WO2012063532A1 - Arrival angle calculation device - Google Patents

Abstract

The purpose of the present invention is to provide an arrival angle calculation device that can calculate an arrival angle to a high degree of accuracy. This arrival angle calculation device (1) comprises a plurality of antennae, a plurality of received signal processing units, and an arrival angle calculation unit. Each of the received signal processing units comprise reception units (12a, 12b), correlation processing units (21a, 21b), peak detection units (22a, 22b), and timing control units (23a, 23b). The timing control units (23a, 23b) are characterised in that when the ratio between the power of the peak period in a period corresponding to an information unit and the power of a period excluding the peak period is larger than a threshold value, signals from the correlation processing units (21a, 21b) are output to an arrival angle calculation unit (24).

Description

Arrival angle calculation device

The present invention relates to an arrival angle calculation device that detects the phase of an incoming radio wave and uses it to calculate the radio wave arrival angle.

In the conventional direction-of-arrival estimation apparatus, calculations with a large calculation amount such as calculation of cross-correlation coefficients and inverse matrix calculation are used, and calculations for several hundred symbols are required. For this reason, an arrival direction estimation device capable of estimating the arrival direction by simple calculation has been desired.

Patent Document 1 proposes an arrival direction estimation device with a reduced operation scale. In the arrival direction estimation device described in Patent Document 1, the arrival direction coefficient is calculated by the complex conjugate circuit and the multiplication circuit for the reception signals received by the two antennas, and the arc tangent calculation and the inverse cosine are performed in the arrival direction detection circuit. By calculating, the arrival direction of the received wave is estimated.

Japanese Patent Laid-Open No. 10-177064

However, Patent Document 1 adopts a configuration in which the power of the arrival direction vector between one slot is compared with a threshold value and the arrival direction is updated when the threshold value is larger than the threshold value. It may not be possible to accurately detect waves and update the direction of arrival. For example, when the background level of the received wave is high, the power of the received wave may be greater than the threshold value regardless of the signal level of the desired wave. In such a situation, since the arrival direction is calculated and updated even in the background level, the arrival direction cannot be estimated correctly.

The present invention has been made in view of such a point, and an object thereof is to provide an arrival angle calculation apparatus that can suppress the influence of the background level of a received wave and can calculate the arrival angle with high accuracy.

An arrival angle calculation apparatus according to the present invention includes a plurality of antennas that receive radio waves transmitted from a certain position, a plurality of reception signal processing units provided corresponding to the antennas, and a plurality of reception signal processing units. An arrival angle calculation unit that calculates an arrival angle of the radio wave by taking in a signal component that is the same information unit between the reception signal processing units from the output signal that is output, and each reception signal processing unit corresponds to the A reception unit that converts a radio wave received by an antenna into a reception signal having phase information of the radio wave and outputs the signal, a correlation processing unit that performs correlation processing on the reception signal output from the reception unit, and the correlation-processed reception signal Detected by the peak detection unit so that a signal component that is the same unit of information is extracted from the output signal of the correlation processing unit and the received signal processing unit from the output signal of the correlation processing unit. A timing control unit that controls the timing of capturing the output signal output from the correlation processing unit in accordance with the peak timing, and the timing control unit includes power in a peak period in a period corresponding to the information unit. If the ratio of the power to the power in the period excluding the peak period is greater than a threshold value, the signal from the correlation processing unit is output to the arrival angle calculation unit.

According to this configuration, the ratio of the power in the peak period and the power in the other periods is compared with a threshold value, and when the ratio is larger than the threshold value, the arrival angle is calculated. Even if the signal level is high, it is possible to accurately detect the peak of the desired wave and calculate the arrival angle. That is, since the arrival angle is not calculated from a portion other than the desired wave, the calculation accuracy of the arrival angle can be improved.

In the arrival angle calculating apparatus of the present invention, the timing control unit, a period in the power of excluding the peak period in the period corresponding to the information unit to the sum .SIGMA.P ₁ power peak periods in the period corresponding to the information unit The ratio ΣP ₁ / ΣP ₂ with respect to the sum ΣP ₂ is compared with a threshold value. When the ratio ΣP ₁ / ΣP ₂ is larger than the threshold value, the signal from the correlation processing unit is sent to the arrival angle calculation unit. It may be output.

In the arrival angle calculation device according to the present invention, the arrival angle calculation unit includes a complex conjugate unit that takes a complex conjugate of a signal from a timing control unit of one received signal processing unit corresponding to one antenna, and the complex conjugate unit. A complex multiplier that multiplies the output and the signal from the timing control unit of the other received signal processing unit corresponding to the other antenna, and performs an arctangent calculation using the output of the complex multiplier, and An arctangent that calculates the phase difference of the received radio wave, an averaging unit that averages the output of the arctangent, and an inverse trigonometric function calculation using the output of the averaging unit to convert to an arrival angle And an arrival angle conversion unit. According to this configuration, since the arrival angle can be calculated without using cross-correlation coefficient calculation or inverse matrix calculation, the size of the arrival angle calculation device can be reduced.

In the arrival angle calculation device of the present invention, the arrival angle calculation unit calculates each phase difference when the calculated phase difference is distributed around + 180 ° and / or −180 ° on the IQ plane. The arrival angle may be calculated by averaging after rotating by a predetermined angle, subtracting the predetermined angle from the average value, and performing an inverse trigonometric function calculation. According to this configuration, when the phase difference is distributed in the phase difference region where the calculation accuracy of the arrival angle tends to decrease, the arrival angle calculation is performed by rotating the phase difference by a predetermined angle. The calculation accuracy does not decrease. As a result, the calculation accuracy of the arrival angle can be sufficiently increased.

In the arrival angle calculation apparatus of the present invention, the number of phase differences larger than + 90 ° or smaller than −90 ° on the IQ plane is larger than the number of phase differences smaller than + 90 ° and larger than −90 °. In this case, it may be determined that the distribution is in the vicinity of + 180 ° and / or −180 ° on the IQ plane.

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

In the arrival angle calculation apparatus of the present invention, when the I component of the output of the complex multiplier is negative and the absolute value of the I component of the output of the complex multiplier is sufficiently larger than the absolute value of the Q component, A phase difference corrected by performing an arctangent calculation in which the relationship between the I component and the Q component is reversed after inverting the sign of the Q component, averaging the corrected phase difference, and calculating the average value Alternatively, 90 ° may be subtracted from the above and inverse trigonometric function calculation may be performed to convert the angle of arrival. According to this configuration, when the phase difference is distributed in the phase difference region where the calculation accuracy of the arrival angle tends to decrease, the arrival angle calculation is performed by rotating the phase difference by a predetermined angle. The calculation accuracy does not decrease. As a result, the calculation accuracy of the arrival angle can be sufficiently increased.

In the arrival angle calculation apparatus of the present invention, when the I component of the output of the complex multiplier is negative and the absolute value of the I component of the output of the complex multiplier is sufficiently larger than the absolute value of the Q component, A phase difference corrected by performing an arc tangent calculation in which the relationship between the I component and the Q component is exchanged after inverting the sign of the I component, averaging the corrected phase difference, and calculating the average value 90 ° may be added to perform inverse trigonometric function calculation to convert the angle to the arrival angle. According to this configuration, when the phase difference is distributed in the phase difference region where the calculation accuracy of the arrival angle tends to decrease, the arrival angle calculation is performed by rotating the phase difference by a predetermined angle. The calculation accuracy does not decrease. As a result, the calculation accuracy of the arrival angle can be sufficiently increased.

In the arrival angle calculation apparatus of the present invention, when the I component of the output of the complex multiplier is negative and the absolute value of the I component of the output of the complex multiplier is sufficiently larger than the absolute value of the Q component, Calculate the phase difference corrected by performing the arctangent calculation after inverting the sign of the I component and the sign of the Q component, averaging the corrected phase difference, and subtracting 180 ° from the average value An inverse trigonometric function calculation may be performed to convert to an arrival angle. According to this configuration, when the phase difference is distributed in the phase difference region where the calculation accuracy of the arrival angle tends to decrease, the arrival angle calculation is performed by rotating the phase difference by a predetermined angle. The calculation accuracy does not decrease. As a result, the calculation accuracy of the arrival angle can be sufficiently increased.

According to the arrival angle calculation device of the present invention, the ratio between the power in the peak period and the power in the remaining period other than the peak period is obtained, and the obtained ratio is compared with the threshold value. Since the arrival angle is calculated when it is large, the peak of the desired wave can be accurately detected and the arrival angle can be calculated even when the signal level of the received wave other than the desired wave is high. That is, since the arrival angle is not calculated from a portion other than the desired wave, the calculation accuracy of the arrival angle can be improved.

It is a block diagram which shows the structural example of the arrival angle calculation apparatus which concerns on embodiment. It is a block diagram which shows the specific structure (DSSS) of the arrival angle calculation apparatus which concerns on embodiment. It is a figure which shows the example of the output waveform of an adder. (A) It is a figure which shows the example of the output waveform of an arctangent part. (B) It is a figure which shows the example of the output waveform of an electric power calculation part. It is a schematic diagram which shows the geometrical relationship of the electromagnetic wave which arrives at an antenna. It is a schematic diagram which shows the example of the position detection system containing an arrival angle calculation apparatus. It is a flowchart of the arrival angle calculation in an arrival angle calculation apparatus. It is a schematic diagram of the signal input into a peak detection part. It is a schematic diagram which shows the example of the signal input into a peak detection part, when using DSSS as a modulation system. It is a schematic diagram which shows the example of the signal input into the peak detection part at the time of taking in a received signal using an AD converter. It is a block diagram which shows another example of an arrival angle calculation part. It is a schematic diagram shown about the calculation range of a phase difference. It is a schematic diagram which shows the example of the calculated phase difference data. FIG. 6 is a schematic diagram showing an outline of arrival angle calculation when the phase difference is near + 180 ° or −180 °. FIG. 10 is a flowchart for calculating an arrival angle when the phase difference is near + 180 ° or −180 °. It is a block diagram which shows another example of an arrival angle calculation part. It is a block diagram which shows the specific structure (OFDM) of the arrival angle calculation apparatus which concerns on embodiment. (A) It is a schematic diagram which shows the structure of the symbol in OFDM. (B) It is a schematic diagram which shows the mode of the correlation process of an OFDM symbol sequence. (A) (b) It is a figure which shows the example of the output waveform from an electric power calculation part. (C) It is a figure which shows the example of the output waveform from an addition part. (D) It is a figure which shows the example of the output waveform from each part of an arctangent part. It is a schematic diagram which shows the structural example of the capsule endoscope system using an arrival angle calculation apparatus.

FIG. 1 is a block diagram showing a configuration example of an arrival angle calculation apparatus according to an embodiment of the present invention. The arrival angle calculation device 1 according to the present embodiment includes a reference signal generator 10 capable of oscillating a reference signal at a predetermined oscillation frequency, reception antennas 11a and 11b arranged at predetermined intervals, and a reception antenna 11a. , 11b converts the radio wave received by the reference signal output from the reference signal generator 10 into a received signal and outputs the received signal, and the angle of arrival from the received signal output from the receiver 12a, 12b. And an arithmetic unit 13 that performs various arithmetic processes for calculation. In addition, since the arrival angle calculation device 1 calculates the arrival angle based on the phase delay caused by the propagation delay of the radio wave, the radio wave having the same information is received at two points (or two or more points) separated by a predetermined interval. There is a need. For this reason, it is necessary to provide two (or more) antennas and a receiving system corresponding to the received radio wave. Note that the arrival angle calculation device 1 is not limited to a configuration including two or more reception systems as long as the same arrival radio wave (the same information unit) can be received at two or more positions separated by a predetermined interval.

The receiving units 12a and 12b include a low noise amplifier, a mixer, a band pass filter, and the like, and are configured to receive radio waves having a predetermined frequency. The calculation unit 13 includes correlation processing units 21a and 21b that perform correlation processing of received signals, peak detection units 22a and 22b that detect peaks of the correlation processed reception signals, and peaks detected by the peak detection units 22a and 22b. And timing control units 23a and 23b that output signals from the correlation processing units 21a and 21b in accordance with the timing of the received signal, and an arrival angle calculation unit 24 that calculates an arrival angle based on the signals from the timing control units 23a and 23b, and , Including. The configuration and function of the calculation unit 13 may be realized by hardware or software.

The correlation processing units 21a and 21b multiply the reception signals from the reception units 12a and 12b and signals having high correlation with the reception signals and output the result. 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 have a peak in the correlation section. The peak detection units 22a and 22b calculate the power of the output signals from the correlation processing units 21a and 21b, and detect the power peaks of the output signals. The timing control units 23 a and 23 b output the output signals from the correlation processing units 21 a and 21 b to the arrival angle calculation unit 24 in accordance with the peak timing detected by the peak detection units 22 a and 22 b. Specifically, based on the information calculated from the detected power during the peak period, it is determined whether or not to output the output signals from the correlation processing units 21a and 21b to the arrival angle calculating unit 24.

FIG. 2 is a block diagram showing a specific configuration example of the arrival angle calculation apparatus when direct spread spectrum (DSSS) is used as a modulation method. 2 shows only the configuration corresponding to the calculation unit 13 in FIG.

In FIG. 2, a correlation processing unit 21a outputs a spread code generator 31 that generates a spread code, multipliers 32a and 32b that multiply a received signal and a spread code, and outputs of the multipliers 32a and 32b for one bit period. And adders 33a and 33b that are added together and output to the peak detector 22a and the timing controller 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 and outputs the detected power peak to the timing control unit 23a. The timing control unit 23a includes a buffer unit 36a that controls whether the signals from the adders 33a and 33b can be output to the arrival angle calculation unit 24 based on the signal from the peak power detection unit 35a. Similarly, the correlation processing unit 21b includes a spread 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, and performs timing control. The unit 23b includes a buffer unit 36b. The arrival angle calculation unit 24 includes a complex conjugate unit 41 that takes a 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, and a complex multiplication unit 42. Based on the information from the power calculation unit 44, the power calculation unit 44 that calculates the power of each chip section from the output signal of the complex multiplication unit 42 An averaging unit 45 that averages the output of the unit 43, and an arrival angle conversion unit 46 that converts the output of the averaging unit 45 into an arrival angle using the output of the averaging unit 45.

The spreading code generator 31 generates a spreading code for despreading a signal spread on the frequency axis by DSSS. The spreading code corresponds to the spreading code used for code modulation (spreading) on the transmission side. Multipliers 32a and 32b perform despreading by multiplying the received signal by the spreading code. The in-phase component I1 of the received signal from the receiving unit 12a is input to the multiplier 32a. Further, the quadrature component Q1 in the received signal from the receiving unit 12a is input to the multiplier 32b. The adders 33a and 33b output the outputs of the multipliers 32a and 32b for each chip interval by adding a period (bit interval) corresponding to 1 bit. FIG. 3A shows an example of an output waveform from the adder 33a. FIG. 3B is a partially enlarged view of the output waveform shown in FIG. FIG. 3C shows an example of an output waveform from the adder 33b. FIG. 3D is a partially enlarged view of the output waveform shown in FIG.

The output signal of the adder 33a and the output signal of the adder 33b are input to the power calculation unit 34a of the peak detection unit 22a and the buffer unit 36a of the timing control unit 23a. The power calculation unit 34a calculates the power for each chip section from 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, and adds the absolute value for each chip section. It outputs to the peak power detection part 35a as electric power information. Upon receiving the power information for each chip section, the peak power detection unit 35a detects the power peak in the received signal and outputs it as power peak information to the buffer unit 36a of the timing control unit 23a. Note that 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 power detection unit 35a.

The power peak information output from the peak detector 22a (peak power detector 35a) is information for determining whether or not there is a peak in the received signal. Specifically, the power peak information includes the sum of power ΣP ₁ in a period near the peak point of the received signal (peak period) and the power in a period excluding the peak period from a 1-bit period that is an information unit in DSSS. This is information indicating whether the ratio R (= ΣP ₁ / ΣP ₂ ) with the sum ΣP ₂ is greater than the threshold value R _th . In the peak power information, if R is greater than _{R th,} the timing controller 23a (buffer section 36a) as to have a peak received signal at that timing, arrival angle a 1 bit signal Ia1 and signals Qa1 It outputs to the calculation part 24. On the other hand, when R is smaller than _Rth , the timing control unit 23a (buffer unit 36a) stops the output to the arrival angle calculation unit 24, assuming that the received signal has no peak at that timing. Here, the peak detection unit 22a performs the calculation process related to the power peak information, but the calculation process related to the power peak information may be performed in the timing control unit 23a.

Correlation processing unit 21b (spreading 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 operations and functions are as follows: correlation processing unit 21a (spreading 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 23a (buffer unit 36a) 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 because the same radio wave is received at two points separated by a predetermined interval. For this reason, the signal output from the timing control unit 23b and the signal output from the timing control unit 23a are slightly different in phase. Output O _a1 of the timing controller _23a, and the output O _a2 of the timing controller 23b, the real part of the signal corresponding to the phase component, when a signal corresponding to the quadrature component expressed by a complex number as an imaginary part, the following formula (1) (2) Φ ₁ and φ ₂ represent the phase of each signal.

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 complex conjugate section 41 outputs a signal Ia1 and a signal in which the sign of the signal Qa1 is inverted. When the output O _a1 ′ of the complex conjugate unit 41 is expressed by a complex number, the following equation (3) is obtained.

Complex multiplier 42, the output _{O a1'} complex conjugate unit 41, and an output _{O a2} of the timing controller 23b by complex multiplication, inverse tangent portion 43 signals Ib and signal Qb is multiplication result and power calculator 44. 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 by the following equations (4) to (6).

The arctangent unit 43 performs an arctangent calculation using the output of the complex multiplier 42. Specifically, the arc tangent operation is performed on the value using the output signal Ib of the complex multiplier 42 as the denominator and the output signal Qb as the numerator. FIG. 4A shows an example of an output waveform from the arc tangent portion 43. The output O _arctan of the arc tangent 43 corresponds to the phase difference φ ₂ −φ ₁ and is expressed by the following equation (7).

The power calculation unit 44 calculates the power for each chip section from 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 the sum to the averaging unit 45 as power information for each chip section. Note that the square value of Ib and the square value of Qb may be added together and output to the averaging unit 45. FIG. 4B shows an example of an output waveform from the power calculation unit 44. When the averaging unit 45 receives the power information for each chip section, the averaging unit 45 averages the output O _arctan of the arc tangent unit 43 based on the information and outputs the average to the arrival angle conversion unit 46. The power calculation unit 44 and the averaging unit 45 may be omitted as appropriate.

The arrival angle conversion unit 46 converts the arrival angle by the inverse trigonometric function calculation using the output of the averaging unit 45 (or the output of the arctangent unit 43 when the averaging unit 45 is not provided). As the inverse trigonometric function calculation, for example, an inverse sine calculation can be applied. The value obtained by the 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 expressed by the following equation (8). In the following equation, λ (m) is the wavelength of the received wave, and d (m) is the distance between the receiving antennas.

The reason why the arrival angle is obtained by the above process is that a geometrical relationship as shown in FIG. 5 is established. An angle formed by radio waves arriving at two receiving antennas 11a and 11b arranged at a distance d (m) apart from a predetermined direction is defined as θ (rad). The propagation distance of the radio wave arriving at the reception antenna 11b is longer than the propagation distance of the radio wave arriving at the reception antenna 11a by Δ (m), and the phase delay (phase difference φ ₂ −φ ₁ (rad)) is increased. Arise. When the relationship between the propagation distance difference Δ and the phase difference φ ₂ −φ ₁ generated in this model is expressed using the wavelength λ (m) of the received wave, the following equation (9) is obtained. In the following formula, Δ <λ.

Further, the following equation (10) is established from the geometric relationship between the propagation distance difference Δ, the antenna interval d, and the arrival angle θ in the above model.

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

Next, an example of a position detection system using the arrival angle calculation device will be described. The position detection system 101 shown in FIG. 6 includes an arrival angle calculation device 1a, another arrival angle calculation device 1b arranged at a predetermined distance D from the arrival angle calculation device 1a, and the access point 2 or the user terminal 3. Consists of including. Each of the access point 2 and the user terminal 3 includes a transmission system and a reception system (not shown), and is configured to be capable of bidirectional information transmission (communication). In addition, the access point 2 and the user terminal 3 are configured to be able to transmit arrival angle calculation radio waves to the arrival angle calculation device 1a and the arrival angle calculation device 1b by their transmission systems. The position detection target may be either the access point 2 or the user terminal 3.

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

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

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

Thereafter, in step 202, the peak detectors 22a and 22b detect the power peak value P _peak from the output signals of the correlation processors 21a and 21b. Then, the power sum ΣP ₁ in the period near the peak point (peak period) and the power sum ΣP ₂ in the period excluding the peak period from the 1-bit period (information unit period) are calculated, and the ratio R (= ΣP ₁ / ΣP ₂ ) is calculated. FIG. 8A schematically shows signals input to the peak detectors 22a and 22b. The peak power P _peak is the power at the peak point P in FIG. 8A, ΣP ₁ is the sum of the power in the peak period t ₁ , and ΣP ₂ is the peak period excluding the peak period t ₁ is the power sum of the period t _2. Here, the peak period t ₁ is a period including the base of the peak. For example, as shown in FIG. 9, when DSSS is used as a modulation method, a base that is twice the period tc of the spreading code is formed. Therefore, the period of 2 · tc can be set to the peak period t ₁ . In FIG. 9, the period t ₂ is expressed as tb−2 · tc using the 1-bit period tb.

FIG. 10 shows an example of signals input to the peak detectors 22a and 22b when a received signal is captured using an AD converter. The horizontal axis t in FIG. 10 indicates the sample number, and t takes a discrete value. 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 AD conversion is oversampling four times as long as one chip period, the base spreads by one chip, and ips = ip−3 and ipe = ip + 3. In this case, R is represented by the following formula (12).

In step 203, the peak detectors 22a and 22b compare the calculated ratio R (= ΣP ₁ / ΣP ₂ ) with a predetermined threshold value R _th . When R is larger than _Rth , the peak detectors 22a and 22b output signals to that effect to the timing controllers 23a and 23b. The timing control unit 23a receives a signal indicating that R than R _th is large, and outputs the arrival angle calculating section 24 a signal required for calculating the arrival angle as the peak is present in the received signal. 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 _Rth , the peak detection units 22a and 22b output signals to that effect to the timing control units 23a and 23b, and the timing control unit 23a assumes that there is no peak in the received signal. The output to the calculation unit 24 is stopped. Then, the arrival angle calculation device 1 executes the flow from step 201 again. _Rth is an arbitrary value. For example, a value that can determine the presence or absence of a peak by comparison with R can be set as _Rth .

As described above, the presence or absence of the peak can be accurately determined by comparing the index (R) with respect to the detected peak and the threshold (R _th ) to determine the presence or absence of the peak.

Here, a method of simply determining the presence or absence of a peak by comparing power (power) and a power threshold value will be considered. FIG. 8B schematically shows a signal with a high background level (solid line) and a signal with a low background level (dotted line). When the background level is low as indicated by a dotted line in FIG. 8B, the peak can be detected by comparing the power peak value with the power threshold value _Pth . However, as shown by the solid line in FIG. 8B, when the background level becomes high enough to exceed _Pth , no peak can be detected even if the power peak value is compared with _Pth . This is because the background level cannot be considered in a simple comparison between the power peak value and the power threshold value. Therefore, as shown in this embodiment, the presence or absence of a peak can be accurately determined by using an index that takes the background level into account for peak detection.

As described above, the angle-of-arrival calculation device according to the present embodiment obtains a ratio between the power in the peak period and the power in the remaining period other than the peak period, and compares the obtained ratio with a threshold value. By determining whether or not there is a peak, the peak of the desired wave can be accurately detected and used for calculation of the arrival angle even when the background level of the received wave is high. That is, since the arrival angle is not calculated from signal components other than the desired wave, the calculation accuracy of the arrival angle can be improved.

FIG. 11 is a block diagram illustrating another aspect of the arrival angle calculation unit 24 in the arrival angle calculation apparatus 1. Arrival angle calculator shown in FIG. 11. 24, a complex conjugate unit 51 which takes the complex conjugate of the output _{O a1} of the timing control unit 23a, and an output _{O a1'} complex conjugate unit 51, the output _{O a2} of the timing controller 23b A complex multiplication unit 52 that performs complex multiplication, and an arctangent unit 53 that performs an arctangent calculation using the output of the complex multiplication unit 52. The operations and functions of the complex conjugate unit 51, complex multiplication unit 52, and arc tangent unit 53 are the same as the operations and functions of the complex conjugate unit 41, complex multiplication unit 42, and arc tangent unit 43 described above. Further, 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, and a phase difference correction unit 54 The phase difference recorrection unit 56 that corrects the calculation result (average value) of the averaging unit 55 when the correction is performed in FIG. 5 and the arrival angle conversion unit 57 that converts the arrival angle using the output of the phase difference recorrection unit 56. And comprising. The operation and function of the arrival angle conversion unit 57 are the same as the operation and function of the arrival angle conversion unit 46 described above.

When the phase difference that is the calculation result of the arc tangent unit 53 becomes a value near + 180 ° (+ π) or near −180 ° (−π), the phase difference correction unit 54 adds a predetermined value to the calculation result of the arc tangent unit. Processing to add an angle (phase difference) is performed. As shown in the IQ plane of FIG. 12, the arrival angle calculation unit 24 of the present embodiment projects the phase difference onto the coordinates of the phase difference range of −180 ° to + 180 ° (−π to + π). For this reason, for example, as shown in FIG. 13A, when the phase difference calculated by the arc tangent portion 53 does not become a value in the vicinity of + 180 ° and −180 °, this is appropriately averaged. The arrival angle can be calculated. However, as shown in FIG. 13B, when the phase difference calculated by the arc tangent unit 53 becomes a value in the vicinity of +180 and −180, a slight error in the calculated phase difference has a great influence on the angle calculation. Will give. Here, two values of −178 ° and + 178 ° are obtained as phase difference data, and one value of + 178 ° has an error of −178 ° from the original value of −178 ° to + 178 °. Assuming that These differences are actually only 4 °. However, when averaging is performed as −178 ° and + 178 ° in the averaging process, the average value becomes 0 °. In reality, although there is a phase difference of about 180 °, it is treated as 0 ° by the averaging process. As described above, when the averaged phase difference greatly deviates from the original phase difference, it is difficult to calculate an appropriate arrival angle.

Therefore, when the phase difference calculated by the arc tangent unit 53 becomes a value near + 180 ° and −180 °, the arrival angle calculation unit 24 shown in FIG. A correction process for adding a predetermined angle (phase difference) to the result is performed so that appropriate averaging is performed. Whether the calculation result of the arc tangent unit 53 is a value near + 180 ° or −180 ° can be determined based on a plurality of phase difference distributions obtained as the calculation result of the arc tangent unit 53. For example, when the number of phase differences larger than + 90 ° (+ π / 2) or smaller than −90 ° (−π / 2) is larger than the number of phase differences smaller than + 90 ° and larger than −90 °. It can be determined that the calculation result of the arc tangent portion 53 is a value near + 180 ° and −180 °. The angle (phase difference) applied by the phase difference correction unit 54 can be set to, for example, + 90 °, but is not limited to this as long as an appropriate averaging process is possible. Preferably, any of -90 °, + 180 °, or -180 ° may be used.

The averaging unit 55 averages the output of the phase difference correction unit 54. Since the arrival angle calculation unit 24 of the present embodiment performs correction to add a phase difference when a phase difference that is not suitable for averaging is calculated, the averaging unit 55 can perform an appropriate averaging process. The phase difference recorrection unit 56 corrects the output of the averaging unit 55 when the phase difference correction unit 54 corrects the phase difference. Specifically, correction is performed to reduce the angle (phase difference) added as a correction value in the phase difference correction unit 54.

FIG. 14 schematically shows the calculation of the arrival angle when the phase difference is near + 180 ° and −180 °. When the phase difference calculated by the arc tangent unit 53 is near + 180 ° and −180 ° on the IQ plane, the phase difference correction unit 54 adds a correction value (+ 90 °) to the phase difference and rotates the coordinate axis, Convert to the coordinate axis for average value 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 inverse sine unit 57.

FIG. 15 is a processing flowchart in the arrival angle calculation unit 24. In step 301, the complex conjugate unit 51 of the arrival angle calculation unit 24 calculates the complex conjugate of the output O _a1 of the timing control unit 23a. Also, complex multiplier 52, in step 302, multiplying the output _{O a1'} output _{O a2} and complex conjugate unit 51 of the timing controller 23b. In step 303, the arc tangent unit 53 performs an arc tangent calculation using the output of the complex multiplier 52, and calculates a phase difference between the received signals.

In step 304, the phase difference correction unit 54 determines whether the calculated phase difference is a value in the vicinity of + 180 ° and −180 ° on the IQ plane. When the calculated phase difference is not a value in the vicinity of + 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. If the calculated phase difference is a value near + 180 ° or near −180 °, the process proceeds to step 306. As described above, the determination is performed based on whether the number of phase differences larger than + 90 ° or smaller than −90 ° is larger than the number of phase differences smaller than + 90 ° and larger than −90 °. Can do.

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 output of the phase difference correction unit 54. In step 308, the phase difference recorrection 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 from the output of the phase difference recorrection unit 56. In this way, the arrival angle calculation unit 24 shown in FIG. 11 calculates an appropriate average value by a series of processes of adding a predetermined phase difference and averaging and then reducing the predetermined phase difference. The calculation accuracy does not decrease. As a result, the calculation accuracy of the arrival angle can be sufficiently increased.

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 the present invention is not limited to this as long as an appropriate averaging process can be realized. For example, the arrival angle calculation unit 24 configured as shown in FIG. 16 may be used. Arrival angle calculator 24 shown in FIG. 16, a complex conjugate unit 61 which takes the complex conjugate of the output _{O a1} of the timing control unit 23a, and an output _{O a1'} complex conjugate unit 61, an output _{O a2} of the timing controller 23b A complex multiplier 62 for performing complex multiplication. The operations and functions of the complex conjugate unit 61 and the complex multiplication unit 62 are the same as the operations and functions of the complex conjugate unit 41 and the complex multiplication unit 42 described above. Further, an IQ comparison unit 63 that compares the absolute value of the in-phase component (I component) and the absolute value of the quadrature component (Q component) of the output of the complex multiplication unit 62, and the output of the complex multiplication unit 62, the IQ comparison unit is used. And an arc tangent unit 64 that performs arc tangent calculation by selecting and changing the calculation method according to the output of 63. Also, an averaging unit 65 that averages the phase difference that is the calculation result of the inverse tangent unit 64, and a phase difference reconstruction that corrects the average value that is the calculation result of the averaging unit 65 according to the calculation method of the inverse tangent unit 64. The correction part 66 and the arrival angle conversion part 67 which converts into an arrival angle using the output of the phase difference re-correction part 66 are provided. The operation and function of the arrival angle conversion unit 67 are the same as the operation and function of the arrival angle conversion unit 46 described above.

The IQ comparison unit 63 determines whether or not the in-phase component (I component) of the output of the complex multiplication unit is negative, and the absolute value of the in-phase component (I component) of the output of the complex multiplication unit 62 and a quadrature component ( The absolute value of the Q component is compared. Specifically, the IQ comparison unit 63 determines the sign of the in-phase component Ib and determines whether the absolute value | Ib | of the in-phase component is sufficiently larger than the absolute value | Qb | Whether the value | Qb | is sufficiently smaller than the absolute value | Ib | of the in-phase component) is determined. When the phase difference of the received signal takes values in the vicinity of + 180 ° and −180 ° on the IQ plane, the in-phase component Ib becomes negative (Ib <0), and the absolute value | Ib | Is sufficiently larger than the absolute value of | Qb |. Therefore, by determining the sign of the in-phase component Ib and determining whether the absolute value | Ib | of the in-phase component is sufficiently larger than the absolute value | Qb | of the quadrature component, the phase difference is + 180 ° and −180 °. It can be determined whether or not a value in the vicinity is taken.

The arc tangent unit 64 uses the output of the complex multiplication unit 62, selects an operation method according to the output of the IQ comparison unit 63, and performs an arc tangent calculation. When the in-phase component is positive, or when the in-phase component is negative and the absolute value | Ib | of the in-phase component is equal to or smaller than the absolute value | Qb | of the quadrature component, An arc tangent operation is performed on the value with the output Ib as the denominator and the output Qb as the numerator. When the in-phase component is negative and the absolute value | Ib | of the in-phase component is sufficiently larger than the absolute value | Qb | of the quadrature component, for example, −Qb obtained by inverting the sign of the output Qb of the complex multiplier 62 is used as the denominator. The arc tangent of the value with the output Ib as the numerator is performed. Note that the above processing when the absolute value | Ib | of the in-phase component is sufficiently larger than the absolute value | Qb | of the quadrature component corresponds to processing for performing an arctangent calculation by rotating the coordinate axis by + 90 °. That is, the phase difference obtained by this processing is a value obtained by adding + 90 ° to the original phase difference.

Note that 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. For example, an arctangent operation may be performed on a value using the output Qb of the complex multiplier 62 as the denominator and −Ib obtained by inverting the sign of the output Ib as the numerator. This process corresponds to a process of performing an arctangent calculation by rotating the coordinate axis by −90 °. That is, the phase difference obtained by this processing is a value obtained by adding −90 ° to the original phase difference (a value obtained by subtracting + 90 °). Further, for example, the arc tangent calculation may be performed by inverting the sign of the output Ib of the complex multiplier 62 and the sign of the output Qb. This process corresponds to a process of performing an arctangent calculation by rotating the coordinate axis by + 180 ° (or −180 °). In other words, the phase difference obtained by this processing is a value obtained by adding + 180 ° (or −180 °) to the original phase difference. An appropriate average value can be calculated also by such processing.

The averaging unit 65 averages the output of the arc tangent unit 64. Since the arrival angle calculation unit 24 of the present embodiment performs a correction that substantially adds (or reduces) a phase difference when a phase difference that is not suitable for averaging is calculated, the averaging unit 65 performs appropriate averaging. Processing is possible. The phase difference re-correction unit 66 corrects the output of the averaging unit 65 when the arctangent unit 64 is performing a process of rotating the coordinate axis by + 90 °. Specifically, correction is performed to reduce + 90 °. When the arc tangent unit 64 performs a process of rotating the coordinate axis by −90 °, correction for reducing −90 ° (ie, correction for adding + 90 °) is performed. Similarly, when the arc tangent unit 64 performs a process of rotating the coordinate axis by + 180 ° (or −180 °), correction is performed to reduce + 180 ° (or −180 °).

Thus, the arrival angle calculation unit 24 shown in FIG. 16 can calculate an appropriate average value in the same manner as the arrival angle calculation unit 24 shown in FIG. As a result, the calculation accuracy of the arrival angle can be sufficiently increased.

FIG. 17 is a block diagram showing a specific configuration example of an arrival angle calculation apparatus when orthogonal frequency division multiplexing (OFDM) is used as a modulation method. Note that FIG. 17 shows only the configuration corresponding to the calculation unit 13 in FIG.

In FIG. 17, the correlation processing unit 21a includes a complex conjugate unit 71a that takes a complex conjugate of the output of the receiving unit 12a, a delay unit 72a that outputs the output of the receiving unit 12a after being delayed by a predetermined period, and a complex conjugate unit 71a. A complex multiplier 73a that performs complex multiplication of the output and the output of the delay unit 72a, and adders 74a and 74b that add and output the output of the complex multiplier 73a for a GI (guard interval) period are provided. The peak detector 22a includes a power calculator 75a that calculates the power of the signals output from the adders 74a and 74b, and a peak power detector 76a that detects the power peak and outputs the detected power peak to the timing controller 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 arrival angle 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 includes a delay unit 77b. The arrival angle calculation unit 24 includes a complex conjugate unit 81 that takes a complex conjugate of the output of the delay unit 77a, a complex multiplication unit 82 that performs complex multiplication of the output of the complex conjugate unit 81, and the output of the delay unit 77b, and a complex multiplication unit 42. Are added for the GI (guard interval) period, and are output by the addition units 83a and 83b, the inverse tangent unit 84 that performs an inverse tangent calculation using the outputs of the addition units 83a and 83b, and the output of the inverse tangent unit 84. An averaging unit 85 for averaging, and an arrival angle conversion unit 86 for converting into an arrival angle using the output of the averaging unit 85 are provided.

The delay units 72a and 72b delay the output of the receiving unit 12a by a predetermined period and output the auto-correlation of the OFDM symbol sequence. Specifically, the delay units 72a and 72b input to the complex multiplication unit 73a at the same timing as the end of the OFDM symbol output from the complex conjugate unit 71a and the GI (guard interval) output from the delay units 72a and 72b. As described above, the output of the receiving unit 12a is output after being delayed by a predetermined period. The complex multiplier 73a performs complex multiplication on the output of the complex conjugate unit 71a and the output of the delay unit 72a. The adders 74a and 74b add the outputs of the complex multiplier 73a for each chip section for the GI period and output the result.

FIG. 18A is a schematic diagram showing a configuration of an OFDM symbol string. As shown in FIG. 18A, the OFDM symbol string is composed of an OFDM symbol that is a data part and a GI that is arranged at the head of the OFDM symbol. GI is data obtained by copying the end of the OFDM symbol, and is inserted to prevent interference between OFDM symbols. FIG. 18B is a schematic diagram illustrating a state of correlation processing (autocorrelation processing) of the OFDM symbol sequence in the correlation processing unit 21a. As shown in FIG. 18A, the output of the delay unit 72a is delayed by the OFDM symbol length with respect to the output of the complex conjugate unit 71a. For this reason, in the complex multiplier 73a, 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 unit 71a and the output of the delay unit 72a. The head can be detected.

The output signals of the adders 74a and 74b are input to the power calculator 75a of the peak detector 22a. The power calculator 75a calculates the power for each chip section from 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 calculates the peak power detection unit 76a as power information for each chip section. Output to. Note that 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 together and output to the peak power detection unit 76a. FIG. 19A shows an example of an output waveform from the power calculator 75a. FIG. 19B is a partially enlarged view of the output waveform shown in FIG. When the peak power detection unit 76a receives the power information for each chip section, the peak power detection unit 76a detects the power peak in the received signal and outputs the detected power peak information to the delay unit 77a of the timing control unit 23a.

The power peak information output from the peak detector 22a (peak power detector 35a) is information for determining whether or not there is a peak in the received signal. Specifically, the power peak information includes power sum ΣP ₁ in a period near the peak point of the received signal (peak period) and power in a period obtained by excluding the peak period from one symbol period that is an information unit in OFDM. This is information indicating whether the ratio R (= ΣP ₁ / ΣP ₂ ) with the sum ΣP ₂ is greater than the threshold value R _th . When OFDM is used as the modulation method, the peak period is equal to the GI period. One symbol period corresponds to a total period of a GI period and a data period (OFDM symbol period). In the peak power information, if R is greater than R _th, the timing controller 23a (delay unit 77a) as to have a peak received signal at that timing, arrival angle calculator receiving signals from the receiving unit 12a 24. On the other hand, when R is R _th smaller than, the timing controller 23a (delay unit 77a), in its timing as the reception signal has no peak, and stops the output to the arrival angle calculator 24. Here, the peak detection unit 22a performs the calculation process related to the power peak information, but the calculation process related to the power peak information may be performed in the timing control unit 23a.

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 unit) 77b) includes the correlation processing unit 21a (complex conjugate unit 71a, delay unit 72a, complex multiplication unit 73a, adders 74a and 74b), peak detection unit 22a (power calculation unit 75a, peak power detection unit 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 because the same radio wave is received at two points separated by a predetermined interval. For this reason, the signal output from the timing control unit 23b and the signal output from the timing control unit 23a are slightly different in phase.

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 multiplier 82 complex-multiplies the output of the complex conjugate unit 81 and the output of the timing controller 23b, and outputs the calculation result to the adders 83a and 83b. The adders 83a and 83b add the outputs of the complex multiplier 82 for each chip interval for the GI period and output the sum to the arctangent unit 84. FIG. 19C shows an example of output waveforms from the adders 83a and 83b. In the figure, the output waveform of the adder 83a is indicated by I, and the output waveform of the adder 83b is indicated by Q.

The arc tangent unit 84 performs an arc tangent calculation using the outputs of the adders 83a and 83b, and calculates the phase difference of the received signal. FIG. 19D shows an example of an output waveform from the arc tangent portion 84. The averaging unit 85 averages the output of the arc tangent unit 84 and outputs it to the arrival angle conversion unit 86. The averaging unit 85 may be omitted as appropriate. The arrival angle conversion unit 86 converts the arrival angle by the inverse trigonometric function calculation using the output of the averaging unit 85 (or the output of the arctangent unit 84 when the averaging unit 85 is not provided). The value obtained by the calculation, that is, the output of the arrival angle conversion unit 86 corresponds to the arrival angle.

As described above, the arrival angle calculation apparatus 1 having the calculation unit 13 in FIG. 17 also obtains the ratio between the power in the peak period and the power in the remaining period other than the peak period, and calculates the ratio and the threshold value. By comparing the presence or absence of a peak by comparison, the peak of the desired wave can be accurately detected and used for the calculation of the arrival angle even when the background level of the received wave is high. That is, since the arrival angle is not calculated from signal components other than the desired wave, the calculation accuracy of the arrival angle can be improved.

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

¡The capsule endoscope swallowed by the patient moves by the peristaltic movement of the digestive tract. The position of the capsule endoscope is monitored, and it can be confirmed whether or not the examination site has been reached. When the capsule endoscope reaches the examination site, the capsule endoscope captures the state of the examination site and transmits it to the data recorder 402, and the data recorder 402 records image information. Thus, by monitoring the position of the capsule endoscope, it is possible to take an image without missing the examination site. In addition, the camera can be turned on when the capsule endoscope reaches the examination site, and the camera capacity can be turned off when the examination site is removed, thus reducing the battery capacity. . In addition, the number of sensors (antennas) can be reduced. Further, if the battery capacities are the same, a larger number of images can be transmitted as compared with the conventional capsule endoscope, and a clear image can be obtained.

Thus, an excellent capsule endoscope system can be constructed by applying the arrival angle calculation device 1 to the position specification of the capsule endoscope.

As described above, according to the arrival angle calculation device of the present invention, the ratio between the power in the peak period and the power in the remaining period other than the peak period is obtained, and the obtained ratio is compared with the threshold value. Since the arrival angle is calculated when is greater than the threshold value, the peak of the desired wave can be accurately detected and the arrival angle can be calculated even when the signal level of the received wave other than the desired wave is high. . That is, since the arrival angle is not calculated from a portion other than the desired wave, the calculation accuracy of the arrival angle can be improved.

In addition, this invention is not limited to description of the said embodiment, It can change suitably in the aspect which exhibits the effect. For example, in the above embodiment, the ratio of the sum of power during the peak period and the sum of power during the period excluding the peak period is compared with the threshold value, but the level of the signal other than the desired wave is considered. The present invention is not limited to this as long as the arrival angle can be calculated. For example, power at a certain timing in the peak period and power at a certain timing other than the peak period may be used as parameters.

Further, in the above embodiment, the configuration shown in the attached drawings is not limited to this, and can be appropriately changed within a range in which the effect of the present invention is exhibited.

The arrival angle calculation apparatus of the present invention can be used for a system for identifying a target position and other various uses.

This application is based on Japanese Patent Application No. 2010-254011 filed on Nov. 12, 2010. All this content is included here.

Claims (9)

1. A plurality of antennas for receiving radio waves transmitted from a certain position, a plurality of reception signal processing units provided corresponding to the respective antennas, and reception signal processing from output signals output from the plurality of reception signal processing units An angle-of-arrival calculation unit that takes in a signal component that is the same information unit between the units and calculates the angle of arrival of the radio wave,
   Each reception signal processing unit performs correlation processing on a reception unit that converts a radio wave received by the corresponding antenna into a reception signal having phase information of the radio wave, and a reception signal output from the reception unit. A processing unit, a peak detection unit that detects a peak of the correlation-processed reception signal, and a signal component that is the same information unit between the reception signal processing units from the output signal of the correlation processing unit, In accordance with the timing of the peak detected by the peak detection unit, a timing control unit that controls the capture timing of the output signal output from the correlation processing unit, and
   The timing control unit receives the signal from the correlation processing unit if the ratio between the power in the peak period in the period corresponding to the information unit and the power in the period excluding the peak period is greater than a threshold value. An angle-of-arrival calculation apparatus that outputs to an angle calculation unit.
2. The timing control unit compares a ratio ΣP ₁ / of the sum ΣP ₁ of power in a peak period in a period corresponding to the information unit and the sum ΣP ₂ of power in a period excluding the peak period in a period corresponding to the information unit. The ΣP ₂ is compared with a threshold value, and when the ratio ΣP ₁ / ΣP ₂ is larger than the threshold value, a signal from the correlation processing unit is output to the arrival angle calculation unit. The arrival angle calculation device according to 1.
3. The arrival angle calculation unit
   A complex conjugate unit that takes a complex conjugate of the signal from the timing control unit of one received signal processing unit corresponding to one antenna;
   A complex multiplier that multiplies the output of the complex conjugate unit by the signal from the timing control unit of the other received signal processing unit corresponding to the other antenna;
   An arc tangent is calculated using the output of the complex multiplier, and an arc tangent for calculating a phase difference of the received radio wave between the antennas;
   An averaging unit that averages the output of the arctangent,
   The arrival angle calculation device according to claim 1, further comprising: an arrival angle conversion unit that performs an inverse trigonometric function operation using an output of the averaging unit and converts the result into an arrival angle.
4. When the calculated phase difference is distributed in the vicinity of + 180 ° and / or −180 ° on the IQ plane, the arrival angle calculation unit averages each phase difference after rotating it by a predetermined angle. The arrival angle calculation device according to claim 3, wherein the predetermined angle is subtracted from the average value to perform an inverse trigonometric function calculation to convert the average angle into an arrival angle.
5. On the IQ plane, when the number of phase differences larger than + 90 ° or smaller than −90 ° is larger than the number of phase differences smaller than + 90 ° and larger than −90 °, The arrival angle calculation device according to claim 4, wherein the arrival angle calculation device determines that the distribution is in the vicinity of + 180 ° and / or -180 °.
6. 6. The arrival angle calculation apparatus according to claim 4, wherein the predetermined angle is any one of + 90 °, −90 °, + 180 °, and −180 °.
7. When the I component of the output of the complex multiplier is negative and the absolute value of the I component of the output of the complex multiplier is sufficiently larger than the absolute value of the Q component, the sign of the Q component is inverted. The corrected phase difference is calculated by performing an arctangent calculation in which the relationship between the I component and the Q component is exchanged, and the corrected phase difference is averaged, and 90 ° is subtracted from the average value to obtain an inverse trigonometric function. 4. The arrival angle calculation apparatus according to claim 3, wherein the calculation is performed to convert the arrival angle into an arrival angle.
8. When the I component of the output of the complex multiplier is negative and the absolute value of the I component of the output of the complex multiplier is sufficiently larger than the absolute value of the Q component, the sign of the I component is inverted. The corrected phase difference is calculated by performing an arc tangent calculation in which the relationship between the I component and the Q component is exchanged, and the corrected phase difference is averaged, and 90 ° is added to the average value to obtain an inverse trigonometric function. 4. The arrival angle calculation apparatus according to claim 3, wherein the calculation is performed to convert the arrival angle into an arrival angle.
9. When the I component of the output of the complex multiplier is negative and the absolute value of the I component of the output of the complex multiplier is sufficiently larger than the absolute value of the Q component, the sign of the I component and the sign of the Q component The phase difference corrected by calculating the arc tangent after inverting is calculated, the corrected phase difference is averaged, 180 ° is subtracted from the average value, and the inverse trigonometric function is calculated. The angle-of-arrival calculation device according to claim 3, wherein

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