JP2009236543A - Radar system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enhance the bearing accuracy without rotating a phased array antenna in relation to a coning error. <P>SOLUTION: A bearing difference between true bearing and estimated bearing caused by the coning error of the phased array antenna that is measured beforehand for each wave angle is stored in a database for calculation of the true bearing. The frequency, pulse width, pulse repetition frequency, pulse arrival time and estimated bearing of a target are detected from an arriving radio wave received separately by the phased array antenna being so set that the antenna array plane thereof is directed in the reference direction and by a multiantenna. Then, a correlation processing is conducted about the frequency, pulse width, pulse repetition frequency and pulse arrival time of the target detected by the two antennas and an estimated wave angle of the correlated target is verified with the wave angle of the database for calculation of the true bearing so as to extract a corresponding bearing difference. Based on the extracted bearing difference, the estimated bearing of the target is corrected and thus the true bearing is calculated. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a radio wave detection apparatus that measures the direction of arrival of radio waves propagating in the atmosphere using a phased array antenna.

  As is well known, when a phased array antenna is used, the arrival direction is calculated from the phase difference (arrival time difference) between the incoming radio waves received by the arrayed element antennas. However, when the radio wave radiation source has an elevation angle with respect to the antenna array surface (horizontal plane), an azimuth variation called a coning error occurs as the arrival direction approaches the side surface direction with respect to the array surface. This occurs because the equiphase surface with respect to the antenna array surface has a cone shape centered on the array. Therefore, in the azimuth measurement using the phased array antenna, when a radio wave having an elevation angle with respect to the antenna array surface arrives in the side surface direction, an error occurs in the calculated estimated azimuth, and the azimuth accuracy decreases. For this reason, a technique has been proposed in which the true bearing is calculated by correcting the estimated bearing when the coning error occurs (see, for example, Patent Document 1).

  In the radio wave detection device described in Patent Document 1, the antenna array surface is mechanically changed so as to change the azimuth direction in consideration of the characteristic that a coning error does not occur in the front direction of the antenna array but increases in the lateral direction. It is configured to rotate horizontally and receive incoming radio waves from the front of the antenna. Also, based on the radio reception data from the front direction of the antenna, for each elevation angle of the radio wave, the antenna rotation angle from the reference, the true azimuth difference due to the coning error, and the azimuth difference between the estimated azimuth are obtained in advance and stored in a database. Keep it. At the time of actual measurement, the estimated azimuth at the reception position where the phased array antenna is rotated in the direction of arrival of the radio wave is calculated, the azimuth difference corresponding to the antenna rotation angle at this time is obtained from the database, and the true Calculate the bearing. The corresponding elevation angle is also acquired.

Japanese Patent Laid-Open No. 2005-181203

  A conventional radio wave detection device using a phased array antenna is configured as described above. However, since the antenna array surface must be rotated, a rotation drive mechanism is required, and control for determining the rotation angle during measurement is performed. It must be made. Further, since the antenna rotation angle must be used to calculate the true orientation, processing time is required accordingly. Furthermore, when a rotational drive mechanism is provided, there are problems such as restrictions on inspection and maintenance.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a radio wave detection device that can improve azimuth accuracy without rotating a phased array antenna against a coning error. .

  The radio wave detector according to the present invention separates the received signal of the incoming radio wave received by the phased array antenna installed with the antenna array surface facing the reference direction for each target, and each target frequency, pulse width, pulse repetition frequency , A first target specification detection unit for detecting a pulse arrival time and an estimated direction, and a received signal of an incoming radio wave received by a multi-antenna is separated for each target, and each target frequency, pulse width, pulse repetition frequency, The second target specification detection unit for detecting the pulse arrival time and the estimated elevation angle is correlated with the target frequency, pulse width, pulse repetition frequency, and pulse arrival time detected by the first and second target specification detection units. A correlation processing unit that performs processing, and a true storage that stores the azimuth difference between the true azimuth and the estimated azimuth caused by the coning error of the phased array antenna measured in advance for each elevation angle. The corresponding azimuth difference is extracted by collating it with the elevation angle of the true azimuth calculation database based on the position calculation database and the estimated elevation angle of the target correlated with the correlation processing unit, and the correlation is performed based on the extracted azimuth difference. A true azimuth calculation processing unit that corrects the estimated azimuth of the target that has been corrected and calculates the true azimuth of the target is provided.

  According to this invention, the radio wave detection device at the time of actual measurement takes out the azimuth difference using the elevation angle acquired by the multi-antenna from the true azimuth calculation database, so it is not necessary to provide the phased array antenna with a rotation drive mechanism. Orientation accuracy can be increased only by electrical processing. Therefore, the problem caused by the conventional rotational drive mechanism is eliminated.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing a functional configuration of a radio wave detection device according to each embodiment of the present invention.
In FIG. 1, the radio wave detection device includes a phased array antenna 1, a multi-antenna 2, receiving units 3 and 4, target specification detecting units 5 and 6, a correlation processing unit 7, a true direction calculation database 8, and a true direction calculation processing unit. 9. A target management unit 10 is provided.
The phased array antenna 1 is an directional antenna that receives incoming radio waves, and the multi-antenna 2 is an elevation angle antenna that receives incoming radio waves. The receiving unit 3 is a unit that detects a target signal from a signal received by the phased array antenna 1, and the receiving unit 4 is a unit that detects a target signal from the received signal by the multi-antenna 2. The target specification detection unit (first target specification detection unit) 5 separates the detected target data for each target, and sets the target specifications such as frequency, pulse width, pulse repetition frequency, pulse arrival time, and estimated direction. It is a means to detect. The target specification detection unit (second target specification detection unit) 6 separates the detected target data for each target and sets the target specifications such as frequency, pulse width, pulse repetition frequency, pulse arrival time, estimated elevation angle, and the like. It is a means to detect. The correlation processing unit 7 is a means by CPU processing for performing correlation processing on the frequency data detected by the both target specification detection units 5 and 6. The true azimuth calculation database 8 is means for storing coning error data measured in advance for each elevation angle. The true azimuth calculation processing section 9 calculates the true azimuth of the incoming radio wave from the corresponding corning error and the estimated target azimuth by matching with the true azimuth calculation database 8 based on the estimated estimated elevation angle of the target. Means by CPU processing. The target management unit 10 is a means based on CPU processing for centrally managing each item and state of the detected target.

Next, the operation will be described according to the processing flow of FIG.
When the incoming radio waves are received by the phased array antenna 1 and the multi-antenna 2, the receiving units 3 and 4 detect target signals from the respective received signals (step ST1). The target data obtained by the receiving units 3 and 4 are given to the corresponding target specification detecting units 5 and 6, respectively. The target specification detection unit 5 detects target specifications such as frequency, pulse width, pulse repetition frequency, pulse arrival time, and estimated azimuth from the detection signal. The target specification detection unit 6 detects target specifications such as a frequency, a pulse width, a pulse repetition frequency, a pulse arrival time, and an estimated elevation angle from the detection signal. (Step ST2). The target specification data detected by the target specification detection units 5 and 6 is sent to the correlation processing unit 7. The correlation processing unit 7 performs correlation processing on the frequency, pulse width, pulse repetition frequency, and pulse arrival time of both detection signals to check whether the same target exists (step ST3). When the same target exists, the estimated azimuth and estimated elevation data of the target are sent to the true azimuth calculation processing unit 9. On the other hand, if the same target does not exist, individual target specification data is sent to the target management unit 10. Next, in the true azimuth calculation unit 9, based on the target estimated elevation angle from the correlation processing unit 7, the true azimuth for each elevation angle stored in advance in the true azimuth calculation error database 8 and the azimuth difference between the estimated azimuths are calculated. Then, an azimuth difference corresponding to the estimated elevation angle is extracted, and a true azimuth is calculated based on the azimuth difference and the estimated azimuth from the correlation processing unit 7 (step ST4). The calculated true azimuth is given to the target management unit 10 and the previously measured target specifications are updated.

Here, the principle of estimating the arrival direction of the incoming radio wave with high accuracy using the coning error characteristic of the phased array antenna will be described.
FIG. 3 is a diagram for explaining a phase difference comparison method of a phased array antenna, and shows a top view of a plurality of element antennas arranged on the XY plane as viewed from above. As shown in the figure, a phased array antenna has a plurality of element antennas arranged in an array, and the arrival azimuth (estimated azimuth) is calculated by a known method from the phase difference between the incoming radio waves received by each element antenna. . At that time, the distribution of equiphase lines has a cone shape with the antenna array surface as an axis, as shown in FIG. Here, EL represents the arrival elevation angle, and AZ represents the arrival direction. When the incoming radio wave has an elevation angle EL, a difference occurs between the arrival direction (true orientation) of the radio wave and the estimated direction due to the relative direction with respect to the antenna array surface, and the elevation angle is 0 on the equiphase line. Is measured as the estimated direction.

  FIG. 5 shows the characteristics of a coning error that occurs in a phased array antenna. When the arrival azimuth is the front direction with respect to the antenna array surface as in A, the estimated azimuth has the same value as the true azimuth regardless of the elevation angle. However, when the arrival direction is close to the side surface direction as in B, a difference in direction occurs between the actual arrival direction (true direction) a at the elevation angle b and the estimated direction c.

FIG. 6 is a schematic diagram showing the relationship between the elevation angle, the azimuth difference, and the true azimuth due to the coning error of the phased array antenna in the coordinate system. In FIG. 6, if a radio wave has arrived from the target T with respect to a phased array antenna that is at the origin of orthogonal coordinates and faces the front in the x-axis direction, the Corning error can be expressed by the following calculation formula.
When the position of the target T is represented by the three-dimensional polar coordinates represented by the distance, the azimuth angle, and the zenith angle with the position of the antenna as the origin, equation (1) is obtained.
(R _T0 , φ _T0 , θ _T0 ) (1)
In this case, the elevation angle is 90 ° −θ _T0 . The relationship between the position of the target T and the Cartesian coordinates (x _T0 , y _T0 , z _T0 ) is
x _T0 = r _T0 · sin θ _T0 · cosφ _T0
y _T0 = r _T0 · sinθ _T0 · sinφ _T0
z _T0 = r _T0 · cos θ _T0
It becomes.
Here, when the target T is in the antenna front direction as a reference, the arrival direction φ _{a0 of the} radio wave is expressed by equation (2).
φ _a0 = 0 (2)
Further, in this case, the estimated azimuth φ _b0 based on the phase comparison is Equation (3) because there is no coning error because radio waves arrive from the front direction.
φ _b0 = 0 (3)

Next, regarding the arrival of radio waves when the target T is in the direction of the angle φ, since the antenna is virtually the same as when the antenna is rotated −φ degrees from the reference direction, the true direction φ _a1 is (4 ) Expression.
φ _a1 = φ (4)
The estimated direction φ _b1 by phase comparison when the radio wave of the target T arrives from the direction of φ degrees is virtually the same as the estimated direction by phase comparison when the antenna rotates −φ degrees from the reference direction. , (5).
φ _b1 = sin ⁻¹ {(sin θ · sin φ) / sin 90 °} (5)
Therefore, from the equations (4) and (5), the azimuth difference Δφ between the estimated azimuth and the true azimuth is expressed by the equation (6).
Δφ = φ _b1 −φ _a1
= Sin ⁻¹ {(sin θ · sin φ) / sin 90 °} −φ (6)
When the relationship between the azimuth difference caused by the coning error according to the equation (6) and the rotation angle of the antenna is expressed for each elevation angle, a curve as shown in FIG. 7 is obtained.

Using a phased array antenna equipped with a drive mechanism in advance, the antenna array surface is rotated from the reference direction, and the elevation angle is sequentially measured with a multi-antenna. The rotation angle from the reference direction (-φ) and the elevation angle (90 ° -θ) Is used to determine the azimuth difference Δφ from the equation (6), and the elevation angle (90 ° −θ) and the azimuth difference Δφ are associated with each other and stored in the true azimuth calculation database 8. At the time of actual measurement, the true azimuth calculation processing unit 9 uses the estimated elevation angle (90 ° −θ) by the multi-antenna 2 corresponding to the estimated azimuth φ _b1 measured by the phased array antenna 1 fixed in the reference direction, and the true azimuth calculation database. 8 is collated, the corresponding azimuth difference Δφ is extracted, and the true azimuth φ _a1 (= φ _b1 −Δφ) is calculated.
When the elevation angle data in the true azimuth calculation database 8 does not have a value that matches the actually estimated elevation angle, the azimuth difference corresponding to the estimated elevation angle is calculated from the azimuth difference corresponding to the previous and next elevation angles. That's fine. In this case, an approximate value of the true orientation is obtained, but the influence of the coning error can be improved.

  As described above, according to the first embodiment, the azimuth difference between the true azimuth and the estimated azimuth caused by the coning error of the phased array antenna measured in advance for each elevation angle is stored in the true azimuth calculation database. In addition, the target frequency, pulse width, pulse repetition frequency, pulse arrival time, and estimated direction are detected from the incoming radio waves received by the phased array antenna installed with the antenna array surface facing the reference direction. The target frequency, pulse width, pulse repetition frequency, pulse arrival time, and estimated elevation angle are detected from the radio wave, and correlation processing is performed on the target frequency, pulse width, pulse repetition frequency, and pulse arrival time using both antennas. The estimated elevation angle of the target is compared with the elevation angle of the true azimuth calculation database to extract the corresponding azimuth difference. Corrects the estimated orientation of the corresponding target on the basis of the extracted orientation difference is to calculate the true orientation of the relevant target. Therefore, the radio wave detection device at the time of actual measurement extracts the azimuth difference from the true azimuth calculation database using the elevation angle acquired by the multi-antenna, so that it is not necessary to provide the rotational drive mechanism for the phased array antenna, and electrical processing The azimuth accuracy can be increased by only Therefore, the problem caused by the conventional rotational drive mechanism is eliminated.

Embodiment 2. FIG.
FIG. 8 is a flowchart illustrating a processing procedure according to the second embodiment. In the figure, step ST41 is provided instead of step ST4 in FIG. That is, in the second embodiment, a method for obtaining a azimuth difference using an arithmetic expression will be described.
The true azimuth calculation processing unit 9 of the second embodiment is provided with a function for performing the processing of equation (6), that is, a processing program. In the true orientation calculation database 8, as described in the first embodiment, the phased array antenna is rotated in advance, the rotation angle of the antenna is measured for each elevation angle, and the obtained association data is stored. .

At the time of actual measurement, the estimated elevation angle by the multi-antenna 2 is used to collate with the elevation angle of the true azimuth calculation database 8 to extract the corresponding antenna rotation angle, and the estimated elevation angle and rotation angle are substituted into the equation (6) The difference is obtained and the true orientation is calculated (step ST41).
In some cases, the elevation angle data in the true azimuth calculation database 8 does not have a value that matches the actually estimated elevation angle. In that case, the rotation angle of the antenna corresponding to the estimated elevation angle is calculated by the ratio using the rotation angle of the antenna corresponding to the front and back elevation angles, and the estimated elevation angle and the calculated rotation angle of the antenna are substituted into equation (6). For example, an approximate value of the true orientation can be obtained. This can also improve the influence of the coning error.

  As described above, according to the second embodiment, the phased array antenna is rotated in advance, and the rotation angle of the antenna measured for each elevation angle is stored in the true azimuth calculation database. The target frequency, pulse width, pulse repetition frequency, pulse arrival time, and estimated direction are detected from the incoming radio waves received by the phased array antenna installed in the direction. At the same time, the target frequency and pulse are received from the incoming radio waves received by the multi-antenna. The width, pulse repetition frequency, pulse arrival time, and estimated elevation angle are detected, correlation processing is performed for the target frequency, pulse width, pulse repetition frequency, and pulse arrival time by both antennas, and the estimated elevation angle of the correlated target is true The angle of rotation of the corresponding antenna is extracted by comparing with the elevation angle of the database for calculation. Calculate the azimuth difference between the true direction and the estimated azimuth due to the coning error of the phased array antenna based on the angle and the rotation angle of the antenna, and correct the estimated azimuth of the target based on the calculated azimuth difference. The true azimuth of is calculated. Therefore, the radio wave detection device at the time of actual measurement extracts the rotation angle of the antenna from the true azimuth calculation database using the elevation angle acquired by the multi-antenna, and calculates the azimuth difference, so the same effect as in the first embodiment is obtained. It is done.

It is a block diagram which shows the function structure which shows the electromagnetic wave detection apparatus by Embodiment 1 of this invention. It is a flowchart which shows the process sequence of the radio wave detector which concerns on Embodiment 1 of this invention. It is explanatory drawing which shows the phase difference comparison method of a phased array antenna. It is explanatory drawing which shows the equiphase line which a phased array antenna has. It is explanatory drawing showing the coning error which a phased array antenna has. It is a schematic diagram which represents the relationship with the elevation angle by a coning error, a azimuth | direction difference, and a true azimuth | direction with a coordinate system. It is explanatory drawing which shows the curve which represented the relationship between the azimuth | direction difference which generate | occur | produces by a coning error, and the rotation angle of an antenna for every elevation angle. It is a flowchart which shows the process sequence of the radio wave detector which concerns on Embodiment 2 of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Phased array antenna, 2 Multi-antenna, 3, 4 Receiving part, 5, 6 Target specification detection part, 7 Correlation processing part, 8 True direction calculation database, 9 True direction calculation processing part, 10 Target management part.

Claims (2)

The incoming signal received by the phased array antenna with the antenna array surface facing the reference direction is separated for each target, and the frequency, pulse width, pulse repetition frequency, pulse arrival time, and estimated direction of each target are detected. A first target specification detecting unit,
A second target specification detection unit that separates received signals of incoming radio waves received by a multi-antenna for each target, and detects a frequency, a pulse width, a pulse repetition frequency, a pulse arrival time, and an estimated elevation angle of each target;
A correlation processing unit that performs correlation processing on the target frequency, pulse width, pulse repetition frequency, and pulse arrival time detected by the first and second target specification detection units;
A true azimuth calculation database for storing a azimuth difference between a true azimuth and an estimated azimuth caused by a coning error of a phased array antenna measured in advance for each elevation angle;
A corresponding azimuth difference is extracted by collating with the elevation angle of the true azimuth calculation database based on the estimated elevation angle of the target obtained by the correlation processing unit, and the correlated target is obtained based on the extracted azimuth difference. A radio wave detection apparatus comprising a true direction calculation processing unit that corrects the estimated direction and calculates a true direction of the target. The incoming signal received by the phased array antenna with the antenna array surface facing the reference direction is separated for each target, and the frequency, pulse width, pulse repetition frequency, pulse arrival time, and estimated direction of each target are detected. A first target specification detecting unit,
A second target specification detection unit that separates received signals of incoming radio waves received by a multi-antenna for each target, and detects a frequency, a pulse width, a pulse repetition frequency, a pulse arrival time, and an estimated elevation angle of each target;
A correlation processing unit that performs correlation processing on the target frequency, pulse width, pulse repetition frequency, and pulse arrival time detected by the first and second target specification detection units;
A database for true azimuth calculation that stores the rotation angle of the antenna measured for each elevation angle by rotating the phased array antenna in advance,
The elevation angle and the antenna rotation angle corresponding to the elevation angle are extracted by collating with the elevation angle of the true azimuth calculation database based on the estimated elevation angle of the target that has been correlated by the correlation processing unit, and the extracted antenna rotation angle Based on the azimuth difference between the true azimuth and the estimated azimuth due to the coning error of the phased array antenna, and correct the estimated azimuth of the correlated target based on the calculated azimuth difference to correct the target A radio wave detection apparatus comprising a true direction calculation processing unit for calculating a true direction.

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