JP2000338215A - Precise measurement method of receiving azimuth in narrow band signal detection processing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method capable of precisely measuring receiving azimuth in narrow-band signal detection processing, without weighing hardwear and increasing the amount of data and operation. SOLUTION: An input signal (S1) from each receiving wave beam in a sector is subjected to FFT processing (S2). A peak of the signal intensity is detected (S3). When the peak position (S4) is not a sector end (S5), the beam number of the receiving wave beam in which the peak is detected is made B. The numbers of three points whose center is B are made (B-1), B and (B+1), and the signal intensities are made A, A0 and A+, respectively. Precise measurement beam number Bfinc of the receiving azimuth is made Bfinc=B+p/2q (where p=A+-A, q=2A0-A+-A) and calculated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a precision measuring method for receiving and detecting a narrow band signal from a signal source and measuring the receiving direction.

[0002]

2. Description of the Related Art Generally, when a narrow band signal such as an acoustic wave or an electromagnetic wave from a signal source is received and detected, and the receiving direction is measured or tracked, data is obtained in a two-dimensional space of direction versus frequency. Since it is necessary to collect and analyze the data in detail, it is desirable to collect the azimuth data using a large number of beams with a narrow beam width and a sufficiently small interval.

[0003] As a known document of this technology, for example, a "signal tracking method" disclosed in Japanese Patent Application Laid-Open No. 8-15402 is disclosed.
There is. The signal tracking device according to the embodiment of the above-mentioned known document receives a narrow band signal from an unknown sound source 1 having an azimuth θ1 and a frequency f1 by a plurality of reception beams B1, B2,. It has a wavy acoustic array sensor 2. On the output side of the acoustic array sensor 2, a frequency for performing a Fourier transform of a received signal of each received beam Bi (i = 1, 2,..., N) to obtain a signal intensity distribution in a frequency space at each sample time The analyzer 3-i is connected. The output side of each frequency analyzer 3-i has a storage device 4-i for storing a signal intensity distribution in a frequency space at each sampling time and an unknown sound source 1 by detecting a signal peak in the signal intensity distribution. A peak detector 6 for detecting the azimuth θ1 and the frequency f1 of the narrowband signal from is connected. That is, regarding the receiving direction of the signal source, a plurality of receiving beams B1, B2, pointing in directions slightly different from each other.
.. Bn indicate that the wave is being received.

[0004]

However, according to the above-mentioned conventional method, a narrow band signal is received and analyzed separately for each direction slightly different from each other, so that a wave receiving sensor array, a frequency analyzer, a storage device, and a peak detector are used. And the like, and with the increase in the amount of data, problems such as hardware resources arise. Also, for some reason, there may be cases where a large number of beams cannot be densely collected, or cases where azimuth data cannot be detected with three or more beams below a certain frequency. However, the above-described conventional technique does not consider such a case. Next, the receiving direction of the signal is calculated. Therefore, in this case, the azimuth calculation result includes a considerable error, and a azimuth satisfying the accuracy is not obtained.

[0005]

According to the present invention, there is provided a method for measuring a receiving direction in a narrow band signal detecting process, wherein a narrow band is detected by using a plurality of receiving beams pointing in different directions within a predetermined sector. A signal is received, and a signal intensity distribution in a two-dimensional space of a beam-to-frequency obtained by frequency-analyzing a reception signal of each of the reception beams is used for each frequency at a maximum point of the signal intensity distribution and at a predetermined point. In the method of detecting the presence of the narrow-band signal by detecting a peak value exceeding the threshold value and precisely measuring the reception direction, when the peak of the signal strength is not at the end of the sector, the peak is detected. B-beam numbers of receive beam, the beam number three points centered on the B (B-1), B , (B + 1), a the signal strength respectively ^-, a ^0, a ⁺ to the , Precise beam number of receiving direction The _{B fine, B fine = B +} p / 2q ( where, p = A ⁺ -A ^- to ^{-, q = 2A 0 -A +} -A) and calculates a.

As a result, even if it is not necessary to increase the data amount and the amount of calculation of the received signal by making the hardware heavy as in the conventional case, and even if the reception beam cannot be densely provided, most of the area within the sector can be obtained. , The direction of arrival of the signal can be calculated with high accuracy.

[0007]

FIG. 2 is an explanatory view of a sensor array, beam numbers and sectors according to an embodiment of the present invention. 2, the sensor array includes sensors 1 to m arranged in a straight line. The arrangement interval may be equal or unequal depending on the system.
In the present embodiment, each sensor is an acoustic sensor that receives an acoustic wave.

This sensor array has a plurality of beams having directional characteristics in directions slightly different from each other within a certain azimuth range (this is referred to as a sector; in FIG. 2, azimuth range from beam 1 to beam n). (Beam 1, Beam 2,
.., Beam n) can be formed and acoustic waves in a continuous azimuth range can be received. Each beam indicated by an arrow in FIG. 2 indicates the center direction of each received beam (having a beam width). As described above, in the present embodiment, the center direction of each beam is indicated as the direction or position of each beam number. Therefore, the beam width has the meaning of the azimuth difference (angle). In FIG. 2, beam 1 and beam n are the beam numbers at the ends of the sector.

FIG. 1 is a flowchart of an azimuth accurate measurement method in a narrow band signal detection process according to an embodiment of the present invention.
The numerical value following "" indicates a step number. First, an FFT (Fast Fourier Transform) analysis is performed on a narrow band signal received for each beam number in each direction by the sensor array of FIG.
S2). FIG. 3 is an explanatory diagram of the FFT result on the beam versus frequency space according to the embodiment of the present invention. The horizontal axis of the figure indicates the beam number, the vertical axis indicates the frequency, and the data in each lattice indicates the received signal strength.

Next, a peak value is detected from the signal composed of the beam (azimuth) and the frequency component (S3 in S1). This peak is detected by searching for a point that is the maximum point in the output for each frequency and whose output value exceeds a predetermined threshold (S4 in FIG. 1). The circles in the grid in FIG. 3 indicate the positions where the peaks were detected.
Numbers 1, 2, and 3 in the circles indicate the peak detection positions in Pattern 1, Pattern 2, and Pattern 3 described later.

Further, using three beams around the peak including the beam from which the peak is obtained, a highly accurate peak position is calculated by parabolic interpolation using one of the three patterns described later (S4 in FIG. 1). ). That is, when the beam at which the peak is obtained is not at the end of the sector, the method of pattern 1 described with reference to FIG. 5 is used (S5 in FIG. 1). It is determined whether a certain frequency f _{0 is} smaller or larger (S6 in FIG. 1),
If it is less than f ₀ is (S7 in FIG. 1) pattern using two of the methods described in FIG. 6, in the case of f ₀ above using the method of pattern 3 as described in FIG. 7 (S8 of Fig. 1).

In order to precisely measure the receiving direction of the narrow band signal, the direction is calculated in three cases of pattern 1, pattern 2 and pattern 3 described below. First, a certain frequency f ₀ used when pattern 2 and pattern 3 are properly used.
Will be described. Figure 4 is an explanatory view of a half-width at half maximum beam width W ₁ of the parabola according to the embodiment of the present invention. Now, when the beam 1 of the beam number is directed toward the end of the sector and the sound source exists in the end of this sector, the signal strength becomes
The maximum value is Smax at the peak 1, the value is less than Smax for the beam 2, and is often zero for the beam 3. In this case, the signal intensity as shown in FIG. 4 can draw a parabola passing through zero of Smax and the beam 3 of the beam 1, obtaining the beam width W ₁ which is a half width at half maximum on the parabola. The beam width W ₁ is a difference (physical direction difference Δθ) between the center direction (hereinafter simply referred to as beam 3) and the center direction of beam 1 (hereinafter simply referred to as beam 1) as shown in the following equation (3). , Which is treated here as the difference between beam numbers) as a quotient obtained by dividing by the square root of 2.

[0013]

(Equation 2)

The physical meaning of the half-width half-width beam width W ₁ is, as shown in FIG. 4, a beam from a beam 1 having a peak value Smax of signal intensity to a beam number having a half-value Smax / 2 along a parabola. Means width. Note that it is called a half width because it is half of a general beam width obtained between both sides of the parabola.

Next, a decision is made by the receiving system of the array sensor.
(Beam width) x (frequency) dimension
Set a constant K with options. And this K is a certain frequency
Number f ₀The quotient divided by W₁F₀Is
Determined from (4) and (5). W₁= K / f₀ … (4) f₀= K / W₁ (5) In FIG. 3, among the reception frequencies 1, 2,.
Equation 4 is f₀Is shown. And of the sector
There is a peak at the end (beam 1 or beam n in FIG. 2)
The frequency of this peak is f₀Smaller or larger
Pattern 2 or pattern 3 to be described later
Is performed. In the example of FIG.
Peak frequency 2 of f₀Less than the number 3 peak in the circle
Frequency 8 is f₀This indicates that this is the case.

Pattern 1 (case other than end of sector (FIG. 3
FIG. 5 is an explanatory diagram of a signal intensity distribution in a case other than the sector end according to the embodiment of the present invention. In FIG. 5, the beam number of the received beam at which the peak is detected is B. The beam numbers of three points centered on B are (B-1), B, (B +
1) and, ^A the signal strength respectively - and A ^0, A ⁺ take, Seihaka beam number B _fine is represented by the following formula (6). _{B fine = B + p / 2q} ... (6) ^{However, p = A + -A - q} = 2A 0 -A + -A - it is. If q = 0, B is set to B _fine as it is.

Pattern 2 (when the frequency of the peak at the end of the sector is lower than a certain frequency f ₀ (peak of numeral 2 in the circle in FIG. 3)) FIG. 6 shows the peak at the end of the sector according to the embodiment of the present invention. FIG. 4 is an explanatory diagram of a signal intensity distribution when the frequency of the signal is less than f ₀ .
In FIG. 6, the beam number at the sector end where the peak is detected is B. The beam numbers at three points from this end are B, (B
+1) and (B + 2), and their signal intensities are A ⁰ , A
Assuming that ¹ , A ² , the precise measurement beam number B _fine is given by the following equations (7) and (8). At the left end of the sector: B _fine = B + 1−p / 2q (7) At the right end of the sector: B _fine = B−1 + p / 2q (8) where p = A ⁰ −A ² q = 2A ¹ −A ⁰ it is -A ^2. If p ≦ 0 or q ≦ 0, the peak is deleted.

Pattern 3 (In the case where the frequency of the peak at the end of the sector is equal to or higher than a certain frequency f ₀ (peak of numeral 3 in a circle in FIG. 3)) First, the relationship between the frequency and the beam width will be described. The beam width is inversely proportional to (array length) × (frequency) of the sensor. That is, when a beam is formed using an array of the same length, the beam width tends to be small at high frequencies and large at low frequencies. Therefore, at a certain frequency f ₀ or more described with reference to FIG. 4, it is difficult to detect an effective signal from the same sound source at a beam number two or more away from a peak beam number.

FIG. 7 is an explanatory diagram of the signal intensity distribution when the peak frequency at the end of the sector is f ₀ or more according to the embodiment of the present invention. First, the frequency of the peaks is f, the half-width at half maximum beam width W _b of the beam number to signal strength space at the frequency of the peak (frequency 8 in the example of FIG. 3), is calculated by the following equation (9). In _{W b = K / f ... (} 9) where K is a constant, it is identical and a constant K used in the W ₁ calculated in equation (4). In FIG. 7, the beam number of the end beam at which the peak is detected is B. The beam numbers at three points from this end are B, (B + 1), (B + 2), and the signal intensities are A ⁰ , A ¹ , A ² (A ⁰ > A ¹ ) in that order.
> A ² ).

First, for safety, it is determined whether or not the following equation (10) holds. A ⁰ −A ² > 1000 × (A ⁰ −A ¹ ) (10) Equation (10) holds. In the case, precise beam field number B
_fine is expressed by the following equations (11) and (12). In the case of the left end of the sector: B _fine = B + 0.5 (11) In the case of the right end of the sector: B _fine = B−0.5 (12) In addition, when Expression (10) is not satisfied, the precise measurement beam number B
_fine is the expression (14), (15) where p is the following expression (13)
Becomes p = (A ⁰ −A ² ) / (A ⁰ −A ¹ ) (13)

[0021]

(Equation 3)

It is also possible to omit the determination of Expression (10) and directly perform the processing of Expressions (14) and (15). This is because Expression (10) is rarely satisfied and is often not satisfied.

As described above, according to the present embodiment, even if the data amount and calculation amount of the received signal are not increased as in the related art, and even if the reception beam cannot be densely provided, the reception within the sector can be performed. By performing calculation processing based on three types of patterns according to the position of the beam where the signal exists and the value of the reception frequency, the arrival direction of the signal can be obtained with high accuracy.

In the above embodiment, the received signal is an acoustic signal. However, any input signal such as an electromagnetic wave can be used as long as it can determine the signal receiving direction, the received frequency, and the received signal strength.

[0025]

As described above, according to the present invention, a predetermined security
Multiple receivers pointing in different directions within the
The narrowband signal using the
Of the beam versus frequency obtained by frequency analysis of the received signal
According to the signal intensity distribution in the two-dimensional space,
Peak at the maximum point of the signal intensity distribution and exceeding a predetermined threshold
Detecting the presence of the narrowband signal by detecting the peak value,
In the method for precisely measuring the receiving direction, the signal strength
If the peak is not at the end of the sector,
The beam number of the detected receiving beam is B, and this B is the center
(B-1), B, (B +
1) The signal strength is A^-, A⁰, A ⁺To be
And the measurement beam number B of the receiving direction_fineAnd B_fine= B + p / 2q (where p = A⁺-A^-, Q = 2A⁰-A⁺-A^-Toss
), So that as a result
The weight of the hardware, and
Without increasing the complexity, it is not possible to obtain
High in most areas within a sector
The arrival direction of the signal can be calculated with high accuracy.

[Brief description of the drawings]

FIG. 1 is a flowchart of an azimuth accurate measurement method in a narrowband signal detection process according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a sensor array, a beam number, and a sector according to the embodiment of the present invention.

FIG. 3 is an explanatory diagram of an FFT result on a beam versus frequency space according to the embodiment of the present invention.

It is an explanatory view of a half-width at half maximum beam width W ₁ of the parabola according to the embodiment of the present invention; FIG.

FIG. 5 is an explanatory diagram of a signal intensity distribution in a case other than the end of a sector according to the embodiment of the present invention.

FIG. 6 is an explanatory diagram of a signal intensity distribution when a peak frequency is less than f ₀ at a sector end according to the embodiment of the present invention.

FIG. 7 is an explanatory diagram of a signal intensity distribution when a peak frequency at a sector end is equal to or more than f _{0 according} to the embodiment of the present invention.

Continued on the front page F term (reference) 5J070 AA02 AC13 AD06 AD08 AH14 AH19 AH35 5J083 AA05 AC17 AD02 AD17 BE12 BE19 BE43 CA07 CA12

Claims (4)

[Claims] 1. A narrowband signal is received using a plurality of receiving beams pointing in mutually different directions within a predetermined sector, and the reception signal of each receiving beam is obtained by frequency analysis. By the signal intensity distribution on the two-dimensional space of beam versus frequency, for each frequency, the presence of the narrow band signal is detected by detecting a peak value exceeding a predetermined threshold at a maximum point of the signal intensity distribution, In the method for precisely measuring the reception direction, when the peak of the signal intensity is not at the end of the sector, the beam number of the reception beam at which the peak is detected is B,
The beam numbers of the three points around B are (B-1),
B, (B + 1), the signal intensity respectively ^A -, ^{A 0,}
When A ^+, the Seihaka beam number B _fine reception _{orientations, B fine = B + p /} 2q ( ^{where, p = A + -A -,} q = 2A 0 -A + -A - to) be calculated as A receiving direction precise measurement method in a narrow band signal detection process, characterized by the following. 2. A narrow-band signal is received by using an array sensor that forms a plurality of reception beams pointing in different directions within a predetermined sector, and the reception signal for each reception beam is frequency-converted. According to the signal intensity distribution in the two-dimensional space of the beam versus frequency obtained by the analysis, the peak value exceeding the predetermined threshold value at the maximum point of the signal intensity distribution for each frequency is detected, so that the narrow band signal is detected. In the method of detecting the presence and precisely measuring the receiving direction, when the peak of the signal strength is at the end of the sector and the frequency of the peak is lower than a predetermined frequency determined by the receiving system of the array sensor, The beam number at the end of the sector where the peak is detected is B, and the beam numbers at three points from this end are B, (B + 1), (B +
2), when the signal strength respectively A ^0, A ^1, A ^2, the Seihaka beam number B _fine reception direction, when the sector left end, when _{B fine = B + 1-p} / 2q sector right end, B _fine = B−1 + p / 2q (where p = A ⁰ −A ² and q = 2A ¹ −A ⁰ −A ² ). 3. A narrow band signal is received by using an array sensor that forms a plurality of reception beams pointing in different directions within a predetermined sector, and the reception signal for each of the reception beams is frequency-converted. According to the signal intensity distribution in the two-dimensional space of the beam versus frequency obtained by the analysis, the peak value exceeding the predetermined threshold value at the maximum point of the signal intensity distribution for each frequency is detected, so that the narrow band signal is detected. In the method of detecting the presence and precisely measuring the receiving direction, when the peak of the signal strength is at the end of the sector and the frequency of this peak is equal to or higher than a predetermined frequency determined by the receiving system of the array sensor, first, as a quotient of the constant determined by the receiving system of the array sensor is divided by the frequency of the peak, determine the half-width at half maximum beam width W _b of the beam number space, then the peak B The beam number of the detected sector edge, the beam number three points from the end B, (B + 1),
(B + 2), and their signal intensities are A ⁰ , A ¹ , and A ^{2 respectively.}
Then, an accurate measurement beam number B _fine of the reception azimuth is calculated by the following equations (1) and (2). (Equation 1) 4. The method according to claim 1, wherein the narrow band signal is an acoustic wave or an electromagnetic wave signal.