JP4902985B2 - Monopulse radar apparatus calibration method and calibration determination apparatus - Google Patents

Description

  The present invention relates to a calibration method for a monopulse radar apparatus and a calibration determination apparatus therefor, and in particular, confirms that a correction value obtained for azimuth (phase difference) correction is not obtained in a multi-target state. The present invention relates to a calibration method and a calibration determination device that can be used.

  As a method for determining the azimuth of the target, a phase monopulse method is known in which the azimuth of the target is calculated from the phase difference between reflected waves received by two antennas.

  FIG. 1 is a diagram for explaining a phase monopulse system. As shown in FIG. 1, a phase monopulse radar device receives reflected waves from an object with two receiving antenna waves, and determines the azimuth angle θ of the object from the reception phase difference φ between them using, for example, the following equation: To do.

θ = sin ⁻¹ (λφ / 2πd ₀ ) (1)
Where λ is the wavelength of the radar wave and d ₀ is the antenna interval.

  Using a transmission wave that is FM-modulated with a triangular wave, the beat signal generated by mixing a part of the transmission wave with the reception wave is relative to the distance to the object from the sum and difference of the frequencies in the upstream and downstream sections of the triangular wave. FM-CW radar that obtains speed is used as an on-vehicle radar. In this FM-CW radar, the aforementioned reception phase difference φ is calculated from the phase value of the peak appearing in the Fourier transform result of the beat signal.

  FIG. 2 is a block diagram showing a configuration of a phase monopulse FM-CW radar apparatus. In FIG. 2, three antennas AT0, AT1, and AT2 are arranged. For example, when the wavelength of a carrier wave is λ, the intervals between AT0 and AT1 and the intervals between AT1 and AT2 are arranged to be λ.

  A transmission signal that is FM-modulated with a triangular wave output from a voltage controlled oscillator (VCO) 10 is amplified by a transmission amplifier 14 and transmitted from an antenna via a circulator 16. In the radar apparatus shown in FIG. 2, transmission / reception uses one of the three antennas AT0, AT1, and AT2 selected by the switches SW0, SW1, and SW2. A reception signal transmitted by the antenna selected by the switches SW0, SW1, and SW2 and received by the antenna selected by the switches SW0, SW1, and SW2 is amplified by the reception amplifier 26 through the circulator 16, and is transmitted to the mixer 28 by the transmission wave. Mixed with a part, a beat signal is generated. The beat signal generated by the mixer 28 is converted into a digital signal by the A / D converter 32, subjected to fast Fourier transform (FFT) by the fast Fourier transform unit 34 and input to the CPU 36. Based on the frequency analysis of the beat signal, the CPU 36 calculates the orientation with the target, as well as the distance and relative speed.

  When obtaining the reception phase difference φ, two of the three antennas AT0, AT1, and AT2 are selected, and for each peak obtained from the received signal (reflected wave) of each selected antenna, the corresponding peak A phase difference value (phase difference φ) is obtained. For example, a combination of the antenna AT0 and the antenna AT1, a combination of the antenna AT0 and the antenna AT2, and a combination of the antenna AT1 and the antenna AT2 can be taken.

  As described above, in the phase monopulse method, the azimuth of the target is obtained based on the reception phase difference φ between the antennas. However, the phase difference also occurs due to the path difference of the reception signal in the radar apparatus. That is, if the distance of the signal path from each antenna to the signal processing circuit is different, the direction is obtained from the phase difference obtained by adding the phase difference due to the signal path difference to the reception phase difference φ between the antennas, and the target It is impossible to find the correct orientation of The signal path difference is represented by Δx in FIG. 2, for example, and the path to the circulator 16 of the received signals at the antennas AT0 and AT2 is longer by Δx than the path (length x) of the antenna AT1. Δx in FIG. 2 is a schematic and exemplary signal path difference. Actually, various signal path differences unique to each radar apparatus are generated according to the circuit design of the radar apparatus and individual differences.

  Since the phase difference corresponding to the signal path difference is detected with a deviation in the azimuth, conventionally, the phase difference corresponding to the signal path difference is obtained in advance as a correction value, and when obtaining the azimuth, the azimuth is determined using the correction value. The correct orientation is obtained by performing calibration to correct. Specifically, in the inspection process before the factory shipment stage of the radar device, the measurement is performed by measuring the azimuth with respect to the target arranged in a known azimuth (preferably, azimuth 0 degree) for each radar device by the phase monopulse method. A correction value for the azimuth (phase difference) is obtained and stored in the radar apparatus so that the obtained azimuth becomes a predetermined azimuth (for example, 0 degree).

  In the normal operation stage after factory shipment, the direction of the target can be correctly detected by the phase monopulse method by calculating using the correction value obtained by this calibration.

  As described above, in the inspection process before the factory shipment stage, the calibration is performed by obtaining the correction value of the phase difference by measuring the azimuth of the reference target whose azimuth is known, but the target is in a multi-target state. If this is the case, the target is detected in an azimuth (phase difference) different from the known azimuth and a correction value for the azimuth is obtained, so that a correct correction value cannot be obtained.

  In the multi-target state, when multiple peaks due to reflection from multiple targets are close enough that they cannot be separated on the frequency axis, the phase of the reflected wave from multiple targets is observed as the phase difference φ. In other words, it means a state in which an incorrect orientation different from any of the correct orientations of each target is measured and the correct orientation cannot be determined. If calibration is performed in the state where another target is placed in the immediate vicinity of the reference target, the above-described multi-target state occurs, and there is a problem that the azimuth is corrected with an incorrect correction value.

  Accordingly, an object of the present invention is to determine whether or not the obtained correction value is obtained in a multi-target state in a calibration process for correcting the azimuth of a monopulse radar device, and a normal state that is not a multi-target state. It is an object of the present invention to provide a calibration method capable of obtaining a correction value with a calibration determination apparatus for the calibration method.

In order to achieve the above object, the calibration method of the present invention has three or more antennas, and a monopulse method based on the reflected wave received by a combination of two of the three or more antennas. In the radar apparatus calibration method for measuring the azimuth of the target according to the above, based on the reflected wave, the azimuth of the reference target arranged in a known azimuth is measured using the monopulse method, and measured using the monopulse method. Perform calibration to correct the azimuth to the azimuth of the reference target, and based on the reflected wave, measure the azimuth of the reference target using a higher resolution method (for example, digital beam forming method) than the monopulse method, only if it can not detect a plurality of orientations during the measurement, the calibration And judging a tio ting effective.

In order to achieve the above object, a calibration determination apparatus of the present invention has three or more antennas, and a monopulse based on a reflected wave received by a combination of two of the three or more antennas. In a radar apparatus calibration determination apparatus that measures the azimuth of a target using a method, the radar apparatus measures and measures the azimuth of a reference target placed in a known azimuth using a monopulse method based on the reflected wave. When the calibration for correcting the azimuth direction to the azimuth of the reference target is executed, an acquisition means for acquiring an information signal relating to the reflected wave, and a higher resolution method (for example, digital) based on the information signal beamforming) was used to measure the orientation of the reference target, to the measurement Ri Failure to detect a plurality of orientation only, characterized in that it comprises an effective and determination means for determining the calibration.

The radar apparatus of the present invention has three or more antennas, and measures the azimuth of the target by the monopulse method based on the reflected waves received by the combination of two of the three or more antennas. In the radar apparatus, the measuring means for measuring the azimuth of the reference target arranged in a known azimuth using the monopulse method based on the reflected wave, and the azimuth measured by the measuring means as the azimuth of the reference target Based on the reflected wave and a calibration means for performing calibration to correct, the orientation of the reference target is measured using a method (for example, digital beam forming method) having a higher resolution than the monopulse method. Failure to detect the azimuth only be determined to be valid the calibration Characterized in that it comprises a determining means.

  A method with higher resolution than the above-mentioned phase monopulse method is, for example, a digital beam forming method.

  According to the present invention, at the time of calibration, the multi-target state is determined by the azimuth measurement by the calculation algorithm having a higher resolution than the monopulse method, or the correct azimuth corresponding to the reference target arranged in the known azimuth is determined. By executing the calibration, it is possible to prevent the calibration based on the wrong direction due to the multi-target state, and it is possible to correctly perform the calibration of the monopulse radar apparatus.

  Embodiments of the present invention will be described below with reference to the drawings. However, such an embodiment does not limit the technical scope of the present invention.

  The calibration method of the monopulse radar apparatus according to the present invention performs azimuth measurement by another arithmetic algorithm having higher azimuth detection resolution than the phase monopulse method in an inspection process before shipment from the factory, and confirms that it is not a multi-target state. Another calculation algorithm is, for example, digital beam forming (DBF). DBF includes various methods such as a beam former method, a capon method, an LP method, MUSIC, and ESPRIT. Each method is described in detail, for example, on pages 174 to 189 of “Adaptive signal processing by array antenna” (Nobuyoshi Kikuma, published by Science and Technology Publishing, first edition of 1998). Detailed explanation in this specification is as follows. Omitted. As an example, an arithmetic expression of the beamformer method when the phase difference between the antennas AT0 and AT1 is used is described below together with the phase monopulse method.

(Phase monopulse method)
Phase difference = arctan2 (ATO phase)-arctan2 (AT1 phase)-correction value Direction = arcsin (phase difference * λ / 2 / π / (antenna spacing d)) * 180 * π
(Beam former method)
Azimuth power (iang) = (ATO phase / correction value * exp (-j * 2 * π * d * sin (iang)) +
AT1 phase / correction value * exp (-j * 2 * π * d * sin (iang)))
Note that iang is an input azimuth angle and is calculated from 1 to 180 degrees. Further, it is not necessary to divide the ATO phase and the AT1 phase by the correction value. By dividing by the correction value, the measurement angle with respect to the reference target is corrected to a known angle, but this is not always necessary for determining whether the target is a multi-target.

  The reason why the phase monopulse method is currently used as a calculation algorithm in a azimuth measuring radar apparatus mounted on a vehicle or the like is that the amount of calculation at one time is relatively small and the calculation time can be suppressed. When operating radar devices mounted on vehicles, etc., in order to be able to respond to sudden changes in the surroundings, such as pedestrians jumping out and vehicle interruptions, in a relatively short cycle (for example, several milliseconds) Therefore, a phase monopulse method is used which can perform one calculation within a relatively short time. On the other hand, the azimuth detection resolution of the phase monopulse method is inferior to another calculation algorithm with a large amount of calculation (for example, digital beam forming such as the above-mentioned beamformer method). May not be separated, and the direction detected and measured as one target may be different from the directions of the plurality of targets.

  In the inspection process for performing calibration before factory shipment, there is no limitation on the calculation time required for one measurement as in actual operation. Therefore, in order to perform azimuth calibration, when measuring the azimuth of a reference target arranged in a known azimuth, it is not always necessary to perform measurement using the phase monopulse method. Therefore, in the present invention, at the time of calibration, the orientation of the reference target is measured using a calculation algorithm having a resolution higher than that of the phase monopulse method. As a result, the orientation of multiple targets can be separated even when the orientation is measured in a state where another target is placed so close to the reference target that it cannot be separated by phase monopulse resolution. Each can be measured. That is, it is possible to determine whether or not a multi-target state that can occur in the azimuth measurement by the phase monopulse method. Thereby, it can prevent that calibration is performed based on an incorrect azimuth | direction, and calibration can be performed correctly.

  FIG. 3 is a process flowchart of the first calibration method according to the embodiment of the present invention. The first calibration method is performed using, for example, a calibration determination device (inspection device) externally connected to the phase monopulse radar device 1. FIG. 5 is a diagram schematically showing a state in which the calibration determination device 50 of the present invention is connected to the phase monopulse radar device. The calibration determination device 50 is a computer device such as a personal computer, for example, and stores and executes a computer program for measuring an azimuth by a calculation algorithm having a resolution higher than that of the phase monopulse method. FIG. 3 shows a processing flow of the entire first calibration method.

  In FIG. 3, first, the inspection worker arranges the reference target in a known direction (for example, 0 degrees) (S100). Thereafter, the phase monopulse radar device 1 is operated, and the radar device 1 obtains the phase difference of the received signal from the antenna, measures the azimuth of the reference target by the phase monopulse method, and further determines the measured azimuth and the known azimuth. Calibration for calculating a correction value based on the difference from the azimuth is executed (S101).

  Subsequently, the calibration determination device 50 acquires the reception phase difference information of the reflected wave received by the phase monopulse radar device 1 from the radar device 1, and uses a calculation algorithm (for example, DBF) with higher resolution than the phase monopulse method. The azimuth is measured (S102). Then, it is determined whether or not a plurality of azimuths are detected by this measurement (S103). If a plurality of azimuths are detected, it is determined that the azimuth obtained by the phase monopulse method is in the multi-target state, and an error is output. (S104). For example, the multi-target display is displayed on the display of the calibration apparatus to notify the inspection operator. In this case, the inspection operator removes the reflection source near the reference target and performs measurement again. On the other hand, when a plurality of azimuths are not detected, that is, when only one azimuth is detected, it is determined that the reference target is the correct azimuth (not in the multi-target state), and the calibration in step S101 is determined to be valid. The correction value obtained in step S101 is stored in the internal memory of the phase monopulse radar apparatus 1 (S105).

  Thus, in the first calibration method, it is confirmed whether or not the azimuth and the correction value obtained by the measurement by the phase monopulse method are those in the multi-target state by a calculation algorithm having a higher resolution than the phase monopulse method.

  In measurement using a calculation algorithm with higher resolution than the phase monopulse method, the phase difference corrected by the correction value obtained in step S101 may be used, or an uncorrected phase difference may be used. As described above, it is possible to determine whether or not the state is a multi-target state (whether a plurality of directions are detected) regardless of whether or not the phase difference is corrected. Further, the correction value may be obtained after it is determined not in step S101 but in step 103 that the multi-target state is not set.

  In the configuration of FIG. 5, the calibration determination device 50 is an external device connected to the radar device 1, but a computer program of an arithmetic algorithm executed by the calibration determination device 50 is installed in the radar device 1, and calibration is performed. Only the CPU of the radar apparatus 1 may execute it. That is, the radar apparatus itself performs calibration validity determination. When the radar apparatus 1 executes a calculation algorithm with a resolution higher than that of the phase monopulse method, the azimuth cannot be measured within one azimuth measurement time required during normal operation. However, since the measurement time does not matter at the time of calibration, the computer program of the high-resolution calculation algorithm is activated and executed. Only during the inspection process period, a computer program of an arithmetic algorithm having a higher resolution than that of the phase monopulse method may be installed in the storage device in the radar apparatus 1, and the computer program may be uninstalled after the inspection process is completed. This is because the computer program is not used after the inspection process is completed, and the storage area of the storage device of the radar apparatus 1 is effectively used.

  FIG. 4 is a process flowchart of the second calibration method in the embodiment of the present invention. In the second calibration method, the azimuth is also measured by a high resolution arithmetic algorithm. The second calibration method is also performed using, for example, a calibration determination device 50 that is externally connected to the phase monopulse radar device 1. FIG. 4 shows a processing flow of the entire second calibration method.

  In FIG. 4, as in the first calibration method, the inspection operator places the reference target in a known direction (S200). Thereafter, the phase monopulse radar device is operated, and the radar device 1 obtains the phase difference based on the received reflection signal from the antenna. The calibration determination apparatus 50 acquires this phase difference information, and measures the orientation of the reference target using a calculation algorithm with higher resolution than the phase monopulse method (S201).

  Further, the calibration determination device 50 determines whether or not a plurality of directions are detected by this measurement (S202). If a plurality of directions are not detected, that is, if only one direction is detected, the direction and the known direction are known. A correction value based on the difference from the reference target orientation is obtained (S203), and when a plurality of orientations are detected, the orientation of the reference target closest to the reference target orientation (known orientation) and the reference target orientation The correction value is calculated based on the difference between (S204) and the obtained correction value is stored in the internal memory of the phase monopulse radar device 1 (S205).

  In this way, in the second calibration method, since the azimuth is also measured by a calculation algorithm having a higher resolution than the phase monopulse method, there is no need to consider the multi-target state unlike the phase monopulse method, and only one azimuth is obtained. If detected, calibration may be performed based on the orientation, and if a plurality of orientations are detected, calibration may be performed based on the orientation closest to the orientation of the reference target.

  Similar to the first calibration method, the second calibration method of FIG. 4 has a higher resolution than the phase monopulse method even when the calibration determination device 50 is externally connected to the phase monopulse radar device 1. Any configuration in which a computer program of an arithmetic algorithm is installed in the radar apparatus 1 and the radar apparatus 1 functions as the calibration determination apparatus 50 can be realized.

  In the above-described embodiment, the calibration of the radar apparatus using the phase monopulse system has been described. However, the calibration is not limited to the phase monopulse system. For example, the calibration of the radar apparatus of another monopulse system such as the amplitude monopulse system is used. However, the present invention is applicable.

It is a figure explaining a phase monopulse system. It is a block diagram which shows the structure of the FM-CW radar apparatus of a phase monopulse system. It is a process flowchart of the 1st calibration method in embodiment of this invention. It is a process flowchart of the 2nd calibration method in embodiment of this invention. It is a figure which shows typically the state which the calibration determination apparatus 50 of this invention is connected to the phase monopulse system radar apparatus.

Explanation of symbols

  AT0, AT1, AT2: antenna, 10: voltage controlled oscillator (VCO), 14: transmission amplifier, 16: circulator 16, 26: reception amplifier, 28: mixer, 32: A / D converter, 34: fast Fourier transform unit, 36: CPU, 50: Calibration determination device

Claims (3)

In a calibration method of a radar apparatus having three or more antennas and measuring the azimuth of a target by a monopulse method based on a reflected wave received by a combination of two of the three or more antennas,
Based on the reflected wave, measure the orientation of a reference target placed in a known orientation using a monopulse method,
Perform calibration to correct the orientation measured using the monopulse method to the orientation of the reference target,
Based on the reflected wave, the orientation of the reference target is measured using a digital beam forming method, and the calibration is determined to be valid only when a plurality of orientations cannot be detected by the measurement. Calibration method. In a calibration determination apparatus for a radar apparatus having three or more antennas and measuring the azimuth of a target by a monopulse method based on a reflected wave received by a combination of two of the three or more antennas ,
Based on the reflected wave, the radar apparatus measures the azimuth of a reference target arranged in a known azimuth using a monopulse method, and executes calibration for correcting the measured azimuth to the azimuth of the reference target. An acquisition means for acquiring an information signal related to the reflected wave;
A determination unit that measures the azimuth of the reference target using a digital beam forming method based on the information signal and determines that the calibration is valid only when a plurality of azimuths cannot be detected by the measurement. A calibration determination apparatus characterized by the above. In a radar apparatus that has three or more antennas and measures the azimuth of a target by a monopulse method based on reflected waves received by a combination of two of the three or more antennas,
Measuring means for measuring the orientation of a reference target arranged in a known orientation using a monopulse method based on the reflected wave;
Calibration means for performing calibration for correcting the orientation measured by the measurement means to the orientation of the reference target;
A determination unit that measures the azimuth of the reference target based on the reflected wave using a digital beam forming method and determines that the calibration is valid only when a plurality of azimuths cannot be detected by the measurement. Radar apparatus characterized by the above.

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