CN108226874B

CN108226874B - Secondary radar digital video display method

Info

Publication number: CN108226874B
Application number: CN201711474166.7A
Authority: CN
Inventors: 张虹
Original assignee: Nanjing Enruite Industrial Co Ltd
Current assignee: Nanjing Enruite Industrial Co Ltd
Priority date: 2017-12-29
Filing date: 2017-12-29
Publication date: 2021-09-10
Anticipated expiration: 2037-12-29
Also published as: CN108226874A

Abstract

The invention discloses a secondary radar digital video display method, after decoding and obtaining the symbol and confidence information of the response, the distance, direction, symbol and confidence of the response are written into a double-port RAM in sequence, the double-port RAM is shared by signal processing and data processing and is divided into 2 areas with equal size; the signal processing generates an interrupt at the beginning of each inquiry period, after the data processing responds to the interrupt, the response signal obtained in the last inquiry period is read from 1 area of the dual-port RAM, and simultaneously, the currently generated response signal is written into the other 1 area of the dual-port RAM by the signal processing in real time, namely, 2 areas of the dual-port RAM are ensured to be in a read-out state and a write-in state respectively. After data processing is carried out to obtain response signals, the response signals are reordered according to the sequence that the direction is from small to large and the distance of the same direction is from near to far and then written into a digital video display list; and periodically sent to the display terminal.

Description

Secondary radar digital video display method

Technical Field

The invention relates to a secondary radar digital video display method, belongs to a secondary radar target display technology, and is suitable for displaying monopulse secondary radar target response information and non-monopulse secondary radar target response information.

Background

The secondary radar is an important component of an air traffic control system, is an important information source of the air traffic control system, is suitable for airport and air route monitoring, and can provide distance, direction, air pressure height, identification codes and other special marks (such as emergency, communication fault, hijacked and the like) of an aircraft with an onboard transponder in a power coverage range.

According to the working principle of the secondary radar, the monitoring function of the secondary radar on the target can be realized only by the cooperation of the airborne transponder and the secondary radar. The secondary radar sends out an inquiry to an airborne transponder in a power coverage range through a wave beam continuously rotating by 360 degrees, and the airborne transponder makes different responses according to different inquiry modes after receiving an inquiry signal of the secondary radar. The secondary radar obtains the position, air pressure height, identification code, special mark code and other information of the airborne transponder through the identification and decoding of the response pulse string, thereby realizing the monitoring of the cooperative target. Usually, on a radar target display terminal, the relevant information of the target is displayed by using a point track or a flight track, and a point track or flight track signal is sent to a control center at the back end for airport monitoring or route control.

Every time the secondary radar receives 1 response, the secondary radar corresponds to 1 response pulse train arranged according to a certain rule, and the response pulse structure is shown in fig. 5. The response pulse is displayed on a display according to the distance and the direction to obtain an original video called a secondary radar. To simplify the display of the reply signal, the pulse train corresponding to 1 reply can also be represented by one pulse, and the reply signal thus displayed is called digital video. According to the difference of the rotation speed of the secondary radar antenna, usually, a wave beam sweeps a target to obtain 8-15 times of response, corresponding original video signals are 8-15 pulse trains, digital video signals are 8-15 pulses, and 1 point of a track or flight path signal is shown in the graph 1. The target information of the digital video display is more original and detailed than the point track and the flight track, but is simpler than the original video. An example of a display of raw video, digital video, point/track that produces 11 responses as the beam sweeps across an object is shown in figure 2. The generation of the digital video relates to each part of a signal receiving path of an antenna, a feeder line, a receiver, signal processing, data processing, display control and the like of the secondary radar, and the digital video not only can enable target information to be displayed more finely, but also has very important functions on judging the state of the secondary radar equipment and positioning faults.

According to different methods for testing the azimuth, the secondary radar is divided into a monopulse working system and a non-monopulse working system, the non-monopulse working system is a traditional azimuth measurement method, the working principle is shown in figure 3, and the azimuth of the target relative to the radar can be obtained by adding the beam pointing azimuth in the beam entering process and the beam pointing azimuth in the beam exiting process and dividing the sum by 2. The non-monopulse system secondary radar is gradually eliminated due to poor angle measurement precision. The single-pulse secondary radar adopts two receiving channels of sigma and delta to realize a single-pulse angle measurement technology, the working principle is shown in fig. 4, the sum-difference ratio (sigma/delta) of a certain target sigma and delta received signal amplitude is obtained through calculation, and a corresponding azimuth correction value can be obtained according to the corresponding relation between the sum-difference ratio and the azimuth offset. In order to distinguish the target on the left or right of the beam direction, a single-pulse system introduces a phase concept, the target falls on the left of an azimuth axis, the phases of sigma and delta receiving signals are opposite, a sum-difference ratio value takes a negative value, and a corresponding azimuth correction value is a negative angle; when the target falls on the right side of the azimuth axis or is very close to the azimuth axis, the target cannot be distinguished to be on the left side or the right side of the azimuth axis, the sum-difference ratio at the moment is defined as low confidence and is also represented by 1 bit.

The primary video of the secondary radar is displayed by a special display device, the method is that after the secondary radar recognizes the response pulse, the direction, the distance zero point and the response pulse string are sent to a special video display, the video display determines the relative position of the response pulse on a screen according to the direction, the distance and the distance zero point, and the display is updated in real time according to the input pulse signal. The secondary radar original video has large information quantity and high updating speed, and a video display and a display card driving circuit are specially equipped for displaying the original video signal in real time.

Along with the development of electronic technology and the improvement of integration level, the processing capacity and the operation speed of a computer are also improved, so that a video display unit and a maintenance display terminal of a secondary radar are combined into a whole, the original video display of a secondary radar response signal is simplified into digital video display, multiple functions of simultaneously finishing radar working mode control, parameter setting, state monitoring, fault alarming, real-time display of digital video, trace and track of a response target on one computer are realized, peripheral equipment of the secondary radar is simplified, and the operability and the maintainability of the radar are improved.

Disclosure of Invention

The invention provides a novel secondary radar digital video display method, which is suitable for displaying the digital video of a monopulse secondary radar and a non-monopulse secondary radar.

In order to solve the problems, the invention adopts the following technical scheme: a secondary radar digital video display method is characterized in that after response pulse extraction is completed in signal processing, frame identification is carried out on pulse signals, only a pulse string comprising F1 and F2 frames is confirmed as a response, and the response is represented by 1 pulse; f1 is the 1 st pulse in the pulse train, F2 is the last 1 pulse in the pulse train;

after the symbol and confidence information of the response are obtained by decoding, sequentially writing the distance, the direction, the symbol and the confidence of the response into a double-port RAM, wherein the double-port RAM is shared by signal processing and data processing and is divided into 2 regions with the same size; the signal processing generates an interrupt at the beginning of each inquiry period, after the data processing responds to the interrupt, the response signal obtained in the last inquiry period is read from 1 area of the dual-port RAM, and simultaneously, the currently generated response signal is written into the other 1 area of the dual-port RAM by the signal processing in real time, namely, 2 areas of the dual-port RAM are ensured to be in a read-out state and a write-in state respectively. After data processing is carried out to obtain response signals, the response signals are reordered according to the sequence that the direction is from small to large and the distance of the same direction is from near to far and then written into a digital video display list; and periodically sent to the display terminal.

The display terminal is a maintenance display terminal, and the maintenance display terminal draws a response existence pulse according to the distance, the direction, the symbol and the confidence coefficient of the response signal on a display interface according to a preset color and displays a digital video of the secondary radar.

Compared with the closest prior art, the invention has the following beneficial effects: by adopting digital video display, firstly, frame filtering is carried out on the response signals, and only complete responses including F1 and F2 frame pulses are displayed, so that incomplete responses generated by multipath and interference are filtered; secondly, the symbol and confidence information are added in the digital video, and the positions of the targets in the antenna beams are reflected by different colors, so that the accurate judgment on the quality, continuity and direction change trend of the response signals is facilitated, the real-time monitoring on the working states of a plurality of functional modules of the secondary radar is facilitated, and the normal monopulse characteristic of the receiver can be judged as long as the digital video response points are clearly divided into a left side and a right side according to the symbols, are symmetrically distributed and are not crossed and mixed; as long as the low-confidence response point only appears at the central position of the digital video, the amplitude-to-amplitude characteristics of sigma and delta of the receiver can be preliminarily judged to be normal; if the digital video has continuous point distribution and no leakage point in the middle, the signal-to-noise ratio of the response signal is high, and the receiver amplifying circuit works normally; if the points of the digital video are uniformly distributed, the rotation speed of the antenna is uniform, the azimuth signal is normal, and the like. The digital video not only reflects the original information, characteristics and quality of the target response signal, but also provides a real-time monitoring means for the states of the secondary radar antenna, the feeder line, the receiver and the whole receiving channel for signal processing, and provides great help for fault diagnosis of the secondary radar. The digital video increases the information content displayed by the response signal without adding special hardware equipment, and the information sharing area between signal processing and data processing is increased by modifying the interface and the program of the maintenance display terminal, so that the digital video can be displayed on the original maintenance display terminal.

Drawings

FIG. 1 is a block diagram of a secondary radar target signal flow.

Fig. 2 type of secondary radar response signal.

FIG. 3 is a schematic diagram of the principle of non-monopulse secondary radar azimuth measurement.

FIG. 4 is a schematic diagram of the principle of single-pulse secondary radar azimuth measurement.

Fig. 5 definition of secondary radar response pulses.

Detailed Description

The present invention is described in further detail below with reference to the attached drawings.

According to the working principle of the secondary radar, the secondary radar on the ground sends out an inquiry signal to the air, and a responder receiving the inquiry signal responds. The response signal is composed of a pulse train arranged according to a certain rule, the pulse train is composed of 15 pulse positions with the pulse width of 0.45 mu S, the leading edge delay of each pulse position of 1.45 mu S and the total occupation of 20.3 mu S, the pulse on the appointed pulse position represents that the code of the position is '1', and the non-pulse represents that the code of the position is '0'. The 1 st pulse of the 15 pulses is F1 and the last 1 pulse is F2, F1 and F2 are frame pulses, always "1", indicating the presence of a response, and the remaining 13 bits are response codes.

The secondary radar displays the relevant information of the target by using a point track or a flight track on a radar target display terminal, and the control center realizes airport monitoring or route control through the point track or the flight track information provided by the radar. In order to obtain target information more detailed than a point track or a flight track, the response pulse can be completely displayed on a screen according to the distance and the direction, and the original video display of the secondary radar is realized. The original video has a large amount of information and a high updating speed, and usually needs a special video display and a display card driving circuit to display. In order to simplify equipment and keep effective information display, 1 pulse string corresponding to 1 response is represented by 1 pulse, the specific method is that F1 and F1 frame identification is carried out on the response pulse, only the pulse string comprising F1 and F2 frames is confirmed to be a response, the symbol and confidence information of the confirmed response are further confirmed, and one response is displayed on a screen corresponding to one point according to the distance and the direction, namely digital video display of secondary radar. The target information displayed by the digital video is richer and more detailed than the point track and the flight track, and is relatively simplified than the original video, but the symbol and confidence information added compared with the original video plays an important role in real-time monitoring and fault positioning of the state of the secondary radar equipment, the hardware cost is not required to be increased, and the digital video display function can be realized by changing software and maintaining the display terminal.

The sum-difference ratio (sigma/delta) of the monopulse secondary radar response signals is distinguished by positive confidence, negative confidence and low confidence, and when the sum-difference ratio is displayed in a digital video mode, positive confidence, negative confidence and low confidence of the sum-difference ratio are represented by different colors, so that a target can be clearly distinguished to be positioned at the left side, the right side or the middle position of an antenna beam. For non-monopulse secondary radar, no delta receiving channel exists, the response signal has no positive and negative score, and no definition of low confidence is provided, and the digital video corresponding to each response is composed of points of one color. Therefore, the digital video is suitable for the response information display of monopulse and non-monopulse secondary radar, and a display example can be seen in fig. 2. Due to the fact that the dwell time of the target in the beam is limited and the position of the target is random, some targets in the digital video do not have low-confidence response points, and some targets have low-confidence response points, but only 1 response point can fall into the low-confidence region due to the fact that the low-confidence region is narrow. The example shown in fig. 2 has 11 responses, 5 responses to the left of the beam, 5 responses to the right of the beam, and the middle 1 response falling in the low confidence region. Since the secondary radar interrogation is an A, C pattern alternating, the encoding of the response bursts also alternates.

The invention provides a secondary radar digital video display method, which comprises the following steps: after the signal processing is finished and the response decoding is carried out to obtain the information of the response target, the distance (16bits), the direction (14bits), the symbol (1bit) and the confidence (1bit) of the response target are sequentially written into a double-port RAM, and the double-port RAM is shared by signal processing and data processing and is divided into 2 regions with equal size. The signal processing generates an interrupt at the beginning of each inquiry period, after the data processing responds to the interrupt, the response signal obtained in the last inquiry period is read from 1 area of the dual-port RAM, and simultaneously, the currently generated response signal is written into the other 1 area of the dual-port RAM by the signal processing in real time, namely, 2 areas of the dual-port RAM are ensured to be in a read-out state and a write-in state respectively. After data processing is carried out to obtain response signals, the response signals are reordered according to the sequence that the direction is from small to large and the distance of the same direction is from near to far, and then the response signals are written into a digital video display list.

The data processing and maintenance display terminal computer is connected through a local area network, when the digital video display is selected according to a control command on the display control interface, the data processing regularly sends a response signal in a digital video display list to the maintenance display terminal through the network, and the maintenance display terminal displays the response signal on a screen in a digital video mode according to the sequence of the azimuth and the distance; when the digital video display is not selected, the data processing and maintenance display terminal does not need to transmit the response signal, and only transmits the point signal, the track signal and the equipment state signal. Because the information content of the response signal is large, the data updating is fast, when the secondary radar equipment works normally and does not pay attention to the equipment state (such as unattended operation and night), the digital video can be selected not to be displayed, and the processing load of the equipment is reduced. When the state of the equipment is concerned, particularly when the equipment has faults, the digital video can be selectively displayed, the problem is found or the fault is positioned by observing the digital video, for example, the digital video response points are divided into a left side and a right side according to clear symbols, are symmetrically distributed and are not crossed and mixed, the monopulse characteristic of the receiver can be judged to be normal, if the digital video response points are distributed continuously and have no leakage point in the middle, the signal-to-noise ratio of the response signal is high, and the amplification circuit of the receiver works normally; if the points of the digital video are uniformly distributed, the rotation speed of the antenna is uniform and the azimuth signal is normal; for example, the digital video is intermittent, which indicates that the amplitude of the reply signal is very weak, or the reply signal is interfered or shielded, resulting in incomplete signal reception, or the gain of the receiver amplifying circuit is too small, the bottom noise is too large, and so on.

And maintaining a target display interface of the display terminal, wherein usually only display options of point tracks and flight tracks are similar to target information options sent to a control center by a radar. The invention adds digital video display content, so digital video display options are correspondingly added on the target display interface, and related control programs are added to complete the functions of generating and sending control commands, connecting networks, sending and receiving data packets, displaying digital videos and the like.

After the function of displaying the digital video is selected by the maintenance display terminal, the relevant information of the response signal is obtained from data processing, the relevant information comprises the distance (16bits), the direction (14bits), the symbol (1bit) and the confidence coefficient (1bit), and the display control program draws a response point on the corresponding position of the target display interface according to the distance and the direction information; according to the sign and confidence information, the response points take different colors, the negative sign uses red to correspond to the left of the beam, the positive sign uses blue to correspond to the right of the beam, and the low confidence corresponds to green to correspond to the center or the vicinity of the beam. Since the position of each response signal in the beam is random, but the time interval is fixed, and the beam width is fixed, the number of times that the beam sweeps across the target to generate the response is basically fixed, the number of times that the beam falls on two sides of the azimuth axis of the beam is also basically half, and the response with low confidence coefficient is randomly generated, 1 response with low confidence coefficient in 1 group of responses is possible, and there is no response with low confidence coefficient (as shown in fig. 2, there is 1 response with low confidence coefficient).

The above description is only a preferred embodiment of the present invention, and is not limited to the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the scope of the claims of the present invention.

Claims

1. A secondary radar digital video display method is characterized in that: after the signal processing finishes the extraction of the response pulse, the frame identification is carried out on the pulse signal, only the pulse train comprising the frames F1 and F2 is confirmed as a response, and the response is represented by 1 pulse; f1 is the 1 st pulse in the pulse train, F2 is the last 1 pulse in the pulse train;

after the symbol and confidence information of the response are obtained by decoding, sequentially writing the distance, the direction, the symbol and the confidence of the response into a double-port RAM, wherein the double-port RAM is shared by signal processing and data processing and is divided into 2 regions with the same size; the signal processing generates an interrupt at the beginning of each inquiry period, after the data processing responds to the interrupt, the response signal obtained in the last inquiry period is read from 1 area of the dual-port RAM, and simultaneously, the currently generated response signal is written into the other 1 area of the dual-port RAM by the signal processing in real time, namely, 2 areas of the dual-port RAM are respectively in a read-out state and a write-in state; after data processing is carried out to obtain response signals, the response signals are reordered according to the sequence that the direction is from small to large and the distance of the same direction is from near to far and then written into a digital video display list; and periodically sending the data to a display terminal;