JP6569612B2 - Radio source location estimation device - Google Patents

Description

  The present invention relates to a position estimation device for a radio wave source that estimates the position of a radio wave source such as a terrestrial transmitting station that is transmitting radio waves by receiving a signal relayed by a satellite.

  Information on time difference of arrival (TDOA), which is the difference between the time when radio waves transmitted from radio sources with unknown positions arrive at two satellites, and the frequency difference between radio waves reaching two satellites There is a technique for estimating the position of the radio wave source using (FDOA: Frequency Difference of Arrival) information (Non-Patent Document 1).

  Two signals respectively relayed by two satellites are multiplied by assuming TDOA (represented by variable τ) and FDOA (represented by variable f), and time integration is obtained. A value obtained by time integration is called a two-dimensional correlation value. The two-dimensional correlation value takes a sharp peak when the assumed (τ, f) matches the actual one. By changing τ and f, the two-dimensional correlation value becomes a peak (τ, f). When (τ, f) at which the two-dimensional correlation value reaches a peak is obtained, the position and speed of the two satellites obtained from the satellite orbit information are used to determine 2 regarding the positional relationship between the two satellites and the radio wave source. One relational expression is determined. By adding the constraint that the radio wave source is on the surface of the earth, the position of the radio wave source can be estimated from τ and f.

  In order to improve the position detection accuracy of the radio wave source, there is a method of using a reference station whose position is known. A two-dimensional correlation value of the signal passing through the two satellites from the reference station is found (τ, f), and the position of the target station is estimated based on the position of the reference station.

D. P. Haworth, et.al, “Interference Localization For Eutelsat Satellites -The First European Transmitter Location System,” International Journal of Satellite Communications, Vol. 15, pp.155-183, 1997

  If the position of the target station can be assumed to some extent from analogy based on past estimation results, etc., and prior information, etc., and there is almost no offset deviation (steady deviation) in the time or frequency of the received signal, two-dimensional The peak position (τ, f) of the correlation value can be assumed from the estimated position of the target station and the orbit information of the satellite. If it can be assumed, the correlation calculation of the two-dimensional correlation value can narrow the range in which (τ, f) is searched, and the calculation amount can also be reduced.

  However, in reality, there is an error in the orbit (position, velocity) of the communication satellite between the actual position and the predicted orbit. It is difficult to estimate this error. There is also a frequency shift in the oscillators of communication equipment and communication satellites. For example, in a communication satellite, the frequency of the received uplink signal and the frequency of the transmitted downlink signal are changed by a fixed frequency. If there is a frequency shift in the oscillator of the communication satellite, the magnitude of this fixed frequency shifts and an offset shift also appears in the FDOA. Further, a frequency error (for example, about 1 kHz) due to a communication satellite device may be added. Therefore, it is necessary to widen the range of (τ, f) to be searched for.

  For example, the accuracy of TDOA requires an accuracy of approximately several tens of microseconds to several thousand microseconds in order to obtain an accuracy of several kilometers to several hundred kilometers. Further, the accuracy of FDOA generally requires an accuracy of several mHz to several 100 mHz in order to obtain an accuracy of several km to several hundred km. In the search, a time shift is expected to be several milliseconds to several tens of milliseconds and a frequency shift is expected to be several to several thousand Hz, so that the search range of TDOA and FDOA is broadly determined. Therefore, when positioning is repeated, a wide range is repeatedly searched, and there is a problem that the calculation time becomes long.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to reduce the amount of calculation compared to the conventional method when repeatedly estimating the position of a radio wave source.

  In the position estimation device according to the present invention, the first received signal received by the first observation station after the radio wave radiated from the radio wave source having an unknown position is relayed by the first satellite, and the radio wave radiated from the radio wave source is received. The second received signal relayed by the second satellite different from the first satellite and received by the second observation station has a determined time difference with respect to the first received signal and takes a complex conjugate. A correlation value calculation unit that calculates a two-dimensional correlation value obtained by integrating a value obtained by multiplying the value and a complex number having an absolute value of 1 rotating at a determined frequency for a determined time; Furthermore, it has a peak detection unit for detecting the time difference and frequency at which the two-dimensional correlation value takes the maximum peak by changing the time difference and the frequency, and a search range determination unit for determining a search range that is a range for changing the time difference and the frequency. . Further, a search solution storage unit that stores a time difference and frequency at which the two-dimensional correlation value takes the maximum peak, a time difference and frequency at which the two-dimensional correlation value detected by the peak detection unit takes a maximum peak, and the first satellite And a positioning unit that determines the position of the radio wave source using the position and speed of the second satellite and the position and speed of the second satellite. The search range determination unit determines the search range based on the time difference and frequency at the latest positioning and the elapsed time from the latest positioning.

  According to the present invention, when the estimation of the position of the radio wave source is repeated, the amount of calculation can be reduced as compared with the prior art.

It is a conceptual diagram explaining the process which estimates the position of the radio wave source whose position is unknown. It is a conceptual diagram explaining the process which estimates the position of the radio wave source (target station) whose position in the case of using a reference station is unknown. It is a figure explaining the process which correct | amends the time and frequency offset shift | offset | difference using a reference station. It is a schematic diagram explaining the structure of the position estimation apparatus which concerns on Embodiment 1 of this invention. 6 is a diagram for explaining a first search range in the position estimation apparatus according to Embodiment 1. FIG. 6 is a diagram for explaining a search range after the second time in the position estimation device according to Embodiment 1. FIG.

Embodiment 1 FIG.
FIG. 1 is a conceptual diagram illustrating processing for estimating the position of a radio wave source whose position is unknown. FIG. 1 is based on the method disclosed in Non-Patent Document 1. In the example of FIG. 1, a radio wave is transmitted from a radio wave source 70 whose position is unknown. A main lobe radio wave 81 radiated from the radio wave source 70 is transmitted to the satellite (# 1) 71. At the same time, the radio wave source 70 emits side lobe radio waves 82. The satellite (# 1) 71 relays the radio wave 81 and transmits the radio wave 83. The radio wave 83 from the satellite (# 1) 71 is received by the antenna (# 1) 72 of the monitoring station. The antenna (# 1) 72 generates a reception signal 91 from the radio wave 83. The sidelobe radio wave 82 radiated from the radio wave source 70 is relayed by the satellite (# 2) 73 and received as the radio wave 84 by the antenna (# 2) 74 of the monitoring station. The antenna (# 2) 73 generates a reception signal 92 from the radio wave 84.

  The antenna (# 1) 72 and the antenna (# 2) 74 may be installed in different monitoring stations. The monitoring station where the antenna (# 1) 72 is installed is the first monitoring station, and the monitoring station where the antenna (# 2) 74 is installed is the second monitoring station. The received signal 91 is the first received signal that is relayed by the satellite (# 1) 71 that is the first satellite and received by the first observation station. The received signal 92 is the second received signal that is relayed by the satellite (# 2) 73 that is the second satellite and received by the second observation station. When the antenna (# 1) 72 and the antenna (# 2) 74 are installed in the same monitoring station, the monitoring station is the first monitoring station and the second monitoring station.

  Received signals 91 and 92 are input to radio wave source position estimating apparatus 50. The position estimation apparatus 50 estimates TDOA and FDOA when the satellite (# 1) 71 and the satellite (# 2) 73 are received. Estimating the position of the intersection of the equal TDOA line 61 that is the intersection of the surface with the estimated TDOA constant and the ground surface and the equal FDOA line 62 that is the intersection of the surface with the estimated FDOA constant and the ground surface The device 50 estimates the position of the radio wave source 70.

  The path until the radio wave 81 radiated from the radio wave source 70 whose position is unknown is received as the radio wave 83 by the antenna (# 1) 72 and the radio wave 82 is received as the radio wave 84 by the antenna (# 2) 74. In the route, the route after satellite (# 1) 71 and the route after satellite (# 2) 72 are known. In order to determine the position of the radio wave source 70, a time difference (TDOA) when radio waves reach the satellite (# 1) 71 and the satellite (# 2) 73 and a frequency difference (FDOA) between the received radio waves 81 and 82 are obtained. The frequency difference is that the satellite (# 1) 71 and the satellite (# 2) 73 move at different velocity vectors, and therefore the change in the reception frequency due to the Doppler effect is that the satellite (# 1) 71 and the satellite (# 2) 73 It is caused by different.

  First, a method for estimating the position of the radio wave source 70 from the arrival time difference (TDOA) and the frequency difference (FDOA) will be described.

Define the following variables:
p _o : the position of the radio wave source 70. It is based on a three-dimensional coordinate system with the center of the earth as the origin.
p _s1 : The position of the satellite (# 1) 71.
p _s2 : The position of the satellite (# 2) 73.
c: Speed of light.
τ ₁ : Time until the radio wave 81 is emitted from the radio wave source 70 and reaches the satellite (# 1) 71.
τ ₂ : Time until the radio wave 82 is emitted from the radio wave source 70 and reaches the satellite (# 2) 73.
v _s1 : The velocity vector of the satellite (# 1) 71.
v _s2 : The velocity vector of the satellite (# 2) 73.
f _d1 : Doppler frequency shift amount generated by the speed of the satellite (# 1) 71.
f _d2 : Doppler frequency shift amount generated by the speed of the satellite (# 2) 73.
fc: the frequency of the carrier wave of the radio wave from the radio wave source 70.
λ: the wavelength of the carrier wave of the radio wave from the radio wave source 70. λ = c / fc

  The time until the radio wave from the radio wave source 70 reaches the satellite (# 1) 71 or the satellite (# 2) 73 can be calculated as follows.

  When the satellite (# 1) 71 and the satellite (# 2) 73 receive the radio wave from the radio wave source 70, the Doppler frequency shift amount generated by the movement of the satellite can be calculated as follows.

  The arrival time difference TDOA between the satellite (# 1) 71 and the satellite (# 2) 73 can be calculated by the following equation (5). The frequency difference FDOA, which is the difference in the Doppler frequency shift amount, can be calculated by the following equation (6).

  Since it is assumed that the radio wave source 70 whose position is unknown exists on the ground surface, the following holds.

ここで、Ｒｅは地球の中心からの地表面までの距離である。Ｒｅは一定値としてもよい。より厳密に計算するには、地図データを参照して、電波源７０の位置に応じてＲｅを決めてもよい。

Here, Re is the distance from the center of the earth to the ground surface. Re may be a constant value. In order to calculate more strictly, Re may be determined according to the position of the radio wave source 70 with reference to the map data.

Given TDOA and FDOA, by the equation (5) to (7), it is possible to determine the position _{p o} radio sources 70. Since the satellite position and velocity (# 1) 71 and the satellite (# 2) 73 is available as a satellite orbit information, the unknown variables of the coordinate p _o (x, y, z) of This is because there are three and the number of equations is three.

  From the received signal 91 by the radio wave 83 from the satellite (# 1) 71 observed by the antenna (# 1) 72 and the received signal 92 by the radio wave 84 from the satellite (# 2) 73 observed by the antenna (# 2) 74. A method for estimating TDOA and FDOA will be described.

Define the following variables:
s (t): A signal radiated from the radio wave source 70.
a (t): A modulated signal multiplied by a carrier wave in a signal radiated from the radio wave source 70. Expressed as a complex number.
s ₁ (t): Received signal 91 of radio wave 83 from radio wave source 70 received by satellite (# 1) 71.
s ₂ (t): A reception signal 92 of the radio wave 84 from the radio wave source 70 received by the satellite (# 2) 73.
s _1d (t): A signal from the radio wave source 70 relayed by the satellite (# 1) 71 received by the antenna (# 1) 72.
s _2d (t): A signal from the radio wave source 70 relayed by the satellite (# 2) 73 received by the antenna (# 2) 74.
τ _1d : Time required for radio waves to reach the antenna (# 1) 72 from the satellite (# 1) 71.
τ _2d : Time required for radio waves to reach the antenna (# 2) 74 from the satellite (# 2) 73.
ωc: Angular frequency of the carrier wave of the radio wave from the radio wave source 70. ωc = 2πfc.
f _1D : A change amount of the carrier frequency when the signal is relayed by the satellite (# 1) 71.
f _2D : A change amount of the carrier frequency when the signal is relayed by the satellite (# 2) 73.

The signal s (t) radiated from the radio wave source 70 is expressed as follows. Actually, the signal includes noise, but here, the expression is expressed by ignoring the noise component.
s (t) = a (t) * exp (jωct) (8)
The signal s ₁ (t) from the radio wave source 70 received by the satellite (# 1) 71 is expressed as follows.
s ₁ (t) = a (t−τ ₁ ) * exp (j (ωc−2πf _d1 ) (t−τ ₁ )) (9)
The signal s ₂ (t) from the radio wave source 70 received by the satellite (# 2) 73 is expressed as follows.
s ₂ (t) = a (t−τ ₂ ) * exp (j (ωc−2πf _{d 2} ) (t−τ ₂ )) (10)

  In practice, delay and Doppler frequency displacement also occur in the downlink satellite line from the satellite (# 1) 71 and the satellite (# 2) 73 to the monitoring station. They can be removed from the received signals 91 and 92 because the position of the monitoring station and the satellite's orbit are known. Expressions (9) and (10) are expressed as signals after removing the influence of the downlink satellite channel.

The signal s _1d (t) from the radio wave source 70 relayed by the satellite (# 1) 71 received by the antenna (# 1) 72 is expressed as follows.
s _1d (t) = s ₁ (t-τ _1d ) * exp (-j2πf _1D ) (t-τ _1d )) (11)
Substituting equation (9) into equation (11) yields:
s _1d (t) = a (t−τ ₁ −τ _1d ) * exp (−j (ωc−2π (f _d1 + f _1D )) (t−τ ₁ −τ _1d )) (12)

The signal s _2d (t) from the radio wave source 70 relayed by the satellite (# 2) 73 received by the antenna (# 2) 74 is expressed as follows.
s _2d (t) = s ₂ (t-τ _2d ) * exp (-j2πf _2D ) (t-τ _2d )) (13)
Substituting equation (10) into equation (13) yields:
s _2d (t) = a (t−τ ₂ −τ _2d ) * exp (−j (ωc−2π (f _d2 + f _2D )) (t−τ ₂ −τ _2d )) (14)

In order to estimate TDOA and FDA from the observable signals s _1d (t) and s _2d (t), a two-dimensional correlation value ccf (τ, f) expressed by the following equation is used. Here, τ is a parameter corresponding to TDOA. f is a parameter corresponding to FDOA. Here, x ^* (t) is a complex conjugate of x (t). It should be noted that the time range for integration in equation (15) is, for example, in the range of several minutes to several tens of minutes, and is appropriately determined according to the situation. The (τ, f) for calculating the two-dimensional correlation value ccf is called a search point.
ccf (τ, f) = ∫s ₁ (t) * s ₂ ^* (t−τ) * exp (−j2πft) dt
= ∫s _1d (t + τ _1d ) * s _2d ^* (t + τ _2d −τ) * exp (j2π (f _1D −f _2D −f) t) dt (15)
Substituting Equation (12) and Equation (13) into Equation (15) gives the following.
ccf (τ, f) = ∫a (t−τ ₁ ) * a ^* (t−τ ₂ + τ) * exp (j2π (−f _d1 + f _d2 −f) t) dt (16)

  In Expression (15), the term exp (−j2πft) is a complex number having an absolute value of 1 that rotates at the determined frequency f. The frequency f is a frequency corresponding to FDOA.

Equation (16) is as follows when τ = τ ₁ -τ ₂ and f = f _d1 -f _d2 .
ccf (τ ₁ −τ ₂ , f _d1 −f _d2 ) = ∫a (t−τ ₁ ) * a ^* (t−τ ₁ ) dt
= ∫ | a (t-τ ₁ ) | ² dt (17)
Equation (17) means that when τ = τ ₁ -τ ₂ and f = f _d1 -f _d2 , ccf (τ, f) takes a peak. When (τ, f) is other than that, ccf (τ, f) becomes zero.

In the above equation, s _1d (t) and s _2d (t) are expressed as analog variables. In practice, the digital signal digitized by the A / D converter is processed. Details are omitted.

  In actual positioning, it is unavoidable that the frequency deviation of the receiving equipment of the monitoring station and the oscillator of the communication satellite and the offset deviation (steady deviation) occur in the orbit (position and velocity) of the communication satellite. Therefore, a time or frequency offset shift occurs in the received signals s1 (t) and s2 (t).

For example, the arrival time tau ₁ for satellite # 1 becomes tau ₁ + .DELTA..tau ₁ if including error .DELTA..tau _1, the Doppler frequency shift amount _{f d1} becomes _{f d1} + _{Δf d1} if including error Delta] f _d1. Then, τ, which is the TDOA in which Equation (16) takes a peak, shifts to τ + Δτ ₁ , and f, which is FDOA, shifts to f + Δf _d1 . As a result, a position shift corresponding to the shift amount (Δτ ₁ , Δf _d1 ) occurs.

  In order to grasp and correct this deviation amount, a radio wave source in which another position is known at the same time is actually used. This radio wave source is referred to herein as a reference station. The unknown radio wave source 70 is called a target station to be distinguished. FIG. 2 is a diagram for explaining processing for correcting a time and frequency offset shift using a reference station.

  The main lobe radio wave 85 radiated from the radio wave source 75 as the reference station is transmitted toward the satellite (# 1) 71. At the same time, the radio wave source 75 emits a side lobe radio wave 86. The satellite (# 1) 71 relays the radio wave 85 and transmits the radio wave 87. The radio wave 87 from the satellite (# 1) 71 is received by the antenna (# 1) 72 of the monitoring station. The antenna (# 1) 72 generates a reception signal 93 from the radio wave 87. The sidelobe radio wave 86 radiated from the radio wave source 75 is relayed by the satellite (# 2) 73 and received as the radio wave 88 by the antenna (# 2) 74 of the monitoring station. The antenna (# 2) 74 generates a reception signal 94 from the radio wave 88.

A two-dimensional correlation value ccf (τ, f) is also calculated for the received signals 93 and 94 generated from the radio waves 85 and 86 radiated from the radio wave source 75 which is a reference station. With reference to FIG. 3, processing for correcting time and frequency offset deviation using a reference station will be described. FIG. 3 (a) shows the relationship between the measured value and the theoretical value of the position of the search point where the two-dimensional correlation value ccf for the reference station peaks. The position of the search point at which the two-dimensional correlation value ccf reaches a peak is called a peak position. Assume that the search point 31 (measured value of peak position) where the two-dimensional correlation value ccf calculated from the received signals 93 and 94 has a peak is (τ _r , f _r ). It is assumed that the search point 32 (the theoretical value of the peak position) where the two-dimensional correlation value ccf should have a peak when there is no offset deviation, which can be calculated from the known position of the reference station, is (τ _r0 , f _r0 ). Δτr and Δfr representing the offset deviation can be calculated as follows.
Δτ _r = τ _r −τ _r0 (18)
Δf _r = f _r −f _r0 (19)

FIG. 3B shows the relationship between the measured value and the theoretical value of the position of the search point where the two-dimensional correlation value ccf for the target station peaks. A search point 33 (measured value of peak position) at which the two-dimensional correlation value ccf (τ, f) for the received signals 91 and 92 from the radio wave source 70 as the target station reaches a peak is (τ _t , f _t ). And The offset deviation for the target station is represented by (Δτ _t , Δf _t ). The offset deviation for the target station can be approximated as follows.
Δτ _t ≈Δτ _r = τ _r −τ _r0 (20)
Δf _t ≈Δf _r = f _r −f _r0 (21)
Although not shown here, the offset deviation may be estimated from the offset deviation of the reference station in consideration of the actually measured values of the peak positions of the target station and the reference station.

A theoretical value 34 (τ _t0 , f _t0 ) in which an offset deviation is considered in the actual measurement value of the peak position of the target station can be calculated as follows.
τ _t0 = τ _t + Δτ _t ≈τ _t + Δτ _r = τ _t + τ _r −τ _r0 (22)
f _t0 = f _t + Δf _t ≈f _t + Δf _r = f _t + f _r −f _r0 (23)
The position of the target station is calculated using the theoretical value 34 (τ _t0 , f _t0 ) of the peak position of the target station. By doing so, the position of the target station can be estimated with higher accuracy than in the case where the offset deviation is also taken into consideration.

  FIG. 4 is a schematic diagram illustrating the configuration of the position estimation apparatus according to Embodiment 1 of the present invention. The radio wave source position estimation device 50 includes a correlation value calculation unit 1, a search range determination unit 2, a peak detection unit 3, a search solution storage unit 4, and a positioning unit 5.

The correlation value calculation unit 1 receives the signal s _1d (t) from the radio wave source 70 relayed by the satellite (# 1) 71 received by the antenna (# 1) 72 and the antenna (# 2) 74. The time difference τ and the frequency difference f are set for the signal s _2d (t) from the radio wave source 70 relayed by the satellite (# 2) 73, and the two-dimensional correlation value ccf expressed by the equation (15) is obtained. calculate.

The search range determination unit 2 sets search ranges for the parameters τ and f according to the elapsed time from the latest positioning. For example, if a threshold determined from the most recent positioning, for example, 10 hours or more have elapsed (referred to as the first), the data of the most recent positioning cannot be used, and the rectangular range defined below is searched. Range.
τ0−Δτ1 ≦ τ ≦ τ0 + Δτ1 (24)
f0−Δf1 ≦ f ≦ f0 + Δf1 (25)
Here, τ0, Δτ1, f0, and Δf1 are predetermined values. FIG. 5 is a diagram for explaining a first search range in the position estimation apparatus according to the first embodiment. The search range 41 shown in FIG. 5 is a first range determined so that a peak exists even if the range in which the radio wave source 70 can exist, measurement conditions, and the like change.

The case where the threshold determined from the latest positioning has not elapsed is called the second or subsequent positioning. The search range in the second and subsequent positioning is a second range that is smaller than the first range that is the search range in the first positioning. The second range is expressed as follows using a coefficient α (0 <α <1), where (τn, fn) is a search point at which the two-dimensional correlation value ccf peaks at the latest positioning.
τn−α * Δτ1 ≦ τ ≦ τn + α * Δτ1 (26)
fn−α * Δf1 ≦ f ≦ fn + α * Δf1 (27)

As shown below, the second search range may be determined by using different coefficients such as a coefficient ατ for the time difference τ and a coefficient αf for the frequency f.
τn−ατ * Δτ1 ≦ τ ≦ τn + ατ * Δτ1 (26A)
fn−αf * Δf1 ≦ f ≦ fn + αf * Δf1 (27A)
When the offset deviation can be predicted to some extent, the coefficient on the + side may be αp and the coefficient on the − side may be αn as follows. Here, 0 <αn + αp <2.
τn−αn * Δτ1 ≦ τ ≦ τn + αp * Δτ1 (26B)
fn−αn * Δf1 ≦ f ≦ fn + αp * Δf1 (27B)
In addition, as shown below, the first search range may be determined centering on the search point (τn, fn) that becomes the peak in the latest search, instead of the fixed value (τ0, f0). .
τn−Δτ1 ≦ τ ≦ τn + Δτ1 (24A)
fn−Δf1 ≦ f ≦ fn + Δf1 (25A)

  FIG. 6 is a diagram for explaining the second and subsequent search ranges in the position estimation apparatus according to the first embodiment. The search range 42 shown in FIG. 6 is smaller than the search range 41 shown in FIG. The search range 42 is a range centered on the time difference τn and the frequency difference fn at the time of the latest positioning. Note that if (τn, fn) is included in the search range, it may not be the center.

The coefficient α is determined as follows, for example, by the elapsed time ΔT from the latest positioning. Α is determined to be monotonously non-decreasing as the elapsed time ΔT increases. By doing so, the size of the second search range becomes monotonously non-decreasing with respect to the elapsed time.
10 hours> ΔT ≧ 6 hours α = 0.8
6 hours> ΔT ≧ 2 hours α = 0.5
2 hours> ΔT α = 0.3
When α is determined in this way, the amount of calculation can be reduced as the elapsed time is smaller without the peak position being outside the search range.

  The peak detector 3 determines the parameters τ and f at which the two-dimensional correlation value ccf has the maximum peak value by changing the parameters τ and f at a predetermined step size. τ is TDOA and f is FDOA. The search step size is initially large and may be reduced as the peak range is estimated.

  The search solution storage unit 4 stores τ and f at which the two-dimensional correlation value ccf obtained by the peak detection unit 3 has the maximum peak value.

  The positioning unit 5 refers to the satellite orbit information according to the equations (5) to (7) in consideration of the offset deviation estimated from the positioning result at the reference station from the parameters τ and f obtained by the peak detection unit 3. The position of the radio wave source 70 is calculated using the position and velocity of the first satellite and the position and velocity of the second satellite. Note that the positioning unit 5 acquires the positions and velocity vectors of the satellite (# 1) 71 and the satellite (# 2) 73 from the satellite orbit information.

  In the radio wave source position estimating apparatus according to the present invention, the search range is determined based on the time difference and frequency difference at the time of the latest positioning and the elapsed time from the most recent positioning, so when the estimation of the position of the radio wave source is repeated. The amount of calculation for estimating the position can be reduced. In particular, the second search range when the elapsed time is less than the threshold is smaller than the first search range when the elapsed time is equal to or greater than a predetermined threshold, and the center of the second search range is closest. The time difference τn and the frequency difference fn at the time of positioning are set to a range. By doing so, when repeatedly estimating the position of the radio wave source, the amount of calculation can be made smaller than when the search range is always the same.

50 Radio Source Location Estimation Device 1 Correlation Value Calculation Unit 2 Search Range Determination Unit 3 Peak Detection Unit 4 Search Solution Storage Unit 5 Positioning Unit 31 Measured Value of Reference Station Peak Position 32 Theoretical Value of Reference Station Peak Position 33 Target Station Measured value 34 of peak position Theoretical value 41 of peak position of target station Search range 42 at the first positioning 42 Search range 61 at the second and subsequent positionings 61 EDOA line 62 Equal FDOA line 70 Radio source (target station)
71 Satellite (# 1)
72 Antenna (# 1)
73 Satellite (# 2)
74 Antenna (# 2)
75 Radio source (reference station)
81 radio wave 82 radio wave 83 radio wave 84 radio wave 85 radio wave 86 radio wave 87 radio wave 88 radio wave 91 reception signal 92 reception signal 93 reception signal 94 reception signal

Claims (3)

The first received signal received by the first observation station after the radio wave radiated from the radio wave source having an unknown position is relayed by the first satellite, and the radio wave radiated from the radio wave source is different from that of the first satellite. A value obtained by taking a complex conjugate of the second received signal relayed by the second satellite and received by the second observation station with a predetermined time difference with respect to the first received signal, and a determined frequency A correlation value calculation unit for calculating a two-dimensional correlation value obtained by integrating a value obtained by multiplying a complex number whose absolute value rotates by 1 for a predetermined time;
A peak detector for detecting the time difference and the frequency at which the two-dimensional correlation value takes a maximum peak by changing the time difference and the frequency;
A search range determination unit for determining a search range which is a range in which the time difference and the frequency are changed;
A search solution storage unit for storing the time difference and the frequency at which the two-dimensional correlation value takes a maximum peak;
The time difference and the frequency at which the two-dimensional correlation value detected by the peak detector takes the maximum peak, the position and velocity of the first satellite, and the position and velocity of the second satellite are used. And a positioning unit for determining the position of the radio wave source,
The radio wave source position estimating device, wherein the search range determining unit determines the search range based on the time difference at the time of the latest positioning and the frequency and an elapsed time from the most recent positioning.   The search range determination unit sets the search range as a first search range when the elapsed time is greater than or equal to a determined threshold value, and sets the search range to the nearest search range when the elapsed time is less than the threshold value. The radio wave source position estimation apparatus according to claim 1, wherein the second search range is smaller than the first search range including the time difference and the frequency at the time of positioning.   The position estimation device of the radio wave source according to claim 2, wherein the size of the second search range is monotonously non-decreasing with respect to the elapsed time.

Images