JP2007071623A - Secondary monitoring radar device and error correction method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance an error correction rate on mode S response data. <P>SOLUTION: Based on the waveform of a response signal from a mode S transponder, whether or not the mode S response data can be erroneous is bit-by-bit determined by a reliability determination part 125 to generate reliability data. Based on the reliability data, bits which can be erroneous of the response data are corrected one bit at a time. This error correction process is repetitively executed until all the errors are eliminated. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a secondary surveillance radar (SSR) device that monitors an aircraft equipped with a mode S transponder, and an error correction method that corrects an error in response data to an inquiry signal of the SSR device.

  The SSR mode S is an apparatus for acquiring information related to monitoring for air traffic control by transmitting a question signal to a transponder mounted on an aircraft and receiving various information as a response signal to the question signal. is there. There are two types of transponders: the ATCRBS transponder conventionally used and the mode S transponder.

  In the SSR mode S, the inquiry signal transmission period is divided into an all-call period and a roll call period, and the aircraft is captured within the beam irradiation period (beam dwell). The all call period is a period for acquiring the mode S transponder and the ATCRBS transponder. The roll call period is a period for individual questions and responses to the Mode S transponder.

  By the way, in the response data of the mode S transponder, an error may occur due to the deterioration of the fruit of the mode S transponder and the ATCRBS transponder and the radio wave environment, and the SSR mode S may not be able to grasp the response normally. For this reason, in the SSR mode S, processing for correcting an error in the mode S response data is performed.

A technique related to the error correction processing of the mode S response data is disclosed in Non-Patent Document 1.
ICAO (International Civil Aviation Organization), “MANUAL OF THE SECONDARY SURVEILLANCE RADAR (SSR) SYSTEMS (Doc 9684)”, SECOND EDITION-1998, Appendix 1 “MODE S CYCLIC POLYNOMIAL ERROR DETECTION AND CORRECTION”

  However, in the conventional error correction processing method, it is possible to correct when the error position interval is within 24 bits in the mode S response data, but there are cases where the error pulse at a position away from 24 bits cannot be corrected. However, in an actual environment, there are many cases where an error pulse is generated away from 24 bits, and the error correction rate of the mode S response data is reduced.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a secondary monitoring radar apparatus and an error correction method for improving the error correction rate of mode S response data.

  In order to achieve the above object, the invention according to claim 1 is a transmission means for transmitting an interrogation signal to an aircraft equipped with a mode S transponder, and a response from the mode S transponder to the interrogation signal transmitted by the transmission means. Receiving means for receiving a signal; binarization processing means for binarizing the response signal to generate response data; and possibility of error for each bit of the response data based on the waveform of the response signal A reliability determination means for generating reliability data for each bit by determining whether there is any error, and correcting one bit at a time of a possible error in the response data based on the reliability data, And error correction means for repeatedly executing an error correction process until the error is eliminated.

  The invention according to claim 2 is characterized in that the error correction means executes an error correction process when the number of bits with a possibility of error is equal to or less than a preset number of correction execution designations.

  The invention according to claim 3 is an error correction method for correcting an error in response data to a question signal transmitted by a secondary monitoring radar apparatus that monitors an aircraft equipped with a mode S transponder, the response from the mode S transponder. Reliability determination for generating reliability data for each bit by determining whether or not there is a possibility of error for each bit of response data generated by binarizing the response signal based on the waveform of the signal And an error correction step of correcting one bit at a time of a possibility of an error in the response data based on the reliability data, and executing an error correction process repeatedly until all errors are eliminated. Features.

  According to a fourth aspect of the invention, there is provided a correction execution number determining step for determining whether or not the number of bits with a possibility of error is equal to or less than a preset number of correction execution designations. Error correction is executed when the number of possible bits is less than or equal to the specified number of correction executions.

  According to the present invention, the reliability data is generated by determining whether there is an error for each bit of the response data based on the waveform of the response signal from the mode S transponder, and based on the reliability data. Bits that may cause an error in the response data are corrected one bit at a time, and the error correction process is repeatedly performed until all errors are eliminated, so that the error correction rate of the mode S response data can be improved.

  The best mode for carrying out the secondary monitoring radar apparatus and error correction method of the present invention will be described below with reference to the drawings.

  FIG. 1 is a schematic configuration diagram showing a secondary monitoring radar device and an onboard device according to an embodiment of the present invention.

  The secondary monitoring radar apparatus 100 includes an interrogator 1 and an antenna 2. The interrogator 1 includes a transceiver 1a that transmits an interrogation signal to the monitoring airspace via the antenna 2 and receives a response signal, and a signal processing unit 1b that generates an interrogation signal and acquires and outputs a target report for each aircraft from the response signal. With. The secondary monitoring radar apparatus 100 is installed on the ground and captures an aircraft on which the upper apparatus 200 is mounted.

  The onboard device 200 is mounted on an aircraft and includes a transponder 3 and an antenna 4. The transponder 3 is a mode S transponder or an ATCRBS transponder. The transponder 3 includes a transceiver 3a that receives the interrogation signal from the secondary monitoring radar apparatus 100 and returns a response signal, and a signal processing unit 3b that generates a response signal for the received interrogation signal.

  FIG. 2 is a block diagram showing the configuration of the secondary monitoring radar apparatus shown in FIG. 1 in more detail. As shown in FIG. 2, the secondary monitoring radar device 100 transmits an interrogation signal and receives an answer signal, an antenna 2 that generates an interrogation signal, a transmission control unit 16 that generates the interrogation signal, and an interrogation signal generated by the transmission control unit 16. The channel management unit 15 that manages the transmission channel, the transmitter 1a1 that outputs the interrogation signal generated by the transmission control unit 16 to the circulator 11, the interrogation signal from the transmitter 1a1 is output to the antenna 2, and the antenna 2 A circulator 11 that outputs a response signal to the receiver 1a2, a receiver 1a2 that receives the response signal and outputs it to either the mode S response processing unit 12 or the ATCRBS response processing unit 13, and a mode S response to the mode S response signal A mode S response processing unit 12 for generating data and an ATCRBS response for generating mode A / C response data for the ATCRBS response signal It includes a processing section 13, and a monitoring processor 14 that controls the channel management unit 15.

  The monitoring processing unit 14 includes a correlation processing unit 14a. The correlation processing unit 14a acquires mode S response data, and performs known correlation processing on the mode S response data. Further, the correlation processing unit 14a acquires mode A / C response data and performs known correlation processing on the mode A / C response data.

  Here, the operation of the secondary monitoring radar apparatus 100 shown in FIG. 2 will be described. The inquiry signal transmission period is divided into an all-call period and a roll call period. First, in the all call period, the transmission control unit 16 generates an interrogator signal including the interrogator identification II and outputs it to the transmitter 1a1. The interrogator identification II is an identification number assigned to the interrogator 1 of the secondary monitoring radar apparatus 100. For example, II = 15 is set in the question signal. The transmitter 1a1 outputs a transmission signal to the antenna 2 via the circulator 11.

  The antenna 2 transmits an interrogation signal to the monitored airspace, receives a response signal from the transponder of the aircraft that has received the interrogation signal, and outputs the response signal to the receiver 1a2 via the circulator 11.

  Then, the receiver 1a2 outputs the mode S response signal from the mode S transponder to the mode S response processing unit 12, and outputs the mode A / C response signal from the ATCRBS transponder to the ATCRBS response processing unit 13.

  The mode S response processing unit 12 generates mode S all call response data for the mode S response signal and outputs it to the monitoring processing unit 14 during the all call period. Further, it is determined whether or not the interrogator identification II included in the mode S all-call response data matches the interrogator 1 own interrogator identification II = 15 included in the question signal. The matching mode S all call response data is subject to the next correlation processing, and the non-matching mode S all call response data is not subject to processing. Further, the mode S response processing unit 12 acquires the mode S address from the mode S all call response data. The mode S address is an identification number assigned to the transponder of each aircraft. For example, the mode S address “801015” is included in the mode S all call response data.

  The ATCRBS response processing unit 13 generates mode A / C response data for the ATCRBS response signal and outputs the mode A / C response data to the monitoring processing unit 14.

  Then, the correlation processing unit 14a acquires the mode S all call response data and performs a known correlation process on the mode S all call response data. Based on the result, the correlation processing unit 14a specifies the mode S response signal transmitted from the same aircraft. Further, the correlation processing unit 14a acquires mode A / C response data and performs known correlation processing on the mode A / C response data. Based on the result, the correlation processing unit 14a identifies the mode A / C response signal transmitted from the same aircraft.

  Thereafter, the roll call period starts, and the monitoring processing unit 14 outputs position information indicating the distance and direction in which the aircraft exists to the channel management unit 15 based on the correlation processing result in the correlation processing unit 14a. And the channel management part 15 manages the transmission channel of the question signal produced | generated by the transmission control part 16 based on position information.

  Then, the transmission control unit 16 generates an inquiry signal including the mode S address “801015” acquired from the mode S all call response data in the all call period, and outputs it to the transmitter 1a1. The transmitter 1a1 outputs an interrogation signal to the antenna 2 via the circulator 11.

  The antenna 2 transmits an interrogation signal to the monitored airspace, receives a response signal from the mode S transponder of the aircraft that has received the interrogation signal, and outputs the response signal to the receiver 1a2 via the circulator 11. The receiver 1a2 outputs the mode S response signal from the mode S transponder to the mode S response processing unit 12.

  The mode S response processing unit 12 generates mode S roll call response data corresponding to the mode S response signal and outputs the mode S roll call response data to the monitoring processing unit 14. Further, it is determined whether or not the mode S address included in the mode S roll call response data matches the mode S address “801015” of the question signal. The matching mode S roll call response data is subject to the next correlation processing, and the non-matching mode S roll call response data is not subject to processing.

  The correlation processing unit 14a acquires mode S roll call response data, performs known correlation processing on the mode S roll call response data, and outputs a target report.

  Next, the mode S response processing unit 12 will be described. First, processing in the conventional mode S response processing unit will be described. FIG. 3 is a block diagram showing a configuration of a mode S response processing unit in a conventional secondary radar apparatus.

  As shown in FIG. 3, the mode S response processing unit 12A in the conventional secondary radar apparatus binarizes the preamble pulse detection unit 121 that detects the preamble pulse of the mode S response signal and the mode S response signal. The binarization processing unit 122 that generates the mode S response data, and the process of determining “0” and “1” from the pulse train of the mode S response data and decoding the parity part (AP or PI field) (hereinafter decoding process) And a decoding processing unit 123 that performs comparison of the interrogator identification II or the mode S address, and determines whether or not there is a possibility of an error for each bit of the mode S response data. A reliability determination unit 125 that generates error data, an error correction processing unit 126 that performs error correction of the mode S response data, and an error And a error determination processing unit 127 performs the same processing as the error judgment processing unit 124 for the error corrected mode S reply data in over correction processing unit 126.

  First, the preamble pulse detection unit 121 detects a preamble pulse indicating a mode S response signal, outputs the mode S response signal and the detection enable to the binarization processing unit 122, and determines the reliability of the mode S response signal. Output to the unit 125.

  The binarization processing unit 122 binarizes the mode S response signal to generate mode S response data, and outputs the mode S response data to the decoding processing unit 123. The decode processing unit 123 decodes the mode S response data and outputs the decoded mode S response data to the error determination processing unit 124.

  Then, the error determination processing unit 124 determines whether or not the interrogator identification II included in the mode S response data matches the interrogator 1 own interrogator identification II = 15 included in the question signal during the all-call period. In the roll call period, it is determined whether or not the mode S address included in the mode S response data matches the mode S address “801015” of the question signal. If they match, the mode S response data is output to the correlation processing unit 14a as a normal response to the question. On the other hand, if they do not match, the error determination processing unit 124 outputs the mode S response data to the error correction processing unit 126.

  The reliability determination unit 125 determines whether or not there is a possibility of an error for each bit of the response data based on the waveform of the mode S response signal, generates reliability data, and uses the reliability data as an error determination processing unit It outputs to 124.

  Thereafter, the error correction processing unit 126 performs known error correction processing on the mode S response data input from the error determination processing unit 124 based on the reliability data, and converts the error corrected mode S response data into an error. The result is output to the determination processing unit 127.

  Then, the error determination processing unit 127 performs the same processing as the error determination processing unit 124, and if they match, the mode S response data is output to the correlation processing unit 14a as a normal response to the question. If they do not match, the mode S response data is discarded as not being processed by the correlation processing unit 14a.

  4 is a diagram showing mode S response data, FIG. 5 is a diagram showing an example in which error correction of mode S response data is possible, and FIG. 6 is a diagram showing an example in which error correction of mode S response data is not possible.

  As shown in FIG. 4, the mode S response data includes an 8 μs preamble pulse indicating a mode S response, a 32-bit or 88-bit protocol field, and a portion representing a 24-bit AP field or PI field. The last 24 bits are AP field for response data for individual questions, and the PI field is response data for all-call questions.

  The mode S response data shown in FIG. 5 has an interference wave in the first bit and the second bit, and the first bit is originally “1”, but is determined to be “0”, and the second bit is originally “0”. Shows an example in which “1” is determined. Further, the mode S response data shown in FIG. 6 has an interference wave in the 1st bit and the 56th bit, and the 1st bit is originally “1” but is determined to be “0”, and the 56th bit is originally “0”. An example in which “1” is determined despite the fact is shown.

  In the conventional mode S response processing unit 12A shown in FIG. 3, the error can be corrected when the error position interval is within 24 bits, but the error cannot be corrected when the distance is longer than 24 bits. That is, the error of the mode S response data shown in FIG. 5 can be corrected, but the mode S response data shown in FIG. 6 cannot be corrected because the error position interval is longer than 24 bits.

  Here, the mode S response processing unit 12 according to the embodiment of the present invention will be described. FIG. 7 is a block diagram showing the configuration of the mode S response processing unit in the secondary radar apparatus according to the embodiment of the present invention. In the constituent elements of the mode S response processing unit 12 shown in FIG. 7, the same constituent elements as those in FIG.

  7 is different from the mode S response processing unit 12A shown in FIG. 3 in that an error correction processing unit 128 is added. The error correction processing unit 128 performs error correction processing on the mode S response data that is determined not to match by the error determination processing unit 127 after the error correction processing is performed by the error correction processing unit 126, based on the reliability data.

  Here, a procedure for performing error correction processing by the error correction processing unit 128 will be described. FIG. 8 is a flowchart showing a procedure of error correction processing according to the embodiment of the present invention.

  First, in step S10, the error correction processing unit 128 has a bit of low reliability in the mode S response data input from the error determination processing unit 127 based on the reliability data input from the reliability determination unit 125. Determine if there is. When there is a bit with low reliability (YES), the process proceeds to step S20. When there is no bit with low reliability (NO), error correction cannot be performed, so the mode S response data is discarded as not being processed by the correlation processing unit 14a.

  Next, in step S20, the error correction processing unit 128 determines whether or not the number n of unreliable bits is equal to or less than the correction execution designation number. When the number is less than the specified number of correction executions (YES), the process proceeds to step S30. When the number is not less than the specified number of correction executions (NO), it is difficult to correct the error, so the mode S response data is not processed by the correlation processing unit 14a. It is discarded as.

In the error correction processing of the error correction processing unit 128, a maximum of 2 ⁿ −1 calculations are performed. For example, when n = 10, it is necessary to perform 1023 calculations. However, if the number n of unreliable bits is large, the probability that error correction can be performed is low even if error correction processing is performed. For example, when the mode S responses of two aircraft overlap, there is almost no probability of error correction. Therefore, the number of correction execution designations is set in advance, and a restriction is set so that correction processing is not executed when the number n of unreliable bits is larger than the number of correction execution designations.

  Next, in step S30, the error correction processing unit 128 changes the bit having low reliability from “0” to “1” or “1” to “0” bit by bit, and decodes the AP field or the PI field.

  Next, in step S40, the error correction processing unit 128 determines whether or not the interrogator identification II included in the mode S response data matches the interrogator 1 own interrogator identification II included in the question signal during the all-call period. to decide. In the roll call period, it is determined whether or not the mode S address included in the mode S response data matches the mode S address of the question signal. If they match (YES), the mode S response data is output to the correlation processing unit 14a, assuming that the response is a normal response with the error corrected. If they do not match (NO), the process proceeds to step S50.

In step S50, the error correction processing unit 128 determines whether or not the unreliable bit changing process has been executed 2 ⁿ −1 times. When it is executed 2 ⁿ −1 times (YES), error correction cannot be performed, so the mode S response data is discarded as not being processed by the correlation processing unit 14a. When not executed 2 ⁿ −1 times (NO), the process returns to step S30 and the subsequent processing is repeated.

  Here, the error correction procedure will be specifically described. 9 is a diagram showing the relationship between the mode S response data and the reliability data, FIG. 10 is a diagram showing the first change process, FIG. 11 is a diagram showing the second change process, and FIG. 12 is the third change process. FIG. In FIG. 9, the reliability data “0” indicates that there is a high possibility of an error and the reliability is low, and the reliability data “1” indicates that the reliability is high.

In FIG. 9, the 1st bit and the 56th bit are reliability data “0”, which indicates the possibility that the mode S response data is erroneously determined. In this case, since the number of unreliable bits is n = 2, the process of changing the unreliable bits is executed 2 ² −1 = 3 times.

  First, as shown in FIG. 10, the error correction processing unit 128 changes the first bit of the mode S response data from “0” to “1”, decodes the AP field or the PI field, and generates the mode S address. Alternatively, it is determined whether or not the interrogator identification II matches. If there is a match, it is assumed that the first bit is judged to be an incorrect value, and the value of the first bit is changed to correct the error. If they do not match, the process proceeds to the second process.

  The second time, as shown in FIG. 11, the error correction processing unit 128 changes the first bit and the 56th bit of the mode S response data from “0” to “1”, decodes the AP field or the PI field, It is determined whether the mode S address or the interrogator identification II matches. If they match, it is assumed that the values of the first bit and the 56th bit are changed and the error can be corrected. If they do not match, the process proceeds to the third process.

  In the third time, as shown in FIG. 12, the error correction processing unit 128 changes the 56th bit of the mode S response data from “0” to “1”, decodes the AP field or the PI field, and sets the mode S address or It is determined whether or not the interrogator identification II matches. If they match, it is assumed that the 56th bit value has been changed and the error has been corrected. If they do not match, it is determined that the error cannot be corrected.

  As described above, according to the secondary monitoring radar apparatus and the error correction method according to the embodiment of the present invention, there is a possibility of an error for each bit of the mode S response data based on the waveform of the response signal from the mode S transponder. The reliability determination unit 125 determines whether or not there is reliability data, and based on the reliability data, the error correction processing unit 128 corrects a bit that may cause an error in the mode S response data bit by bit. Then, since error correction processing is repeatedly executed until all errors are eliminated, errors at positions apart from 24 bits can be corrected. In addition, a plurality of errors within 24 bits can be corrected. For this reason, the error correction rate of the mode S response data can be improved.

It is a schematic block diagram which shows the secondary monitoring radar apparatus and aircraft side apparatus which concern on embodiment of this invention. It is a block diagram which shows the structure of the secondary monitoring radar apparatus shown in FIG. 1 in detail. It is a block diagram which shows the structure of the mode S response process part in the conventional secondary radar apparatus. It is a figure which shows mode S response data. It is a figure which shows the example which can carry out the error correction of mode S response data. It is a figure which shows the example which cannot carry out the error correction of mode S response data. It is a block diagram which shows the structure of the mode S response process part in the secondary radar apparatus of embodiment of this invention. It is a flowchart which shows the procedure of the error correction process of embodiment of this invention. It is a figure which shows the relationship between mode S response data and reliability data. It is a figure which shows the change process of the 1st time. It is a figure which shows the change process of the 2nd time. It is a figure which shows the change process of the 3rd time.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Interrogator 1a, 3a Transceiver 1b, 3b Signal processing part 2, 4 Antenna 3 Transponder 1a1 Transmitter 1a2 Receiver 11 Circulator 12, 12A Mode S response processing part 13 ATCRBS response processing part 14 Monitoring processing part 14a Correlation processing part 15 Channel Management unit 16 Transmission control unit 100 Secondary monitoring radar device 121 Preamble pulse detection unit 122 Binarization processing unit 123 Decoding processing unit 124, 127 Error determination processing unit 125 Reliability determination unit 126, 128 Error correction processing unit 200 Onboard device

Claims (4)

Transmitting means for transmitting an interrogation signal to an aircraft equipped with a mode S transponder;
Receiving means for receiving a response signal from the mode S transponder to the interrogation signal transmitted by the transmitting means;
Binarization processing means for binarizing the response signal to generate response data;
Reliability determination means for determining whether there is an error for each bit of the response data based on the waveform of the response signal and generating reliability data for each bit;
Error correction means for correcting one bit at a time of a possibility of error in the response data based on the reliability data and executing error correction processing repeatedly until all errors are eliminated Secondary monitoring radar device.   The secondary monitoring radar apparatus according to claim 1, wherein the error correction unit executes an error correction process when the number of bits with a possibility of error is equal to or less than a predetermined number of correction execution designations. An error correction method for correcting an error in response data to an interrogation signal transmitted by a secondary monitoring radar device that monitors an aircraft equipped with a mode S transponder,
Based on the waveform of the response signal from the mode S transponder, it is determined whether or not there is a possibility of an error for each bit of the response data generated by binarizing the response signal. A reliability determination step for generating data;
An error correction step of correcting one bit at a time of a possibility of error in the response data based on the reliability data, and executing an error correction process repeatedly until all errors are eliminated Error correction method. A correction execution number determination step for determining whether or not the number of bits with a possibility of error is equal to or less than a preset number of correction execution designations;
The error correction method according to claim 3, wherein the error correction step executes error correction when the number of bits with a possibility of error is equal to or less than the correction execution designated number.

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