Position estimation device, radio wave reception device, position estimation method, and position estimation program

Abstract

A position estimation device (10) comprises a correlation calculation unit (4), a direction estimation unit (5), and a position determination unit (8). The correlation calculation unit (4) calculates, as each element of a group of cross-correlation values, a cross-correlation value between signals corresponding to radio waves received by every two antenna beams within an antenna beam group consisting of a quantity of N antenna beams (where N is an integer of 3 or greater) that each receive radio waves transmitted from a radio wave source. The direction estimation unit (5) estimates the arrival direction of radio waves as an estimated arrival direction on the basis of each element of the group of cross-correlation values and an antenna gain pattern of each antenna beam of the antenna beam group. The position determination unit (8) determines an estimated position of a radio wave source on the basis of the estimated arrival direction.

Description

Position estimation device, radio wave receiving device, position estimation method, and position estimation program

[0001] This disclosure relates to a position estimation device, a radio wave receiving device, a position estimation method, and a position estimation program.

[0002] There is a radio wave receiving device that detects radio waves of a certain frequency and identifies the location of the radio station emitting those radio waves. As a specific example of a location estimation method in such a radio wave receiving device, Non-Patent Document 1 discloses a location estimation method in which three antenna beams are placed in close proximity and the location of the radio wave source is estimated based on the received power of the three antenna beams.

[0003] B. C. Fredrick, “Geolocation of source interference from a single satellite with multiple antennas,” Master's thesis, Naval Postgrad. School, Monterey, CA, 2014

[0004] The position estimation method disclosed in Non-Patent Document 1 has the problem that the accuracy of estimating the position of the radio wave source deteriorates when the incoming radio waves are weak.

[0005] The purpose of this disclosure is to provide a position estimation device that can estimate the position of a radio wave source with relatively high accuracy, even when the incoming radio waves are weak, by utilizing the cross-correlation value between it and other antenna beam signals.

[0006] The position estimation device according to this disclosure comprises: a correlation calculation unit that calculates the cross-correlation value between signals corresponding to radio waves received in each of two antenna beams of an antenna beam group consisting of N antenna beams, each of which receives radio waves transmitted from a radio wave source, when N is an integer of 3 or more, as each element of a cross-correlation value group; a direction estimation unit that estimates the direction of arrival of radio waves as an estimated direction of arrival based on each element of the cross-correlation value group and the antenna gain pattern of each antenna beam of the antenna beam group; and a position determination unit that determines the estimated position of the radio wave source based on the estimated direction of arrival.

[0007] According to the position estimation device of this disclosure, a correlation calculation unit calculates the cross-correlation values ​​between signals corresponding to radio waves received by two antenna beams each of three or more antenna beams, as elements of a cross-correlation value group. A direction estimation unit estimates the direction of arrival of the radio waves as an estimated direction of arrival, based on each element of the cross-correlation value group and the antenna gain pattern of each antenna beam in the antenna beam group. A position determination unit determines the estimated position of the radio wave source based on the estimated direction of arrival. Therefore, according to this disclosure, by utilizing the cross-correlation values ​​between other antenna beam signals, a position estimation device can be obtained that can estimate the position of a radio wave source with relatively high accuracy even if the incoming radio waves are weak.

[0008] A diagram showing an example configuration of the radio wave receiving device 20 according to Embodiment 1. A diagram showing an example hardware configuration of the position estimation device 10 according to Embodiment 1. A diagram showing an example hardware configuration of the position estimation device 10 according to Embodiment 1. A diagram showing an example configuration of the correlation calculation unit 4 according to Embodiment 1. A diagram explaining the operation of the beam pattern output unit 6 according to Embodiment 1. A diagram showing an example configuration of the direction estimation unit 5 according to Embodiment 1. A diagram explaining the operation of the direction estimation unit 5 according to Embodiment 1. A diagram explaining the operation of the position determination unit 8 according to Embodiment 1. A flowchart showing the operation of the position estimation device 10 according to Embodiment 1. A diagram explaining the effects of Embodiment 1, where (a) is a diagram showing the estimation result by the prior art, and (b) is a diagram showing the estimation result by the position estimation device 10. A diagram showing an example configuration of the radio wave receiving device 20 according to Embodiment 1. A diagram showing an example hardware configuration of the position estimation device 10 according to a modified example of Embodiment 1. A diagram showing an example configuration of the radio wave receiving device 20 according to Embodiment 3. A diagram explaining the operation of the demultiplexing unit 90 according to Embodiment 3. A diagram showing an example configuration of the antenna 1 according to Embodiment 4. A diagram showing an example configuration of the antenna 1 according to Embodiment 4.

[0009] In the description and drawings of the embodiments, the same elements and corresponding elements are denoted by the same reference numeral. The descriptions of elements denoted by the same reference numeral are omitted or simplified as appropriate. The arrows in the figures mainly indicate the flow of data or processing. Also, "part" may be read as "circuit," "device," "equipment," "process," "step," "procedure," "processing," or "circuitry" as appropriate. The functions of each part of each device may be realized by firmware, software, hardware, or a combination thereof.

[0010] Embodiment 1. This embodiment will be described in detail below with reference to the drawings.

[0011] ***Description of Configuration*** Figure 1 is a configuration diagram showing an example of a radio wave receiving device 20 according to Embodiment 1. The radio wave receiving device 20 is a technology that targets electromagnetic waves in general that propagate through space. Therefore, there are no particular restrictions on the frequency band that the radio wave receiving device 20 targets. In addition, the radio wave receiving device 20 may be configured with a receiving system suitable for the frequency band to be intercepted. However, the following description assumes a configuration that includes functions to be provided in various wireless devices that handle radio waves. The expression "radio waves" below may be read as other types of electromagnetic waves. As shown in Figure 1, the radio wave receiving device 20 includes antennas 1-1 to 1-3, receiving circuits 2-1 to 2-3, a position estimation device 10, and an output circuit 9. Figure 1 shows an example of the configuration of the radio wave receiving device 20 when the number of beams N is 3. The radio wave receiving device 20 includes N antennas 1, N receiving circuits 2, N distribution units 3, and N correlation calculation units 4. N is an integer of 3 or more. The notation "-i" (where i is a natural number) is used to distinguish between multiple elements when there are multiple elements of the same type, or when there are multiple equivalent elements. The position estimation device 10 comprises distribution units 3-1 to 3-3, correlation calculation units 4-1 to 4-3, direction estimation unit 5, beam pattern output unit 6, reference information setting unit 7, and position determination unit 8.

[0012] Antennas 1-1 through 1-3 each receive radio waves arriving from a radio wave source and output the radio waves from receiving circuit 2-1 to receiving circuit 2-3.

[0013] Receiving circuits 2-1 to 2-3 each perform frequency conversion, filtering, and analog-to-digital conversion on the radio waves acquired by antennas 1-1 to 1-3, thereby converting the radio waves acquired by antennas 1-1 to 1-3 into signals such as digital data of a predetermined frequency and bandwidth, or I / Q (In-Phase / Quadratur-Phase) data. Receiving circuits 2-1 to 2-3 each output the converted signals to the position estimation device 10, particularly from distribution unit 3-1 to distribution unit 3-3. In other words, the radio wave receiving device 20 has antenna circuits with N beam outputs.

[0014] Each of the distribution units 3-1 to 3-3 is implemented by the distribution circuit 31 shown in Figure 2, as a specific example. Figure 2 shows an example of the hardware configuration of the position estimation device 10. Each of the distribution units 3-1 to 3-3 is, as a specific example, an N-distributor (a 3-distributor in the configuration shown in Figure 1) of the antenna received signal digitized by the receiving circuit 2-1 to 2-3. Each of the distribution units 3-1 to 3-3 distributes or duplicates the signal into N parts and outputs each signal from the correlation calculation unit 4-1 to the correlation calculation unit 4-3.

[0015] The correlation calculation unit 4 calculates the cross-correlation value between signals corresponding to radio waves received in each of the two antenna beams of the antenna beam group, as each element of the cross-correlation value group. The antenna beam group consists of N antenna beams, each receiving radio waves transmitted from a radio wave source. The N antenna beams correspond to N antennas 1.

[0016] Each of the correlation calculation units 4-1 to 4-3 is implemented, as a specific example, by the correlation calculation circuit 32 shown in Figure 2. Each of the correlation calculation units 4-1 to 4-3 performs a complex inner product calculation between the received signals of each antenna 1, as a specific example. Each of the correlation calculation units 4-1 to 4-3 acquires received signals from the distribution unit 3-1 to the distribution unit 3-3. Each of the correlation calculation units 4-1 to 4-3 calculates the cross-correlation (complex inner product) of the received signals between different antennas 1, finds the average value of the cross-correlation, further calculates the square of the average value, and outputs the calculation result to the direction estimation unit 5.

[0017] The reference information setting unit 7 is implemented, in specific examples, by the reference information setting circuit 36 ​​shown in Figure 2. The reference information setting unit 7 sets the reference information and preconditions necessary to determine the position of the radio wave source, such as the position where the radio wave receiving device 20 is installed, the distance from the radio wave receiving device 20 to the target range for detecting radio waves, and the orientation of the radio wave receiving device 20. The reference information setting unit 7 outputs the necessary information to the beam pattern output unit 6 and the position determination unit 8, respectively.

[0018] The beam pattern output unit 6 is implemented, in specific examples, by the beam pattern output circuit 33 shown in Figure 2. Based on the information obtained from the reference information setting unit 7, the beam pattern output unit 6 outputs beam pattern (antenna gain pattern) information to the direction estimation unit 5. The antenna gain pattern is sometimes also referred to as the gain pattern.

[0019] The direction estimation unit 5 estimates the direction of arrival of radio waves as the estimated direction of arrival, based on each element of the cross-correlation value group and the antenna gain pattern of each antenna beam in the antenna beam group. As a specific example, the direction estimation unit 5 is implemented by the direction estimation circuit 34 shown in Figure 2. The direction estimation unit 5 obtains a total of six cross-correlation values ​​from the correlation calculation unit 4-1 to the correlation calculation unit 4-3. The direction estimation unit 5 also obtains three beam pattern data from the beam pattern output unit 6. The direction estimation unit 5 estimates the direction of arrival of the signal coming from the radio wave source from the six cross-correlation values ​​and the three beam pattern data, and outputs the estimated direction of arrival information to the position determination unit 8.

[0020] The position determination unit 8 determines the estimated position of the radio wave source based on the estimated direction of arrival. The position determination unit 8 is implemented by the position determination circuit 35 shown in Figure 2, as a specific example. The position determination unit 8 obtains the target range for detecting radio waves with each beam from the reference information setting unit 7 and obtains the direction of arrival information from the direction estimation unit 5. The target range is, as a specific example, information indicating latitude and longitude. The target range is the range in which the radio wave source exists. The target range generally includes the range in which radio waves can be received with a certain level of reception sensitivity or higher. As a specific example, the target range is the range in Figure 5 where the three antenna beams overlap with a reasonably high gain, that is, the range around the area connecting the peak gain directions of each antenna beam. The direction of arrival information is, as a specific example, information indicating elevation angle and azimuth angle. The position determination unit 8 determines the position of the radio wave source from the target range in which radio waves are detected by observation and the information indicating the direction of arrival of the radio waves, and outputs the determination result to the output circuit 9.

[0021] The direction estimation unit 5 estimates the estimated direction of arrival, and for two or more combinations of i, m, and n, it may determine an angular range as each element of the angular range group in which the absolute value of the difference between the value corresponding to the cross-correlation amplitude of antenna beam m with respect to antenna beam i and the value corresponding to the cross-correlation amplitude of antenna beam n with respect to antenna beam i, and the difference between the antenna gain of antenna beam m and the antenna gain of antenna beam n, is within the amplitude threshold. At this time, the position determination unit 8 determines the estimated position of the radio wave source based on each element of the angular range group. Note that antenna beam i, antenna beam m, and antenna beam n are each antenna beams included in the antenna beam group. Each of i, m, and n is an integer between 1 and N. It is assumed that i ≠ m, i ≠ n, and n ≠ m are satisfied. Antenna beam i corresponds to antenna 1-i. The value corresponding to the cross-correlation amplitude is, as a specific example, the value corresponding to the square of the cross-correlation amplitude.

[0022] The output circuit 9 outputs the estimated position of the radio wave source determined by the position estimation device 10. Specifically, based on the output of the position estimation device 10, the output circuit 9 provides the user with analysis results such as the position, direction, and distance of the radio wave source, as well as the intensity, frequency, and bandwidth of the radio waves. The output circuit 9 is implemented as a display device, such as a display, as a concrete example. The output circuit 9 may also output the analysis results to other devices.

[0023] In Figure 1, it is assumed that the distribution unit 3, correlation calculation unit 4, direction estimation unit 5, beam pattern output unit 6, reference information setting unit 7, and position determination unit 8 are each implemented by dedicated hardware as shown in Figure 2. That is, it is assumed that the position estimation device 10 is implemented by a distribution circuit 31, a correlation calculation circuit 32, a beam pattern output circuit 33, a direction estimation circuit 34, a position determination circuit 35, and a reference information setting circuit 36. Specific examples of each of the distribution circuit 31, correlation calculation circuit 32, beam pattern output circuit 33, direction estimation circuit 34, position determination circuit 35, and reference information setting circuit 36 ​​include single circuits, composite circuits, programmed processors, parallel programmed processors, ASICs (Application Specific Integrated Circuits), FPGAs (Field-Programmable Gate Arrays), or combinations thereof.

[0024] The components of the position estimation device 10 are not limited to those implemented by dedicated hardware; the position estimation device 10 may also be implemented by software, firmware, or a combination of software and firmware. The software or firmware is stored in the computer's memory as a position estimation program. A computer refers to hardware that executes programs. As a specific example, a device equipped with a processor 42 is considered a computer. The processor 42 may be 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 DSP (Digital Signal Processor), or a combination thereof.

[0025] Figure 3 shows an example of a computer hardware configuration when the position estimation device 10 is implemented by software or firmware. When the position estimation device 10 is implemented by software or firmware, a position estimation program is stored in memory 41 to cause the computer to execute the processing procedures in each of the distribution circuit 31, correlation calculation circuit 32, beam pattern output circuit 33, direction estimation circuit 34, position determination circuit 35, and reference information setting circuit 36. The computer's processor 42 then executes the position estimation program stored in memory 41. The position estimation program is a program that causes the computer to implement the functions of each part of the position estimation device 10.

[0026] Data used when executing the position estimation program, and data obtained by executing the position estimation program, are appropriately stored in the memory device. Each part of the position estimation device 10 makes appropriate use of the memory device. The memory device consists of, as a specific example, a main memory, an auxiliary memory, a register in the processor 42, and at least one of the cache memory in the processor 42. Note that the terms data and information may have the same meaning. The memory device may be independent of the computer. The functions of memory 41 may be realized by other memory devices.

[0027] The position estimation program may be recorded on a computer-readable non-volatile recording medium. Specific examples of non-volatile recording media include optical discs or flash memory. The position estimation program may also be provided as a program product.

[0028] Figure 2 shows a specific example in which each component of the position estimation device 10 is implemented by dedicated hardware. Figure 3 shows a specific example in which the position estimation device 10 is implemented by software or firmware. However, these are merely examples, and some components of the position estimation device 10 may be implemented by dedicated hardware, while the remaining components are implemented by software or firmware.

[0029] Figure 4 is a configuration diagram showing an example of a correlation calculation unit 4-1 according to Embodiment 1. Correlation calculation units 4-2 and 4-3 are the same as those of correlation calculation unit 4-1. Figure 4 shows an example of the configuration of the correlation calculation unit 4-1 when the correlation calculation is realized by complex inner product processing and averaging processing. The correlation calculation unit 4-1 shown in Figure 4 includes correlation processing circuits 51-1 and 51-2, averaging circuits 52-1 and 52-2, and amplitude extraction circuits 53-1 and 53-2.

[0030] ***Explanation of Operation*** The operation procedure of the position estimation device 10 corresponds to the position estimation method. The program that implements the operation of the position estimation device 10 corresponds to the position estimation program.

[0031] Next, an example of a series of operations starting from the correlation processing circuit 51-1 will be described. First, the correlation processing circuit 51-1 calculates a complex inner product value from the signals b1 and b2 output from the distributor 3-1 (corresponding to the antenna 1-1) and the distributor 3-2 (corresponding to the antenna 1-2), and outputs the calculation result. Here, the reason for calculating the complex inner product value is because it is assumed that the signals b1 and b2 are represented by complex numbers expressed by the in-phase component (I) and the quadrature component (Q). Note that for real number signals, the complex conjugate "*" does not need to be taken. The complex inner product values corresponding to the signals b1 and b2 are expressed as [Equation 1]. Here, m means the data of the m-th sample obtained by digital sampling. Similarly, the output of the correlation processing circuit 51-2, that is, the complex inner product values corresponding to the signals b1 and b3, are expressed as [Equation 2].

[0032]

[0033] Next, the averaging circuit 52-1 averages the output of the correlation processing circuit 51-1. As a specific example, the averaging circuit 52-1 calculates the average value of M samples as shown in [Equation 3], and outputs the calculation result to the amplitude extraction circuit 53-1.

[0034]

[0035] Next, the amplitude extraction circuit 53-1 calculates the amplitude squared value corresponding to the output of the averaging circuit 52-1 as shown in [Equation 4], and outputs the calculation result to the direction estimation unit

[0036]

[0037] The correlation operation unit 4 performs the above processing for the number of antennas provided in the radio wave receiving device 20. That is, in the configuration shown in FIG. 1, the correlation operation unit 4 performs the operation for three antennas, and sequentially outputs the six cross-correlation amplitude squared values β calculated as shown in [Equation 5] to the direction estimation unit 5. ｉｊ

[0038]

[0039] ​FIG. 5 is a beam layout diagram for explaining an example of the operation of the beam pattern output unit 6 according to Embodiment 1. FIG. 5 shows an example in which the peak directions (directions of maximum gain) of three beams (Beam1, Beam2, and Beam3 in FIG. 5) are arranged close to each other. Each line in FIG. 5 is a contour line showing the amount of gain reduction with respect to the peak gain in 1 dB increments. Near the center of the beam layout diagram shown in FIG. 5, the three beam patterns intersect at a point where the gain reduction amount with respect to the peak is decreased by a certain value between -4 dB and -3 dB. FIG. 5 shows a two-dimensional gain pattern with respect to the horizontal direction (Azimuth) and the vertical direction (Elevation). The beam pattern output unit 6 reads out measured values or calculated values stored in advance as two-dimensional data as information within the necessary range of this two-dimensional gain pattern, and outputs the read values to the direction estimation unit 5. Note that the two-dimensional gain pattern is an antenna gain pattern expressed in two dimensions. Calculation and interpolation may be performed by on-board processing on the satellite.

[0040] FIG. 6 is a configuration diagram showing an example of the direction estimation unit 5. FIG. 6 shows a configuration example of the direction estimation unit 5 in the case where direction estimation is realized by a prediction result indicating that a signal is arriving from within a certain range. The direction estimation unit 5 includes a prediction range calculation circuit 61 and an angle determination circuit 62.

[0041] The prediction range calculation circuit 61 calculates ranges (Az, EL) that satisfy [Equation 6] to [Equation 8] from the two-dimensional gain pattern G ｉ (Az, El) and the dB value of β ｉｊ (the value obtained by removing 10 * log10 from β ｉｊ ), which is P ｉｊ , and outputs the calculation results to the angle determination circuit 62. Note that each of (P １３ - P ２３ ), (P ２１ - P ３１ ), and (P １２ - P ３２ ) corresponds to the difference between the value corresponding to the mutual correlation amplitude of the antenna beam m with respect to the antenna beam i and the value corresponding to the mutual correlation amplitude of the antenna beam n with respect to the antenna beam i. (G １ (Az, El) - G２ (Az, El)) and (G ２ (Az, El)-G ３ (Az, El)) and (G １ (Az, El)-G ３ Each of (Az, El) represents the difference between the antenna gain of antenna beam m and the antenna gain of antenna beam n.

[0042]

[0043] Note that ΔP [dB] is a margin that takes into account the measurement error (calculation error) of cross-correlation. ΔP corresponds to the amplitude threshold. ｉｊ This includes the effective radiated power (EIRP) of the radio source, various losses up to the device, and the antenna gain. Here, the former two can be considered essentially identical between beams. Therefore, taking the ratio of the received power values ​​of the two beams (the difference in dB values ​​in the above equations) satisfies the relationships from [Equation 6] to [Equation 8], respectively.

[0044] Figure 7 illustrates the results obtained by calculations using [Equation 6] to [Equation 8]. Figure 7 shows the results of determining the angular range for three sets of i, m, and n combinations. Each range shown in Figure 7 corresponds to each element of the angular range group. Figure 7 shows the range where the signal from the radio source is predicted to arrive, based on each of [Equation 6] to [Equation 8]. In Figure 7, ΔP is set to 0.5 dB. As shown in Figure 7, the solutions that satisfy [Equation 6] to [Equation 8] represent a band-shaped range with a width dependent on the value of ΔP. The prediction range calculation circuit 61 outputs these three results to the angle determination circuit 62.

[0045] The angle determination circuit 62 determines the direction of arrival of the signal from the radio wave source based on the output of the prediction range calculation circuit 61. Specifically, as shown in Figure 7, the angle determination circuit 62 outputs the angle range where the three prediction ranges intersect as the angle determination result to the position determination unit 8.

[0046] The position determination unit 8 determines the position of the radio wave source based on the output from the reference information setting unit 7 and the direction estimation unit 5. For example, if the radio wave receiving device 20 is mounted on a satellite, the position determination unit 8 determines the position of the radio wave source from the range (latitude and longitude) in which radio waves are detected by each beam, the satellite's orbital information, and the angular range information from the direction estimation unit 5. For example, the output shown in Figure 8 is obtained as the result of determining the position of the radio wave source. In Figure 8, the "×" mark represents the actual position of the radio wave source (True value), and the "◇" mark represents the estimation result (Estimation). The data output by the position determination unit 8 may be user-friendly display information as shown in Figure 8, or it may be specific position coordinate data.

[0047] Next, the operation of the position estimation device 10 shown in Figure 1 will be explained. Figure 9 is a flowchart showing an example of a position estimation method, which is the processing procedure of the position estimation device 10.

[0048] (Step ST1) The reference information setting unit 7 stores various setting information such as the position, altitude, observation range, and beam arrangement of the radio wave receiving device 20, and outputs the necessary information to the beam pattern output unit 6 and the position determination unit 8.

[0049] (Step ST2) Each of the distribution units 3-1 to 3-3 divides the input signal into three parts and outputs them from the correlation calculation unit 4-1 to the correlation calculation unit 4-3.

[0050] (Step ST3) Correlation calculation units 4-1 to 4-3 calculate the squared value of the cross-correlation amplitude based on [Equation 5] and output the calculation result to the direction estimation unit 5.

[0051] (Step ST4) The beam pattern output unit 6 outputs the gain pattern of the observation range to the direction estimation unit 5 based on the settings output from the reference information setting unit 7.

[0052] (Step ST5) The direction estimation unit 5 uses the outputs from the correlation calculation unit 4-1 to the correlation calculation unit 4-3 and the output of the beam pattern output unit 6 to estimate the arrival angle range of the radio wave source based on [Equation 6] to [Equation 8]. The direction estimation unit 5 outputs the estimated angle range to the position determination unit 8.

[0053] (Step ST6) The position determination unit 8 estimates the position of the radio wave source based on the output from the reference information setting unit 7 and the direction estimation unit 5.

[0054] Figure 10 shows an example of the results of estimating the position of a radio wave source under the same conditions. Figure 10(a) shows the estimation result using the conventional technology. Figure 10(b) shows the estimation result using the position estimation device 10 according to this embodiment. The conditions in question are an environment where the signal level is weak, that is, an environment with a low SNR (Signal to Noise Ratio). As shown in Figure 10, although the estimation result using the conventional technology deviates from the true value, the estimation result using the position estimation device 10 according to this embodiment is in close agreement with the true value. Therefore, the effectiveness of this embodiment compared to the conventional technology has been confirmed.

[0055] Figure 1 shows a configuration in which each signal is divided into three parts by distribution unit 3-3 from distribution unit 3-1, and three correlation calculation units 4-1 are connected to correlation calculation units 4-3. On the other hand, as shown in Figure 11, the position estimation device 10 has a correlation calculation unit 11 that integrates the distribution unit 3 and the correlation calculation unit 4, and the correlation calculation unit 11 may obtain processing and output equivalent to the processing and output of the distribution unit 3 and the correlation calculation unit 4. The processing of the distribution unit 3 and the correlation calculation unit 4 can be achieved by digital signal processing, and there is a degree of freedom in the configuration for realizing the functions of the distribution unit 3 and the correlation calculation unit 4.

[0056] ***Explanation of the Effects of Embodiment 1*** In Embodiment 1, the position estimation device 10 includes distribution units 3-1 to 3-3, correlation calculation units 4-1 to 4-3, direction estimation unit 5, beam pattern output unit 6, reference information setting unit 7, and position determination unit 8. Distribution units 3-1 to 3-3 each distribute the outputs from antennas 1-1 to 1-3 and receiving circuit 2-1 to 2-3, which form three antenna beams. Each of the correlation calculation units 4-1 to 4-3 calculates the cross-correlation value between the antenna beam signals and outputs the squared value of the amplitude, which is the calculation result. The direction estimation unit 5 estimates the direction of arrival of the signal from the radio wave source based on the squared value of the cross-correlation amplitude and the antenna gain pattern of each antenna beam. The beam pattern output unit 6 outputs the antenna gain pattern of each antenna beam. The reference information setting unit 7 outputs initial settings such as the observation range. The position determination unit 8 estimates the position of the radio wave source based on the outputs from the direction estimation unit 5 and the reference information setting unit 7. Therefore, the position estimation device 10 can estimate the position of the radio wave source with relatively high accuracy by obtaining only three beam outputs.

[0057] ***Other Configurations*** <Modification 1> Figure 12 shows an example of the hardware configuration of the position estimation device 10 according to this modification. The position estimation device 10 includes a processing circuit 48 instead of a processor 42, or a memory 41 and a processor 42. The processing circuit 48 is hardware that realizes at least a part of each part of the position estimation device 10. The processing circuit 48 may be dedicated hardware, or it may be a processor that executes a program stored in the memory 41.

[0058] If the processing circuit 48 is dedicated hardware, specific examples of the processing circuit 48 include 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. The position estimation device 10 may also include multiple processing circuits that substitute for the processing circuit 48. The multiple processing circuits share the role of the processing circuit 48.

[0059] In the position estimation device 10, some functions may be implemented by dedicated hardware, while the remaining functions may be implemented by software or firmware.

[0060] The processing circuit 48 can be implemented, in specific examples, by hardware, software, firmware, or a combination thereof. The memory 41, processor 42, and processing circuit 48 are collectively referred to as the "processing circuitry." In other words, the functions of each functional component of the position estimation device 10 are implemented by the processing circuitry. The position estimation device 10 according to other embodiments may also have a configuration similar to this modified example.

[0061] Embodiment 2. The following describes the main differences from the embodiment described above.

[0062] ***Description of Configuration*** The configuration of the radio wave receiving device 20 according to this embodiment is the same as the configuration of the radio wave receiving device 20 according to Embodiment 1. The position estimation device 10 according to Embodiment 1 estimates a certain range as a direction estimation value. On the other hand, the position estimation device 10 according to this embodiment determines the direction estimation value with pinpoint accuracy.

[0063] In this embodiment, the direction estimation unit 5 estimates the estimated direction of arrival and may determine, for two or more combinations of i, m, and n, the angle that minimizes the difference between the value corresponding to the cross-correlation amplitude of antenna beam m with respect to antenna beam i and the value corresponding to the cross-correlation amplitude of antenna beam n with respect to antenna beam i, and the difference between the antenna gain of antenna beam m and the antenna gain of antenna beam n, as each element of the minimum angle group. In this case, the position determination unit 8 in this embodiment determines the estimated position of the radio wave source based on each element of the minimum angle group.

[0064] Specifically, the direction estimation unit 5 first determines (Az1, El1), (Az2, El2), and (Az3, El3) as angles that satisfy each of [Equation 9] to [Equation 11]. Finding angles that satisfy each of [Equation 9] to [Equation 11] is equivalent to finding the angle that minimizes the difference between the square of the cross-correlation amplitude and the beam gain. The angles that satisfy each of [Equation 9] to [Equation 11] are elements of the minimum angle group.

[0065]

[0066] Next, the direction estimation unit 5 finds the centroid of the three solutions (three points) corresponding to [Equation 9] to [Equation 11], as shown in [Equation 12] and [Equation 13]. The direction estimation unit 5 outputs the found centroid to the position determination unit 8 as the direction of arrival of the signal from the radio wave source (Az_ans, El_ans). Here, since a triangle is formed by the three points, the centroid of the three points is equivalent to the average of the three points.

[0067]

[0068] The position determination unit 8 in this embodiment estimates the position of the radio wave source using the centroids of three points corresponding to [Equation 9] to [Equation 11] as output from the direction estimation unit 5.

[0069] ***Explanation of the effects of Embodiment 2*** In Embodiment 2, the direction estimation unit 5 precisely estimates the direction of arrival of the radio wave source by searching for the smallest point in a simple manner. Therefore, according to Embodiment 2, the position of the radio wave source can be estimated faster and more easily compared to Embodiment 1.

[0070] Embodiment 3. The following describes the differences from the embodiments described above, mainly with reference to the drawings. Embodiments 1 and 2 perform correlation calculations on the received time-domain signals. Embodiment 3, on the other hand, describes an embodiment that uses frequency-domain signals.

[0071] ***Configuration Description*** Figure 13 is a configuration diagram showing an example of a radio wave receiving device 20 including a position estimation device 10 according to Embodiment 3. As shown in Figure 13, the position estimation device 10 newly includes FFT units 80-1 to 80-3 and demultiplexing units 90-1 to 90-3. FFT is an abbreviation for Fast Fourier Transform.

[0072] FFT units 80-1 to 80-3 each perform a Fourier transform on the digital signals output from receiving circuits 2-1 and 2-3, respectively, thereby converting the digital signals into frequency domain signals. FFT units 80-1 to 80-3 each output the converted signals to demultiplexers 90-1 and 90-3, respectively.

[0073] The demultiplexing units 90-1 to 90-3 each extract a signal component with a frequency bandwidth BW, including the signal component from the radio wave source, from the frequency domain signal output from the FFT unit 80-1 to 80-3. The demultiplexing units 90-1 to 90-3 each output the signal after bandwidth extraction from the distribution unit 3-1 to the distribution unit 3-3.

[0074] An example of the operation of the demultiplexing units 90-1 to 90-3 will be explained using Figure 14. Figure 14 shows the frequency spectrum after the Fourier transform. In Figure 14, the horizontal axis represents frequency and the vertical axis represents amplitude. When a signal is received from a radio source, a signal component is superimposed on the noise component. Here, the signal can be detected by observing the frequency spectrum. The FFT unit 80 extracts the portion corresponding to the frequency bandwidth BW, which includes the signal band, from the frequency spectrum. By the FFT unit 80 extracting the portion corresponding to the frequency bandwidth BW, the data from which unnecessary noise components have been removed can be used in subsequent processing.

[0075] The correlation calculation unit 4 in this embodiment calculates the cross-correlation value between signals corresponding to radio waves received in each of the two antenna beams of the antenna beam group, which corresponds to the frequency bandwidth BW that includes the signal band corresponding to the signal component of the radio wave transmitted from the radio wave source, among the signals corresponding to the radio waves received in each of the two antenna beams.

[0076] ***Explanation of the effects of Embodiment 3*** In Embodiment 3, by adding an FFT unit 80-3 from the FFT unit 80-1 and a demultiplexing unit 90-3 from the demultiplexing unit 90-1, signal data with unwanted noise components removed is extracted. Therefore, according to Embodiment 3, compared with Embodiments 1 and 2, robust and stable processing can be performed with respect to noise components.

[0077] Embodiment 4. The following will mainly describe the differences from the embodiments described above, with reference to the drawings. Embodiment 4 describes a specific example of the configuration of the antenna 1 for forming N beams.

[0078] ***Configuration Description*** Figure 15 shows an example of the configuration of antenna 1 when the number of beams N is 3, illustrating a reflector antenna system in which reflectors 101 are installed in front of antennas 1-1 to 1-3. The reflector 101 is also called a reflector. In Figure 15, the antenna circuit comprises N primary radiators and one reflector 101. With the antenna 1 shown in Figure 15, by adjusting the three-dimensional positions of antennas 1-1 to 1-3, one reflector 101 can be shared, reducing the overall size of antenna 1, while improving angular resolution through high gain.

[0079] Figure 16 shows an example of a direct array configuration using antennas 1-1 to 1-K, where K is an integer greater than or equal to 2. In Figure 16, the antenna circuit comprises multiple antenna elements and a beamforming circuit 111. Figure 16 shows that by using an array antenna consisting of K antennas 1-1 to 1-K, and digitally combining the received signals from each antenna 1 in the beamforming circuit 111, it is possible to realize a flexible array antenna through digital beamforming, where the total number of antennas 1 is any number, the directional direction of each antenna 1 is any direction, and the sidelobe level is any value. Therefore, with the array antenna shown in Figure 16, it is possible to appropriately adjust the beam arrangement, number of beams, beam pattern, etc., to optimize them according to the environment. Consequently, the array antenna shown in Figure 16 can improve the operational convenience of the array antenna. It is also possible to further install a reflector 101 in front of antennas 1-1 to 1-K to create an array-fed reflector system, or an imaging reflector system.

[0080] ***Explanation of the effects of Embodiment 4*** By equipping the radio wave receiving device 20 with the antenna 1 according to this embodiment, higher resolution or improved flexibility can be achieved.

[0081] ***Other Embodiments*** The embodiments described above can be freely combined, any component of each embodiment can be modified, or any component can be omitted in each embodiment. Furthermore, the embodiments are not limited to those shown in embodiments 1 to 4, and various modifications can be made as needed. The procedures described using flowcharts, etc., may be modified as appropriate.

[0082] The various aspects of this disclosure are summarized below as an appendix.

[0083] (Note 1) A position estimation device comprising: a correlation calculation unit that calculates the cross-correlation value between signals corresponding to radio waves received in each of two antenna beams of an antenna beam group consisting of N antenna beams, each of which receives radio waves transmitted from a radio wave source, as each element of a cross-correlation value group when N is an integer of 3 or more; a direction estimation unit that estimates the direction of arrival of radio waves as an estimated direction of arrival based on each element of the cross-correlation value group and the antenna gain pattern of each antenna beam of the antenna beam group; and a position determination unit that determines the estimated position of the radio wave source based on the estimated direction of arrival.

[0084] (Note 2) The position estimation device according to Note 1, wherein each of i, m, and n is an integer between 1 and N, and i≠m, i≠n, and n≠m are satisfied, the direction estimation unit estimates the estimated direction of arrival, and for two or more combinations of i, m, and n, the angle range in which the absolute value of the difference between the value corresponding to the cross-correlation amplitude of antenna beam m of the antenna beam group with respect to antenna beam i of the antenna beam group and the value corresponding to the cross-correlation amplitude of antenna beam n of the antenna beam group with respect to antenna beam i, and the difference between the antenna gain of antenna beam m and the antenna gain of antenna beam n, is within the amplitude threshold, is determined as each element of the angle range group, and the position determination unit determines the estimated position of the radio wave source based on each element of the angle range group.

[0085] (Note 3) The position estimation device according to Note 1, wherein each of i, m, and n is an integer between 1 and N, and i≠m, i≠n, and n≠m are satisfied, the direction estimation unit estimates the estimated direction of arrival, and for two or more combinations of i, m, and n, it finds the angle that minimizes the difference between the value corresponding to the cross-correlation amplitude of antenna beam m of the antenna beam group with respect to antenna beam i of the antenna beam group and the value corresponding to the cross-correlation amplitude of antenna beam n of the antenna beam group with respect to antenna beam i, and the difference between the antenna gain of antenna beam m and the antenna gain of antenna beam n, and the position determination unit determines the estimated position of the radio wave source based on the elements of the minimum angle group.

[0086] (Note 4) The position estimation device according to any one of Notes 1 to 3, wherein the correlation calculation unit calculates the cross-correlation value between signals corresponding to radio waves received by each of the two antenna beams of the antenna beam group, and the cross-correlation value between signals corresponding to a frequency bandwidth that includes the signal band corresponding to the signal component of the signal corresponding to the radio wave transmitted from the radio wave source, among the signals corresponding to the radio waves received by each of the two antenna beams.

[0087] (Note 5) The position estimation device according to any one of Notes 1 to 4, wherein each antenna beam in the antenna beam group corresponds to an antenna equipped on an artificial satellite.

[0088] (Appendix 6) A radio wave receiving device comprising: a position estimation device described in any one of Appendix 1 to 5; an antenna circuit having N beam outputs; and an output circuit that outputs the estimated position of the radio wave source determined by the position estimation device.

[0089] (Note 7) The antenna circuit is a radio wave receiving device as described in Note 6, comprising N primary radiators and one reflector.

[0090] (Note 8) The antenna circuit is the radio wave receiving device described in Note 6, comprising a plurality of antenna elements and a beamforming circuit.

[0091] 1 Antenna, 2 Receiving circuit, 3 Distribution unit, 4 Correlation calculation unit, 5 Direction estimation unit, 6 Beam pattern output unit, 7 Reference information setting unit, 8 Position determination unit, 9 Output circuit, 10 Position estimation device, 11 Correlation calculation unit, 20 Radio wave receiving device, 31 Distribution circuit, 32 Correlation calculation circuit, 33 Beam pattern output circuit, 34 Direction estimation circuit, 35 Position determination circuit, 36 Reference information setting circuit, 41 Memory, 42 Processor, 48 Processing circuit, 51 Correlation processing circuit, 52 Averaging circuit, 53 Amplitude extraction circuit, 61 Prediction range calculation circuit, 62 Angle determination circuit, 80 FFT unit, 90 Demultiplexing unit, 101 Reflector, 111 Beamforming circuit.

Claims

1. A position estimation device comprising: a correlation calculation unit that calculates the cross-correlation value between signals corresponding to radio waves received in each of two antenna beams of an antenna beam group consisting of N antenna beams, each of which receives radio waves transmitted from a radio wave source, when N is an integer of 3 or more, as each element of a cross-correlation value group; a direction estimation unit that estimates the direction of arrival of radio waves as an estimated direction of arrival based on each element of the cross-correlation value group and the antenna gain pattern of each antenna beam of the antenna beam group; and a position determination unit that determines the estimated position of the radio wave source based on the estimated direction of arrival.

2. The position estimation device according to claim 1, wherein each of i, m, and n is an integer between 1 and N, and the conditions i≠m, i≠n, and n≠m are satisfied, the direction estimation unit estimates the estimated direction of arrival, and for two or more combinations of i, m, and n, it determines an angular range as each element of the angular range group in which the absolute value of the difference between the value corresponding to the cross-correlation amplitude of antenna beam m of the antenna beam group with respect to antenna beam i of the antenna beam group and the value corresponding to the cross-correlation amplitude of antenna beam n of the antenna beam group with respect to antenna beam i, and the difference between the antenna gain of antenna beam m and the antenna gain of antenna beam n, is within the amplitude threshold, and the position determination unit determines the estimated position of the radio wave source based on each element of the angular range group.

3. The position estimation device according to claim 1, wherein each of i, m, and n is an integer between 1 and N, and the conditions i≠m, i≠n, and n≠m are satisfied, the direction estimation unit estimates the estimated direction of arrival, and for two or more combinations of i, m, and n, it finds the angle that minimizes the difference between the value corresponding to the cross-correlation amplitude of antenna beam m of the antenna beam group with respect to antenna beam i of the antenna beam group and the value corresponding to the cross-correlation amplitude of antenna beam n of the antenna beam group with respect to antenna beam i, and the difference between the antenna gain of antenna beam m and the antenna gain of antenna beam n, and the position determination unit determines the estimated position of the radio wave source based on the elements of the minimum angle group.

4. The position estimation device according to any one of claims 1 to 3, wherein the correlation calculation unit calculates, as a cross-correlation value between signals corresponding to radio waves received by each of the two antenna beams of the antenna beam group, the cross-correlation value between signals corresponding to a frequency bandwidth that includes the signal band corresponding to the signal component of the signal corresponding to the radio wave transmitted from the radio wave source, among the signals corresponding to the radio waves received by each of the two antenna beams.

5. The position estimation device according to any one of claims 1 to 4, wherein each antenna beam in the antenna beam group corresponds to an antenna equipped on an artificial satellite.

6. A radio wave receiving device comprising: a position estimation device according to any one of claims 1 to 5; an antenna circuit having N beam outputs; and an output circuit that outputs the estimated position of the radio wave source determined by the position estimation device.

7. The radio wave receiving device according to claim 6, wherein the antenna circuit comprises N primary radiators and one reflector.

8. The radio wave receiving device according to claim 6, wherein the antenna circuit comprises a plurality of antenna elements and a beamforming circuit.

9. A correlation calculation unit in which, when N is an integer of 3 or more, the computer calculates the cross-correlation values ​​between signals corresponding to radio waves received in each of two antenna beams of an antenna beam group consisting of N antenna beams, each of which receives radio waves transmitted from a radio wave source, as each element of a cross-correlation value group; the computer estimates the direction of arrival of the radio waves as an estimated direction of arrival based on each element of the cross-correlation value group and the antenna gain pattern of each antenna beam of the antenna beam group; and the computer determines the estimated position of the radio wave source based on the estimated direction of arrival.

10. A position estimation program that causes a computer-based position estimation device to execute the following: a correlation calculation process in which, when N is an integer of 3 or more, the cross-correlation values ​​between signals corresponding to radio waves received in each of the two antenna beams of an antenna beam group consisting of N antenna beams, each receiving radio waves transmitted from a radio wave source, are calculated as elements of a cross-correlation value group; a direction estimation process in which the direction of arrival of radio waves is estimated as the estimated direction of arrival based on each element of the cross-correlation value group and the antenna gain pattern of each antenna beam of the antenna beam group; and a position determination process in which the estimated position of the radio wave source is determined based on the estimated direction of arrival.

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