JP2011089886A - Radar apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radar apparatus capable of positioning with high accuracy by canceling an effect of doppler ambiguity onto positioning and concurrently compensating for an effect of a range doppler coupling error, using information of measured angle values of a radar. <P>SOLUTION: The radar apparatus includes a transmitting and receiving sensor 1 for radiating radio waves to a target and a receiving sensor 2 for receiving the radio waves reflected on the target. The receiving sensor 2 includes pulse compression units 11, 12 for observing receiving time, doppler frequency and measured angle values from receiving radio waves, a doppler frequency detection unit 13, a receiving time difference detection unit 14, a sensor 1 information receiving unit 15, a measured angle processing unit 17, a doppler frequency candidate calculation unit 18, a positioning calculation unit 16A and a target position decision unit 19 for positioning while eliminating the fuzziness of a doppler frequency by doppler ambiguity using information of observed receiving time, doppler frequency and measured angle values. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention cancels the influence of Doppler ambiguity on positioning and uses the influence of the range Doppler coupling error by using the information of the radar angle value in addition to the information of the reception time of the received signal and the Doppler frequency. Further, the present invention relates to a radar apparatus that simultaneously corrects and performs highly accurate positioning.

  As described in Non-Patent Document 1, in a bistatic radar with one transmitting station and two receiving stations, the target distance (time) and the Doppler frequency are observed, and the target three-dimensional is calculated by the positioning calculation to the target. A position vector can be estimated. Such a bistatic radar positioning process uses a plurality of pieces of information on the target distance (time) and Doppler frequency, so that positioning accuracy higher than that of a conventional monostatic radar can be obtained.

  However, when considering a radar that performs pulse compression widely used in radar and operates in a low PRF (Pulse Repetition Frequency) mode, if the target Doppler frequency is observed from the phase change between pulse hits, the observation An ambiguity (hereinafter, Doppler ambiguity) occurs in the value, and a plurality of candidates exist as observed values of the Doppler frequency. Therefore, there is a problem that an incorrect positioning result is obtained unless Doppler ambiguity is excluded. Further, since the true value of the Doppler frequency is not known due to the Doppler ambiguity, there is also a problem that the range Doppler coupling error at the reception time caused by pulse compression cannot be corrected.

  A conventional bistatic positioning method will be described with reference to FIGS. FIG. 5 is a diagram showing a configuration of a conventional bistatic radar. FIG. 6 is a diagram illustrating a configuration of a reception sensor of a conventional radar apparatus. In the following, in each figure, the same reference numerals indicate the same or corresponding parts. Next, problems when applied to the low PRF radar will be described.

  The transmission / reception sensor 1 has both radio wave transmission and reception capabilities, radiates radio waves to a moving target, and receives the target reflected waves. The reception sensor 2 receives a radio wave, receives a target reflected wave radiated from the transmission / reception sensor 1 and reflected in the direction of the reception sensor 2, and a direct wave directly propagated from the transmission / reception sensor 1 to the reception sensor 2. Prior to this, communication from the transmission / reception sensor 1 to the reception sensor 2 is also performed, and the distance between the transmission / reception sensor 1 and the target observed from the position vector and velocity vector of the transmission / reception sensor 1 and the target reflected wave received by the transmission / reception sensor 1. , And the target velocity vector is transmitted to the receiving sensor 2.

  The positioning process shown in FIG. 6 is performed by the reception sensor 2 of FIG. Assume that pulse compression using a chirp signal is performed in the pulse compression units 11 and 12 as preprocessing. In FIG. 6, the Doppler frequency detection unit 13 observes the Doppler frequency from the target reflected wave received by the reception sensor 2, and the reception time difference detection unit 14 receives the target reflected wave received by the reception sensor 2 and the reception sensor from the transmission / reception sensor 1. The direct wave reception time difference to 2 is observed. The sensor 1 information receiving unit 15 acquires the distance between the transmission / reception sensor 1 and the target, the target velocity vector, the position vector and the velocity vector of the transmission / reception sensor 1 from the communication wave transmitted from the transmission / reception sensor 1 to the reception sensor 2. . At this time, between each information acquired by the Doppler frequency detection unit 13, the reception time difference detection unit 14, and the sensor 1 information reception unit 15 and the target position vector to be solved, the following equations (1) to (3) The relationship of the equation is established.

In equations (1) to (3), p represents a position vector, v represents a velocity vector, subscripts 1, 2, and T represent the transmission / reception sensor 1, the reception sensor 2, and the target, respectively. t _TDOA is the reception time difference observed by the reception time difference detection unit 14, f _FOA is the Doppler frequency observed by the Doppler frequency detection unit 13, R _target is the target distance acquired by the sensor 1 information reception unit 15, c Represents the propagation speed of radio waves, and f ₀ represents the transmission frequency. Also, in equation (3), the variable on the left side is the distance, which is equivalent to the equation for the reception time. Simultaneous equations in the positioning calculation unit 16 Equation (1) to (3) by solving for the target position vector p _T a, estimates the three-dimensional position vector of the target. The simultaneous equations are non-linear equations, but can be solved by an iterative improvement method (Gauss-Newton method) using linear approximation.

  However, when the radio wave radiated to the target is a low PRF, a Doppler ambiguity corresponding to the PRF is generated in the Doppler frequency received by the receiving sensor 2 and detected by the Doppler frequency detector 13. This Doppler ambiguity is an integer in which the phase change amount observed between pulse hits is 2π because there is a possibility that the phase change amount between pulse hits exceeds 2π when the pulse hit interval is long. This means that the Doppler frequency has an ambiguity that is an integral multiple of the PRF with respect to the observed value. At this time, the true Doppler frequency is one of values obtained by adding an integer multiple of the PRF to the observed value of the Doppler frequency. Therefore, if this ambiguity is eliminated and the true Doppler frequency cannot be determined, a plurality of positioning result candidates exist. Therefore, if the Doppler ambiguity cannot be excluded, there is a problem that an incorrect positioning result is obtained.

  In addition, when using pulse compression by chirp signals or the like in the pulse compression units 11 and 12 in FIG. 6, the frequency of the target reflected wave changes due to Doppler shift due to target movement, and the peak of the pulse after pulse compression occurs. An error called a range Doppler coupling error occurs. If this error cannot be ignored, the range Doppler coupling error is expressed as a function of the Doppler frequency and can be corrected by the observed Doppler frequency. That is, a correction term for a range Doppler coupling error may be added to the right side of equation (1). However, since there is a problem of Doppler ambiguity as described above, there is a problem that the true Doppler frequency is not determined, and the range Doppler coupling error cannot be corrected. In the case of the processing of FIG. 6, the range Doppler coupling error generated in the pulse compression units 11 and 12 is added to the reception time difference detected by the reception time difference detection unit 14, and the positioning calculation unit 16 There is a problem that an error also occurs in the positioning result.

K. C. HO: "An Accurate Algebraic Solution for Moving Source Location Using TDOA and FDOA Measurements" IEEE Trans. On Signal Processing, Vol.52, No.9, Sep. 2004

  However, the above prior art has the following problems. That is, in a bistatic radar that uses pulse compression and operates at a low PRF, a problem that a true target position vector cannot be estimated by a plurality of observation Doppler frequency candidates corresponding to Doppler ambiguity, and frequency modulation When pulse compression is used, there is a problem that the reception time has a range Doppler coupling error. There is a problem in that it is necessary to correct a ranging error caused by these two problems and perform highly accurate positioning.

  The present invention has been made to solve the above-described problems, and uses Doppler ambiguity by using radar angle measurement information in addition to reception signal reception time and Doppler frequency information. An object of the present invention is to obtain a radar apparatus capable of canceling the influence on the positioning and correcting the influence of the range Doppler coupling error at the same time and performing highly accurate positioning.

  A radar apparatus according to the present invention includes a transmission sensor that radiates radio waves to a target, and first and second reception sensors that receive radio waves reflected by the target, the first or second The reception sensor uses the means for observing the reception time, Doppler frequency and angle measurement value from the received radio wave, and the Doppler frequency ambiguity due to the Doppler ambiguity using the information on the observed reception time, Doppler frequency and angle measurement value. And means for performing positioning while eliminating the above.

  According to the radar apparatus of the present invention, in addition to the information on the reception time of the received signal and the Doppler frequency, the information on the angle value of the radar is used to cancel the influence on the positioning of the Doppler ambiguity and the range. The influence of the Doppler coupling error is also corrected at the same time, and highly accurate positioning can be performed.

It is a figure which shows the structure of the receiving sensor of the radar apparatus which concerns on Embodiment 1 of this invention. It is a figure which shows the selection method in the target position determination part of the receiving sensor of the radar apparatus which concerns on Embodiment 1 of this invention. It is a figure which shows another structure of the radar apparatus which concerns on Embodiment 1 of this invention. It is a figure which shows the structure of the receiving sensor of the radar apparatus which concerns on Embodiment 2 of this invention. It is a figure which shows the structure of the conventional bistatic radar. It is a figure which shows the structure of the receiving sensor of the conventional radar apparatus.

  A preferred embodiment of a radar apparatus according to the present invention will be described below with reference to the drawings.

Embodiment 1 FIG.
A radar apparatus according to Embodiment 1 of the present invention will be described with reference to FIGS. 1 to 3 and FIG. 1 is a diagram showing a configuration of a reception sensor of a radar apparatus according to Embodiment 1 of the present invention. FIG. 2 is a diagram showing a selection method in the target position determination unit of the reception sensor of the radar apparatus according to Embodiment 1 of the present invention. FIG. 3 is a diagram showing another configuration of the radar apparatus according to Embodiment 1 of the present invention.

  In FIG. 1, a reception sensor 2 of a radar apparatus according to Embodiment 1 of the present invention includes a pulse compression unit 11, a pulse compression unit 12, a Doppler frequency detection unit 13, a reception time difference detection unit 14, and a sensor 1. An information reception unit 15, a positioning calculation unit 16 </ b> A, an angle measurement processing unit 17, a Doppler frequency candidate calculation unit 18, and a target position determination unit 19 are provided.

  In FIG. 1, that is, in addition to each processing unit in the conventional positioning process of FIG. 6 shown above, an angle measurement processing unit 17, a Doppler frequency candidate calculation unit 18, and a target position determination unit 19 are added, and a positioning calculation unit 16 is replaced with a positioning calculation unit 16A. Further, FIG. 1 also assumes a case where processing is performed in the reception sensor 2 of FIG. 5, as in the case of FIG. 6.

  Next, the operation of the radar apparatus according to the first embodiment will be described with reference to the drawings.

  In the first embodiment, positioning is performed while coping with a problem caused by Doppler ambiguity by using the processing of the configuration shown in FIG. In the flow of positioning processing shown in FIG. 1, the Doppler frequency detection unit 13 and the reception time difference detection unit 14 perform Doppler frequency and reception time from the target reflected wave and direct wave subjected to the pulse compression processing by the pulse compression units 11 and 12. Differences are observed. In addition, the angle measurement processing unit 17 newly performs angle measurement processing on the target reflected wave, and observes the arrival direction (angle measurement value) of the target reflected wave with respect to the reception sensor 2. At this time, the Doppler frequency detected by the Doppler frequency detection unit 13 shown in FIG. 1 is influenced by the Doppler ambiguity, and therefore has a plurality of candidates according to the PRF as in the following equation (4). .

In this equation (4), _fFOA (n) tilde is a set of Doppler frequency candidates, _fFOA is a Doppler frequency detected by the Doppler frequency detector 13, PRF is a target reflected wave and direct wave PRF, and n is an integer. N _max and N _min are the upper and lower limits of n determined from the assumed maximum and minimum values of the target relative speed.

The Doppler frequency candidate calculation unit 18 in FIG. 1 calculates Doppler frequency candidates f _FOA (n) tildes for any N _max to N _min according to Equation (4), and sends all candidates to the positioning calculation unit 16A. This positioning calculation unit 16A performs positioning calculation using the following equations (5), (6), and (7).

Expressions (5) to (7) correspond to Expressions (1) to (3) in the conventional case, respectively. p _T (n) represents a target position coordinate candidate corresponding to f _FOA (n) tilde, and is an object to be solved for the simultaneous equations. In addition, in Equation (5), a correction term for a range Doppler coupling error that was not found in Equation (1) is added at the end of the right side. Δt represents the pulse width of the chirp signal, and B represents its bandwidth. With this correction term, the reception time difference is corrected according to _fFOA (n) tilde, and the target position vector candidate p _T (n) in which the range Doppler coupling error is canceled is obtained. The positioning calculation unit 16A solves the equations (5) to (7) for all the _fFOA (n) tildes and obtains all target position vector candidates p _T (n). Equation (5) shows a correction term when linear chirp is used as pulse compression. When other pulse compression such as non-linear chirp is used, a correction term corresponding to that is used.

  The plurality of target position vector candidates obtained by the positioning calculation unit 16A are sent to the target position determination unit 19 together with the angle measurement values obtained by the angle measurement processing unit 17, where one target position vector is the final positioning result. Selected as. The selection method in the target position determination unit 19 is shown in FIG. In FIG. 2, it is assumed that three position vectors exist as target position vector candidates. At this time, the linear direction from the receiving sensor 2 to each target position vector candidate ideally matches the angle measurement value obtained by the angle measurement processing unit 17. Therefore, the target position determination unit 19 calculates an angle formed by the direction of the angle measurement value and the direction of each target position vector candidate, and determines the smallest target position vector as the final target position vector.

  As described above, in the first embodiment, the positioning processing is performed on all the Doppler frequency candidates using the conventional positioning processing, and the information of the angle measurement values is used for those positioning results. The positioning result corresponding to the Doppler frequency is selected. In addition, for each Doppler frequency candidate, positioning is performed while correcting the range Doppler coupling error using the value of the Doppler frequency candidate, so that the finally selected positioning result is the range Doppler frequency. Coupling errors are also corrected correctly. This realizes positioning having two functions of dealing with the Doppler ambiguity problem and correcting the range Doppler coupling error.

  In the description so far, the processing by the reception sensor 2 in FIG. 5 is assumed. However, information is transmitted from the reception sensor 2 to the transmission / reception sensor 1 by communication waves, and the same processing is performed by the transmission / reception sensor 1. There is no problem if done. In addition, the information observed for the positioning calculation has two distances (time) and one Doppler frequency, but it may have one or two distances (time) and two Doppler frequencies. A corresponding equation may be used. Further, although an example in which the angle measurement process and the Doppler frequency detection process are also performed by the reception sensor 2 has been described, even if these are performed by the transmission / reception sensor 1, the positioning can be performed in the same manner.

  Up to this point, a positioning system having one transmission / reception sensor 1 and one reception sensor 2 as shown in FIG. 5 has been considered. However, in the present embodiment, for example, a transmission sensor 1 as shown in FIG. The same processing is possible with two receiving sensors. In FIG. 3, the transmission sensor 1A emits radio waves to the target, and the reception sensor 2A and the reception sensor 2B receive the reflected waves. Known information such as the reception time, Doppler frequency, angle measurement value, each sensor position vector, and target velocity vector observed by each sensor is shared by the reception sensor 2A through the communication wave, and the processing is performed according to the processing flow shown in FIG. By doing so, the same effect as the configuration of FIG. 5 is realized.

  As described above, in the first embodiment, each piece of information is acquired by two sensors, they are finally shared, a positioning process is performed, and a solution is selected using a measured angle value for the positioning result. .

Embodiment 2. FIG.
A radar apparatus according to Embodiment 2 of the present invention will be described with reference to FIG. 4, FIG. 5, and FIG. FIG. 4 is a diagram showing the configuration of the reception sensor of the radar apparatus according to Embodiment 2 of the present invention.

  In FIG. 4, the reception sensor 2 of the radar apparatus according to the second embodiment of the present invention includes a pulse compression unit 11, a pulse compression unit 12, a Doppler frequency detection unit 13, a reception time difference detection unit 14, and a sensor 1. An information receiving unit 15, a positioning calculation unit 16B, and an angle measurement processing unit 17 are provided.

  Next, the operation of the radar apparatus according to the second embodiment will be described with reference to the drawings.

  As in the first embodiment, the second embodiment also realizes positioning having two functions of dealing with the Doppler ambiguity problem and correcting the range Doppler coupling error. In the first embodiment, the solution selection using the angle measurement value is performed after the positioning calculation. In the second embodiment, the angle calculation value is used at the stage of the positioning calculation, and the amount of information in the positioning calculation is increased. Solve the target position vector and Doppler ambiguity at the same time.

  FIG. 4 shows the flow of processing assuming the case where processing is performed by the reception sensor 2 in FIG. 5, similarly to the description in the first embodiment. In FIG. 4, the Doppler frequency detection unit 13, the reception time difference detection unit 14, and the angle measurement processing unit 17 perform Doppler frequency and reception from the target reflected wave and direct wave that have been subjected to pulse compression processing by the pulse compression units 11 and 12. Time difference and angle measurement values are extracted. In addition, various information from the transmission / reception sensor 1 is acquired by the sensor 1 information receiving unit 15 as before. All the information acquired so far is sent to the positioning calculation unit 16B, and positioning processing is performed.

  In the positioning calculation unit 16B, in addition to the three equations for the relationship between the reception position difference, the Doppler frequency, the target distance and the target position vector used in the conventional positioning calculation unit 16 and the positioning calculation unit 16A, An equation for the relationship between the value and the target position vector is also used. At this time, the positioning equation is as follows.

Equations (11) and (12) are equations for the angle measurement value at the receiving sensor 2. Here, since it is assumed that two-dimensional angle measurement is performed, two equations are added. θ ₂ represents a measured value of the elevation angle of the arrival direction of the target reflected wave in the receiving sensor 2, φ ₂ represents a measured value of the azimuth, and x, y, and z represent three-dimensional values of the position vector p, respectively. Represents ingredients. Further, f _amb is added as a new variable to the equation (9). This is a variable that represents the difference between the observed Doppler frequency f _FOA and the true Doppler frequency, and the true Doppler frequency can be written as f _FOA -f _amb . In accordance with this, the portion corresponding to the Doppler frequency in the correction term of the range Doppler coupling error in the equation (8) is described as f _FOA -f _amb . The correction term for the range Doppler coupling error here is also a description in the case where a linear chirp signal is used in the pulse compression units 11 and 12, and it is necessary to correct the correction term according to the type of pulse compression used. There is.

In the second embodiment, the formula (8) to (12) rather than solving only with conventional target position vector p _T, f _amb also perform treatment target position vector p _T simultaneously solving as a variable of solving the subject. Thereby, the error between the true Doppler frequency and the observed Doppler frequency due to the Doppler ambiguity is corrected in the positioning calculation, and the true target position vector is obtained as a solution for the positioning calculation. In addition, since the Doppler frequency is corrected in the positioning calculation, _fFOA− f _amb used in the range Doppler coupling error correction term of Equation (8) is also a true Doppler frequency value, and the range is not included in the positioning calculation itself. This has the effect of correcting the Doppler coupling error.

  As described above, in the second embodiment, by adding the relational expression between the angle measurement value and the target position vector to the positioning calculation, not only the conventional target position vector but also the true Doppler frequency and the observed Doppler frequency by the Doppler ambiguity In this case, the positioning error can be solved, and the influence of Doppler ambiguity can be eliminated and the range Doppler coupling error can be corrected.

  In the description so far, the two-dimensional angle measurement value in the reception sensor 2 of FIG. 5 is used as the angle measurement result, but only one of the elevation angle and the azimuth angle of the reception sensor 2 may be used. Only the angle measurement value of the transmission / reception sensor 1 or both of the angle measurement results of the transmission / reception sensor 1 and the reception sensor 2 may be used, and the number of equations varies depending on the number, but the positioning has the same effect. Processing is possible. As for the Doppler frequency, the frequency observed by the transmission / reception sensor 1 as well as the reception sensor 2 may be used. However, when two Doppler frequencies are used, the error variable between the true Doppler frequency and the observed Doppler frequency due to the Doppler ambiguity appears in each equation. Do. As in the example of the first embodiment, even in the second embodiment, there is no problem even if processing is performed by the transmission / reception sensor 1.

  Further, similarly to the example of the first embodiment, also in the second embodiment, it is possible to perform processing using the sensor configuration of FIG. Even in this case, the observation values and known information of the reception sensors 2A and 2B are collected at one place (for example, the reception sensor 2A), and the Doppler ambiguity and the range Doppler coupling error are obtained by performing the same processing as in FIG. Positioning can be performed while correcting these two problems.

  As described above, in the second embodiment, the observation values of the two sensors are shared, and the positioning calculation by the simultaneous solution of the true Doppler frequency and the Doppler frequency error by the Doppler ambiguity and the target position vector is performed. Is called.

  DESCRIPTION OF SYMBOLS 1 Transmission / reception sensor, 1A transmission sensor, 2A reception sensor, 2B reception sensor, 11 Pulse compression part, 12 Pulse compression part, 13 Doppler frequency detection part, 14 Reception time difference detection part, 15 Sensor 1 information reception part, 16A Positioning calculation part , 16B positioning calculation unit, 17 angle measurement processing unit, 18 Doppler frequency candidate calculation unit, 19 target position determination unit.

Claims (10)

A transmission sensor that emits radio waves to the target;
First and second receiving sensors for receiving radio waves reflected by the target,
The first or second receiving sensor is
Means for observing the reception time, Doppler frequency, and angle measurement value from the received radio wave;
Means for performing positioning while eliminating ambiguity of Doppler frequency due to Doppler ambiguity using information on observed reception time, Doppler frequency, and angle measurement value. The radar apparatus according to claim 1, wherein a transmission / reception sensor includes the transmission sensor and the first or second reception sensor. The means for performing positioning estimates all positioning result candidates using positioning calculation with respect to all Doppler frequency candidates and reception time, and uses a positioning value from among all positioning result candidates. The radar apparatus according to claim 1 or 2, wherein a vector is selected. The means for performing the positioning, as selection of the target position vector using the angle measurement value, an angle formed by the direction of the angle measurement value based on the receiving sensor that observed the angle measurement value and the direction of the candidate of the positioning result The radar apparatus according to claim 3, wherein the radar apparatus calculates and selects a positioning result candidate having the smallest angle as a target position vector. The means for performing the positioning uses the reception time, the Doppler frequency, and the angle measurement value simultaneously for the positioning calculation, and simultaneously solves the difference between the observed Doppler frequency and the true Doppler frequency by the target position vector and the Doppler ambiguity. The radar apparatus according to claim 1, wherein a true target position vector is measured. The positioning means introduces a range Doppler coupling error correction term into the positioning equation in the positioning calculation, thereby eliminating the Doppler frequency ambiguity due to Doppler ambiguity and correcting the range Doppler coupling error. The radar apparatus according to claim 3, wherein positioning is also performed. The radar apparatus according to any one of claims 1 to 6, wherein the positioning means uses a total of three pieces of information on reception time and Doppler frequency. The radar device according to any one of claims 1 to 6, wherein the positioning means uses a total of four pieces of information on reception time and Doppler frequency. The radar apparatus according to any one of claims 1 to 8, wherein the means for performing positioning uses an angle measurement value of one of two sensors that perform reception. The radar apparatus according to any one of claims 1 to 8, wherein the positioning means uses angle values of both of two sensors that perform reception.

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