Positioning device and positioning method

Abstract

A measuring device (3) comprises: a position candidate calculating unit (12) that, when a pulse signal is repeatedly emitted from a target, calculates one or more position candidates for the target using a first equation relating to a time difference between the reception time of each pulse signal by a first satellite (1-1) and the reception time of each pulse signal by a second satellite (1-2), and a second equation relating to a frequency difference between a Doppler frequency included in each first reception signal and a Doppler frequency included in each second reception signal; and a target position identifying unit (13) that, on the basis of a variation over time in the time difference and a variation over time in the frequency difference, selects the position candidate that indicates the true position of the target, from among the one or more position candidates calculated by the position candidate calculating unit (12).

Description

Positioning device and positioning method

[0001] The present disclosure relates to a positioning device and a positioning method.

[0002] There is a positioning device that calculates the position of a target based on received signals that indicate reflected waves of a signal reflected by the target at multiple times. For example, Non-Patent Document 1 discloses an example of such a positioning device, which, when a continuous wave is radiated toward a target, acquires a first received signal that is a received signal of the reflected wave from a first satellite that receives the continuous wave reflected by the target, acquires a second received signal that is a received signal of the reflected wave from a second satellite that receives the reflected wave, and calculates the position of the target from the first received signal and the second received signal.

[0003] “INTERFERENCE LOCALIZATION FOR EUTELSAT SATELLITES-THE FIRST EUROPEAN TRANSMITTER LOCATION SYSTEM”, INTERNATIONAL JOURNAL OF SATELLITE COMMUNICATIONS, VOL. 15, 155-183 (1997)

[0004] The positioning device disclosed in Non-Patent Document 1 can calculate the position of a target if the signal radiated toward the target is a continuous wave, but if the signal radiated toward the target is a pulsed signal, the position of the target is calculated to be the virtual image position resulting from the repetition of the pulse signal in addition to the true position of the target, which has the problem that the true position of the target cannot be identified.

[0005] The present disclosure has been made to solve the above-mentioned problems, and aims to provide a positioning device that can calculate the true position of a target even if the signal emitted toward the target is a pulse signal.

[0006] A positioning device according to the present disclosure includes a signal acquisition unit that, when pulse signals are repeatedly emitted from a target, acquires first received signals that are received signals of each pulse signal from a first satellite that has received each pulse signal, and acquires second received signals that are received signals of each pulse signal from a second satellite that has received each pulse signal. The positioning device also includes a position candidate calculation unit that calculates one or more position candidates of the target using a first equation relating to a time difference between the time at which each pulse signal is received by the first satellite and the time at which each pulse signal is received by the second satellite, and a second equation relating to a frequency difference between a Doppler frequency included in each first received signal and a Doppler frequency included in each second received signal, and a target position identification unit that selects a position candidate that indicates a true position of the target from the one or more position candidates calculated by the position candidate calculation unit, based on either a change in the time difference over time or a change in the frequency difference over time.

[0007] According to the present disclosure, even if the signal emitted toward the target is a pulse signal, the true position of the target can be calculated.

[0008] 1 is a configuration diagram showing a positioning system including a positioning device 3 according to a first embodiment. FIG. 2 is a hardware configuration diagram showing the hardware of the positioning device 3 according to the first embodiment. FIG. 3 is a hardware configuration diagram of a computer when the positioning device 3 is realized by software, firmware, or the like. FIG. 4 is a flowchart showing a positioning method, which is a processing procedure of the positioning device 3. FIG. 5 is an explanatory diagram showing the relationship between the position u of a target and the respective positions of a first satellite 1-1 and a second satellite 1-2. FIG. 6 is an explanatory diagram showing position candidates calculated by a position candidate calculation unit 12. FIG. 7 is an explanatory diagram showing the true position and the position of a virtual image of a target. FIG. 8 is an explanatory diagram showing how multiple peaks appear on a map of TDOA and FDOA as a pulse signal is repeated. FIG. 9 is an explanatory diagram showing the reception times t of each pulse signal by the first satellite 1-1. ａ and the reception time t of each pulse signal by the second satellite 1-2. ｂ 1 is an explanatory diagram showing the relationship between the time difference τ between the first received signal p and the target and the TDOA of one or more position candidates of the target. １(t ａ ) and the Doppler frequency contained in the second received signal p ２ (t ｂ 1 is an explanatory diagram showing a relationship between a time change in frequency difference Δf with a Doppler frequency included in a frequency domain (F) and a time change in FDOA for one or more position candidates of a target. FIG. 2 is a configuration diagram showing a positioning system including a positioning device 3 according to a second embodiment. FIG. 3 is a hardware configuration diagram showing hardware of a positioning device 3 according to a second embodiment. FIG. 4 is a hardware configuration diagram showing hardware of a positioning device 3 according to a third embodiment. FIG. 5 is a hardware configuration diagram showing hardware of a positioning device 3 according to a third embodiment.

[0009] In order to explain the present disclosure in more detail, embodiments of the present disclosure will be described below with reference to the accompanying drawings.

[0010] Embodiment 1. Fig. 1 is a configuration diagram showing a positioning system including a positioning device 3 according to embodiment 1. Fig. 2 is a hardware configuration diagram showing the hardware of the positioning device 3 according to embodiment 1. The positioning system shown in Fig. 1 includes a first satellite 1-1, a second satellite 1-2, an antenna 2-1, an antenna 2-2, and a positioning device 3. The target shown in Fig. 1 is a radio wave source, and repeatedly radiates a pulse signal.

[0011] When pulse signals are repeatedly emitted from the target, the first satellite 1-1 receives each pulse signal. The first satellite 1-1 transmits a first received signal, which is a received signal of each pulse signal, to the antenna 2-1. When pulse signals are repeatedly emitted from the target, the second satellite 1-2 receives each pulse signal. The second satellite 1-2 transmits a second received signal, which is a received signal of each pulse signal, to the antenna 2-2.

[0012] The antenna 2-1 receives a first received signal transmitted from the first satellite 1-1 and transmits the first received signal to the positioning device 3. The antenna 2-2 receives a second received signal transmitted from the second satellite 1-2 and transmits the second received signal to the positioning device 3. The positioning device 3 includes a signal acquisition unit 11, a position candidate calculation unit 12, and a target position identification unit 13.

[0013] The signal acquirer 11 is realized by, for example, the signal acquirer circuit 21 shown in FIG. 2 . The signal acquirer 11 acquires first received signals, which are received signals of the respective pulse signals, from the first satellite 1-1 via the antenna 2-1. The signal acquirer 11 acquires second received signals, which are received signals of the respective pulse signals, from the second satellite 1-2 via the antenna 2-2. The signal acquirer 11 outputs the respective first received signals and the respective second received signals to the position candidate calculator 12 and the target position identifier 13, respectively.

[0014] The position candidate calculation unit 12 is realized by, for example, the position candidate calculation circuit 22 shown in FIG. 2 . The position candidate calculation unit 12 acquires each of the first received signals and each of the second received signals from the signal acquisition unit 11. The position candidate calculation unit 12 calculates one or more position candidates for the target using a first equation and a second equation. The first equation is an equation relating to the time difference between the reception time of each pulse signal by the first satellite 1-1 and the reception time of each pulse signal by the second satellite 1-2. The second equation is an equation relating to the frequency difference between the Doppler frequency included in each of the first received signals and the Doppler frequency included in each of the second received signals. The position candidate calculation unit 12 outputs information indicating one or more position candidates for the target to the target position identification unit 13.

[0015] The target position identifying unit 13 is realized by, for example, the target position identifying circuit 23 shown in FIG. 2 . The target position identifying unit 13 acquires each of the first received signals and each of the second received signals from the signal acquiring unit 11. The target position identifying unit 13 acquires information indicating one or more position candidates of the target from the position candidate calculating unit 12. The target position identifying unit 13 selects a position candidate indicating the true position of the target from the one or more position candidates of the target based on the time change in the time difference and the time change in the frequency difference. The position candidate indicating the true position of the target selected by the target position identifying unit 13 is displayed as the true position of the target on, for example, a display device (not shown).

[0016] 1, it is assumed that each of the signal acquisition unit 11, the position candidate calculation unit 12, and the target position identification unit 13, which are components of the positioning device 3, is realized by dedicated hardware as shown in Fig. 2. That is, it is assumed that the positioning device 3 is realized by a signal acquisition circuit 21, a position candidate calculation circuit 22, and a target position identification circuit 23. Each of the signal acquisition circuit 21, the position candidate calculation circuit 22, and the target position identification circuit 23 corresponds to, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC (Application Specific Integrated Circuit), an FPGA (Field-Programmable Gate Array), or a combination thereof.

[0017] The components of the positioning device 3 are not limited to those realized by dedicated hardware, and the positioning device 3 may be realized by software, firmware, or a combination of software and firmware. Software or firmware is stored as a program in the memory of a computer. A computer refers to hardware that executes a program, and includes, for example, a CPU (Central Processing Unit), a GPU (Graphics Processing Unit), a central processing unit, a processing unit, an arithmetic unit, a microprocessor, a microcomputer, a processor, or a DSP (Digital Signal Processor).

[0018] 3 is a hardware configuration diagram of a computer when the positioning device 3 is realized by software, firmware, etc. When the positioning device 3 is realized by software, firmware, etc., programs for causing a computer to execute the respective processing procedures of the signal acquisition unit 11, the position candidate calculation unit 12, and the target position identification unit 13 are stored in a memory 31. Then, a processor 32 of the computer executes the programs stored in the memory 31.

[0019] 2 shows an example in which each of the components of the positioning device 3 is realized by dedicated hardware, while Fig. 3 shows an example in which the positioning device 3 is realized by software, firmware, etc. However, this is merely an example, and some of the components in the positioning device 3 may be realized by dedicated hardware, and the remaining components may be realized by software, firmware, etc.

[0020] Next, the operation of the positioning device 3 shown in Fig. 1 will be described. Fig. 4 is a flowchart showing a positioning method, which is a processing procedure of the positioning device 3. A target, which is a radio wave source, may repeatedly radiate pulse signals. When pulse signals are repeatedly radiated from the target, the first satellite 1-1 receives each pulse signal. The first satellite 1-1 receives the first received signal p, which is a received signal of each pulse signal. １ (t ａ ) is transmitted to the antenna 2-1. The first received signal p １ (t ａ ) is the time when the first satellite 1-1 receives the pulse signal. ａ The first received signal p １ (t ａ ) is the reception time t ａ Contains information on:

[0021] When the pulse signals are repeatedly emitted from the target, the second satellite 1-2 receives each pulse signal. The second satellite 1-2 receives the second received signal p ２ (t ｂ ) is transmitted to the antenna 2-2. The second received signal p ２ (t ｂ ) is the time when the second satellite 1-2 receives the pulse signal. ｂ The second received signal p ２ (t ｂ ) is the reception time t ｂ Contains information on:

[0022] The antenna 2-1 receives the first received signal p transmitted from the first satellite 1-1. １ (t ａ ) and a first received signal p１ (t ａ ) to the positioning device 3. The antenna 2-2 receives the second received signal p ２ (t ｂ ) and a second received signal p ２ (t ｂ ) to the positioning device 3.

[0023] The signal acquisition unit 11 receives a first received signal p from a first satellite 1-1 via an antenna 2-1. １ (t ａ ) from the second satellite 1-2 via the antenna 2-2 (step ST1 in FIG. 4). ２ (t ｂ ) (step ST2 in FIG. 4). The signal acquisition unit 11 acquires the first received signal p １ (t ａ ) and the second received signal p ２ (t ｂ ) to the position candidate calculation unit 12 and the target position identification unit 13, respectively.

[0024] The position candidate calculation unit 12 receives the first received signal p from the signal acquisition unit 11. １ (t ａ ) and the second received signal p ２ (t ｂ Since the orbit of the first satellite 1-1 is known, the reception time t ａ The position s of the first satellite 1-1 at １ (t ａ ) is known. In addition, the orbit of the second satellite 1-2 is known, so the reception time t ｂ The position s of the second satellite 1-2 at ２ (t ｂ ) is known. The position s of the first satellite 1-1 １ (t ａ ) and the position s of the second satellite 1-2 ２ (t ｂ ) may be stored in an internal memory of the position candidate calculation unit 12 or may be provided from outside the positioning device 3, for example.

[0025] The position candidate calculation unit 12 calculates the time t of reception of each pulse signal by the first satellite 1-1, assuming that the target position is u, as shown in the following equation (1): ａ and the reception time t of each pulse signal by the second satellite 1-2. ｂ The first equation is specified for the time difference τ between the target and the first satellite 1-1. The time difference τ is calculated, for example, by correlation processing between a plurality of received signals. The process of calculating the time difference τ by correlation processing is a known technique, so a detailed explanation will be omitted. FIG. 5 is an explanatory diagram showing the relationship between the target position u and the respective positions of the first satellite 1-1 and the second satellite 1-2. In the example of FIG. 5, the target is assumed to exist on the surface of the Earth. In FIG. 5, v １ is the reception time t ａ The velocity of the first satellite 1-1 at ２ is the reception time t ｂ is the velocity of the second satellite 1-2 at r １ is the reception time t ａ the distance between the first satellite 1-1 and the target at r ２ is the reception time t ｂ is the distance between the second satellite 1-2 and the target at

[0026] In equation (1), c is the propagation speed of the pulse signal.

[0027] The position candidate calculation unit 12 calculates the first received signal p １ (t ａ ) and the Doppler frequency contained in the second received signal p ２ (t ｂ The frequency difference Δf is calculated, for example, by correlation processing between a plurality of received signals. The process of calculating the frequency difference Δf by correlation processing is a well-known technique, and therefore a detailed description thereof will be omitted.

[0028] In formula (2), f ０ is the center frequency of the received signal. １ , v ２is known and may be stored in the internal memory of the position candidate calculation unit 12, or may be provided from outside the positioning device 3, for example.

[0029] The position candidate calculation unit 12 calculates one or more position candidates for the target by solving the simultaneous equations of the first equation shown in Equation (1) and the second equation shown in Equation (2) using the constraint condition shown in Equation (5) below (step ST3 in FIG. 4). The constraint condition shown in Equation (5) requires that the target exists on the surface of the Earth.

[0030] In formula (5), R Ｅ is the radius of the Earth.

[0031] The position candidate calculated by the position candidate calculation unit 12 is the position of the intersection of a TDOA (Time Difference Of Arrival) curve and an FDOA (Frequency Difference Of Arrival) curve, as shown in Fig. 6. Fig. 6 is an explanatory diagram showing the position candidate calculated by the position candidate calculation unit 12. The TDOA is calculated based on the first received signal p １ (t ａ ) and the second received signal p ２ (t ｂ ) in the time direction. The FDOA is calculated by calculating the correlation between the first received signal p １ (t ａ ) and the second received signal p ２ (t ｂ ) in the frequency direction.

[0032] The first received signal p １ (t ａ ) and the second received signal p ２ (t ｂ) relate to a pulse signal that is repeatedly emitted, and therefore ambiguity occurs due to the repetition of the pulse signal. In other words, the position candidates calculated by the position candidate calculation unit 12 include position candidates that indicate the position of a virtual image in addition to position candidates that indicate the true position of the target, as shown in FIG. 7. FIG. 7 is an explanatory diagram showing the true position of the target and the position of a virtual image. In FIG. 7, x indicates the position of the ambiguity, which is a virtual image. The reason for the ambiguity is that multiple peaks appear on the map of TDOA and FDOA as the pulse signal is repeated, as shown in FIG. 8. If the signal emitted from the target is a continuous wave, only one peak appears on the map of TDOA and FDOA, and therefore no ambiguity occurs.

[0033] 8 is an explanatory diagram showing how multiple peaks appear on a map of TDOA and FDOA as the pulse signal is repeated. The position candidate calculation unit 12 outputs information indicating one or more position candidates of the target to the target position identification unit 13. FIG. 9 is a diagram showing the reception times t ａ and the reception time t of each pulse signal by the second satellite 1-2. ｂ 1 is an explanatory diagram showing the relationship between the time difference τ between the reception time t and the target and the TDOA of one or more position candidates of the target. ａ and reception time t ｂ The time change of the time difference τ between the target and the virtual image corresponds to the time change of the TDOA related to the true position of the target, but does not correspond to the time change of the TDOA related to the virtual image position. In FIG. 9, the solid lines show the theoretical values ​​of TDOA when it is assumed that the target actually exists at each position candidate. A shows the time change of the TDOA related to the true position of the target, and B to F show the time change of the TDOA related to the virtual image position. The dashed lines show the time change of the TDOA related to the reception time t ａ and reception time t ｂ This shows the change in the time difference between the received signal and the actual measured value calculated by correlation processing between multiple received signals.

[0034] FIG. 10 shows the first received signal p １ (t ａ) and the Doppler frequency contained in the second received signal p ２ (t ｂ 1 is an explanatory diagram showing the relationship between the time change of the frequency difference Δf between the Doppler frequency included in the first received signal p and the time change of the FDOA for one or more position candidates of the target. １ (t ａ ) and the Doppler frequency contained in the second received signal p ２ (t ｂ The time change of the frequency difference Δf from the Doppler frequency included in the first received signal p corresponds to the time change of the FDOA related to the true position of the target, but does not correspond to the time change of the FDOA related to the position of the virtual image. In FIG. 10, the solid lines show the theoretical values ​​of the FDOA when it is assumed that the target actually exists at each position candidate. A shows the time change of the FDOA related to the true position of the target, and B to F show the time change of the FDOA related to the position of the virtual image. The dashed lines show the time change of the FDOA related to the first received signal p １ (t ａ ) and the Doppler frequency contained in the second received signal p ２ (t ｂ ) and is an actual measurement value calculated by correlation processing between a plurality of received signals.

[0035] The target position specifying unit 13 receives the first received signal p from the signal acquiring unit 11. １ (t ａ ) and the second received signal p ２ (t ｂ ) The target position identifying unit 13 acquires information indicating one or more position candidates of the target from the position candidate calculation unit 12. The target position identifying unit 13 selects a position candidate indicating the true position of the target from the one or more position candidates of the target based on the time change τ of the time difference and the time change of the frequency difference Δf (step ST4 in FIG. 4). Below, a specific description will be given of the process of selecting a position candidate indicating the true position of the target by the target position identifying unit 13.

[0036] The target position specifying unit 13 receives the pulse signals from the first satellite 1-1 at the time t ａ and the reception time t of each pulse signal by the second satellite 1-2.ｂ The target position specifying unit 13 selects a candidate for the TDOA of the true target from one or more position candidates of the target based on the change in time of the time difference τ. Specifically, the target position specifying unit 13 selects a candidate for the TDOA of the true target from the change in time of the TDOA of one or more position candidates of the target. ａ and reception time t ｂ In the example of Fig. 9, the time change A of the TDOA is selected.

[0037] The target position specifying unit 13 receives the first received signal p １ (t ａ ) and the Doppler frequency contained in the second received signal p ２ (t ｂ The target position identification unit 13 calculates the time change of the frequency difference Δf between the Doppler frequency included in the target position and the Doppler frequency included in the target position. The target position identification unit 13 selects a candidate for the FDOA of the true target from one or more position candidates calculated by the position candidate calculation unit 12 based on the time change of the frequency difference Δf. Specifically, the target position identification unit 13 selects, as the candidate for the FDOA of the true target, the time change of the FDOA corresponding to the change in the frequency difference Δf from the time changes of the FDOA related to one or more position candidates of the target. In the example of FIG. 10 , the FDOA time change A is selected. The target position identification unit 13 calculates the true position of the target by performing new position location using the selected candidate for the TDOA of the true target and the selected candidate for the FDOA of the true target. Since the true position of the target is the position where the candidate for the TDOA of the true target and the candidate for the FDOA of the true target intersect, the position location here is to calculate the position where the candidate for the TDOA of the true target and the candidate for the FDOA of the true target intersect.

[0038] In the first embodiment described above, the positioning device 3 is configured to include a signal acquisition unit 11 that, when pulse signals are repeatedly emitted from a target, acquires first received signals, which are received signals of each pulse signal, from a first satellite 1-1 that has received each pulse signal, and acquires second received signals, which are received signals of each pulse signal, from a second satellite 1-2 that has received each pulse signal. The positioning device 3 also includes a position candidate calculation unit 12 that calculates one or more position candidates for the target using a first equation relating to the time difference between the reception time of each pulse signal by the first satellite 1-1 and the reception time of each pulse signal by the second satellite 1-2, and a second equation relating to the frequency difference between the Doppler frequency included in each first received signal and the Doppler frequency included in each second received signal, and a target position identification unit 13 that selects a position candidate that indicates the true position of the target from the one or more position candidates calculated by the position candidate calculation unit 12, based on a time change in the time difference and a time change in the frequency difference. Therefore, the positioning device 3 can calculate the true position of the target even if the signals emitted toward the target are pulse signals.

[0039] Second Embodiment In a second embodiment, a positioning device 3 including a differential calculation unit 14 that time-differentiates a function of time that represents a time difference will be described.

[0040] Fig. 11 is a configuration diagram showing a positioning system including a positioning device 3 according to embodiment 2. In Fig. 11, the same reference numerals as in Fig. 1 indicate the same or corresponding parts, and detailed description thereof will be omitted. Fig. 12 is a hardware configuration diagram showing the hardware of the positioning device 3 according to embodiment 2. In Fig. 12, the same reference numerals as in Fig. 2 indicate the same or corresponding parts, and detailed description thereof will be omitted. The positioning device 3 includes a signal acquisition unit 11, a differential calculation unit 14, a position candidate calculation unit 15, and a target position identification unit 13.

[0041] The differential calculation unit 14 is realized by, for example, a differential calculation circuit 24 shown in FIG. 12. The differential calculation unit 14 receives the first received signal p １ (t ａ ) and the second received signal p ２ (tｂ The differential calculation unit 14 obtains the reception times t ａ and the reception time t of each pulse signal by the second satellite 1-2. ｂ The differential calculation unit 14 determines a first equation relating to the time difference τ between the reception time t ａ and reception time t ｂ The derivative calculation unit 14 outputs the first equation and the time-differentiated function to the position candidate calculation unit 15.

[0042] The position candidate calculation unit 15 is realized by, for example, a position candidate calculation circuit 25 shown in FIG. 12. The position candidate calculation unit 15 acquires the first equation and the time-differentiated function from the differential calculation unit 14. The position candidate calculation unit 15 calculates one or more position candidates for the target using the first equation and the time-differentiated function. The time-differentiated function is calculated by dividing the first received signal p １ (t ａ ) and the Doppler frequency contained in the second received signal p ２ (t ｂ The position candidate calculation unit 15 outputs information indicating one or more position candidates of the target to the target position identification unit 13.

[0043] 11, it is assumed that the signal acquisition unit 11, the differential calculation unit 14, the position candidate calculation unit 15, and the target position identification unit 13, which are components of the positioning device 3, are each realized by dedicated hardware as shown in Fig. 12. That is, it is assumed that the positioning device 3 is realized by a signal acquisition circuit 21, a differential calculation circuit 24, a position candidate calculation circuit 25, and a target position identification circuit 23. Each of the signal acquisition circuit 21, the differential calculation circuit 24, the position candidate calculation circuit 25, and the target position identification circuit 23 corresponds to, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC, an FPGA, or a combination thereof.

[0044] The components of the positioning device 3 are not limited to those realized by dedicated hardware, and the positioning device 3 may be realized by software, firmware, or a combination of software and firmware. When the positioning device 3 is realized by software, firmware, or the like, programs for causing a computer to execute the respective processing procedures of the signal acquisition unit 11, the differential calculation unit 14, the position candidate calculation unit 15, and the target position identification unit 13 are stored in a memory 31 shown in Fig. 3. Then, a processor 32 shown in Fig. 3 executes the programs stored in the memory 31.

[0045] 12 shows an example in which each of the components of the positioning device 3 is realized by dedicated hardware, while Fig. 3 shows an example in which the positioning device 3 is realized by software, firmware, etc. However, this is merely an example, and some of the components in the positioning device 3 may be realized by dedicated hardware, and the remaining components may be realized by software, firmware, etc.

[0046] Next, the operation of the positioning device 3 shown in Fig. 11 will be described. The signal acquisition unit 11 receives a first received signal p from a first satellite 1-1 via an antenna 2-1. １ (t ａ ) from the second satellite 1-2 via the antenna 2-2. ２ (t ｂ The signal acquisition unit 11 acquires the first received signal p １ (t ａ ) and the second received signal p ２ (t ｂ ) to the differential calculation unit 14, the position candidate calculation unit 15, and the target position identification unit 13, respectively.

[0047] The differential calculation unit 14 receives the first received signal p from the signal acquisition unit 11. １ (t ａ ) and the second received signal p ２ (t ｂ Since the orbit of the first satellite 1-1 is known, the reception time t ａThe position s of the first satellite 1-1 at １ (t ａ ) is known. In addition, the orbit of the second satellite 1-2 is known, so the reception time t ｂ The position s of the second satellite 1-2 at ２ (t ｂ ) is known. The position s of the first satellite 1-1 １ (t ａ ) and the position s of the second satellite 1-2 ２ (t ｂ ) may be stored in an internal memory of the differential calculation unit 14, or may be provided from outside the positioning device 3.

[0048] The differential calculation unit 14, like the position candidate calculation unit 12 shown in FIG. 1, calculates the first received signal p １ (t ａ ) and the second received signal p ２ (t ｂ ) to identify a first equation. The derivative calculation unit 14 time-differentiates the time function representing the TDOA, as shown in, for example, FIG. 9 , as shown in the following equation (6). The derivative calculation unit 14 outputs the first equation and the time-differentiated function to the position candidate calculation unit 15.

[0049]

[0050] The position candidate calculation unit 15 acquires the first equation and the time-differentiated function from the differential calculation unit 14. The position candidate calculation unit 15 calculates one or more position candidates for the target using the first equation and the time-differentiated function. Because the time-differentiated function corresponds to the second equation, the position candidate calculation unit 15 can calculate one or more position candidates for the target using the first equation and the time-differentiated function. The position candidate calculation unit 15 outputs information indicating the one or more position candidates for the target to the target position identification unit 13.

[0051] In the second embodiment described above, the positioning device 3 is configured to include a derivative calculation unit 14 that time-differentiates a time function that represents a time difference, and the position candidate calculation unit 15 calculates one or more position candidates of the target using the first equation and the function after time differentiation by the derivative calculation unit 14, instead of using the first equation and the second equation. Therefore, the positioning device 3 can calculate the true position of the target even if an error is included in either the Doppler frequency included in each of the first received signals or the Doppler frequency included in each of the second received signals.

[0052] Third Embodiment In a third embodiment, a positioning device 3 including an integral calculation unit 16 that time-integrates a function of time that represents a frequency difference will be described.

[0053] Fig. 13 is a configuration diagram showing a positioning system including a positioning device 3 according to embodiment 3. In Fig. 13, the same reference numerals as in Fig. 1 indicate the same or corresponding parts, and detailed description thereof will be omitted. Fig. 14 is a hardware configuration diagram showing the hardware of the positioning device 3 according to embodiment 3. In Fig. 14, the same reference numerals as in Fig. 2 indicate the same or corresponding parts, and detailed description thereof will be omitted. The positioning device 3 includes a signal acquisition unit 11, an integral calculation unit 16, a position candidate calculation unit 17, and a target position identification unit 13.

[0054] The integral calculation unit 16 is realized by an integral calculation circuit 26 shown in Fig. 14. The integral calculation unit 16 receives the first received signal p １ (t ａ ) and the second received signal p ２ (t ｂ ) is obtained. The integral calculation unit 16, like the position candidate calculation unit 12 shown in FIG. 1, obtains the first received signal p １ (t ａ ) and the Doppler frequency contained in the second received signal p ２ (t ｂ The integral calculation unit 16 time-integrates a function of time that represents the FDOA, which is the frequency difference Δf. The integral calculation unit 16 outputs the second equation and the time-integrated function to the position candidate calculation unit 17.

[0055] The position candidate calculation unit 17 is realized by, for example, the position candidate calculation circuit 27 shown in FIG. 14. The position candidate calculation unit 17 acquires the second equation and the function after time integration from the integral calculation unit 16. The position candidate calculation unit 17 calculates one or more position candidates for the target using the second equation and the function after time integration. The function after time integration is calculated based on the reception time t of each pulse signal by the first satellite 1-1. ａ and the reception time t of each pulse signal by the second satellite 1-2. ｂ This corresponds to the first equation regarding the time difference τ between the target and the target position. The position candidate calculation unit 17 outputs information indicating one or more position candidates for the target to the target position identification unit 13.

[0056] 13, it is assumed that the signal acquisition unit 11, integral calculation unit 16, position candidate calculation unit 17, and target position identification unit 13, which are components of the positioning device 3, are each realized by dedicated hardware as shown in Fig. 14. That is, it is assumed that the positioning device 3 is realized by a signal acquisition circuit 21, integral calculation circuit 26, position candidate calculation circuit 27, and target position identification circuit 23. Each of the signal acquisition circuit 21, integral calculation circuit 26, position candidate calculation circuit 27, and target position identification circuit 23 corresponds to, for example, a single circuit, a composite circuit, a programmed processor, a parallel programmed processor, an ASIC, an FPGA, or a combination thereof.

[0057] The components of the positioning device 3 are not limited to those realized by dedicated hardware, and the positioning device 3 may be realized by software, firmware, or a combination of software and firmware. When the positioning device 3 is realized by software, firmware, or the like, programs for causing a computer to execute the respective processing procedures of the signal acquisition unit 11, the integral calculation unit 16, the position candidate calculation unit 17, and the target position identification unit 13 are stored in a memory 31 shown in Fig. 3. Then, a processor 32 shown in Fig. 3 executes the programs stored in the memory 31.

[0058] 14 shows an example in which each of the components of the positioning device 3 is realized by dedicated hardware, while Fig. 3 shows an example in which the positioning device 3 is realized by software, firmware, etc. However, this is merely an example, and some of the components in the positioning device 3 may be realized by dedicated hardware, and the remaining components may be realized by software, firmware, etc.

[0059] Next, the operation of the positioning device 3 shown in Fig. 13 will be described. The signal acquisition unit 11 receives a first received signal p from a first satellite 1-1 via an antenna 2-1. １ (t ａ ) from the second satellite 1-2 via the antenna 2-2. ２ (t ｂ The signal acquisition unit 11 acquires the first received signal p １ (t ａ ) and the second received signal p ２ (t ｂ ) to the integral calculation unit 16, the position candidate calculation unit 17, and the target position identification unit 13, respectively.

[0060] The integral calculation unit 16 receives the first received signal p from the signal acquisition unit 11. １ (t ａ ) and the second received signal p ２ (t ｂ Since the orbit of the first satellite 1-1 is known, the reception time t ａ The position s of the first satellite 1-1 at １ (t ａ ) is known. In addition, the orbit of the second satellite 1-2 is known, so the reception time t ｂ The position s of the second satellite 1-2 at ２ (t ｂ ) is known. The position s of the first satellite 1-1 １ (t ａ ) and the position s of the second satellite 1-2 ２ (t ｂ ) may be stored in the internal memory of the integral calculation unit 16, or may be provided from outside the positioning device 3, for example.

[0061] The integral calculation unit 16, like the position candidate calculation unit 12 shown in FIG. 1, calculates the first received signal p １ (t ａ ) and the second received signal p ２ (t ｂ ) to identify a second equation. The integral calculation unit 16 time-integrates a time function Δf(t) representing the FDOA, as shown in, for example, FIG. 10 , as shown in the following equation (7). The integral calculation unit 16 outputs the second equation and the time-integrated function to the position candidate calculation unit 17.

[0062]

[0063] The position candidate calculation unit 17 acquires the second equation and the time-integrated function from the integral calculation unit 16. The position candidate calculation unit 17 calculates one or more position candidates for the target using the second equation and the time-integrated function. Because the time-integrated function corresponds to the first equation, the position candidate calculation unit 17 can calculate one or more position candidates for the target using the second equation and the time-integrated function. The position candidate calculation unit 17 outputs information indicating the one or more position candidates for the target to the target position identification unit 13.

[0064] In the third embodiment described above, the positioning device 3 is configured to include an integral calculation unit 16 that time-integrates a function of time that represents the frequency difference, and the position candidate calculation unit 17 calculates one or more position candidates for the target using the second equation and the function after time integration by the integral calculation unit 16, instead of using the first equation and the second equation. Therefore, the positioning device 3 calculates one or more position candidates for the target using the reception time t ａ , or the reception time t of each pulse signal by the second satellite 1-2 ｂ Even if any of the above contains an error, the true position of the target can be calculated.

[0065] In addition, the present disclosure allows for free combination of the respective embodiments, modification of any of the components of the respective embodiments, or omission of any of the components of the respective embodiments.

[0066] The positioning device according to the present disclosure can be used to measure the position of a ship or the like, for example.

[0067] 1-1 First satellite, 1-2 Second satellite, 2-1 Antenna, 2-2 Antenna, 3 Positioning device, 11 Signal acquisition unit, 12 Position candidate calculation unit, 13 Target position identification unit, 14 Differential calculation unit, 15 Position candidate calculation unit, 16 Integration calculation unit, 17 Position candidate calculation unit, 21 Signal acquisition circuit, 22 Position candidate calculation circuit, 23 Target position identification circuit, 24 Differential calculation circuit, 25 Position candidate calculation circuit, 26 Integration calculation circuit, 27 Position candidate calculation circuit, 31 Memory, 32 Processor.

Claims

1. A positioning device comprising: a signal acquisition unit that, when pulse signals are repeatedly emitted from a target, acquires first received signals that are received signals of each pulse signal from a first satellite that received each pulse signal, and acquires second received signals that are received signals of each pulse signal from a second satellite that received each pulse signal; a position candidate calculation unit that calculates one or more position candidates for the target using a first equation related to the time difference between the time each pulse signal is received by the first satellite and the time each pulse signal is received by the second satellite, and a second equation related to the frequency difference between the Doppler frequency included in each first received signal and the Doppler frequency included in each second received signal; and a target position identification unit that selects a position candidate that indicates the true position of the target from the one or more position candidates calculated by the position candidate calculation unit, based on the time difference and the frequency difference over time.

2. The positioning device according to claim 1, characterized in that the target position identification unit determines the change over time in the time difference between the reception time of each pulse signal by the first satellite and the reception time of each pulse signal by the second satellite.

3. The positioning device according to claim 1, characterized in that the target position identification unit determines the change over time in the frequency difference between the Doppler frequency contained in each first received signal and the Doppler frequency contained in each second received signal.

4. A positioning device as described in any one of claims 1 to 3, characterized in that the position candidate calculation unit calculates one or more position candidates for the target using the constraint that the target exists on the surface of the Earth, the first equation, and the second equation.

5. A positioning device as described in any one of claims 1 to 4, characterized in that it comprises a derivative calculation unit that time-differentiates a function of time representing the time difference, and the position candidate calculation unit calculates one or more position candidates for the target using the first equation and the function after time differentiation by the derivative calculation unit, instead of using the first equation and the second equation.

6. A positioning device as claimed in any one of claims 1 to 4, characterized in that it comprises an integral calculation unit that time-integrates a function of time representing the frequency difference, and the position candidate calculation unit calculates one or more position candidates for the target by using the second equation and the function after time integration by the integral calculation unit, instead of using the first equation and the second equation.

7. A positioning method in which, when pulse signals are repeatedly emitted from a target, a signal acquisition unit acquires, from a first satellite that received each pulse signal, a first received signal that is a received signal of each pulse signal, and acquires, from a second satellite that received each pulse signal, a second received signal that is a received signal of each pulse signal; a position candidate calculation unit calculates one or more position candidates for the target using a first equation related to the time difference between the time each pulse signal was received by the first satellite and the time each pulse signal was received by the second satellite, and a second equation related to the frequency difference between the Doppler frequency included in each first received signal and the Doppler frequency included in each second received signal; and a target position identification unit selects, from the one or more position candidates calculated by the position candidate calculation unit, a position candidate that indicates the true position of the target based on the time difference and the frequency difference over time.

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