JP5163765B2 - Angle measuring device, radar device, angle measuring method and angle measuring program - Google Patents

Description

  The present invention relates to a radar device or the like for detecting a target, and more particularly to an angle measurement technique for detecting elevation angle information of a target in a multipath environment where there is a reflected wave from the ground or the sea surface.

  A radar device generally detects the presence of a target by observing the position and movement status of the target by emitting a radio wave into space and receiving a reflected signal from the target. In the radar apparatus, a radio wave (transmission beam) is emitted from the antenna to the space, is reflected by the target, is received by the antenna again, and is output as a radar reception signal to a receiver or the like. The radar reception signal is A / D converted at a predetermined sampling interval, the amplitude value of the digital reception signal at each sampling point is compared with a threshold value, and a digital reception signal equal to or higher than the threshold value is determined as a target signal. Thus, the target signal is detected. In the distance measurement process, target distance information is obtained based on the difference between the time when the radio wave is emitted and the time when the target signal is detected. This target detection and distance information measurement are the basic functions and the simplest configuration of the radar apparatus.

  Target azimuth information can be obtained by changing the azimuth of the transmission beam, obtaining radar reception signals having different azimuths, and performing azimuth measurement processing. Furthermore, by emitting multiple transmit beams with different elevation angles, receiving reflected signals from the same target, and performing elevation angle measurement processing using the amplitude difference and phase difference of the received signals with different elevation angles, the altitude information of the target is obtained. Can be obtained.

  The process of launching radio waves in the space you want to observe is called scanning. The radar apparatus can acquire target information continuously at a predetermined interval by repeatedly performing a scanning operation. For example, an amplitude comparison method and a monopulse method are known as representative angle measuring methods.

  In the case of the amplitude comparison method, a target is detected with a plurality of beams set continuously in the elevation angle direction, and an angle measurement value is obtained using a beam with the highest received intensity. As a countermeasure against multipath, an amplitude comparison method in which the directional center of the received beam is shifted upward (off-bore) is used. By this method, the influence of the reflected wave from the ground or the sea surface is reduced.

  On the other hand, in the monopulse method, the arrival angle of the direct wave is obtained by utilizing the relationship that the sum-and-difference division signal Δ / Σ draws a constant characteristic curve with respect to the elevation angle θ.

  In an environment where the influence of multipath can be ignored, data with higher accuracy can be obtained by using the monopulse method than when using the amplitude comparison angle measurement method. However, when the monopulse method is used, it is known that the angle measurement accuracy deteriorates in a multipath environment (Non-Patent Document 1). This is because the shape of the difference beam in the monopulse beam shape is easy to receive indirect waves. In other words, for low elevation targets in a multipath environment, in addition to direct waves from the target, indirect waves that have reflected on the ground or the sea surface and propagated through other paths also arrive, so the sum signal of the received signal and This is because Δ / Σ, which is the result of complex division with the difference signal, is observed as a value different from Δ / Σ in the case of only the direct wave.

  In fact, in a multipath environment, during the observation period, (1) the target is moving at a long distance with a low elevation angle, so the change in elevation angle associated with the movement of the target can be ignored. (2) Direct waves and multipath Under the condition that the change of the relative amplitude ratio with the indirect wave is small and (3) the fluctuation of the relative phase difference φ between the direct wave and the indirect wave is large, Δ / Σ is complex as shown in FIG. A circular locus 100 is drawn on a plane (Non-Patent Document 1).

  On the other hand, there is a technique disclosed in Patent Document 1 as means for realizing highly accurate angle measurement by a monopulse method in a multipath environment. A schematic configuration diagram thereof is shown in FIG. The feature of this technique is that it includes the first circle center calculation means 103 and the angle conversion means 104. The first circle center calculation means 103 calculates the radius and center coordinates of the circle locus 100 drawn by Δ / Σ on the complex plane based on Δ / Σ calculated by the complex division means 102. The angle conversion means 104 calculates the arrival angle of the direct wave from the radius and the center coordinates obtained by the first circle center calculation means 103.

  Here, in order to perform highly accurate angle measurement in a multipath environment, it is necessary to accurately obtain the circular locus 100 shown in FIG. For this reason, Patent Document 1 discloses a method in which radio waves having the same frequency are transmitted at a certain interval, observed three times or more, and three or more different Δ / Σ coordinates on the complex plane are obtained. This method uses the fact that when the target is moving, the relative phase difference φ between the direct wave and the indirect wave changes due to the distance from the target changing. By keeping the time interval of each observation to some extent, the observation points on the complex plane are plotted in a positional relationship apart from each other as shown in the example of the observation points 101a, 101b, and 101c in FIG. It becomes possible to obtain the circular locus 100 with high accuracy from the coordinates of the observation point. However, if the time interval of each observation is shortened, each point approaches as in the example of the observation points 101d, 101e, and 101f on the complex plane in FIG. Becomes difficult. Therefore, in order to obtain a circular locus with high accuracy, the target needs to move to some extent during observation, and observation over a plurality of scans is necessary in practice.

  Other related techniques for eliminating the influence of multipath are disclosed in Patent Documents 2, 3 and the like.

Japanese Patent No. 3353991 JP 2010-85283 A Japanese Patent Laid-Open No. 11-118919

Samuel M. Sherman; “Monopulse Principles and Techniques”, Artech House, Inc. 1983

  In the multipath environment where there is a reflected wave from the ground or the sea surface, when the off-bore method is adopted among the amplitude comparison methods, if the off-bore method is used, the received signal from the target will be weakened, making target detection itself difficult. There is a problem of becoming.

  On the other hand, in the method of Patent Document 1 using the monopulse method, it is necessary to obtain different Δ / Σ coordinates on the complex plane. At this time, since the same ΣΔ beam having the same frequency is emitted a plurality of times, observation over a plurality of scans is necessary in practice, and there is a problem that the observation time becomes long.

  An object of the present invention is to solve the above-described problems of the technology, and to obtain an angle measuring device and the like that enable more accurate elevation angle estimation in a short time under a multipath environment.

The angle measuring device according to the present invention includes:
A first elevation angle calculation unit for calculating a direct wave elevation angle and an indirect wave elevation angle based on a received signal;
A second elevation angle calculation unit that calculates only the direct wave elevation angle based on the received signal;
When both the direct wave elevation angle and the indirect wave elevation angle are calculated by the first elevation angle calculation unit, the direct elevation angle calculated by the first elevation angle calculation unit is output, and the first elevation angle calculation unit outputs the direct wave elevation angle. If both the direct wave elevation angle and the indirect wave elevation angle are not calculated, a direct wave elevation angle output unit that outputs the direct wave elevation angle calculated by the second elevation angle calculation unit;
It is provided with.

A radar apparatus according to the present invention
An antenna that radiates a transmission radio wave for radar and receives a reflected wave from a target corresponding to the transmission radio wave,
A transceiver for outputting a high-frequency signal to the antenna and detecting a signal received by the antenna;
A beam former that forms a plurality of reception beams from a signal after reception processing by the transceiver and extracts a reception signal in each reception beam formed;
A target detector for detecting a target based on a received signal in each beam formed by the beam former;
When the target is detected by the target detector, the reception beam necessary for angle measurement processing is selected from the reception signals formed by the beam former, and the reception signal obtained by the reception beam is selected. Or a beam selector to be formed;
An angle measuring device according to the present invention for performing angle measurement processing based on the selected received beam and a received signal calculated by the received beam;
It is provided with.

The angle measuring method according to the present invention is:
The first elevation angle calculation unit calculates a direct wave elevation angle and an indirect wave elevation angle based on the received signal,
A second elevation angle calculator calculates only the direct wave elevation angle based on the received signal;
The direct wave elevation angle output unit outputs the direct wave elevation angle calculated by the first elevation angle calculation unit when both the direct wave elevation angle and the indirect wave elevation angle are calculated by the first elevation angle calculation unit, When both the direct wave elevation angle and the indirect wave elevation angle are not calculated by the first elevation angle calculation unit, the direct wave elevation angle calculated by the second elevation angle calculation unit is output.
It is characterized by that.

The angle measuring program according to the present invention is:
First elevation angle calculating means for calculating a direct wave elevation angle and an indirect wave elevation angle based on a received signal;
Second elevation angle calculating means for calculating only the direct wave elevation angle based on the received signal; and
When both the direct wave elevation angle and the indirect wave elevation angle are calculated by the first elevation angle calculation means, the direct wave elevation angle calculated by the first elevation angle calculation means is output, and the first elevation angle calculation means outputs the direct wave elevation angle. Direct wave elevation angle output means for outputting the direct wave elevation angle calculated by the second elevation angle calculation means when both the direct wave elevation angle and the indirect wave elevation angle are not calculated,
It is for making a computer function as.

  According to the present invention, by calculating a direct wave elevation angle in consideration of not only a direct wave but also an indirect wave, highly accurate angle measurement can be performed in a short time in a multipath environment. In addition to this, since the angle measurement processing assuming the case of only the direct wave is also used, angle measurement is possible regardless of the presence or absence of the influence of multipath.

1 is a block diagram illustrating a radar device according to a first embodiment. It is a block diagram which shows the angle measuring processor (angle measuring apparatus of Embodiment 1) in FIG. 3 is a graph showing a reception beam formed in the first embodiment. It is explanatory drawing which shows a multipath environment typically. It is a graph which shows the calculation result of Formula (8), FIG. 5 [A] is a graph which shows an example when two solutions are calculated | required, and FIG. 5 [B] is a case where two solutions are not calculated | required. It is a graph which shows an example. 6A is a flowchart illustrating an example of the angle measurement method according to the first embodiment, and FIG. 6B is a block diagram illustrating an example of a computer that executes the angle measurement program according to the first embodiment. It is a block diagram which shows the 1st example (when DBF is employ | adopted) of the radar apparatus of Embodiment 2. FIG. It is a block diagram which shows the 2nd example (when ABF is employ | adopted) of the radar apparatus of Embodiment 2. FIG. 6 is a graph showing a reception beam formed in the second embodiment. FIG. 10A is a graph showing how Δ / Σ draws a circular locus on the complex plane in a multipath environment, and FIG. 10B is a block diagram showing the angle measuring device described in Patent Document 1. .

  Hereinafter, embodiments of the present invention that solve the above-described problems will be described in detail with reference to the drawings. In all the drawings, the same components are denoted by the same reference numerals.

<Embodiment 1>
FIG. 1 is a block diagram illustrating a radar apparatus according to the first embodiment. FIG. 2 is a block diagram showing the angle measuring processor in FIG. Hereinafter, description will be given based on these drawings. The first embodiment also includes embodiments of the angle measuring device, the angle measuring method, and the angle measuring program in addition to the radar device.

  The angle measuring device 5 as the angle measuring apparatus according to the first embodiment includes a first elevation angle calculating unit 51, a second elevation angle calculating unit 52, and a direct wave elevation angle output unit 50. The first elevation angle calculation unit 51 calculates a direct wave elevation angle and an indirect wave elevation angle based on the received signal. The second elevation angle calculation unit 52 calculates only the direct wave elevation angle based on the received signal. The direct wave elevation angle output unit 50 outputs the direct wave elevation angle calculated by the first elevation angle calculation unit 51 when the first elevation angle calculation unit 51 calculates both the direct wave elevation angle and the indirect wave elevation angle. When both the direct wave elevation angle and the indirect wave elevation angle are not calculated by the calculation unit 51, the direct wave elevation angle calculated by the second elevation angle calculation unit 52 is output.

  Here, the three reception beams are beam 1, beam 2, and beam 3, the reception signal for beam 1 is reception signal 1, the reception signal for beam 2 is reception signal 2, and the reception signal for beam 3 is The received signal is 3. Further, it is assumed that the received signal 1 includes a beam pattern 1 that is a function of elevation angle, the received signal 2 includes a beam pattern 2 that is a function of elevation angle, and the received signal 3 includes a beam pattern 3 that is a function of elevation angle. .

  At this time, the first elevation angle calculation unit 51 may include a beam pair selection unit 511 and an elevation angle search unit 512. The beam pair selection unit 551 selects the beam pair 1 composed of the beam 1 and the beam 2 and the beam pair 2 composed of the beam 2 and the beam 3 from the three reception beams. The elevation angle search unit 512 calculates a complex phase obtained by subtracting the received signal 2 from the received signal 1 with respect to the beam pair 1 by weighting the phase correction term consisting of the quotient of the beam pattern 1 and the beam pattern 2. 2, the complex phase obtained by subtracting the received signal 3 from the received signal 2 with the weight of the phase correction term consisting of the quotient of the beam pattern 2 and the beam pattern 3 is calculated, and the difference between the phases is zero or 180 degrees. Search for an elevation that satisfies a condition equal to an integer multiple of.

  The direct wave elevation angle output unit 50 may include an indirect wave determination unit 54 and a direct wave elevation angle extraction unit 55. The indirect wave determination unit 54 determines that the first elevation angle calculation unit 51 uses the calculation result by the first elevation angle calculation unit 51 when two elevation angles satisfying the above condition are obtained by the first elevation angle calculation unit 51. If two elevation angles satisfying the above conditions are not obtained, a determination is made using the calculation result by the second elevation angle calculation unit 52. When the indirect wave determination unit 54 determines that the calculation result by the first elevation angle calculation unit 51 is used, the direct wave elevation angle extraction unit 55 outputs the larger one of the two elevation angles satisfying the above condition as the direct wave elevation angle. . When the indirect wave determination unit 54 determines that the calculation result by the second elevation angle calculation unit 52 is used, the second elevation angle calculation unit 52 outputs the calculation result by the second elevation angle calculation unit 52 as a direct wave elevation angle.

  The angle measurement processor 5 may further include a parameter output unit 53. The parameter output unit 53 outputs parameters necessary for the calculation to the first elevation angle calculation unit 51 and the second elevation angle calculation unit 52. The parameter output unit 53 may be omitted, and the function of the parameter output unit 53 may be provided to each of the first elevation angle calculation unit 51 and the second elevation angle calculation unit 52.

  The radar apparatus 10 according to the first embodiment radiates a transmission wave for radar and receives an reflected wave from a target corresponding to the transmission radio wave, and outputs a high-frequency signal to the antenna 1 while using the antenna 1. A transmitter / receiver 2 for detecting a received signal, a beam former 3 for forming a plurality of reception beams from a signal after reception processing by the transmitter / receiver 2, and extracting a reception signal in each formed reception beam; A target detector 4 for detecting a target based on the received signal in each beam formed by the former 3 and a received signal formed by the beam former 3 when the target detector 4 detects the target. A beam selector 6 that selects a reception beam necessary for angle measurement processing and selects or forms a reception signal obtained by the reception beam, and the selected reception beam and the reception beam. It includes a angle measuring processor 5 for performing angle measuring process based on the received signal calculated by the beam, the.

  The beam former 3 forms all the reception signals necessary for the angle measurement processing at the same time, and performs the processing in the second elevation angle calculation unit 52 and the three or more reception beams necessary for the processing in the first elevation angle calculation unit 51. A necessary reception beam may be formed. The beam selector 6 may select three reception beams necessary for processing in the first elevation angle calculation unit 51.

  Hereinafter, the first embodiment will be described in more detail.

  A radar apparatus 10 according to the first embodiment includes an antenna 1, a transceiver 2, a beam former 3, a target signal detector 4, a beam selector 6, and an angle measurement processor 5 as an angle measurement apparatus. The beam former 3, the target signal detector 4, the beam selector 6, and the angle measurement processor 5 constitute a signal processor 8.

  The transceiver 2 outputs a high frequency signal to the antenna 1. Then, the antenna 1 radiates a high-frequency signal in a predetermined direction in the air, receives a radio wave reflected from the target, and outputs the received high-frequency signal to the transceiver 2. The transceiver 2 detects the received signal sent from the antenna 1, A / D converts it, and sends it as a digital received signal to the beam former 3.

  Based on a plurality of digital reception signals sent from the transceiver 2, the beam former 3 simultaneously forms three or more reception beams and calculates a reception signal for each formed reception beam. In general, a digital beam forming (DBF) technique is used for forming the reception beam, but an analog beam forming (ABF) technique may be used.

  As shown in FIG. 4, the direct wave 12 arrives directly at the aerial line 1 from the target 11, and the indirect wave 13 arrives at the aerial line 1 from the target 11 via the ground or the sea surface 14.

FIG. 3 shows a conceptual diagram of reception beam forming. FIG. 3 shows a case where, for example, three reception beams are formed at predetermined intervals in the elevation angle θ direction. When the received beams are beam 1, beam 2, and beam 3, respectively, the calculated received signal output in each received beam is Σ ₁ , Σ ₂ , and Σ ₃ , respectively. The beam pattern at the nth (n = 1, 2, 3) elevation angle θ is defined as a function Sn (θ) of the elevation angle θ. Here, it is assumed that each beam pattern S (θ) is known, but the shape is not particularly specified. Since three received beams are formed simultaneously, the relative phase difference between the direct wave and the indirect wave is the same for all received beams, and the relative amplitude ratio is different for each received beam because each beam pattern is different from the elevation angle. Different. Therefore, the reception values Σ _{1 to} Σ ₃ in each reception beam are expressed by the following equations, respectively.

Σ ₁ = R _t1 e ^{−jφ ′} [S ₁ (α) + γS ₁ (β) e ^−jφ ]] (1)
Σ ₂ = R _t1 e ^{−jφ ′} [S ₂ (α) + γS ₂ (β) e ^−jφ ]] (2)
Σ ₃ = R _t1 e ^{−jφ ′} [S ₃ (α) + γS ₃ (β) e ^−jφ ]] (3)
α: Elevation angle of direct wave β: Elevation angle of indirect wave R _t1 : Amplitude intensity of direct wave φ ': Absolute phase of direct wave γ: Relative amplitude ratio of indirect wave to direct wave φ: Relative phase difference of indirect wave to direct wave

In the example of FIG. 3, three simultaneous multi-beams having different elevation angles are used as reception beams, and reception signal outputs calculated by the beam former 3 are Σ ₁ , Σ ₂ , and Σ ₃ . However, it is also possible to calculate a reception output signal for each of the Σ and Δ beams by performing a monopulse beam forming operation as necessary.

  The target signal detector 4 compares the reception signal of each reception beam formed by the beam former 3 with a preset target detection threshold, and determines that the reception signal equal to or higher than the threshold is the target signal. Determine and detect the target signal.

The beam selector 6 selects three received beams and received signals Σ ₁ , Σ ₂ , and Σ ₃ calculated by the received beams when the number of simultaneous multi-beams is four or more, and the angle measuring processor 5 Send to. When a target is detected by a plurality of reception beams having a plurality of elevation angles, normally, three beams including the reception beam that has detected the maximum value and the reception beams above and below it are selected. When the number of simultaneous multi-beams is three, all the received beams and received signals Σ ₁ , Σ ₂ , and Σ ₃ are selected.

  The angle measurement processor 5 performs angle measurement on the detected target to calculate the elevation angle of the direct wave. Here, the angle measurement processor 5 includes a first elevation angle calculation unit 51, a second elevation angle calculation unit 52, a parameter output unit 53, an indirect wave determination unit 54, and a direct wave elevation angle extraction unit 55, as shown in FIG. The

  The first elevation angle calculation unit 51 is means for calculating the direct wave elevation angle α and the indirect wave elevation angle β in a multipath environment based on the elevation angle estimation method of the present invention. Although details will be described later, in the first elevation angle calculation unit 51, when the influence of the indirect wave can be ignored, it is difficult to estimate the direct wave elevation angle α.

On the other hand, when the influence of the indirect wave among the reflected waves from the target can be ignored, the second elevation angle calculation unit 52 measures the angle based on the angle measurement method assuming that only the direct wave is received without receiving the indirect wave. Process. As the processing method, existing monopulse angle measurement or amplitude comparison angle measurement can be used.

The parameter output unit 53 outputs parameters necessary for calculation in the first elevation angle calculation unit 51 and the second elevation angle calculation unit 52 to the first elevation angle calculation unit 51 and the second elevation angle calculation unit 52, respectively. The first elevation angle calculation unit 51 outputs the values of the beam patterns S ₁ (θ), S ₂ (θ), and S ₃ (θ) with respect to the given value of θ. These values can be output by being stored in the parameter output unit 53 in advance or calculated by the parameter output unit 53.

The indirect wave determination unit 54 determines whether or not to obtain the direct wave elevation angle α from the calculation result in the first elevation angle calculation unit 51. That is, when two solutions (θ ₁ , θ ₂ ) related to the elevation angle are calculated by the first elevation angle calculation unit 51, the result is directly output to the wave elevation angle extraction unit 55. On the other hand, if two solutions are not calculated by the first elevation angle calculation unit 51, the process proceeds to the second elevation angle calculation unit 52.

When the first elevation angle calculation unit 51 calculates two solutions θ ₁ and θ _{2 for the} elevation angle, the direct wave elevation angle extraction unit 55 outputs the larger one of the two as the direct elevation angle α.

  Next, the first elevation angle calculation unit 51 will be described in detail with reference to the drawings. The first elevation angle calculation unit 51 in FIG. 2 includes a beam pair selection unit 511 and an elevation angle search unit 512.

  The beam pair selection unit 511 selects two sets of beam pairs formed from two reception beams from the three reception beams selected by the beam selector 6. Here, the respective beam pairs are referred to as a beam pair 1 composed of a beam 1 and a beam 2, and a beam pair 2 composed of a beam 2 and a beam 3. In addition, in the example of FIG. 3, although it is set as the beams 1, 2, and 3 toward the low elevation angle direction, how to assign a beam number is arbitrary.

The elevation angle search unit 512 refers to the received values of the two pairs of beams and the beam patterns S ₁ (θ), S ₂ (θ), and S ₃ (θ) stored in the parameter output unit 53, respectively. A search is made for θ where the value of the following equation (4) calculated from the beam pair is equal to the value of equation (5).

arg (Σ ₁ − (S ₁ (θ) / S ₂ (θ)) · Σ ₂ ) (4)
arg (Σ ₂ − (S ₂ (θ) / S ₃ (θ)) · Σ ₃ ) (5)

Equation (4) is obtained for the beam pair 1 by using the received signal Σ ₂ with the phase correction term composed of the quotients S ₁ (θ) / S ₂ (θ) of the beam patterns S ₁ (θ) and S ₂ (θ) as a weight. Is obtained by subtracting from the received signal Σ ₁ the complex phase. Similarly, for the beam pair 2, Expression (5) is a received signal weighted by a phase correction term consisting of the quotients S ₂ (θ) / S ₃ (θ) of the beam patterns S ₂ (θ) and S ₃ (θ). In this calculation, a complex phase obtained by subtracting Σ ₃ from the received signal Σ _{2 is} obtained. However, the values of S ₁ (θ) / S ₂ (θ) and S ₂ (θ) / S ₃ (θ) are uniquely determined for a given θ.

At this time, the parentheses in the expressions (4) and (5) are expressed as follows when the expressions (1) to (3) are substituted and arranged.
Σ ₁ − (S ₁ (θ) / S ₂ (θ)) · Σ ₂
= [S ₁ (α) − (S ₁ (θ) / S ₂ (θ)) · S ₂ (α)] R _t1 e ^{−jφ ′}
+ [S ₁ (β) − (S ₁ (θ) / S ₂ (θ)) · S ₂ (β)] · R _t1 γe ^{−j (φ ′ + φ)}
... (6)
Σ ₂ − (S ₂ (θ) / S ₃ (θ)) · Σ ₃
= [S ₂ (α) − (S ₂ (θ) / S ₃ (θ)) · S ₃ (α)] R _t1 e ^{−jφ ′}
+ [S ₂ (β) − (S ₂ (θ) / S ₃ (θ)) · S ₃ (β)] · R _t1 γe ^{−j (φ ′ + φ)}
... (7)

Here, at θ = α, the phase terms in the equations (6) and (7) are both e ^{−j (φ ′ + φ)} (∵first term = 0 on the right side), so that the phases of both are equal. . Similarly, even when θ = β, the phase terms in equations (6) and (7) are both e ^{−jφ ′} (the second term on the right side = 0), so the phase difference between them is zero or an integral multiple of π. Is equal to This means that when θ is equal to the direct wave elevation angle α or the indirect wave elevation angle β, the difference between the value of equation (4) and the value of equation (5) is equal to zero or an integer multiple of π.

When the relative amplitude ratio γ of the indirect wave to the direct wave is not zero, when searching for θ where the difference between the value of the equation (4) and the value of the equation (5) is equal to zero or an integer multiple of π, two solutions are obtained. I want. When the two searched solutions are θ ₁ and θ ₂ , respectively, they correspond to either the direct wave elevation angle α or the indirect wave elevation angle β. Here, as can be seen from the angular relationship between the direct wave 12 and the indirect wave 13 in the multipath environment shown in FIG. 4, the larger one of θ ₁ and θ ₂ corresponds to the direct wave elevation angle α. The wave elevation angle α can be estimated. In other words, in the case of being influenced by the indirect wave 13, it means that the elevation angle search unit 512 can obtain θ ₁ and θ ₂ corresponding to the direct wave elevation angle α and the indirect wave elevation angle β.

  On the other hand, when γ can be assumed to be zero, the second term on the right side of equations (6) and (7) is both zero, so equations (4) and (5) are always equal regardless of the value of θ. The direct wave elevation angle α or the indirect wave elevation angle β cannot be estimated. In other words, when it is not affected by the indirect wave, the elevation angle search unit 512 cannot measure the direct wave elevation angle α or the indirect wave elevation angle β.

  As an embodiment for searching for a value of θ in which the difference between Equation (4) and Equation (5) is equal to zero or an integer multiple of π, for example, a range of possible values for θ is specified, and the value of θ The ratio of the real part / imaginary part of the equation (6) and the ratio of the real part / imaginary part of the equation (7) are compared while searching for θ that has the same value. There is a method of searching for the value of θ that minimizes (8).

arg _min | arg (Σ ₁ − (S ₁ (θ) / S ₂ (θ)) · Σ ₂ )
−arg (Σ ₁ − (S ₁ (θ) / S ₃ (θ)) · Σ ₃ ) | (8)

  At the value of θ at which Equation (8) is minimized, the difference between the values calculated from Equation (6) and Equation (7) is zero.

FIG. 5 is a diagram illustrating an example of a calculation result of Expression (8). When two solutions are obtained as in the example of FIG. 5A, the two solutions θ ₁ and θ ₂ are output to the direct wave elevation angle extraction unit 55, and the larger one of them is the direct wave elevation angle α. Is output. On the other hand, when two solutions are not obtained as in the example of FIG. 5B, the process proceeds to the second elevation angle calculation unit 52. In addition, there is no restriction | limiting in particular about the search method of (theta).

  As described above, according to the radar apparatus 10 of the first embodiment, by using the angle measurement processor 5 having the first elevation angle calculation unit 51, the measurement of the direct wave elevation angle in a multipath environment can be performed in a short time. It becomes possible to carry out with accuracy. In addition, by combining the second elevation angle calculation unit 52 based on an angle measurement method assuming only a direct wave, angle measurement is possible even when there is no multipath effect.

  Next, the angle measurement method and angle measurement program of Embodiment 1 will be described.

  The angle measurement method according to the first embodiment captures the operation of the angle measurement device according to the first embodiment as a method invention. That is, the angle measuring method according to the first embodiment includes the following steps. The first elevation angle calculation unit 51 calculates a direct wave elevation angle and an indirect wave elevation angle based on the received signal. The second elevation angle calculation unit 52 calculates only the direct wave elevation angle based on the received signal. When the direct wave elevation angle output unit 50 calculates both the direct wave elevation angle and the indirect wave elevation angle by the first elevation angle calculation unit 51, the direct wave elevation angle output unit 50 outputs the direct wave elevation angle calculated by the first elevation angle calculation unit 51, and the first elevation angle A step of outputting the direct wave elevation angle calculated by the second elevation angle calculation unit 52 when both the direct wave elevation angle and the indirect wave elevation angle are not calculated by the calculation unit 51.

  In other words, as shown in FIG. 6A, the direct wave elevation angle and the indirect wave elevation angle are calculated based on the received signal (step 201), and it is determined whether both the direct wave elevation angle and the indirect wave elevation angle are calculated. If both the direct wave elevation angle and the indirect wave elevation angle are calculated, the calculated direct wave elevation angle is output (step 203). If both the direct wave elevation angle and the indirect wave elevation angle are not calculated, Only the direct wave elevation angle is calculated based on the received signal (step 204), and the calculated direct wave elevation angle is output (step 205).

  Each part of the angle measuring device according to the first embodiment may be realized by a computer. The angle measurement program according to the first embodiment causes a computer to function as each unit of the angle measurement apparatus according to the first embodiment. As shown in FIG. 6B, the computer 300 may be a general computer including a CPU 301, a ROM 302, a RAM 303, an input / output interface 304, and the like. That is, the angle measurement program according to the first embodiment includes a first elevation angle calculation unit (corresponding to the first elevation angle calculation unit 51) that calculates a direct wave elevation angle and an indirect wave elevation angle based on the received signal, and a direct wave based on the received signal. Second elevation angle calculation means for calculating only the elevation angle (corresponding to the second elevation angle calculation unit 52), and when both the direct wave elevation angle and the indirect wave elevation angle are calculated by the first elevation angle calculation means, the first elevation angle calculation means Direct wave elevation angle that outputs the calculated direct wave elevation angle, and outputs the direct wave elevation angle calculated by the second elevation angle calculation means when neither the direct wave elevation angle nor the indirect wave elevation angle is calculated by the first elevation angle calculation means This is for causing the computer 300 to function as output means (corresponding to the direct wave elevation angle output unit 50).

  The CPU 301 reads out the angle measurement program from the ROM 302 or the RAM 303, interprets it, and executes it. The angle measurement program may be recorded on a non-transitory storage medium, such as an optical disk or a semiconductor memory. In this case, the angle measurement program is read from the recording medium by the computer 300 and executed.

  The angle measurement method and angle measurement program of the first embodiment conform to other configurations of the angle measurement device of the first embodiment, the configuration of the radar device of the first embodiment, or the configuration of the radar device of the second embodiment to be described later. It may be complicated. According to the angle measurement method and angle measurement program of the first embodiment, the same effects as those of the angle measurement apparatus of the first embodiment can be obtained.

<Embodiment 2>
In the first embodiment, angle measurement processing is performed using two sets of beam pairs selected from three reception beams formed at the same time without time division. On the other hand, in the second embodiment, the angle measurement process is performed by using two reception beams to be formed simultaneously and forming the two reception beams in two steps. Even in this case, it is possible to estimate the direct wave elevation angle in a multipath environment as in the first embodiment. Hereinafter, differences from the first embodiment will be described.

  In the first embodiment, it is necessary to form at least three reception beams at the same time. Therefore, it is assumed that DBF is adopted. On the other hand, the second embodiment can be easily adopted even with ABF because only two reception beams are formed simultaneously.

  As shown in FIGS. 7 and 8, the radar apparatuses 10a and 10b according to the second embodiment include a time difference correction processor 7 that converts received signals obtained at different times into received signals obtained at the same time. It is further provided with the feature. FIG. 7 is a block diagram showing the radar apparatus 10a when DBF is employed in the second embodiment. Compared with the block diagram showing the radar apparatus of the first embodiment shown in FIG. 1, it can be seen that a time difference correction processor 7 is newly provided. These operations will be described later.

  On the other hand, FIG. 8 shows a block diagram showing the radar apparatus 10b when ABF is adopted. A method for obtaining a received signal required for performing target detection and angle measurement processing differs between when ABF is employed and when DBF is employed. Therefore, the radar apparatus 10b of FIG. 8 differs from that of FIG. 7 in that the configuration of the transmitter / receiver 2b is different from that of FIG. 7, and the beam former in the signal processor 8b is not necessary. The other configuration of the radar apparatus 10b of FIG. 8 is the same as when the DBF shown in FIG. 7 is adopted.

  Next, the operation in the second embodiment will be described in detail. FIG. 9 shows a conceptual diagram of the reception beam. At different times t1 and t2, two received beams are formed at predetermined intervals in the elevation direction. At this time, one of the two reception beams formed at time t1 and one of the two reception beams formed at time t2 have the same beam shape and the same elevation angle direction. It is. This received beam is referred to as beam 2, the remaining received beam formed at time t1 is referred to as beam 1, and the remaining received beam formed at time t2 is referred to as beam 3. It is assumed that the shapes of the beam 1 and the beam 2 are different.

Here, the received signal detected by beam 1 at time t1 is Σ ₁ , the received signal detected by beam 2 is Σ ₂ , the received signal detected by beam 2 at time t 2 is Σ ₂ ′, and beam 3 is used. Let the detected received signal be Σ ₃ '. However, the case without the dash symbol (') means the received signal at time t1, and the case with the dash symbol (') means the received signal at time t2. At this time, although the signal intensity and absolute phase of the direct wave at times t1 and t2 are different, it is considered that the relative amplitude ratio and the relative phase difference between the direct wave and the indirect wave do not change. Therefore, each received signal is represented by the following equation.

Σ ₁ = R _t1 e ^−jφ′t1 [S ₁ (α) + γS ₁ (β) e ^−jφ ]] (9)
Σ ₂ = R _t1 e ^−jφ′t1 [S ₂ (α) + γS ₂ (β) e ^−jφ ]] (10)
Σ ₂ ′ = R _t2 e ^−jφ′t2 [S ₂ (α) + γS ₂ (β) e ^−jφ ]] (11)
Σ ₃ ′ = R _t2 e ^−jφ′t2 [S ₃ (α) + γS ₃ (β) e ^−jφ ]] (12)
α: Elevation angle of direct wave β: Elevation angle of indirect wave R _t1 : Amplitude intensity of direct wave at time t1 R _t2 : Amplitude intensity of direct wave at time t2 φ't1: Absolute phase of direct wave at time t1 φ't2: Absolute phase of direct wave at time t2 γ: Relative amplitude ratio of indirect wave to direct wave φ: Relative phase difference of indirect wave to direct wave

In the second embodiment, a reception signal necessary for angle measurement processing is sent to the target detector 4. The reception signals necessary for the angle measurement processing include at least the above-mentioned Σ ₁ , Σ ₂ , Σ ₂ ′, and Σ ₃ ′. Further, when the second elevation angle calculation unit 52 adopts the monopulse method, reception signals for the Σ and Δ beams obtained by the monopulse beam forming process are further included. When the target is detected by the target detector 4, the received signal is output to the beam selector 6.

Here, in order to perform angle measurement processing by the angle measurement processor 5, reception signals detected by three reception beams at the same time are required. Therefore, the beam selector 6 and the time difference correction processor 7 calculate the received signal Σ ₃ detected by the beam 3 at time t1.

The beam selector 6 selects Σ ₂ , Σ ₂ ′, Σ ₃ ′ necessary for calculating the received signal Σ ₃ , sends it to the time difference correction processor 7, and measures Σ ₁ , Σ ₂ . Send to processor 5.

The time difference correction processor 7 performs the following calculation.
(Σ ₂ / Σ ₂ ') ・ Σ ₃ '
= (R _t1 e ^−jφ′t1 / R _t2 e ^−jφ′t2 ) · R _t2 e ^−jφ′t2 [S ₃ (α) + γS ₃ (β) e ^−jφ ]
= R _t1 e ^−jφ′t1 [S ₃ (α) + γS ₃ (β) e ^−jφ ]] (13)

Here, if φ′t1 on the right side of equation (13) is rewritten as φ ′, it matches the right side of equation (3), so the right side of equation (13) is obtained when detected by beam 3 at time t1. It can be seen that the received signal Σ ₃ is considered to be generated. That is, the time difference correction processor 7 calculates the received signal Σ ₃ detected by the beam 3 at time t 1 from the received signals Σ ₂ , Σ ₂ ′, Σ ₃ ′. The calculated received signal Σ ₃ is sent to the angle measurement processor 5.

As a result, the angle measurement processor 5 receives the reception signals Σ ₁ , Σ ₂ , and Σ ₃ obtained by the three reception beams at the same time t1. Specifically, the received signals Σ ₁ , Σ ₂ , and Σ ₃ are sent to the first elevation angle calculation unit 51 in the angle measuring processor 5 shown in FIG. The subsequent processing is the same as the processing described in the first embodiment.

  As described above, by providing the beam selector 6 and the time difference correction processor 7, angle measurement processing in a multipath environment can be performed with the same accuracy as in the first embodiment even when two reception beams are formed in two steps. Can be performed. In the second embodiment, even ABF can be easily adopted, so that the cost for the apparatus can be reduced.

  Next, the effects of the present invention will be summarized. (1) By calculating the direct wave elevation angle analytically in consideration of not only direct waves but also indirect waves in the first elevation angle calculation unit, highly accurate angle measurement is possible in a multipath environment. (2) In addition to the first elevation angle calculation unit, the second elevation angle calculation unit that performs angle measurement processing assuming the case of only direct waves is also used, so angle measurement is possible regardless of the presence or absence of multipath effects. It becomes. (3) Since the reflected wave from the beam radiated continuously in one scan is used, the angle can be measured in a short time. (4) By configuring a beam former capable of forming three or more received beams, it is possible to perform more accurate angle measurement. (5) By providing a time difference correction processor, the angle can be measured even when the number of received beams is two and scanning is performed twice to form a received beam, and an ABF (analog beam forming) technique is provided. By configuring the reception beamformer based on the above, it is possible to reduce the cost of hardware.

  Although the present invention has been described with reference to the above embodiments, the present invention is not limited to the above embodiments. Various changes that can be understood by those skilled in the art can be made to the configuration and details of the present invention. Further, the present invention includes a combination of some or all of the configurations of the above-described embodiments as appropriate.

  Although a part or all of the above embodiments can be described as the following supplementary notes, the present invention is not limited to the following configurations.

[Supplementary Note 1] A first elevation angle calculation unit that calculates a direct wave elevation angle and an indirect wave elevation angle based on a received signal;
A second elevation angle calculation unit that calculates only the direct wave elevation angle based on the received signal;
When both the direct wave elevation angle and the indirect wave elevation angle are calculated by the first elevation angle calculation unit, the direct elevation angle calculated by the first elevation angle calculation unit is output, and the first elevation angle calculation unit outputs the direct wave elevation angle. If both the direct wave elevation angle and the indirect wave elevation angle are not calculated, a direct wave elevation angle output unit that outputs the direct wave elevation angle calculated by the second elevation angle calculation unit;
An angle measuring device comprising:

[Appendix 2] The angle measuring device according to Appendix 1,
The three receive beams are beam 1, beam 2, and beam 3,
The received signal for the beam 1 is a received signal 1;
The received signal for the beam 2 is a received signal 2;
The received signal for the beam 3 is a received signal 3,
Suppose that the received signal 1 includes a beam pattern 1 that is a function of elevation angle;
Suppose that the received signal 2 includes a beam pattern 2 that is a function of elevation angle;
When the received signal 3 includes a beam pattern 3 that is a function of elevation angle,
The first elevation angle calculation unit includes a beam pair selection unit and an elevation angle search unit,
The beam pair selection unit selects a beam pair 1 composed of the beam 1 and the beam 2 and a beam pair 2 composed of the beam 2 and the beam 3 from the three reception beams,
The elevation angle search unit calculates a complex phase obtained by subtracting the received signal 2 from the received signal 1 with respect to the beam pair 1 by weighting a phase correction term consisting of a quotient of the beam pattern 1 and the beam pattern 2. Calculate the phase of a complex number obtained by subtracting the received signal 3 from the received signal 2 with the phase correction term consisting of the quotient of the beam pattern 2 and the beam pattern 3 as a weight for the beam pair 2, Search for an elevation angle that satisfies the condition that the phase difference is equal to zero or an integer multiple of 180 degrees,
An angle measuring device characterized by that.

[Appendix 3] The angle measuring device according to Appendix 2,
The direct wave elevation angle output unit includes an indirect wave determination unit and a direct wave elevation angle extraction unit,
The indirect wave determination unit determines to use the calculation result by the first elevation angle calculation unit when two elevation angles satisfying the condition are obtained by the first elevation angle calculation unit, and the first elevation angle calculation unit When two elevation angles satisfying the above condition are not obtained, a determination is made using the calculation result by the second elevation angle calculation unit,
The direct wave elevation angle extraction unit outputs, as the direct wave elevation angle, the larger one of the two elevation angles satisfying the condition when the indirect wave determination unit determines to use the calculation result of the first elevation angle calculation unit. And
The second elevation angle calculation unit outputs the calculation result by the second elevation angle calculation unit as the direct wave elevation angle when the indirect wave determination unit determines to use the calculation result by the second elevation angle calculation unit.
An angle measuring device characterized by that.

[Appendix 4] The angle measuring device according to any one of Appendixes 1 to 3,
A parameter output unit for outputting parameters necessary for the calculation to the first elevation angle calculation unit and the second elevation angle calculation unit;
An angle measuring device further comprising the angle measuring device.

[Appendix 5] An antenna that radiates a transmission radio wave for radar and receives a reflected wave from a target corresponding to the transmission radio wave;
A transceiver for outputting a high-frequency signal to the antenna and detecting a signal received by the antenna;
A beam former that forms a plurality of reception beams from a signal after reception processing by the transceiver and extracts a reception signal in each reception beam formed;
A target detector for detecting a target based on a received signal in each beam formed by the beam former;
When the target is detected by the target detector, the reception beam necessary for angle measurement processing is selected from the reception signals formed by the beam former, and the reception signal obtained by the reception beam is selected. Or a beam selector to be formed;
The angle measuring device according to any one of appendices 1 to 4, which performs angle measurement processing based on the selected reception beam and a reception signal calculated by the reception beam;
A radar apparatus comprising:

[Appendix 6] The radar apparatus according to Appendix 5,
The beam former forms all the reception signals necessary for the angle measurement processing at the same time, and is necessary for the processing by the three or more reception beams and the second elevation angle calculation unit required for the processing by the first elevation angle calculation unit. Form a receive beam,
The beam selector selects three reception beams required for processing in the first elevation angle calculation unit;
Radar apparatus characterized by the above.

[Appendix 7] The radar apparatus according to Appendix 5,
It further comprises a time difference correction processor that converts received signals obtained at different times into received signals obtained at the same time,
Radar apparatus characterized by the above.

[Appendix 8] The first elevation angle calculation unit calculates a direct wave elevation angle and an indirect wave elevation angle based on the received signal,
A second elevation angle calculator calculates only the direct wave elevation angle based on the received signal;
The direct wave elevation angle output unit outputs the direct wave elevation angle calculated by the first elevation angle calculation unit when both the direct wave elevation angle and the indirect wave elevation angle are calculated by the first elevation angle calculation unit, When both the direct wave elevation angle and the indirect wave elevation angle are not calculated by the first elevation angle calculation unit, the direct wave elevation angle calculated by the second elevation angle calculation unit is output.
Angle measuring method characterized by that.

[Supplementary Note 9] First elevation angle calculating means for calculating a direct wave elevation angle and an indirect wave elevation angle based on a received signal,
Second elevation angle calculating means for calculating only the direct wave elevation angle based on the received signal; and
When both the direct wave elevation angle and the indirect wave elevation angle are calculated by the first elevation angle calculation means, the direct wave elevation angle calculated by the first elevation angle calculation means is output, and the first elevation angle calculation means outputs the direct wave elevation angle. Direct wave elevation angle output means for outputting the direct wave elevation angle calculated by the second elevation angle calculation means when both the direct wave elevation angle and the indirect wave elevation angle are not calculated,
Angle measurement program to make the computer function as.

[Supplementary Note 11] A first elevation angle calculation unit that calculates a direct wave elevation angle and an indirect wave elevation angle in a multipath environment using reception signals obtained by three different beams at the same time;
A second elevation angle calculation unit that performs angle measurement processing assuming only a direct wave;
A parameter output unit for outputting parameters necessary for calculation in the first elevation angle calculation unit and the second elevation angle calculation unit to the first elevation angle calculation unit and the second elevation angle calculation unit, respectively;
An indirect wave determination unit that determines whether to use the calculation result in the first elevation angle calculation unit when estimating the direct wave elevation angle;
A direct wave elevation angle extraction unit for obtaining the direct wave elevation angle using a calculation result in the first elevation angle calculation unit,
The first elevation angle calculation unit includes:
Select two beam pairs, beam pair 1 consisting of beam 1 and beam 2 and beam pair 2 consisting of beam 2 and beam 3 from the three different beams used to determine the received signal. A beam pair selection unit to perform,
Using the elevation angle as a parameter, the received signal 2 weighted by the phase correction term consisting of the quotients of the beam pattern 1 and the beam pattern 2 and the complex phase obtained by subtracting the received signal 1 from the quotient of the beam pattern 1 and the beam pattern 3 An elevation angle search unit for calculating a complex phase obtained by subtracting the received signal 3 with the phase correction term as a weight from the received signal 1 and searching for an elevation angle at which the phase difference between them is equal to zero or an integer multiple of 180 degrees; Have
When two elevation angles satisfying the above condition are obtained in the first elevation angle calculation unit, the indirect wave determination unit determines to use the calculation result in the first elevation angle calculation unit, and the direct wave elevation angle extraction unit Of the two solutions for elevation angle, the one with the larger value is directly output as the wave elevation angle,
When two elevation angles satisfying the above conditions are not obtained by the first elevation angle calculation unit, the indirect wave determination unit determines to use the calculation result of the second elevation angle calculation unit, and calculates the second elevation angle. Calculate the wave elevation angle directly at the unit and output the value as the wave elevation angle directly.
An angle measuring device characterized by that.

[Supplementary Note 12] An antenna that radiates a transmission radio wave for radar and receives a reflected wave from a target corresponding to the transmission radio wave;
A reception signal processing unit that outputs a high-frequency signal to the antenna and detects a reception signal sent from the antenna, forms a multi-beam from the signal after reception processing, and extracts a digital reception signal in each formed beam;
A target signal detector that performs target detection based on the received signal in each beam formed by the reception processing unit;
A beam selector that selects a reception beam necessary for angle measurement processing from among the reception signals formed by the beam former when a target is detected, and selects or forms a reception signal obtained by the reception beam When,
The angle measuring device according to appendix 11, which performs angle measurement processing based on the selected reception beam and a reception signal calculated by the reception beam;
A radar apparatus comprising:

[Supplementary Note 13] In the radar apparatus according to Supplementary Note 12,
All the received signals necessary for angle measurement processing are formed at the same time,
Forming at least three received beams required for processing in the first elevation angle calculation unit and beams required for processing in the second elevation angle calculation unit by the reception beam former;
A radar apparatus, comprising: a beam selector that selects three multi-beams necessary for processing in the first elevation angle calculation unit as the beam selector.

[Supplementary Note 14] In the radar apparatus according to Supplementary Note 12,
The number of reception beams to be formed at the same time is two, and scanning is performed in two times to overlap one beam to form a reception beam,
A time difference correction processor for converting a received signal obtained at a different time in the beam selector to a signal received at the same time;
Time difference correction processing is performed based on reception signals obtained by the same reception beam pattern at different times.
Radar apparatus characterized by the above.

  INDUSTRIAL APPLICABILITY The present invention can be used for an angle measurement technique for detecting elevation angle information of a target in a multipath environment where there is a reflected wave from the ground, the sea surface, or the like, for example, a radar apparatus that detects a target.

DESCRIPTION OF SYMBOLS 1 Antenna 2, 2b Transmitter / receiver 3 Beamformer 4 Target detector 5 Angle measuring processor (angle measuring device)
6 Beam selector 7 Time difference correction processor 8, 8a, 8b Signal processor 10, 10a, 10b Radar device 11 Target 12 Direct wave 13 Indirect wave 14 Ground or sea surface 50 Direct wave elevation angle output unit 51 First elevation angle calculation unit 52 Second elevation angle calculation unit 53 Parameter output unit 54 Indirect wave determination unit 55 Direct wave elevation angle extraction unit 511 Beam pair selection unit 512 Elevation angle search unit 100 Circular locus 101a, 101b, 101c, 101d, 101e drawn by Δ / Σ on the complex plane , 101f Observation value 102 Complex division means 103 First circle center calculation means 104 Angle conversion means 300 Computer 301 CPU
302 ROM
303 RAM
304 I / O interface

Claims (8)

A first elevation angle calculation unit for calculating a direct wave elevation angle and an indirect wave elevation angle based on a received signal;
A second elevation angle calculation unit that calculates only the direct wave elevation angle based on the received signal;
When both the direct wave elevation angle and the indirect wave elevation angle are calculated by the first elevation angle calculation unit, the direct elevation angle calculated by the first elevation angle calculation unit is output, and the first elevation angle calculation unit outputs the direct wave elevation angle. If both the direct wave elevation angle and the indirect wave elevation angle are not calculated, a direct wave elevation angle output unit that outputs the direct wave elevation angle calculated by the second elevation angle calculation unit;
With
The three receive beams are beam 1, beam 2, and beam 3,
The received signal for the beam 1 is a received signal 1;
The received signal for the beam 2 is a received signal 2;
The received signal for the beam 3 is a received signal 3,
Suppose that the received signal 1 includes a beam pattern 1 that is a function of elevation angle;
Suppose that the received signal 2 includes a beam pattern 2 that is a function of elevation angle;
When the received signal 3 includes a beam pattern 3 that is a function of elevation angle,
The first elevation angle calculation unit includes a beam pair selection unit and an elevation angle search unit,
The beam pair selection unit selects a beam pair 1 composed of the beam 1 and the beam 2 and a beam pair 2 composed of the beam 2 and the beam 3 from the three reception beams,
The elevation angle search unit calculates a complex phase obtained by subtracting the received signal 2 from the received signal 1 with respect to the beam pair 1 by weighting a phase correction term consisting of a quotient of the beam pattern 1 and the beam pattern 2. Calculate the phase of a complex number obtained by subtracting the received signal 3 from the received signal 2 with the phase correction term consisting of the quotient of the beam pattern 2 and the beam pattern 3 as a weight for the beam pair 2, Search for an elevation angle that satisfies the condition that the phase difference is equal to zero or an integer multiple of 180 degrees,
An angle measuring device characterized by that. The angle measuring device according to claim 1 ,
The direct wave elevation angle output unit includes an indirect wave determination unit and a direct wave elevation angle extraction unit,
The indirect wave determination unit determines to use the calculation result by the first elevation angle calculation unit when two elevation angles satisfying the condition are obtained by the first elevation angle calculation unit, and the first elevation angle calculation unit When two elevation angles satisfying the above condition are not obtained, a determination is made using the calculation result by the second elevation angle calculation unit,
The direct wave elevation angle extraction unit outputs, as the direct wave elevation angle, the larger one of the two elevation angles satisfying the condition when the indirect wave determination unit determines to use the calculation result of the first elevation angle calculation unit. And
The second elevation angle calculation unit outputs the calculation result by the second elevation angle calculation unit as the direct wave elevation angle when the indirect wave determination unit determines to use the calculation result by the second elevation angle calculation unit.
An angle measuring device characterized by that. The angle measuring device according to claim 1 or 2 ,
A parameter output unit for outputting parameters necessary for the calculation to the first elevation angle calculation unit and the second elevation angle calculation unit;
An angle measuring device further comprising the angle measuring device. An antenna that radiates a transmission radio wave for radar and receives a reflected wave from a target corresponding to the transmission radio wave,
A transceiver for outputting a high-frequency signal to the antenna and detecting a signal received by the antenna;
A beam former that forms a plurality of reception beams from a signal after reception processing by the transceiver and extracts a reception signal in each reception beam formed;
A target detector for detecting a target based on a received signal in each beam formed by the beam former;
When the target is detected by the target detector, the reception beam necessary for angle measurement processing is selected from the reception signals formed by the beam former, and the reception signal obtained by the reception beam is selected. Or a beam selector to be formed;
The angle measuring device according to any one of claims 1 to 3, wherein an angle measuring process is performed based on the selected received beam and a received signal calculated by the received beam.
A radar apparatus comprising: The radar device according to claim 4 ,
The beam former forms all the reception signals necessary for the angle measurement processing at the same time, and is necessary for the processing by the three or more reception beams and the second elevation angle calculation unit required for the processing by the first elevation angle calculation unit. Form a receive beam,
The beam selector selects three reception beams required for processing in the first elevation angle calculation unit;
Radar apparatus characterized by the above. The radar device according to claim 4 ,
It further comprises a time difference correction processor that converts received signals obtained at different times into received signals obtained at the same time,
Radar apparatus characterized by the above. A first elevation angle calculating step for calculating a direct wave elevation angle and an indirect wave elevation angle based on the received signal ;
A second elevation angle calculating step of calculating only the direct wave elevation angle based on the received signal ;
When both the direct wave elevation angle and the indirect wave elevation angle are calculated in the first elevation angle calculation step, the direct wave elevation angle calculated in the first elevation angle calculation step is output, and in the first elevation angle calculation step, the A direct wave elevation output step for outputting the direct wave elevation angle calculated in the second elevation angle calculation step when both the direct wave elevation angle and the indirect wave elevation angle are not calculated ;
Including
The three receive beams are beam 1, beam 2, and beam 3,
The received signal for the beam 1 is a received signal 1;
The received signal for the beam 2 is a received signal 2;
The received signal for the beam 3 is a received signal 3,
Suppose that the received signal 1 includes a beam pattern 1 that is a function of elevation angle;
Suppose that the received signal 2 includes a beam pattern 2 that is a function of elevation angle;
When the received signal 3 includes a beam pattern 3 that is a function of elevation angle,
The first elevation angle calculating step includes a beam pair selection step and an elevation angle search step,
In the beam pair selection step, a beam pair 1 consisting of the beam 1 and the beam 2 and a beam pair 2 consisting of the beam 2 and the beam 3 are selected from the three reception beams,
In the elevation angle search step, a complex phase obtained by subtracting from the received signal 1 the received signal 2 weighted by a phase correction term consisting of a quotient of the beam pattern 1 and the beam pattern 2 for the beam pair 1. Calculate the phase of a complex number obtained by subtracting the received signal 3 from the received signal 2 with the phase correction term consisting of the quotient of the beam pattern 2 and the beam pattern 3 as a weight for the beam pair 2, Search for an elevation angle that satisfies the condition that the phase difference is equal to zero or an integer multiple of 180 degrees,
Angle measuring method characterized by that. First elevation angle calculating means for calculating a direct wave elevation angle and an indirect wave elevation angle based on a received signal;
Second elevation angle calculating means for calculating only the direct wave elevation angle based on the received signal; and
When both the direct wave elevation angle and the indirect wave elevation angle are calculated by the first elevation angle calculation means, the direct wave elevation angle calculated by the first elevation angle calculation means is output, and the first elevation angle calculation means outputs the direct wave elevation angle. Direct wave elevation angle output means for outputting the direct wave elevation angle calculated by the second elevation angle calculation means when both the direct wave elevation angle and the indirect wave elevation angle are not calculated,
A angle measuring program for causing a computer to function as,
The three receive beams are beam 1, beam 2, and beam 3,
The received signal for the beam 1 is a received signal 1;
The received signal for the beam 2 is a received signal 2;
The received signal for the beam 3 is a received signal 3,
Suppose that the received signal 1 includes a beam pattern 1 that is a function of elevation angle;
Suppose that the received signal 2 includes a beam pattern 2 that is a function of elevation angle;
When the received signal 3 includes a beam pattern 3 that is a function of elevation angle,
The first elevation angle calculation means includes a beam pair selection means and an elevation angle search means,
The beam pair selection means selects a beam pair 1 consisting of the beam 1 and the beam 2 and a beam pair 2 consisting of the beam 2 and the beam 3 from the three reception beams,
The elevation angle search means calculates a complex phase obtained by subtracting from the received signal 1 the received signal 2 weighted by a phase correction term consisting of a quotient of the beam pattern 1 and the beam pattern 2 for the beam pair 1. Calculate the phase of a complex number obtained by subtracting the received signal 3 from the received signal 2 with the phase correction term consisting of the quotient of the beam pattern 2 and the beam pattern 3 as a weight for the beam pair 2, Search for an elevation angle that satisfies the condition that the phase difference is equal to zero or an integer multiple of 180 degrees,
Angle measuring program characterized by that.

Images