Secondary radar interception method, interception program, and recording medium

Abstract

To efficiently specify information such as a radar signal and a position of a secondary radar.SOLUTION: In the interception method of the secondary radar 1 of the present invention, the two reception signals B11 and B12 obtained by receiving the peripheral signal including the radar signal A1 transmitted from the secondary radar 1 by the two reception devices 11 and 12 are acquired, and the first to third pulses P1 to P3 of the radar signal A1 included in the reception signals B11 and B12 are specified based on the relationship between the two reception signals B11 and B12. The present invention also relates to an interception program for causing a computer 20 to execute each step of the interception method, and further relates to a computer-readable recording medium in which the interception program is recorded.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a secondary radar interception method for intercepting radar signals transmitted from a secondary radar, a secondary radar interception program used for intercepting radar signals transmitted from a secondary radar, and a computer-readable recording medium having the interception program recorded thereon. [Background technology]

[0002] A secondary radar used for air traffic control transmits an interrogation signal to a moving object such as an aircraft and receives a response signal transmitted from a transponder in the moving object in response to the interrogation signal. Based on the relationship between the interrogation signal and the response signal, information such as the position of the moving object is obtained, and this information is used for air traffic control.

[0003] Such secondary radars are typically installed within airports or on the surrounding grounds. They include a directional interrogation antenna that transmits an interrogation signal and an SLS (side lobe suppression) antenna that transmits an SLS signal. The directional interrogation antenna rotates so that its main lobe, which transmits the strongest interrogation signal, can be directed around the entire periphery of the interrogation antenna.

[0004] In a typical three-pulse SLS secondary radar, the interrogation signal includes multiple combinations of a P1 pulse and a P3 pulse that is transmitted approximately 8 μsec or 21 μsec after the P1 pulse, and the SLS signal includes multiple P2 pulses that are transmitted approximately 2 μsec after the P1 pulse. In other words, the radar signal transmitted from the secondary radar includes multiple pulse groups consisting of P1 to P3 pulses. In each pulse group of the radar signal, the time difference between the P1 and P3 pulses varies depending on the type of interrogation signal. Types of interrogation signals include interrogations for identifying aircraft bodies, interrogations for determining aircraft altitude, etc.

[0005] In such a radar signal, the signal strength of the P1 and P3 pulses is greater than the signal strength of the P2 pulse in the main lobe direction, and the signal strength of the P1 and P3 pulses is less than the signal strength of the P2 pulse in the side lobe direction. A technology is employed that utilizes these characteristics of the signal strengths of the P1 to P3 pulses to identify the P1 and P3 pulses in the main lobe direction.

[0006] To understand the noise conditions at airports and their surrounding areas, local governments and other organizations monitor the flight paths of aircraft flying into and around airports. For example, this monitoring involves intercepting radar signals consisting of interrogation signals and SLS signals from secondary radars, and response signals from aircraft transponders, and identifying aircraft flight paths based on these intercepted signals. For this reason, devices are installed around airports to intercept surrounding signals, including radar signals and response signals.

[0007] However, when many aircraft are waiting in the sky around the airport, when many aircraft are conducting training around the airport, etc., the response signals of many aircraft will be flying around the airport. Also, when there are reflecting objects such as aircraft and large buildings around the airport, the radar signals that reach the interception device directly from the secondary radar (hereinafter referred to as "direct radar signals" as needed) and the radar signals that reach the interception device after being reflected from the reflecting objects from the secondary radar (hereinafter referred to as "reflected radar signals" as needed) will be mixed together.

[0008] In this situation, it is difficult to extract the radar signal from the intercepted signal, which is a problem. To address this issue, various secondary radar interception techniques have been proposed that allow the radar signal to be extracted.

[0009] An example of such a secondary radar interception technology is a secondary radar interception technology that extracts, from a plurality of intercepted pulses contained in a radar signal intercepted by a single interception device, a plurality of extracted pulses having a signal strength that exceeds, within a certain period of time, a threshold value that is set to be smaller than the signal strength of the direct radar signal in the main lobe direction and larger than the signal strength of the reflected radar signal; if the extracted pulses have the same number of peaks, the same time difference between the peaks, and the same difference in reception strength between the peaks, the extracted pulses are identified as being included in the direct radar signal transmitted from the same secondary radar and as one of the same P1 to P3 pulses; and if a non-extracted pulse that does not exceed the threshold appears in the same period as the extracted pulse identified above, the non-extracted pulse is identified as being included in the direct radar signal transmitted from the same secondary radar as the extracted pulse and as one of the same P1 to P3 pulses as the extracted pulse (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0010] [Patent Document 1] Patent Publication No. 2014-231995 Summary of the Invention [Problem to be solved by the invention]

[0011] However, the signal strength of the direct radar signal in the main lobe direction and the signal strength of the reflected radar signal generally vary depending on individual conditions, such as the secondary radar, reflectors, and installation conditions of the interception device. Therefore, in order to set a threshold as in the example of the secondary radar interception technology described above, it is necessary to adjust the threshold appropriately according to the individual conditions. Adjusting such a threshold is difficult and requires a great deal of effort.

[0012] In the above example of the interception technology, when a computer is required to perform a calculation process to determine whether the number of peaks, the time difference between the peaks, and the difference in reception intensity between the peaks are the same for the extracted pulses, this calculation process places a huge load on the computer and is therefore inefficient. Also, in the above example of the interception technology, there is a problem in clarifying the position of the secondary radar when the position of the secondary radar is unknown.

[0013] Furthermore, the time difference between multiple pulse groups in a radar signal is not necessarily constant. In particular, in the case of a staggered system, this time difference is not constant, and for example, the time difference may change regularly. Furthermore, in the case of a random staggered system, this time difference changes randomly. In contrast, in the example of the above-mentioned interception technology, non-extracted pulses can only be identified if they appear at the same period as extracted pulses. In other words, in the example of the above-mentioned interception technology, non-extracted pulses cannot be identified in the case of a staggered system, particularly in the case of a random staggered system.

[0014] In view of this situation, it is desirable that a method for intercepting secondary radar, as well as an interception program and a computer-readable recording medium on which the program is recorded, be able to efficiently identify information such as the radar signal and position of the secondary radar, and furthermore, it is desirable that the information of the secondary radar be efficiently identified even in the case of a staggered method, particularly a random staggered method. [Means for solving the problem]

[0015] In order to solve the above problem, a secondary radar interception method according to a first aspect is a method for intercepting a radar signal transmitted from a secondary radar, wherein the secondary radar has a directional interrogation antenna that transmits an interrogation signal while rotating, and an omnidirectional SLS antenna that transmits an SLS signal, and the radar signal includes a plurality of pulse groups each consisting of a combination of a first and a third pulse of the interrogation signal and a second pulse of the SLS signal, and in each pulse group, the second pulse is transmitted at a predetermined first interval from the transmission of the first pulse, and the third pulse is transmitted at a predetermined second interval from the transmission of the first pulse, the method for intercepting secondary radar includes the steps of: acquiring first and second received signals obtained by receiving peripheral signals including the radar signal by first and second receiving devices, respectively; and identifying, from the first received signal, a plurality of pulses that appear at a certain reception timing difference u with respect to the plurality of pulses of the second received signal as the first to third pulses. The reception timing difference u can be a value u (=d / v) obtained by dividing the difference in distance d to the secondary radar between the first and second receiving devices by the speed of light v, which is the speed of radio waves.

[0016] In order to solve the above problem, a method for intercepting a secondary radar according to a second aspect is a method for intercepting a radar signal transmitted from a secondary radar, wherein the secondary radar has a directional interrogation antenna that transmits an interrogation signal while rotating, and an omnidirectional SLS antenna that transmits an SLS signal, the radar signal includes a plurality of pulse groups each consisting of a combination of a first and a third pulse of the interrogation signal and a second pulse of the SLS signal, and in each pulse group, the second pulse is transmitted at a predetermined first interval from the transmission of the first pulse, and the third pulse is transmitted at a predetermined second interval from the transmission of the first pulse. The method includes a step of acquiring first and second received signals, which are peripheral signals including a radar signal received by first and second receiving devices, respectively; a step of calculating a relative shift time u (=d / v) of the first and second received signals based on a difference in distance d between the first and second receiving devices to the secondary radar and the speed of light v, which is the speed of radio waves, to make the timings of the first and second received signals coincide with each other based on the transmission timing of the radar signal, and performing a correction to relatively shift the first and second received signals by the shift time u; and a step of identifying, after the correction, from the first received signal, multiple pulses that appear at the same timing as the multiple pulses of the second received signal as the first to third pulses.

[0017] The secondary radar intercepting programs according to the first and second aspects cause a computer to execute the steps of the secondary radar intercepting methods according to the first and second aspects, respectively.

[0018] The recording medium according to the first and second aspects is a computer-readable recording medium on which the secondary radar intercept program according to the first and second aspects is recorded. [Effects of the Invention]

[0019] The secondary radar interception method and secondary radar interception program and recording medium according to the first and second aspects respectively make it possible to efficiently identify information such as the radar signal and position of the secondary radar, and furthermore, even in the case of a staggered method, particularly a random staggered method, it is possible to efficiently identify information of the secondary radar. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 is a plan view schematically showing a secondary radar, first and second receiving devices, and a computing device according to each of the first to fourth embodiments. [Figure 2] FIG. 2 is a flowchart for explaining the secondary radar intercept method according to the first embodiment. [Figure 3] Fig. 3(a) is a graph schematically showing a radar signal transmitted from a secondary radar according to each of the first to sixth embodiments, and Fig. 3(b) is a graph schematically showing another radar signal transmitted from another secondary radar. [Figure 4] FIG. 4 is a graph schematically showing the first and second received signals according to each of the first to fourth embodiments side by side. [Figure 5] FIG. 5 is a graph schematically showing the first and second received signals according to the first embodiment side by side in a state after correction. [Figure 6] FIG. 6 is a hardware configuration diagram of a computer for executing a secondary radar interception program according to the first embodiment. [Figure 7] FIG. 7 is a flowchart for explaining the secondary radar intercept method according to the second embodiment. [Figure 8] FIG. 8 is a flowchart for explaining the secondary radar intercept method according to the third embodiment. [Figure 9] FIG. 9 is a flowchart for explaining a secondary radar intercept method according to the fourth embodiment. [Figure 10]FIG. 10 is a plan view schematically showing the secondary radar, the first to third receiving devices, and the arithmetic device according to each of the fifth and sixth embodiments. [Figure 11] FIG. 11 is a flowchart for explaining a secondary radar intercept method according to the fifth embodiment. [Figure 12] FIG. 12 is a graph showing a schematic arrangement of received signals from the first to third receiving devices according to the fifth and sixth embodiments. [Figure 13] FIG. 13 is a flowchart for explaining the secondary radar intercept method according to the sixth embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0021] The following describes a secondary radar interception method, an interception program, and a recording medium according to each of the first to sixth embodiments. The secondary radar (hereinafter simply referred to as "radar" as necessary) used in each embodiment is for air traffic control. However, the radar can also be used for purposes other than air traffic control.

[0022] Furthermore, the recording medium according to the present embodiment may be a semiconductor memory such as a RAM (Random Access Memory), a ROM (Read Only Memory), or a flash memory, an optical disk such as a CD-ROM, a DVD-ROM, or a Blu-ray, a magnetic disk, etc. However, the recording medium is not limited to these.

[0023] Here, we will briefly touch on the interception methods, interception programs, and recording media (hereinafter referred to as "interception methods, etc." as necessary) according to the first to sixth embodiments. The interception methods, etc. according to the first and second embodiments each make it possible to identify multiple pulses contained in a radar signal transmitted from at least one radar using multiple receiving devices. The interception method, etc. according to the third embodiment makes it possible to identify the location of one radar using at least two receiving devices. The interception method, etc. according to the fourth embodiment makes it possible to identify the locations of multiple radars using at least two receiving devices. The interception methods, etc. according to the fifth embodiment each make it possible to identify the location of one radar using at least three receiving devices. The interception method, etc. according to the sixth embodiment makes it possible to identify the locations of multiple radars using at least three receiving devices.

[0024] "First embodiment" A secondary radar interception method, an interception program, and a recording medium according to the first embodiment will be described.

[0025] "Outline of secondary radar interception method" 1 to 5, the interception method of the secondary radar 1 according to this embodiment is outlined as follows: Referring to Figures 1 and 2, the interception method according to this embodiment is used to intercept a radar signal A1 transmitted from the radar 1.

[0026] As shown in Figure 1, radar 1 has a directional interrogation antenna 1a that rotates to transmit an interrogation signal. Radar 1 also has an omnidirectional SLS (side lobe suppression) antenna 1b that transmits an SLS (side lobe suppression) signal. Typically, radar 1 is installed at an airport with a runway L used for takeoff and landing of aircraft J, or on the surrounding grounds.

[0027] Referring to FIG. 3(a), the radar signal A1 includes a plurality of pulse groups G1 each consisting of a combination of a first pulse P1 and a third pulse P3 of the interrogation signal and a second pulse P2 of the SLS signal. In each pulse group G1, the second pulse P2 is transmitted a predetermined first interval t1 after the transmission of the first pulse P1, and the third pulse P3 is transmitted a predetermined second interval t2 after the transmission of the first pulse P1. Such a radar signal A1 is transmitted via radio waves. Typically, the frequency of the radio waves is approximately 1030 MHz. However, the frequency of the radio waves is not limited to this.

[0028] In this embodiment and the following embodiments, the timing of signal transmission, reception, etc. is shown in terms of time (sec). In Fig. 3(a) and Figs. 3(b), 4, 5, and 12 described below, the horizontal axis T represents time (sec), and the vertical axis I represents signal strength (dBm). However, the timing of signal transmission, reception, etc. can also be shown in terms of signal phase (degrees).

[0029] 2 and 4, the interception method includes a step (signal acquisition step) S11 of acquiring first and second received signals B1 and B2, which are peripheral signals including a radar signal A1 received by first and second receiving devices 11 and 12, respectively. Note that in Fig. 4, the solid line B1 indicates the first received signal B1, and the solid line B2 indicates the second received signal B2.

[0030] 2 and 5, the interception method includes a step (signal correction step) S12 of correcting at least one of the first and second received signals B1, B2. In the signal correction step S12, at least one of the first and second received signals B1, B2 is corrected in accordance with the difference in distance d (m, meters) to the radar 1 between the first and second receiving devices 11, 12 so as to match the timing of the first and second received signals B1, B2 based on the transmission timing of the radar signal A1. Furthermore, the interception method includes a step (pulse identification step) S13, after the signal correction step S12, of identifying, from the first received signal B1, multiple pulses P1 to P3 that appear at the same timing as the multiple pulses of the second received signal B2, as the first to third pulses P1 to P3.

[0031] In Fig. 5, only the second received signal B2 is corrected as an example. However, only the first received signal B1 can also be corrected. Alternatively, both the first and second received signals B1 and B2 can be corrected. In Fig. 5, the solid line B1 indicates the first received signal B1, and the solid line B2 indicates the second received signal B2.

[0032] "Details of secondary radar interception methods" 1 to 5, the interception method of the secondary radar 1 according to this embodiment can be specifically as follows: Referring to Fig. 3(a), typically, in the radar signal A1, the first interval t1 can be about 2 μsec, and the second interval t2 can be about 8 μsec or about 21 μsec.

[0033] For example, when the interrogation signal is related to an interrogation for identifying the aircraft body (in the case of Mode A), the second interval t2 is about 8 μsec. For example, when the interrogation signal is related to an interrogation for identifying the aircraft altitude (in the case of Mode C), the second interval t2 is about 21 μsec. However, the first interval and the second interval are not limited to these.

[0034] 1, radar signal A1 reaches each of receiving devices B1 and B2 directly from radar 1. In other words, radar signal A1 is not reflected by reflectors such as buildings or nearby aircraft on its way from radar 1 to receiving devices B1 and B2.

[0035] 4 and 5, each of the received signals B1 and B2 acquired in the signal acquisition step S11 includes not only the radar signal A1 but also noise N. For example, the noise N includes an aircraft's response signal to a signal other than the radar signal A1, an interrogation signal other than Mode A and C (e.g., a Mode S interrogation signal) transmitted from the radar 1, a reflected radar signal that has been reflected from a reflector and reached each of the receiving devices B1 and B2, and external signals transmitted from external facilities other than the radar 1, aircraft, etc. Examples of external signals include radio waves from an aircraft's ACAS (Airborne Collision Avoidance System).

[0036] The signal pulses that may be included in the noise N in this way may appear at irregular timing differences between the first and second received signals B1, B2, may not be periodic, may appear only at momentary time intervals, may appear at timing differences relative to other pulses that are significantly different from the timing differences between the first to third pulses P1 to P3, and / or may have a signal strength that is smaller than the first to third pulses P1 to P3 of the radar signal A1.

[0037] Furthermore, in the radar signal A1, the timing difference between the multiple pulse groups G1 is much larger than the timing difference between the first to third pulses P1 to P3 of each pulse group G1. Therefore, the first to third pulses P1 to P3 and the pulse group G1 that includes them appear at timings sufficiently separated from noise N other than the pulse group G1 in most cases. Due to these characteristics of the noise N and the characteristics of the radar signal A1, the above-mentioned interception method makes it possible to sufficiently distinguish the first to third pulses P1 to P3 of the radar signal A1 from the noise N in each of the received signals B1 and B2.

[0038] Next, in a signal correction step S12, a relative shift time u (sec) (=d / v) of the first and second reception signals B1 and B2 is calculated based on the difference in distance d (m) to the radar 1 between the first and second reception devices 11 and 12 and the radio wave speed, i.e., the speed of light v (m / sec). Then, the first and second reception signals B1 and B2 are relatively shifted by the shift time u.

[0039] As a result, the timings of the first and second received signals B1 and B2 will match with each other based on the transmission timing of the radar signal A1. Note that if the distance difference d is 0 (zero) m and the shift time u is also 0 (zero) sec, the first and second received signals B1 and B2 can be considered to be relatively shifted by 0 (zero) sec.

[0040] Even when there are multiple radars 1 and 2, such as when there is radar 1 and one or more other radars 2 as shown in Fig. 1, if pulse group G2 of another radar signal A2 (shown in Fig. 3(b)) transmitted from another radar 2 is treated as noise N, it is possible to identify pulses P1 to P3 of radar signal A1 transmitted from radar 1 by the above interception method. Then, by repeating the above interception method while switching between radar 1 and another radar 2, it is possible to identify pulses P1 to P3 of all of the multiple radar signals A1 and A2 transmitted from the multiple radars 1 and 2.

[0041] "Secondary radar interception program and recording medium" The interception program and recording medium for the secondary radar 1 according to this embodiment will be described with reference to Figures 2 and 6. The interception program according to this embodiment is used to intercept the radar signal A1 transmitted from the radar 1.

[0042] Such an interception program is configured to cause the computer 20 to execute each of the steps S11 to S13 of the interception method according to this embodiment. That is, the interception program can cause the computer 20 to execute at least the signal acquisition step S11, the signal correction step S12, and the pulse identification step S13. Furthermore, the recording medium according to this embodiment is a computer-readable recording medium on which such an interception program is recorded.

[0043] "Interception System" 1 and 6, an interception system configured as hardware including an interception program and a recording medium according to this embodiment will be described. The interception system includes the first and second receiving devices 11 and 12. The interception system also includes a computer 20 that can execute the interception program. The computer 20 is communicably connected to the receiving devices 11 and 12 via a communication network 30.

[0044] The computer 20 can also be referred to as the arithmetic device 20 according to this embodiment. Although not particularly shown, such an arithmetic device 20, i.e., the computer 20, has a signal acquisition unit, a signal correction unit, and a pulse identification unit configured to enable the signal acquisition step S11, the signal correction step S12, and the pulse identification step S13, respectively.

[0045] The computer 20 has a bus 21, a CPU (Central Processing Unit) 22, an HDD (Hard Disk Drive) 23, a RAM (Random Access Memory) 24, a ROM (Read Only Memory) 25, a communication interface 26, and an input / output interface 27. The computer 20 may further have an optical disk drive 28 capable of reading optical disks, and a flash memory 29 that is detachable from the computer 20. The CPU 22, HDD 23, RAM 24, ROM 25, communication interface 26, input / output interface 27, optical disk drive 28, and flash memory 29 are connected directly or indirectly via the bus 21. The communication interface 26 is connected to the communication network 30.

[0046] The interception program is recorded on the HDD 23, which is a recording medium of the computer 20. However, the interception program can also be recorded on a recording medium other than the HDD.

[0047] As described above, the method for intercepting the secondary radar 1 according to this embodiment includes a step (signal acquisition step) S11 of acquiring first and second received signals B1, B2 received by the first and second receiving devices 11, 12, respectively, as peripheral signals including the radar signal A1; a step (signal correction step) S12 of correcting at least one of the first and second received signals B1, B2 in accordance with the difference in distance d to the secondary radar 1 between the first and second receiving devices 11, 12, so as to match the timing of the first and second received signals B1, B2 based on the transmission timing of the radar signal A1; and a step (pulse identification step) S13 of identifying, after the correction, from the first received signal B1, multiple pulses P1 to P3 that appear at the same timing as the multiple pulses of the second received signal B2 as first to third pulses P1 to P3.

[0048] According to this interception method, the first to third pulses P1 to P3 can be efficiently identified throughout the entire transmission period of the radar signal A1 by the simple process of comparing the first and second received signals B1 and B2 after the above correction. In particular, regardless of the difference in transmission timing between the multiple pulse groups G1 of the radar signal A1, the above comparison can identify the first to third pulses P1 to P3 from each of the first and second received signals B1 and B2, so that the first to third pulses P1 to P3 can be efficiently identified even in the case of a staggered system, particularly a random staggered system. Therefore, information such as the radar signal A1 of the secondary radar 1 can be efficiently identified, and further, even in the case of a staggered system, particularly a random staggered system, the information of the secondary radar 1 can be efficiently identified.

[0049] Furthermore, the interception program for the secondary radar 1 according to this embodiment can provide the same effects as the interception method according to this embodiment. The recording medium according to this embodiment can provide the same effects as the interception method and interception program according to this embodiment.

[0050] "Second embodiment" A secondary radar interception method, an interception program, and a recording medium according to the second embodiment will be described.

[0051] "Secondary Radar Intercept Method" 1, 3(a), 4, and 7, the interception method for the secondary radar 1 according to this embodiment is as follows: Referring to FIGS. 1 and 3(a), the interception method according to this embodiment, like the first embodiment, is used to intercept a radar signal A1 transmitted from the secondary radar 1. As shown in FIG. 7, this interception method includes a signal acquisition step S21 similar to the signal acquisition step S11 of the first embodiment.

[0052] 4 and 7, the interception method includes a step (pulse identification step) S22 of identifying, from a first received signal B1, multiple pulses P1-P3 that appear at a certain reception timing difference u relative to the multiple pulses of a second received signal B2 as first to third pulses P1-P3 of a radar signal A1. As an example of a condition for the pulse identification step S22, the difference in distance d to the radar 1 between the first and second receiving devices 11, 12 can be within approximately 200 km, and the certain reception timing difference u can be within a search range of approximately -668 μsec to approximately +668 μsec. As another example of a condition for the pulse identification step S22, the difference in distance d to the radar 1 between the first and second receiving devices 11, 12 can be within approximately 70 km, and the certain reception timing difference u can be within a search range of approximately -234 μsec to approximately +234 μsec. However, the distance difference and search range are not limited to these.

[0053] More specifically, the pulse identification step S22 can be performed as follows: First, one or more pulses of the first received signal B1 that are shifted within the search range for each of the plurality of pulses in the second received signal B2 are selected, and the reception timing differences of the one or more pulses selected in this manner are calculated and recorded. From the plurality of reception timing differences calculated and recorded, a plurality of identical reception timing differences u are extracted. A plurality of pulses P1 to P3 of the first received signal B1 that respectively correspond to the plurality of identical reception timing differences u are identified as first to third pulses P1 to P3.

[0054] "Secondary radar interception program, recording medium, and interception system" 6 and 7, an interception program and a recording medium for the secondary radar 1 according to this embodiment will be described. Furthermore, an interception system configured as hardware including the interception program and a recording medium according to this embodiment will be described. The interception program according to this embodiment, like the interception program according to the first embodiment, is used to intercept radar signal A1 transmitted from radar 1.

[0055] Such an interception program is configured to cause the computer 20 to execute each step S21 and S22 of the interception method according to this embodiment. That is, the interception program can cause the computer 20 to execute at least the signal acquisition step S21 and the pulse identification step S22. Furthermore, the recording medium according to this embodiment is a computer-readable recording medium on which such an interception program is recorded.

[0056] Although not particularly shown, in the interception system according to this embodiment, computer 20 has a signal acquisition unit and a pulse identification unit configured to enable signal acquisition step S21 and pulse identification step S22, respectively, instead of the signal acquisition unit, signal correction unit, and pulse identification unit of the first embodiment. Except for the configuration of computer 20, the interception system according to this embodiment is similar to the interception system according to the first embodiment.

[0057] As described above, the interception system for the secondary radar 1 according to this embodiment includes a step (signal acquisition step) S21 of acquiring first and second received signals B1, B2 received by the first and second receiving devices 11, 12, respectively, as peripheral signals including the radar signal A1, and a step (pulse identification step) S22 of identifying, from the first received signal B1, multiple pulses P1 to P3 that appear with a certain reception timing difference u relative to the multiple pulses of the second received signal B2, as first to third pulses P1 to P3.

[0058] According to this interception method, the first to third pulses P1 to P3 can be efficiently identified throughout the entire transmission period of the radar signal A1 through the simple process of identifying multiple pulses P1 to P3 that appear at a constant reception timing difference u between the first and second received signals B1 and B2. In particular, since the first to third pulses P1 to P3 can be identified from each received signal B1 and B2 as described above regardless of the difference in transmission timing between the multiple pulse groups G1 of the radar signal A1, the first to third pulses P1 to P3 can be efficiently identified even in the case of a staggered system, particularly a random staggered system. Therefore, information such as the radar signal A1 of the secondary radar 1 can be efficiently identified, and further, information from the secondary radar 1 can be efficiently identified even in the case of a staggered system, particularly a random staggered system.

[0059] Furthermore, the interception program for the secondary radar 1 according to this embodiment can provide the same effects as the interception method according to this embodiment. The recording medium according to this embodiment can provide the same effects as the interception method and interception program according to this embodiment.

[0060] "Third embodiment" A secondary radar interception method, an interception program, and a recording medium according to the third embodiment will be described.

[0061] "Secondary Radar Intercept Method" 1, 3(a), 4, and 8, the interception method for the secondary radar 1 according to this embodiment is as follows: Referring to FIGS. 1 and 3(a), the interception method according to this embodiment, like the interception method according to the second embodiment, is used to intercept a radar signal A1 transmitted from the secondary radar 1. As shown in FIG. 8, this interception method includes a signal acquisition step S31 that is similar to the signal acquisition step S21 of the second embodiment.

[0062] 4 and 8, the interception method includes a representative pulse extraction step S32 of extracting a representative pulse group G11, which is one of the plurality of pulse groups G1, from each of the received signals B1 and B2 within an antenna rotation period h (shown in FIG. 3(a)) required for one rotation of the interrogation antenna 1a. The representative pulse groups G11 of the first and second received signals B1 and B2 have common characteristics that indicate their identity.

[0063] Such a common feature can be the first and third pulses P1, P3 in the main lobe direction, which are a combination of two pulses P1, P3 that show the largest amplitude within an antenna rotation period h. In this case, the representative pulse extraction step S32 can include identifying, from each of the received signals B1, B2, the two pulses P1, P3 that appear at a second interval t2 with respect to each other within the antenna rotation period h and that show the largest amplitude as the first and third pulses P1, P3 in the main lobe direction, respectively.

[0064] Note that when two pulses P1, P3 appearing at the second interval t2 relative to each other are a combination showing the largest amplitude, this refers to when the average value of the amplitudes of these two pulses P1, P3 is the largest, or when the amplitude of one of these two pulses P1, P3 is the largest. Furthermore, this representative pulse extraction step S32 can also include identifying, from the multiple pulses of each received signal B1, B2, a pulse P2 that appears within the antenna rotation period h, the first interval t1 after the reception timing of the first pulse P1 in the main lobe direction, as the second pulse P2 in the main lobe direction.

[0065] Alternatively, the common feature may be common amplitudes of the first to third pulses P1 to P3 and first and second intervals t1 and t2. In this case, the representative pulse extraction step S32 may compare multiple pulses between the first and second received signals B1 and B2 within the antenna rotation period h, and through this comparison, search for and extract a representative pulse group G11 having common amplitudes of the first to third pulses P1 to P3 and first and second intervals t1 and t2 between the first and second received signals B1 and B2. This is because the first to third pulses P1 to P3 of the representative pulse group G11 extracted from each received signal B1 and B2 depend on the first to third pulses P1 to P3 of the pulse group G1 of the same radar signal A1.

[0066] The interception method includes a step (representative timing difference calculation step) S33 of calculating a representative timing difference r between representative pulse groups G11 of the first and second received signals B1, B2. Note that the representative timing difference r can be the timing difference between the first, second, or third pulses P1 to P3 in the representative pulse groups G11 of the first and second received signals B1, B2.

[0067] The representative timing difference r is negative if the representative pulse group G11 of the first received signal B1 appears after the representative pulse group G11 of the second received signal B2, and positive if the representative pulse group G11 of the first received signal B1 appears before the representative pulse group G11 of the second received signal B2.

[0068] The interception method includes a step (adjacent pulse extraction step) S34 of extracting, from the second reception signal B2, a pulse group G12 that appears at a timing closest to the representative pulse group G11 of the first reception signal B1 as an adjacent pulse group G12. The interception method also includes a step (reception timing difference calculation step) S35 of calculating a reception timing difference u between the representative and adjacent pulse groups G11, G12 that are adjacent to each other. Note that the reception timing difference u can be the timing difference between the first, second, or third pulses P1 to P3 in the representative pulse group G11 of the first reception signal B1 and the adjacent pulse group G12 of the second reception signal B2.

[0069] The reception timing difference u is a negative value when the representative pulse group G11 of the first reception signal B1 appears after the adjacent pulse group G12 of the second reception signal B2, and a positive value when the representative pulse group G11 of the first reception signal B1 appears before the adjacent pulse group G12 of the second reception signal B2.

[0070] The interception method includes a step (position determination step) S36 of determining the position of the radar 1 based on the antenna rotation period h, the representative timing difference r, the reception timing difference u, and the positions of the first and second receiving devices 11, 12. Specifically, such position determination step S36 can be performed as follows.

[0071] 1 and 3(a), the antenna rotation period h is typically 4 or 10 seconds, and in many cases, the antenna rotation period h is known. In this case, this known value can be used as the antenna rotation period h. However, if the antenna rotation period h is unknown, the interception method may include a step (period calculation step) of calculating the antenna rotation period h based on the interval between adjacent representative pulse groups G11 transmitted from the radar 1 in the first or second received signal B1 or B2. For example, in this period calculation step, adjacent representative pulse groups G11 can be searched for and the antenna rotation period h can be identified based on the fact that the antenna rotation period h is 4 or 10 seconds.

[0072] Furthermore, the rotation direction of the interrogation antenna 1a (indicated by arrow W1 in FIG. 1 and FIG. 10, which will be described later) is typically clockwise in a planar view. In light of this, when the representative timing difference r is a negative value, it can be determined that the radar 1 is located on the left side when viewed from the first receiving device 11 to the second receiving device 12 in a planar view. When the representative timing difference r is a positive value, it can be determined that the radar 1 is located on the right side when viewed from the first receiving device 11 to the second receiving device 12 in a planar view.

[0073] However, if the rotation direction of the interrogation antenna 1a is unknown, it is advisable to roughly estimate in advance whether the radar 1 is located to the left or right in a plan view when looking at the second receiving device 12 from the first receiving device 11. Note that the determination and estimation of the rotation direction (indicated by arrow W2 in FIG. 1 and FIG. 10 described later) and position of the interrogation antenna 2a of another radar 2 described later are also similar to the determination and estimation of the rotation direction and position of the interrogation antenna 1a of the radar 1.

[0074] Referring to Figures 1 and 4, based on the antenna rotation period h, the representative timing difference r, and the reception timing difference u, the angular difference θ (degrees) between the first and second receiving devices 11, 12 centered on the position of the radar 1 is calculated using the following (Equation 1).

[0075] θ = (ru) / h×360 (degrees) (Formula 1)

[0076] Based on the reception timing difference u and the speed of light v, the difference in distance d (m) to the radar 1 between the first and second receiving devices 11, 12 is calculated by the following (Equation 2).

[0077] d = v×u (m) (Formula 2)

[0078] Furthermore, the distance e (m) between the first and second receiving devices 11, 12 is calculated based on the positions of the first and second receiving devices 11, 12. Then, in a planar view, using the positions of the first and second receiving devices 11, 12 as a reference, the position that satisfies the conditions that the angle difference θ between the first and second receiving devices 11, 12, the distance difference d to the radar 1 between the first and second receiving devices 11, 12, and the distance e between the first and second receiving devices 11, 12 are all predetermined values ​​can be determined as the position of the radar 1.

[0079] "Secondary radar interception program, recording medium, and interception system" 6 and 8, an interception program and a recording medium for the secondary radar 1 according to this embodiment will be described. Furthermore, an interception system configured as hardware including the interception program and a recording medium according to this embodiment will be described. The interception program according to this embodiment, like the interception program according to the second embodiment, is used to intercept radar signal A1 transmitted from radar 1.

[0080] Such an interception program is configured to cause the computer 20 to execute each of the steps S31 to S36 of the interception method according to this embodiment. That is, the interception program causes the computer 20 to execute at least the signal acquisition step S31, the representative pulse extraction step S32, the representative timing difference calculation step S33, the adjacent pulse extraction step S34, the reception timing difference calculation step S35, and the position identification step S36. Furthermore, the recording medium according to this embodiment is a computer-readable recording medium having such an interception program recorded thereon.

[0081] Although not shown in the figures, in the interception system according to this embodiment, the computer 20 has a signal acquisition unit, a representative pulse extraction unit, a representative timing difference calculation unit, an adjacent pulse extraction unit, a reception timing difference calculation unit, and a position identification unit configured to respectively execute the signal acquisition step S31, the representative pulse extraction step S32, the representative timing difference calculation step S33, the adjacent pulse extraction step S34, the reception timing difference calculation step S35, and the position identification step S36, instead of the signal acquisition unit and pulse identification unit of the second embodiment. Except for the configuration of the computer 20, the interception system according to this embodiment is similar to the interception system according to the second embodiment.

[0082] As described above, the method for intercepting the secondary radar 1 according to this embodiment includes a step (signal acquisition step) S31 of acquiring first and second received signals B1, B2, which are peripheral signals including the radar signal A1 received by the first and second receiving devices 11, 12, respectively; a step (representative pulse extraction step) S32 of extracting a representative pulse group G11, which is one of a plurality of pulse groups G1, from a plurality of pulses in each of the received signals B1, B2, within an antenna rotation period h during one rotation of the interrogation antenna 1a, wherein the representative pulse groups G11 of the first and second received signals B1, B2 have common characteristics to indicate their identity; The method includes a step S33 of calculating a representative timing difference r between the groups G11 (representative timing difference calculation step), a step S34 of extracting from the second received signal B2 the pulse group G12 that appears at the timing closest to the representative pulse group G11 of the first received signal B1 as the adjacent pulse group G12 (adjacent pulse extraction step), a step S35 of calculating the reception timing difference u between the adjacent representative and adjacent pulse groups G11, G12 (reception timing difference calculation step), and a step S36 of identifying the position of the secondary radar 1 based on the antenna rotation period h, the representative timing difference r, the reception timing difference u, and the positions of the first and second receiving devices 11, 12.

[0083] According to this interception method, even if the position of one secondary radar 1 is unknown, the position of the secondary radar 1 can be efficiently identified based on the representative timing difference r and reception timing difference u, which can be calculated by the simple process described above, and the known positions of the first and second receiving devices 11 and 12. In particular, regardless of the difference in transmission timing between the multiple pulse groups G1 of the radar signal A1, the representative timing difference r and reception timing difference u can be easily identified using the representative pulse group G11 extracted from the multiple pulses of the first and second received signals B1 and B2. Therefore, even in the case of a staggered method, particularly a random staggered method, the position of the secondary radar 1 can be efficiently identified as described above. Therefore, information such as the position of the secondary radar 1 can be efficiently identified, and further, even in the case of a staggered method, particularly a random staggered method, information about the secondary radar 1 can be efficiently identified.

[0084] In the interception method for the secondary radar 1 according to this embodiment, the common feature can be the first and third pulses P1 and P3 in the main lobe direction, which are a combination of two pulses P1 and P3 that exhibit the largest amplitude within the antenna rotation period h. This interception method can efficiently extract the representative pulse group G11 based on prominent features such as the maximum amplitude.

[0085] Alternatively, in the interception method for the secondary radar 1 according to this embodiment, the common feature can be that the first to third pulses P1 to P3 have common amplitudes and common first and second intervals t1 and t2. According to this interception method, it is possible to efficiently extract representative pulse groups G11 as needed in any period within the antenna rotation period h.

[0086] Furthermore, the interception program for the secondary radar 1 according to this embodiment can provide the same effects as the interception method according to this embodiment. The recording medium according to this embodiment can provide the same effects as the interception method and interception program according to this embodiment.

[0087] "Fourth embodiment" A secondary radar interception method, an interception program, and a recording medium according to the fourth embodiment will be described.

[0088] "Secondary Radar Intercept Method" 1, 3(a) and (b), 4, and 9, the interception method for secondary radars 1 and 2 according to this embodiment is as follows: Referring to Fig. 1 and Fig. 3(a) and (b), the interception method according to this embodiment is used to intercept multiple radar signals A1 and A2 transmitted from multiple secondary radars 1 and 2, respectively.

[0089] The interception method according to this embodiment, like the interception method according to the third embodiment, can be used to intercept a radar signal A1 transmitted from a secondary radar 1. Furthermore, the interception method according to this embodiment can be used to intercept another radar signal A2 transmitted from another secondary radar 2. In FIG. 1, two radars 1 and 2 are shown. However, the interception method according to this embodiment can also be used to intercept three or more radar signals transmitted from three or more secondary radars.

[0090] 1, similar to radar 1, radar 2 has a directional interrogation antenna 2a that transmits an interrogation signal while rotating. Radar 2 also has an omnidirectional SLS antenna 2b that transmits an SLS signal. Typically, radar 2, similar to radar 1, is installed at an airport with a runway L used for takeoff and landing of aircraft J, or at a site surrounding the airport.

[0091] 3(b), another radar signal A2 includes a plurality of pulse groups G2 each consisting of a combination of first to third pulses P1 to P3, similar to the radar signal A1. Referring to FIGS. 4 and 9, the interception method includes a step (signal acquisition step) S41 of acquiring first and second received signals B1 and B2 received by first and second receiving devices 11 and 12, respectively, from peripheral signals each including a plurality of radar signals A1 and A2.

[0092] The interception method includes a step (search target extraction step) S42 of extracting, from each received signal B1, B2, a plurality of target pulses P1-P3 that appear at a certain reception timing difference u between the first and second received signals B1, B2 as a plurality of pulses P1-P3 contained in a radar signal A1 transmitted from a target radar 1, which is one of a plurality of secondary radars 1, 2. As an example of a condition for the search target extraction step S52, the difference in distance d to the radar 1 between the first and second receiving devices 11, 12 can be within approximately 200 km, and the certain reception timing difference u can be within a search range of approximately -668 μsec to +668 μsec. As another example of a condition for the search target extraction step S52, the difference in distance d to the radar 1 between the first and second receiving devices 11, 12 can be within approximately 70 km, and the certain reception timing difference u can be within a search range of approximately -234 μsec to +234 μsec. However, the distance difference and search range are not limited to these.

[0093] More specifically, the search target extraction step S42 can be performed as follows: First, one or more pulses in the first received signal B1 that are shifted within the search range for each of the multiple pulses in the second received signal B2 are selected, and the reception timing differences of the selected one or more pulses are calculated and recorded. From the calculated and recorded multiple reception timing differences, multiple identical reception timing differences u are extracted. Multiple pulses P1 to P3 in the first received signal B1 that respectively correspond to the multiple identical reception timing differences u are extracted as multiple target pulses P1 to P3.

[0094] The interception method includes a representative pulse extraction step S43 of extracting a representative pulse group G11, which is one of a plurality of pulse groups G1, from a plurality of target pulses P1-P3 in each of the received signals B1 and B2 within an antenna rotation period h (shown in FIG. 3(a)) required for one rotation of the interrogation antenna 1a. The representative pulse groups G11 of the first and second received signals B1 and B2 have common characteristics that indicate their identity.

[0095] The common feature can be the first and third pulses P1, P3 in the main lobe direction, which are a combination of two pulses P1, P3 that exhibit the largest amplitude within the antenna rotation period h. Alternatively, the common feature can be the amplitudes of the first to third pulses P1-P3 that are common to each other, and the first and second intervals t1, t2. The representative pulse extraction step S43 is similar to the representative pulse extraction step S32 of the third embodiment, except that a representative pulse group G11 is extracted from the plurality of target pulses P1-P3 of each received signal B1, B2.

[0096] Here, if the antenna rotation period h of the interrogation antenna 1a of the target radar 1 is known, this known value can be used as the antenna rotation period h. However, if the antenna rotation period h is unknown, the interception method may include a step of calculating the antenna rotation period h based on the interval between adjacent representative pulse groups G11 transmitted from the target radar 1 in the first or second received signal B1, B2 (period calculation step).

[0097] For example, in this period calculation step, it is possible to search for adjacent representative pulse groups G11 and identify the antenna rotation period h based on whether the antenna rotation period h is 4 or 10 seconds. Note that if an interception method according to a sixth embodiment, which will be described later, includes such a period calculation step, it is possible to calculate the antenna rotation period h from any of the first to third received signals B1 to B3.

[0098] The interception method includes a step (representative timing difference calculation step) S44 of calculating a representative timing difference r between representative pulse groups G11 of the first and second received signals B1, B2, similar to the representative timing difference calculation step S33 of the third embodiment. The interception method includes a step (reception timing difference calculation step) S45 of calculating the reception timing difference u, similar to the representative timing difference calculation step S33 of the third embodiment. The interception method includes a step (location determination step) S46 of determining the location of the target radar 1 based on the antenna rotation period h, the representative timing difference r, the reception timing difference u, and the locations of the first and second receiving devices 11, 12, similar to the location determination step S36 of the third embodiment.

[0099] In the above, radar 1 of the multiple radars 1 and 2 is set as target radar 1, and the position of this target radar 1 is identified. In addition, in the interception method according to this embodiment, radars other than radar 1 of the multiple radars 1 and 2 can be set as target radar 2, and the position of this target radar can be identified.

[0100] For example, it is possible to set another radar 2 out of the multiple radars 1 and 2 as the target radar and identify the position of this target radar 2. Then, by identifying the position of the target radar while switching the target radar to one of the multiple radars, it is possible to identify the positions of all of the multiple radars. Such identification of the positions of multiple radars can be similarly performed in the interception method according to the sixth embodiment, which will be described later.

[0101] "Secondary radar interception program, recording medium, and interception system" 6 and 9, an interception program and a recording medium for the secondary radars 1 and 2 according to this embodiment will be described. Furthermore, an interception system configured as hardware including the interception program and the recording medium according to this embodiment will be described. The interception program according to this embodiment is used to intercept multiple radar signals A1 and A2 transmitted from multiple radars 1 and 2, respectively.

[0102] Such an interception program is configured to cause the computer 20 to execute each of the steps S41 to S46 of the interception method according to this embodiment. That is, the interception program can cause the computer 20 to execute at least the signal acquisition step S41, the search target extraction step S42, the representative pulse extraction step S43, the representative timing difference calculation step S44, the reception timing difference calculation step S45, and the position identification step S46. Furthermore, the recording medium according to this embodiment is a computer-readable recording medium having such an interception program recorded thereon.

[0103] Although not shown in the figures, in the interception system according to this embodiment, the computer 20 has a signal acquisition unit, a search target extraction unit, a representative pulse extraction unit, a representative timing difference calculation unit, a reception timing difference calculation unit, and a position identification unit configured to respectively execute the signal acquisition step S41, the search target extraction step S42, the representative pulse extraction step S43, the representative timing difference calculation step S44, the reception timing difference calculation step S45, and the position identification step S46, instead of the signal acquisition unit, the representative pulse extraction unit, the representative timing difference calculation unit, the adjacent pulse extraction unit, the reception timing difference calculation unit, and the position identification unit of the third embodiment. Except for the configuration of the computer 20, the interception system according to this embodiment is similar to the interception system according to the third embodiment.

[0104] As described above, the method for intercepting the secondary radars 1 and 2 according to this embodiment includes a step (signal acquisition step) S41 of acquiring first and second received signals B1 and B2, which are peripheral signals including a plurality of radar signals A1 and A2 received by the first and second receiving devices 11 and 12, respectively; a step (search target extraction step) S42 of extracting, from each received signal B1 and B2, a plurality of target pulses P1 to P3 that appear with a certain reception timing difference u between the first and second received signals B1 and B2 as a plurality of pulses P1 to P3 included in the radar signal A1 transmitted from the target radar 1, which is one of the plurality of secondary radars 1 and 2; and a step (search target extraction step) S42 of extracting, from the plurality of target pulses P1 to P3 in each received signal B1 and B2, a search target pulse P1 to P3 that appears with a certain reception timing difference u between the first and second received signals B1 and B2 as a result of one rotation of the interrogation antenna 1a of the target radar 1. The method includes a step (representative pulse extraction step) S43 of extracting a representative pulse group G11, which is one of the plurality of pulse groups G1, within an antenna rotation period h between the first and second reception signals B1 and B2, wherein the representative pulse groups G11 of the first and second reception signals B1 and B2 have a common characteristic such that they are identical to each other; a step (representative timing difference calculation step) S44 of calculating a representative timing difference r between the representative pulse groups G11 of the first and second reception signals B1 and B2; a step (reception timing difference calculation step) S45 of calculating a reception timing difference u; and a step (position determination step) S46 of identifying the position of the target radar 1 based on the antenna rotation period h, the representative timing difference r, the reception timing difference u, and the positions of the first and second reception devices 11 and 12.

[0105] According to this interception method, even when the positions of the multiple radars 1 and 2 are unknown, the position of the target radar 1 can be efficiently identified based on the representative timing difference r and the reception timing difference u, which can be easily calculated based on the multiple target pulses P1 to P3 as described above, and the known positions of the first and second receiving devices 11 and 12. In particular, regardless of the difference in transmission timing between the multiple pulse groups G1 included in the radar signals A1 and A2 transmitted from the target radar 1, the representative timing difference r and the reception timing difference u can be easily calculated based on the representative pulse group G11 extracted from the multiple target pulses P1 to P3 that appear with a constant reception timing difference u between the first and second received signals B1 and B2. Therefore, even in the case of a staggered method, particularly a random staggered method, the position of the target radar 1 can be efficiently identified as described above. Therefore, information such as the positions of the secondary radars 1 and 2 can be efficiently identified. Furthermore, even in the case of a staggered method, particularly a random staggered method, information about the secondary radars 1 and 2 can be efficiently identified.

[0106] In the interception method for the secondary radars 1 and 2 according to this embodiment, the common feature can be the first and third pulses P1 and P3 in the main lobe direction, which are a combination of two pulses P1 and P3 that exhibit the largest amplitude within the antenna rotation period h. This interception method can efficiently extract the representative pulse group G11 based on prominent features such as the maximum amplitude.

[0107] Alternatively, in the interception method for the secondary radars 1 and 2 according to this embodiment, the common feature can be that the first to third pulses P1 to P3 have common amplitudes and common first and second intervals t1 and t2. According to this interception method, it is possible to efficiently extract representative pulse groups G11 as needed in any period within the antenna rotation period h.

[0108] Furthermore, the interception program for the secondary radars 1 and 2 according to this embodiment can provide the same effects as the interception method according to this embodiment. The recording medium according to this embodiment can provide the same effects as the interception method and interception program according to this embodiment.

[0109] "Fifth embodiment" A secondary radar interception method, an interception program, and a recording medium according to the fifth embodiment will be described.

[0110] "Secondary Radar Intercept Method" 3(a) and 10 to 12, the interception method of the secondary radar 1 according to this embodiment is as follows: The interception method according to this embodiment is used to intercept the radar signal A1 transmitted from the secondary radar 1, similar to the interception method according to the third embodiment.

[0111] 10 to 12, the interception method includes a step (signal acquisition step) S51 of acquiring first, second, and third received signals B1, B2, and B3, which are peripheral signals including a radar signal A1 received by first, second, and third receiving devices 11, 12, and 13, respectively. In Fig. 12, the solid line B1 indicates the first received signal B1, the solid line B2 indicates the second received signal B2, and the solid line B3 indicates the third received signal B3.

[0112] 11 and 12, the interception method includes a representative pulse extraction step S52 of extracting a representative pulse group G11, which is one of the plurality of pulse groups G1, from each of the received signals B1 to B3 within an antenna rotation period h (shown in FIG. 3(a)) required for one rotation of the interrogation antenna 1a. The representative pulse groups G11 of the first to third received signals B1 to B3 have common characteristics that indicate their identity. Note that the representative pulse extraction step S52 is similar to the representative pulse extraction step S32 of the third embodiment, except that it is performed on the third received signal B3 in addition to the first and second received signals B1 and B2.

[0113] Such common feature can be the first and third pulses P1, P3 in the main lobe direction, which are a combination of two pulses P1, P3 that exhibit the largest amplitude within the antenna rotation period h. Alternatively, the common feature can be the amplitudes of the first to third pulses P1 to P3 that are common to each other, and the first and second intervals t1, t2.

[0114] The interception method includes a step (representative timing difference calculation step) S53 of calculating a first representative timing difference r1 between the representative pulse groups G11 of the first and second received signals B1, B2 and a second representative timing difference r2 between the representative pulse groups G11 of the first and third received signals B1, B3. The first representative timing difference r1 may be the timing difference r1 between the first, second, or third pulses P1-P3 in the representative pulse groups G11 of the first and second received signals B1, B2. The second representative timing difference r2 may be the timing difference r2 between the first, second, or third pulses P1-P3 in the representative pulse groups G11 of the first and third received signals B1, B3.

[0115] Furthermore, the first representative timing difference r1 is set to a negative value when the representative pulse group G11 of the first received signal B1 appears after the representative pulse group G11 of the second received signal B2, and is set to a positive value when the representative pulse group G11 of the first received signal B1 appears before the representative pulse group G11 of the second received signal B2.

[0116] The second representative timing difference r2 is negative if the representative pulse group G11 of the first received signal B1 appears after the representative pulse group G11 of the third received signal B3, and is positive if the representative pulse group G11 of the first received signal B1 appears before the representative pulse group G11 of the third received signal B3.

[0117] The interception method includes a step (position determination step) S54 of determining the position of the radar 1 based on the antenna rotation period h, the first and second representative timing differences r1, r2, and the positions of the first to third receiving devices 11 to 13. Specifically, such position determination step S54 can be performed as follows.

[0118] 3(a) and 12, the antenna rotation period h is typically 4 or 10 seconds, and in many cases, the antenna rotation period h is known. In this case, this known value can be used as the antenna rotation period h. However, if the antenna rotation period h is unknown, the interception method can include a step (period calculation step) of calculating the antenna rotation period h based on the interval between adjacent representative pulse groups G11 transmitted from the radar 1 in any of the first to third received signals B1 to B3. In this period calculation step, based on the fact that the antenna rotation period h is 4 or 10 seconds, adjacent representative pulse groups G11 can be searched for and the antenna rotation period h can be identified.

[0119] 10 and 12, the rotation direction of the interrogation antenna 1a is typically clockwise in a planar view. In light of this, if the first representative timing difference r1 is a negative value, it can be determined that the radar 1 is located on the left side when viewed from the first receiving device 11 to the second receiving device 12 in a planar view. If the first representative timing difference r1 is a positive value, it can be determined that the radar 1 is located on the right side when viewed from the first receiving device 11 to the second receiving device 12 in a planar view. However, if the rotation direction of the interrogation antenna 1a is unknown, it is advisable to roughly estimate in advance whether the radar 1 is located on the left or right side when viewed from the first receiving device 11 to the second receiving device 12 in a planar view.

[0120] 10 and 12, when the second representative timing difference r2 is a negative value, it can be determined that the radar 1 is located on the left side when viewed from the first receiving device 11 to the third receiving device 13 in a planar view. When the second representative timing difference r2 is a positive value, it can be determined that the radar 1 is located on the right side when viewed from the first receiving device 11 to the third receiving device 13 in a planar view. However, when the rotation direction of the interrogation antenna 1a is unknown, it is advisable to roughly estimate in advance whether the radar 1 is located on the left or right side when viewed from the first receiving device 11 to the third receiving device 13 in a planar view.

[0121] Based on the antenna rotation period h and the first representative timing difference r1, the first angular difference θ1 (degrees) between the first and second receiving devices 11, 12 centered on the position of the radar 1 is calculated using the following (Equation 3). Note that the first distance difference d1 to the radar 1 between the first and second receiving devices 11, 12 has a small effect on the first angular difference θ1 compared to the first representative timing difference r1, so it is treated as 0 (m) in the calculation of the first angular difference θ1.

[0122] θ1 = r1 / h×360 (degrees) (Formula 3)

[0123] Based on the antenna rotation period h and the second representative timing difference r2, the second angular difference θ2 (degrees) between the first and third receiving devices 11, 13 centered on the position of the radar 1 is calculated using the following (Equation 4). Note that the second distance difference d2 to the radar 1 between the first and third receiving devices 11, 13 also has a small effect on the second angular difference θ2 compared to the second representative timing difference r2, so it is treated as 0 (m) in the calculation of the second angular difference θ2.

[0124] θ2 = r2 / h×360 (degrees) (Formula 4)

[0125] Furthermore, a first distance e1 (m) between the first and second receiving devices 11 and 12 is calculated based on the positions of the first and second receiving devices 11 and 12. A second distance e2 (m) between the first and third receiving devices 11 and 13 is calculated based on the positions of the first and third receiving devices 11 and 13. Then, a position that satisfies the condition that the first angular difference θ1 between the first and second receiving devices 11 and 12, the second angular difference θ2 between the first and third receiving devices 11 and 13, the first distance e1 between the first and second receiving devices 11 and 12, and the second distance e2 between the first and third receiving devices 11 and 13 are all predetermined values ​​in a planar view can be determined as the position of the radar 1.

[0126] In addition, in the position determination process S54, the intersection of an arc-shaped trajectory drawn so as to satisfy the first angular difference θ1 based on the positions of the first and second receiving devices 11, 12 in a planar view and an arc-shaped trajectory drawn so as to satisfy the second angular difference θ2 based on the positions of the first and third receiving devices 11, 13 can also be determined as the position of the radar 1.

[0127] "Secondary radar interception program, recording medium, and interception system" 6 and 10, an interception program and a recording medium for the secondary radar 1 according to this embodiment will be described. Furthermore, an interception system configured as hardware including the interception program and the recording medium according to this embodiment will be described. The interception program according to this embodiment is used to intercept radar signal A1 transmitted from radar 1.

[0128] Such an interception program is configured to cause the computer 20 to execute each of steps S41 to S44 of the interception method according to this embodiment. That is, the interception program causes the computer 20 to execute at least a signal acquisition step S51, a representative pulse extraction step S52, a representative timing difference calculation step S53, and a position identification step S54. Furthermore, the recording medium according to this embodiment is a computer-readable recording medium having such an interception program recorded thereon.

[0129] Although not shown, in the interception system according to this embodiment, the computer 20 has a signal acquisition unit, a representative pulse extraction unit, a representative timing difference calculation unit, an adjacent pulse extraction unit, a reception timing difference calculation unit, and a location determination unit configured to respectively execute the signal acquisition step S51, the representative pulse extraction step S52, the representative timing difference calculation step S53, and the location determination step S54, instead of the signal acquisition unit, the representative pulse extraction unit, the representative timing difference calculation unit, the adjacent pulse extraction unit, the reception timing difference calculation unit, and the location determination unit of the third embodiment. As shown in FIG. 10 , the interception system according to this embodiment further includes a third receiving device 13, which is connected to the communication network 30. This interception system is similar to the interception system according to the third embodiment, except for the configuration of the computer 20, the third receiving device 13, and the associated configuration.

[0130] As described above, the method for intercepting the secondary radar 1 according to this embodiment includes a step (signal acquisition step) S51 of acquiring the first, second, and third received signals B1, B2, and B3, which are peripheral signals including the radar signal A1, received by the first, second, and third receiving devices 11, 12, and 13, respectively, and a step (representative pulse extraction step) S52 of extracting a representative pulse group G11, which is one of the plurality of pulse groups G1, from the plurality of pulses of each received signal B1 to B3 within the antenna rotation period h during one rotation of the interrogation antenna 1a. The method includes a step S52 of determining whether the pulse groups G11 have common characteristics to indicate their identity; a step S53 of calculating a first representative timing difference r1 between the representative pulse groups G11 of the first and second received signals B1, B2 and a second representative timing difference r2 between the representative pulse groups G11 of the first and third received signals B1, B3 (representative timing difference calculation step); and a step S54 of identifying the position of the secondary radar 1 based on the antenna rotation period h, the first and second representative timing differences r1, r2, and the positions of the first to third receiving devices 11 to 13 (position identification step).

[0131] According to this interception method, even if the position of one secondary radar 1 is unknown, the position of the secondary radar 1 can be efficiently identified based on the first and second representative timing differences r1, r2, which can be calculated by the simple process described above, and the known positions of the first to third receiving devices 11-13. In particular, regardless of the difference in transmission timing between the multiple pulse groups G1 of the radar signal A1, the first and second representative timing differences r1, r2 can be easily calculated using the representative pulse group G11 extracted from the multiple pulses of the first to third received signals B1-B3. Therefore, even in the case of a staggered method, particularly a random staggered method, the position of the secondary radar 1 can be efficiently identified as described above. Therefore, information such as the position of the secondary radar 1 can be efficiently identified, and further, even in the case of a staggered method, particularly a random staggered method, information about the secondary radar 1 can be efficiently identified.

[0132] In the interception method for the secondary radar 1 according to this embodiment, the common feature can be the first and third pulses P1 and P3 in the main lobe direction, which are a combination of two pulses P1 and P3 that exhibit the largest amplitude within the antenna rotation period h. This interception method can efficiently extract the representative pulse group G11 based on prominent features such as the maximum amplitude.

[0133] Alternatively, in the interception method for the secondary radar 1 according to this embodiment, the common feature can be that the first to third pulses P1 to P3 have common amplitudes and common first and second intervals t1 and t2. According to this interception method, it is possible to efficiently extract representative pulse groups G11 as needed in any period within the antenna rotation period h.

[0134] Furthermore, the interception program for the secondary radar 1 according to this embodiment can provide the same effects as the interception method according to this embodiment. The recording medium according to this embodiment can provide the same effects as the interception method and interception program according to this embodiment.

[0135] "Sixth embodiment" A secondary radar interception method, an interception program, and a recording medium according to the sixth embodiment will be described.

[0136] "Secondary Radar Intercept Method" 3(a) and (b), 10, 12, and 13, the interception method for secondary radars 1 and 2 according to this embodiment is as follows: Referring to Figures 3(a) and (b) and 10, the interception method according to this embodiment is used to intercept multiple radar signals A1 and A2 transmitted from multiple secondary radars 1 and 2, respectively.

[0137] Similar to the interception methods according to the fourth and fifth embodiments, the interception method according to this embodiment can be used to intercept a radar signal A1 transmitted from a secondary radar 1. Furthermore, similar to the interception method according to the fourth embodiment, the interception method according to this embodiment can be used to intercept another radar signal A2 transmitted from another secondary radar 2. Referring to Figures 12 and 13, the interception method includes a step (signal acquisition step) S61 of acquiring first, second, and third received signals B1, B2, and B3 received by first, second, and third receiving devices 11, 12, and 13, respectively, which are peripheral signals including these radar signals A1 and A2.

[0138] The interception method includes a step (search target extraction step) S62 of extracting, from each of the received signals B1 to B3, a plurality of target pulses P1 to P3 that appear at a constant first reception timing difference u1 between the first and second received signals B1, B2 and that appear at a constant second reception timing difference u2 between the first and third received signals B1, B3, as a plurality of pulses P1 to P3 contained in a radar signal A1 transmitted from a target radar 1 that is one of the plurality of secondary radars 1 and 2. Note that the search target extraction step S62 is similar to the search target extraction step S42 of the fourth embodiment, except that it is executed for the third received signal B3 in addition to the first and second received signals B1 and B2.

[0139] The interception method includes a representative pulse extraction step S63 of extracting a representative pulse group G11, which is one of the plurality of pulse groups G1, from the plurality of target pulses P1 to P3 of each of the received signals B1 to B3 within an antenna rotation period h (shown in FIG. 3(a)) required for one rotation of the interrogation antenna 1a. These representative pulse groups G11 of the first to third received signals B1 to B3 have common characteristics that indicate their identity.

[0140] The common feature can be a combination of first and third pulses P1, P3 in the main lobe direction, which are the two pulses P1, P3 that exhibit the largest amplitude within the antenna rotation period h. Alternatively, the common feature can be a combination of first to third pulses P1-P3 and first and second intervals t1, t2 that are common to each other. Note that the representative pulse extraction step S63 is similar to the representative pulse extraction step S53 of the fifth embodiment, except that it is performed on the third received signal B3 in addition to the first and second received signals B1, B2.

[0141] The interception method includes a step (representative timing difference calculation step) S64 of calculating a first representative timing difference r1 between the representative pulse groups G11 of the first and second received signals B1, B2 and a second representative timing difference r2 between the representative pulse groups G11 of the first and third received signals B1, B3, similar to the representative timing difference calculation step S53 of the fifth embodiment. The interception method includes a step (location determination step) S65 of determining the location of the target radar 1 based on the antenna rotation period h, the first and second representative timing differences r1, r2, and the locations of the first to third receiving devices 11-13, similar to the location determination step S54 of the fifth embodiment.

[0142] "Secondary radar interception program, recording medium, and interception system" 6 and 13, an interception program and a recording medium for the secondary radars 1 and 2 according to this embodiment will be described. Furthermore, an interception system configured as hardware including the interception program and the recording medium according to this embodiment will be described. The interception program according to this embodiment is used to intercept multiple radar signals A1 and A2 transmitted from multiple radars 1 and 2, respectively.

[0143] Such an interception program is configured to cause the computer 20 to execute each step of the interception method according to this embodiment. That is, the interception program can cause the computer 20 to execute at least a signal acquisition step S61, a search target extraction step S62, a representative pulse extraction step S63, a representative timing difference calculation step S64, and a position identification step S65. Furthermore, the recording medium according to this embodiment is a computer-readable recording medium having such an interception program recorded thereon.

[0144] Although not particularly shown, in the interception system according to this embodiment, the computer 20 has a signal acquisition unit, a search target extraction unit, a representative pulse extraction unit, a representative timing difference calculation unit, and a position identification unit configured to respectively execute the signal acquisition step S61, the search target extraction step S62, the representative pulse extraction step S63, the representative timing difference calculation step S64, and the position identification step S65, instead of the signal acquisition unit, the representative pulse extraction unit, the representative timing difference calculation unit, and the position identification unit of the fifth embodiment. Except for the configuration of the computer 20, the interception system according to this embodiment is similar to the interception system according to the fifth embodiment.

[0145] As described above, the method for intercepting the secondary radars 1 and 2 according to this embodiment includes a step (signal acquisition step) S61 of acquiring first, second, and third received signals B1, B2, and B3, which are peripheral signals including radar signals A1 and A2 from the plurality of secondary radars 1 and 2, received by the first, second, and third receiving devices 11, 12, and 13, respectively; a step (search target extraction step) S62 of extracting, from each of the received signals B1 to B3, a plurality of target pulses P1 to P3 that appear at a fixed first reception timing difference u1 between the first and second received signals B1 and B2 and that appear at a fixed second reception timing difference u2 between the first and third received signals B1 and B3, as a plurality of pulses P1 to P3 included in the radar signal A1 transmitted from the target radar 1, which is one of the plurality of secondary radars 1 and 2; and a step (search target extraction step) S62 of extracting a plurality of target pulses P1 to P3 from each of the received signals B1 to B3. The method includes a step (representative pulse extraction step) S63 of extracting a representative pulse group G11, which is one of the plurality of pulse groups G1, from P1 to P3 within an antenna rotation period h during which the interrogation antenna 1a of the target radar 1 makes one rotation, wherein the representative pulse groups G11 of the first to third reception signals B1 to B3 have common characteristics so as to indicate their identity; a step (representative timing difference calculation step) S64 of calculating a first representative timing difference r1 between the representative pulse groups G11 of the first and second reception signals B1, B2 and a second representative timing difference r2 between the representative pulse groups G11 of the first and third reception signals B1, B3; and a step (position identification step) S65 of identifying the position of the target radar 1 based on the antenna rotation period h, the first and second representative timing differences r1, r2, and the positions of the first to third receiving devices 11 to 13.

[0146] According to this interception method, even when the positions of the multiple secondary radars 1 and 2 are unknown, the position of the target radar 1 can be efficiently identified based on the first and second representative timing differences r1 and r2, which can be easily calculated based on the multiple target pulses P1 to P3 described above, and the known positions of the first to third receiving devices 11 to 13. In particular, regardless of the difference in transmission timing between the multiple pulse groups G1 included in the radar signal A1 transmitted from the target radar 1, the first and second representative timing differences r1 and r2 can be easily identified based on the representative pulse group G11 extracted from the multiple target pulses P1 to P3, which appear as a constant first or second reception timing difference u1 or u2 between the first to third received signals B1 to B3. Therefore, even in the case of a staggered system, particularly a random staggered system, the position of the target radar 1 can be efficiently identified as described above. Therefore, information such as the positions of the secondary radars 1 and 2 can be efficiently identified. Furthermore, even in the case of a staggered system, particularly a random staggered system, information about the secondary radars 1 and 2 can be efficiently identified.

[0147] In the interception method for the secondary radars 1 and 2 according to this embodiment, the common feature can be the first and third pulses P1 and P3 in the main lobe direction, which are a combination of two pulses P1 and P3 that exhibit the largest amplitude within the antenna rotation period h. This interception method can efficiently extract the representative pulse group G11 based on prominent features such as the maximum amplitude.

[0148] Alternatively, in the interception method for the secondary radars 1 and 2 according to this embodiment, the common feature can be that the first to third pulses P1 to P3 have common amplitudes and common first and second intervals t1 and t2. According to this interception method, it is possible to efficiently extract representative pulse groups G11 as needed in any period within the antenna rotation period h.

[0149] Furthermore, the interception program for the secondary radars 1 and 2 according to this embodiment can provide the same effects as the interception method according to this embodiment. The recording medium according to this embodiment can provide the same effects as the interception method and interception program according to this embodiment.

[0150] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and the present invention can be modified and changed based on the technical concept thereof.

[0151] Embodiments 1 to 10 of the present invention are as follows. [Embodiment 1] A method for intercepting a radar signal transmitted from a secondary radar, the method comprising: a directional interrogation antenna that transmits an interrogation signal while rotating; and an omnidirectional SLS antenna that transmits an SLS signal; the radar signal includes a plurality of pulse groups each consisting of a combination of a first and a third pulse of the interrogation signal and a second pulse of the SLS signal; and in each pulse group, the second pulse is transmitted at a predetermined first interval from the transmission of the first pulse, and the third pulse is transmitted at a predetermined second interval from the transmission of the first pulse. acquiring first and second received signals, which are peripheral signals including the radar signal, received by first and second receiving devices, respectively; correcting at least one of the first and second received signals in accordance with a difference in distance to the secondary radar between the first and second receiving devices so as to match the timings of the first and second received signals based on a transmission timing of the radar signal; after the correction, identifying, from the first received signal, a plurality of pulses that appear at the same timing as a plurality of pulses of the second received signal as the first to third pulses; Secondary radar interception methods, including: [Embodiment 2] A method for intercepting a radar signal transmitted from a secondary radar, the method comprising: a directional interrogation antenna that transmits an interrogation signal while rotating; and an omnidirectional SLS antenna that transmits an SLS signal; the radar signal includes a plurality of pulse groups each consisting of a combination of a first and a third pulse of the interrogation signal and a second pulse of the SLS signal; and in each pulse group, the second pulse is transmitted at a predetermined first interval from the transmission of the first pulse, and the third pulse is transmitted at a predetermined second interval from the transmission of the first pulse. acquiring first and second received signals, which are peripheral signals including the radar signal, received by first and second receiving devices, respectively; identifying, from the first received signal, a plurality of pulses that appear at a certain reception timing difference with respect to the plurality of pulses of the second received signal as the first to third pulses; Secondary radar interception methods, including: [Embodiment 3] A method for intercepting a radar signal transmitted from a secondary radar, the method comprising: a directional interrogation antenna that transmits an interrogation signal while rotating; and an omnidirectional SLS antenna that transmits an SLS signal; the radar signal includes a plurality of pulse groups each consisting of a combination of a first and a third pulse of the interrogation signal and a second pulse of the SLS signal; and in each pulse group, the second pulse is transmitted at a predetermined first interval from the transmission of the first pulse, and the third pulse is transmitted at a predetermined second interval from the transmission of the first pulse. acquiring first and second received signals, which are peripheral signals including the radar signal, received by first and second receiving devices, respectively; extracting a representative pulse group, which is one of the plurality of pulse groups, from the plurality of pulses of each received signal within an antenna rotation period during one rotation of the interrogation antenna, wherein the representative pulse groups of the first and second received signals have a common characteristic that indicates their identity; calculating a representative timing difference between representative pulse groups of the first and second received signals; extracting, from the second received signal, a pulse group that appears at a timing closest to a representative pulse group of the first received signal, as an adjacent pulse group; calculating a reception timing difference between the representative and adjacent pulse groups; determining a position of the secondary radar based on the antenna rotation period, the representative timing difference, the reception timing difference, and the positions of the first and second receiving devices; Secondary radar interception methods, including: [Embodiment 4] A secondary radar interception method for intercepting a plurality of radar signals respectively transmitted from a plurality of secondary radars, wherein each secondary radar has a directional interrogation antenna that transmits an interrogation signal while rotating, and an omnidirectional SLS antenna that transmits an SLS signal, each radar signal includes a plurality of pulse groups each consisting of a combination of a first and a third pulse of the interrogation signal and a second pulse of the SLS signal, and in each pulse group, the second pulse is transmitted at a predetermined first interval from the transmission of the first pulse, and the third pulse is transmitted at a predetermined second interval from the transmission of the first pulse, acquiring first and second received signals, which are peripheral signals including the plurality of radar signals received by first and second receiving devices, respectively; extracting, from each received signal, a plurality of target pulses that appear with a certain reception timing difference between the first and second received signals as a plurality of pulses contained in a radar signal transmitted from a target radar that is any one of the plurality of secondary radars; extracting a representative pulse group, which is one of the plurality of pulse groups, from a plurality of target pulses of each received signal within an antenna rotation period during which an interrogation antenna of the target radar makes one rotation, wherein the representative pulse groups of the first and second received signals have a common characteristic to indicate their identity; calculating a representative timing difference between representative pulse groups of the first and second received signals; calculating the reception timing difference; determining a position of the target radar based on the antenna rotation period, the representative timing difference, the reception timing difference, and the positions of the first and second receiving devices; Secondary radar interception methods, including: [Embodiment 5] A method for intercepting a radar signal transmitted from a secondary radar, the method comprising: a directional interrogation antenna that transmits an interrogation signal while rotating; and an omnidirectional SLS antenna that transmits an SLS signal; the radar signal includes a plurality of pulse groups each consisting of a combination of a first and a third pulse of the interrogation signal and a second pulse of the SLS signal; and in each pulse group, the second pulse is transmitted at a predetermined first interval from the transmission of the first pulse, and the third pulse is transmitted at a predetermined second interval from the transmission of the first pulse. acquiring first, second, and third received signals, which are peripheral signals including the radar signal received by first, second, and third receiving devices, respectively; extracting a representative pulse group, which is one of the plurality of pulse groups, from the plurality of pulses of each received signal within an antenna rotation period during which the interrogation antenna makes one rotation, wherein the representative pulse groups of the first to third received signals have a common characteristic that indicates their identity; calculating a first representative timing difference between the representative pulse groups of the first and second received signals and a second representative timing difference between the representative pulse groups of the first and third received signals; determining the position of the secondary radar based on the antenna rotation period, the first and second representative timing differences, and the positions of the first to third receiving devices; Secondary radar interception methods, including: [Embodiment 6] A secondary radar interception method for intercepting a plurality of radar signals respectively transmitted from a plurality of secondary radars, wherein each secondary radar has a directional interrogation antenna that transmits an interrogation signal while rotating, and an omnidirectional SLS antenna that transmits an SLS signal, each radar signal includes a plurality of pulse groups each consisting of a combination of a first and a third pulse of the interrogation signal and a second pulse of the SLS signal, and in each pulse group, the second pulse is transmitted at a predetermined first interval from the transmission of the first pulse, and the third pulse is transmitted at a predetermined second interval from the transmission of the first pulse, acquiring first, second, and third received signals, which are peripheral signals including radar signals from the plurality of secondary radars received by first, second, and third receiving devices, respectively; extracting, from each received signal, a plurality of target pulses that appear at a first predetermined reception timing difference between the first and second received signals and that appear at a second predetermined reception timing difference between the first and third received signals as a plurality of pulses included in a radar signal transmitted from a target radar that is any one of the plurality of secondary radars; a step of extracting a representative pulse group, which is one of the plurality of pulse groups, from a plurality of target pulses of each received signal within an antenna rotation period during which an interrogation antenna of the target radar makes one rotation, wherein the representative pulse groups of the first to third received signals have a common characteristic to indicate their identity; calculating a first representative timing difference between the representative pulse groups of the first and second received signals and a second representative timing difference between the representative pulse groups of the first and third received signals; identifying the position of the target radar based on the antenna rotation period, the first and second representative timing differences, and the positions of the first to third receiving devices; Secondary radar interception methods, including: [Embodiment 7] A method for intercepting a secondary radar as described in any one of embodiments 3 to 6, wherein the common feature is that the first and third pulses are in the main lobe direction and are a combination of two pulses that exhibit the largest amplitude within the antenna rotation period. [Embodiment 8] A method for intercepting a secondary radar described in any one of embodiments 3 to 6, wherein the common feature is that the amplitudes of the first to third pulses and the first and second intervals are common to each other. [Embodiment 9] A secondary radar interception program that causes a computer to execute each step of the secondary radar interception method according to any one of the first to eighth embodiments. [Embodiment 10] A computer-readable recording medium having recorded thereon a secondary radar interception program as described in embodiment 9. [Explanation of symbols]

[0152] 1... Secondary radar, radar, target radar, 2... Secondary radar, another secondary radar, radar, another radar 1a, 2a...Question antenna, 1b, 2b...SLS antenna 11...first receiving device, 12...second receiving device, 13...third receiving device 20...Computers, arithmetic units A1...radar signal, A2...radar signal, another radar signal B1...first received signal, B2...second received signal, B3...third received signal G1...pulse group, G11...representative pulse group, G12...adjacent pulse group, P1...first pulse, P2...second pulse, P3...third pulse d...distance difference t1...first interval, t2...second interval h...antenna rotation period u...shift time, reception timing difference, u1...first reception timing difference, u2...second reception timing difference r...representative timing difference, r1...first representative timing difference, r2...second representative timing difference S11: signal acquisition step, S12: signal correction step, S13: pulse identification step S21: Signal Acquisition Step, S22: Pulse Identification Step S31: signal acquisition step, S32: representative pulse extraction step, S33: representative timing difference calculation step, S34: adjacent pulse extraction step, S35: reception timing difference calculation step, S36: position identification step S41: signal acquisition step, S42: search target extraction step, S43: representative pulse extraction step, S44: representative timing difference calculation step, S45: reception timing difference calculation step, S46: position identification step S51: signal acquisition step, S52: representative pulse extraction step, S53: representative timing difference calculation step, S54: position identification step S61: signal acquisition step, S62: search target extraction step, S63: representative pulse extraction step, S64: representative timing difference calculation step, S65: position identification step

Claims

1. A method for intercepting a radar signal transmitted from a secondary radar, wherein the secondary radar has a directional interrogation antenna that transmits an interrogation signal while rotating, and an omnidirectional SLS antenna that transmits an SLS signal, the radar signal includes a plurality of pulse groups each consisting of a combination of a first and a third pulse of the interrogation signal and a second pulse of the SLS signal, and in each pulse group, the second pulse is transmitted at a predetermined first interval from the transmission of the first pulse, and the third pulse is transmitted at a predetermined second interval from the transmission of the first pulse, acquiring first and second received signals, which are peripheral signals including the radar signal, received by first and second receiving devices, respectively; identifying, from the first received signal, a plurality of pulses that appear at a certain reception timing difference u with respect to the plurality of pulses of the second received signal as the first to third pulses; Secondary radar interception methods, including:

2. 2. The method for intercepting a secondary radar according to claim 1, wherein the reception timing difference u is a value u (= d / v) obtained by dividing a difference in distance d to the secondary radar between the first and second receiving devices by the speed of light v, which is the speed of radio waves.

3. A method for intercepting a radar signal transmitted from a secondary radar, wherein the secondary radar has a directional interrogation antenna that transmits an interrogation signal while rotating, and an omnidirectional SLS antenna that transmits an SLS signal, the radar signal includes a plurality of pulse groups each consisting of a combination of a first and a third pulse of the interrogation signal and a second pulse of the SLS signal, and in each pulse group, the second pulse is transmitted at a predetermined first interval from the transmission of the first pulse, and the third pulse is transmitted at a predetermined second interval from the transmission of the first pulse, acquiring first and second received signals, which are peripheral signals including the radar signal, received by first and second receiving devices, respectively; a step of calculating a relative shift time u (= d / v) of the first and second received signals based on a difference in distance d between the first and second receiving devices to the secondary radar and the speed of light v, which is the speed of radio waves, to make the timings of the first and second received signals coincide with each other based on the transmission timing of the radar signal, and performing a correction to relatively shift the first and second received signals by the shift time u; after the correction, identifying, from the first received signal, a plurality of pulses that appear at the same timing as a plurality of pulses of the second received signal as the first to third pulses; Secondary radar interception methods, including:

4. A secondary radar interception program that causes a computer to execute each step of the secondary radar interception method according to any one of claims 1 to 3.

5. A computer-readable recording medium having recorded thereon the secondary radar interception program according to claim 4.

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