JPWO2020012591A1 - Direction estimation device and wireless device - Google Patents

Abstract

Direction estimation device according to the present invention, a signal quality calculation unit that measures or predicts the quality of signals received using a plurality of antennas, according to the quality of the signal measured or predicted by the signal quality calculation unit, An angle range setting unit that sets an angle range for estimating the arrival direction of the signal, and a direction estimation unit that estimates the arrival direction of the signal within the angle range set by the angle range setting unit. And With this configuration, it is possible to perform direction estimation in a wider angle range than that of the related art for a signal having high signal quality among signals to be subjected to direction estimation.

Description

The present invention relates to a direction estimating device and a wireless device for estimating the direction of a signal.

A wireless device that estimates the direction of existence of an object to be measured needs direction estimation that accurately estimates the direction of a signal from a wide angle range when receiving the signal. Generally, in the direction estimation performed by a wireless device, the arrival direction of the signal is estimated using the phase difference of the signals received by a plurality of antennas. There are various algorithms for direction estimation, but basically, the direction of arrival of the signal that causes the phase difference measured between multiple antennas is searched from within the defined angular range, and the phase difference is calculated. The direction in which is generated is estimated as the arrival direction of the signal.

In the conventional direction estimation device, a certain angle range for performing direction estimation is usually determined in advance so that the arrival directions of all signals satisfying a certain quality standard can be estimated. For example, when each antenna has an omni-antenna, direction estimation may be performed with a direction of −90° to 90° as an angle range. There are also cases where the angle range for direction estimation is determined based on the beam width of the receiving antenna, the beam width of signal transmission, etc. (for example, Patent Documents 1 and 2) or by a delay profile ( For example, Patent Document 3). As described above, there are various methods for setting the angle range, but this angle range is determined in advance before performing the direction estimation.

JP, 2017-67623, A JP, 2016-151424, A JP 2001-251233 A

In the conventional direction estimation device, a certain angle range in which direction estimation is performed is predetermined so that the arrival directions of all signals satisfying a certain quality standard can be estimated. That is, in the conventional direction estimation device, since the direction estimation is performed for all signals within a certain angle range, the angle range can be estimated for signals having low signal quality while satisfying a certain quality standard. Is set. As a result, for signals with high signal quality, direction estimation cannot be performed in a wider angle range, and if the direction of arrival of the signal is outside the set angle range, the direction of the signal There is a problem that cannot be estimated.

The present invention has been made to solve the above problems, and estimates the direction of a signal in a wider angle range than that of the prior art for a signal having high signal quality among signals to be subjected to direction estimation. The purpose is to obtain a possible direction estimation device.

Direction estimation device according to the present invention, a signal quality calculation unit that measures or predicts the quality of the signal received using a plurality of antennas, depending on the quality of the signal measured or predicted by the signal quality calculation unit, An angle range setting unit that sets an angle range for estimating the arrival direction of the signal, and a direction estimation unit that estimates the arrival direction of the signal within the angle range set by the angle range setting unit. And

According to the present invention, it is possible to perform direction estimation in a wider angle range than that of the conventional technique for a signal having high signal quality among signals to be subjected to direction estimation.

3 is a configuration example of radio apparatus 100 and direction estimation apparatus 500 according to Embodiment 1. 3 is a flowchart showing a processing procedure of the wireless device 100 according to the first embodiment. 3 shows an example of a format of the signal 30 according to the first embodiment. Phases of signals output from matched filters 4, 5, and 6 in the first embodiment. 7 shows an example of the amplitudes of signals output from matched filters 4, 5, and 6 in the first embodiment. 9 is an example of setting an angular range performed by the direction estimation unit 9 in the first embodiment. A direction estimation use environment exemplified in the first embodiment. FIG. 4 is a diagram showing a relationship between the arrangement of array antennas and the signal arrival direction φ in the wireless device 100 according to the first embodiment. The evaluation result which evaluated L((GAMMA),r) obtained by the direction estimation method in Embodiment 1. FIG. 6 is a beam pattern diagram for explaining the process in the first embodiment. A processing circuit included in the wireless device 100 in Embodiment 1. A processing circuit and a memory included in the wireless device 100 in Embodiment 1. 6 is a configuration diagram of a wireless system according to Embodiment 2. FIG. 3 is a configuration diagram of a wireless device 200 according to Embodiment 2. FIG. 5 is a configuration diagram of a terminal device 210 according to Embodiment 2. FIG. 7 is a flowchart showing the operation of the wireless system according to the second embodiment. Antenna arrangement, estimation accuracy, and angle error for performing direction estimation in all directions in the third embodiment. The antenna structure in the radio|wireless apparatus 100 of Embodiment 3. 6 is a configuration diagram of a wireless device 300 according to Embodiment 3. FIG. FIG. 16 is a diagram showing signal transmission and reception of a wireless device 400 in Embodiment 4. 6 is a configuration diagram of a wireless device 400 according to Embodiment 4. FIG. Flowchart showing operation of radio apparatus 400 according to Embodiment 4 FIG. 16 is a diagram showing a state of direction estimation at each time in the fifth embodiment. FIG. 16 is a diagram showing a transition of L(Γ,r) with respect to sin φ1 in the sixth embodiment.

Embodiment 1.
Hereinafter, embodiments of the present invention will be described.

FIG. 1 is a diagram showing a configuration example of radio apparatus 100 and direction estimation apparatus 500 according to the first embodiment. The wireless device 100 has antennas 0, 1, 2, matched filters 4, 5, 6, a signal quality calculation unit 7 for measuring the signal quality, and a signal quality measured by the signal quality calculation unit 7. An angle range setting unit 8 that sets an angle range for estimating the signal angle, and a direction estimation unit 9 that estimates the direction of the signal within the angle range set by the angle range setting unit 8. The direction estimation device 500 includes a signal quality calculation unit 7, an angle range setting unit 8, and a direction estimation unit 9. In each of the following figures, the same reference numerals indicate the same or corresponding parts.

The signal received by the wireless device 100 may be the one transmitted from the measurement object or the one transmitted by the wireless device 100. For example, when the wireless device 100 transmits a signal, the wireless device 100 can estimate the existing direction of the measurement target by receiving the reflected wave of the transmission signal from the measurement target and estimating the direction of the received signal. In addition, when the measurement object transmits a signal, the wireless device 100 receives the signal transmitted by the measurement object and estimates the direction of the received signal, so that the existence direction of the measurement object can be estimated.

The antennas 0, 1, 2 receive signals wirelessly transmitted. Although FIG. 1 shows a configuration including three antennas as an example, the number of antennas is not limited to three, and any number of antennas of three or more may be used. Matched filters 4, 5, and 6 are filters corresponding to known signals, and when a known signal included in a received signal passes through matched filters 4, 5, and 6, the output values of matched filters 4, 5, and 6 increase. The signal quality calculation unit 7 measures the signal quality of the received signal using the output values from the matched filters 4, 5, and 6. The signal used for measuring the signal quality may be any one of the output values from the matched filters 4, 5, and 6, or may use a plurality of output values. The signal quality is measured by, for example, a signal-to-noise power ratio (SNR: Signal to Noise Power Ratio). The signal quality is not limited to the SNR, and the ratio of the standard deviation of the signal power to the standard deviation of the noise power may be used, or any other parameter indicating the signal quality may be used.

The angle range setting unit 8 sets the angle range when the direction estimation unit 9 estimates the direction of the received signal according to the signal quality measured by the signal quality calculation unit 7. The direction estimation unit 9 estimates the direction of the received signal using the output values of the matched filters 4, 5, and 6 within the angle range set by the angle range setting unit 8.

Next, the operation of the wireless device 100 will be described. FIG. 2 shows a flowchart showing the processing procedure of the wireless device 100.

First, the wireless device 100 receives the signal 30 with the antennas 0, 1, and 2 (S201). FIG. 3 shows an example of the format of the signal 30. In FIG. 3, signal 30 is represented as a spread signal having amplitudes of +1 and -1. The signal 30 may be any signal as long as it is a known signal. For example, it may be a single carrier signal, a multicarrier signal, a spread signal, a chirp signal, or any other signal.

Next, the wireless device 100 inputs the signals received by the antennas 0, 1, and 2 to the matched filters 4, 5, and 6 (S202). FIG. 4 shows the phases of the signals output from the matched filters 4, 5, and 6. Matched filters 4, 5, and 6 output signals corresponding to the received signals at antennas 0, 1, and 2, respectively. The outputs corresponding to the matched filters 4, 5 and 6 have phases θ0, θ1 and θ2, respectively. Further, as shown in FIG. 4, the distance between the antenna 0 and the antenna 1 is d1, and the distance between the antenna 0 and the antenna 2 is d2.

FIG. 5 shows an example of the amplitude of the signal output from the matched filter 4. When a known signal is input to the matched filter 4, the matched filter 4 outputs the amplitude 51. When a signal that is not a known signal is input to the matched filter 4, the output peak of the matched filter 4 becomes smaller than the peak of the amplitude 51. Therefore, the timing at which the known signal is input to the matched filter 4 can be extracted by determining the output from the matched filter 4 by the threshold value. The timing of the known signal can be known in advance. As a method of grasping the timing of the known signal, any existing method may be used. Further, the output from the matched filter 4 contains stationary noise 52. Although the output from the matched filter 4 has been described here, similar signals are also output from the matched filters 5 and 6.

The signal quality calculation unit 7 measures the signal quality (S203). The signal quality calculation unit 7 measures the power of the stationary noise 52 in a state where no signal is input to the matched filter 4. Further, the power of the known signal can be measured by measuring the amplitude 51 of the output of the matched filter 4 at the timing when the known signal is detected. Although the case where the matched filter 4 is used has been described here, the outputs of the matched filters 5 and 6 may be used instead of the output of the matched filter 4. Further, the signal quality calculation unit 7 may measure the average of the signal qualities of the outputs of the matched filters 4, 5, and 6. For example, when the signal quality is measured as SNR, the ratio of the power of the known signal and the power of the noise 52 is calculated. There are various methods for measuring the SNR, but any existing method may be used.

The angle range setting unit 8 sets the angle range (S204). FIG. 6 shows an example of the setting of the angle range performed by the direction estimation unit 9. As shown in FIG. 6, the angle range setting unit 8 sets different angle ranges according to the signal quality of the signal. In FIG. 6, the angular width D (D is a specific angular width) when SNR<=10 dB, the angular width 2D when 10 dB<SNR<=20 dB, and the angular width 5D when 20 dB<SNR<=30 dB. It is set as an angle range. This angle range is set so that direction estimation is performed by satisfying a predetermined criterion. This criterion is, for example, a criterion that the direction estimation success rate satisfies a predetermined success rate, the direction estimation accuracy satisfies a predetermined accuracy, or the like.

Note that the example of setting the angle range is not limited to FIG. 6, and any form of setting the angle range according to the signal quality may be used so that the direction estimation satisfies the criterion. For example, the angle range can be set by a function that inputs the signal quality and outputs the angle range.

The direction estimation unit 9 estimates the direction of the received signal using the angle range set by the angle range setting unit 8 (S205). Since the angle range setting unit 8 sets the angle range so that the direction estimation satisfies the criterion, the direction estimation unit 9 can perform the direction estimation satisfying the criterion.

As described above, in the wireless device 100, by setting the angle range according to the signal quality and estimating the direction of the received signal, it is possible to estimate the direction within the angle range suitable for the signal quality. As a result, direction estimation can be performed in a wide angle range for a signal with high signal quality.

In the following, in order to deepen the understanding in the present embodiment, an example of a specific direction estimation and a characteristic analysis of direction estimation in wireless device 100 when three antennas are used will be shown. However, the invention described in this embodiment is not limited to the case of three antennas.

(A1) Usage Environment A usage environment for direction estimation illustrated in FIG. 7 is shown. FIG. 7 shows an example in which the terminal device 110, which is an object to be measured, transmits a radio wave that carries a known signal, and the wireless device 100 estimates the direction of the radio wave. Here, an environment will be taken as an example, in which the radio waves have a narrow angular spread enough to be regarded as a single direction in the wireless device 100, and the influence of other scattered waves of radio waves on the direction estimation is small.

(A2) Response Vector FIG. 8 shows the relationship between the arrangement of array antennas and the signal arrival direction φ in the wireless device 100. The wireless device 100 receives radio waves in the direction φ using three antennas (antennas 0, 1, 2) that are linearly arranged. At this time, the response vector a(φ) of the radio wave is expressed by the following equation.
a(φ)=
[1, e(j2π(d1/λ)sinφ), e(j2π(d2/λ)sinφ)] ^T
Here, dm (m=1, 2) is the distance between the antenna 0 and the antenna m, and λ is the wavelength of the radio wave.

The response vector a(φ) can be rewritten as the following equation.
a(φ)=[1, e(j2πFT1), e(j2πFT2)] ^T (1)
F=sin φ, T1=d1/λ, T2=d2/λ (2)
Here, T1 and T2 are fixed values.

In the direction estimation, the range of F in the following equation is handled.
F<=(B/2) ⇔ |φ|<=sin ⁻¹ (B/2) (3)
Here, B represents the estimated range of F.

(A3) Direction estimation method The direction estimation method performed by the direction estimation unit 9 will be described.

At the matched filter output of antenna i (=0, 1, 2), the complex amplitude of
(P) ^1/2 exp(jθi)+zi=(η _i ) ^1/2 exp{j(θi+ξi)}
=(η _i ) ^1/2 exp(jθ'i)
i=0, 1, 2(4)
Where P is the power of the received signal at the matched filter output, θi is the phase of the received signal at the matched filter output, zi is the noise at the matched filter output, η _i is the power including the received signal and noise, and ξ _i is The phase measurement error, θ'i, represents the measured phase.

Using the measured phase θ′i, the measured phase difference Δθ′i between antenna 0 and antenna i is expressed by the following equation.
Δθ'i=θ'i-θ'0 i=1, 2
By the way, according to the equation (1), the phase difference Δθi between the antenna 0 and the antenna i (=1, 2) in the ideal state which is not affected by noise has the relation of F=sin φ and the following equation.
Δθ1=2πFT1-2nπ (5)
Δθ2=2πFT2-2mπ (6)
Here, n and m are integers.

Since the phase difference Δθi cannot be measured in a real environment, if the measured phase difference Δθ′i is used instead, the estimated value Fi(n) (i=1, 2) of F corresponding to the equations (5) and (6) becomes Each is expressed by the following equation.
F1(n)=(n+Δθ′1/2π)B1 (7)
F2(m)=(m+Δθ′2/2π)B2 (8)
Bi=1/Ti=λ/di i=1, 2 (9)
Here, Bi (i=1, 2) is a range of F in which direction estimation can be performed using the antenna 0 and the antenna i without generating the uncertainty elements nB1 and mB2, and n(or m) is the uncertainty element nB1( or mB2).

When the estimated value Fi(n) (i=1, 2) satisfies the equation (3) similarly to F, the following equation holds.
−B/2<=(n+Δθ′1/2π)B1<=B/2
−B/2<=(n+Δθ′2/2π)B2<=B/2
Therefore, if the range of Δθ′i (i=1, 2) is defined as 0<=Δθ′i<2π, the range of n and m is given by the following equation.
U={[-B/2B1]<=n<=[B/2B1],
[-B/2B2]<=m<=[B/2B2]} (10)
Here, [a] represents the maximum integer less than or equal to a.

Although the estimated values F1(n) and F2(m) have various values depending on the integers n and m, there is a high possibility that the state where F1(n) and F2(m) match is F=sin φ to be obtained. Therefore, the direction estimation unit 9 performs the following direction estimation.
(Q1) |F1(n)−F2(m)| is calculated to find the minimum integer group (n′, m′) of the following equation.
(N′,m′)=arg _(n,m)εU min |F1(n)−F2(m)|
The range B in U (equation (10)) is set in advance so that (n′, m′) can be uniquely determined.

(Q2) A highly accurate estimated value F′ of the following equation is obtained to obtain a direction estimated value φ.
F′={(2T1 ² −T1T2)F1(n′)+(2T2 ² −T1T2)F2(m′)}
/{2(T1 ² −T1T2+T2 ² )} (11)
φ=sin ⁻¹ F′ (12)

The equation (11) is derived by the derivation process described below. First, a highly accurate estimated value F′ is expressed in the form of the following equation for appropriately weighting F1(n) and F2(m), and appropriate weights w1 and w2 are obtained.
F′=w1·F1(n)+w2·F2(m)=w ^T F (13)
w=[w1, w2] ^T
F=[F1(n), F2(m)] ^T
Here, ^T represents transposition.

From the equations (5) and (6), F0=sin φ corresponding to the true direction satisfies the simultaneous equations of the following equations in an ideal state that is not affected by noise.
F0=n·B1+f1 (5')
F0=m·B2+f2 (6')
fi=Δθi/(2πTi) i=1, 2
Let (n, m) give F0=sin φ corresponding to the true direction be (n0, m0).

In the control (Q1), a state in which (n', m') coincides with (n0, m0) of F0=sinφ corresponding to the true direction is called a "success state". The conditions for a successful state (n',m')=(n0,m0) are discussed below.

First, equations (7) and (8) are rewritten by the following equations.
F1(n)=nB1+f1+e1 (7')
F2(m)=nB2+f2+e2 (8′)
ei=(ξi−ξ0)/(2πTi) i=1, 2
Assuming that the success state (n′, m′)=(n0, m0) in the control (Q1), F is calculated from the following equations (5′), (6′), (7′), and (8′). Meet
F=1·F0+e (14)
1=[1,1] ^T
e=[e1, e2] ^T
=(1/2π)[ξ1/T1, ξ2/T2] ^T
-(Ξ0/2π)[1/T1, 1/T2] ^T
From equations (13) and (14), the weight w that maximizes the ratio of the power (w ^T 1) ^{2 of} F0=sin φ and the noise power (w ^T e) ² corresponding to the true direction included in F′ is The MVDR (Minimum Variance Distortion Response) weight of the following equation is obtained.
w=Φ ⁻¹ 1/(1 ^T Φ ⁻¹ 1) (15)
= 1/(2(T1 ² −T1·T2+T2 ² ))
[2T1 ² −T1·T2, −T1·T2+T2 ² ] ^T
Φ=E [ee ^H ]
Here, ^H represents a conjugate transposition. From the weight w of Expression (15), the relationship of Expression (11) is derived from Expressions (13) and (15).

(A4) Direction estimation possible range B
Assuming the direction estimation in the direction estimation unit 9 shown in (A3), the characteristics of the direction estimation possible range B set by the angle range setting unit 8 will be described. The direction estimation is appropriately performed because the integer set (n′, m′) derived in (Q1) is expressed by Equations (5) and (6) (which cannot be measured in the real environment but can be calculated in the simulation environment). When it matches the integer set (n0, m0) in a noise-free ideal state, which is a success state in which the true direction can be estimated without causing an error due to uncertainty (ambiguity). Become.

Therefore, the success rate Ps that results in a successful state is first derived. Using the formulas (5′), (6′), (7′), and (8′), F1(n)−F2(m) in the control (Q1) is represented by the following formula.
F1(n)-F2(m)=Δn·B1-Δm·B2+e1-e2
Δn=n−n0
Δm=m−m0
The success state (n′,m′)=(n0,m0) satisfies the formula (10) and (n,m)≠(n0,m0) is satisfied for the following (n,m). This is the case when the expression is satisfied.
|X(n,m)+e1-e2|>|e1-e2| (16)
X(n,m)=Δn·B1−Δm·B2
Here, among X(n,m), the negative value X ⁻ closest to 0 and the positive value X ⁺ closest to 0 are respectively represented by the following expressions.
X ⁻ =Δn ⁻ ·B 1 −Δm ⁻ ·B 2
X ⁺ =Δn ⁺ ·B1-Δm ⁺ ·B2
At this time, Expression (16) is satisfied in the following cases.
When · e1-e2> = 0 X - <-2 (e1-e2) ^{Thus, e1-e2 <-X - /} 2
-When e1-e2<0 X ⁺ <-2(e1-e2) Therefore, e1-e2>-X ⁺ /2
That is,
^{-X + / 2 <e1-e2} <-X - / 2
Is satisfied.

Therefore, the success rate Ps is the random variable u
u=2(e1-e2)/B1
={ξ1-ξ0-r(ξ2-ξ0)}/π
Corresponds to the probability that satisfies the following equation.
^{Y -} <u <Y ⁺
Y ⁻ =Δn ⁻ −Δm ⁻ ·r
Y ⁺ =Δn ⁺ −Δm ⁺ ·r
r=T1/T2=d1/d2
Y ⁻ and Y ⁺ respectively represent a negative value closest to 0 and a positive value closest to 0 in Y=Δn−Δm·r. Here, Δn and Δm are integers that satisfy the following equation.
[-B/(2B1)]<=n<=[B/(2B1)]
[-B/(2B2)]<=m<=[B/(2B2)]
Therefore, the range of Δn=n−n0 and Δm=m−m0 is [−B/(2B1)]−n0<=Δn<=[B/(2B1)]−n0(17)
[-B/(2B2)]-m0<=Δm<=[B/(2B2)]-m0(18)
Given in. Further, the random variable ξi when performing the calculation is ξi=arctan(yi/(Γ ^1/2 +xi)), i=0,1,2
Given in. Here, xi and yi (i=0, 1, and 2) are Gaussian variables having variance 1/2 and are independent of each other, and Γ is the SNR when the phase θi is measured by the matched filter output.

From the equations (17) and (18), the success rate Ps varies depending on n0, m0, that is, the radio wave direction φ determined by n0, m0. The success rate Ps also changes depending on the estimated range B. Therefore, the range B in which Ps>Preq (Preq: required success rate) can be maintained is calculated by the following process.
(R1) SNR Γ (=10, 20, 30 dB) and ratio r (0<r<1) are set.
Under (R2)SNR Γ and ratio r, the maximum value L(Γ,r) of B/B2 that can maintain Ps>Preq is found for all (n0,m0)εU.

At this time, the range B in which Ps>Preq can be maintained satisfies the following equation.
B/B2 <=L(Γ,r)⇒B<=L(Γ,r)·B2 (19)

FIG. 9 shows the results of evaluating L(Γ, r) for Preq=0.99, SNR=10, 20, 30 dB, and the ratio r (0<r<1). In the figure, L(.GAMMA.,r) is a large value at r=0.37 and 0.63 at any of SNR=10, 20, and 30 dB. In FIG. 9, the ratio B/B2 is evaluated based on only the ratio r=d1/d2 without depending on the specific antenna intervals d1 and d2. The evaluation result of FIG. 9 is a relationship that is established regardless of the size of the antenna intervals d1 and d2.

From the result of FIG. 9, it can be seen that the angle range in which the direction estimation can be performed while maintaining the predetermined success rate Preq is determined depending on the ratio r of antenna intervals r=d1/d2 and the signal quality (for example, SNR). .. From this result, it is understood that the direction estimation unit 9 can perform the direction estimation satisfying the reference by setting the angle range in which the direction estimation is performed based on the signal quality in the angle range setting unit 8.

(A5) Estimation accuracy In the successful state, the direction estimation accuracy of the direction estimation performed by the direction estimation unit 9 is derived. F=sin φ and the noise power ratio γ in the highly accurate estimated value F′ (equation (11)) are expressed by the following equation.
γ = 1 ^T Φ ^-1 1
=(8π ² (T1 ² +T2 ² −T1T2))/(3σ ² ).
=(8π ² (d1 ² +d2 ² −d1d2))/(3λ ² σ ² ) (20)
Here, σ ² =E[|ξ0| ² ]=E[|ξ1| ² ]=E[|ξ2| ² ]. From Expression (20), it is possible to improve the direction estimation accuracy by increasing the antenna distances d1 and d2 while maintaining the success state.

The power ratio γ has a relationship with the estimated value F′ by the following equation.
F′=sin φ+e E [|e| ² ]=1/γ
Here, e represents an error component.
When φ=0, the following equation holds.
φ'≒φ+e=e
At this time, the standard deviation (rad) of the angular error included in the estimated value φ'is
E[|e| ² ] ^1/2 =1/γ ^1/2
The standard deviation (°) of angular error is
180/(π・γ ^1/2 )
Given in.
(End of explanation of specific processing and characteristic analysis assuming 3 antennas)

As shown in FIG. 9, the maximum value of the angle range B for which direction estimation can be performed while satisfying the required success rate Preq by the SNR of the signal measured by the signal quality calculation unit=L(Γ,r)・B2 changes. Therefore, in the present embodiment, in S204, the angle range setting unit 8 sets the angle range B smaller than L(Γ,r)·B2 according to the signal quality (for example, SNR Γ), and in S205, The direction estimation unit 9 estimates the direction of the received signal within the angular range B. With this configuration, even when the signal quality changes, it is possible to perform direction estimation while satisfying a required criterion such as a success rate.

Note that, as shown in FIG. 9, the maximum value of the angular range B in which the direction estimation can be performed differs depending on the antenna interval ratio r=d1/d2. Therefore, in order to increase the maximum value of the angle range B, it is necessary to appropriately set the ratio r=d1/d2 of the antenna intervals.

In general terms, the process of setting the angle range B according to the quality of the signal can also be grasped as follows using the beam pattern shown in FIG. First, it is assumed that the direction of the main lobe 1001 of the beam pattern formed by the plurality of antennas is changed to various directions and the direction of the main lobe 1001 having the highest power is detected as the direction of the signal. At this time, in the direction estimation, it is necessary to distinguish the reception power of the signal 30 received at the peak of the main lobe 1001 from the reception power of the signal 30 received at the side lobe 1002 and the grating lobe 1003. In order to distinguish this received power with a sufficiently small error rate, the received signal is included in the received signal more than the received power difference of the signal generated by the gain difference 1004 between the peak of the main lobe 1001 and the peaks of the side lobe 1002 and the grating lobe 1003. The noise power generated must be small. This is because if the noise power is high, the signal received by the side lobe 1002 or the grating lobe 1003 is erroneously detected as the signal received by the main lobe 1001 and erroneous direction estimation is performed. Therefore, whether or not the direction estimation can be performed without error depends on the magnitude of the noise power, and when the noise power included in the received signal is smaller than the received power difference of the signal caused by the gain difference 1004, a wide angle range is obtained. At 1005, direction estimation can be performed. On the other hand, when the noise power included in the received signal is larger than the received power difference of the signal caused by the gain difference 1004, the signal received in the grating lobe 1003 may be mistaken as the signal received in the main lobe 1001. Therefore, when estimating the direction of the signal, it is necessary to perform direction estimation within a narrow angle range 1006 where the grating lobe 1003 does not appear. In this way, the angle range in which direction estimation can be performed with an appropriate error rate changes depending on the magnitude of noise power included in the received signal.

As a result, as shown in the present embodiment, by performing the process of determining the angle range in which the direction is estimated according to the signal quality, it is possible to maintain an appropriate error rate for various signals. It becomes possible to perform direction estimation. In particular, for signals of high quality, it is possible to perform direction estimation in a wide angle range. This principle basically holds regardless of the number of antennas and the direction estimation method. As described in Non-Patent Document 1 below, the direction estimation method includes a beam scanning type and a null scanning type. In the present embodiment, the beam scanning type direction estimation is basically assumed and described, but the same principle holds true for the null scanning type direction estimation. In the null scanning type direction estimation, when the signal quality (for example, SNR) is low, the influence of noise in the correlation matrix of the array antenna calculated from the received signal becomes large, and the weight vector corresponding to the calculated null direction is ideal. There is an error with respect to the weight vector. As a result, if the direction of arrival is estimated using the weight vector, there is a high possibility that the direction of the grating lobe will be erroneously detected. As described above, even in the null scanning type direction estimation, if the signal quality (for example, SNR) is low, there is a high possibility that the direction of the grating lobe is erroneously detected. Therefore, even in the direction estimation of the null scan type, the direction estimation is performed for various signals while maintaining an appropriate error rate by performing the process of determining the angle range in which the direction estimation is performed according to the signal quality. Will be possible.
[Non-Patent Document 1] Nobuyoshi Kikuma, "Adaptive Signal Processing by Array Antenna", Science and Technology Publishing

As is clear from the above description, the present embodiment has been described by taking the case of three antennas as an example, but the invention shown in this embodiment is not limited to three antennas. Further, the present invention is not limited to the arrival direction estimation method shown in the present embodiment. For any number of antennas as long as there are three or more antennas, the angle range setting unit 8 sets the angle range B according to the quality of the signal, and the direction estimation unit 9 generally knows within the angle range B. The direction of the received signal can be estimated by using the direction estimation method.

It should be noted that, as far as the author knows, the conventional literature does not show that the angle range in which the direction estimation can be performed while maintaining an appropriate error rate varies depending on the signal quality described so far. That is, it has not been known so far that a difference in the angle range in which the direction can be estimated occurs due to the difference in signal quality, and it will be first revealed in the present embodiment. Further, radio apparatus 100 and direction estimation apparatus 500 described in the present embodiment are newly constructed based on the new knowledge.

Each function of the matched filters 4, 5, and 6, the signal quality calculation unit 7, the angle range setting unit 8, and the direction estimation unit 9 in the wireless device 100 is realized by a processing circuit (Processing Circuit). This processing circuit is also called a CPU (Central Processing Unit), a central processing unit, a processing unit, an arithmetic unit, a microprocessor, a microcomputer, a processor, or a DSP that executes a program stored in a memory even if it is dedicated hardware. ).

When the processing circuit is dedicated hardware, as shown in FIG. 11, the processing circuit 1101 may be, for example, a single circuit, a multiple circuit, or a programmed processor. , A parallel programmed processor (multiple programmed processors), an ASIC (Application Specific Integrated Circuit), an FPGA (Field Programmable Gate Array), or a combination thereof. The respective functions of the matched filters 4, 5, 6, the signal quality calculation unit 7, the angle range setting unit 8, and the direction estimation unit 9 may be realized by the processing circuits, or the functions of the respective units may be collectively realized by the processing circuits. You may.

When the processing circuit is a CPU, the wireless device 100 includes a processing circuit 1201 and a memory 1202, as shown in FIG. The functions of the matched filters 4, 5, 6, the signal quality calculation unit 7, the angle range setting unit 8, and the direction estimation unit 9 are realized by software, firmware, or a combination of software and firmware. Software and firmware are described as programs and stored in the memory 1202. The processing circuit 1201 realizes the function of each unit by reading and executing the program stored in the memory 1202. That is, when the wireless device 100 is executed by the processing circuit 1201, the steps of generating a filter output of a received signal, measuring a signal quality, setting an angular range, and estimating a direction result. It comprises a memory 1202 for storing the program to be executed. Examples of these programs can be represented by steps S202 to S205 shown in FIG. It can also be said that these programs cause a computer to execute the procedures and methods of the matched filters 4, 5, and 6, the signal quality calculation unit 7, the angle range setting unit 8, and the direction estimation unit 9. Here, the memory 1202 corresponds to, for example, a nonvolatile or volatile semiconductor memory such as a RAM, a ROM, a flash memory, an EPROM, an EEPROM, a magnetic disk, a flexible disk, an optical disk, a compact disk, a mini disk, or a DVD. To do.

Note that each function of the matched filters 4, 5, 6, the signal quality calculation unit 7, the angle range setting unit 8, and the direction estimation unit 9 is partially realized by dedicated hardware and partially realized by software or firmware. You may do so. For example, the matched filters 4, 5, 6 and the signal quality calculation unit 7 realize their functions by a processing circuit as dedicated hardware, and the angle range setting unit 8 and the direction estimation unit 9 store the processing circuits in a memory. The function can be realized by reading and executing the executed program.

In this way, the processing circuit 1201 can realize each function described above by hardware, software, firmware, or a combination thereof.

As described above, radio apparatus 100 according to the present embodiment sets the angle range in which the direction of the received signal is estimated according to the signal quality of the received signal. With this configuration, it is possible to estimate the direction of a signal having a high signal quality over a wider angle range than that of the related art, and it is possible to estimate the existing direction of the measurement target from the wide angle range. In the present embodiment, the characteristic of the direction estimation is described by taking the specific direction estimation method as a specific example in (A3), but the present embodiment is limited to the direction estimation method shown in (A3). Instead, it is applicable to commonly known direction estimation methods. That is, the phenomenon that the range of angles that can be estimated changes according to the SNR of the signal is valid for a generally known direction estimation method. In general direction estimation, the range of angles depends on the SNR of the signal. Can be set.

Although the first embodiment has described the direction estimation in radio apparatus 100, the direction estimation according to the present embodiment may be applied to a signal other than a radio signal as long as the signal direction is estimated. it can. That is, the direction estimation device 500 in the wireless device 100 can be applied to the direction estimation of any signal, not only the wireless signal. For example, the direction estimation of the present embodiment can be applied to various types of direction estimation such as voice signal direction estimation and vibration direction estimation. Therefore, the application destination of the direction estimation device 500 is not limited to the wireless signal.

Further, in the present embodiment, the known signals 31, 33, 35 are input to the matched filters 4, 5, 6 to measure the phase of the signal 30, but the signal 30 is a non-modulated signal (CW: In the case of continuous wave, the phase of the signal 30 can be directly measured without using the matched filters 4, 5, and 6. For example, when the timing for measuring the phase of the signal 30 is known in advance and the unmodulated signal is measured at that timing, the phase of the signal 30 can be directly measured.

As described above, the direction estimation apparatus 500 according to the present embodiment measures with the signal quality calculation unit 7 that measures the quality of the signal 30 received using the plurality of antennas 0, 1, 2 and the signal quality calculation unit 7. An angle range setting unit 8 for setting an angle range for estimating the arrival direction of the signal, and a direction for estimating the arrival direction of the signal in the angle range set by the angle range setting unit 8. The estimating unit 9 is provided. With this configuration, it is possible to perform direction estimation in a wider angle range than that of the conventional technique for a signal having a high signal quality among signals to be subjected to direction estimation.

In addition, in direction estimation apparatus 500 according to the present embodiment, signal quality calculation section 7 measures the signal-to-noise power ratio of signal 30 as the quality. With this configuration, the signal quality can be easily measured, and the angle range setting unit 8 can set an appropriate angle range using the relationship between the signal-to-noise power ratio and the angle range (for example, FIG. 9). For example, using the relationship shown in FIG. 9, it is possible to derive the relationship between the SNR and the angular range shown in FIG.

In addition, radio apparatus 100 according to the present embodiment receives radio-transmitted signal 30 using a plurality of antennas 0, 1, and 2 and uses direction estimation apparatus 500 to estimate the direction of the received signal. It is characterized by performing. With this configuration, it is possible to perform direction estimation in a wider angle range than the related art.

Embodiment 2.
The present embodiment discloses a mode in which the direction of a received signal can be smoothly estimated by controlling signal transmission.

As shown in FIG. 9, in the wireless device 100, the angle range in which the direction can be estimated is determined according to the signal quality. Therefore, in the present embodiment, a mode will be described in which wireless device 200 notifies terminal device 210 of control information so that direction estimation can be performed within a suitable angle range, and terminal device 210 transmits a signal based on the control information.

FIG. 13 shows the configuration of the wireless system according to the second embodiment. This wireless system includes a wireless device 200 and a terminal device 210. The terminal device 210 transmits the signal 30 shown in FIG. 3, the wireless device 200 receives the signal 30, and estimates the direction of the received signal.

FIG. 14 shows the configuration of radio apparatus 200 according to the second embodiment. In addition to the configuration of the first embodiment, wireless device 200 includes control information notification unit 10 that notifies terminal device 210 of control information. FIG. 15 shows the configuration of the terminal device 210 according to the second embodiment. The terminal device 210 includes an antenna 11, a signal transmitting unit 12 that transmits a signal, a transmission control unit 13 that sets a signal format or transmission power of a signal to be transmitted, and a control information receiving unit 14 that receives control information from the terminal device 210.

FIG. 16 is a flowchart showing the operation of this embodiment. In the present embodiment, the control information notification unit 10 of the wireless device 200 notifies the terminal device 210 of the control information necessary for the next signal transmission based on the signal reception results so far (S1601). There are various forms of control information to be notified. For example, the control information notification unit 10 may receive the quality information of the signal received so far from the signal quality calculation unit 7 and notify the terminal device 210 of the signal quality information. In another example, the control information notification unit 10 receives the information of the angle range set so far from the angle range setting unit 8 in addition to the signal quality information, and considers the angle range required for the next signal transmission. It is also possible to notify the required transmission power information. In this case, when the required angle range and the ratio r of the antenna spacing are determined, the required SNR is determined from the characteristic curve shown in FIG. The transmission power required to realize the required SNR is notified by the transmission power control information. Further, in another example, the control information notifying unit 10 can also notify the necessary signal format in consideration of the angle range required for the next signal transmission. Here, the signal format includes a spreading factor when the transmission signal is a spread signal, a chirp rate when the transmission signal is a chirp signal, and a configuration of the known signal when the transmission signal is a specific known signal. included. The method of notifying the signal quality information, the transmission power information, and the signal format information may be any known method.

When the terminal device 210 is notified of the control information, the control information receiving unit 14 receives the control information. The transmission control unit 13 of the terminal device 210 sets the transmission power or signal format suitable for the next transmission based on the received control information (S1602). Here, it is possible to notify, as the signal format, a spreading factor when the transmission signal is a spread signal and a chirp rate when the transmission signal is a chirp signal, and the terminal device 210 follows the notification to select an appropriate signal format. To set.

The terminal device 210 transmits a signal in the selected signal format (S1603). The wireless device 200 estimates the direction of the received signal (S1604). At this time, the direction estimation unit 9 of the wireless device 200 may use the direction estimation method described in the first embodiment or another direction estimation method. Further, the wireless device 200 can recognize the reception timing of the signal 30 from the outputs of the matched filters 4, 5, and 6, the wireless device 200 is notified in advance of the timing at which the terminal device 210 transmits, and the wireless device 200 It is also possible to configure the reception timing of the signal 30 from the notification information. Based on the output timing from the matched filters 4, 5, and 6, the direction estimation unit 9 can estimate the direction of the received signal.

Further, in the present embodiment, the configuration has been described in which wireless device 200 notifies terminal device 210 of control information, but a configuration in which control information is not notified can also be used. For example, the wireless device 200 transmits a known signal to the terminal device 210, and the terminal device 210 measures the SNR using the transmitted known signal, thereby roughly understanding the SNR obtained when the terminal device 210 transmits the signal. can do. By using the result, the terminal device 210 may perform transmission control by the transmission control unit 13 and transmit a signal.

In addition, although the terminal device 210 has been described as an example in the present embodiment, any wireless device may be used instead of the terminal device 210.

As described above, in the present embodiment, the wireless device 100 needs to estimate the direction of the signal transmitted from the terminal device 210, which is a wireless device, and received by the wireless device 100 (the wireless device 200), which is a receiving station. A transmission control unit 13 that determines the transmission power or the signal format, and a signal transmission unit 12 that transmits the signal in accordance with the transmission power or the signal format determined by the transmission control unit. It is characterized by With this configuration, it is possible to adjust the signal quality (for example, SNR) when performing the direction estimation in the wireless device 100 (the wireless device 200) according to the required angle range, and thus it is possible to reduce unnecessary transmission power. Further, by using a suitable signal format, it becomes possible to perform direction estimation within a required angle range.

Further, in the present embodiment, the signal received by radio apparatus 100 (radio apparatus 200) is a spread signal, and the signal format includes a spread rate of the spread signal. With this configuration, the terminal device 210 transmits a spread signal having a predetermined spreading rate, and the wireless device 100 (wireless device 200) despreads the spread signal using the matched filters 4, 5, and 6, whereby the wireless device It is possible to easily adjust the signal quality (for example, SNR) required when the direction estimation is performed by 100 (the wireless device 200).

Further, in the present embodiment, the signal received by wireless device 100 (wireless device 200) is a chirp signal, and the signal format includes a chirp rate of the chirp signal. With this configuration, the terminal device 210 transmits a chirp signal of a predetermined chirp rate, and the wireless device 100 (radio device 200) performs pulse compression of the chirp signal by using the matched filters 4, 5, and 6, whereby It is possible to easily adjust the signal quality (for example, SNR) required when the device 100 (radio device 200) performs direction estimation.

Embodiment 3.
In this embodiment, as a specific example of the analysis shown in the first embodiment, an example of an antenna arrangement capable of highly accurate direction estimation over a wide range is shown, and an antenna used for direction estimation is selected from a plurality of antennas. Embodiments will be described. Note that, although the case where three antennas are mainly used will be described below, the present embodiment is not limited to three antennas, and can be applied to any antenna of three or more antennas.

The state in which all directions (|φ|<=π/2) are within the range of direction estimation corresponds to the state of B=2 in Expression (3). Therefore, in order to maintain the success rate Preq in all directions, the equation (19) needs to satisfy B=2, and the antenna spacing d2 is restricted by the following equation.
d2 <= L(Γ, r)·λ/2 (20)
Here, λ represents the wavelength of the radio wave that carries the signal. From the discussion of (A5) in the first embodiment, it is possible to improve the direction estimation accuracy by widening the antenna intervals d1 and d2 while maintaining the expression (20). Therefore, the antenna spacing (d1, d2) that maintains the success rate Preq in all directions and obtains the highest estimation accuracy is given by the following equation.
(D1, d2)=(L(Γ,r)rλ/2, L(Γ,r)λ/2) (21)

An application example of Expression (21) will be shown. Taking the case of r=0.37 in FIG. 9 where L(Γ, r) is large,
L(Γ, 0.37)=2 Γ=10 dB (22)
=8 Γ=20 dB
=27 Γ=30 dB
And (d1, d2) in equation (21) is given by the following equation.
(D1, d2)=(0.37λ, λ) Γ=10 dB
(1.48λ, 4λ) Γ=20 dB
(4.995λ, 13.5λ) Γ=30 dB (23)
Further, the following equation holds for the estimation accuracy when the antenna arrangement of equation (23) is used.
γ | _SNR /γ | _{10 dB} = G _A · G _B (24)
G _A =L(Γ, 0.37) ² /L( ¹⁰ dB, 0.37) ²
G _B =σ ² | _{10 dB} /σ ² | _SNR
Here, ·| _SNR represents the value of the parameter · in the state where the SNR is given, G _A represents the accuracy improvement due to the widening of the antenna spacing, and G _B represents the accuracy improvement due to the reduction of the phase measurement error.

In FIG. 17, the antenna placement (d1, d2) that maintains the success rate Preq=0.99 in all directions at SNR Γ=10, 20, and 30 dB and obtains the highest estimation accuracy, and the estimation when the antenna placement is used The characteristics of accuracy γ and angle error are summarized. It can be seen from FIG. 17 that if the SNR is high, even if the antenna spacing is wider than a half wavelength, it is possible to perform highly accurate direction estimation over a wide range while maintaining a high success rate. Further, it can be seen that as the SNR becomes higher, the estimation accuracy is improved from both of the accuracy improvement G _A due to the widening of the antenna spacing and the accuracy improvement G _B due to the reduction of the phase measurement error.

FIG. 18 shows an antenna configuration in wireless device 300 of the present embodiment. In FIG. 18, in addition to the antennas 0, 1, and 2 included in the wireless device 100 described in the first embodiment, antennas 0'and 2'are provided. Here, the antenna distance between antenna 0 and antenna 1 is 0.37λ, the antenna distance between antenna 0 and antenna 2 is 1λ, the distance between antenna 0′ and antenna 1 is 1.48λ, and the distance between antenna 0′ and antenna 2′ is An example with 4λ is shown.

FIG. 19 shows the configuration of radio apparatus 300 of the present embodiment. The wireless device 300 includes an antenna selection unit 301 in addition to the configuration of the wireless device 100 described in the first embodiment. The antenna selection unit 301 selects which of the received signal from the antenna 0 and the received signal from the antenna 0'is used. Similarly, which of the received signal from the antenna 2 and the received signal from the antenna 2'is used is selected. It should be noted that, in a state where the signal is continuously transmitted in the signal quality calculation unit 7, the antenna selection unit 301 appropriately switches the antennas via the switches 302 and 303, so that the antennas 0, 0', 1, 2, 2' It is possible to measure all of the signal quality of.

In the present embodiment, the signal quality calculation unit 7 measures the signal quality of the antennas 0, 0′, 1, 2, 2′, and the antenna selection unit 301 uses the measured signal quality (for example, SNR) based on the measured signal quality. Select multiple antennas for direction estimation. For example, in the case of SNR Γ=10 dB, based on FIG. 17, the antenna arrangement that maintains the success rate Preq=0.99 in all directions and obtains the highest estimation accuracy is (d1, d2)=(0. 37λ, λ). Therefore, the antenna selection unit 301 selects the antennas 0, 1 and 2 in FIG. 18 and estimates the arrival direction of the signals using the received signals at the antennas 0, 1 and 2. Further, in the case of SNR Γ=20 dB, based on FIG. 17, the antenna arrangement that maintains the success rate Preq=0.99 in all directions and obtains the highest estimation accuracy is (d1, d2)=(1. 48λ, 4λ). Therefore, the antenna selection unit 301 selects the antenna 0', 1, 2'in FIG. 18 and estimates the arrival direction of the signal using the received signals at the antennas 0', 1, 2'. In this way, the antenna selection unit 301 selects a plurality of antennas to be used for direction estimation based on the measured signal quality (for example, SNR), so that the success rate Preq in all directions is obtained under each signal quality. =0.99 is maintained, and the direction can be estimated with high estimation accuracy. In addition, by selecting an antenna and performing direction estimation, it is possible to perform signal processing with a small amount of calculation using received signals from a small number of antennas. Although the case where the direction estimation is performed in all directions has been described here, the direction estimation need not necessarily be performed in all directions. Further, although the case where the success rate Preq=0.99 is taken up, the success rate may be any other value. Any antenna may be selected as the antenna.

As described above, according to the present embodiment, an antenna for radio apparatus 300 to select an antenna used for direction estimation from a plurality of antennas included in radio apparatus 300 according to the signal quality calculated by signal quality calculation unit 7. The selecting unit 301 is provided. With this configuration, it is possible to perform the direction estimation of the signal with high estimation accuracy while maintaining a predetermined success rate within the angle range in which the direction estimation is performed according to the signal quality.

Further, although the configuration in which the antenna is selected has been described so far, the same object can be achieved by the configuration in which the antenna is moved instead of selecting the antenna. That is, instead of selecting the antenna from the antennas 0 and 0', one antenna may be moved to one of the antenna 0 and the antenna 0'. In this case, the wireless device 300 includes an antenna movement control unit that moves the plurality of antennas 0, 1 and 2 to a position determined by the signal quality calculated by the signal quality calculation unit 7 instead of the antenna selection unit 301. With this configuration, as in the case of selecting an antenna, it is possible to perform direction estimation of a signal with high estimation accuracy while maintaining a predetermined success rate within an angle range in which direction estimation is performed according to signal quality. Becomes

Fourth Embodiment
In the present embodiment, in the first to third embodiments, different wireless devices perform transmission and reception, whereas in the present embodiment, one wireless device performs signal transmission and signal reception. Indicates.

When performing wireless communication, the wireless device 200 and the terminal device 210 are usually different wireless devices as described in the second embodiment. On the other hand, when measuring the moving speed of the measuring object, one wireless device 400 transmits a signal 30 and the same wireless device 400 receives the signal 30 reflected by the measuring object 2001 as shown in FIG. The wireless device 400 can estimate the arrival direction of the signal 30 reflected by the measurement target.

FIG. 21 shows the configuration of radio apparatus 400 according to the present embodiment. Wireless device 400 includes a transmission control unit 21 and a signal transmission unit 22 in addition to the configuration of wireless device 100 described in the first embodiment.

FIG. 22 shows a flowchart showing the operation of radio apparatus 400 according to the present embodiment. In the present embodiment, the transmission control unit 21 of the wireless device 400 determines the control information necessary for the next signal transmission based on the signal reception result so far, and signals to transmit the signal based on the control information. The transmitter 22 is controlled (S2201). There are various forms of control information. For example, the transmission control unit 21 receives the signal quality of the signal received so far from the signal quality calculation unit 7, further receives the information of the angle range set up to now from the angle range setting unit 8, and in the next signal transmission. Determine the required transmit power or signal format, taking into account the required angular range. More specifically, when the required angle range is determined, the required SNR is determined from the characteristic curve shown in FIG. The transmission power and signal format required to realize the required SNR are determined. The signal transmitter 22 transmits the signal 30 according to the control information determined by the transmission controller 21 (S2202). The signal 30 transmitted from the wireless device 400 is reflected by the measurement target 2001, and the reflected wave is received by the wireless device 400 (S2203). The wireless device 400 estimates the direction of the received signal as in the first to third embodiments (S2204), and detects the direction of the measurement target 2001.

As described above, in the present embodiment, one wireless device transmits and receives a signal and estimates the direction of the received signal.

That is, the wireless device 400 according to the present embodiment estimates the directions of the signals transmitted from the device itself, reflected by the measurement target 2001, and received by the device itself within the angular range required by the wireless device 100. A transmission control unit 21 that determines transmission power or a signal format, and a signal transmission unit 22 that transmits a signal according to the transmission power or the signal format determined by the transmission control unit 21 are provided. And With this configuration, it is possible to estimate the direction of the measurement target 2001 by using the transmission power or the signal format required according to the existing direction and the moving speed of the measurement target 2001, and reduce unnecessary transmission power. Is possible. Further, by using the signal 30 having a suitable signal format, it is possible to estimate the direction in a wide angle range.

Embodiment 5.
The fifth embodiment shows one mode of adjusting the transmission power or the signal format of the signal at the time of signal transmission in the second to fourth embodiments.

FIG. 23 shows how the direction is estimated at each time in this embodiment. As shown in the second to fourth embodiments, the angle range in which the direction can be estimated differs depending on the received power and the signal format of the signal received by wireless device 200. On the other hand, the arrival direction of a signal usually changes continuously in time.

In consideration of such characteristics, in the present embodiment, the terminal device 210 transmits a signal having the signal format/transmission power of standard J at times p1 and p4, and the signal format/signal at the times p2, p3, p5, and p6. A signal having a transmission power of standard K is transmitted. Here, with the standard J signal, it is possible to estimate the direction in a wider angle range than with the standard K signal. This signal transmission can be performed by determining the signal format/transmission power in the control information notification unit 10 (FIG. 14) or the transmission control 13 (FIG. 15) in the second embodiment.

As shown in FIG. 23, when this signal transmission is performed, the direction of the signal can be estimated from the wide angle range 23012302 at the times p1 and p4. At times p2, p3, p5, and p6, the received signals are received in angle ranges 2303, 2304, 2305, and 2306 narrower than the angle range obtained at times p1 and p4 with the direction estimated at times p1 and p4 as the central direction. Direction estimation is performed.

If the change in the direction of the received signal from the time p1 to the time p2 is within ½ of the angular range set at the time p2, the direction can be estimated at the time p2 without error. Similarly, if the change in the direction of the received signal from the time p1 to the time p3 is within 1/2 of the angular range set at the time p3, the direction can be estimated without error at the time p3.

As the time elapsed from the time p1 increases, the possibility that the signal arrival direction changes will increase. Therefore, the standard J signal is transmitted again at time p4 to perform direction estimation in a wide angle range 2302. Here, when the same standard J is used, the angle range 2301 and the angle range 2302 are the same range.

That is, in the present embodiment, when the angular range in the signal existing direction is wide, a transmission signal of standard J is transmitted, and when it is known that the angular range in the signal existing direction is a limited range, A standard K signal is transmitted. If the characteristics that the arrival direction changes are known, the temporal pattern for transmitting the standard J or standard K signal can be determined in advance. Moreover, the standard of the transmission power and the signal format of the transmission signal to be transmitted next can be determined depending on which position in the set angle range the direction estimated by the direction estimation unit 9 belongs to.

In the standard K, the angle range in which the direction can be estimated is narrower than that in the standard J, and normally, the transmission power of the standard K signal is smaller than that of the standard J signal. Therefore, it is possible to estimate the direction of the received signal while suppressing the transmission power as compared with the case where the direction of the standard J is always used to estimate the direction in a wide angle range. As described above, by adaptively using signals of a plurality of standards, it is possible to reduce power consumption while maintaining appropriate direction estimation performance. As a result, it is possible to suppress the interference with surrounding wireless stations.

Further, the direction estimation device 500 according to the present embodiment sets the first angular range 2301 at the first time p1, and the first angular range at the second time p2 that is later than the first time p1. A second angle range 2303 narrower than 2301 is set. With this configuration, the arrival direction of the signal is estimated in a wide range at the first time point p1 and the information of the direction estimated at the first time point p1 is used at the second time point p2 to obtain the first angular range 2301. Even if the second angle range 2303 that is narrower than that is set, the direction estimation of the signal can be smoothly performed. Further, by narrowing the angle range, the power of the signal required for the direction estimation can be suppressed, and the power required for the signal transmission can be suppressed.

Further, when the same standard J is used, the angle range 2301 and the angle range 2302 are both the same first angle range, and the direction estimation device 500 according to the present embodiment is configured such that the angle range setting unit 8 causes the angle range setting unit 8 to set the first and second angles. The first angle range is set at a third time p4, which is later than the second times p1 and p2. With this configuration, it is possible to perform direction estimation in a wide range only at the time when direction estimation in a wide angle range is required, so that the direction estimation capability in a wide range can be suppressed while suppressing the power required for signal transmission. It can be maintained at the agency time.

Sixth Embodiment
In this embodiment, as a specific example of the control shown in the fifth embodiment, an example of a mode in which a spread signal is used as the signal 30 and the spread rate of the spread signal is determined as a signal format is disclosed.

First, a control configuration when performing direction estimation in a wide angle range at times p1 and p4 will be described. As shown in FIG. 17, a high SNR Γ is required to perform highly accurate direction estimation over a wide range. Here, SNR Γ is the SNR at the output of the matched filter, and even if the SNR before the input of the matched filter is low, if a high SNR can be obtained at the output of the matched filter, highly accurate direction estimation can be performed in a wide range. Therefore, in order to improve the SNR at the output of the matched filter, the spread signal is used as the signal 30. As a specific example, the following usage environment is assumed when the antenna spacing is (d1, d2)=(1.48λ, 4λ).
Usage environment)
Spreading rate of spreading signal: SF1=100
Before matched filter input: SNR=0 dB
After output of matched filter: SNR Γ=20 dB

In this usage environment, SNR=20 dB can be secured by the matched filter output, and the wireless device 200 can perform highly accurate direction estimation in all directions. As described above, by using the spread signal having a high spread rate as the signal 30, even in an environment where the SNR before inputting the matched filter is low, highly accurate direction estimation can be performed in a wide range. In the fifth embodiment, this control can be realized by setting the signal format of the standard J to the spread signal with the spreading factor SF1=100.

At time p1 (p4), when the direction estimation for all directions is performed, the wireless device 200 can grasp the direction φ1 of the terminal device 210. In the subsequent direction estimation at the times p2 and p3 (p5, p6), it is necessary to detect the existing direction of the terminal device 210 after movement around the direction φ1. Therefore, the estimation range of F=sin φ in the direction estimation at the times p2 and p3 is set as follows.
-B'/2+sinφ1 <=F<=B'/2+sinφ1 (25)
Here, the range B′ is preset in the wireless device 200 in consideration of the movement characteristics of the terminal device 210.

In this direction estimation, the estimation range in (A2) and (A3) is -B/2 <=F <=B/2 (26)
Corresponds to the direction estimation in which is replaced by the equation (25). In that case, the operation is represented by equations (10), (16) and (17)
It can be analyzed by replacing B/2 in B with B′/2+sin φ1.

In FIG. 24, in the case of Preq=0.99, SNR=10, 20, 30 dB, and the ratio r=0.37, the maximum value L(Γ,r) of B′/B2 that can be obtained by using the equation (25) is shown. A transition with respect to sin φ1 is shown. From the figure, L(Γ, r) does not change even if sin φ1 changes from −1 to 1. Although the case of r=0.37 has been taken up here, r=0.1, 0.2,. ． ． , 0.9, L(Γ, r) is constant regardless of sin φ1. In this way, the direction-estimable range B'is constant regardless of the direction φ1. Therefore, if φ1=0 is set, the equation (25) has the same format as the equation (26), and the analysis performed in (A3) and (A4) can be applied to the range B′ as it is.

Therefore, in the direction estimation at the times p2 and p3 (p5, p6), the following processing is performed.
(S1) The wireless device 200 determines the range B′ so that the direction of the terminal device 210 is within the range of Expression (25).
(S2) The wireless device 200 determines an SNR Γ that satisfies the following equation so that the success rate Preq=0.99 can be maintained in the range B′.
B'/B2<=L(Γ,r)
(S3) The wireless device 200 determines the spreading factor SF2 required to achieve the SNR Γ and notifies the terminal device 210 of the spreading factor SF2.
(S4) The terminal device 210 transmits a spread signal with the spreading factor SF2, and the wireless device 200 performs direction estimation within the range of Expression (25).

As a specific example, the following usage environment is assumed when the antenna spacing is (d1, d2)=(1.48λ, 4λ).

Usage environment) Estimated range: B'=1/2
(-1/4+sinφ1<=sinφ<=1/4+sinφ1)
Before matched filter input: SNR=0 dB
After output of matched filter: SNR Γ=10 dB
Spreading factor of known signal: SF2=10

Here, SNR Γ=10 dB, B2=λ/d2=1/4 ⇒ B′/B2=2
⇒ 2 <= L (Γ, 0.37)
And derived from FIG. In the fifth embodiment, this control can be realized by setting the signal format of the standard K to the spreading signal of spreading factor SF2=10.

In this way, the terminal device 110 transmits the spread signal in accordance with the spreading factor determined by the wireless device 200, so that the wireless device 200 can perform direction estimation within a necessary angular range.

Embodiment 7.
In the above embodiments, the signal quality calculation unit 7 measures the signal quality, but this embodiment discloses a mode in which the signal quality calculation unit 7 predicts the signal quality.

In the above embodiments, the signal quality calculation unit 7 directly measures the signal quality of the received signal. However, in some cases, the signal quality of the received signal can be predicted without directly measuring the signal quality of the received signal. For example, if SNR Γ1 is measured as the signal quality at the first signal reception and the power difference cn between the n (=2, 3,...) Received signal and the first received signal and the signal is grasped, SNR of the received signal of
Γ1×cn
Can be predicted as The power difference information cn can be grasped if the difference in power of the transmission signals is known.

For example, in FIG. 20, since the wireless device 400 transmits a signal, it is possible to grasp the power difference cn between the n (=2, 3,...) Received signal and the first received signal. By using this information, it is possible to predict the signal quality of the received signal without measuring the signal quality of the received signal directly after measuring SNR Γ1 as the signal quality at the first signal reception.

As described above, in the present embodiment, the signal quality calculation unit 7 predicts the signal quality. That is, in the first to sixth embodiments so far, the process of measuring the signal quality by the signal quality calculating unit 7 is replaced with the process of predicting the signal quality. With this configuration, the signal quality can be calculated without having to measure the signal quality every time the signal is received. Moreover, since the signal quality of the received signal can be predicted before the signal is received, the angle range can be set in advance by the angle range setting unit 8, and the processing after the signal reception can be smoothly performed. Become.

0, 0', 1, 2, 2': antenna, 4, 5, 6: matched filter, 7: signal quality calculation unit, 8: angle range setting unit, 9: direction estimation unit, 10: control information notification unit, 11: antenna, 12: signal transmitter, 13: transmission controller, 14: control information receiver, 21: transmission controller, 22: signal transmitter, 30: signal, 51: amplitude, 52: noise, 100: wireless Device, 110: terminal device, 200: wireless device, 210: terminal device, 300: wireless device, 301: antenna selection unit, 302, 303: switch, 400: wireless device, 500: direction estimation device, 1001: main lobe, 1002: side lobe, 1003: grating lobe, 1004: gain difference, 1005, 1006: angle range, 1101: processing circuit, 1201: processing circuit, 1202: memory, 2001: measurement object, 2301, 2302, 2303, 2304, 2305, 2306: Angle range

Direction estimation device according to the present invention, a signal quality calculation unit that measures or predicts the quality of the signal received using a plurality of antennas, depending on the quality of the signal measured or predicted by the signal quality calculation unit, An angle range setting unit that sets an angle range for estimating the arrival direction of the signal, and a direction estimation unit that estimates the arrival direction of the signal in the angle range set by the angle range setting unit, and the quality is It is characterized in that it depends on the degree of noise contained in the received signal .

Claims (11)

A signal quality calculation unit that measures or predicts the quality of signals received using a plurality of antennas,
An angle range setting unit that sets an angle range for estimating the arrival direction of the signal according to the quality of the signal measured or predicted by the signal quality calculation unit,
A direction estimation unit that estimates the arrival direction of the signal in the angle range set by the angle range setting unit,
A direction estimating device comprising: The direction estimation apparatus according to claim 1, wherein the signal quality calculation unit measures or predicts a signal-to-noise power ratio of the signal as the quality. The angle range setting unit sets a first angle range at a first time, and sets a second angle range narrower than the first angle range at a second time later than the first time. The direction estimation device according to claim 1 or 2, wherein The direction estimation device according to claim 3, wherein the angle range setting unit sets the first angle range at a third time later than the second time. A wireless device, which receives a wirelessly transmitted signal using the plurality of antennas, and performs direction estimation for the signal using the direction estimating device according to claim 1. .. Depending on the quality of the signal measured or predicted by the signal quality calculation unit,
An antenna selection unit that selects an antenna used for direction estimation from the plurality of antennas,
The wireless device according to claim 5, further comprising: An antenna movement control unit that moves the plurality of antennas to a position determined by the quality of the signal measured or predicted by the signal quality calculation unit,
The wireless device according to claim 5, further comprising: The estimation of the direction of the signal transmitted from the own device and received by the receiving station is performed within the angle range required by the receiving station, and a transmission control unit that determines the transmission power or the signal format,
According to the transmission power or signal format determined by the transmission control unit, a signal transmission unit for transmitting a signal,
A wireless device comprising: The signal received at the receiving station is a spread signal,
9. The wireless device according to claim 8, wherein the signal format includes a spreading factor of the spread signal. The signal received at the receiving station is a chirp signal,
9. The wireless device according to claim 8, wherein the signal format includes a chirp rate of the chirp signal. Including the receiving station,
The wireless device according to claim 8, wherein the receiving station receives a signal in which the transmitted signal is reflected by an object to be measured.

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