CN103180751A - Arrival angle calculation device - Google Patents

Abstract

An arrival angle calculation device capable of calculating an arrival angle with high accuracy. An arrival angle calculation device (1) is provided with a plurality of antennas, a plurality of reception signal processing units, and an arrival angle calculation unit, wherein each reception signal processing unit is provided with a reception unit (12A, 12 b), a correlation processing unit (21 a, 21 b), a peak detection unit (22A ), a timing control unit (23 a, 23 b), and a timing control unit (23 a, 23 b) that outputs a signal from the correlation processing unit (21 a, 21 b) to an arrival angle calculation unit (24) if the ratio of the power in the peak period in a period corresponding to an information unit to the power in a period other than the peak period is greater than a threshold value.

Description

Arrival angle calculation device

technical field

The present invention relates to an arrival angle calculating device which detects the phase of an arriving radio wave and uses it for calculating the arrival angle of the radio wave.

Background technique

In the conventional direction-of-arrival estimating apparatus, calculations requiring a large amount of calculations, such as calculations of cross-correlation coefficients and inverse matrix calculations, require calculations of hundreds of symbols. Therefore, it is desired to obtain a direction-of-arrival estimating device that can estimate the direction of arrival through simple calculations.

Patent Document 1 proposes a direction-of-arrival estimating device with a reduced calculation scale. In the direction of arrival estimating device described in Patent Document 1, the coefficient of the direction of arrival is calculated by the complex conjugate circuit and the multiplication circuit for the received signal received by the two antennas, and the arctangent operation is performed in the direction of arrival detection circuit. And arccosine operation, and estimate the direction of arrival of the received wave.

prior art literature

patent documents

Patent Document 1: Japanese Patent Application Laid-Open No. 10-177064

Contents of the invention

The problem to be solved by the invention

However, in Patent Document 1, the power of the direction-of-arrival vector between one slot is compared with a threshold value, and the direction-of-arrival vector is updated when the power of the direction-of-arrival vector between one slot is greater than the threshold value. Expect a wave to update the direction of arrival. For example, when the background value of the received wave is high, the power of the received wave may become larger than the threshold regardless of the signal level of the desired wave. In this case, the direction of arrival is also calculated and updated under the background value, so the direction of arrival cannot be correctly estimated.

The present invention has been made in view of such points, and an object of the present invention is to provide an arrival angle calculation device capable of suppressing the influence of background values of received waves and calculating an arrival angle with high precision.

means to solve the problem

The angle of arrival calculation device of the present invention is characterized in that it includes: a plurality of antennas for receiving radio waves transmitted from a certain position; a plurality of received signal processing units provided corresponding to the antennas; and an angle of arrival calculation unit configured from The output signals outputted by the plurality of received signal processing units take in signal components that are the same information unit among the received signal processing units to calculate the angle of arrival of the radio waves, and each of the received signal processing units includes: a receiving unit configured by a corresponding The electric wave received by the antenna is converted into a received signal having phase information of the electric wave and output; the correlation processing unit performs correlation processing on the received signal output from the receiving unit; the peak detection unit detects that the correlation has been performed. a peak value of the received signal to be processed; and a timing control unit that is detected by the peak detection unit in such a manner that a signal component that becomes the same information unit between the received signal processing units is cut out from the output signal of the correlation processing unit. In accordance with the timing of the peak value, the timing of taking in the output signal output from the correlation processing unit is controlled, and the power during the peak period and the power during the period other than the peak period in the period corresponding to the information unit are controlled. When the ratio is larger than the threshold value, the timing control unit outputs the signal from the correlation processing unit to the angle-of-arrival calculation unit.

According to this configuration, the ratio between the power during the peak period and the power during other periods is compared with the threshold value, and when the ratio is greater than the threshold value, the angle of arrival is calculated. Therefore, even when the signal level of the received wave other than the desired wave is high Under this condition, it is also possible to accurately detect the peak of the desired wave and calculate the angle of arrival. That is, since the angle of arrival is not calculated from parts other than the desired wave, the calculation accuracy of the angle of arrival can be improved.

In the angle of arrival calculation device of the present invention, it is also possible to compare the ratio ΣP ₁ /ΣP _{2 between ΣP 1 and ΣP 2 with a} threshold value, and when the ratio ΣP ₁ /ΣP ₂ is greater than the In the case of a threshold value, the timing control unit outputs the signal from the correlation processing unit to the angle-of-arrival calculation unit, wherein the above-mentioned ΣP ₁ is the sum of the electric power during the peak period in the period corresponding to the information unit , the above-mentioned ΣP ₂ is the sum of electric power in periods other than the peak period in the period corresponding to the information unit.

In the angle-of-arrival calculation device of the present invention, the angle-of-arrival calculation unit may include: a complex conjugate unit that takes the complex conjugate of the signal from the timing control unit of one reception signal processing unit, and the one reception signal processing unit The signal processing part corresponds to one antenna; the complex multiplication part multiplies the output of the complex conjugate part and the signal from the timing control part of the other received signal processing part, and the received signal processing part of the other party is connected to the other antenna. one antenna corresponds; the arctangent part uses the output of the complex multiplication part to perform an arctangent calculation, and calculates the phase difference of the received radio wave between the antennas; the averaging part performs an arctangent calculation on the output of the arctangent part Averaging; and an arrival angle conversion unit that performs an inverse trigonometric calculation using the output of the averaging unit to convert it into an arrival angle. According to this configuration, the angle of arrival can be calculated without using the calculation of the correlation coefficient, the inverse matrix operation, and the like, so that the scale of the angle-of-arrival calculation device can be reduced.

In the angle-of-arrival calculation device of the present invention, the angle-of-arrival calculation unit may use each The phase difference is averaged after being rotated by a predetermined angle, the predetermined angle is subtracted from the average value, and an inverse trigonometric function is performed to convert it into an arrival angle. According to this configuration, when the phase difference is distributed in the phase difference region where the calculation accuracy of the angle of arrival tends to decrease, the calculation of the angle of arrival is performed by rotating the phase difference by only a predetermined angle, so that the calculation accuracy of the angle of arrival does not decrease. . As a result, the calculation accuracy of the angle of arrival can be sufficiently improved.

In the angle of arrival calculation device of the present invention, on the I-Q plane, the number of phase differences greater than +90° or less than -90° may be greater than the number of phase differences less than +90° and greater than -90° In the case of , it is determined that they are distributed in the vicinity of +180° and/or -180° on the I-Q plane.

In the arrival angle calculation device of the present invention, the predetermined angle may be any angle of +90°, -90°, +180°, or -180°.

In the angle of arrival calculation device of the present invention, the I component of the output of the complex multiplication unit may be negative, and the absolute value of the I component of the output of the complex multiplication unit may be compared with the absolute value of the Q component. If it is sufficiently large, the corrected phase difference is calculated by performing an arctangent operation in which the relationship between the I component and the Q component is reversed after the sign of the Q component is reversed, and the corrected phase difference is calculated. After averaging, 90° is subtracted from the average value, and an inverse trigonometric function operation is performed to convert it into an angle of arrival. According to this configuration, when the phase difference distribution is in the phase difference region where the calculation accuracy of the angle of arrival tends to decrease, the calculation of the angle of arrival is performed by rotating the phase difference by a predetermined angle, so that the calculation accuracy of the angle of arrival is not high. reduce. As a result, the calculation accuracy of the angle of arrival can be sufficiently improved.

In the angle of arrival calculation device of the present invention, the I component of the output of the complex multiplication unit may be negative, and the absolute value of the I component of the output of the complex multiplication unit may be compared with the absolute value of the Q component. If it is sufficiently large, the corrected phase difference is calculated by performing an arctangent operation in which the relationship between the I component and the Q component is reversed after the sign of the I component is reversed, and the corrected phase difference is calculated. For averaging, add 90° to the average value and perform an inverse trigonometric function operation to convert it into an arrival angle. According to this configuration, when the phase difference distribution is in the phase difference region where the calculation accuracy of the angle of arrival tends to decrease, the calculation of the angle of arrival is performed by rotating the phase difference by a predetermined angle, so that the calculation accuracy of the angle of arrival is not high. reduce. As a result, the calculation accuracy of the angle of arrival can be sufficiently improved.

In the angle of arrival calculation device of the present invention, the I component of the output of the complex multiplication unit may be negative, and the absolute value of the I component of the output of the complex multiplication unit may be compared with the absolute value of the Q component. If it is sufficiently large, the corrected phase difference is calculated by performing an arctangent operation after inverting the sign of the I component and the Q component, the corrected phase difference is averaged, and from the average After the value is subtracted by 180°, the inverse trigonometric function operation is performed to transform it into the arrival angle. According to this configuration, when the phase difference distribution is in the phase difference region where the calculation accuracy of the angle of arrival tends to decrease, the calculation of the angle of arrival is performed by rotating the phase difference by a predetermined angle, so that the calculation accuracy of the angle of arrival is not high. reduce. As a result, the calculation accuracy of the angle of arrival can be sufficiently improved.

Invention effect

According to the angle-of-arrival calculating device of the present invention, the ratio of the electric power during the peak period to the electric power during the remaining periods other than the peak period is obtained, the obtained ratio is compared with a threshold value, and the angle of arrival is calculated when the ratio is larger than the threshold value. , so even when the signal level of the received wave other than the desired wave is high, the peak of the desired wave can be accurately detected and the angle of arrival can be calculated. That is, since the angle of arrival is not calculated from parts other than the desired wave, the calculation accuracy of the angle of arrival can be improved.

Description of drawings

FIG. 1 is a block diagram showing a configuration example of an arrival angle calculation device according to the embodiment.

FIG. 2 is a block diagram showing a specific configuration (DSSS) of the angle-of-arrival calculation device according to the embodiment.

FIG. 3 is a diagram showing an example of an output waveform of an adder.

FIG. 4( a ) is a diagram showing an example of an output waveform of an arctangent unit, and FIG. 4( b ) is a diagram showing an example of an output waveform of an electric power calculation unit.

Fig. 5 is a schematic diagram showing the geometric relationship of radio waves reaching the antenna.

FIG. 6 is a schematic diagram showing an example of a position detection system including an arrival angle calculation device.

Fig. 7 is a flow chart of the angle of arrival calculation in the angle of arrival calculation device.

FIG. 8 is a schematic diagram of signals input to a peak detection unit.

FIG. 9 is a schematic diagram showing an example of a signal input to a peak detection unit when DSSS is used as a modulation scheme.

FIG. 10 is a schematic diagram showing an example of a signal input to a peak detection unit when a received signal is acquired using an AD converter.

FIG. 11 is a block diagram showing another example of an arrival angle calculation unit.

FIG. 12 is a schematic diagram showing a calculation range of a phase difference.

FIG. 13 is a schematic diagram showing an example of calculated phase difference data.

FIG. 14 is a schematic diagram showing an outline of angle-of-arrival calculation when the phase difference is in the vicinity of +180° or −180°.

FIG. 15 is a flowchart of angle-of-arrival calculation when the phase difference is in the vicinity of +180° or −180°.

FIG. 16 is a block diagram showing another example of an arrival angle calculation unit.

FIG. 17 is a block diagram showing a specific configuration (OFDM) of the angle-of-arrival calculation device according to the embodiment.

FIG. 18( a ) is a schematic diagram showing a symbol configuration in OFDM, and FIG. 18( b ) is a schematic diagram showing a state of correlation processing of OFDM symbol strings.

19 (a) and (b) are diagrams showing examples of output waveforms from the power calculation unit, (c) are diagrams showing examples of output waveforms from the addition unit, and (d) are diagrams showing each part from the arctangent unit A diagram of an example of the output waveform.

FIG. 20 is a schematic diagram showing a configuration example of a capsule endoscope system using an arrival angle calculation device.

Detailed ways

FIG. 1 is a block diagram showing a configuration example of an arrival angle calculation device according to an embodiment of the present invention. The angle-of-arrival calculation device 1 according to this embodiment includes: a reference signal generator 10 capable of oscillating a reference signal at a predetermined oscillation frequency; receiving antennas 11a, 11b arranged at predetermined intervals; The reference signal output by the reference signal generator 10 converts the radio waves received by the receiving antennas 11a, 11b into received signals and outputs them; various operations. Also, since the angle of arrival calculation device 1 calculates the angle of arrival based on the phase lag caused by the propagation delay of radio waves, it is necessary to receive radio waves having the same information at two points (or two or more points) separated by a predetermined interval. Therefore, it is necessary to have two (or more) antennas and receiving systems corresponding to receiving radio waves. In addition, the angle-of-arrival calculation device 1 is not limited to the configuration including two or more receiving systems as long as the same arriving radio wave (same information unit) can be received at two or more positions separated by a predetermined interval.

The receiving units 12a and 12b are configured to include a low-noise amplifier, a mixer, a band-pass filter, and the like, and are configured to be able to receive radio waves of a predetermined frequency. The computing unit 13 is configured to include: a correlation processing unit 21a, 21b, which performs correlation processing on the received signal; a peak detection unit 22a, 22b, which detects the peak value of the received signal that has undergone the correlation processing; The timing of the peak detected by the parts 22a, 22b outputs signals from the correlation processing parts 21a, 21b; and the arrival angle calculation part 24 calculates the arrival angle based on the signals from the timing control parts 23a, 23b. In addition, the configuration and functions of the computing unit 13 may be realized by hardware or by software.

The correlation processing units 21a and 21b multiply the received signal from the receiving unit 12a and 12b by a signal having a high correlation with the received signal, and output the multiplied signal. Since the signals multiplied by the correlation processing units 21a and 21b have a high correlation with the received signal, the signals output from the correlation processing units 21a and 21b peak in the correlation interval. The peak detection units 22a, 22b calculate the power of the output signals from the correlation processing units 21a, 21b, and detect the power peaks of the output signals. The timing control units 23a, 23b output the output signals from the correlation processing units 21a, 21b to the arrival angle calculation unit 24 in accordance with the peak timings detected by the peak detection units 22a, 22b. Specifically, it is determined whether or not to output the output signals from the correlation processing units 21 a and 21 b to the angle-of-arrival calculation unit 24 based on information calculated from the detected electric power in the peak period.

FIG. 2 is a block diagram showing a specific configuration example of an angle-of-arrival calculation device when direct spectrum spread (DSSS) is used as a modulation scheme. In addition, in FIG. 2, only the structure corresponding to the calculation part 13 in FIG. 1 is shown.

In FIG. 2 , the correlation processing unit 21a includes: a spreading code generator 31 that generates a spreading code; multipliers 32a and 32b that multiply the received signal and the spreading code; ) period and output to the adders 33a and 33b of the peak detection unit 22a and the timing control unit 23a. The peak detection unit 22a includes: a power calculation unit 34a that calculates the power of the signals output from the adders 33a and 33b; and a peak power detection unit 35a that detects the power peak value and outputs it to the timing control unit 23a. The timing control unit 23a includes a buffer unit 36a, and controls whether or not signals from the adders 33a and 33b are output to the angle-of-arrival calculation unit 24 based on the signal from the peak power detection unit 35a. Similarly, the correlation processing unit 21b includes a spreading code generator 31, multipliers 32c and 32d, and adders 33c and 33d. The peak detection unit 22b includes a power calculation unit 34b and a peak power detection unit 35b. The timing control unit 23b includes a buffer unit 36b. The angle of arrival calculation unit 24 includes: a complex conjugate unit 41 that takes the complex conjugate of the output of the buffer unit 36a; a complex multiplication unit 42 that multiplies the output of the complex conjugate unit 41 and the output of the buffer unit 36b; The arc tangent unit 43 that performs the arc tangent calculation based on the output of the unit 42; the power calculation unit 44 that calculates the power of each chip (chip) interval based on the output signal of the complex multiplication unit 42; an averaging unit 45 for averaging the output of the arctangent unit 43; and an arrival angle conversion unit 46 for converting the output of the averaging unit 45 into an arrival angle.

The spreading code generator 31 generates a spreading code for despreading a signal spread on the frequency axis by DSSS. This spreading code corresponds to the spreading code used for code modulation (spreading) on the transmission side. The multipliers 32a and 32b despread the reception signal by multiplying it by the spreading code. The in-phase component I1 of the received signal from the receiving unit 12a is input to the multiplier 32a. In addition, the quadrature component Q1 of the received signal from the receiving unit 12a is input to the multiplier 32b. The adders 33 a and 33 b add the outputs of the multipliers 32 a and 32 b for each chip interval within a period corresponding to 1 bit (bit interval) and output the result. FIG. 3( a ) shows an example of an output waveform from the adder 33 a. Fig. 3(b) is a partially enlarged view of the output waveform shown in Fig. 3(a). In addition, FIG.3(c) has shown the example of the output waveform from the adder 33b. Fig. 3(d) is a partially enlarged view of the output waveform shown in Fig. 3(c).

The output signal of the adder 33a and the output signal of the adder 33b are input to the electric power calculation part 34a of the peak detection part 22a and the buffer part 36a of the timing control part 23a. The power calculating unit 34a calculates the power for each chip interval based on the output signals of the adders 33a and 33b. Specifically, the power calculation unit 34a adds the absolute value of the output signal of the adder 33a corresponding to the in-phase component and the absolute value of the output signal of the adder 33b corresponding to the quadrature component, as power information for each chip interval And it outputs to the peak electric power detection part 35a. When receiving power information for each chip interval, the peak power detection unit 35a detects the power peak value in the received signal, and outputs it as power peak information to the buffer unit 36a of the timing control unit 23a. In addition, the square value of the output signal of the adder 33a and the square value of the output signal of the adder 33b may be added and output to the peak electric power detection part 35a.

The power peak information output from the peak detection unit 22 a (peak power detection unit 35 a ) is information for determining the presence or absence of a peak of the received signal. Specifically, the power peak information is the sum ΣP ₁ representing the power in the period near the peak point of the received signal (peak period) and the period excluding the peak period from the 1-bit period serving as the information unit in DSSS. Information on whether the ratio R (=ΣP ₁ /ΣP ₂ ) of the electric power sum ΣP ₂ is greater than the threshold value R _th . In the power peak information, when R is larger than R _th , the timing control unit 23a (buffer unit 36a) considers that the received signal has a peak value at the timing, and sends 1-bit signal Ia1 and signal Qa1 to the arrival angle calculation unit 24 output. On the other hand, when R is smaller than R _th , the timing control unit 23 a (buffer unit 36 a ) considers that the received signal does not have a peak at the timing, and stops the output to the angle-of-arrival calculation unit 24 . In addition, here, although the peak detection unit 22a performed calculation processing related to the power peak information, the timing control unit 23a may perform calculation processing related to the power peak information.

及

表示各信号的相位。Correlation processing unit 21b (diffusion code generator 31, multipliers 32c and 32d, adders 33c and 33d), peak detection unit 22b (power calculation unit 34b, peak power detection unit 35b), timing control unit 23b (buffer unit 36b) The operation and function of the above-mentioned correlation processing unit 21a (diffusion code generator 31, multipliers 32a and 32b, adders 33a and 33b), peak detection unit 22a (power calculation unit 34a, peak power detection unit 35a), timing control The operation and function of the unit 23 a (buffer unit 36 a ) are the same. However, since the received signal input to the correlation processing unit 21b and the received signal input to the correlation processing unit 21a receive the same radio wave at two points separated by a predetermined interval, their phases are slightly different. Therefore, the phase of the signal output from the timing control unit 23b is slightly different from that of the signal output from the timing control unit 23a. When the output O _a1 of the timing control unit 23a and the output O _a2 of the timing control unit 23b are represented by complex numbers with the signal corresponding to the in-phase component as the real part and the signal corresponding to the quadrature component as the imaginary part, the following As in formulas (1) and (2). in addition,

and

Indicates the phase of each signal.

【Formula 1】

${\mathrm{<span\; class="notranslate">\; o</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="Ia"\; filenames="HDA00003110433600011.png,HDA00003110433600122.png"\; state="\{\{state\}\}">Ia</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="iQ"\; filenames="HDA00003110433600011.png,HDA00003110433600122.png"\; state="\{\{state\}\}">iQ</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; Ae</span>}}^{\mathrm{<span\; class="notranslate">\; i</span>}{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; A</span>}\mathrm{<span\; class="notranslate">\; cos</span>}\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; iA</span>}\mathrm{<span\; class="notranslate">\; sin</span>}{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

[Formula 2]

${\mathrm{<span\; class="notranslate">\; o</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="Ia"\; filenames="HDA00003110433600091.png,HDA00003110433600181.png"\; state="\{\{state\}\}">Ia</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="iQ"\; filenames="HDA00003110433600091.png,HDA00003110433600181.png"\; state="\{\{state\}\}">iQ</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; Ae</span>}}^{\mathrm{<span\; class="notranslate">\; i</span>}{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; A</span>}\mathrm{<span\; class="notranslate">\; cos</span>}\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; iA</span>}\mathrm{<span\; class="notranslate">\; sin</span>}{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

The output O _a1 of the timing control unit 23 a is input to the complex conjugate unit 41 of the arrival angle calculation unit 24 . The complex conjugate unit 41 outputs the complex conjugate of the output O _a1 of the timing control unit 23 a to the complex multiplication unit 42 . That is, the signal Ia1 and the sign-inverted signal of the signal Qa1 are output from the complex conjugate unit 41 . When the output O _{a1 ′} of the complex conjugate unit 41 is represented by a complex number, it becomes like the following formula (3).

[Formula 3]

${\mathrm{<span\; class="notranslate">\; o</span>}}_{\mathrm{<span\; class="notranslate">\; a</span>}{\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; \&prime;</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; Ia</span>}\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="iQ"\; filenames="HDA00003110433600011.png,HDA00003110433600122.png"\; state="\{\{state\}\}">iQ</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; Ae</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; i</span>}{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; A</span>}\mathrm{<span\; class="notranslate">\; cos</span>}{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; iA</span>}\mathrm{<span\; class="notranslate">\; sin</span>}{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

The complex multiplication unit 42 complex multiplies the output O _{a1 ′} of the complex conjugate unit 41 and the output O _a2 of the timing control unit 23b, and supplies the signal Ib and the signal Qb as the result of the multiplication to the arctangent unit 43 and the electric power calculation unit 44. output. The output O _b of the complex multiplication unit 42 , the in-phase component Ib and the quadrature component Qb of the output O _b are expressed as in the following expressions (4) to (6).

[Formula 4]

${\mathrm{<span\; class="notranslate">\; o</span>}}_{\mathrm{<span\; class="notranslate">\; b</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; Ae</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; i</span>}{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}<span\; class="notranslate">\; \&Center\; Dot;</span>{\mathrm{<span\; class="notranslate">\; Ae</span>}}^{\mathrm{<span\; class="notranslate">\; i</span>}{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}}<span\; class="notranslate">\; (</span><span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; be</span>}}^{\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; )</span>$

$<span\; class="notranslate">\; =</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="Ia"\; filenames="HDA00003110433600011.png,HDA00003110433600122.png"\; state="\{\{state\}\}">Ia</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; <figure-callout\; id="2"\; label="Ia"\; filenames="HDA00003110433600091.png,HDA00003110433600181.png"\; state="\{\{state\}\}">Ia</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="Q"\; filenames="HDA00003110433600011.png,HDA00003110433600122.png"\; state="\{\{state\}\}">Q</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; Q</span>}\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="Q"\; filenames="HDA00003110433600011.png,HDA00003110433600122.png"\; state="\{\{state\}\}">Q</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; Ia</span>}\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; <figure-callout\; id="1"\; label="Ia"\; filenames="HDA00003110433600011.png,HDA00003110433600122.png"\; state="\{\{state\}\}">Ia</figure-callout></span>}\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; Q</span>}\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

[Formula 5]

Ib=Ia1×Ia2+Qa1×Qa2 ...(5)

[Formula 6]

Qb＝Qa1×Ia2-Ia1×Qa2 ...(6)

相当，由下述式（7）表示。The arctangent unit 43 performs an arctangent calculation using the output of the complex multiplication unit 42 . Specifically, an arctangent calculation of a value with the output signal Ib of the complex multiplication unit 42 as the denominator and the output signal Qb as the numerator is performed. FIG. 4( a ) shows an example of an output waveform from the arctangent unit 43 . The output O _arctan of the arc tangent unit 43 and the phase difference

Correspondingly, represented by the following formula (7).

[Formula 7]

${\mathrm{<span\; class="notranslate">\; o</span>}}_{\mathrm{<span\; class="notranslate">\; arctan</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; the\; tan</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}\frac{\mathrm{<span\; class="notranslate">\; Qb</span>}}{\mathrm{<span\; class="notranslate">\; Ib</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}<span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 7</span>}<span\; class="notranslate">\; )</span>$

The power calculation unit 44 calculates the power for each chip interval based on the output signal of the complex multiplication unit 42 . Specifically, the power calculation unit 44 adds the absolute value of Ib and the absolute value of Qb, and outputs it to the averaging unit 45 as power information for each chip interval. Alternatively, the square value of Ib and the square value of Qb may be added and output to the averaging unit 45 . FIG. 4( b ) shows an example of an output waveform from the power calculation unit 44 . The averaging unit 45 receives the power information for each chip interval, averages the output O _arctan of the arctangent unit 43 based on the information, and outputs it to the angle-of-arrival converting unit 46 . In addition, the electric power calculation part 44 and the averaging part 45 can also be omitted suitably.

The arrival angle conversion unit 46 uses the output of the averaging unit 45 (the output of the arctangent unit 43 when the averaging unit 45 is not provided) and converts it into an arrival angle by inverse trigonometric calculation. As an inverse trigonometric operation, for example, an arcsine operation can be applied. The value obtained by this calculation, that is, the output of the arrival angle conversion unit 46 corresponds to the arrival angle θ (rad). The output O _arcsin of the arrival angle conversion unit 46 is represented by the following equation (8). In addition, in the following formula, λ(m) is the wavelength of the received wave, and d(m) is the distance between the receiving antennas.

[Formula 8]

${\mathrm{<span\; class="notranslate">\; o</span>}}_{\mathrm{<span\; class="notranslate">\; arcsin</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; sin</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}\frac{{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="43"\; label="o"\; filenames="HDA00003110433600021.png"\; state="\{\{state\}\}">o</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 43</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}}<span\; class="notranslate">\; \&CenterDot;</span>\frac{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}{\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 8</span>}<span\; class="notranslate">\; )</span>$

（rad））。当用接收波的波长λ（m）来表示在该模型中产生的传播距离的差分Δ与相位差

的关系时，成为下述式（9）那样。另外，在下述式中，Δ＜λ。The reason for obtaining the angle of arrival by the above processing is that the geometric relationship shown in FIG. 5 is established. The angle formed by the radio waves arriving at the two receiving antennas 11 a , 11 b arranged at a distance d (m) apart based on a predetermined direction is assumed to be θ (rad). The propagation distance of the radio wave reaching the receiving antenna 11b is Δ(m) longer than the propagation distance of the radio wave reaching the receiving antenna 11a, and a phase delay (phase difference

(rad)). When the wavelength λ(m) of the received wave is used to represent the difference Δ and phase difference of the propagation distance generated in this model

In the case of the relationship, it becomes like the following formula (9). In addition, in the following formulae, Δ<λ.

[Formula 9]

$\mathrm{<span\; class="notranslate">\; \&Delta;</span>}<span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; \&lambda;</span>}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 9</span>}<span\; class="notranslate">\; )</span>$

In addition, the following formula (10) holds true from the geometric relationship of the propagation distance difference Δ, the antenna spacing d, and the arrival angle θ in the above model.

[Formula 10]

Δ＝dsinθ ...(10)

That is, the angle of arrival θ is expressed as in the following equation (11). In addition, Expression (11) corresponds to the processing in the arrival angle conversion unit 46 . Thus, it can be seen that the angle of arrival can be calculated by the angle of arrival calculation device of this embodiment.

[Formula 11]

$\mathrm{<span\; class="notranslate">\; \&theta;</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; sin</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}\frac{{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&phi;</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}\mathrm{<span\; class="notranslate">\; \&pi;</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span>\frac{\mathrm{<span\; class="notranslate">\; \&lambda;</span>}}{\mathrm{<span\; class="notranslate">\; d</span>}}<span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 11</span>}<span\; class="notranslate">\; )</span>$

Next, an example of a position detection system using an arrival angle calculation device will be described. The position detection system 101 shown in FIG. 6 is configured to include an angle-of-arrival calculation device 1a, another angle-of-arrival calculation device 1b arranged at a predetermined distance D from the angle-of-arrival calculation device 1a, an access point 2, or a user terminal 3. The access point 2 and the user terminal 3 are configured to include a transmission system and a reception system (not shown), respectively, and are capable of bidirectional information transmission (communication). In addition, the access point 2 and the user terminal 3 are configured to be able to transmit radio waves for calculating the angle of arrival to the angle-of-arrival calculating device 1 a and the angle-of-arriving calculating device 1 b through respective transmission systems. The object of location detection may be either the access point 2 or the user terminal 3 .

The angle-of-arrival calculation device 1a receives radio waves transmitted from the transmission antenna of the access point 2 through the reception antennas 11aa and 11ab, and calculates the angle-of-arrival based on the angle-of-arrival calculation device 1a. Also, the angle-of-arrival calculation device 1b receives radio waves transmitted from the transmission antenna of the access point 2 through the reception antennas 11ba and 11bb, and calculates the angle-of-arrival based on the angle-of-arrival calculation device 1b. If the positional relationship between the angle-of-arrival calculation device 1a and the angle-of-arrival calculation device 1b is known, the position of the access point 2 can be determined based on the angles of arrival based on each.

In addition, in the case of detecting the position of the user terminal 3 , the angle-of-arrival calculation device 1 a and the angle-of-arrival calculation device 1 b calculate the angle of arrival of radio waves transmitted from the user terminal 3 .

FIG. 7 is a flowchart of the angle-of-arrival calculation in the angle-of-arrival calculation device 1 according to the present embodiment. When the angle-of-arrival calculation device 1 receives radio waves to be calculated for the angle-of-arrival, the receiving units 12a and 12b output reception signals to the correlation processing units 21a and 21b. Thereafter, the correlation processing units 21 a and 21 b perform correlation processing and addition processing of the received signals in step 201 .

Thereafter, in step 202, the peak detection units 22a and 22b detect the peak value P _peak of the electric power from the output signals of the correlation processing units 21a and 21b. Thereafter _{, the sum ΣP 1 of electric power in the period near the peak point (peak period) and the sum ΣP 2 of} electric power in the period other than the peak period are calculated from the 1-bit period (period of information unit) are calculated and calculated. The ratio R (=∑P ₁ /∑P ₂ ). FIG. 8( a ) schematically shows signals input to the peak detection units 22 a and 22 b. The peak power P _peak is the power at the peak point P in Fig. 8(a), ΣP ₁ is the sum of power during the peak period _t1 , and _ΣP2 is the period t obtained by removing the peak period _t1 from the 1-bit period The sum of the electricity in ₂ . Here, the peak period _t1 is a period including the ups and downs of the peak. For example, as shown in FIG. 9 , when DSSS is used as the modulation method, it is possible to form a rising and falling interval twice the period tc of the spreading code. Therefore, the period of 2·tc can be defined as the peak period t ₁ . In addition, in FIG. 9 , period t2 is expressed as tb−2·tc using 1-bit period tb.

FIG. 10 shows an example of signals input to the peak detection units 22a and 22b in the case where the received signal is captured using an AD converter. The horizontal axis t in FIG. 10 represents sample encoding, and t takes discrete values. When DSSS is used as the modulation method, for example, if the spreading code is 11 chips and the 1-bit period is 1 μs, the 1-chip period of the spreading code is 0.091 μs. If it is assumed that the AD conversion is 4 times oversampling during 1 chip period, the up-down interval is extended by 1 chip amount, and becomes ips=ip-3, ipe=ip+3. In this case, R is represented by the following formula (12).

【Number 12】

$\mathrm{<span\; class="notranslate">\; R</span>}<span\; class="notranslate">\; =</span>\frac{{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; ip</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 3</span>}}^{\mathrm{<span\; class="notranslate">\; ip</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}{{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}\mathrm{<span\; class="notranslate">\; 1</span>}}^{\mathrm{<span\; class="notranslate">\; i</span>}\mathrm{<span\; class="notranslate">\; 2</span>}}{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; \&Sigma;</span>}}_{\mathrm{<span\; class="notranslate">\; ip</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 3</span>}}^{\mathrm{<span\; class="notranslate">\; ip</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 3</span>}}{\mathrm{<span\; class="notranslate">\; P</span>}}_{\mathrm{<span\; class="notranslate">\; i</span>}}}<span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; \&CenterDot;</span><span\; class="notranslate">\; \&Center\; Dot;</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 12</span>}<span\; class="notranslate">\; )</span>$

In step 203 , the peak detection units 22 a and 22 b compare the calculated ratio R (=ΣP ₁ /ΣP ₂ ) with a predetermined threshold R _th . When R is _larger than Rth, the peak detection units 22a and 22b output signals of the content to the timing control units 23a and 23b. The timing control unit 23a, when receiving a signal that R is greater than _Rth , considers that the received signal has a peak, and outputs a signal necessary for calculating the angle of arrival to the angle-of-arrival calculation unit 24 . Thereafter, in step 204 , the arrival angle calculation unit 24 calculates the arrival angle. On the other hand, when R is equal to or less than R _th , the peak detection units 22a, 22b output signals of the content to the timing control units 23a, 23b, and the timing control unit 23a considers that there is no peak value in the received signal, and stops reporting to the arrival signal. The output of the angle calculation part 24. Thereafter, the angle-of-arrival calculation device 1 executes the flow from step 201 again. R _th is an arbitrary value. For example, R _th may be set to a value to which the presence or absence of a peak can be determined by comparison with R.

In this way, by comparing the index (R) related to the detected peak value with the threshold value (R _th ) to determine the presence or absence of the peak value, it is possible to accurately determine the presence or absence of the peak value.

Here, a method of simply comparing power (electric power) with a threshold value of power to determine the presence or absence of a peak will be considered. Figure 8(b) schematically represents a signal with a high background value (solid line) and a signal with a low background value (dashed line). In FIG. 8( b ), when the background value is low as indicated by the dotted line, the peak value can be detected by comparing the peak value of the power with the threshold value P _th of the power. However, in FIG. 8( b ), when the background value is high enough to exceed P _th as indicated by the solid line, the peak value cannot be detected even if the peak value of the power is compared with P _th . This is because the background value cannot be considered in a simple comparison of the peak value of the power and the threshold value of the power. Therefore, as shown in the present embodiment, by using an index that takes the background value into consideration for detection of a peak, the presence or absence of a peak can be accurately determined.

As described above, the angle of arrival calculation device according to this embodiment determines the peak value by calculating the ratio of the power during the peak period to the power in the remaining periods other than the peak period, and comparing the calculated ratio with a threshold value. With or without, even when the background value of the received wave is high, the peak of the desired wave can be accurately detected and used for the calculation of the angle of arrival. That is, since the angle of arrival is not calculated from signal components other than the desired wave, the calculation accuracy of the angle of arrival can be improved.

FIG. 11 is a block diagram illustrating another form of the arrival angle calculation unit 24 in the arrival angle calculation device 1 . The angle of arrival calculation unit 24 shown in FIG. 11 includes: a complex conjugate unit 51 that takes the complex conjugate of _{the output O a1 of} the timing control unit 23a; O _a2 A complex multiplication unit 52 for complex multiplication; and an arctangent unit 53 for performing an arctangent calculation using the output of the complex multiplication unit 52. The operations and functions of the complex conjugate unit 51 , complex multiplier 52 , and arctangent unit 53 are the same as those of the complex conjugate unit 41 , complex multiplier 42 , and arctangent unit 43 described above. In addition, it is equipped with: a phase difference correction unit 54 that corrects the calculation result based on the calculation result (phase difference) of the arctangent unit 53; an averaging unit 55 that averages the output of the phase difference correction unit 54; When corrected, the phase difference recorrector 56 corrects the calculation result (average value) of the averaging unit 55; and the arrival angle conversion unit 57 converts the output of the phase difference recorrector 56 into an arrival angle. The operation and function of the arrival angle conversion unit 57 are the same as those of the above-mentioned arrival angle conversion unit 46 .

The phase difference correcting unit 54 adds the phase difference to the calculation result of the arctangent unit when the phase difference as the calculation result of the arctangent unit 53 becomes a value near +180° (+π) or −180° (−π). processing on a specified angle (phase difference). As shown on the I-Q plane of FIG. 12 , the angle-of-arrival calculation unit 24 of this embodiment projects the phase difference onto coordinates in a phase difference range of −180° to +180° (−π to +π). Therefore, for example, as shown in FIG. 13( a ), when the phase difference calculated by the arctangent unit 53 does not have a value near +180° and -180°, by averaging them, it is possible to appropriately calculate the arrival phase difference. angle. However, as shown in FIG. 13(b), when the phase difference calculated by the arctangent unit 53 has a value in the vicinity of +180 and -180, a slight error in the calculated phase difference exerts a large influence on the angle calculation. . Here, it is assumed that two values of -178° and +178° are obtained as phase difference data, and one value of +178° is +178° with an error of -4° from the original value of -178°. of. Their difference is actually only 4°. However, in the averaging process, when averaging as -178° and +178°, the average value becomes 0°. Although there is actually a phase difference of about 180°, it is treated as 0° by the averaging process. In this way, when the averaged phase difference greatly deviates from the original phase difference, it becomes difficult to calculate an appropriate angle of arrival.

Therefore, in the angle-of-arrival calculation unit 24 shown in FIG. 11 , when the phase difference calculated by the arctangent unit 53 has a value around +180° and −180°, the phase difference correction unit 54 performs calculations by the arctangent unit 53 Correction processing of a predetermined angle (phase difference) is added to the result, and appropriate averaging is performed. Whether the calculation result of the arctangent unit 53 is a value near +180° or −180° can be determined based on the distribution of a plurality of phase differences obtained as the calculation result of the arctangent unit 53 . For example, when the number of phase differences greater than +90° (+π/2) or less than -90° (-π/2) is greater than the number of phase differences less than +90° and greater than -90°, it can be determined that The calculation result of the arctangent unit 53 is a value in the vicinity of +180° and −180°. The angle (phase difference) added by the phase difference correction unit 54 may be, for example, +90°, but it is not limited to this as long as it is an angle that can perform appropriate averaging processing. Preferably, it may be any one of -90°, +180° or -180°.

The averaging unit 55 averages the outputs of the phase difference correcting unit 54 . The angle-of-arrival calculation unit 24 of the present embodiment performs correction by adding a phase difference when calculating a phase difference that is not suitable for averaging, so that an appropriate averaging process can be performed in the averaging unit 55 . The phase difference recorrecting unit 56 corrects the output of the averaging unit 55 when the phase difference correction is performed by the phase difference correcting unit 54 . Specifically, correction is performed by subtracting the angle (phase difference) added as a correction value by the phase difference correction unit 54 .

FIG. 14 schematically shows the outline of calculation of the angle of arrival when the phase difference is in the vicinity of +180° and −180°. When the phase difference calculated by the arctangent unit 53 is around +180° and −180° in the I-Q plane, the phase difference correcting unit 54 adds a correction value (+90°) to the phase difference to rotate the coordinate axis, and Transform to the axis used for mean calculation. The averaging unit 55 calculates an average value (−92°) based on the data. The phase difference recorrection unit 56 performs correction by subtracting the correction value (+90°) from the output data of the phase difference correction unit 54 , and outputs the corrected data (+178°) to the arcsine unit 57 .

FIG. 15 is a flowchart of processing in the above-mentioned angle-of-arrival calculation unit 24 . The complex conjugate unit 51 of the angle of arrival calculation unit 24 calculates the complex conjugate of the output O _a1 of the timing control unit 23 a in step 301 . In addition, the complex multiplication unit 52 multiplies the output O _a2 of the timing control unit 23 b and the output O _{a1 ′} of the complex conjugate unit 51 in step 302 . Thereafter, the arctangent unit 53 performs an arctangent calculation using the output of the complex multiplying unit 52 in step 303 to calculate the phase difference between the received signals.

In step 304 , the phase difference correction unit 54 determines whether or not the calculated phase difference is a value around +180° and −180° in the I-Q plane. When the calculated phase difference is not a value near +180° and −180°, the process proceeds to step 305 and the arrival angle calculation unit 24 calculates the arrival angle without correcting the phase difference. When the calculated phase difference is a value around +180° or around −180°, the process proceeds to step 306 . This determination can be made based on whether the number of phase differences greater than +90° or less than −90° is greater than the number of phase differences less than +90° and greater than −90° as described above.

In step 306 , the phase difference correction unit 54 performs a process of adding 90° to the phase difference that is the calculation result of the arctangent unit 53 . In step 307 , the averaging unit 55 averages the outputs of the phase difference correcting unit 54 . Thereafter, in step 308 , the phase difference recorrecting unit 56 performs a process of subtracting 90° from the average value that is the calculation result of the averaging unit 55 . Thereafter, in step 309 , the arrival angle conversion unit 57 calculates the arrival angle based on the output of the phase difference recorrection unit 56 . In this way, in the angle-of-arrival calculation unit 24 shown in FIG. 11 , an appropriate average value is calculated through a series of processes of subtracting a predetermined phase difference after adding and averaging a predetermined phase difference. Therefore, the calculation of the angle of arrival Accuracy is not reduced. As a result, the calculation accuracy of the angle of arrival can be sufficiently improved.

In addition, here, the phase difference correction unit 54 performs a process of adding a predetermined angle to the calculation result of the arctangent unit 53 , but it is not limited to this as long as an appropriate averaging process can be realized. For example, an arrival angle calculation unit 24 having a configuration as shown in FIG. 16 may also be used. _{The angle of arrival calculation unit 24 shown in FIG. 16 includes: a complex conjugate unit 61 that takes the complex conjugate of the output O a1 of} the timing control unit 23a; The complex multiplication unit 62 that outputs O _a2 complex numbers. The operations and functions of the complex conjugate unit 61 and the complex multiplier 62 are the same as those of the complex conjugate unit 41 and the complex multiplier 42 described above. In addition, it is equipped with: an IQ comparison unit 63 that compares the absolute value of the in-phase component (I component) of the output of the complex multiplication unit 62 with the absolute value of the quadrature component (Q component); The arc tangent unit 64 that performs arc tangent calculation by selecting and changing the calculation method based on the output of the comparison unit 63 . In addition, it is provided with: an averaging unit 65 that averages the phase difference that is the calculation result of the arctangent unit 64; and a phase difference recorrecting unit that corrects the average value that is the calculation result of the averaging unit 65 based on the calculation method of the arctangent unit 64. 66; and an arrival angle conversion unit 67 for converting the output of the phase difference recorrection unit 66 into an arrival angle. The operation and function of the arrival angle conversion unit 67 are the same as those of the above-mentioned arrival angle conversion unit 46 .

The IQ comparison section 63 determines whether the in-phase component (I component) of the output of the complex multiplication section is negative, and compares the absolute value of the in-phase component (I component) of the output of the complex multiplication section 62 with the absolute value of the quadrature component (Q component). . Specifically, the IQ comparison section 63 judges the sign of the in-phase component Ib, and judges whether the absolute value of the in-phase component |Ib| is sufficiently larger than the absolute value of the quadrature component |Qb| (the absolute value of the quadrature component |Qb| Whether the absolute value of the in-phase component ︱Ib︱ is sufficiently small compared to that). When the phase difference of the received signal takes values around +180° and -180° in the I-Q plane, the in-phase component Ib is negative (Ib<0), the absolute value of the in-phase component︱Ib︱ and the absolute value of the quadrature component ︱Qb︱ is sufficiently larger than ︱Qb︱. Therefore, by judging the sign of the in-phase component Ib and judging whether the absolute value of the in-phase component︱Ib︱ is sufficiently large compared with the absolute value of the quadrature component︱Qb︱, it can be determined whether the phase difference is around +180° and -180° value.

The arc tangent unit 64 uses the output of the complex multiplication unit 62 and selects a calculation method based on the output of the IQ comparison unit 63 to perform an arc tangent calculation. When the in-phase component is positive, the in-phase component is negative, and the absolute value |Ib| of the in-phase component is about the same as or smaller than the absolute value |Qb| of the quadrature component. The arc tangent operation of the value whose output Ib is the denominator and the output Qb is the numerator. In the case where the in-phase component is negative and the absolute value of the in-phase component |Ib| is sufficiently larger than the absolute value of the quadrature component |Qb|, for example, inverting the sign of the output Qb of the complex multiplying unit 62 is performed. - Arctangent operation of the value with Qb as the denominator and output Ib as the numerator. In addition, the above processing when the absolute value of the in-phase component |Ib| is sufficiently larger than the absolute value of the quadrature component |Qb| corresponds to the processing of rotating the coordinate axis by +90° and performing an arctangent calculation. That is, the phase difference obtained by this process is a value obtained by adding +90° to the original phase difference.

In addition, the processing when the absolute value |Ib| of the in-phase component is sufficiently larger than the absolute value |Qb| of the quadrature component is not limited to the above-mentioned processing. For example, an arctangent calculation may be performed using the output Qb of the complex multiplication unit 62 as the denominator and −Ib having the sign of the output Ib inverted as the numerator. This processing corresponds to the processing of rotating the coordinate axis by −90° and performing an arctangent calculation. That is, the phase difference obtained by this process is a value obtained by adding −90° to the original phase difference (a value obtained by subtracting +90°). In addition, for example, the arctangent calculation may be performed by inverting the signs of the output Ib and the output Qb of the complex multiplying unit 62 . This processing corresponds to the processing of performing an arctangent calculation by rotating the coordinate axis by +180° (or -180°). That is, the phase difference obtained by this process is a value obtained by adding +180° (or −180°) to the original phase difference. Through this processing, an appropriate average value can also be calculated.

The averaging unit 65 averages the outputs of the arctangent unit 64 . The angle-of-arrival calculation unit 24 of the present embodiment performs correction that substantially adds (or subtracts) the phase difference when calculating a phase difference that is not suitable for averaging, so that an appropriate averaging process can be performed in the averaging unit 65 . The phase difference recorrecting unit 66 corrects the output of the averaging unit 65 when the arctangent unit 64 has performed the process of rotating the coordinate axis by +90°. Specifically, a correction of subtracting +90° is performed. In addition, when the arctangent unit 64 has performed the process of rotating the coordinate axis by −90°, correction by subtracting −90° (that is, correction by adding +90°) is performed. Similarly, when the arctangent unit 64 performs processing of rotating the coordinate axis by +180° (or −180°), correction of subtracting +180° (or −180°) is performed.

In this way, the arrival angle calculation unit 24 shown in FIG. 16 can also calculate an appropriate average value similarly to the arrival angle calculation unit 24 shown in FIG. 11 , so the calculation accuracy of the arrival angle does not decrease. As a result, the calculation accuracy of the angle of arrival can be sufficiently improved.

FIG. 17 is a block diagram showing a specific configuration example of an angle-of-arrival calculation device when orthogonal frequency division multiplexing (OFDM) is used as a modulation scheme. In addition, in FIG. 17, only the structure corresponding to the calculation part 13 in FIG. 1 is shown.

In FIG. 17 , the correlation processing unit 21a includes: a complex conjugate unit 71a for taking the complex conjugate of the output of the receiving unit 12a; a delay unit 72a for delaying the output of the receiving unit 12a by a predetermined period and outputting it; The output of the part 71a and the output of the delay part 72a are complex multiplied by a complex multiplication part 73a; and the adders 74a, 74b which add the output of the complex multiplication part 73a and output only during the GI (Guard Interval) period. The peak detection unit 22a includes: a power calculation unit 75a that calculates the power of signals output from the adders 74a and 74b; and a peak power detection unit 76a that detects the power peak value and outputs it to the timing control unit 23a. The timing control unit 23a includes a delay unit 77a that controls the output timing of the signal from the reception unit 12a to the angle of arrival calculation unit 24 based on the signal from the peak power detection unit 76a. Similarly, the correlation processing unit 21b includes a complex conjugate unit 71b, a delay unit 72b, a complex multiplication unit 73b, and adders 74c and 74d. The peak detection unit 22b includes a power calculation unit 75b and a peak power detection unit 76b. The timing control unit 23b has a delay Section 77b. Arrival angle calculation unit 24 is equipped with: complex conjugate unit 81 that takes the complex conjugate of the output of delay unit 77a; complex multiplication unit 82 that multiplies the output of complex conjugate unit 81 and the output of delay unit 77b; During the (guard interval) period, adders 83a and 83b add the outputs of the complex multiplying unit 42 and output them; use the outputs of the adders 83a and 83b to perform an arctangent calculation; and average the outputs of the arctangent unit 84 The averaging unit 85; and the arrival angle conversion unit 86 that converts the output of the averaging unit 85 into an arrival angle.

The delay units 72a and 72b take the autocorrelation of the OFDM symbol sequence, and therefore delay the output of the reception unit 12a by a predetermined period and output it. Specifically, the delay units 72a and 72b input the tail of the OFDM symbol output by the complex conjugate unit 71a and the GI (guard interval) output by the delay units 72a and 72b to the complex multiplication unit 73a at the same timing, and make the receiving unit The output of 12a is delayed by a predetermined period and output. The complex multiplication unit 73a complex multiplies the output of the complex conjugate unit 71a and the output of the delay unit 72a. The adders 74a and 74b add the output of the complex multiplying unit 73a for each chip interval and output it only in the GI period.

FIG. 18( a ) is a schematic diagram showing the structure of an OFDM symbol sequence. As shown in FIG. 18( a ), an OFDM symbol sequence is composed of an OFDM symbol as a data part and a GI arranged at the head of the OFDM symbol. The GI copies the data at the end of the OFDM symbol and is inserted to prevent interference between OFDM symbols. FIG. 18( b ) is a schematic diagram showing a state of correlation processing (autocorrelation processing) of OFDM symbol sequences in the correlation processing unit 21 a. As shown in FIG. 18( a ), the output of the delay unit 72 a is delayed by the OFDM symbol length relative to the output of the complex conjugate unit 71 a. Therefore, in the complex multiplying unit 73a, an autocorrelation can be obtained by multiplying the output of the complex conjugate unit 71a and the output of the delay unit 72a. The autocorrelation value (GI correlation value) shows a peak when the same data as GI appears in the output of the complex conjugate part 71a and the output of the delay part 72a, so by using this point, it is possible to detect the OFDM symbol that is the data part start.

The output signals of the adders 74a and 74b are input to the electric power calculation part 75a of the peak detection part 22a. The power calculation unit 75a calculates the power for each chip interval based on the output signals of the adders 74a and 74b. Specifically, the power calculation unit 34a adds the absolute value of the output signal corresponding to the in-phase component and the absolute value of the output signal corresponding to the quadrature component, and outputs it to the peak power detection unit 76a as power information for each chip interval. . Alternatively, the square value of the output signal corresponding to the in-phase component and the square value of the output signal corresponding to the quadrature component may be added and output to the peak power detection unit 76a. FIG. 19( a ) shows an example of an output waveform from the power calculation unit 75 a. Fig. 19(b) is a partially enlarged view of the output waveform shown in Fig. 19(a). When receiving power information for each chip interval, the peak power detection unit 76a detects the power peak value in the received signal, and outputs it as power peak information to the delay unit 77a of the timing control unit 23a.

The power peak information output from the peak detection unit 22 a (peak power detection unit 35 a ) is information for determining the presence or absence of a peak of the received signal. Specifically, the power peak information is the sum ΣP ₁ of the electric power in the period near the peak point of the received signal (peak period) and the period excluding the peak period from the 1-symbol period which is the information unit in OFDM. Information on whether the ratio R (=ΣP ₁ /ΣP ₂ ) of the electric power sum ΣP ₂ is larger than the threshold value R _th . When OFDM is used as the modulation scheme, the peak period is equal to the GI period. In addition, one symbol period corresponds to a period in which the GI period and the data period (OFDM symbol period) are combined. In the power peak information, when R is greater than R _th , the timing control unit 23 a (delay unit 77 a ) considers that the received signal has a peak value at the timing, and sends the received signal from the receiving unit 12 a to the arrival angle calculation unit 24 . On the other hand, when R is smaller than R _th , the timing control unit 23 a (delay unit 77 a ) considers that the received signal does not have a peak at the timing, and stops the output to the angle-of-arrival calculation unit 24 . In addition, here, although the peak detection unit 22a performed calculation processing related to the power peak information, the timing control unit 23a may perform calculation processing related to the power peak information.

Correlation processing unit 21b (complex conjugate unit 71b, delay unit 72b, complex multiplication unit 73b, adders 74c, 74d), peak detection unit 22b (power calculation unit 75b, peak power detection unit 76b), timing control unit 23b (delay Part 77b), the action and function of the correlation processing part 21a (complex conjugate part 71a, delay part 72a, complex multiplication part 73a, adder 74a, 74b), peak detection part 22a (power calculation part 75a, peak power detection part 76a), the operation and function of the timing control unit 23a (delay unit 77a) are the same. However, the received signal input to the correlation processing unit 21b and the received signal input to the correlation processing unit 21a are slightly different in phase since the same radio wave is received at two points separated by a predetermined interval. Therefore, the phase is slightly different between the signal output from the timing control unit 23b and the signal output from the timing control unit 23a.

The output of the timing control unit 23 a is input to the complex conjugate unit 81 of the arrival angle calculation unit 24 . The complex conjugate unit 81 outputs the complex conjugate of the output of the timing control unit 23 a to the complex multiplication unit 82 . The complex multiplication unit 82 complex multiplies the output of the complex conjugate unit 81 and the output of the timing control unit 23b, and outputs the calculation result to the addition units 83a and 83b. The adders 83 a and 83 b add the outputs of the complex multiplier 82 for each chip interval in the GI period, and output to the arctangent unit 84 . FIG. 19( c ) shows an example of output waveforms from the adders 83 a and 83 b. In the figure, the output waveform of the adder 83a is represented by I, and the output waveform of the adder 83b is represented by Q.

The arctangent unit 84 performs an arctangent calculation using the outputs of the adders 83a and 83b, and calculates the phase difference of the received signal. FIG. 19( d ) shows an example of an output waveform from the arctangent unit 84 . The averaging unit 85 averages the output of the arctangent unit 84 and outputs it to the arrival angle conversion unit 86 . In addition, the averaging unit 85 may be appropriately omitted. The arrival angle conversion unit 86 uses the output of the averaging unit 85 (the output of the arctangent unit 84 when the averaging unit 85 is not provided) and converts it into an arrival angle by inverse trigonometric calculation. The value obtained by this calculation, that is, the output of the arrival angle conversion unit 86 corresponds to the arrival angle.

In this way, also in the angle-of-arrival calculation device 1 having the calculation unit 13 of FIG. By judging the presence or absence of peaks, even when the background value of the received wave is high, the peak of the desired wave can be accurately detected and used to calculate the angle of arrival. That is, since the angle of arrival is not calculated from signal components other than the desired wave, the calculation accuracy of the angle of arrival can be improved.

FIG. 20 is a schematic diagram showing a position-specific capsule endoscope system in which the angle-of-arrival calculation device 1 is applied to the capsule endoscope. The capsule endoscope system shown in FIG. 20 includes a plurality of sensor arrays 401 and a data logger 402 that records data from the sensor arrays 401 . The sensor array 401 includes an antenna corresponding to the receiving antenna of the angle-of-arrival calculation device 1 , and is configured to receive radio waves from a capsule endoscope swallowed by a patient. The data recorder 402 determines the position of the capsule endoscope swallowed by the patient according to the phase information of the electric wave received in the sensor array 401 .

The endoscope capsule, swallowed by the patient, is moved by the peristaltic motion of the digestive tract. The position of the capsule endoscope is monitored, and it can be confirmed whether it has reached the examination site. When the capsule endoscope arrives at the examination site, the capsule endoscope takes pictures of the examination site and sends them to the data recorder 402, and the data recorder 402 records the image information. In this way, by monitoring the position of the capsule endoscope, imaging can be performed without missing the examination site. In addition, since the power of the camera and the like can be turned on at the timing when the capsule endoscope reaches the examination site, and can be turned off when the capsule endoscope departs from the examination site, the battery capacity can be reduced. In addition, the number of sensors (antennas) can be reduced. In addition, if the battery capacity is the same, a large number of images can be transmitted compared with conventional capsule endoscopes, and clearer images can be obtained.

In this way, by applying the angle-of-arrival calculation device 1 to determine the position of a capsule endoscope, an excellent capsule endoscope system can be constructed.

As described above, according to the angle-of-arrival calculation device of the present invention, the ratio of the electric power during the peak period to the electric power during the remaining periods other than the peak period is obtained, and the obtained ratio is compared with the threshold value. If the ratio is greater than the threshold value, The angle of arrival is calculated, so even when the signal level of the received wave other than the desired wave is high, the peak of the desired wave can be accurately detected and the angle of arrival can be calculated. That is, since the angle of arrival is not calculated from parts other than the desired wave, the calculation accuracy of the angle of arrival can be improved.

In addition, this invention is not limited to description of said embodiment, It can change suitably so that the effect may be exhibited. For example, in the above-mentioned embodiment, the ratio of the sum of the electric power during the peak period to the sum of the electric power during periods other than the peak period is compared with the threshold, but as long as the arrival of the level of the signal other than the desired wave can be considered Angle calculation is not limited to this. For example, power at a certain timing during the peak period and power at a certain timing during periods other than the peak period may be used as parameters.

In addition, in the said embodiment, the structure etc. which are shown in drawing are not limited to this, It can change suitably within the range which exhibits the effect of this invention.

Industrial availability

The angle-of-arrival calculation device of the present invention can be used in a system for specifying the position of an object, and in various other applications.

This application is based on Japanese Patent Application No. 2010-254011 filed on November 12, 2010 and incorporates the entire content thereof.

Claims (9)

1. A device for calculating an angle of arrival, characterized in that, It is provided with: a plurality of antennas for receiving radio waves transmitted from a certain position; a plurality of received signal processing units provided corresponding to the antennas; The signal takes in the signal components that become the same information unit between the received signal processing units to calculate the angle of arrival of the radio wave, Each of the received signal processing units includes: a receiving unit that converts the radio wave received by the corresponding antenna into a received signal having phase information of the radio wave and outputs it; and a correlation processing unit that converts the received signal output from the receiving unit Correlation processing is performed; a peak detection unit detects the peak value of the received signal subjected to the correlation processing; and a timing control unit cuts out the output signal from the correlation processing unit to become the same information unit between the received signal processing units. The manner of the signal component is matched with the timing of the peak value detected by the peak detection part, thereby controlling the acquisition timing of the output signal output from the correlation processing part, When the ratio of the power in the peak period to the power in periods other than the peak period in the period corresponding to the information unit is greater than a threshold value, the timing control unit sends a signal from the correlation processing unit to the The output of the angle of arrival calculation unit. 2. The angle of arrival computing device according to claim 1, wherein: The ratio ΣP ₁ /ΣP ₂ of ΣP ₁ and ΣP ₂ is compared with a threshold value, and if the ratio ΣP ₁ /ΣP ₂ is greater than the threshold value, the timing control section will The signal from the correlation processing unit is output to the angle-of-arrival calculation unit, wherein the above-mentioned ΣP ₁ is the sum of electric power during the peak period in the period corresponding to the information unit, and the above-mentioned ΣP ₂ is the period corresponding to the information unit The sum of the power in periods other than the peak period in . 3. The angle of arrival computing device according to claim 1 or 2, wherein: The angle of arrival calculation unit has: The complex conjugate part is used to obtain the complex conjugate of the signal from the timing control part of one received signal processing part, and the one received signal processing part corresponds to one antenna; a complex multiplication unit that multiplies the output of the complex conjugate unit by a signal from the timing control unit of the other received signal processing unit that corresponds to the other antenna; an arctangent unit performing an arctangent calculation using an output of the complex multiplying unit to calculate a phase difference of the received radio waves between the antennas; an averaging unit that averages the output of the arctangent unit; and The arrival angle conversion unit performs an inverse trigonometric calculation using the output of the averaging unit to convert the arrival angle. 4. The angle of arrival calculation device according to claim 3, wherein: When the calculated phase differences are distributed in the vicinity of +180° and/or -180° on the I-Q plane, the angle-of-arrival calculation unit rotates each phase difference by a predetermined angle and averages them, and obtains the average After subtracting the predetermined angle, an inverse trigonometric function operation is performed to convert it into an arrival angle. 5. The angle of arrival computing device according to claim 4, wherein: On the I-Q plane, when the number of phase differences greater than +90° or less than -90° is greater than the number of phase differences less than +90° and greater than -90°, it is determined that the number of phase differences distributed on the I-Q plane Around +180° and/or -180°. 6. The angle-of-arrival calculating device according to claim 4 or 5, characterized in that, The predetermined angle is any angle of +90°, -90°, +180° or -180°. 7. The angle-of-arrival computing device according to claim 3, wherein: When the I component of the output of the complex multiplication unit is negative and the absolute value of the I component of the output of the complex multiplication unit is sufficiently larger than the absolute value of the Q component, by inverting the Q After the sign of the component is reversed, an arctangent operation is performed in which the relationship between the I component and the Q component is exchanged to calculate the corrected phase difference, the corrected phase difference is averaged, and the inverse Trigonometric function operation, thus transforming into angle of arrival. 8. The angle of arrival computing device according to claim 3, wherein: When the I component of the output of the complex multiplication unit is negative and the absolute value of the I component of the output of the complex multiplication unit is sufficiently larger than the absolute value of the Q component, by inverting the I After the signs of the components are exchanged, the arctangent operation of the relationship between the I component and the Q component is performed to calculate the corrected phase difference, and the corrected phase difference is averaged, and the average value is added to 90° and then reversed. Trigonometric function operation, thus transforming into angle of arrival. 9. The angle-of-arrival computing device according to claim 3, wherein: When the I component of the output of the complex multiplication unit is negative and the absolute value of the I component of the output of the complex multiplication unit is sufficiently larger than the absolute value of the Q component, by inverting the I The sign of the Q component and the sign of the Q component are followed by an arctangent operation to calculate the corrected phase difference, the corrected phase difference is averaged, and an inverse trigonometric function operation is performed after subtracting 180° from the average value, thereby transforming is the angle of arrival.

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