JP2000147083A - Method and apparatus for measuring arrival angle - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and apparatus for measuring the arrival angle, wherein the downsizing and a low power consumption can be realized and there is no need to eliminate the influence of the mutual coupling between antennas. SOLUTION: An antenna 20, a baseband signal generator 21, a reverse modulator circuit 22, a serial-parallel converter 23 and an arrival angle estimating circuit 24 are provided, the antenna is moved at a fixed velocity v at a fixed angle with respect to arrival wave, a signal received by the antenna 20 for every prescribed time Ts is converted (21) into a baseband signal, oppositely modulated (22), and converted (23) into a parallel signal, the parallel signal received every time Ts is regarded as a signal received by a plurality of antennas disposed with fixed spacings d and the direction of the arrival wave, is measured in the arrival angle estimating circuit 24.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an angle-of-arrival measuring method and an angle-of-arrival measuring device, and more particularly to an angle-of-arrival measuring method and an angle-of-arrival measuring device for measuring the angle of arrival of an incoming wave in digital mobile communication or the like. is there.

[0002]

2. Description of the Related Art In digital mobile communications, it is important to increase the number of frequency channels by effectively utilizing frequencies in order to meet rapidly increasing demand. In order to spatially use frequency effectively in the cellular system,
It is necessary to shorten the frequency repetition distance. However, when the frequency repetition distance is shortened, the power of co-channel interference increases, which causes a significant deterioration in transmission characteristics.

Therefore, co-channel interference countermeasures have become important. In recent years, introduction of an adaptive array, which is a type of interference canceller, has been studied as co-channel interference countermeasures. The adaptive array removes interference waves by adaptively controlling the directivity of the antenna. In order to operate this adaptive array effectively, it is necessary to design parameters according to an actual moving propagation path. In particular, information on the angle of arrival of the arriving wave is important in design, and it is necessary to measure the angle of arrival.

For this measurement, MUSIC (Multiple
Signal Classification) algorithm (Subspace-Based method) or MVDR (Minimum Vacuum
It has been considered to use a beamforming method such as a riance distortionless response (Algorithm) algorithm for the estimation algorithm. Here, the eigen-expansion method, which requires a large amount of computation but has excellent estimation accuracy, particularly the MUSIC algorithm will be described.

FIG. 1 shows a conventional angle-of-arrival measuring device using the MUSIC algorithm, and its operation will be described. In addition,
Here, the number of antennas is L (L is a natural number of 2 or more).
First, the received wave received from the antenna # 1 is input to the input terminal Rin
1 and input to the baseband signal generator # 1.
The signal is converted from the frequency band to the baseband and output from the output terminal Bout1 as a received baseband signal. Similarly, a received signal received from another antenna is input to a corresponding baseband signal generator, converted into a baseband, and output as a received baseband signal.

The angle-of-arrival estimating circuit 5 estimates the angle of arrival of a radio wave with these received baseband signals as inputs, and outputs an estimated value of the angle of arrival to an output terminal. Next, the configuration of the baseband signal generator of FIG. 1 is shown in FIG. 2 and its operation will be described. First, a received wave received from the n-th (1 ≦ n ≦ L) antenna is input from the input terminal Rin, is amplified by the low noise amplifier 10, and is branched by the hybrid 11.
One signal is input to the low-pass filter 16 after being multiplied by the multiplier 12 by the carrier signal output by the carrier signal generator 15. Then, the signal is sampled by the A / D converter 18 every sampling period Ts and converted into a digital signal. The other signal branched by the hybrid 11 is multiplied by the multiplier 13 with the carrier signal rotated by 90 degrees in the phase shifter 14, input to the low-pass filter 17, and then sampled by the A / D converter 19. , Are converted to digital signals. The outputs of the A / D converters 18 and 19 are combined and output from the output terminal Bout.
The operation in FIG. 2 is quasi-synchronous detection (detection of the same frequency but different phases), and the outputs of the A / D converters 18 and 19 correspond to the in-phase and quadrature components of the quasi-synchronous detection signal. And the received baseband signal x _n (i)
And Hereinafter, all the baseband signals are represented by a complex representation in which the in-phase component is the real part and the quadrature component is the imaginary part, and i means time iTs and is an integer indicating the i-th sampling point. Also, unless otherwise specified, the sampling period Ts
Is equal to the symbol period T of the transmission modulation wave.

Next, the operation of the angle-of-arrival estimation circuit 5 of FIG. 1 will be described. First, the received baseband signals x ₁ (i) to x
_L (i) is input to the arrival angle estimation circuit 5. An L-dimensional received signal vector X having the received baseband signal as an element
(i) is defined as follows.

[0008]

(Equation 1)

A covariance matrix R (i) of the received signal vector X (i) is obtained based on a time average as in the following equation.

[0010]

(Equation 2)

Here, exponential weighting time averaging is performed, and a forgetting coefficient λ _c (0 <λ _c ≦ 1) is introduced. β _i is a normalization constant, which is a reciprocal of the actual observation time as shown in Expression (3). This covariance matrix R (i) is eigen-expanded, and its eigenvectors are expressed as {e ₁ , e ₂ ,..., E _L },
Let the corresponding eigenvalues be {α ₁ , α ₂ ,..., Α _L }. R (i) is a Hermitian matrix, and the eigenvectors are vectors orthogonal to each other. In addition, the eigenvalues are all positive real numbers, and numbers are assigned in descending order. This eigenvalue has the following properties.

Α ₁ >> α _D >> α _{D + 1} =... Α _L = σ _n ² (4) where D is the number of arriving waves and σ _n ² is the average power of the noise signal. The magnitudes of the eigenvalues up to the Dth are about the signal power of the arriving wave, and the eigenvalues after the (D + 1) th are equal to the average power of the noise signal. Here, the eigenvectors corresponding to the eigenvalues up to the D-th are represented by the eigenvectors in the signal space, D + 1
The eigenvectors corresponding to the eigenvalues after the th are referred to as eigenvectors in the noise space. It is known that the eigenvectors of this noise space are almost orthogonal to the array response vector of the arriving wave (Simon Haykin, Pren
tice-Hall Publishing, Adaptive Filter Theory 2nd edition,
(See Chapter 12).

The array response vector will be described by taking a linear array having an antenna interval d shown in FIG. 3 as an example. In this figure, it is assumed that a plane wave having an arrival angle φ has arrived. The arriving wave of antenna # 2 is antenna #
2πd cosφ with the path difference dcosφ for the incoming wave of 1
The / λ (λ: wavelength of radio wave) phase is advanced. Below,
It is assumed that the delay time caused by the path difference is negligible as compared with the symbol period T of the transmission modulation wave. Therefore, the difference between the received waves of the antenna # 1 and the antenna # 2 is only the phase difference caused by the path difference. Similarly, the n-th (1 ≦ n ≦
The arriving wave of the (L) th antenna #n has a phase advance of 2π (n-1) dcosφ / λ with respect to the arriving wave of antenna # 1, and the difference between the received waves of antenna # 1 and antenna #n Is only this phase difference. A vector having these relative phase differences as elements is an array response vector A
(Φ)

[0014]

(Equation 3)

## EQU1 ## Here, j is an imaginary unit. In order to make the arrival angle estimation work well, the antenna interval d needs to be λ / 2 or less. Since the eigenvector in the noise space is almost orthogonal to the array response vector of the arriving wave, the arrival angle of the arriving wave can be estimated by finding the angle of arrival φ satisfying the following equation.

[0016]

(Equation 4)

Therefore, the MUSIC algorithm obtains the angle of arrival φ at which S (φ) defined by the following equation becomes a peak,
This is an estimated value of the angle of arrival.

[0018]

(Equation 5)

Although the denominator of equation (8) is substantially zero, a solution can be obtained without actually diverging when the solution is actually obtained. Also, it is clear from equation (8). In this algorithm, D <L must be satisfied, and the number of arriving waves that can be estimated is the number of antennas minus one (in FIG.
1).

[0020]

The conventional angle-of-arrival measuring instrument described above requires a plurality of antennas.
Therefore, a plurality of receiving systems, that is, a plurality of baseband signal generators are required. The baseband signal generator is an analog circuit, and unlike a digital circuit, it is difficult to save power and reduce the size, and the power consumption and volume of the measuring device become enormous. In order to increase the estimation accuracy of the number of arriving waves and the angle of arrival that can be estimated, the number of antennas must be further increased, and the power consumption and the volume are further increased. In addition, there is a signal leakage between the antennas, that is, an effect of mutual coupling, and a function for eliminating this effect is required.

As described above, the conventional angle-of-arrival measuring apparatus requires a plurality of antennas, the power consumption and volume of the receiver become enormous, and the influence of mutual coupling between antennas must be eliminated. There was a problem. The present invention has been made in view of the above problems, and provides an angle of arrival measuring method and an angle of arrival measuring device that can be reduced in size and power consumption and that does not need to eliminate the influence of mutual coupling between antennas. It is intended for.

[0022]

According to the first aspect of the present invention, there is provided an antenna, a receiving means for receiving a signal connected to the antenna, and an arrival angle estimation for estimating a signal arrival direction. An arrival angle measuring method for measuring the direction of an arriving wave using the means 24, comprising: moving the antenna at a constant speed with a constant angle with respect to the arriving wave; Means for converting a serial reception signal received every predetermined time into a parallel signal, the parallel reception signal is regarded as a reception signal received by a plurality of antennas provided at regular intervals, and the arrival angle estimation means Is a method for measuring the direction of an incoming wave.

According to the first aspect of the present invention, the serial reception signal received by the antenna and the reception means at predetermined time intervals is converted into a parallel signal, and the parallel reception signal is provided at regular intervals. By measuring the direction of the arriving wave assuming that it is a received signal received by a plurality of antennas, it is possible to reduce the size and power consumption, and to achieve a method of measuring the angle of arrival that does not require removing the influence of mutual coupling between antennas. Can be provided.

According to a second aspect of the present invention, there is provided an arrival angle measuring method for measuring a direction of an incoming wave based on an eigen-expansion method or a beam forming method, wherein one antenna 20 and one reception apparatus connected to the antenna are provided. Means 21 are provided,
Having a certain angle with respect to the incoming wave, moving the antenna at a certain speed, and converting a serial reception signal for each predetermined time Ts received by the antenna and the receiving means into a parallel signal, The method is characterized in that the parallel received signals are regarded as received signals received by a plurality of antennas provided at a fixed interval d, and the direction of the incoming wave is measured based on the eigen expansion method or the beam forming method.

According to the second aspect of the present invention, the antenna is moved, the serial reception signal received by the antenna for every predetermined time Ts is converted into a parallel signal, and the parallel reception signal is converted at a constant interval d. By measuring the direction of the arriving wave based on the eigen expansion method or the beam forming method assuming that the signals are received by a plurality of provided antennas, miniaturization and low power consumption can be achieved, and mutual coupling between antennas can be achieved. It is possible to provide a method of measuring the angle of arrival that does not need to eliminate the effect of the angle of arrival.

According to a third aspect of the present invention, in the arrival angle measuring method according to the first or second aspect, the predetermined time is set to T.
where s, v is the moving speed of the antenna, and λ is the wavelength of the radio wave, vTs / λ ≦ 0.5.
According to the third aspect of the invention, by setting vTs / λ ≦ 0.5, the arrival angle can be estimated well.

According to a fourth aspect of the present invention, there is provided an angle-of-arrival measuring device provided on a mobile body, comprising: a receiving unit 21 for converting a received signal from one antenna 20 into a baseband and outputting a received baseband signal; An inverse modulation unit 22 that inversely modulates the received baseband signal using a known signal sequence and outputs an inversely modulated signal, performs serial / parallel conversion using the inversely modulated signal as an input, and outputs an inversely modulated parallel signal. Serial / parallel conversion means 23, vehicle speed measurement means 25 for measuring and outputting the speed of a moving object, and arrival angle for estimating and outputting the angle of arrival of a radio wave by using the inversely modulated parallel signal and the speed of the moving object as inputs. It is characterized by comprising estimating means 24.

According to a fifth aspect of the present invention, there is provided an angle-of-arrival measuring device provided on a mobile body, comprising a receiving means 21 for converting a received signal from one antenna 20 into a baseband and outputting a received baseband signal. A serial-to-parallel conversion unit 23 that performs serial-parallel conversion using the reception baseband signal as an input and outputs a reception baseband parallel signal, a vehicle speed measurement unit 25 that measures and outputs the speed of a moving object, It is characterized by comprising an angle-of-arrival estimating means 24 for estimating and outputting an angle of arrival of a radio wave by using a baseband parallel signal and the speed of the moving object as inputs.

According to a sixth aspect of the present invention, in the angle-of-arrival measuring apparatus according to the fourth or fifth aspect, the angle-of-arrival estimating means is based on an eigenexpansion method or a beamforming method.
It is characterized in that arrival angle estimation is performed. The invention according to claims 4 to 6 is an arrival angle measurement device capable of measuring an arrival angle by the arrival angle measurement method according to claims 1 to 3.

[0030]

Next, embodiments of the present invention will be described with reference to the drawings. [First Embodiment] FIG. 4 shows the configuration of the first embodiment of the present invention. A received wave from one antenna 20 is input to a baseband signal generator 21. Here, the baseband signal generator (receiving means) 21 is the same as that shown in FIG. Baseband signal generator 21
The received baseband signal x (i) output from is input to an inverse modulation circuit (inverse modulation means) 22. The transmission signal sequence is known on the receiver side, and using this known signal sequence b (i),
x (i) is inversely modulated and the modulated component is removed, and then the inversely modulated signal
Output as y (i). Note that this inverse modulation operation is equivalent to x (i)
This is equivalent to dividing by b (i). This inverse modulation signal y
(i) is input to a serial / parallel conversion circuit (serial / parallel conversion means) 23, and L parallel signals are output. An L-dimensional vector Y (i) having the parallel signal as an element is determined as follows.

[0031]

(Equation 6)

Arrival angle estimation circuit (arrival angle estimation means) 24
Receives the inverse-modulated parallel signal as an input.
By substituting the L-dimensional received signal vector X (i) determined by the above with Y (i), the arrival angle of the incoming wave can be estimated using the MUSIC algorithm described in the related art. This will be described with reference to FIG. In the figure, it is assumed that a moving body equipped with the configuration of the first embodiment moves at a speed v, and a plane wave having an arrival angle φ with respect to the speed direction has arrived. It is assumed that the moving body at the point A reaches the point B after Ts seconds.
The reception wave at this time is advanced as compared with the reception wave at the point A. Since the path difference is vTscosφ, 2πvTsc
The osφ / λ phase is advanced. This situation is equivalent to the situation shown in FIG. 3 if the correction is performed by the inverse modulation operation so that the change of the received wave due to the time difference of Ts is eliminated. Therefore, X
If (i) is replaced by Y (i) and the antenna interval d is replaced by vTs, the arrival angle of the incoming wave can be estimated using the MUSIC algorithm described in the related art. In order to make the arrival angle estimation work well, the antenna interval d is set to λ /
Since vTs / λ needs to be 2 or less, vTs / λ must be 0.5 or less.

As described above, the arrival angle estimation circuit 24 in FIG.
With the inverse-modulated parallel signal and the speed of the moving object output from the vehicle speed measurement circuit 25 as inputs, the arrival angle of an incoming wave is estimated, and the estimated value is output to an output terminal. Computer simulation was performed to examine the characteristics of the present embodiment. FIG. 6 shows the result. Here, the transmission signal is QPSK modulation, CNR is 30 dB, vTs / λ is 0.5, and L in equation (9) is 7. The incoming waves were three waves, and the angles of arrival were 45, 90, and 135 degrees with respect to the speed direction of the moving body. Case 1 is a case where the delay times of these arriving waves are 0 and all are equal. Case 2 is a case where only the 135 ° arriving wave is delayed by 1T due to the influence of multipath or the like.
Indicates that the incoming waves at 45, 90, and 135 degrees are 0,
This is the case where the delay is 1T and 2T. In the figure, the horizontal axis is the arrival angle candidate φ, and the vertical axis is S (φ) determined by Expression (8). In case 1, peaks occur at 45, 90, and 135 degrees, but in case 2 and case 3, peaks occur at different locations. This is because when incoming waves having different delay times arrive due to the influence of multipath or the like, the correction of the received wave by the inverse modulation operation cannot be completely performed. [Second Embodiment] In order to solve this problem, a transmission signal may be transmitted such that a reception signal for each sampling period Ts does not fluctuate with time. For example, the transmission signal sequence may be set to a constant value (for example, “111... 1”). In the case of such a transmission signal, the correction of the received wave by the inverse modulation operation becomes unnecessary. An embodiment in this case is shown in FIG. Here, the point different from the first embodiment of FIG. 4 is that there is no inverse modulation circuit, and the output signal of the reception baseband signal generator 21 is directly input to the serial / parallel conversion circuit 23 and the arrival angle estimation circuit 24 The point is that a reception baseband parallel signal is supplied.

FIG. 8 shows a computer simulation result of the second embodiment. Simulation conditions are shown in FIG.
This is the same as in the first embodiment, and good results are obtained in case 3 which has deteriorated in the first embodiment. Although the MUSIC algorithm has been described as an example of the angle-of-arrival estimation algorithm here, ESPRIT (Estimation of Signal
Parameters Via Rotational Invariance Techniqu
es) and algorithms such as MVDR can also be applied. Also,
The sampling period Ts can take a value other than the modulation symbol period T in a range where vTs / λ is 0.5 or less.

As described above, the angle of arrival of the arriving wave can be estimated based on the signal received from one antenna and the speed of the moving body, so that a plurality of antennas and receivers are not required.
The power consumption and volume of the receiver can be reduced,
Since there is only one antenna, there is no mutual coupling between antennas, and an operation for removing the influence of mutual coupling between antennas is not required.

In particular, it is effective to use the present invention in a radio system in which co-channel interference cannot be ignored.

[0037]

According to the present invention as described above, the following various effects can be realized. According to the first to third aspects of the present invention, the antenna is moved, the serial reception signal received by the antenna for each predetermined time Ts is converted into a parallel signal, and the parallel reception signal is provided at a constant interval d. By measuring the direction of the arriving wave based on an algorithm such as the eigen-expansion method or the beamforming method assuming that the signals are received by a plurality of antennas received, the size and power consumption can be reduced, and An arrival angle measurement method that does not need to eliminate the influence of mutual coupling can be provided.

In particular, according to the third aspect of the present invention, vT
By setting s / λ ≦ 0.5, it is possible to satisfactorily estimate the angle of arrival. According to the invention described in claims 4 to 6, the antenna is moved, the serial reception signal received by the antenna for each predetermined time Ts is converted into a parallel signal, and the parallel reception signal is provided at a constant interval d. By measuring the direction of the arriving wave based on an algorithm such as the eigen-expansion method or the beamforming method assuming that the signals are received by a plurality of antennas received, the size and power consumption can be reduced, and It is possible to provide an angle-of-arrival measuring instrument that does not need to eliminate the influence of mutual coupling.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a conventional angle of arrival measuring device.

FIG. 2 is a diagram for explaining a configuration of a baseband signal generator of FIG. 1;

FIG. 3 is a diagram showing a relationship between a linear array and a plane wave.

FIG. 4 is a diagram showing a configuration diagram of a first embodiment of the present invention.

FIG. 5 is a diagram illustrating a relationship between a moving object and a plane wave.

FIG. 6 is a diagram illustrating a computer simulation result according to the first embodiment of this invention. .

FIG. 7 is a diagram showing a configuration diagram of a second embodiment of the present invention.

FIG. 8 is a diagram illustrating a computer simulation result according to the second embodiment of this invention.

[Explanation of symbols]

 1, 2, 20 Antenna 3, 4, 21 Baseband signal generator 5, 24 Arrival angle estimation circuit 25 Vehicle speed measurement circuit

Claims (6)

[Claims] 1. An arrival angle measuring method for measuring a direction of an incoming wave using one antenna, a receiving unit connected to the antenna for receiving one signal, and an arrival angle estimating unit for estimating an arrival direction of the signal. Having a certain angle with respect to the arriving wave, moving the antenna at a certain speed, and converting the serial reception signal received by the antenna and the receiving means for each predetermined time into a parallel signal. Converting the parallel received signal as a received signal received by a plurality of antennas provided at regular intervals, and measuring the direction of the incoming wave by the angle of arrival estimating means. Method. 2. An arrival angle measuring method for measuring a direction of an incoming wave based on an eigen expansion method or a beam forming method, comprising: providing one antenna and one receiving means connected to the antenna; Having a certain angle, moving the antenna at a certain speed, converting the serial reception signal received by the antenna and the receiving means at every predetermined time into a parallel signal, An arrival angle measuring method characterized in that a direction of an incoming wave is measured based on an eigen-expansion method or a beam-forming method, assuming that received signals are received by a plurality of antennas provided at predetermined intervals. 3. The arrival angle measurement method according to claim 1, wherein vTs / λ ≦ 0.5, where Ts is the predetermined time, v is the moving speed of the antenna, and λ is the wavelength of the radio wave. 3. The arrival angle measuring method according to claim 1 or 2, wherein: 4. An angle-of-arrival measuring device provided on a moving object, a receiving means for converting a received signal from one antenna into a baseband band and outputting a received baseband signal, and converting the received baseband signal into a known signal. Reverse modulation means for performing reverse modulation using a sequence and outputting a reverse modulation signal; serial / parallel conversion means for performing serial / parallel conversion using the reverse modulation signal as input and outputting a reverse modulation parallel signal; Vehicle speed measuring means for measuring and outputting a speed; arrival angle estimating means for estimating and outputting an angle of arrival of a radio wave with the inversely modulated parallel signal and the speed of the moving object as inputs. Measuring instrument. 5. An angle-of-arrival measuring device provided on a moving body, comprising: receiving means for converting a received signal from one antenna into a baseband and outputting a received baseband signal; and serially receiving the received baseband signal as an input. Serial / parallel conversion means for performing parallel conversion and outputting a reception baseband / parallel signal; vehicle speed measurement means for measuring and outputting the speed of a moving object; and measuring the reception baseband / parallel signal and the speed of the moving object. An arrival angle measuring device comprising an arrival angle estimating means for estimating and outputting an arrival angle of a radio wave as an input. 6. The angle-of-arrival measuring device according to claim 4, wherein the angle-of-arrival estimation means estimates the angle of arrival based on an eigenexpansion method or a beamforming method.