JP4954112B2 - Array angle measuring device - Google Patents

Description

  The present invention relates to an array angle measuring device, and more particularly to an array angle measuring device for use in mobile communication, in-vehicle radar, and the like.

  In an apparatus that measures the incident angle of an incoming signal using a plurality of sensor elements, it is necessary to measure the reception channel characteristics of each sensor in advance or calibrate so that the reception channel characteristics of all sensors are the same. For this reason, it is necessary to observe or calibrate the reception channel characteristics of each sensor by observing the reception data corresponding to the incident angle. In the prior art, reception channel characteristics are measured and calibrated using received data of incoming signals whose incident angles are known.

  As a prior art for estimating an incident angle of an incoming signal using a plurality of sensors, there is a MUSIC (MUltiple SIgnal Classification) method or the like (for example, see Non-Patent Document 1). In such a prior art, when the number of incoming signals is one or when a plurality of incoming signals are uncorrelated, it is necessary to measure in advance the relationship between the reception channel characteristics of all the sensors and the incident angle. .

  On the other hand, when a plurality of incoming signals are completely correlated, it is necessary to calibrate so that the reception channel characteristics of all the sensors are the same (for example, see Non-Patent Document 2).

  In the conventional calibration method, received data corresponding to a preset incident angle is measured. In particular, in the incident angle estimation method using the relationship between the reception channel characteristics of all the sensors and the incident angle, it is assumed that the incident angle is known. In addition, there is an existing technique as a calibration method for estimating a parameter representing the reception channel characteristic of each sensor (for example, see Non-Patent Document 3). The parameter representing the reception channel characteristic of each sensor is synonymous with the calibration parameter. Also for such a calibration method, received data having a known incident angle is used.

  However, the receiving channel characteristic of the sensor varies with time due to, for example, the influence of the temperature characteristic of the amplifier. Therefore, the information on the reception channel characteristics included in the reception data measured in advance cannot be used for the calibration process of the reception channel characteristics that have changed over time. In such a case, it is desirable to update the reception data used for the calibration process, but it is often difficult to measure the reception data of an incoming signal with a known incident angle during sensor operation. In addition, adding equipment for setting an incoming signal with a known incident angle increases the cost of the apparatus.

  Therefore, it is conceivable that calibration processing is performed using received data of an incoming signal whose incident angle is unknown to cope with temporal changes in sensor reception channel characteristics. There is a conventional technique proposed as such a calibration method (for example, see Non-Patent Document 4). This prior art is a calibration method for estimating calibration parameters.

  FIG. 3 is a flowchart showing the flow of the calibration process shown in Non-Patent Document 4. 3, step S1 is an angle measurement process, step S2 is a calibration parameter estimation process for estimating a calibration parameter, step S3 is a calibration angle measurement process using the calibration parameter, and step S4 is a convergence determination of the calibration process. Convergence determination processing.

In the signal processing in FIG. 3, approximate angle measurement values (θ hat) ⁽⁰⁾ of a plurality of received data are obtained in the angle measurement processing in step S <b> 1. This angle measurement value (θ hat) ⁽⁰⁾ is assumed to be the incident angle, and the parameter (p hat) ⁽¹ ) representing the reception channel characteristics of each sensor using the incident angle in the calibration parameter estimation processing in step S2. ⁾ . Next, in the calibration angle measurement process of step S3, the angle measurement process calibrated with the estimated parameter (p hat) ⁽¹⁾ is performed, and the angle measurement value (θ hat) ⁽¹⁾ is estimated. In the convergence determination process in step S4, it is determined whether the estimated parameter (p hat) ⁽¹⁾ and the measured angle value (θ hat) ⁽¹⁾ have converged. If converged, the process ends. If not converged, the process returns to the calibration parameter estimation process in step S2, and the calibration parameter estimation process in step S2 and the calibration angle measurement process in step S3 are repeatedly calculated in the same manner as described above. , The parameter (p hat) ⁽ⁱ⁾ and the angle measurement value (θ hat) ⁽ⁱ⁾ are converged. In the i-th iterative calculation, the parameter (p hat) ⁽ⁱ⁾ is estimated using the measured angle value (θ hat) ⁽ⁱ⁻¹⁾ in the calibration parameter estimation process 2 in step S2, and the calibration in step S3. In the angle measurement process, the angle measurement value (θ hat) ⁽ⁱ⁾ is estimated by the angle measurement process calibrated by the parameter (p hat) ⁽ⁱ⁾ .

R. O. Schmidt, “Multiple emitter location and signal parameter estimation,” IEEE Trans., Vol. AP-34, no. 3, pp. 276-280, March 1986 T. Shan, M. Wax, T. Kailath, “On spatial smoothing for direction-of-arrival estimation of coherent signals,” IEEE Trans. Acoustics, Speech, and Signal Processing, vol. 33, no.4, pp. 806 -811, Aug 1985 B. Friedlander, A. J. Weiss, “Direction finding in the presence of mutual coupling,” IEEE Trans. Antennas and Propagation, vol.39, no. 3, pp. 273-284, March 1991 V. C. Soon, L. Tong, T.F. Huang, R. Liu, “A subspace method for controlling sensor gains and phases,” IEEE Trans. Signal Processing, vol. 42, no. 4, pp. 973-976, Apr 1994

However, when the error of the reception channel characteristic of each sensor includes a component that rotates the coordinate system, all angle measurement values include the same coordinate system rotation error. Therefore, in the conventional signal processing shown in FIG. 3 described above, since the same coordinate system rotation error occurs in the angle measurement value (θ hat) ⁽⁰⁾ in the angle measurement process in step S1, the parameter estimation for calibration in step S2 is performed. The coordinate system rotation error cannot be estimated by the processing. As described above, when the same error occurs in all the angle measurement values, the fact that the error factor cannot be calibrated is a drawback of the calibration process using the reception data whose incident angle is unknown.

  Thus, in the prior art, when the incident angle is unknown, there is a problem that the observation error for rotating the coordinate system cannot be calibrated.

  The present invention has been made in order to solve such problems, and when performing reception channel characteristic measurement and calibration using received data of an incoming signal whose incident angle is unknown, the physicality of the incoming signal is measured. It is an object of the present invention to obtain an array angle measuring device that makes it possible to perform calibration processing with high accuracy and low cost by estimating a coordinate system from characteristics.

  The present invention relates to an array angle measuring device used by being attached to a movable platform, and a plurality of sensor elements constituting an array antenna for receiving an incoming signal from a target which is a signal generation source, and the sensor Receiving means for outputting the incoming signal received by an element as received data; angle measuring processing means for estimating an incident angle of the target signal based on the received data generated by the receiving means; and the angle measuring process Based on the incident angle estimated by the means, movement direction estimation processing means for estimating the moving direction of the platform, and on the reception channel of the sensor element based on the incident angle estimated by the angle measurement processing means Calibration signal estimation processing means for estimating a characteristic difference, and the movement direction and the calibration signal estimated by the movement direction estimation processing means Using said reception channel characteristic difference estimated by the constant processing means, an array angle measuring device provided with an improved calibration angle measuring processing means for calibrating the incidence angle estimated by the angle measuring processing means.

  The present invention relates to an array angle measuring device used by being attached to a movable platform, and a plurality of sensor elements constituting an array antenna for receiving an incoming signal from a target which is a signal generation source, and the sensor Receiving means for outputting the incoming signal received by an element as received data; angle measuring processing means for estimating an incident angle of the target signal based on the received data generated by the receiving means; and the angle measuring process Based on the incident angle estimated by the means, movement direction estimation processing means for estimating the moving direction of the platform, and on the reception channel of the sensor element based on the incident angle estimated by the angle measurement processing means Calibration signal estimation processing means for estimating a characteristic difference, and the movement direction and the calibration signal estimated by the movement direction estimation processing means Since it is an array angle measuring device provided with an improved calibration angle measurement processing means for calibrating the incident angle estimated by the angle measurement processing means using the reception channel characteristic difference estimated by a constant processing means, When measuring and calibrating reception channel characteristics using received data of incoming signals with unknown incident angles, the calibration system is estimated with high accuracy and low cost by estimating the coordinate system from the physical characteristics of the incoming signals. Can be implemented.

Embodiment 1 FIG.
FIG. 1 is a configuration diagram showing the configuration of an array angle measuring device according to Embodiment 1 of the present invention. As shown in FIG. 1, the array angle measuring device according to the first embodiment is provided with a plurality of (L pieces) sensor elements 2-1 constituting an array antenna provided on a movable platform 1 that can be moved. 2-2,..., 2-L, a receiver 3, and a signal processing device 4. The receiver 3 applies the necessary processing such as amplification and A / D conversion to the incoming signal received by the sensor elements 2-1, 2-2,. Output. The signal processing device 4 indicates a difference in reception channel characteristics between the movement direction estimation processing unit 12 that estimates the movement direction of the mobile platform 1 and each of the sensor elements 2-1, 2-2, ..., 2-L. A calibration parameter estimation processing unit 13 that estimates calibration parameters, and an improved calibration angle measurement processing unit 14 that performs improved calibration angle measurement processing using the estimated moving direction and calibration parameters are provided. In the moving platform 1 targeted in the first embodiment, the moving direction can be used as the reference axis of the coordinate system in the angle measurement process as shown in FIG. In the signal processing device 7, the reference axis is determined by estimating the moving direction of the moving platform 1, and the coordinate system based on the conventional calibration process is made to coincide with the reference axis. For example, if the sensor elements 2-1, 2-2,..., 2-L are sensors that determine the moving direction of the moving platform 1 at an incident angle of 0 °, the estimated moving direction and 0 according to the conventional calibration process are used. Estimate the parameters to compensate for the angular difference that exists between the ° directions. In FIG. 1, 20 indicates a moving direction vector of the moving platform 1, and 30 indicates a signal generation source (target). Reference numeral 31 denotes a signal output from the signal generation source, and reference numeral 21 denotes an incident angle of the signal 31 with respect to the moving direction vector 20.

Next, the operation will be described.
Suppose that a calibration process using received data with a known incident angle in the case where a component that rotates the coordinate system is included in the error of the reception channel characteristic of each sensor element 2-1, 2-2, ..., 2-L. Is applied, the component that rotates the coordinate system can also be estimated in the calibration parameter estimation process. This is because a correct coordinate system can be defined in the estimation process by inputting the true value of the incident angle to the calibration parameter estimation process. From this, it is considered that the component that rotates the coordinate system can be estimated if an accurate coordinate system can be defined in the estimation process.

  Therefore, in the first embodiment, a calibration process using received data with an unknown incident angle is compensated by adding a function for estimating a coordinate system. That is, the difference between the calibration parameter by the calibration process using the reception data whose unknown incident angle is unknown and the estimation result by the function of estimating the coordinate system is newly estimated as the compensation parameter, and the new parameter is obtained by combining the calibration parameter and the compensation parameter. The correct calibration parameters. Then, angle measurement processing using new calibration parameters is performed.

  FIG. 2 is a flowchart showing a process flow of the array angle measuring device according to the first embodiment. In FIG. 2, step S11 is an angle measurement process similar to step S1 shown in FIG. 3, step S13 is a calibration parameter estimation process similar to step S2 shown in FIG. 3, and step S15 is shown in FIG. It is the same convergence determination process as shown step S4. Since these are as described above, they will be briefly described here. The difference between FIG. 2 and FIG. 3 is that the process of step S12 is added in FIG. 2, and the process of step S14 is performed instead of step S3 of FIG. Note that step S12 is a process for estimating the moving direction of the moving platform 1, and step S14 is an angle measurement process using calibration parameters and moving direction information.

In the signal processing of FIG. 2, first, a target signal is generated and output by the target signal generation source 30. The output target signal arrives as an incoming signal and is received by a plurality of sensor elements 2-1, 2-2,..., 2-L constituting the array antenna. At this time, in the angle measurement process of step S11, the receiver 3 generates reception data from the incoming signals received by the plurality of sensor elements 2-1, 2-2,. Using data, for example, H. Krim, M. Viberg, “Two decades of array signal processing research: the parametric approach” IEEE Signal Processing Magazine, vol. 13, no. 4, pp. 67-94, Jul 1996 ( Hereinafter, a rough angle measurement value (θ hat) ⁽⁰⁾ is obtained by arithmetic processing shown in Non-Patent Document 5. The angle measurement value (θ hat) ⁽⁰⁾ has the same observation error effect as the observation data not subjected to the calibration process shown in Non-Patent Document 3 or Non-Patent Document 4. Since the observation error includes a component that rotates the coordinate system, the angle measurement value (θ hat) ⁽⁰⁾ includes a certain angle error corresponding to the coordinate system rotation amount. Next, the movement direction estimation processing unit 12 of the signal processing device 4 assumes that the measured angle value (θ hat) ⁽⁰⁾ is the incident angle 21, and moves the movement platform 1 by the movement direction estimation process in step S12. The direction vector (ξ hat) ⁽¹⁾ is estimated. As a means for estimating the moving direction vector (ξ hat) ⁽¹⁾ , there are methods described in documents such as Japanese Patent Application Laid-Open No. 2007-3395 and Japanese Patent Application Laid-Open No. 2006-349568. Next, the calibration parameter estimation processing unit 13 of the signal processing device 4 uses the method shown in Non-Patent Document 4, for example, in the calibration parameter estimation processing in step S13, and the angle measurement value assumed to be the incident angle 21. (Θ hat) Based on ⁽⁰⁾ , a calibration parameter (p hat) ⁽¹⁾ representing a reception channel characteristic difference between the sensor elements 2-1, 2-2, ..., 2-L is estimated. Specific examples of the calibration parameter (p hat) ⁽¹⁾ include a matrix W in Non-Patent Document 3, a vector v in Non-Patent Document 4, and the like. Next, the improved calibration angle measurement processing unit 14 of the signal processing device 4 performs the estimated movement direction vector (ξ hat) ⁽¹⁾ and the calibration parameter (p hat) ^{(1) in} the improved calibration angle measurement process of step S14. Are used to perform an angle measurement process to calibrate the approximate angle measurement value (θ hat) ⁽⁰⁾ estimated in step S11 to obtain an angle measurement value (θ hat) ⁽¹⁾ . For example, calibration observation data obtained by dividing the observation data by the observation data theoretical value of the signal arriving from the movement direction indicated by the movement direction vector (ξ hat) ⁽¹⁾ is obtained. Further, the calibration observation data is calibrated with a calibration parameter (p hat) ⁽¹⁾ , and an angle measurement value (θ hat) ⁽¹⁾ is calculated by the calculation shown in Non-Patent Document 5. Next, the improved calibration angle measurement processing unit 14 of the signal processing device 4 performs the calibration parameter (p hat) ⁽¹⁾ estimated in step S13 and the angle measurement value estimated in step S14 ^{(1) in} the convergence determination process in step S15. θ hat) It is determined whether ⁽¹⁾ has converged. In the convergence determination process, the movement direction vector (ξ hat) ⁽ⁱ⁾ and the calibration parameter (p hat) ⁽ⁱ⁾ estimated in the i-th iteration calculation, and the movement direction vector (i-th iteration calculation) ⁽ⁱ⁾ When the difference between ⁽ ξ hat) ^(i-1) and calibration parameter (p hat) ^(i-1) is smaller than a predetermined threshold value, it is determined as a convergence state. If it has converged, the process ends. If it has not converged, the process returns to the calibration parameter estimation process in step S12. Thereafter, as with the signal processing of FIG.

  In the flowchart of FIG. 2, the order of the movement direction estimation process in step S12 and the calibration parameter estimation process in step S13 may be interchanged.

  In addition, the calibration parameter estimation process in step S13 in FIG. 2 is not limited to the process of estimating the calibration parameter described in Non-Patent Document 4 described above, and the calibration as described in Non-Patent Document 3 described above. It is also possible to employ a process for estimating the operational parameters.

Further, in the improved calibration angle measurement process of step S14 in FIG. 2, all the sensor elements 2-1 using the moving direction vector (ξ hat) ⁽¹⁾ and the calibration parameter (p hat) ⁽¹⁾ of the moving platform 1 are used. , 2-2,..., 2-L, the relationship between the reception channel characteristics and the incident angle can be reproduced, and angle measurement processing can be performed. Further, the moving direction vector (ξ hat) ⁽¹⁾ (and calibration parameter (p hat) ⁽¹⁾ ) of the mobile platform 1 is used to compensate for the error of the reception channel characteristic difference in the received data, and the angle measurement process is performed. It can be carried out. In particular, the method of calibrating the error of the reception channel characteristic from the reception data is employed for performing the angle measurement process by the above-described MUSIC method or the like when a plurality of incoming signals are completely correlated.

  In addition, as an example of the moving direction estimation process in step S12 in FIG. 2, it further has a function of estimating the relative velocity between the signal generation source 30 and the moving platform 1, and uses the estimated incident angle and relative velocity. The moving direction of the mobile platform 1 may be estimated. The relative velocity is expressed as a function of the incident angle. For example, when attention is paid to the relative speed between the moving platform 1 and a stationary object, the relative speed has a physical characteristic that maximizes in the moving direction of the moving platform 1. From this physical characteristic, the moving direction of the moving platform 1 can be estimated.

  Alternatively, as another example of the movement direction estimation process in step S12 in FIG. 2, the apparatus further has a function of estimating a relative distance between the signal generation source 30 and the movement platform 1, and calculates the estimated incident angle and relative distance. It may be used to estimate the moving direction of the moving platform 1. The relative position between the signal generation source 30 and the mobile platform 1 is estimated from the incident angle and the relative distance, and the movement direction of the mobile platform 1 is estimated by tracking the relative position over a plurality of observation data having different observation times. To do. For example, when attention is paid to the relative position between the moving platform 1 traveling straight and a stationary object, the locus of the relative position draws a straight line due to the change in the observation time. Since this straight line is parallel to the moving direction of the moving platform 1, the moving direction of the moving platform 1 can be estimated.

  As described above, in the first embodiment, the moving direction of the moving platform 1 is estimated, and in the calibration process, a process for compensating the coordinate system using the estimated moving direction of the moving platform 1 as a reference axis is added. Therefore, the reception channel characteristic difference between the sensor elements can be calibrated only with the reception data of the incoming signal whose incident angle is unknown. In addition, the configuration for performing the calibration can be realized at a low cost because a signal source having a known incident angle is not provided outside the apparatus.

It is a block diagram which shows the structure of the array angle measuring apparatus which concerns on Embodiment 1 of this invention. It is a flowchart which shows the flow of a process of the array angle measuring device which concerns on Embodiment 1 of this invention. It is a flowchart which shows the flow of the conventional signal processing.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Mobile platform, 2-1, 2-2, 2-3 Sensor element, 3 Receiver, 4 Signal processing apparatus, 12 Movement direction estimation process part, 13 Calibration parameter estimation process part, 14 Improved calibration angle measurement process part, S1, S11 Angle measurement processing, S2, S13 Calibration parameter estimation processing, S3 Calibration angle measurement processing, S4, S15 Convergence determination processing, S14 Improved calibration angle measurement processing.

Claims (4)

An array angle measuring device used by being attached to a movable platform,
A plurality of sensor elements constituting an array antenna for receiving an incoming signal from a target which is a signal generation source;
Receiving means for outputting the incoming signal received by the sensor element as received data;
Angle measurement processing means for estimating an incident angle of the target signal based on the received data output by the receiving means;
Based on the incident angle estimated by the angle measurement processing means, a movement direction estimation processing means for estimating the movement direction of the platform;
Calibration signal estimation processing means for estimating a reception channel characteristic difference of the sensor element based on the incident angle estimated by the angle measurement processing means;
Improvement of calibrating the incident angle estimated by the angle measurement processing means using the movement direction estimated by the movement direction estimation processing means and the reception channel characteristic difference estimated by the calibration signal estimation processing means. An array angle measuring device comprising calibration angle measuring processing means. The calibration signal estimation processing means further includes:
The array angle measuring device according to claim 1, wherein an error of the estimated difference in the reception channel characteristic is compensated using the movement direction estimated by the movement direction estimation unit. The moving direction estimating means includes
A function of estimating a relative speed between the target and the platform;
The array angle measuring device according to claim 1 or 2, wherein a moving direction of the platform is estimated based on the incident angle and the relative velocity estimated by the angle measuring processing means. The moving direction estimating means includes
A function of estimating a relative distance between the target and the platform;
The array angle measuring device according to claim 1, wherein a moving direction of the platform is estimated based on the incident angle and the relative distance estimated by the angle measuring processing unit.

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