The clutter signal also has the same amplitude as the target signal, but the distance resolution is not required to be as precise as an aircraft, and the movement is much slower (ground clutter has zero movement,
(Indicating that weather clutter moves slowly), the signal update need not be similar to an aircraft.

That is, it is found that the transmission capacity as shown by the above formula has the following redundant parts. Regarding the noise amplitude bits, the higher-order bits are always 0 based on the amplitude distribution characteristics, but the bits are transmitted with the same number of bits as the aircraft. Since the distance resolution of noise and clutter is too fine, there is unnecessary data.

[0014] The clutter updates the screen at a fast cycle (the same update cycle as the video of the aircraft) despite the slow movement. When the ratio of the entire target signal is calculated, it can be calculated by the following equation. The data amount of the video of the aircraft portion shown in FIG. 12 is calculated below.

The width of the reflected signal from the aircraft is determined by the beam width of the radar, and approximately 30 hits can be obtained. That is, the reflection signal of the same aircraft is displayed at a certain position on the display with a spread of 30 sweeps. Further, the thickness (depth) of the video blip is widened by the transmission pulse width of the radar or about twice, and the distance resolution is usually set to about 1/2 of the transmission pulse width. When A / D conversion is performed using this clock, up to four 8-bit A / D conversion data are generated for one aircraft.

As described above, the data amount of one aircraft is 8
Bit × 4 × 30 hits = approximately 960 bits. If data is transmitted when 400 aircraft are present in one screen, the transmission capacity is 960 bits x 4
00 units / 10 seconds = 38.4 kbps, which is about 0.8% compared to the total transmission capacity of 4.8 Mbps.

The data amount of the aircraft is about 40 kb from the above.
ps. From these, the data capacity of the noise signal and the clutter signal, which are other components of the radar video, is 4.8 Mbps-40 kbps = 4.7.
6 Mbps, which indicates that almost all of the total data capacity is configured. For this reason, it has been found that the capacity of 4.8 Mbps is obtained by transmitting a signal that does not need high accuracy for a signal of about 1% (only an aircraft signal) with the same accuracy.

The present invention focuses on the properties of a noise signal and a clutter signal, and realizes a reduction in transmission capacity by eliminating a redundant portion of the data amount of these signals which originally have excessive quality. At the same time, improve transmission efficiency, reduce line maintenance cost, and improve performance, miniaturization, weight reduction, high speed, low power consumption, high integration, simplification of circuit and device configuration, security improvement, and reliability. It is an object of the present invention to provide a radar video transmission device, a digital transmission device, and a reception device capable of improving operability, operability, productivity, maintainability, and resource reusability.

[0019]

In order to achieve the above object, a radar video transmission apparatus, a digital transmission apparatus and a reception apparatus according to the present invention transmit radar video in a low transmission capacity digital transmission apparatus. Side, scan integration means for extracting only the clutter signal from the radar video, video difference means for subtracting the clutter signal portion from the radar video to generate only an aircraft signal and a noise signal, and an aircraft signal from the difference signal. A target / noise separating unit for separating a noise signal, a target data generating unit for extracting azimuth information and amplitude information from the separated target signal to generate target data, and a data number by thinning out range bin data from the separated noise signal. Noise data range bin decimation means for reducing the noise signal Noise data high-order bit thinning means for removing high-order bits and outputting only low-order bits; noise data generating means for adding noise information to the output noise data to generate noise data; and A clutter data range bin thinning unit for reducing the number of clutter signal data by the same operation as the range bin thinning, a clutter data sector dividing unit for storing the clutter data for one scan, and dividing and outputting the one scan data; It comprises clutter data generating means for generating and outputting clutter data by adding azimuth information to a clutter signal, and video multiplexing means for multiplexing and transmitting the target data, noise data and clutter data for each signal of the same azimuth. And the receiving side, based on the received data, Video separating means for separating target data, noise data and clutter data, a target data buffer memory for temporarily buffering target data, and a target signal reproduction for decoding distance information and amplitude information from the target data to reproduce a target signal Means, a noise data buffer memory for temporarily buffering noise data, a noise data range bin reproducing means for interpolating a range bin to the noise data and returning to the number of range bins before thinning out, and uniformly adding upper bits and setting the number of amplitude bits to A. A noise data range bin reproducing means for returning to the state of / D conversion, a clutter data sector synthesis memory for sequentially storing the clutter data divided and transmitted according to its azimuth information, and a range bin before thinning out the range bins by interpolation. Clutter data to return to number And a radar video synthesizing unit that non-additively synthesizes the reproduced target signal, noise signal, and clutter signal in sweep units, and reproduces and outputs the original radar video.

Further, the apparatus further comprises D / A conversion means, wherein the output of the radar video synthesizing means is input to the D / A conversion means and can be output as an analog signal to the outside. Also, a radar video, low transmission capacity digital transmission device, a scan integrator for extracting only a clutter signal from the radar video, and a signal of only an aircraft signal and a noise signal by subtracting a clutter signal portion from the radar video. A video difference means for generating, a target / noise separation means for separating an aircraft signal and a noise signal from the difference signal, a target data generation means for extracting azimuth information and amplitude information from the separated target signal to generate target data, Similarly, noise data range bin thinning means for thinning out range bin data from the separated noise signal to reduce the number of data, noise data high order bit thinning means for removing the high order bit of the noise signal and outputting only the low order bit, Add azimuth information to the noise data, Noise data generating means for generating data, clutter data range bin thinning means for reducing the number of data of clutter signals from the clutter signal by the same operation as the range bin thinning of the noise signal, and storing the clutter data for one scan; Clutter data sector dividing means for dividing and outputting the data for one scan, clutter data generating means for generating and outputting clutter data by adding azimuth information to the clutter signal, and using the same target data, noise data and clutter data And video multiplexing means for multiplexing and transmitting each azimuth signal.

[0021] Also, a low-capacity digital receiver for radar video, a video separating means for separating received data into target data, noise data and clutter data, and a target data buffer for temporarily buffering the target data A memory, a target signal reproducing means for decoding distance information and amplitude information from the target data and reproducing the target signal, a noise data buffer memory for temporarily buffering the noise data, and a range bin interpolated and thinned out for the noise data A noise data range bin reproducing means for returning the number of range bins to the previous number, a noise data range bin reproducing means for uniformly adding upper bits and returning the number of amplitude bits to the state of A / D conversion, and clutter data divided and transmitted. Clutter that sequentially stores according to the azimuth information Clutter data range bin reproducing means for interpolating the reduced range bins to return to the number of range bins before thinning, and non-adding and synthesizing the reproduced target signal, noise signal and clutter signal in sweep units to obtain the original radar video And a radar video synthesizing means for reproducing and outputting the same.

With the above configuration, the noise signal is once A
The noise data sampled by the / D conversion means is thinned out (the same processing as reducing the resolution of the sampling clock), and the upper bits of the A / D conversion amplitude bits due to low amplitude (the upper bits are always fixed to 0) The amount of data of the noise signal is reduced, and the clutter signal reduces the amount of data by the same thinning process and the movement is much slower than that of an aircraft (ground clutter 0, indicating that the weather clutter moves slowly), so that the signal update time (indicating the update time of one display screen) is delayed according to the amount of movement, and the clutter signal occupying in the transmission data is reduced. The data transmission capacity is reduced by reducing the ratio of the data transmission, thereby realizing a low transmission capacity.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The basic operation of a radar video transmission device, a digital transmission device and a reception device according to the present invention will be described with reference to the configuration of FIG. After the radar video is converted into a digital signal by the A / D conversion means, it is input to the "scan integration means (1)" and the "video difference means (2)".

In the "scan integration means (1)", FIG.
The sweep signals in the same direction shown in FIGS. 2A and 2B are added for several scans to generate the signal shown in FIG. This added signal (FIG. 2 (c)) is divided by the added scan number to generate an averaged signal shown in FIG. 2 (d). A threshold level (FIG. 2 (e)) is set for this averaged signal, and only a clutter signal above the threshold level is extracted.

The signal at this time is generated for each sweep as shown in FIG. 2 (f) and output as a clutter signal (21). "Video difference means (2)" is a clutter signal (21) output from scan integrator (1) in response to a sweep signal (FIG. 3 (a)) output from the A / D converter (FIG. 3 (b)). Then, a difference signal (22) shown in FIG.

The difference signal (22) includes only a noise signal and a target signal. The "target / noise separating means (3)" sets the threshold level shown in FIG. 3 (d) for the difference signal (22), and sets the target signal (FIG. 3 (e)) having the threshold level or higher. The target signal (23) and the noise signal (24) are separated into noise signals (FIG. 3 (f)) below the level.

"Target data generating means (4)"
For the target signal (23) (FIG. 4 (a)), the distance of the target signal is calculated using a clock having the resolution required by the user, and target data (25) as shown in FIG. 4 (c) is generated. And output. The “noise data range bin thinning means (5)” outputs the noise signal (2) shown in FIG.
For 4), the data amount is reduced.

In the A / D conversion, a noise signal (FIG. 3 (f)) obtained by sampling at a distance resolution having an accuracy required by a user is converted into a range bin thinning concept shown in FIG. Data is extracted at regular intervals. Figure-
In the case of the example No. 5, the A / D converted data of FIG. 5A is extracted at one data skip interval in FIG. 5B.

This operation reduces the data amount by half.
In the extracted noise data (26), the "noise data upper bit thinning means (6)" deletes the upper bits uniformly and outputs only the lower bits. High-order bit thinning is
The operation is as follows. When 2V is A / D converted by 4 bits, noise less than 0.5V is represented by any of the following four patterns.

When the amplitude is 0 V: (MSB) 0000 (LSB) When the amplitude is 0.125 V: (MSB) 0001 (LSB) When the amplitude is 0.25 V: (MSB) 0010 (LSB) When the amplitude is 0.375 V: (MSB) 0011 (LSB) When the amplitude is 0.50 V: (MSB) 0100 (LSB) Since the noise is always set to less than 0.5 V, 000
It is represented by any one of bits 0, 0001, 0010, and 0011. In this case, since the upper two bits are constant at 00, this part is deleted and only the lower two bits are output.

This indicates that since the upper two bits are known, 4-bit data can be reproduced by adding the upper two bits uniformly to the lower two bits on the receiving side at 00. The noise signal of only the lower bits is grouped in sweep units by the "noise data generating means (7)", and is added as azimuth information and output as noise data. The clutter signal (21) output from the scan integrator (1) (FIG. 2)
(F)) is a "clutter data range bin thinning means (8)", which outputs a reduced amount of data by the same operation as in the case of the noise signal described above. FIG. 5 illustrates the operation.

The thinned clutter signal is temporarily stored in "clutter data sector dividing means (9)". The "clutter data sector dividing means (9)" has an internal memory and divides the display screen into sectors at equal angular intervals based on the azimuth signal as shown in FIG. Are sequentially stored.

For example, if the azimuth signal is one rotation of the antenna (36
In the case of a system in which 4096 pulses are output at 0 degree rotation), a sector memory divided into 4096 is provided, and a clutter signal is stored in a memory in a sector area corresponding to the direction of the signal. The call timing from the memory is an azimuth reference signal output from the antenna (a signal output one pulse at the timing when the antenna faces magnetic north, ARP
Called. ) Is output, a clutter signal for only a few sectors is output.

When the ARP is input during the next rotation, a clutter signal of a different sector is output for one sector. This works sequentially and repeatedly. FIG. 7 shows the concept of the operation. The "clutter data generation means (10)" generates and outputs clutter data by adding a sector number.

The "video multiplexing means (11)" multiplexes the target data, noise data and clutter data generated as described above in sweep units and transmits the multiplexed data. Figure 8 shows the transmission concept. The clutter data is
As described above, since the output is sequentially performed for each scan at the timing shown in FIG. 7, the transmission format is such that when the sweep signal that matches the direction of the clutter signal to be transmitted is transmitted as shown in FIG. The clutter data is multiplexed on the noise data and the target data.

On the receiving side, the video multiplexed data transmitted by the operation of FIG. 8 is received by the "video separating means (12)", separated into target data, noise data and clutter data, and outputted. . The target data is temporarily stored in the “target buffer memory (13)”.

The target data output from the "target buffer memory (13)" is decoded by the "target signal reproducing means (14)" (FIG. 4 (d)), and the range clock is used. The target signal is reproduced at the calculated position, and the target signal (27) (FIG. 10 (c)) in sweep units shown in FIG. 4 (e) is output.

The noise data is temporarily stored in the "noise data buffer memory (15)", and is then stored in the "noise data range bin reproducing means (16)" as shown in FIG.
Is interpolated by the thinned-out noise data as shown in FIG. 5D, and the data amount is adjusted to that before the thinning-out. Noise data (2
8) "Noise data upper bit addition means (17)"
Then, the upper bits of the number of deleted bits are added in a data format of 0, the number of amplitude bits of the noise data is uniformly reproduced, and the noise signal (29) is reproduced and output in sweep units.

The interpolation of the range bin works as shown in FIG. However, since FIG. 5 shows a case where data is skipped by skipping one data, the interpolation on the receiving side doubles each data and restores the entire data amount. The clutter data is stored in the "clutter data sector synthesis memory (18)".
The clutter data is stored in the sector memory in the same direction.

Since the clutter data is sequentially transmitted for each scan, the clutter data has the effect of sequentially increasing the data stored in the sector memory. Fig. 9 shows the concept of operation. For example, in a case where only one sector is transmitted in one scan in the case of dividing 4096 sectors, one screen is completed on the receiving side after 4096 scans. The clutter data sector combining memory (18) outputs clutter data while retaining data.

The output clutter data is reproduced by the "clutter data range bin reproducing means (19)" by the same operation as the above-described noise signal range bin reproducing operation. The outline of the operation is the same as in FIG. Each reproduced target signal (27) (FIG. 10)
(C)), the noise signal (29) (FIG. 10 (b)) and the clutter signal (30) (FIG. 10 (a)) are respectively non-additive synthesized by the "radar video synthesizing means (20)". Then, the radar video (31) (FIG. 10 (d)) is reproduced and output to the outside as an analog signal via the D / A conversion means.

Next, embodiments of the present invention will be described in detail with reference to the drawings. Referring to FIG. 1, an embodiment of the present invention has a configuration shown in FIG. It is divided into a video transmitting side and a video receiving side, and a transmitting side and a receiving side are connected by a digital line. First, the configuration of the transmitting side will be described.

The transmitting side converts an analog signal radar video output from the radar system into a digital signal, an A / D conversion circuit, integrates the digital signal radar video every several scans, and averages the data for one scan. Scan integrator 1 that generates an encoded video, detects and extracts only clutter data from the video, and performs a difference between the radar video output from the A / D conversion circuit and the clutter data output from the scan integrator 1. A "video difference circuit 2" for generating and outputting a video signal of only an aircraft and a noise signal, and separating the aircraft signal (referred to as a target signal) and a noise signal from a difference video including the aircraft and the noise signal by a threshold level, A "target / noise separation circuit 3" to be output, a separated target signal, The target data is generated and output for each aircraft by adding the amplitude bits of the target signal for four clocks to the distance information obtained by sampling the distance from the loader reference distance (0NM point) with the range clock. A generating circuit 4, a noise data range bin thinning circuit 5 for thinning out the separated noise signal in a range bin to compress the amount of data and outputting the thinned data, and a high order bit of the noise data being uniformly deleted to lower order. A "noise data high-order bit thinning circuit 6" that outputs only the bits; a "noise data generation circuit 7" that generates and outputs noise data by summarizing in sweep units and adding azimuth information; The range bin is thinned out for the clutter signal in the same way as the noise signal, A clutter data range bin thinning circuit 8 for outputting a clutter signal obtained by compressing a clutter signal, dividing the clutter signal into sectors on one display screen at equal angular intervals, and having a storage area having the same number of sectors as one scan A "clutter data sector dividing circuit 9" for storing, a "clutter data generating circuit 10" for generating and outputting clutter data by adding azimuth information to a clutter signal in sweep units output from the clutter data sector dividing circuit 9, A "video multiplexing circuit 11" that multiplexes target data, noise data, and clutter data in sweep units of the same direction, generates radar video data, and outputs the data to a digital line.

The receiving side separates the target data, the noise data and the clutter data from the multiplexed radar video data, and outputs the separated data.
2), a "target data buffer memory 13" for temporarily buffering the target data, and deciphering / separating distance information and amplitude information from the target data, grouping target data in the same direction in sweep units, and arranging them based on the distance information. A "target data reproducing circuit 14" for generating and outputting a target signal, a "noise data buffer memory 15" for temporarily buffering noise data, and interpolating the noise data that has been thinned out in the range bin, thereby reducing the data amount on the transmission side. A "noise data range bin reproducing circuit 16" to make the same number as the above, and a higher-order bit indicating "0" is uniformly added to the noise signal in which the range bin data has been corrected, and the same amplitude bit as the output of the A / D conversion circuit on the transmission side. The "noise data high-order bit reproduction circuit 17" for reproducing data into a number of sectors and one sector A clutter data sector combining memory 18 that decodes the sector number of clutter data transmitted by several sectors every time and stores the clutter data in a memory area having the same number as the sector number, and a range bin for clutter data. "Clutter data range bin reproducing circuit 1"
9 ", the target data from the target signal reproducing circuit 14, the noise data from the noise data upper bit reproducing circuit 17, and the clutter data range bin reproducing circuit 19
And a "radar video synthesizing circuit 20" for reading out each data in the same direction of the clutter data from the sweep unit in a sweep unit, synthesizing the data by a non-additive mixing method, and generating and outputting a radar video in a sweep unit. The analog signal is reproduced by the / A circuit and output to the outside.

The operation of FIG. 11 will be described with reference to FIGS. Signal waveforms used in the description are expressed in an analog (conceptual) manner. First, because the radar video of the analog signal is output from the radar system,
The signal is converted into a digital signal by an A / D conversion circuit. The sampling clock and the number of amplitude bits at this time are in accordance with the required quality of the remote place.

This digital signal is input to the "scan integration circuit 1" and the "video difference circuit 2". The “scan integrator 1” inputs and stores a radar video in sweep units at the timing of a radar trigger. The azimuth signal is used to integrate several sweeps of the same azimuth sweep signal to generate an averaged video for one scan.

FIG. 2 shows a case of two-scan integration as an example. Add the signal diagrams of sweep units in the same direction read in accordance with the radar trigger-2 (a) and (b),
The signal shown in FIG. 2C is generated. Next, averaging (in this case, dividing by 2) is performed to generate an averaged video shown in FIG.

A threshold level is set for this averaged video, and only the clutter signal is detected, extracted and output. This clutter signal 21 is shown in FIG. The "video difference circuit 2" captures a video signal in sweep units using a radar trigger. It is shown in FIG. The above-mentioned clutter signal 21 (FIG. 3 (b)) is subtracted from the video signal, and a difference signal 22 (FIG. 3 (c)) consisting only of the target and noise is output.

The difference signal 22 is converted into a target signal 23 and a noise signal 2 by a shresh hold level (FIG. 3D) in a "target / noise separation circuit 3".
4 and output. Separated target signal 23
Is shown in FIG. 3 (e), and the noise signal 24 is shown in FIG.
Show.

The target signal 23 (FIG. 4 (a)) is
The target generation circuit 4 calculates the distance from the reference distance of the radar (the radar position is set to 0 NM) using a clock having the distance resolution required for the used system (the same as the sampling clock of the A / D conversion circuit). And generate distance information. The noise signal 24 that generates target data for each target signal by adding distance information to the target amplitude data and outputs the noise signal is extracted at regular intervals by the “noise data range bin thinning circuit 5”. Reduce the amount of signal data. This operation is performed in sweep units.

FIG. 5 shows the operation. This noise signal 2
6. The "noise data upper bit thinning circuit 6" deletes the upper bits and outputs only the lower bits. The "noise data generation circuit 7" generates noise data by adding azimuth information to the noise signal of only the lower bits and outputs the noise data.

The data amount of the clutter signal 21 is reduced by the "clutter data range bin thinning circuit 8" in the same manner as the above-described noise signal range bin thinning operation. Figure-
5 shows the effect. As shown in FIG. 6, the clutter signals obtained by thinning out the range bins are divided into sectors on one display screen at equal angular intervals, and the clutter signals in the azimuth corresponding to the sector number are sequentially stored in the memory.

This memory has a capacity to hold one display screen, and the storage area is the same as the number of sector divisions. This operation is performed by the "clutter sector dividing circuit 9". As for the output of the clutter signal, the clutter signal of only several sectors is output for each scan by the azimuth reference signal output from the radar system. Figure 7 shows the output concept.

The "clutter data generation circuit 10" generates and outputs clutter data with azimuth information added. These target data, noise data, and clutter data are stored in a sweep unit in the same azimuth as “video multiplexing circuit 1.
The data is output from each data generating circuit in response to a read signal from "1", multiplexed, and output to a digital line.

On the receiving side, the received multiplexed signal is separated into target data, noise data and clutter data by the "video separation circuit 12", and is output. The “target data buffer memory 13” has an operation of temporarily storing the target data. The "target signal reproducing circuit 14" decodes the azimuth information from the target data output from the buffer memory, and generates a target signal by a clock having the same frequency as that of the transmission side as shown in FIG. -4 (e) to reproduce and output a target data signal in sweep units. (Figure-10
(C)) The noise data is temporarily buffered in the “noise data buffer memory 15”, and then the “noise data range bin reproducing circuit 16” converts the noise data of FIG. 5 (c) to that of FIG. 5 (d). The range bin data interpolation shown is performed, and the data amount before thinning out on the transmission side is reproduced.

Next, "Noise data upper bit reproduction circuit 1"
7 ", the upper bit of the bit indicating" 0 "is uniformly added to the noise data of only the lower bit, and the A /
It reproduces and outputs the same bit number as the amplitude bit number of the D conversion circuit. The signal is reproduced as a signal shown in FIG.
The clutter data is stored in the same sector as the azimuth information in the "clutter data sector combining memory 18". This memory holds clutter data for one display screen.

The clutter data stored and output in the memory is interpolated by the "clutter data range bin reproducing circuit 17" into the clutter signal data as shown in the conceptual diagram of FIG. Reproduce the same amount as the sender. "Radar video synthesis circuit 20"
Reads the target signal 27, the noise signal 29, and the clutter signal 30 in the same direction in sweep units (read signal 32), and reproduces the radar video signal shown in FIG.

Finally, the analog signal is reproduced by the D / A conversion circuit and output to the outside. Hereinafter, an example in which the present invention is applied to a specific radar system will be described. In the case of an air route monitoring radar system, the radar system is
Located at the summit, the control center is located in the city. Therefore, a digital line such as a dedicated line is required to supply radar video to a control station.

In the case of the conventional method, about 5 Mbps
The need to use a digital line is described in the prior art. For airline surveillance radar systems,
Distance resolution is about 1/8 NM (equivalent to 1.5 μs) Since the display system of the control station has 16 gradations, the video amplitude bit is 4 bits and the radar trigger is about 300 pp.
s, the azimuth is one rotation of the antenna, that is,
A signal which is represented by six pulses and is called an azimuth signal (ACP), which is output by one pulse when the antenna faces magnetic north, is called an azimuth reference signal (ARP).

The rotation speed of the antenna is about 10 seconds. The radar coverage is 200 NM. An example in which the present invention is actually applied will be described with an example of the above system specifications. FIG. 11 is applied to the configuration of the embodiment. For this reason, 3-7 [1] is applied to the configuration.

The transmitting device includes “scan integrating circuit 1”,
“Video difference circuit 2”, “target / noise separation circuit 3”, “target data generation circuit 4”, “noise data range bin thinning circuit 5”, “noise data upper bit thinning circuit 6”, “noise data generation circuit 7” "Clutter data range bin thinning circuit 8", "clutter data sector dividing circuit 9", "clutter data generation circuit 1"
0 "and" video multiplexing circuit 11 ".

The receiving device includes a “video separation circuit 12”,
“Target buffer memory 13”, “target reproduction circuit 14”, “noise data buffer memory 15”,
It comprises a "noise data range bin reproducing circuit 16", a "noise data upper bit reproducing circuit 17", a "clutter data sector synthesizing memory 18", a "clutter data range bin reproducing circuit 19", and a "radar video synthesizing circuit 20".

Incidentally, various external signals in this embodiment are as follows. Clock: 1.5 μs (1/8 NM system resolution) Radar trigger: 3.3 ms cycle (300 pps) Azimuth reference signal: 1 pulse / 10 sec (ARP) Azimuth signal: 4096/10 sec (ACP) Output from radar system An analog signal radar video has a maximum level of about 2 V and has information corresponding to 200 NM in synchronization with the radar trigger.

The data is digitized by the A / D conversion circuit, and the sampling clock is generated in 4 bits in 1.5 μs. The digitized radar video is input to the “scan integration circuit 1” and the “video difference circuit 2”.
The “scan integration circuit 1” captures a digital video signal in sweep units in synchronization with a radar trigger of about 3.3 ms.

At this time, the number of pulses of the azimuth signal supplied from the radar system is counted at the same time, and the azimuth of the sweep signal is recognized. In "scan integration circuit 1",
It has memory areas from No. 0000 to No. 4096,
The video is stored in the same memory area as the azimuth information of the sweep signal of the first scan (FIG. 2A) by the azimuth signal of 4096 pulses.

The number 0000 in the memory area indicates magnetic north.
When all the first scans have been stored and the sweep signal of the second scan (FIG. 2B) is input, the stored sweep signal of the same direction (FIG. 2A) is added to the stored sweep signal. Averaging the added signal (FIG. 2 (c)) (FIG. 2 (d))
And rewrite.

After the averaging process, only the clutter is extracted and separated from the signal according to the threshold level. The clutter signal is output in the same state in each scan, but the aircraft and noise have no correlation in each scan, and when the scan signals are added, the number of scans does not stack. The clutter signal, due to its scan-to-scan correlation properties,
When the cumulative addition is performed, a large amplitude difference appears. The conceptual diagram is shown in FIG.

The aircraft / noise has no correlation between scans when compared at the same location (here, distance). Figure-
2 (a) and FIG. 2 (b) are sum signals. FIG. 2 (c) shows a specific example. In this state, the signal is averaged (division is performed by the number of added scans, and in the example of FIG. 2, the signal is divided by 2 for 2-scan addition).
As shown in (c), only the clutter maintains the state of the signal before integration, and the amplitude of aircraft and noise is reduced by the division.

As a result, by setting the threshold, only the clutter signal can be easily extracted. Figure-
2 (f). In the “video difference circuit 2”, the video signal (FIG. 3) is synchronized with the radar trigger in sweep units.
(A)), and the difference from the clutter signal 21 (FIG. 3 (b)) output from the video integration circuit 2 is calculated.

Based on this difference, a difference signal 2 consisting of only the noise signal and the aircraft (target) from which the clutter signal has been removed
2 (FIG. 3C) is output. In the “target / noise separation circuit 3”, the differential signal diagram-3 (c)
Set a threshold level of 0.5V. Since the noise signal is set to less than 0.5 V (usually 0.3 V) and output from the radar system, the target signal 2 is obtained from the threshold level diagram-3 (d).
3 (FIG. 3 (e)) and the noise signal 24 (FIG. 3 (f))
Is separated into

The target signal 24 has a resolution of 1/8 NM in the "target data generation circuit 4".
With a clock of 5 μs, the distance from 0 NM is calculated.
As a result, the azimuth information is represented by about 16 bits. Since the spread of the 4-bit amplitude of the target signal in the distance direction (pulse width of the target signal) is equal to or twice the width of a 3 μs transmission pulse, when A / D conversion is performed in 1.5 μs, This corresponds to at most four clocks.

Therefore, one aircraft on the sweep has four 4-bit amplitude data. As a result, the data of the aircraft becomes 32 bits by 16 bits + 4 bits × 4 pieces of distance information. The “target generation circuit 4” performs processing in units of sweeps, but generates and outputs 32-bit target data per target.

The noise signal 24 is first converted to a 4-bit signal of 1.5 μs by the “noise data range bin thinning circuit 5”.
(1/8 NM)
In the M range, the noise data is 200 NM ÷ 1/8
The NM has generated 1600 range bin data. Therefore, noise data per sweep is 1600 range bins × 4 bits.

Since the noise has a distance resolution similar to that of an aircraft, the range bin thinning is set to 2, and every other noise data is extracted from 1600 noise data from 0 NM to 200 NM. This is 3.0 μs (1
/ 4 NM) is equivalent to the case of A / D conversion. As a result, the 4-bit noise data output from the “noise data range bin thinning circuit 5” is 800 bits.
Reduced to pieces. Here, the data compression ratio becomes 1/2.

Next, the "noise data high-order bit thinning circuit 6" uniformly deletes the high-order 2 bits of the 4-bit noise data. Since A / D conversion is performed on 2V with 4 bits, noise data of less than 0.5V changes only lower 2 bits. The upper 2 bits are always 0. By this processing, the “noise data upper bit thinning circuit 6”
All the zero noise data are output in 2 bits.

The noise data is added with azimuth information by the "noise data generation circuit 7" and output. The clutter signal 21 compresses the data amount in the "clutter data range bin thinning circuit 8" in the same manner as the noise signal, but the clutter of the clutter data range bin 8 has a larger spread in the distance direction than the noise. Is possible.

With respect to 1600 4-bit data, every fourth data is extracted to obtain 400 4-bit data. 1
This is equivalent to the case where A / D conversion is performed at a resolution of / 2 NM.
The clutter data is recognized by the clutter data sector dividing circuit 9 based on the direction signal based on the direction signal, and stored in the memory area of the same sector in sweep units.

In this case, the memory is set to 4096 sectors and stored in the memory sector recognized by the ACP direction signal counter of 4096 pulses. The output timing is based on ARP, and is set to 2 during one scan (10 seconds).
The clutter data of 56 sectors is extracted and output. Figure 7 shows the output concept. As a result, it takes 16 scans to finish outputting all 4096 sectors.

The "clutter data generation circuit 10" adds azimuth information to each clutter signal and outputs the same as the noise data. The "video multiplexing circuit 11" extracts target data, noise data, and clutter data in the same direction on a sweep basis, multiplexes the data, and outputs the multiplexed data to a digital line. Figure 8 shows the transmission concept.

On the receiving side, the "video separation circuit 12" separates the data into target data, noise data and clutter data and outputs the data. The target data is temporarily buffered in the “target buffer memory 13”,
The "target signal reproducing circuit 14" decodes the distance information and the amplitude bit in 32-bit units, and reproduces the target signal in sweep units according to FIG. 4D according to the distance information. The signal is output as shown in FIG.

After the noise data is temporarily buffered in the "noise data buffer memory 15", the 800 range bins are doubled by the "noise data range bin reproducing circuit 16" and reproduced to 1600. FIG. 5 shows the operation. As a result, the same number of range bin data as the output is reproduced by the pre-stage A / D conversion circuit on the transmission side. The "noise data high-order bit reproducing circuit 17" uniformly adds the high-order 2 bits indicating 0 to the 2-bit noise data and reproduces the 4-bit data.

As a result, the noise data is reproduced as 1600 4-bit data. The clutter data is stored in a memory area having the same number as the direction information of the clutter data in the “clutter data sector combining memory 18”.
Store clutter data. This memory is divided into 4096 sector areas like the transmitting side.

[Grand Clutter Range Bin Reproduction Circuit 1]
In "9", the data amount is reproduced by the same operation as the noise data. However, in the case of clutter data, each range bin data is multiplied by 4 to reproduce 1600 4-bit clutter data. The "radar video synthesizing circuit 20" reads out target data, noise data and clutter data of the same azimuth in a sweep unit with a readout signal 32 output by a radar trigger and an azimuth signal, and performs non-additive synthesis. Thus, the radar video shown in FIG. 10D is reproduced.

In the non-additive mixing, the maximum value is extracted from the three types of data for each distance unit (every 1/8 NM) and is used as video information at that distance. As a result, FIG.
The signal of (d) is obtained. Finally, the digital signal is reproduced and output by the D / A conversion circuit.

[0085]

[Other Embodiments] In FIG. 11, by supplying only a target signal to a system for performing tracking processing based on target detection data on the control station side, the present invention can be applied to systems other than display devices. At present, the radar system requires a target detection device as a configuration, but since the present invention also has such a function, a function of separately outputting only an aircraft (target detection) signal can be easily realized. Can supply to system.

If the type of radar video to be transmitted is not one type, the configuration shown in FIG. 11 can be realized only by configuring the number of video to be transmitted, and a signal to be transmitted to a remote place can be arbitrarily set. . Although the basic concept of the present invention is to transmit all the information included in the radar video to a remote place, the present invention can transmit only the clutter and covers the so-called MTI processing function. It can also be applied to countermeasures to eliminate MTI disappearance by backing up the signal processing of the existing radar system or applying the capability interpolation.

[0087]

The effect of the present invention is that the transmission capacity is compressed without deteriorating the quality of the radar video (the resolution of the aircraft). This is because the present invention separates the target signal, the noise signal, and the clutter signal from each other, and performs data compression processing only on the noise signal and the clutter signal.

The conventional digital transmission capacity of radar video was 4.8 Mbps. The reason is that the transmission capacity in the present invention is obtained by the following calculation. However, the numerical values are an example as described above. Transmission capacity of target signal + transmission capacity of noise signal + transmission capacity of clutter signal Transmission capacity of target signal Data amount of one target on one sweep: 32 bits When one target is spread in the azimuth direction (hit number is considered) Data amount: 32 bits × 30 hits = 960 bits Total target data amount in one display screen: 960 bits × 400 units = 384000 bits Since real-time transmission in 10 seconds is necessary, target transmission capacity: 384000 bitsｂ10 s =
38.4 kbps Transmission capacity of noise signal Noise data amount for one sweep: 800 data × 2 bits = 1600 bits Noise data amount in one display screen: 1600 bits × 3
000 sweep = 4800000 bits To transmit in 10 seconds, noise transmission capacity: 4800000 bits @ 10s
= 480 kbps Clutter signal transmission capacity Clutter data amount for one sweep: 400 pieces × 4 bits = 1600 bits Transmission capacity to be transmitted in 10 seconds: 1600 bits × 25
6 sweep ÷ 10 s = 41 kbps From the above, the transmission capacity in the present invention is 38.4 kbps + 480 kbps + 41 kbps = 5
59.4 kbps For the transmission capacity of 4.8 Mbps in the conventional method, about 1 /
9 capacity.

As for noise, since the distance resolution can be further reduced, the compression ratio may be further increased. As a result, the line maintenance cost can be reduced by 1/9 or more. As described above, according to the radar video transmission device of the present invention, the noise signal is thinned out from the noise data once sampled by the A / D converter (this is the same process as reducing the resolution of the sampling clock).
In addition, the data amount of the noise signal is reduced from the upper bit of the amplitude bit of the A / D conversion by the low amplitude (since noise has a property that the higher bit is always fixed to 0). Since the reduction of the data amount and the movement by the thinning-out processing are much slower than that of the aircraft (the ground clutter has a moving amount of 0, but indicates that the weather clutter moves slowly), the signal update time (1 It is possible to realize a low transmission capacity by delaying the display screen update time (indicating the update time of the display screen) in accordance with the movement amount, and reducing the data transmission capacity by reducing the ratio of the clutter signal in the transmission data. It has various excellent effects.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of an embodiment of a radar video transmission device, a digital transmission device, and a reception device according to the present invention.

FIG. 2 is a conceptual diagram of scan integration and clutter separation.

FIG. 3 is a conceptual diagram of target / noise separation.

FIG. 4 is a conceptual diagram of target data generation and target signal reproduction.

FIG. 5 is a conceptual diagram of range bin thinning / range bin reproduction.

FIG. 6 is a conceptual diagram of clutter data sector division.

FIG. 7 is a conceptual diagram of clutter data transmission timing.

FIG. 8 is a conceptual diagram of video multiplex transmission.

FIG. 9 is a conceptual diagram of clutter data sector composition.

FIG. 10 is a conceptual diagram of radar video synthesis.

FIG. 11 is a configuration example of an embodiment of the present invention.

FIG. 12 is an explanatory diagram of a radar video.

[Explanation of symbols]

1 scan integration means (circuit), 2 video difference means (circuit), 3 target / noise separation means (circuit) 4 target data generation means (circuit), 5 noise data range bin thinning means (circuit) 6 noise data upper bit thinning means (Circuit), 7 Noise data generating means (Circuit) 8 Clutter data range bin thinning means (Circuit), 9 Clutter data sector dividing means (Circuit) 10 Clutter data generating means (Circuit), 11 Video multiplexing means (Circuit) 12 Video Separation means (circuit), 13 target data buffer memory 14 target signal reproduction means (circuit), 15 noise data buffer memory, 16 noise data range bin reproduction means (circuit), 17 noise data upper bit reproduction means (circuit), 18 clutter data Sector synthesis memory 19 clutter data range bin reproducing means (circuit) 20 radar video synthesizing means, 21 clutter signal, 22 difference signal, 23 target signal, 24 noise signal, 25 target data, 26 noise data, 27 target signal, 28 noise data, 29 noise signal , 30 Clutter signal

Claims (4)

[Claims] In a digital transmission apparatus of a low transmission capacity of radar video, a transmitting side is provided with a scan integrator for extracting only a clutter signal from the radar video, and an aircraft signal obtained by subtracting a clutter signal portion from the radar video. Differential means for generating a signal consisting of only noise and noise signals, target / noise separating means for separating an aircraft signal and a noise signal from the differential signal, and generating direction data and amplitude information from the separated target signal to generate target data Target data generating means, noise data range bin thinning means for thinning out range bin data from the separated noise signal to reduce the number of data, and noise data high-order bits for removing high-order bits of the noise signal and outputting only low-order bits Decimation means and noise data output Noise data generating means for generating noise data by adding information; clutter data range bin thinning means for reducing the number of clutter signal data from the clutter signal by the same operation as the range bin thinning of the noise signal described above; Clutter data sector dividing means for storing one scan and dividing and outputting the data for one scan; clutter data generating means for generating and outputting clutter data by adding azimuth information to a clutter signal; Video multiplexing means for multiplexing and transmitting noise data and clutter data for each signal in the same direction, video separating means for separating the receiving side into target data, noise data and clutter data from the received data, and target data Target buffer to temporarily buffer A target buffer memory, a target signal reproducing means for decoding distance information and amplitude information from target data and reproducing a target signal, a noise data buffer memory for temporarily buffering noise data, and interpolating a range bin to the noise data; Noise data range bin reproducing means for returning the number of range bins before thinning, noise data range bin reproducing means for uniformly adding upper bits and returning the number of amplitude bits to the state of A / D conversion, and clutter data divided and transmitted. Clutter data sector synthesis memory for sequentially storing according to the azimuth information, clutter data range bin reproducing means for interpolating the reduced range bins and returning to the number of range bins before thinning, reproduced target signal, noise signal and clutter signal in sweep units Is added to the original radar video. A radar video transmission apparatus comprising: a radar video synthesizing unit that reproduces and outputs a video signal. 2. The apparatus further comprises a D / A conversion means, wherein an output of the radar video synthesizing means can be input to the D / A conversion means and output to the outside as an analog signal. The radar video transmission device according to claim 1. 3. A low-capacity digital transmission apparatus for radar video, comprising: a scan integrator for extracting only a clutter signal from the radar video; Video / difference means for generating a signal of the target signal, target / noise separation means for separating an aircraft signal and a noise signal from the difference signal, and target data generation for extracting azimuth information and amplitude information from the separated target signal to generate target data Means, a noise data range bin thinning means for thinning out range bin data from the separated noise signal to reduce the number of data, and a noise data high bit thinning means for removing upper bits of the noise signal and outputting only lower bits. Add azimuth information to the above output noise data Noise data generating means for generating noise data; clutter data range bin thinning means for reducing the number of clutter signal data from the clutter signal by the same operation as the above-described range bin thinning of the noise signal; Clutter data sector dividing means for dividing and storing the data for one scan, clutter data generating means for generating and outputting clutter data by adding azimuth information to the clutter signal, the target data, noise data and Video multiplexing means for multiplexing clutter data for each signal in the same direction and transmitting the multiplexed data, and a radar video digital transmission device. 4. A digital receiver having a low transmission capacity for radar video, comprising: video separating means for separating received data into target data, noise data and clutter data; and a target data buffer for temporarily buffering the target data. Memory, target signal reproducing means for decoding the distance information and amplitude information from the target data and reproducing the target signal, noise data buffer memory for temporarily buffering the noise data, and interpolating and thinning out the range bin to the noise data Noise data range bin reproducing means for returning the number of range bins to the previous number; noise data range bin reproducing means for uniformly adding upper bits and returning the number of amplitude bits to the state of A / D conversion; Clutter that sequentially stores according to the azimuth information Clutter data range bin reproducing means that interpolates the reduced range bins and returns the number of range bins before thinning, and non-additional synthesis of the reproduced sweep target signal, noise signal, and clutter signal to produce the original radar video And a radar video synthesizing means for reproducing and outputting the digital video signal.