KR950003603B1 - Clutter attenuation control and takedown apparatus and method of pulse radar - Google Patents

Abstract

The apparatus includes; means for selecting ports corresponding to function controlling signals input; means for memorizing clutter algorithm with high speed and large capacity which stores algorithm; means for distributing data which inputs data from the clutter algorism memorizing means and the port selecting means; sensitivity time control(STC) means which removes the surface reflecting wave from the radar receiving signals input; fast time constant(FTC) means which removes weather reflecting waves; means which compensates the gains so much levels as the ones removed from the STC means and the FTC means; and means for generating synchronizing signals which extracts the synchronizing signals from the signals received in the radar and synchronizes the clutter algorism memorizing means.

Description

Clutter attenuation control and eliminator of pulse radar and method

1 is a block diagram showing the configuration of a general pulse radar,

2 is a detailed block diagram of the video signal processor of FIG.

3 is a block diagram of a conventional clutter adjuster and remover,

FIG. 4 is a detailed configuration diagram showing FIG. 3 in more detail.

5 is a block diagram of the clutter control and eliminator of the pulse radar of the present invention,

FIG. 6 is a detailed configuration diagram illustrating FIG. 5 in more detail.

7 shows land clutter when the sea condition is 5 (typhoon),

8 shows the sea level clutter when the sea condition is 1 (the calmest time),

9 shows a land clutter when the reflection of the earth's surface is maximum,

10 shows land clutter when the reflection of the ground surface is minimal,

FIG. 11 shows the rain clutter when the rainfall is maximum,

12 shows rain clutter when rainfall is minimal.

13A, 13B, and 13C show the case where the clutter is the minimum and the maximum when the seventh to the twelfth degrees are shown.

14A to 14E illustrate a method of implementing a clutter removal algorithm in a memory.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to video signal processing of a pulse radar, and more particularly, to a clutter control and canceller and a method for attenuating or effectively removing various clutter signal forces included in a video signal of a radar receiver. will be.

The radar is divided into pulse radar, CW (continuous wave) radar, frequency modulated radar, and phase modulated radar according to the application. Figure is like the first diagram. The pulse modulator 10 generates a repeated pulse train, and the transmitter 11 amplifies the signal with a high output according to a train of pulses signal and transmits the signal to the antenna 14. The duplexer 12 serves to separate transmission and reception so that one antenna 14 can be shared in transmission and reception. The antenna 14 emits pulses into space and receives echoes reflected from targets, ground surfaces, sea surfaces, rain, clouds, fog, and the like. The position coordinates of the antenna 14 are controlled by a position servo 22 connected between the mechanical device 13 driving the antenna 14 and the display and the controller 21 so that the azimuth angle on the display and the position of the antenna 14 are adjusted. Are motivated. The echo signal received by the antenna 14 is input to the low noise RF amplifier 15 via the duplexer 12. The low noise RF amplifier 15 amplifies the received signal while suppressing noise. The mixer 16 mixes the local oscillation signal from the local oscillator 17 and the received input RF signal to produce an intermediate frequency signal (hereinafter referred to as IF below intermediate frequency) of 30 MHz to 120 MHz. The intermediate frequency amplifier (IF AMP) is a matched filter that amplifies the signal-to-noise (S / N) ratio. Detector 19 produces a video signal at the received IF. At this time, the video signal includes a signal reflected on the target, noise and clutter. Clutter refers to echo signals reflected from the surface, sea surface, clouds, rain, and fog. The surface clutter reflected from the surface and the sea clutter reflected from the sea surface And weather clutter (called volume clutter) that is reflected from rain, clouds, and fog. Such clutter signals may be useful signals depending on radar purposes and uses, and may be regarded as unnecessary signal forces, but generally referred to as unnecessary signal forces. The video signal processor 20 removes unnecessary noise or clutter deemed unnecessary in relation to the radar operation purpose at the time and extracts and displays a pure target signal. The display and controller 21 show the target captured by the radar on the CRT and display various necessary states. There is also a clutter selector adjuster that allows the operator to manipulate the display.

2 is a video signal processor 20 which is further divided into a clutter remover 23 for removing clutter from a received echo and a video for extracting a target signal while reducing the extraction level for various noise signals below a predetermined level. Signal main processor 24 is shown. The pulse radar transmits a transmission pulse and receives the echo. The echo signal includes the target reflector reflected signal and the clutter reflected from the environmental factors such as the surface, sea surface, cloud, fog, and rain. It is necessary to remove the unnecessary clutter to accurately detect the problem. Clutter displayed on the CRT is an obstacle to distinguishing targets.

Conventionally, the method of performing the clutter removal function of the pulse radar is to remove the clutter using a simple analog standard model, or to calculate the clutter algorithm in the central processing unit as shown in US Pat. No. 4,837,579. There is a method of supplying every pulse repetition period (hereinafter referred to as PRT). That is, according to FIGS. 3 and 4, which are the method according to US Pat. No. 4,837.579, the clutter is calculated in consideration of a number of variables obtained from more than 40 rayta basic specifications and various statistics in the system processor 69. When the radar operator adjusts the adjuster in the control panel, the system processor 69 performs calculations to derive an appropriate algorithm in consideration of all the variables accordingly. The calculated final output goes to the address decoder and buffer 65 via the system bus 68. The address decoder and buffer 65 distributes the input to the STC 62 and the gain compensator 64 which remove surface clutter. The STC 62 temporarily stores the data provided by the system processor 69 in the memory 71 and latches the data according to the synchronization of the latch clock 63 to convert the D / A converter 73 into an analog signal to convert the video signal. Generate a mean signal to remove the surface and ground clutter. FTC (referred to as Fast Time Constant) is a kind of high-pass filter that removes the volume clutter reflected from the weather factor, and removes the clutter to a uniform level by the variable resistor. The gain compensator 64 temporarily stores the data provided by the system processor 69 in the memory 75 and then latches it in synchronization with the latch clock so that the analog signal is rolled on the D / A converter 77 by the STC 80 and the FTC. The level is compensated for as attenuated at 61. In this way, the conventional clutter remover performs only the Thresholder 70 function that executes the algorithm delivered by the system processor 69, and thus must supply data every PRT or only when the operator adjusts the data without supplying every PRT. Even if supplied, all algorithmic calculations were performed on the system processor.

The disadvantage of the conventional clutter remover is that the system processor performs the clutter processing algorithm and outputs the result, so that the performance of the entire system is degraded, and the processing speed is slow, so that it cannot be applied to a high resolution radar or color image radar. do. In addition, the main synchronization signal must be received from the outside, and in order to solve the problem by itself, additional circuits are added, and if the algorithm cannot be processed quickly, the S / N ratio is reduced and the capture performance is deteriorated.

Therefore, an object of the present invention is to store a pre-calculated algorithm in a high-capacity memory in order to remove or phase-attenuate clutter contained in the radar received signal, and to quickly output the result according to the controller's input, reliability The present invention provides a clutter control and eliminator for pulse radar capable of rapid and rapid processing.

Another object of the present invention is to provide a method for adjusting and removing clutter of a pulse radar.

In order to achieve the above object of the present invention, a clutter adjusting and eliminating device for a pulse radar is a port for selecting a corresponding port according to a function controller signal input from an adjuster in a video processor of a pulse radar comprising an antenna, a transceiver, and a display. Selection means; A high-speed large-capacity clutter algorithm memory means for storing an algorithm selected in advance according to the port selection means and outputting it on demand; Data distribution means for inputting data from the clutter algorithm memory and the port selection means and distributing the data to the means; STC means for removing ground and surface reflection waves from the radar received signal according to the value output from the clutter algorithm memory means; FTC means for removing the weather reflection wave in accordance with the signal from the data distribution means; Gain compensating means for compensating for the level removed from the STC and the FTC according to a signal input from the clutter algorithm memory via the data divider; And synchronizing means for extracting a synchronizing signal from the radar received signal and holding a frequency generator to synchronize the clutter algorithm memory means.

In addition, the clutch radar clutch adjustment and removal method for achieving the other object of the present invention is a clutter removal method of the pulse radar, the step of selecting a clutter removal algorithm corresponding to the sea and weather conditions observed by the operator ; Extracting a clutter removal algorithm corresponding to the operator's selection from among a plurality of clutter removal algorithms corresponding to the grades of sea and weather conditions calculated and stored in advance; And removing clutter included in the received radar signal according to the extracted clutter removal algorithm, thereby using a clutter removal algorithm that is pre-calculated according to the grade of sea and weather conditions. Characterized in that possible.

Next will be described in detail with reference to the accompanying drawings.

5 is a block diagram of the clutter control and eliminator of the present invention pulse radar. Video signals of marine navigation and coastal surveillance, marine control radar or aircraft detection, tracking radar, and meteorological radar or mapping radar video signals include ocean waves, rain, snow, clouds, Signals reflected from fog, ground conditions, etc. are included. These signals are necessary or unnecessary in relation to radar detection purposes. Unnecessary signals, like noise signals, act as a deterrent to detection and capture. The signal reflected from the sea surface is called sea clutter. The sea clutter depends on the height of the waves and is closely related to the wind speed. It is also related to the angle seen by the radar. Sea Clutter is a clutter strength σc, where the beam shape loss is Lp, the distance from the wave is varied according to R, antenna height h, wind speed, sea condition, wave length, etc. When the parameter γ, the beam angle θa, the grazing angle ø, and the wavelength C are obtained as follows.

Here, if the wave state is 5 (typhoon) and 1 (the calmest state), this equation is applied to calculate the C / N level of the radar with X Band (8GHz ~ 12GHz) frequency. It is distributed in the area shown in the figure.

In addition, the volume clutter intensity? C due to rain, snow, clouds, fog, etc. is obtained by the following formula.

The variable that determines ηv is (ψ304) γ, which means hourly rainfall, and the correlation is expressed as follows.

ηv (㎡ / ㎡) = 5.7 × 10 ^-14 γ ^1.6 / λ ⁴

At this time, the general distribution of standard rainfall that can occur around the world is 1 ~ 70mm / H, and these equations are divided into minimum and maximum levels, and the C / N area is calculated based on the X band case. It is as follows. In addition, the intensity θc of the ground clutter reflected from the ground or land is calculated by the following formula.

Here, the most important variable is γ, which is variable depending on the topography, and the minimum and maximum reflection ranges are about rocks and mountains. In this case, γ is in the range of about 0.03 to 0.15, and the C / N is calculated by dividing the maximum and the minimum based on this value, as shown in FIGS. 9 and 10.

Sea Clutter and Land Clutter among the clutters examined so far are scattered in the near field, although the range is somewhat different depending on the radar purpose. In this case, the clutter-to-noise region (hereinafter referred to as C / N) is achieved by STC processing, and in the case of volume clutter, it is achieved by FTC processing because the generation area is distributed over the entire range of the radar. do. In addition, gain compensation is required as much as the area removed from the STC and FTC. Such a clutter processing algorithm is not calculated and processed by a computer as in the prior art, and all possible situations are calculated and statistically modeled as needed from 2 to 512 steps or more, and then the algorithm is rapidly We devised a technique to permanently store in memory and select one at any time and apply it to signal processing. In other words, in order to improve a lot of absurdity, performance and speed reduction in the method of always calculating the algorithm and sending it to the computer, it is realized using ultra-high-capacity memory. This method is superior to the conventional methods in terms of performance such as speed, reliability, and detection ability. In the case of using the system processor, signal processing techniques of about 32 steps or less are mostly due to the processing power of the processor. It is possible to realize more than that. In other words, the visual discrimination ability that humans can see with eyes can be satisfied with this in the case of 16 stages, and in the case of black-and-white image display radar, but in the case of color image display, the ability to distinguish them by eyes is further increased. The invention can also be used in the color scheme.

In Fig. 5, the port selector 31 includes an STC port and a gain compensator 27 for inputting a function control signal 32, which is operated by an operator, from the adjuster in the display and the controller 21 to the STC 25. A function control signal is applied by selecting the FTC port directly to the data distributor 28 without passing through the gain port and the clutter algorithm memory 29 to. The function control signal 32 is a 4-bit port selection signal and an 8-bit function selection signal according to the signal processing step, and up to 256 algorithms can be selected for each port. These algorithm steps can be expanded as many times as necessary, but 64 steps are usually sufficient even in the color scheme, and can be extended to 256 or more steps in preparation for the ultra-high resolution image presentation technique that will be introduced later. The clutter algorithm memory 29 stores the STC algorithm and the gain compensation algorithm and sends the selected algorithm to the data distributor 28 according to the synchronization signal. The data distributor 28 distributes data from the clutter algorithm memory 29 and the FTC port to the STC 25, the FTC 26, and the gain compensator 27, respectively. The STC 25 removes sea clutter from the radar received signal after converting the digital data into analog. The FTC 26 removes the volume clutter by converting the digital value of the data divider 28 into an analog and then receiving the video signal from which the cancelling clutter is removed from the STC 25. The gain compensator 27 compensates for the level removed by the STC 25 and the FTC 26. The synchronization generator 30 extracts the PRT trigger signal from the radar received signal, generates an address of the clutter algorithm memory 29 according to the counter of the frequency generator, and sequentially accesses the memory to output data of the address.

6 is a detailed block diagram of the clutch adjuster and remover of the pulse radar of the present invention, in which the received signal reflected by the radiation radiation from the antenna 14 is subjected to video signal processing by the amplitude level controller 59 via the IF stage. After adjusting to an appropriate level, the surface clutter remover 47 removes the surface clutter component by a given level according to an algorithm. Among these signals, signal components reflected from rain, snow, clouds, and fog are removed by volume reflection clutter in the weather reflector 51 and finally compensated by a certain level in the gain compensator 55 to compensate for the constant flase-alarm. rate) to the signal processor. The purpose of the surface reflector eliminator 47 is to remove the strong signal forces reflected from the ground or near the antenna and the strong reflected signal that varies depending on the sea surface state from the sea surface state from the sea surface. In addition to the concept of eliminating clutter signal components, since the radar signal uses a reflected signal, approximately -9 dB attenuation theory is applied, so that some signal attenuation is inevitable.

Therefore, if these values are calculated using the above-mentioned formula and summed up as curves, they are the same as in FIGS. 13a, 13b, and 13c. FIG. 13A shows the areas where the sea is at its calmest and in the maximum typhoon. This section is divided into a minimum of 32 steps and a maximum of 256 steps and stored in the clutter algorithm memory 29 so that any one of the controllers on the front panel of the display device is selected. It latches in the clutter algorithm memory 29 via the clutter algorithm memory 29. At this time, one waveform data stored in the memory is compared with the PRT video signal currently received by the surface reflector eliminator 47 through the data divider 46 with 8 bits to realize signal attenuation. In addition, in the case of the weak weather reflection wave reflected from rain, snow, clouds, fog, etc., if a certain level is selected, the function switch (D / A converter 44 and the signal collector 49) passes through the data distributor 28. After confirming at 50), the weather echo canceller 51 attenuates the reflected signal in a very dense form to some extent. The application standard of this signal level is the distribution of the area as shown in Fig. 13C calculated by the above-mentioned formula, and it is about 1/3 to 1/2 of the sea reflection wave area. The signals from which the various clutters are removed from the surface reflector eliminator 47 and the meteorological reflector eliminator 51 are compensated by gain compensation data in the clutter algorithm memory 28. This data is converted into an analog signal in the D / A converter 52 and then the gain is compensated in the gain compensator 55 via the function amplifier 53 and the function converter 54. The gain compensation degree can be compensated for in all areas in which the level values removed by the surface reflector eliminator 47 and the meteorological reflector eliminator 51 are added together.

This signal processing is performed separately in the 1PRT section, and in order to execute this, the PRT trigger included in the received signal is detected and synchronized. That is, the PRT trigger detected by the system synchronization signal detector 48 is connected to the memory address generator 57 so that synchronization is performed every PRT. The frequency oscillated by the frequency generator 56 is supplied with a 16-bit address from the memory address generator 57 and supplied to the clutter algorithm memory 29, and is signaled by a total of 16 bits of the basic clock within one PRT period. Processing algorithm curves can be constructed, allowing the PRT to be used for any short or long radar.

13A, 13B, and 13C collectively show the clutter, and FIG. 13A shows marine clutter, FIG. 13B shows land clutter, and FIG. 13C shows this clutter.

14A to 14E illustrate a method of implementing a clutter algorithm, which is a main idea of the present invention, into a memory. FIG. 14A shows the possible range of the surface clutter, which is divided into 32 stages using the least algorithm as the algorithm 1 and the largest algorithm as the algorithm 32. 14B is a case in which the operator selects step 30 of the algorithm of FIG. 14A as an adjuster, and the selected algorithm is subdivided into 512 sample steps within the PRT interval, and sequentially accessed according to the address of the address generator of the synchronization generator. Print the data. The sample stage can also be varied as needed to handle both long and short PRT sections. FIG. 14c illustrates a PRT section and a dynamic range in relation to FIG. 14b. FIG. 14D illustrates the algorithm steps of FIG. 14A in the memory, and FIG. 14E illustrates the algorithm 30 in FIG. 14B in the memory. Such algorithms can be implemented directly in high-speed, high-capacity memory as needed to perform clutter removal without the help of a system processor.

In this way, the clock radar attenuator and eliminator of the present invention can significantly improve overall performance by reducing the load of the system processor by quickly processing the clutter elimination algorithm according to a pre-calculated result in a high speed memory without performing the clutter removal algorithm. By changing the high speed memory, various algorithms can be easily replaced, and the steps of the clutter removal algorithm can be implemented from 5 to 512, which can be applied to the color display, thereby improving the detection and capturing ability.

Claims (8)

A pulse radar video processor comprising an antenna, a transceiver, and a display, the video processor comprising: port selection means for selecting a corresponding port according to a function controller signal inputted from an adjuster; A high-speed large-capacity clutter algorithm memory means for storing an algorithm selected in advance according to the port selection means and outputting it on demand; Data distribution means for inputting data from the clutter algorithm memory and the port selection means and distributing the data to the means; STC means for removing surface reflection waves from the radar received signal according to the data value output from the clutter algorithm memory means; FTC means for removing the weather reflection wave in accordance with the signal input from the data distribution means; Gain compensating means for compensating for the level removed by said STC means and said FTC means in accordance with a signal input from said clutter algorithm memory through said data divider; And synchronization generating means for extracting synchronization from a radar received signal and holding a frequency generator to synchronize the clutter algorithm memory. 2. The clutter algorithm memory according to claim 1, characterized in that the clutter algorithm memory has an algorithm for removing clutter due to the ground surface or the sea surface, and an algorithm for compensating gain as much as attenuated by the STC means and the FTC means. Clutter attenuation control and removal of pulse radar. 2. The apparatus of claim 1, wherein the STC sum is a function of amplifying means for amplifying an analog signal of the D / A converting means and D / A converting means for converting the digital data inputted from the data distributor. A clutter of a pulse radar comprising: a function converting means for adjusting an output signal so as to be within a range of a clutter removing algorithm; and a surface reflecting wave removing means for removing clutter from a radar received signal according to the output of the function converting means. Attenuator and Eliminator. 2. The apparatus of claim 1, wherein the FTC means comprises: D / A conversion means for receiving digital data input from the data divider and converting the digital data into an analog signal, and signal collection means for appropriately amplifying the analog signal of the D / A conversion means; And a function switch means for receiving the output of said signal collecting means and checking whether it is within an algorithm range. 2. The apparatus of claim 1, wherein the gain compensating means comprises: D / A converting means for receiving digital data from the data distributor and converting the analog data into an analog signal, and functional amplifying means for amplifying the D / A converted analog signal. And a gain adjusting means for compensating for gain in accordance with said function converting means. 2. The apparatus according to claim 1, wherein the synchronization generating means comprises a synchronization signal detecting means for detecting a PRT trigger from a radar received signal and a frequency generating means for oscillating to synchronize the plurality of steps and the clutter algorithm memory according to the synchronization signal. A clutter attenuation control and removal device for a pulse radar comprising an address generating means for generating an address. 2. The control apparatus according to claim 1, wherein the port selection means includes an STC port for selecting data of the STC means and a gain port for selecting data of the gain compensation means and an FTC port for selecting data of the FTC means according to an adjuster. And a decoder for selecting the port according to the selection of the ruler. CLAIMS 1. A clutter removal method of a pulse radar comprising: selecting a clutter removal algorithm corresponding to sea and weather conditions observed by an operator; Extracting a clutter removal algorithm corresponding to the operator's selection from among a plurality of clutter removal algorithms corresponding to the grades of sea and weather conditions calculated and stored in advance; And removing clutter included in the received radar signal according to the extracted clutter removal algorithm, thereby using a clutter removal algorithm that is pre-calculated according to the grade of sea and weather conditions. Attenuation control and removal method characterized in that possible.