JP2009139183A - Angle measuring apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an angle measuring apparatus for measuring the angle of a target accurately even when turbulence of phase by radome exists. <P>SOLUTION: This angle measuring apparatus comprises a plurality of antenna elements 21, 22 and 23 arranged so that the directions of linear polarization are different, a polarization specifying section 5 for specifying polarization and calculating the polarization angle based on the level of a signal received by the plurality of antenna elements, a phase correction table 6 storing a correction value for correcting the phase for each polarization angle, and an angle measuring section 4 for acquiring the correction value according to the polarization angle from the polarization specifying section from the phase correction table, correcting the phase of the signal received by the plurality of antenna elements using the acquired correction value, and measuring the angle of the target direction using an angle measuring curve depending on the phase difference of the signal after the correction. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an angle measuring device for measuring an angle of a target with a radio wave interferometer, and more particularly to a technique for preventing deterioration in angle measuring accuracy due to polarization.

  A conventional radio interferometer equipped with a radome has a problem that the phase of a signal obtained from each antenna element is disturbed due to the influence of the radome and the measurement accuracy is deteriorated. In order to solve this problem, a technique is known in which angle characteristics are tabulated in advance and signals from antenna elements are corrected using this table.

  FIG. 12 is a block diagram showing a configuration of an angle measuring device for measuring a target with a radio wave interferometer employing a conventional interferometer method (see Non-Patent Document 1) using such a technique. This angle measuring device includes a radome 1, antenna elements 21, 22 and 23, receivers 31, 32 and 33, an angle measuring unit 4 and a phase correction table 7.

  The antenna elements 21, 22 and 23 receive radio waves, convert them into electric signals, and send them to the receivers 31, 32 and 33, respectively. These antenna elements 21, 22 and 23 are covered by the radome 1.

  The receivers 31, 32, and 33 perform predetermined processing on the signals sent from the antenna elements 21, 22, and 23, respectively, and send them to the angle measuring unit 4. The angle measuring unit 4 corrects the phase of the signals transmitted from the receivers 31, 32, and 33 using the correction value acquired from the phase correction table 7, and performs angle measurement based on the corrected signal.

  The phase correction table 7 stores information representing angle characteristics. Specifically, as shown in FIG. 13, the arrival angle Φl (l = 1, 2,...) For each of the frequencies fm (m = 1, 2,..., M; M is a positive integer). , L; L is a positive integer), and a correction value cml is measured and stored in advance. The contents of the phase correction table 7 are referred to by the angle measuring unit 4 as described above.

  The operation of the conventional angle measuring device configured as described above will be described. FIG. 14 is a flowchart showing angle measurement processing in the angle measuring apparatus. In the angle measurement process, first, a correction table is extracted (step S51). That is, the angle measuring unit 4 selects a correction value according to the frequency and direction of arrival of the radio wave received from the phase correction table 7.

  Next, rough measurement is performed (step S52). That is, the angle measuring unit 4 performs coarse angle measurement after correcting the signals sent from the receivers 31, 32, and 33 using the correction value selected in step S51. In this case, an angle measurement value with low accuracy but no angular ambiguity is obtained.

Next, precise angle measurement is performed (step S53). That is, the angle measurement unit 4 calculates a precise angle measurement value using the value obtained by performing the rough angle measurement process in step S52. In this case, angular ambiguity occurs. Therefore, the angle measuring unit 4 sets a predetermined range as the target range from the angle measurement value obtained in step S52, specifies the angle existing in the target range as the angle measurement value, and outputs the angle measurement information to the outside. .
Yoshida, “Revised Radar Technology”, IEICE, pp.285-286 (1996)

  In the conventional angle measuring device described above, a phase correction table configured to have a constant angle characteristic is used regardless of polarization. However, since the angle characteristics change according to the polarization, when the polarization is unknown, an appropriate correction value cannot be obtained, and a correction error occurs. There is also a problem that the phase disturbance becomes large and ambiguity occurs in the angle measurement curve.

  The present invention has been made to solve the above-described problems, and its object is to provide an angle measuring device capable of measuring a target with higher accuracy even when there is a phase disturbance due to a radome. is there.

  In order to solve the above problem, the first invention specifies a plurality of antenna elements arranged so that the directions of linearly polarized waves are different from each other, and specifies the polarization based on the levels of signals received by the plurality of antenna elements. The polarization specifying unit that calculates the polarization angle using the phase, the phase correction table that stores the correction value for correcting the phase for each polarization angle, and the correction value according to the polarization angle from the polarization specifying unit are phased. Angle measurement that acquires from the correction table, corrects the phase of the signal received by multiple antenna elements using the acquired correction value, and measures the target direction using the angle measurement curve based on the phase difference of the corrected signal It has the part.

  Further, the second invention provides a plurality of antenna elements, a angle measuring unit that measures a target direction using a angle measuring curve based on a phase difference of signals received by the plurality of antenna elements, and a angle measuring unit in the angle measuring unit. When the angle measurement curve used in the above shows that it has angle ambiguity, it is monotonic from among the angle measurement curves due to the phase difference of the signals received by the multiple antenna element pairs of the multiple antenna elements. A new angle measurement curve is formed by selecting a changing portion, and an angle measurement correction processing unit for correcting an angle measurement result in the angle measurement unit using the formed angle measurement curve is provided.

  The third invention provides a plurality of antennas in a plurality of antenna elements when the angle measurement curve used for angle measurement in the angle measurement unit indicates that the angle measurement has an angle ambiguity in the first invention. A new angle measurement curve is formed by selecting a monotonically changing portion from a plurality of angle measurement curves due to the phase difference of the signals received by the element pair, and the angle measurement unit uses the formed angle measurement curve. An angle measurement correction processing unit for correcting the angle measurement result is provided.

  According to the present invention, even when there is a disturbance in the phase of the signal from the antenna element due to the radome, the target angle can be measured with higher accuracy.

  Specifically, according to the first invention, the polarization angle is calculated by specifying the polarization based on the levels of the signals received by the plurality of antenna elements, and the correction value corresponding to the polarization angle is set as the phase. Since the phase of the signal obtained from the correction table and received by multiple antenna elements is corrected and the target direction is measured using the angle measurement curve based on the phase difference of the corrected signal, an appropriate value according to the polarization is obtained. A correction value can be used, and the target direction can be measured with high accuracy.

  Further, according to the second aspect of the invention, the angle measurement value is corrected by selecting a monotonically changing portion of the angle measurement curve that is less affected by the angle ambiguity among the plurality of angle measurement curves. The angle ambiguity generated by the disturbance can be reduced, and the target direction can be measured with high accuracy.

  Further, according to the third invention, an effect obtained by combining the effects of the first invention and the effect of the second invention can be obtained.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram illustrating the configuration of the angle measuring device according to the first embodiment of the present invention. This angle measuring device is configured by adding a polarization specifying unit 5 to the angle measuring device shown in FIG. 11 and changing the phase correction table 7 to another phase correction table 6. Hereinafter, a description will be given focusing on differences from the conventional angle measuring device.

  FIG. 2 shows the arrangement of the antenna elements 21, 22 and 23. In order to specify the polarization, as shown in FIG. 3, antenna elements 21, 22 and 23 arranged so that the directions of polarization are different are used.

  In the example shown in FIG. 3, when the vertical direction is 0 degree, the polarization direction of the antenna element 21 is 0 degree, the polarization direction of the antenna element 22 is 60 degrees, and the polarization direction of the antenna element 23 is It is set to 120 degrees. FIG. 3 shows a case where three antenna elements are used. In general, when N elements (N is a positive integer) are used, the direction of polarization is divided into 180 degrees by N. It can be an angle.

The polarization specifying unit 5 specifies the polarization and calculates the polarization angle. FIG. 4 is a diagram for explaining the principle of specifying the polarization. The identification of the polarization is performed using the level of the signal output from the antenna elements 21, 22 and 23 whose polarization direction is changed (hereinafter referred to as "reception level"). In the case of linear polarization, the polarization angle is calculated by the following centroid calculation.

here,
θn: angle of polarization of the nth antenna element
0, 180 / N, 180 / N × 2,... 180 / N × (N−1)
An: reception level of n-th antenna element N: number of antenna elements (n = 1 to N)
In the case of FIG. 4A, since only the reception level An of the antenna element 21 is high, it is determined that the polarization is linearly polarized, and the polarization angle is calculated as 0 degree by the centroid calculation of the equation (1). In the case of FIG. 4B, since only the reception level An of the antenna element 22 is high, it is determined as a linearly polarized wave, and the polarization angle is calculated to be 60 degrees by the centroid calculation of the equation (1). In the case of FIG. 4C, since the reception level An of the antenna element 22 and the antenna element 23 is high, it is determined as linear polarization, and the polarization angle is calculated as 90 degrees by the centroid calculation of equation (1). .

  As shown in FIG. 4D, if the reception levels An are almost the same level, it is determined as circularly polarized waves. The polarization angle calculated by the polarization specifying unit 5 is sent to the phase correction table 6.

  The phase correction table 6 stores information representing angle characteristics. Specifically, as shown in FIG. 5, for each polarization angle Θn (n = 1, 2,..., N; N is a positive integer), the frequency fm (m = 1, 2,... , M; M is a positive integer), a correction value cnml for the arrival angle Φl (l = 1, 2,..., L; L is a positive integer) is measured and stored in advance. The contents of the phase correction table 6 are referred to by the angle measuring unit 4.

  Next, the operation of the angle measuring device according to the first embodiment of the present invention configured as described above will be described. FIG. 6 is a flowchart showing the angle measurement process performed by the angle measuring device including N receivers. Here, it is assumed that N = 3.

  In this angle measurement process, first, the antenna element reception level is acquired (step S11). That is, the receivers 31, 32, and 33 perform predetermined processing on the signals transmitted from the antenna elements 21, 22, and 23, respectively, and then send the received signals to the angle measurement unit 4 and the polarization specifying unit 5.

  Next, polarization specifying processing is performed (step S12). That is, the polarization specifying unit 5 specifies the polarization based on the reception level of the received signals sent from the receivers 31, 32 and 33, calculates the polarization angle, and sends it to the phase correction table 6.

  Next, correction table extraction corresponding to the polarization is performed (step S13). That is, the angle measuring unit 4 extracts a correction value corresponding to the polarization angle, frequency, and arrival direction of the received radio wave from the phase correction table 6.

  Next, rough measurement is performed (step S14). In the case of the arrangement of antenna elements shown in FIG. 2, the angle measuring unit 4 extracts received signals obtained from a pair of antenna elements having a small interval (hereinafter referred to as “pair elements”) via the receiver in step S13. Each of the correction values is corrected, and a rough angle measurement is performed using an angle measurement curve based on a phase difference between the pair of received signals after correction, thereby calculating a rough angle. In this case, as shown in FIG. 7B, an angle measurement value with low accuracy but no angular ambiguity is obtained.

  Next, a precise angle is performed (step S15). That is, the angle measuring unit 4 corrects the received signals obtained from the pair elements having a large interval via the receiver with the correction values extracted in step S13, and measures the phase difference between the corrected pair of received signals. A precise angle is calculated using an angular curve, and a highly accurate angle is calculated. In this case, as shown in FIG. 7A, angular ambiguity occurs. Therefore, the angle measuring unit 4 sets a predetermined range as a target range from the angle measurement value obtained in step S14, and specifies an angle existing in the target range as the angle measurement value. The specified angle measurement value is output to the outside as angle measurement information.

In the angle measurement process in steps S14 and S15, if the phase correction is not performed on each of the AZ plane and the EL plane, that is, the angle measurement is performed while ignoring the polarization, the target angle is calculated by the following equation. it can.

here,
λ; wavelength di; position dj from antenna element i from phase center; position from antenna element j from phase center; Φ; target angle Δψij; phase difference between paired elements. When performing angle measurement in consideration, the target angle is calculated by the following equation using Δψij and the correction value of the phase correction table 6.

here,
Cnml: Correction value Polarization angle θ: n = 1 to N
Frequency f; m = 1 to M
Arrival angle Φ; l = 1 to L
In addition, although the flowchart shown in FIG. 6 shows the angle measurement processing of the angle measuring device provided with N receivers, even if the angle measuring device includes less than N receivers, Angle measurement processing is possible. FIG. 8 is a flowchart showing angle measurement processing performed by such an angle measuring device. Here, it is assumed that N = 2 and the receiver 33 does not exist.

  In this angle measurement process, first, the antenna element reception level is acquired (step S21). That is, the receivers 31 and 32 perform predetermined processing on the signals transmitted from the antenna elements 21, 22, and 23, respectively, and then send the received signals to the angle measurement unit 4 and the polarization specifying unit 5.

  Next, it is checked whether or not acquisition of reception signals from all antenna elements has been completed (step S22). If it is determined in step S22 that acquisition of reception signals from all antenna elements has not been completed, the antenna elements are changed (step S23). For example, the antenna element connected to the receiver 32 is switched from the antenna element 22 to the antenna element 23. Then, it returns to step S21 and the process mentioned above is repeated.

  On the other hand, if it is determined in step S22 that acquisition of received signals from all antenna elements has been completed, the process proceeds to step S12. The processing after step S12 is the same as the angle measurement processing performed by the angle measuring device including the N receivers described above.

  As described above, according to the angle measuring apparatus according to the first embodiment of the present invention, the polarization angle is calculated by specifying the polarization based on the levels of the signals received by the plurality of antenna elements 21, 22 and 23. Then, a correction value corresponding to the polarization angle is acquired from the phase correction table 6 to correct the phase of the signals received by the plurality of antenna elements 21, 22 and 23, and the angle measurement curve based on the phase difference of the corrected signals. Since the target direction is measured using, an appropriate correction value corresponding to the polarization can be used, and the target direction can be measured with high accuracy.

  The angle measuring device according to the second embodiment of the present invention is configured to reduce the angular ambiguity generated by the phase disturbance caused by the radome.

  FIG. 9 is a block diagram illustrating a configuration of the angle measuring device according to the second embodiment of the present invention. This angle measuring device is configured by adding an angle measuring correction processing unit 8 to the angle measuring device according to the first embodiment shown in FIG.

  The angle measurement correction processing unit 8 indicates that the angle measurement curve used for angle measurement in the angle measurement unit 4 indicates that the angle measurement ambiguity has an angle ambiguity, and a plurality of pair elements in the antenna elements 21, 22, and 23 A new angle measurement curve is formed by selecting the part that changes monotonously (monotonically increasing or decreasing) from multiple angle measuring curves due to the phase difference of the signals received by the (antenna element pair). The angle measurement result in the angle measuring unit 4 is corrected using the angle measurement curve.

  When selecting a monotonically changing portion of the angle measurement curve, if there are a plurality of monotonically changing portions, it is preferable to select the one having a larger slope.

  Now, consider an angle measuring device having three antenna elements A, B and C as shown in FIG. In this case, with respect to the AZ plane, two types of antenna elements A and C and antenna elements B and C can be selected as the pair elements that are separated from each other for use in the precise measurement angle. Since the same applies to the EL plane, only the AZ plane will be described below.

  When angle measurement curves are drawn in advance for each pair element, depending on the phase disturbance, the phase difference of the pair element changes monotonously with respect to the angle, as shown in FIGS. 10 (b) and 10 (c). As a result, there may be an angular ambiguity.

  As a countermeasure, an angle measurement curve having a small angle ambiguity is selected according to the angle range by utilizing the fact that the angle range having the angle ambiguity varies depending on the paired elements. In the pair of antenna elements A and C shown in FIG. 10B, a part T1 of the angle measurement curve is selected as an angle range in which the angle can be measured, and in the pair of antenna elements B and C shown in FIG. A part T2 of the angle measurement curve is selected as an angle range in which the angle can be measured.

  Then, a part of the selected angle measurement curves T1 and T2 are combined as shown in FIG. 10D and used for angle measurement. As a result, the angle can be measured by the angle measurement curve with reduced angle ambiguity.

  In addition, if the angle measurement curve in the angle range in which the angle can be measured cannot be selected, the position can be selected by changing the position of the antenna element forming the pair.

  Next, the operation of the angle measuring device according to the second embodiment will be described. FIG. 11 is a flowchart showing an angle measurement process performed by an angle measuring device including N receivers. Here, it is assumed that N = 3.

  In the following description, steps that perform the same process as the angle measurement process in the angle measuring apparatus according to the first embodiment shown in FIG. Simplify.

  In this angle measurement process, first, the antenna element reception level is acquired (step S11). Next, polarization specifying processing is performed (step S12). Next, correction table extraction corresponding to the polarization is performed (step S13).

  Next, angle measurement is performed (step S31). That is, the angle measuring unit 4 executes the same processing as the processing of step S14 and step S15 in the angle measuring processing performed by the angle measuring device according to the first embodiment.

  Next, it is checked whether or not the angle measurement for all the pair elements has been completed (step S32). For example, it is checked whether or not two kinds of angle measurement such as a pair of antenna elements A and C and a pair of antenna elements B and C are completed. If it is determined in step S32 that the angle measurement for all the pair elements has not been completed, pair change is performed (step S33). For example, when the angle measurement of the pair of antenna elements A and C is completed and the angle measurement of the pair of antenna elements B and C is not completed, the angle measurement of the pair of antenna elements B and C is performed. The setting is changed. Then, it returns to step S31.

  On the other hand, if it is determined in step S32 that the angle measurement for all the paired elements has been completed, angle measurement value selection is performed (step S34). That is, the angle measurement correction processing unit 8 selects a monotonically changing portion from a plurality of angle measurement curves to form a new angle measurement curve, and the angle measurement unit 4 uses the formed angle measurement curve. Correct the corner results.

  As described above, according to the angle measuring apparatus according to the second embodiment of the present invention, measurement is performed by selecting a monotonically changing portion of the angle measurement curve that is less affected by the angle ambiguity among the plurality of angle measurement curves. Since the angle value is corrected, it is possible to reduce the angle ambiguity caused by the phase disturbance caused by the radome and to measure the target direction with high accuracy.

  Note that the angle measuring device according to the second embodiment described above is configured by adding the angle measurement correction processing unit 8 to the angle measuring device according to the first embodiment, but the polarization specifying unit is different from the conventional angle measuring device. An angle measuring correction processing unit 8 may be added to the angle measuring device that is not provided. In this case, steps S11 to S13 shown in the flowchart of FIG. 11 can be omitted. Also in this configuration, similarly to the angle measuring device according to the second embodiment, it is possible to reduce the angle ambiguity generated by the phase disturbance caused by the radome.

  Further, in the angle measuring device according to the second embodiment, the case where the three antenna elements are provided has been described, but the case where four or more antenna elements are provided may be used. Conversely, if no angular ambiguity occurs, two antenna elements may be provided.

  Furthermore, in the angle measuring device according to the second embodiment, the angle measurement is performed by combining the coarse angle and the precise angle, but the angle measurement may not be a combination of the coarse angle and the precise angle.

  The present invention can be applied to a radio wave interferometer, a radar apparatus, and the like provided with a radome.

It is a block diagram which shows the structure of the angle measuring device which concerns on Example 1 of this invention. It is a figure which shows arrangement | positioning of the antenna element used with the angle measuring device which concerns on Example 1 of this invention. It is a figure which shows the polarization of the antenna element used with the angle measuring device which concerns on Example 1 of this invention. It is a figure for demonstrating the principle which specifies the polarization performed by the polarization specific part of the angle measuring device which concerns on Example 1 of this invention. It is a figure which shows the structure of the phase correction table used with the angle measuring device which concerns on Example 1 of this invention. It is a flowchart which shows the angle measurement process performed when the angle measuring device which concerns on Example 1 of this invention is equipped with N receivers. It is a figure for demonstrating calculation of the angle measurement value in the case of performing the rough measurement angle and the precise measurement angle in the angle measuring device which concerns on Example 1 of this invention. It is a flowchart which shows the angle measurement process performed when the angle measuring apparatus which concerns on Example 1 of this invention is provided with the number of receivers which is less than N pieces. It is a block diagram which shows the structure of the angle measuring device which concerns on Example 2 of this invention. It is a figure for demonstrating selection of the angle measurement curve in the angle measuring apparatus which concerns on Example 2 of this invention. It is a flowchart which shows the angle measurement process performed when the N angle receiver is provided in the angle measuring apparatus which concerns on Example 2 of this invention. It is a block diagram which shows the structure of the conventional angle measuring apparatus. It is a figure which shows the structure of the phase correction table used with the conventional angle measuring device. It is a flowchart which shows the angle measurement process performed in the conventional angle measuring apparatus.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Radome 21-23 Antenna element 31-33 Receiver 4 Angle measurement part 5 Polarization specific | specification part 6, 7 Phase correction table 8 Angle measurement correction process part

Claims (3)

A plurality of antenna elements arranged so that the directions of linearly polarized waves are different;
A polarization specifying unit that calculates a polarization angle by specifying a polarization based on a level of a signal received by the plurality of antenna elements;
A phase correction table storing a correction value for correcting the phase for each polarization angle;
A correction value corresponding to the polarization angle from the polarization specifying unit is acquired from the phase correction table, and the phase of the signal received by the plurality of antenna elements is corrected using the acquired correction value, and the corrected An angle measurement unit that measures the target direction using an angle measurement curve based on the phase difference of the signal,
An angle measuring device comprising: A plurality of antenna elements;
An angle measuring unit for measuring an angle of a target direction using an angle measurement curve based on a phase difference of signals received by the plurality of antenna elements;
When the angle measurement curve used for angle measurement in the angle measurement unit indicates that the angle measurement ambiguity has an angle ambiguity, a plurality of signals are obtained due to phase differences of signals received by a plurality of antenna element pairs in the plurality of antenna elements. A new angle measurement curve by selecting a monotonically changing portion from the angle measurement curve, and an angle measurement correction processing unit that corrects the angle measurement result in the angle measurement unit using the formed angle measurement curve; and ,
An angle measuring device comprising:   When the angle measurement curve used for angle measurement in the angle measurement unit indicates that the angle measurement ambiguity has an angle ambiguity, a plurality of signals are obtained due to phase differences of signals received by a plurality of antenna element pairs in the plurality of antenna elements. A new angle measurement curve is formed by selecting a monotonically changing portion from among the angle measurement curves, and an angle measurement correction processing unit that corrects the angle measurement result in the angle measurement unit using the formed angle measurement curve is provided. The angle measuring device according to claim 1, further comprising:

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