JP5770494B2 - Scan correlation processing device, radar device, and scan correlation processing method - Google Patents

Description

  The present invention relates to a scan correlation processing device, a radar device, and a scan correlation processing method.

In a radar apparatus used in a ship or the like, scan correlation processing is performed to remove noise (clutter) such as unnecessary reflected waves generated according to sea conditions and weather conditions. This scan correlation process is based on the previous scan correlation result obtained one scan before and the sweep data obtained in the current scan based on the position of the ship in the previous scan and the position and difference in the current scan. This is a process for detecting noise from the extracted current input value and removing the noise.
Here, the sweep data is data obtained every transmission / reception (sweep) by transmission of radio waves and reception of reflected waves of the radio waves in the radar apparatus.

  The calculation of the correlation in time-series continuous sweep data is performed by performing a predetermined operation on the sweep data value obtained by this sweep and the previous output value obtained based on the previous sweep. To obtain the current output value. Such calculation is performed by using a look-up table in which output values associated with each combination of the sweep data value and the previous output value are stored (for example, Patent Document 1). ).

JP-A-4-371145

However, in the radar apparatus, in order to be able to distinguish a slight amplitude difference between echoes on the screen display, it is necessary to increase the gradation of data by reducing the degree of quantization. In this case, since the number of values that the data can take increases, the number of combinations of sweep data values and output values stored in the lookup table increases. In addition, since the output value is stored for each combination of the sweep data value and the output value in the lookup table used for calculating the output value, the storage area required for the lookup table is remarkably increased. For example, when the possible values of the sweep data value and the output value are increased from 16 to 128, the output value corresponding to each combination stored in the lookup table is changed from 16 × 16 (= 256) to 128 × 128 ( = 16384), the storage area required for the lookup table is remarkably increased.
When the processing in the scan correlation processing is mounted on an ASIC (application-specific integrated circuit), a change that increases the data gradation increases the memory size required for mounting the lookup table, which increases the chip size of the ASIC, There is a problem that the manufacturing cost of the ASIC chip is increased.

  The present invention has been made to solve the above problem, and its purpose is to provide a scan correlation processing device capable of suppressing an increase in memory usage in scan correlation processing even when the resolution of radar images is improved. A radar apparatus and a scan correlation processing method are provided.

In order to solve the above problem, the present invention provides a class corresponding to an output value calculated one time before among a plurality of classes dividing a numerical range from a lower limit value to an upper limit value with respect to a value that can be taken by an output value. as well as select a grade selection unit for selecting a grade corresponding to the sweep data value input more of the grade obtained by dividing the numerical range from the lower limit to the upper limit for possible values for sweep data values, before once a grade that corresponds to the calculated output values, each combination of a grade that corresponds to the sweep data value, stored in advance instructions table associating an instruction code showing the operation for calculating the output value instruction An instruction code corresponding to a combination of a storage unit, a class corresponding to the output value calculated immediately before selected by the class selection unit, and a class corresponding to the input sweep data value is stored in the instruction storage unit. Read instruction command And an arithmetic unit for calculating an output value from the output value calculated once before and the input sweep data value based on the instruction code read by the instruction code reading unit. This is a scan correlation processing device.

  Further, the present invention is the above-described invention, wherein the instruction storage unit stores a plurality of instruction tables associated with each sea condition and weather condition, and the instruction code reading unit further includes: Selecting a command table corresponding to information indicating marine conditions and weather conditions inputted from the outside from a plurality of command tables stored in the command storage unit, and reading a command code from the selected command table, To do.

  Also, the present invention provides the scan correlation processing device according to the invention described above, a radar transmission / reception unit that inputs the sweep data value obtained for each transmission / reception of radio waves to the scan correlation processing device, and calculation in the scan correlation processing device. And an image output unit that outputs display image data based on the output value.

In addition, the present invention selects a class corresponding to the output value calculated one time before from among a plurality of classes in which a numerical range from a lower limit value to an upper limit value with respect to a value that the output value can take, and sweep data. A selection step for selecting a class corresponding to an input sweep data value from a plurality of classes that divides a numerical range from a lower limit value to an upper limit value with respect to possible values, and an output value calculated one time before a grade that corresponds, for each combination of the grade that corresponds to the sweep data values from the instruction storage unit that previously stores command table that contains the instruction code indicating an operation for calculating an output value, in the selection step Read the instruction code corresponding to the selected combination of the class corresponding to the output value calculated immediately before and the class corresponding to the input sweep data value from the instruction storage unit. And an operation step of calculating an output value from the output value calculated one time before and the input sweep data value based on the read instruction code in the instruction code reading step. Is a scan correlation processing method characterized by the above.

According to the present invention, the output value of the previous time and the output value of the previous time and the output value of the previous time and the input value of the current time, which are subject to the calculation of the scan correlation process, for each class combination that divides the numerical value range that each value can take. An instruction code indicating an operation for calculating an output value from the sweep data value is included in the instruction table.
As a result, the number of instruction codes included in the instruction table is a class that divides the number of combinations of the output value and the sweep data value one time before and the numerical range for the value that can be taken by the previous output value and the sweep data value. The number of combinations can be reduced, and the output value and the sweep data value can be kept constant regardless of the number of possible combinations of values. As a result, even when the resolution can be improved by reducing the values that can be taken by the output value and the sweep data value, an increase in the memory size required for mounting the instruction table (lookup table) can be suppressed, and in the scan correlation process An increase in memory usage and an increase in chip size can be suppressed.

It is a schematic block diagram which shows the structure of the radar apparatus in this embodiment. It is a block diagram which shows the structural example of the scan correlation process part 12 in the embodiment. It is a figure which shows the example of the command table memorize | stored in the command memory | storage part. It is a flowchart which shows the process which updates the display memory part 11 in the embodiment.

  Hereinafter, a scan correlation processing device, a radar device, and a scan correlation processing method according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic block diagram showing a configuration of a radar apparatus according to the present embodiment. In this radar apparatus, the antenna unit 2 receives a reflected wave (echo) reflected by a target from a radio wave transmitted from the antenna unit 2, and outputs image information corresponding to the received reflected wave to the display unit 16. is there.
Here, in the present embodiment, a case will be described in which the received signal output based on the reflected wave is quantized with 7-bit accuracy and the radar apparatus is installed on a ship.

  As shown in the figure, the radar apparatus includes a transmission / reception control unit 1, an antenna unit 2, an A / D (Analog-to-digital) conversion unit 3, a radar signal processing unit 4, a sweep memory unit 5, and an antenna. Rotation signal generation unit 6, distance angle signal control unit 7, gyro interface unit 8, coordinate conversion unit 9, speed information input unit 10, display memory unit 11, scan correlation processing unit 12, display information generation unit 13, graphic memory unit 14 An image composition unit 15 and a display unit 16.

The transmission / reception control unit 1 controls transmission / reception of the antenna unit 2 included in the own device.
Under the control of the transmission / reception control unit 1, the antenna unit 2 transmits radio waves from an antenna that rotates at a predetermined rotation period, receives radio waves reflected by a target, and the power level (amplitude) of the received radio waves. ) Is output to the A / D converter 3.

The A / D conversion unit 3 quantizes the reception signal input from the antenna unit 2 with 7 bits, and outputs the quantized digital signal to the radar signal processing unit 4.
The radar signal processing unit 4 performs a CFAR (Constant False Alarm Rate) process for suppressing the false alarm probability to a certain level or less using a known technique, and sweeps the result as sweep data. It is stored in the memory unit 5. In the sweep memory unit 5, sweep data in which the received power level of the reflected wave is digitized is stored in chronological order.

The antenna rotation signal generation unit 6 generates a pulse signal synchronized with the rotation angle of the antenna included in the antenna unit 2, and outputs the generated pulse signal to the distance angle signal control unit 7.
The gyro interface unit 8 detects the course of the ship in which the apparatus is installed, and outputs information indicating the detected course to the distance angle signal control unit 7.
The distance angle signal control unit 7 calculates an angle from the pulse signal input from the antenna rotation signal generation unit 6 and information input from the gyro interface unit 8, and sends information indicating the calculated angle to the coordinate conversion unit 9. Output.

The speed information input unit 10 is input with speed information indicating the speed at which the ship in which the apparatus is installed moves.
The coordinate conversion unit 9 calculates a read address and a write address in the display memory unit 11 based on the angle calculated by the distance angle signal control unit 7 and the speed information input to the speed information input unit 10. In other words, the coordinate conversion unit 9 performs conversion from the polar coordinate system to the orthogonal coordinate system using the position of the ship calculated based on the direction of the antenna and the course and speed information of the ship, and the display memory. A read address and a write address for selecting data corresponding to the sweep data stored in the sweep memory unit 5 among the data stored in the unit 11 are calculated.

  The display memory unit 11 has a plurality of storage areas for storing data obtained by one rotation of the antenna, that is, data for one scan, and stores PPI (Plan Position Indicator) display data. In addition, any one of the plurality of storage areas of the display memory unit 11 is selected using the read address and the write address calculated by the coordinate conversion unit 9.

The scan correlation processing unit 12 performs processing for removing noise (clutter) such as unnecessary reflected waves generated according to sea conditions and weather conditions based on the correlation between scans. Specifically, the scan correlation processing unit 12 reads out the previous output value, which is data obtained by the previous scan, from the display memory unit 11 and reads the current input value, which is data obtained by the current sweep. Read from the sweep memory unit 5.
The scan correlation processing unit 12 performs a calculation based on the correlation between the previous output value and the current input value, and stores the current output value, which is the calculation result, in the display memory unit 11. At this time, the previous output value is data stored in the storage area selected by the read address calculated by the coordinate conversion unit 9. The current output value is stored in the storage area selected by the write address calculated by the coordinate conversion unit 9.

The display information generation unit 13 generates display data to be displayed on the display unit 16 based on information indicating a nautical chart, an electronic bearing line, a VRM (Variable Range Marker), and the generated display data is graphically displayed. It is stored in the memory unit 14.
The image synthesis unit 15 synthesizes the data stored in the display memory unit 11 and the display data stored in the graphic memory unit 14 and outputs the synthesized data to the display unit 16.
The display unit 16 displays the data input from the image composition unit 15 as an image. The display unit 16 is, for example, an LCD (Liquid Crystal Display).

FIG. 2 is a block diagram illustrating a configuration example of the scan correlation processing unit 12 in the present embodiment. As shown in the figure, the scan correlation processing unit 12 includes a division threshold storage unit 121, a class selection unit 122, four pipeline registers 123a to 123d, an instruction storage unit 124, an instruction code reading unit 125, and three pipeline registers. 126a to 126c and a calculation unit 127 are provided.
The scan correlation processing unit 12 selects a class corresponding to each of the previous output value and the current input value, and an operation code for calculating the current output value based on the class corresponding to the previous output value and the current input value. The processing time is shortened by pipelining the three processes of the process of reading out and the process of calculating the current output value based on the read operation code.

  The division threshold value storage unit 121 has a plurality of values for dividing a numerical range (0 to 127) from a lower limit value to an upper limit value with respect to values that can be taken by the previous output value and the current input value that are data quantized by 7 bits. The threshold value is stored. For example, in the division threshold storage unit 121, the upper limit value of each class is stored in ascending order so that the numerical value range (0 to 127) is divided into eight classes.

  The class selection unit 122 compares the previous output value read from the display memory unit 11 and the current input value read from the sweep memory unit 5 with each threshold value stored in the segment threshold value storage unit 121, and outputs the previous output value. A class corresponding to each of the value and the current input value is selected, and a signal indicating the selected class is output. Here, the signal indicating the class output by the class selection unit 122 is a signal having a 4-bit information amount indicating any one of the eight classes.

The pipeline register 123a receives the previous output value read from the display memory unit 11, and stores the previous output value input. The pipeline register 123b receives the current input value read from the sweep memory unit 5 and stores the input current input value.
The pipeline register 123c receives a class corresponding to the previous output value from the class selection unit 122, and stores the input class. The pipeline register 123d receives a class corresponding to the current input value from the class selection unit 122, and stores the input class. Each of the pipeline registers 123a to 123d is configured by a storage element such as a flip-flop, for example, stores input signals and information at predetermined intervals, and outputs the stored signals and information. .

  The instruction storage unit 124 stores in advance an instruction table in which an instruction code indicating an operation for calculating the current output value is associated with each combination of the class corresponding to the previous output value and the class corresponding to the current input value. Has been. In the present embodiment, the instruction table includes instruction codes associated with all combinations (64 patterns) of classes corresponding to the previous output value (eight patterns) and classes corresponding to the current input value (eight patterns). Is remembered. The instruction code stored in the instruction storage unit 124 is information indicating an operation to be executed by the operation unit 127. Based on the information in the instruction code, one of the previous output value, the current input value, and the immediate value included in the instruction code is selected as the input value to be calculated. Similarly, the operation content for the input value is selected based on the information in the instruction code.

FIG. 3 is a diagram illustrating an example of an instruction table stored in the instruction storage unit 124. Here, for simplicity of explanation, there are two classes, “0” and “1”, corresponding to the previous output value and the current input value, and there are four combinations of each class. The case is shown.
As shown in the figure, when the combination of (previous output value, current output value) is (0, 0), an operation “subtract“ 1 ”from the previous output value and output” ”is associated. Yes. Further, (0, 1) is associated with an operation “output previous output value”, (1, 0) is associated with an operation “output immediate value“ 0 ””, (1, 1) is associated with an operation of “adding“ 1 ”to the current input value and outputting” ”.

  Returning to FIG. 2, the description will be continued. The class corresponding to the previous output value and the class corresponding to the current input value are input to the instruction code reading unit 125 from the pipeline registers 123c and 123d. The instruction code reading unit 125 reads out an instruction code corresponding to the input combination of the two classes from the instruction storage unit 124, and outputs the read instruction code.

  The pipeline register 126a receives the previous output value from the pipeline register 123a and stores the previous output value that is input. The pipeline register 126b receives the current input value from the pipeline register 123b and stores the current input value that is input. The pipeline register 126c receives the instruction code from the instruction code reading unit 125 and stores the input instruction code. Each pipeline register 126a to 126c is flipped in the same manner as the pipeline registers 123a to 123d. It is composed of a storage element such as a flop, and stores input signals and information at predetermined intervals, and outputs the stored signals and information.

  The arithmetic unit 127 receives the previous output value stored in the pipeline register 126a, the current input value stored in the pipeline register 126b, and the instruction code stored in the pipeline register 126c. . The computing unit 127 calculates the current output value from the previous output value and the current input value based on the input instruction code.

  FIG. 4 is a flowchart showing a process for updating the display memory unit 11 in the present embodiment. In the radar device, when the process of updating the display memory unit 11 is started, the coordinate conversion unit 9 uses polar coordinates using the position of the ship calculated based on the direction of the antenna and the course and speed information of the ship. Conversion from a system to an orthogonal coordinate system is performed, and the address of the display memory unit 11 corresponding to the sweep data stored in the sweep memory unit 5 is calculated (step S1).

  The scan correlation processing unit 12 reads the value (previous output value) stored in the address calculated by the coordinate conversion unit 9 (step S2), and also reads the sweep data value (current input value) from the sweep memory unit 5, Correlation processing is performed to calculate the current output value (step S3). This correlation processing is performed by performing an operation according to the combination of the previous output value and the current input value based on the configuration of the scan correlation processing unit 12 described above.

The scan correlation processing unit 12 stores the calculated current output value at the address calculated in step S2 in the storage area of the display memory unit 11 (step S4).
The values stored in the display memory unit 11 are updated by repeatedly performing the processes in steps S1 to S4 described above.

  In this way, by appropriately changing the threshold value stored in the classification threshold value storage unit 121 and the command table stored in the command storage unit 124, the class selection unit 122 sets the class for the current input value and the previous output value. It is possible to select and perform an arbitrary calculation according to an arbitrary amplitude. Accordingly, it is possible to set an appropriate scan correlation processing algorithm according to various sea conditions and weather conditions. In addition, by changing the information stored in the classification threshold value storage unit 121 and the command storage unit 124 as needed, it is possible to switch to scan correlation processing according to sea conditions and weather conditions in real time.

  As described above, in the scan correlation processing unit 12, the class selection unit 122 stores the numerical range from the lower limit value to the upper limit value with respect to the previous output value read from the display memory unit 11 in the segment threshold value storage unit 121. The class to which the previous output value belongs is selected. Further, the class selection unit 122 compares the numerical value range from the lower limit value to the condition value for the current input value read from the sweep memory unit 5 with each threshold value stored in the segment threshold value storage unit 121, Select the class to which the input value belongs. The instruction code reading unit 125 reads from the instruction storage unit 124 the instruction code associated with the combination of the class of the previous output value selected by the class selection unit 122 and the class of the current input.

In this way, the previous output value and the current input value are classified into classes, and the instruction code is associated with each combination of the class corresponding to the previous output value and the class corresponding to the current input value. The number of instruction codes stored in the unit 124 can be made smaller than the combination of the value that can be taken by the previous output value and the value that can be taken by the current input value. As a result, even when the resolution between the previous output value and the current input value is improved, an increase in the memory size required for the implementation of the instruction table can be suppressed, an increase in memory usage in the scan correlation process, and a scan correlation. The increase in size of the ASIC chip on which the processing is mounted can be suppressed.
Also, the size of the instruction code does not depend on the resolution of the previous output value and the current input value, that is, the amount of information. Since there is no need to change, even when the resolution between the previous output value and the current input value is improved, the increase in memory size required to implement the instruction table can be suppressed, and the memory usage in scan correlation processing increases. And the enlargement of the ASIC chip which implements the scan correlation processing can be suppressed.

  In the present embodiment, the case where the instruction storage unit 124 stores one instruction table has been described. However, the instruction storage unit 124 may store a plurality of instruction tables. In this case, each of the plurality of instruction tables is associated with each sea condition and weather condition, and information indicating the sea condition and weather condition input from the outside is input to the instruction code reading unit 125. Then, the instruction code reading unit 125 may select an instruction table corresponding to the input information indicating the sea condition and the weather condition, and read the instruction code from the selected instruction table. Thereby, the command table according to the sea condition and the weather condition can be selected, the scan correlation process according to the sea condition and the weather condition can be performed, and the noise removal accuracy can be improved.

  DESCRIPTION OF SYMBOLS 1 ... Transmission / reception control part, 2 ... Antenna part, 3 ... A / D conversion part, 4 ... Radar signal processing part, 5 ... Sweep memory part, 6 ... Antenna rotation signal generation part, 7 ... Distance angle signal control part, 8 ... Gyro interface unit, 9 ... coordinate conversion unit, 10 ... speed information input unit, 11 ... display memory unit, 12 ... scan correlation processing unit, 13 ... display information generation unit, 14 ... graphic memory unit, 15 ... image synthesis unit, 16 ... Display unit, 121 ... Division threshold storage unit, 122 ... Class selection unit, 123a, 123b, 123c, 123d ... Pipeline register, 124 ... Instruction storage unit, 125 ... Instruction code reading unit, 126a, 126b, 126c ... Pipeline Register, 127 ... arithmetic unit

Claims (4)

Select the class corresponding to the output value calculated one time before among the multiple classes that divide the numerical range from the lower limit value to the upper limit value for the value that the output value can take, and for the value that the sweep data value can take A class selection unit that selects a class corresponding to an input sweep data value from a plurality of classes that divides a numerical range from a lower limit value to an upper limit value;
A grade that corresponds to the output value calculated before once each combination of a grade that corresponds to the sweep data value, stores in advance a command table associating an instruction code showing the operation for calculating the output value An instruction storage unit,
Instruction code reading for reading out an instruction code from the instruction storage unit according to a combination of a class corresponding to the output value calculated immediately before selected by the class selection unit and a class corresponding to the input sweep data value And
A scan unit comprising: an arithmetic unit that calculates an output value from the output value calculated one time before and the input sweep data value based on the instruction code read by the instruction code reading unit; Correlation processing device. The scan correlation processing device according to claim 1,
The command storage unit stores a plurality of command tables associated with each sea condition and weather condition,
The instruction code reading unit further selects an instruction table corresponding to information indicating sea conditions and weather conditions inputted from the outside from a plurality of instruction tables stored in the instruction storage unit, and the selected instruction table A scan correlation processing device characterized by reading an instruction code from The scan correlation processing device according to claim 1 or 2,
A radar transceiver for inputting the sweep data value obtained for each transmission / reception of radio waves to the scan correlation processor;
A radar apparatus comprising: an image output unit that outputs display image data based on an output value calculated by the scan correlation processing apparatus. Select the class corresponding to the output value calculated one time before among the multiple classes that divide the numerical range from the lower limit value to the upper limit value for the value that the output value can take, and for the value that the sweep data value can take A class selection step for selecting a class corresponding to the input sweep data value from among a plurality of classes dividing the numerical range from the lower limit value to the upper limit value;
A grade that corresponds to the output value calculated before once for each combination of a grade that corresponds to the sweep data value, stores in advance command table that contains the instruction code indicating an operation for calculating an output value An instruction code corresponding to a combination of a class corresponding to the output value calculated in the previous class selected in the class selection step and a class corresponding to the input sweep data value An instruction code reading step for reading from the storage unit;
The instruction code reading step includes a calculation step of calculating an output value based on the read instruction code and the output value calculated one time before and the input sweep data value. Scan correlation processing method.

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