Estimation device, mobile body, earth station, system, method, and program for estimating position of signal generation source

Abstract

To provide an estimation device and the like for estimating a position of a signal generation source.SOLUTION: An estimation device includes: a device for determining frequency characteristics of a signal received by one moving object at a plurality of reception times; a device for determining, for a reception time set consisting of two reception times among the plurality of reception times, frequency versus correlation value characteristics that indicate a relation between a correlation value between the frequency characteristics of two reception times in the reception time set and the frequency; a device for calculating, for the reception time set, a Doppler frequency change amount that is assumed at a candidate estimated position of a signal generation source based on the position and velocity of the moving object at the two reception times in the reception time set; a device for determining, based on the frequency versus correlation value characteristics and the assumed Doppler frequency change amount for the reception time set, candidate estimated position versus correlation value characteristics that indicate a relation between the candidate estimated position for the reception time set and the correlation value; and a device for determining an estimated position of the signal generation source based on the candidate estimated position versus correlation value characteristics for one or more reception time sets.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to an estimation device, a mobile object, an earth station, a system, a method, and a program for estimating the position of a signal source. [Background technology]

[0002] A method for estimating the location of a radio wave source using Doppler frequency in a satellite system is known (for example, Patent Document 1). In Patent Document 1, radio waves at each transmission location are restored from the estimated Doppler change amount, reception time delay, and reception time, and the degree of coincidence is calculated, and the location with the highest degree of coincidence is determined to be the estimated location of the radio wave source. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] U.S. Patent No. 11,480,649 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the method described in Patent Document 1, it is necessary to accurately calculate the amount of shift due to the Doppler effect in order to restore the original radio wave. Errors are likely to occur in the stage of calculating the amount of shift from the acquired signal, making it difficult to accurately estimate the position of the transmission source.

[0005] The present invention has been made to solve the above-mentioned problems, and has as its object to estimate the position of a signal source without the need to accurately calculate the amount of Doppler shift. [Means for solving the problem]

[0006] 1. An estimation device of one embodiment of the present invention is an estimation device that estimates the position of a signal source, and includes: a frequency characteristics determination device that determines frequency characteristics of a signal received by a single moving object at multiple reception times; a frequency vs. correlation value characteristics determination device that determines, for a reception time set consisting of two reception times from the multiple reception times, frequency vs. correlation value characteristics that indicate the relationship between the correlation value between the frequency characteristics of two reception times in the reception time set and the frequency; an assumed Doppler frequency change calculation device that calculates, for the reception time set, an assumed Doppler frequency change at a candidate estimated position of the signal source based on the position and velocity of the moving object at the two reception times in the reception time set; a candidate estimated position vs. correlation value characteristics determination device that determines, based on the frequency vs. correlation value characteristics and the assumed Doppler frequency change for the reception time set, a candidate estimated position vs. correlation value characteristics that indicate the relationship between the candidate estimated position and the correlation value for the reception time set; and an estimated position determination device that determines an estimated position of the signal source based on the candidate estimated position vs. correlation value characteristics for one or more reception time sets.

[0007] The estimated position determination device in the estimation device described in Section 2.1 may determine, as the estimated position of the signal source, a candidate estimated position for which the value calculated by a function having a correlation value determined based on the estimated candidate position versus correlation value characteristics for a plurality of reception time sets as an argument is equal to or greater than a predetermined value.

[0008] 3. The estimation device according to claim 2, wherein the function is a function that calculates the integral value of an argument.

[0009] In the estimation device described in sections 4.1 to 4.3, one of the two reception times in each of the plurality of reception time sets may be a common reception time for the plurality of reception time sets, and the other may be a reception time that differs for each set.

[0010] In the estimation device described in sections 5.1 to 5.3, none of the two reception times in each of the plurality of reception time sets may be a common reception time in the plurality of reception time sets.

[0011] 6. A moving body according to one embodiment of the present invention may include the estimation device according to any one of items 1 to 5.

[0012] 7. In one embodiment of the present invention, an earth station may include an estimation device according to any one of items 1 to 5.

[0013] 8. An estimation system in one embodiment of the present invention is an estimation system for estimating the position of a signal source, including one or more mobile bodies and one or more earth stations, and includes: a frequency characteristics determination device that determines the frequency characteristics of a signal received by a single mobile body at multiple reception times; a frequency band correlation value characteristic determination device that determines, for a reception time set consisting of two reception times from the multiple reception times, a frequency vs. correlation value characteristic that indicates the relationship between the correlation value between the frequency characteristics of the two reception times in the reception time set and the frequency; an assumed Doppler frequency change calculation device that calculates, for a reception time set, an assumed Doppler frequency change at a candidate estimated position of the signal source based on the position and velocity of the mobile body at the two reception times in the reception time set; a candidate estimated position vs. correlation value characteristic determination device that determines, based on the frequency vs. correlation value characteristic and the assumed Doppler frequency change for the reception time set, a candidate estimated position vs. correlation value characteristic that indicates the relationship between the candidate estimated position and the correlation value for the reception time set; and an estimated position determination device that determines an estimated position of the signal source based on the candidate estimated position vs. correlation value characteristic for one or more reception time sets.

[0014] In the system described in Section 9.8, each of the devices may be provided in either the mobile unit or the earth station.

[0015] In the system described in Section 10.8, the devices may be provided in a distributed manner in the mobile unit and the earth station.

[0016] 11. An estimation method in one embodiment of the present invention is a method for estimating the position of a signal source, which includes causing one or more computers to determine frequency characteristics of a signal received by a single moving object at multiple reception times, and for a reception time set consisting of two reception times from the multiple reception times, determine frequency versus correlation value characteristics indicating the relationship between the correlation value between the frequency characteristics of the two reception times in the reception time set and the frequency, calculate an expected Doppler frequency change at a candidate estimated position of the signal source for the reception time set based on the position and velocity of the moving object at the two reception times in the reception time set, determine a candidate estimated position versus correlation value characteristic indicating the relationship between the candidate estimated position for the reception time set and the correlation value based on the frequency versus correlation value characteristic and the expected Doppler frequency change for the reception time set, and determine an estimated position of the signal source based on the candidate estimated position versus correlation value characteristics for one or more reception time sets.

[0017] 12. A program according to one embodiment of the present invention can cause one or more computers to execute the method described in paragraph 11. [Effects of the Invention]

[0018] According to an embodiment of the present invention, the position of a signal source can be estimated without calculating the amount of Doppler shift. [Brief explanation of the drawings]

[0019] [Figure 1] 1 is a diagram illustrating a configuration of a position estimation system according to an embodiment. [Figure 2] FIG. 2 is a diagram showing the detailed configuration of a mobile body and an earth station including an estimation device. [Figure 3] FIG. 2 is a diagram illustrating a detailed configuration of an estimation device. [Figure 4] 1 is an example of an operation flowchart of an estimation system including an estimation device according to an embodiment. [Figure 5] 10 is an example of a time-domain waveform of a radio wave received by a mobile body. [Figure 6A]10 is an example of frequency characteristics of a received signal at a reception time t0 in the embodiment. [Figure 6B] 10 is an example of frequency characteristics of a received signal at a reception time t1 in the embodiment. [Figure 7] FIG. 1 is a diagram for explaining the concept of signal correlation processing. [Figure 8] 10 is an example of frequency versus correlation value characteristics (time t0-t1) in the embodiment. [Figure 9A] 10 is a diagram illustrating an example of an assumed Doppler frequency change characteristic (time t0-t1) according to an embodiment. [Figure 9B] 10 is a diagram illustrating an example of an assumed Doppler frequency change characteristic (time t0-t2) in the embodiment. [Figure 9C] 10 is a diagram illustrating an example of an assumed Doppler frequency change amount characteristic (time t0-t3) in the embodiment. [Figure 10A] 10 is an example of candidate estimated position versus correlation value characteristics (time t0-t1) in the embodiment. [Figure 10B] 10 is an example of candidate estimated position versus correlation value characteristics (time t0-t2) in the embodiment. [Figure 10C] 10 is an example of candidate estimated position versus correlation value characteristics (time t0-t3) in the embodiment. [Figure 11] 10 is a diagram illustrating an example of an integral value characteristic of a correlation value characteristic in the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0020] An estimation device, a mobile object, an earth station, a system, a method, and a program for estimating the position of a signal source according to an embodiment of the present invention will be described with reference to the drawings.

[0021] Fig. 1 is a diagram showing the configuration of an estimation system for estimating the position of a signal source according to this embodiment. As will be described in detail below, the estimation system 1 shown in Fig. 1 is a system that receives signals such as radio waves and estimates the position of the signal source based on the received signals. The estimation system 1 can be used as a radio wave monitoring system.

[0022] The estimation system 1 includes a mobile object 2 and an earth station 3. The mobile object 2 receives signals such as radio waves, and an estimation device provided in the mobile object 2 estimates the position of a signal source based on the received signals and transmits information about the estimated position to the earth station 3. The mobile object 2 may be, for example, an artificial satellite, an aircraft including an unmanned aerial vehicle, or any other device capable of receiving radio waves while moving. In this specification, the mobile object 2 is an artificial satellite. An artificial satellite can move around the Earth on a satellite orbit. The satellite orbit can be, for example, a low Earth orbit (LEO), a medium Earth orbit (MEO), or a geostatinary Earth orbit (GEO), but is not limited to these. In FIG. 1, the mobile object 2 moves along a predetermined satellite orbit 4. For example, the mobile object 2 is located at position 2t0 at time t0, moves to position 2t1 at time t1, and moves to position 2t2 at time t2. Although only one moving body 2 is shown in FIG. 1, the estimation system 1 may include multiple moving bodies 2.

[0023] The estimation system 1 aims to estimate the positions of signal sources 5-1, 5-2, and 5-3 whose positions are unknown. There may be one or more signal sources. The estimation system 1 may include multiple mobile objects 2, but it can estimate the position of a signal source based on a signal received by a single mobile object 2. Fig. 1 shows a coordinate system indicating latitude, longitude, and altitude above sea level.

[0024] The moving body 2 includes a receiver 20, an estimation device 21, a transmitter 22, a position information acquisition device 23, a communication transceiver 25, a control device 26, and a storage device 27, and may also include other components for realizing various functions. These components may include a power supply subsystem including solar panels, batteries, etc., that supplies power to each device mounted on the moving body 2, an attitude control subsystem that controls the attitude of the moving body 2, a propulsion subsystem that propels the moving body 2, a thermal control subsystem that controls the temperature range inside the moving body 2, etc.

[0025] The receiver 20 is a device that receives signals such as radio waves and includes a receiving antenna. The radio waves referred to here may be, for example, electromagnetic waves having a frequency of 3 THz or less, but are not limited thereto. For example, infrared rays or any other waves having a Doppler-shifted waveform may also be used. The receiver 20 receives, for example, radio waves arriving from Earth. In this embodiment, Earth refers to the ground and / or the sea, but the radio waves that the receiver 20 can receive are not limited thereto. That is, radio wave sources include equipment installed on the ground, mobile objects that can move on the ground, ships at sea, aircraft above the ground or sea surface, and spacecraft in outer space. Here, the receiver 20 converts the received analog radio signal into a digital signal representing the time-domain waveform of the radio signal and outputs the digital signal.

[0026] The estimation device 21 is configured with one or more computers and / or one or more processing circuits and storage devices, and estimates the position of a signal source based on a signal such as a received radio wave. A more detailed configuration of the estimation device 21 is shown in FIG. 3. As shown in FIG. 3, the estimation device 21 includes a frequency characteristic determination device 211, a frequency vs. correlation value characteristic determination device 212, an assumed Doppler frequency change calculation device 213, a candidate estimated position vs. correlation value characteristic determination device 214, and an estimated position determination device 215. These devices may be realized by one or more computers and / or processing circuits executing a program stored in a storage device in the estimation device 21, or these functions may be realized by hardware by configuring electronic circuits or the like to realize some or all of the functions.

[0027] The frequency vs. correlation value characteristic determiner 212 determines the frequency characteristics of a signal received by a single mobile unit at multiple reception times. For a reception time pair consisting of two reception times among the multiple reception times, the frequency vs. correlation value characteristic determiner 212 determines a frequency vs. correlation value characteristic indicating the relationship between the correlation value between the frequency characteristics of the two reception times in the reception time pair and the frequency. The assumed Doppler frequency change calculator 213 calculates an assumed Doppler frequency change at a candidate estimated position of a signal source for the reception time pair based on the position and velocity of the mobile unit at the two reception times in the reception time pair. The candidate estimated position vs. correlation value characteristic determiner 214 determines a candidate estimated position vs. correlation value characteristic indicating the relationship between the candidate estimated position and the correlation value for the reception time pair based on the frequency vs. correlation value characteristic and the assumed Doppler frequency change for the reception time pair. The estimated position determiner 215 determines an estimated position of a signal source based on the candidate estimated position vs. correlation value characteristic for one or more reception time pairs.

[0028] In one embodiment, the estimated position determination device 215 can determine, as the estimated position of the signal source, a candidate estimated position for which a value calculated by a function having a correlation value as an argument, determined based on the estimated candidate position vs. correlation value characteristics for a plurality of reception time sets, is equal to or greater than a predetermined value. A plurality of candidate estimated positions may be determined as the estimated position of the signal source. In another embodiment, the candidate estimated position for which the value calculated by the function having a correlation value as an argument is the highest may be determined as the estimated position of the signal source. The estimated position can be specified by latitude and longitude, but can also be an area having a certain range represented by the latitude and longitude.

[0029] The function that takes correlation values ​​as arguments can be a function that calculates the integral of the arguments. One example of a value calculated by a function that takes correlation values ​​as arguments is the sum of correlation values. Alternatively, the function can be a function that integrates a value obtained by multiplying each correlation value by a determined weighting coefficient. The function can be any function that determines a value indicating the magnitude of correlation at a position based on multiple correlation values.

[0030] One of the two reception times in each of a plurality of reception time sets may be a reception time that is common to the plurality of reception time sets, and the other may be a reception time that is different for each set. Furthermore, in another embodiment, a reception time may be used in which none of the two reception times in each of a plurality of reception time sets is a reception time that is common to the plurality of reception time sets.

[0031] In this embodiment, the estimation device 21 acquires its own position and velocity, which are used to calculate the Doppler frequency change expected at the candidate estimated position of the signal source, from the position information acquisition device 23. Here, velocity includes the direction of movement. In other embodiments, the estimation device 21 may determine its own position and velocity based on the predetermined route and time of the moving object, or may acquire the position and velocity from another device such as the earth station 3.

[0032] The estimation device 21 outputs the estimated position to the transmitter 22. The transmitter 22 is a device that transmits information on the estimated position of the signal source input from the estimation device 21, and includes a transmitting antenna. The transmitter 22 transmits the estimated position information to, for example, the earth station 3. Instead of the transmitter 22, the estimation device 21 may transmit the estimated position information from a communication transceiver 25 via a control device.

[0033] The position information acquisition device 23 acquires the position information and speed of the moving object 2. The position information acquisition device 23 can calculate the position and speed of the moving object 2 based on signals from a global navigation satellite system (GNSS), for example, and input them to the estimation device 21.

[0034] The communications transceiver 25 is a device that receives command signals from the earth station 3 and transmits telemetry signals to the earth station 3, and includes a communications antenna. The command signals are signals that include command data for controlling the mobile object 2. The command signals are signals that the control device 26 uses to control each component, and are transmitted from the communications transceiver 25 to the control device 26. The telemetry signals are signals that include telemetry data that indicates the status of the mobile object 2. The communications transceiver 25 demodulates the received command signals and outputs the demodulated signals to the control device 26. The communications transceiver 25 modulates the telemetry signals and transmits them to the earth station 3 via the communications transceiver 25.

[0035] The control device 26 is configured with one or more computers and / or one or more processing circuits, and performs overall control of the mobile object 2. For example, the control device 29 can control the receiver 20, the estimation device 21, the transmitter 22, the position information acquisition device 23, the communication transceiver 25, and the memory device 27. The memory device 27 is configured with memory and / or storage, and stores information necessary for controlling the mobile object 2, etc. The memory device 27 may store a program necessary for controlling the mobile object 2, and each device may be realized by executing this program on one or more computers and / or one or more processing circuits, or these functions may be realized by hardware by configuring electronic circuits, etc., to realize some or all of the functions.

[0036] The earth station 3 is a system for communicating with the mobile object 2. The earth station 3 may be fixedly installed on the ground, or may be deployed on the ground, on the sea, or in a mobile object that can move above the ground or sea surface.

[0037] The earth station 3 comprises a communications transceiver 30 , a control device 31 , and a storage device 32 .

[0038] The communication transceiver 30 includes an antenna for transmitting command signals and receiving telemetry signals, and generates and transmits command signals by modulating control signals for the mobile object 2. The communication transceiver 30 also receives and demodulates telemetry signals and outputs the results to the control device 31. The communication transceiver 30 is further capable of receiving a signal including estimated position information transmitted from the transmitter 22 of the mobile object 2, although the signal containing the estimated position information may be received by another receiver.

[0039] The control device 31 includes input / output devices and a computer and / or processing circuit, and generates control signals for the mobile object 2. The memory device 32 includes memory and / or storage, and stores information necessary for controlling the earth station 3, etc. The memory device 27 stores programs necessary for controlling the mobile object, and each device may be realized by executing these programs on one or more computers and / or one or more processing circuits. Alternatively, these functions may be realized by hardware by configuring electronic circuits or the like to realize some or all of the functions. The memory device 27 can also store the received estimated position. This makes it possible, for example, to identify the position of a ship transmitting a signal and perform necessary processing for that ship.

[0040] In this embodiment, the estimation device 21 is included in the mobile object 2, but part or all of it may be provided in the earth station 3. For example, the mobile object 2 transmits information indicating a signal received by the mobile object 2, which is received by the earth station 3 and input to the estimation device 21 provided in the earth station 3, thereby making it possible to estimate the position of the signal source based on the signal received by the mobile object 2. In yet another embodiment, the estimation device 21 may be provided partly or entirely in a device other than the mobile object 2 and the earth station 3, or the estimation device 21 may be installed as a standalone device, and the signal received by the mobile object 2 may be received via a communication device provided in the estimation device 21 to estimate the position of the signal source.

[0041] Next, the operation of the estimation system 1 in this embodiment will be described with reference to Fig. 4. First, the receiver 20 of the satellite 2, which is a single moving object, receives a signal for a predetermined period, for example, from time t0 to t N The receiver 20 receives radio signals at times t0, t1, t2, t3, . . . t as shown in FIG. N and the time axis waveform of each divided time is sampled at a sampling frequency f s The signal is sampled by the sampling unit 20, converted into a digital signal representing the time-axis waveform, and output to the estimation unit 21.

[0042] The estimation device 21 calculates the time-axis waveform at each time t0, t1, t2, t3, . . . t based on the input digital signal. N In this embodiment, the frequency characteristics are determined based on the time domain waveform using a fast Fourier transform (FFT), but any method may be used as long as it can determine the frequency characteristics of the received signal.

[0043] Since the satellite 2 receives radio waves while moving, the signal frequency f transmitted from the signal source varies depending on the relative moving speed of the signal source relative to the satellite 2. org A radio wave signal with a Doppler frequency f d (Transmitted signal frequency f org+ the shift amount δ due to the Doppler effect). In this embodiment, the moving speed of the satellite 2 is assumed to be sufficiently greater than the moving speed of the signal source, and the signal source is considered to be stationary. As an example, frequency characteristics at times t0 and t1 are shown in FIGS. 6A and 6B. The frequency characteristics indicate the relationship between frequency and amplitude. For example, FIG. 6A shows frequency characteristics that indicate large amplitude between frequencies f1 and f2, while FIG. 6B shows frequency characteristics that indicate large amplitude between frequencies f3 and f4. That is, at time t0, it is considered that a signal with a Doppler frequency between frequencies f1 and f2 was received, and at time t1, it is considered that a signal with a Doppler frequency between frequencies f3 and f4 was received. In this case, although the signal is received from the same signal source, it is possible that the Doppler frequency changed due to the magnitude of the Doppler effect on the radio waves received from the signal source changing as the satellite 2 moved at a certain speed.

[0044] Next, the estimation device 21 determines frequency versus correlation value characteristics (S404). The frequency versus correlation value characteristics indicate the correlation between two frequency characteristics. Any method can be used to determine the frequency versus correlation value characteristics as long as it can determine the correlation between two frequency characteristics. In this embodiment, a method is used to determine signal correlation processing (cross-correlation) of two signals. Signal correlation processing cross-correlation is a method for evaluating how similar two signals are. The larger the value, the more similar the two signals are. Cross-correlation in the frequency domain of a signal is expressed by the following equation (1).

[0045]

number

[0046] F * ti :time t i Frequency characteristics of the signal corresponding to (* indicates Hermitian transpose) Ftx :time t x The frequency characteristics of the signal corresponding to

[0047] where F * ti Consider shifting the frequency characteristics of by various values ​​u on the frequency axis and taking the correlation as shown in the following equation (2).

[0048]

number

[0049] As mentioned above, cross-correlation exhibits a high correlation value when two signals are similar. When two received signals received at different times are transmitted from the same signal source, their frequency characteristics are similar, which is considered to result in a high correlation value. When a receiver receives signals while moving, the signals are received at different Doppler frequencies, and the frequency characteristics shift in the frequency axis direction by the amount of Doppler frequency change. Therefore, as shown in (a) of FIG. 7, even if two received signals are from the same transmission source, the two signals do not overlap, resulting in a small correlation value. In this embodiment, to determine whether two received signals are similar when the Doppler frequency shifts due to a change in the Doppler effect, the correlation value is determined while shifting the frequency characteristics of one of the signals, as shown in Equation (2). When two received signals are from the same transmission source, as shown in (b) of FIG. 7, when the magnitude of the shifted frequency u corresponds to the amount of Doppler frequency change between the two signals, the two signals overlap significantly, resulting in a large correlation value. The Doppler frequency change amount means the frequency difference between a first Doppler frequency affected by the Doppler effect experienced by a first received signal and a second Doppler frequency affected by the Doppler effect experienced by a second received signal.

[0050] Therefore, by using equation (2) above to determine the correlation characteristics between the frequency characteristics of the signals received at the two reception times, the Doppler frequency change of the two signals can be estimated.

[0051] FIG. 8 shows the frequency versus correlation value characteristics between the frequency characteristics at time t0 and time t1 using equation (2). The horizontal axis shows one of the frequency characteristics (F ti ) indicates the shifted frequency u, and the vertical axis indicates the correlation value. Since u shows high correlation values ​​at fa, fb, fc, and fd, it is estimated that signals with Doppler frequency changes corresponding to these frequencies were received at time t0 and time t1. Even when received by a single receiver, signals emitted from sources at different locations experience different Doppler effects. Therefore, the frequency band correlation value characteristics in Figure 8, which show four peaks, indicate the possibility that signals emitted from four signal sources were received. Note that one or more peak frequencies may be false positives.

[0052] In another embodiment, cross-ambiguity may be used as a signal correlation process to determine the correlation between two frequency characteristics. In cross-ambiguity, in addition to shifting the frequency and calculating the correlation, the correlation is also calculated, including a time domain delay, and the time difference and frequency shift at which two signals overlap can be determined. Instead of frequency domain correlation processing, cross-ambiguity is calculated, and then the largest correlation is found for each frequency shift, making it possible to determine an estimated position using processing similar to that when cross-correlation is used.

[0053] In the present embodiment, a reception time set is determined, each set consisting of two reception times from among a plurality of reception times, and a process of determining the frequency versus correlation value characteristics is executed for the two reception times in each determined reception time set, thereby acquiring the frequency versus correlation value characteristics for each reception time set.

[0054] Then, in S406, for each reception time pair, the estimation device 21 calculates the Doppler frequency change amount at the candidate estimated position of the signal source based on the position and velocity of the moving body 2 that received the signal at the two reception times of the reception time pair. The position and velocity of the moving body 2 are acquired from the position information acquisition device 23. For the received signal at one reception time included in one reception time pair, a first estimated Doppler frequency is determined based on the estimated position, direction of movement, and velocity of the signal source. Similarly, for the received signal at the other reception time pair, a second estimated Doppler frequency is determined based on the estimated position, direction of movement, and velocity of the signal source. The difference between the first and second estimated Doppler frequencies is then calculated to calculate the estimated Doppler frequency change amount for the reception time pair at the position. The candidate estimated positions can be one or more arbitrary points. In this embodiment, the candidate estimated positions are points within a predetermined area on the Earth's surface (ground and sea level) and identified by latitude and longitude.

[0055] 9A to 9C are diagrams showing the estimated Doppler frequency change characteristics for each of three reception time pairs (time t0 and time t1, time t0 and time t2, and time t0 and time t3) at each latitude and longitude. The points connected by lines 901 to 905, 911 to 915, and 921 to 925 have the same estimated Doppler frequency change f d1 , f d2 , f d3 , f d4 , f d5 means that f is the expected point. d5 9A to 9C show contour lines of the estimated Doppler frequency change. Figures 9A to 9C can also be considered as maps of the estimated Doppler frequency change relative to latitude and longitude. For the sake of simplicity, nothing is shown for points between the contour lines, but the estimated Doppler frequency change is also calculated for these points and stored in the storage device of the estimation device 21 in association with each latitude and longitude. Here, the estimated Doppler frequency change characteristic for each latitude and longitude is expressed by the function df j (lat (latitude), lon (longitude)). The function df jThe amount of change in Doppler frequency expressed by (lat (latitude), lon (longitude)) may be stored as a table in association with each latitude and longitude, or may be calculated by sequential calculation.

[0056] In this embodiment, one of the reception times included in each reception time group is the same time t0, but it is also possible for the reception times not to include a common reception time, or for the reception times to overlap partially. For example, the reception time groups may not include a common reception time, such as time t0 and time t1, time t2 and time t3, and time t4 and time t5, or they may overlap partially, such as time t0 and time t1, time t1 and time t2, and time t3 and time t4. Any time group may be used as long as it allows the amount of Doppler frequency change to be determined at two reception times.

[0057] In S408, the estimation device 21 determines a candidate estimated position vs. correlation value characteristic indicating the relationship between the candidate estimated position and the correlation value for the reception time set, based on the frequency vs. correlation value characteristic and the estimated Doppler frequency change amount for the reception time set. Furthermore, in S410, the estimation device 21 determines an estimated position of the signal source based on the candidate estimated position vs. correlation value characteristic for one or more reception time sets. In this embodiment, the estimated position is determined based on a value calculated by a function that takes as an argument the correlation value determined based on the estimated candidate position vs. correlation value characteristic for a plurality of reception time sets. Here, the function that takes the correlation value as an argument is a function that calculates the integral value of the argument, and can be expressed by the following equation (3).

[0058]

number

[0059] corr j is a function showing the correlation value characteristic of the candidate estimated position, which indicates the correlation value for latitude lat and longitude lon. The assumed Doppler frequency change amount at each latitude lat and longitude lon in the reception time set j is expressed as a function dfj and a function corr indicating the frequency vs. correlation value characteristic in the reception time set j is calculated based on j The correlation value for the latitude and longitude is determined by substituting F(lat, lon). This is performed for N reception pairs, and the integral value SumF(lat, lon) of the determined correlation value is output. This is performed for each candidate estimated position (latitude, longitude). Then, it is considered that the signal is most likely to have been transmitted from a position where the calculated integral value is large. Here, N is a natural number greater than or equal to 1, and although N may be 1, a multiple number greater than or equal to 2 can improve the accuracy of the location estimation. Improving the estimation accuracy means that the area of ​​the estimated location can be further limited, and the probability of false detection can be reduced.

[0060] In this embodiment, a candidate estimated position for which the integral value of the correlation value determined based on the estimated candidate position vs. correlation value characteristics for a plurality of reception time sets is equal to or greater than a predetermined value is determined as the estimated position of the signal source, but a predetermined number of candidate estimated positions may be estimated in descending order of integral value, or the estimated position may be determined based on the integral value by other methods.

[0061] Figure 10A-C shows the correlation coefficients for the three sets of reception times. j 10A to 10C show an example of a correlation value characteristic (map) for candidate estimated positions, which indicates the relationship between the correlation value calculated by the above and latitude and longitude. The horizontal and vertical axes represent latitude and longitude, and gray areas indicate regions with high correlation values. In FIGS. 10A to 10C, the regions with the highest correlation values ​​are shown in gray for simplification, but each latitude and longitude has its own correlation value, which is stored in estimation device 21. FIG. 11 shows an integral value characteristic (map) that indicates the relationship between the integral value of the correlation value for these three reception time sets and latitude and longitude. Since position 1101 shows an integral value that exceeds the threshold, this candidate estimated position is determined as the estimated position.

[0062] When only one set of reception times is used, the estimated location can be determined by assuming that the signal is emitted from any of the locations in the gray area shown in FIG. 10A, for example.

[0063] In this embodiment, the estimated position is specified by latitude and longitude, but it will be clear to those skilled in the art that it can also be specified by a three-dimensional coordinate system using a method similar to that of the above-described embodiment.

[0064] By using this embodiment, it is possible to estimate the position of a signal source without calculating the amount of Doppler shift. The candidate estimated position-to-correlation position characteristics used in the process of determining the estimated position of the signal source can be based on one reception time set, but the estimation accuracy can be improved by using two or more reception time sets.

[0065] When using conventional methods, for example, the value at which the largest peak appears in Figure 8 is calculated as the Doppler shift amount, and the estimated position must be determined based only on that parameter. However, when multiple peaks appear as in the example shown in Figure 8, a slight momentary error can lead to a large erroneous reading of the Doppler shift amount. In other words, there is a possibility that a different peak may be read, and if an erroneous peak is read, the accuracy of the position estimation decreases. In this embodiment, the correlation value is directly associated with the candidate estimated position, so there is no risk of an erroneous reading of the parameter based on an instantaneous value, which would result in a decrease in the estimation accuracy. By overlapping the correlation values ​​over several time periods, it is possible to estimate that the position with the greatest overlap is most likely to be the signal source, making it less susceptible to the influence of such outliers.

[0066] In this embodiment, the location of a signal source can be estimated based on a signal received by a single moving object. Furthermore, even if there are multiple signal sources, the locations of the multiple signal sources can be estimated based on a signal received by a single moving object.

[0067] In other embodiments of the present invention, the present invention may be a program that realizes the functions of the embodiments of the present invention described above and the processes shown in the flowcharts, or a computer-readable storage medium that stores the program.In still other embodiments, the present invention may be a method that realizes the functions of the embodiments of the present invention described above and the processes shown in the flowcharts.In still other embodiments, the present invention may be a server that can supply a program that realizes the functions of the embodiments of the present invention described above and the processes shown in the flowcharts to a computer.In still other embodiments, the present invention may be a virtual machine that realizes the functions of the embodiments of the present invention described above and the processes shown in the flowcharts.

[0068] In the processes or operations described above, the processes or operations can be freely changed as long as no inconsistencies in the processes or operations occur, such as the use of data that should not yet be available in a certain step. Furthermore, the embodiments described above are merely examples for explaining the present invention, and the present invention is not limited to these examples. The present invention can be embodied in various forms without departing from the spirit of the invention. [Explanation of symbols]

[0069] 1: Estimation system 2: Moving object 3:Earth station 4:Satellite orbit 5: Signal source 20: Receiver 21: Estimation device 22: Transmitter 23: Location information acquisition device 25: Communication transmitter / receiver 26: Control device 27: Storage device 29: Control device 30: Communication transmitter / receiver 31: Control device 32: Storage device 211: Frequency characteristic determination device 212: Frequency vs. correlation value characteristic determination device 213: Estimated Doppler frequency change calculation device 214: Candidate estimated position pair correlation value characterization device 215: Estimated position determination device

Claims

1. An estimation device for estimating a position of a signal source, comprising: a frequency characteristic determination device for determining frequency characteristics of signals received by a single moving object at multiple reception times; a frequency versus correlation value characteristic determining device that determines, for a reception time pair consisting of two reception times among the plurality of reception times, a frequency versus correlation value characteristic that indicates a relationship between a correlation value between frequency characteristics of the two reception times in the reception time pair and a frequency; an estimated Doppler frequency change calculation device that calculates an estimated Doppler frequency change at a candidate estimated position of a signal source based on the position and velocity of the moving object at two reception times of the reception time set; a candidate estimated position vs. correlation value characteristic determining device that determines a candidate estimated position vs. correlation value characteristic indicating a relationship between a candidate estimated position and a correlation value for the reception time set based on the frequency vs. correlation value characteristic for the reception time set and an estimated Doppler frequency change amount; an estimated location determiner for determining an estimated location of a signal source based on candidate estimated location versus correlation value characteristics for one or more reception time sets; An estimation device comprising:

2. 2. The estimation device according to claim 1, wherein the estimated position determination device determines, as the estimated position of the signal source, a candidate estimated position whose value calculated by a function having a correlation value determined based on estimated candidate position versus correlation value characteristics for a plurality of reception time sets as an argument is equal to or greater than a predetermined value.

3. The estimation device according to claim 2 , wherein the function calculates an integral value of an argument.

4. The estimation device according to claim 1 , wherein one of the two reception times in each of the plurality of reception time sets is a common reception time among the plurality of reception time sets, and the other reception time is a different reception time for each of the sets.

5. The estimation device according to claim 1 , wherein none of the two reception times in each of the plurality of reception time sets is a common reception time in the plurality of reception time sets.

6. A moving body including the estimation device according to claim 1.

7. An earth station including the estimator according to claim 1.

8. 1. An estimation system for estimating a location of a signal source, the system comprising one or more mobile objects and one or more earth stations, a frequency characteristic determination device for determining frequency characteristics of signals received by a single moving object at multiple reception times; a frequency versus correlation value characteristic determining device that determines, for a reception time pair consisting of two reception times among the plurality of reception times, a frequency versus correlation value characteristic that indicates a relationship between a correlation value between frequency characteristics of the two reception times in the reception time pair and a frequency; an estimated Doppler frequency change calculation device that calculates an estimated Doppler frequency change at a candidate estimated position of a signal source based on the position and velocity of the moving object at two reception times of the reception time set; a candidate estimated position vs. correlation value characteristic determining device that determines a candidate estimated position vs. correlation value characteristic indicating a relationship between a candidate estimated position and a correlation value for the reception time set based on the frequency vs. correlation value characteristic for the reception time set and an estimated Doppler frequency change amount; an estimated location determiner for determining an estimated location of a signal source based on candidate estimated location versus correlation value characteristics for one or more reception time sets; An estimation system including:

9. The devices are provided in either the mobile unit or the earth station. The estimation system according to claim 8 .

10. The devices are provided in a distributed manner in the mobile unit and the earth station. The estimation system according to claim 8 .

11. 1. A method for estimating a location of a signal source, comprising: determining frequency characteristics of signals received by a single mobile unit at a plurality of reception times; determining a frequency-to-correlation value characteristic indicating a relationship between a correlation value between frequency characteristics of the two reception times of the reception time pair and a frequency for a reception time pair made up of two reception times of the plurality of reception times; calculating, for a set of reception times, an estimated Doppler frequency change at a candidate estimated location of a signal source based on the position and velocity of the moving body at two reception times of the set of reception times; determining a candidate estimated position vs. correlation value characteristic indicating a relationship between the candidate estimated position and the correlation value for the reception time set based on the frequency vs. correlation value characteristic for the reception time set and the estimated Doppler frequency change amount; determining an estimated location of the signal source based on the candidate estimated location versus correlation value characteristics for one or more sets of reception times; method.

12. A program for causing one or more computers to carry out the method according to claim 11.

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