JP6044116B2 - Radar apparatus, angle measuring method and program - Google Patents

Description

  The present invention relates to a radar device that detects a target, and more particularly, to a multipath presence / absence determination technology that determines whether or not a reflected wave from the ground or the sea surface is present in a multipath environment when detecting elevation angle information of a target. .

  Radar devices generally emit radio waves into space and receive radio waves reflected by the target to detect the presence of the target and observe the position of the target, the motion state of the target, and the like.

  In the radar apparatus, a transmission beam, which is a radio wave, is emitted from an aerial into space, reflected by a target, then received again by the aerial, and output from the aerial to a receiver or the like as a radar reception signal. The radar reception signal is A / D converted at a predetermined sampling interval to become a digital reception signal. 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 greater than the threshold value is detected as a target signal indicating the presence of the target. Also, the radar apparatus obtains target distance information 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 of the radar apparatus.

  The radar apparatus can obtain target azimuth information by changing the azimuth of the transmission beam, obtaining radar reception signals having different azimuths, and performing azimuth measurement processing.

  Further, the radar apparatus emits a plurality of transmission beams having different elevation angles, receives reflected signals from the same target, and performs elevation angle measurement processing using the amplitude difference and phase difference of reception signals having different elevation angles. Altitude information can be obtained.

  Sending a radio wave to the space to be observed is called scanning, and the radar apparatus can acquire target information continuously at a predetermined interval by repeatedly performing the scanning operation.

  For example, an amplitude comparison method and a monopulse method are known as representative angle measuring methods.

  In the amplitude comparison method, the radar apparatus detects a target with a plurality of reception beams formed continuously in the elevation angle direction, and the ratio of the target elevation angle (target elevation angle) and the amplitude or phase of the target signal in each reception beam is constant. The target elevation angle is obtained using the relationship.

  In the amplitude comparison method, Patent Document 1 describes that the angle measurement accuracy deteriorates when there are multipaths.

  FIG. 23 shows a state in which the antenna 1 of the radar apparatus receives a multipath wave that is a reflected wave from the ground or the sea surface in addition to the direct wave from the target T.

  The phase relationship between the direct wave and the multipath wave input to the antenna 1 depends on the distance to the target T and the like. When there is a multipath, since the combined wave of the direct wave and the multipath wave is detected as the target signal, the above relationship is not established, and the angle measurement accuracy deteriorates.

  In the monopulse system, the radar apparatus simultaneously forms two types of received beam patterns of Σ (sum) beam and Δ (difference) beam, and the sum / division division signal Δ / Σ draws a constant characteristic curve with respect to the target elevation angle. The arrival angle of the direct wave is obtained using the relationship.

  Non-Patent Document 1 and Patent Document 2 describe that the angle measurement accuracy deteriorates even when the monopulse method has multipath, as in the case of the amplitude comparison method.

  Various methods are known as a multipath countermeasure.

  There is a diversity method as a general multipath countermeasure. The diversity method reduces the influence of multipath by using a plurality of frequencies and antennas to acquire and process a plurality of data having different influences of multipath.

  In addition to the diversity method, as a measure particularly in the amplitude comparison method, a method of setting (off-bore) the directional center of the received beam by shifting upward is known. With this off-bore method, the received power of the multipath wave from the ground or the sea surface is reduced and the influence is reduced.

  In addition, as a countermeasure in the monopulse method, Patent Document 3 discloses an angle measurement method for estimating the arrival angles of direct waves and multipath waves in order to improve angle measurement accuracy.

JP 2006-0783342 A JP 2000-28704 A JP 2002-243824 A

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

  If the above multipath countermeasure is performed on a received beam outside the multipath environment, the following problem occurs.

  When the off-bore method is adopted as a multipath countermeasure, the received signal from a target with a low elevation angle also becomes weak, and there is a problem that target detection becomes difficult as compared with the case without off-bore.

  In the angle measuring method described in Patent Document 3, there is a problem that the calculation load increases because the arrival angles of the direct wave and the multipath wave are estimated.

  In the frequency diversity method, since signals of a plurality of frequencies are transmitted and received, a radar apparatus that cannot transmit at a plurality of frequencies at the same time needs to transmit a plurality of times in the same direction, resulting in a problem that the data rate is lowered.

  An object of the present invention is to provide a radar apparatus, an angle measuring method, and a program that can solve the above-described problems.

The radar apparatus of the present invention
A beam forming unit that forms a plurality of reception beams having different elevation angles and extracts a reception signal in each reception beam;
A target detection unit for detecting a target signal indicating the presence of a target based on a reception signal in each reception beam;
A multipath presence / absence determination unit that determines presence / absence of multipath based on reception signals in a plurality of selection reception beams including a reception beam in which the target signal is detected among the plurality of reception beams;
When it is determined that there is no multipath, a first angle measurement process without multipath countermeasures is performed, and when it is determined that there is multipath, a second measurement with multipath countermeasures is performed. A processing unit for performing corner processing,
The multipath presence determination unit
A phase difference calculation unit for calculating a phase difference of reception signals in two specific reception beams specified from the plurality of selection reception beams;
A phase difference prediction unit that predicts a phase difference between the reception signals in the two specific reception beams in a situation where there is no multipath;
Based on the difference between the predicted results of the phase difference prediction unit and the calculation result of the phase difference calculating section, seen including and a determination unit for determining presence or absence of the multipath,
The beam forming unit forms, as the plurality of reception beams, two or more simultaneous Σ beams having different elevation angles including the simultaneous Σ beam in which the target signal is detected,
The multipath presence / absence determining unit further includes an output unit that outputs parameters necessary for predicting the phase difference to the phase difference predicting unit,
The phase difference prediction unit predicts the phase difference based on an elevation angle of the two specific reception beams and the parameter .

An angle measuring method of the present invention is an angle measuring method in a radar apparatus,
A beam forming step of forming a plurality of reception beams having different elevation angles and extracting a reception signal in each reception beam;
A target detection step of detecting a target signal indicating the presence of a target based on the received signal in each of the received beams;
A multipath presence / absence determination step for determining presence / absence of multipath based on reception signals in a plurality of selection reception beams including the reception beam in which the target signal is detected among the plurality of reception beams;
When it is determined that there is no multipath, a first angle measurement process without multipath countermeasures is performed, and when it is determined that there is multipath, a second measurement with multipath countermeasures is performed. Processing steps for performing corner processing,
The multipath presence determination step includes
A phase difference calculating step of calculating a phase difference of received signals in two specific received beams specified from the plurality of selected received beams;
A phase difference prediction step for predicting a phase difference between the reception signals in the two specific reception beams in a situation where there is no multipath;
Based on the difference between the predicted results of the phase difference between the calculation result of the phase difference, seen including and a determination step of determining whether the multipath,
In the beam forming step, as the plurality of reception beams, two or more simultaneous Σ beams having different elevation angles including the simultaneous Σ beam in which the target signal is detected are formed,
In the multipath presence / absence determination step, a parameter required for predicting the phase difference is further output to the phase difference prediction unit,
In the phase difference prediction step, the phase difference is predicted based on the elevation angle of the two specific reception beams and the parameter .

The program of the present invention is stored in a computer.
A beam forming procedure for forming a plurality of reception beams having different elevation angles and extracting a reception signal in each reception beam;
A target detection procedure for detecting a target signal indicating the presence of a target based on a received signal in each of the received beams;
A multipath presence / absence determination procedure for determining presence / absence of multipath based on reception signals in a plurality of selective reception beams including a reception beam in which the target signal is detected among the plurality of reception beams;
When it is determined that there is no multipath, a first angle measurement process without multipath countermeasures is performed, and when it is determined that there is multipath, a second measurement with multipath countermeasures is performed. A processing procedure for performing corner processing, and
The multipath presence determination procedure includes:
A phase difference calculation procedure for calculating a phase difference of reception signals in two specific reception beams specified from the plurality of selection reception beams;
A phase difference prediction procedure for predicting a phase difference of each received signal in the two specific received beams in the absence of the multipath;
Based on the difference between the predicted results of the phase difference between the calculation result of the phase difference, seen including and a determination procedure for determining the presence or absence of the multipath,
In the beam forming procedure, as the plurality of received beams, two or more simultaneous Σ beams having different elevation angles including the simultaneous Σ beam in which the target signal is detected are formed,
In the multipath presence / absence determination procedure, further, a parameter necessary for predicting the phase difference is output to the phase difference prediction unit,
In the phase difference prediction procedure, the phase difference is predicted based on the elevation angle of the two specific reception beams and the parameter .

  According to the present invention, it is possible to avoid problems caused by multipath countermeasures in the absence of multipath.

It is a block diagram which shows the structure of the radar apparatus which concerns on Embodiment 1 of this invention. It is a block diagram which shows the structure of the multipath presence determination device in Embodiment 1 of this invention. It is a figure which shows the state from which the electromagnetic wave came from the direction of angle (alpha) with respect to the linear array antenna front direction. FIG. 6 is a diagram illustrating a reception signal Σ ₁ and a reception signal Σ ₂ obtained when there is no multipath in Embodiment 1 of the present invention in a complex plane. It is a figure which shows the relationship between the phase of the received signal obtained when there is no multipath in Embodiment 1 of this invention, and the nose elevation angle of the received beam used when obtaining the received signal. FIG. 6 is a diagram illustrating a reception signal Σ ₁ and a reception signal Σ ₂ obtained when there is a multipath in Embodiment 1 of the present invention in a complex plane. It is a figure which shows the relationship between the phase of the received signal obtained when there exists multipath in Embodiment 1 of this invention, and the nose elevation angle of the received beam used when obtaining the received signal. Is a diagram illustrating the difference between the nose elevation of the two beams obtained when the multipath does not exist, the relationship between the phase difference of the received signal sigma ₁ and the received signal sigma ₂ in the first embodiment of the present invention. It illustrates two and the difference of the nose elevation of the beam obtained when multipath is present, the relationship between the phase difference of the received signal sigma ₁ and the received signal sigma ₂ in the first embodiment of the present invention. It is a block diagram which shows the structure of the multipath presence determination device in Embodiment 2 of this invention. It is a figure which shows the relationship between the beam elevation angle obtained when there is no multipath in Embodiment 2 of this invention, and the phase of a received signal. It is a figure which shows the relationship between the beam elevation angle obtained when there exists multipath in Embodiment 2 of this invention, and the phase of a received signal. It is the figure explaining the processing content in the correction value calculation part 66 in Embodiment 2 of this invention using the relationship between the beam elevation angle and the phase of a received signal. It is a figure which shows the relationship between the phase of the received signal obtained when there is no multipath in Embodiment 2 of this invention, and the nose elevation angle of the received beam used when obtaining the received signal. It is a figure which shows the relationship between the phase of the received signal obtained when there exists multipath in Embodiment 2 of this invention, and the nose elevation angle of the received beam used when obtaining the received signal. It is a block diagram which shows the structure of the multipath presence determination device in Embodiment 3 of this invention. It is the figure which showed the received signal (SIGMA) and the received signal (DELTA) obtained when there is no multipath in Embodiment 3 of this invention on a complex plane. It is the figure which showed the received signal (SIGMA) and the received signal (DELTA) obtained when there exists multipath in Embodiment 3 of this invention on a complex plane. It is a block diagram which shows the structure of the radar apparatus which concerns on Embodiment 4 of this invention. In Embodiment 1 of this invention, it is a figure which shows the example from which the phase difference of the received signals (SIGMA) ₁ and (SIGMA) ₂ obtained when there exists multipath becomes the same value as phase difference prediction value (phi) ₀ . In Embodiment 3 of this invention, it is a figure which shows the example from which the phase difference of the received signal (SIGMA) obtained when there exists multipath and the received signal (DELTA) becomes the same value as phase difference prediction value (phi) ₀ . It is a block diagram which shows the structure of the radar apparatus which concerns on Embodiment 5 of this invention. It is a figure which shows the mode of a multipass.

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

<Embodiment 1>
FIG. 1 is a block diagram illustrating a radar apparatus 10 according to the first embodiment.

  In FIG. 1, a radar apparatus 10 according to the first embodiment includes an antenna 1, a transmission / reception unit 2, a beam former 3, a target signal detector 4, a beam selector 5, a multipath presence / absence determiner 6, a switch 7, and a multipath. An external angle measurement processor 81 and a multipath internal angle measurement processor 82 are included. The switching unit 7, the multipath outside angle measurement processor 81, and the multipath angle measurement processor 82 are included in the processing unit A. The beam processor 3, the target signal detector 4, the beam selector 5, the multipath presence / absence determiner 6, and the processing unit A are included in the signal processor B.

  The transmission / reception unit 2 outputs a transmission wave signal (for example, a high frequency signal) to the antenna 1.

  The antenna 1 includes a plurality of antennas, and radiates radio waves according to transmission wave signals in a predetermined direction in the air. The antenna 1 receives the radio wave reflected by the target and outputs a signal corresponding to the received radio wave to the transmission / reception unit 2.

  The transmission / reception unit 2 detects a signal transmitted from the antenna 1, A / D converts the signal to generate a digital reception signal, and outputs the digital reception signal to the beam former 3. The transmission / reception unit 2 generates a digital reception signal for each antenna and outputs the digital reception signal for each antenna to the beam former 3.

  The beam former 3 is an example of a beam forming unit. The beam former 3 simultaneously forms two or more reception multi-beams including a reception beam from which a target signal is detected based on a plurality of digital reception signals sent from the transmission / reception unit 2 and A reception signal in the reception beam is calculated. Normally, digital beam forming (DBF) technology is used when performing reception multi-beam forming, but analog beam forming (ABF) technology may be used.

  The target signal detector 4 is an example of a target detection unit. 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 detects a reception signal equal to or higher than the target detection threshold as a target signal. The target signal detector 4 detects distance information and azimuth angle information using the target signal. For example, the target signal detector 4 obtains target distance information based on the difference between the time when the antenna 1 emits radio waves and the time when the target signal is detected. The target signal detector 4 obtains target azimuth information from the radiation (transmission) direction of the radio wave that is the source of the target signal. The target signal detector 4 outputs the output of the beam former 3 and the detection result of the target signal detector 4 to the beam selector 5.

  When the number of simultaneous multi-beams formed by the beam former 3 is two or more, the beam selector 5 includes two reception beams (selection reception beams) including the reception beam from which the target signal is detected, and the reception thereof. The reception signal calculated by the beam (selected reception beam) is selected, and the selected two reception beams and reception signals are output to the multipath presence / absence determiner 6.

  Further, the beam selector 5 selects a reception beam necessary for angle measurement and a reception signal calculated by the reception beam based on the result determined by the multipath presence / absence determination unit 6, and the selection result (measurement). A reception beam necessary for the corner and a reception signal calculated by the reception beam are output to the switch 7.

  In addition, when the number of simultaneous multi-beams formed by the beam former 3 is two, the beam selector 5 calculates the elevation angles of all reception beams (selection reception beams) and reception signals calculated by the reception beams. And output to the multipath presence / absence determiner 6 and the switch 7.

  The multipath presence / absence determiner 6 is an example of a multipath presence / absence determination unit. The multipath presence / absence determiner 6 determines the multipath based on the elevation angle of the two received beams (selected received beam) selected by the beam selector 5 and the received signal calculated by the received beam (selected received beam). The determination result is output to the beam selector 5 and the switch 7. Details of the configuration will be described later.

  When the multipath presence / absence determiner 6 determines that there is no multipath, the switching unit 7 selects to perform angle measurement processing by the multipath outside angle measurement processor 81, and when it is determined that there is multipath, the switch 7 It is selected to perform the angle measurement process by the in-path angle measurement processor 82.

  Both the out-of-multipath angle measurement processor 81 and the in-multipath angle measurement processor 82 perform angle measurement operations on the detected target to calculate the target elevation angle.

  The multipath outside angle measurement processor 81 calculates the target elevation angle by a normal angle measurement process (first angle measurement process) that does not take a multipath countermeasure such as an amplitude comparison angle measurement method, while the multipath angle measurement The processor 82 calculates the target elevation angle by angle measurement processing (second angle measurement processing) that performs multipath countermeasures such as an amplitude comparison angle measurement method employing an off-bore method, for example.

  When it is determined that there is no multipath, the processing unit A performs a first angle measurement process that is not provided with multipath countermeasures, and when it is determined that multipath is present, multipath countermeasures are applied. A second angle measurement process is performed.

  The signal processor B is, for example, a computer.

  FIG. 2 is a block diagram showing the multipath presence / absence determiner 6 of the first embodiment. In FIG. 2, the same components as those shown in FIG.

  In FIG. 2, the multipath presence / absence determiner 6 includes a phase difference calculation unit 61, a phase difference prediction unit 62, a proportional coefficient output unit 63, an allowable error setting unit 64, and a determination unit 65.

  The phase difference calculation unit 61 calculates the phase difference between the two received signals input from the beam selector 5. The two input reception signals are reception signals of two specific reception beams that are two selection reception beams selected by the beam selector 5.

  When there is no multipath, the phase difference prediction unit 62 predicts a theoretical value that can be taken as a phase difference between the reception signals obtained from the two reception beams (specific reception beams) selected by the beam selector 5. Calculate as

  The proportional coefficient output unit 63 is an example of an output unit. The proportionality coefficient output unit 63 outputs information (parameters) necessary for the phase difference prediction unit 62 to calculate the predicted value of the phase difference to the phase difference prediction unit 62.

  The allowable error setting unit 64 is an example of a setting unit. The permissible error setting unit 64 sets the permissible error of the phase difference necessary for setting the range of the phase difference value corresponding to the absence of multipath.

  The determination unit 65 determines the presence / absence of multipath based on the difference between the value calculated by the phase difference calculation unit 61 and the value calculated by the phase difference prediction unit 62. In the present embodiment, the determination unit 65 performs multipath if the difference between the value calculated by the phase difference calculation unit 61 and the value calculated by the phase difference prediction unit 62 is within the allowable error set by the allowable error setting unit 64. If it is determined that there is no difference and the difference exceeds an allowable error, it is determined that there is multipath. The determination unit 65 outputs the determination result to the beam selector 5 and the switch 7.

  Here, the two reception signals input to the phase difference calculation unit 61 are signals received simultaneously by two reception beams (specific reception beams), and the two reception beams are referred to as beam 1 and beam 2, The received signal for beam 1 is referred to as received signal 1, and the received signal for beam 2 is referred to as received signal 2. The received signals 1 and 2 are both represented by complex numbers.

  The phase difference predicting unit 62 outputs a theoretical value that can be taken as a phase difference between received signals obtained from two received beams (specific received beams) when there is no multipath. It differs depending on the forming method, that is, the angle measuring method.

  In the first embodiment, two simultaneous Σ beams having different elevation angles are used as the two received beams, but a monopulse beam (Σ, Δ beam) may be used instead of the two simultaneous Σ beams. Is possible. The determination reference setting when the monopulse beam is used will be described in the third embodiment.

  As shown in FIG. 3, it is assumed that the antenna 1 is formed by a linear array (interval d) in which N antenna elements # 1 to #N are arranged at equal intervals.

  FIG. 3 shows a state in which radio waves (plane waves) arrive from an angle α with respect to the antenna front direction.

  If each antenna element is antenna # 1, antenna # 2,... Antenna #N in order from the left, the output (received signal) of each antenna element is added by an adder 32 via a variable phase shifter 31, respectively. Is done. The variable phase shifter 31 and the adder 32 are included in the beam former 3. In FIG. 3, the transmitter / receiver 2 is omitted for simplification of description.

Here, in order to simplify the description, it is assumed that the reception characteristics of the antenna elements are equal to each other, and the reception signal at antenna # 1 is E ₁ (t, α). At this time, since the path difference between the antenna #n and the antenna # 1 becomes d · (n-1) · sinα, when the wavelength at the transmission frequency and the lambda, the received signal E _n of the antenna #n (t, alpha) Is represented by the following equation.

E _n (t, α) = E ₁ (t, α) exp [−j2π (d / λ) · (n−1) sin α]
... (1)
Here, assuming that the beam is formed so that the nose direction of the received beam of the array antenna is an angle θ _k (k = 1, 2) from the front direction of the antenna, the received signal of antenna #n in this beam k is variable. After going through the phaser,
E _n (t, α) · exp [j2π (d / λ) · (n−1) sin θ _k ]
= E ₁ (t, α) exp [j2π (d / λ) · (n−1) · (sin θ _k −sin α)]
... (2)
Since the received signal Σ _k received by the beam k is the combined output of the equation (2), the received signal Σ _k is expressed by the following equation.

Σ _k = E ₁ (t, α) · Σexp [j2π (d / λ) · (n−1) · (sin θ _k −sin α)]
... (3)
However, Σ in the right equation in equation (3) represents the sum of n = 0 to N−1. Phase Argshiguma _k of the received signal sigma _k this time is the following formula.

argΣ _k = arg [E ₁ (t, α)]
+ Arg (Σexp [j2π (d / λ) · (n−1) · (sin θ _k −sin α)])
... (4)
Here, when θ _k −α is sufficiently small, the following approximation holds.

_{sinθ k -sinα = sinθ k -sin (} θ k - (θ k -α))
_{≒ sinθ k - [sinθ k -cosθ} k · (θ k -α)]
= Cos θ _k · (θ _k −α) (5)
It becomes. When Expression (5) is established, the phase of the reception signal Σ _k is as follows.

argΣ _k = arg [E ₁ (t, α)]
+ Arg (Σexp [j2π (d / λ) · (n−1) · cos θ _k · (θ _k −α)])
= Arg [E ₁ (t, α)] + ψ (x _k ) (6)
However,
ψ (x _k ) = arg (Σexp [j2π (d / λ) · (n−1) · x _k ]) (7)
x _k = cos θ _k · (θ _k −α) (8)
In this case, since θ _k −α is sufficiently small, x _k can be regarded as sufficiently small. Therefore, ψ (x _n ) can be approximately expressed as a linear function of x _n , and the following relationship is established.

ψ (x _k ) = ψ (0) + ψ ′ (0) · x _k (9)
However, ψ ′ (x) is a derivative of ψ (x), and ψ ′ (0) is a constant independent of θ _k and α. Also,
ψ (0) = arg (Σexp [2π (d / λ) · 0]) = argN = 0
Thus, equation (9) can be modified as follows.

ψ (x _k ) = C · x _k = C · cos θ _k · (θ _k −α) (C≡ψ ′ (0)) (10)
Here, when the distance between the beam 1 and the beam 2 is narrow,
cos θ ₁ ≈cos θ ₂ (11)
Can be considered. Normally, multipath is a problem when both the nose elevation direction of the beam and the direction of the incoming wave are close to the horizontal direction, so that θ _k −α may be considered to be sufficiently small. As for the beam interval, for example, when θ ₁ = + 0 °, if −8 ° <θ ₂ <8 °, cos θ ₂ > 0.99, and the difference between the two is 1% or less. Even if it is considered that cos θ ₁ ≈cos θ ₂ ≈1 holds, there is no practical problem.

From the above, the phase of the received signal Σ ₁ received by the beam 1 and the phase of the received signal Σ ₂ received by the beam 2 are as follows from the equations (6), (10), and (11).

argΣ ₁ = arg [E ₁ (t, α)] + ψ (x ₁ )
= Arg [E ₁ (t, α)] + C · cos θ ₁ · (θ ₁ −α) (12)
argΣ ₂ = arg [E ₁ (t, α)] + ψ (x ₂ )
= Arg [E ₁ (t, α)] + C · cos θ ₁ · (θ ₂ −α) (13)
Therefore, the phase difference between the received signal Σ ₁ and the received signal Σ ₂ is as follows.

argΣ ₂ −argΣ ₁ = C · cos θ ₁ · (θ ₂ −θ ₁ ) = φ ₀ (14)
The constant C = ψ ′ (0) is a function of the number N of antenna elements, the antenna element interval d, and the wavelength λ, and these are known and can be calculated. Also, since the beam nose elevation angles θ ₁ and θ ₂ are known, the phase difference φ ₀ between the reception signal Σ ₁ and the reception signal Σ ₂ when there is no multipath.
Can be predicted in advance.

Here, using equation (6), the received signal Σ _k when the direction of the incoming wave is α and there is no multipath can be expressed as follows.

Σ ₁ = R _1t · exp (jχ) · exp [jψ (x ₁ )] (15)
Σ ₂ = R _2t · exp (jχ) · exp [jψ (x ₂ )] (16)
R _kt : Amplitude intensity of direct wave reception signal obtained from beam k χ = arg [E ₁ (t, α)]
At this time, the reception signal Σ ₁ and the reception signal Σ ₂ when there is no multipath are represented by a complex plane as shown in FIG. FIG. 5 shows the relationship between the phase of the received signal and the nose elevation angle of the received beam used to obtain the received signal when there is no multipath. In FIG. 5, black circles indicate points obtained from the reception beam 1, and black squares indicate points obtained from the reception beam 2. As shown in equations (12) and (13), the slope of the straight line passing through the black circle and the black square is a constant value C · cos θ ₁ .

  On the other hand, the received power when the multipath wave arrives from the direction of the angle β with respect to the antenna front direction is the sum of the contribution from the direct wave and the contribution from the multipath wave, and is expressed by the following equation.

Σ ₁ = R _t · exp (jχ) · exp [jψ ₁ (x ₁ )] + R _t '· exp (jχ') · exp [jψ ₁ (x ₁ ')] (17)
Σ ₂ = R _t · exp (jχ) · exp [jψ ₂ (x ₂ )] + R _t '· exp (jχ') · exp [jψ ₂ (x ₂ ')] (18)
R ′ _t : Amplitude intensity of multipath wave reception signal obtained from beam k χ ′ = arg [E ₁ (t, β)]
x _n '= cos θ _n · (θ _n −β) (19)
At this time, when the received signal Σ ₁ and the received signal Σ ₂ in the case of multipath are expressed in a complex plane, they are as shown in FIG. In FIG. 6, the dotted line represents the contribution from the direct wave, and the broken line represents the contribution from the multipath wave. Since contributions due to multipath waves are added, it can be seen from FIG. 6 that the phases of the received signal Σ ₁ and the received signal Σ ₂ have different values from the case where there is no multipath.

  FIG. 7 shows the relationship between the phase of the received signal and the nose elevation angle of the received beam used to obtain the received signal when there are multipaths.

In FIG. 7, black circles indicate points obtained from the reception beam 1, and black squares indicate points obtained from the reception beam 2. For comparison, when there is no multipath, a point obtained from the reception beam 1 is indicated by a white circle, and a point obtained from the reception beam 2 is indicated by a white square. For the two points obtained when there is no multipath, a white square is on the straight line of the slope C · cos θ ₁ passing through the white circle, whereas for the two points obtained when there is a multipath, the black circle It can be seen that a black square usually exists at a position deviating from the straight line of the slope C · cos θ ₁ passing through.

If the value that can be taken as the phase difference between the received signal Σ ₁ and the received signal Σ ₂ when there is no multipath is the phase difference predicted value φ ₀ , the following relationship holds.

φ ₀ = C · cos θ ₁ · (θ ₂ −θ ₁ ) (20)
When comparing the phase difference predicted value φ ₀ with the actually obtained received signal Σ ₁ and the phase difference value of the received signal Σ ₂ , if the two values are different, it can be estimated that there is a multipath, If both values are close, it can be estimated that there is no multipath.

The determination unit 65 compares the value Σ ₂ −Σ ₁ calculated by the phase difference calculation unit 61 with the phase difference prediction value φ ₀ calculated by the phase difference prediction unit 62, and the difference between the two is set as an allowable error setting. If it is within the allowable error δφ set by the unit 64, it is determined that there is no multipath, and if it exceeds the allowable error δφ, it is determined that there is multipath, and the determination result is output to the beam selector 5 and the switch 7. .

FIGS. 8 and 9 show the relationship between the difference θ ₂ −θ ₁ between the nose elevation angles of the two received beams used together and the phase difference between the received signal Σ ₁ and the received signal Σ ₂ . argΣ ₂ -argΣ ₁ is a value calculated from the actually obtained received signal, and the phase difference predicted value φ ₀ is a value obtained from Equation (20). Figure 8 is argΣ ₂ -argΣ ₁ the difference of phi ₀ corresponds to the case where it is determined that no multipath since tolerance is within the error δφ, argΣ ₂ difference -Argshiguma ₁ and phi ₀ is within tolerance .delta..phi I understand that there is. On the other hand, FIG. 9 corresponds to a case where it is determined that there is multipath.

  Next, the effect of this embodiment will be described.

  According to the radar apparatus 10 of the first embodiment, the multipath presence / absence determiner 6 including the phase difference calculation unit 61, the phase difference prediction unit 62, the proportional coefficient output unit 63, the allowable error setting unit 64, and the determination unit 65 is used. This makes it possible to determine the presence or absence of multipath. Further, by combining the switch 7, the external multipath angle measurement processor 81, and the multipath internal angle measurement processor 82, it is possible to perform the multipath countermeasure processing only when there is a multipath.

  According to the present embodiment, the beam former 3 forms a plurality of reception beams having different elevation angles, and extracts reception signals from the respective reception beams. The target signal detector 4 detects a target signal indicating the presence of a target based on the reception signal in each reception beam. The multipath presence / absence determiner 6 determines the presence / absence of multipath based on reception signals of a plurality of selected reception beams including a reception beam from which a target signal is detected among a plurality of reception beams. When it is determined that there is no multipath, the processing unit A performs a first angle measurement process that is not provided with multipath countermeasures, and when it is determined that multipath is present, multipath countermeasures are applied. A second angle measurement process is performed.

  Multipath presence / absence determiner 6 includes a phase difference calculation unit 61, a phase difference prediction unit 62, and a determination unit 65. The phase difference calculation unit 61 calculates the phase difference between the reception signals in the two specific reception beams specified from the plurality of selection reception beams. The phase difference prediction unit 62 predicts a phase difference between the reception signals in the two specific reception beams in a situation where there is no multipath. The determination unit 65 determines the presence / absence of multipath based on the difference between the calculation result of the phase difference calculation unit 61 and the prediction result of the phase difference prediction unit 62.

  For this reason, it is possible to determine the presence / absence of multipath using the phase difference between the reception signals of the two specific reception beams and the predicted phase difference when there is no multipath. Then, by determining the presence or absence of multipath, it is possible to perform multipath countermeasure processing only when there is a multipath.

  In the present embodiment, the allowable error setting unit 64 sets an allowable value of a difference between the calculation result of the phase difference calculation unit 61 and the prediction result of the phase difference prediction unit 62. The determination unit 65 determines that there is multipath when the difference between the calculation result of the phase difference calculation unit 61 and the prediction result of the phase difference prediction unit 62 is larger than the allowable value, and the difference is equal to or less than the allowable value. In this case, it is determined that there is no multipath. For this reason, it is possible to adjust the accuracy of the determination of the presence / absence of multipath depending on how the allowable value is set.

  In the present embodiment, the beam former 3 forms two or more simultaneous Σ beams having different elevation angles, including the simultaneous Σ beams from which the target signals are detected, as a plurality of reception beams. The multipath presence / absence determiner 6 includes a proportional coefficient output unit 63 that outputs parameters necessary for predicting the phase difference to the phase difference prediction unit 62. The phase difference prediction unit 62 predicts a phase difference in a situation where there is no multipath, based on the elevation angles of the two specific reception beams and the parameters from the proportional coefficient output unit 63.

  For this reason, even if two or more simultaneous Σ beams having different elevation angles including the simultaneous Σ beams in which the target signal is detected are formed as a plurality of received beams, the phase difference prediction unit 62 does not have multipath. It is possible to predict the phase difference.

  Further, in the present embodiment, the plurality of selective reception beams and the two specific reception beams include the two simultaneous Σ beams in which the target signal is detected among the two or more simultaneous Σ beams formed by the beam former 3. It is a simultaneous Σ beam of books. The phase difference prediction unit 62 predicts the phase difference between the reception signals in the two specific reception beams in a situation where there is no multipath, based on the elevation angles of the two specific reception beams.

  Therefore, it is possible to determine the presence or absence of multipath using two simultaneous Σ beams.

<Embodiment 2>
In the first embodiment, it is assumed that the distance between the beams to be used is narrow, that is, the relationship of Expression (11) is established. However, in Embodiment 2, the distance between the beams to be used is wide and the relation of Expression (11) is satisfied. It is possible to determine the presence / absence of multipath even when the above is not established. However, in Embodiment 1, two or more simultaneous multi-beams are sufficient, whereas in Embodiment 2, three or more simultaneous multi-beams are required.

  FIG. 10 is a block diagram illustrating a multipath presence / absence determiner 6A according to the second embodiment. In FIG. 10, the same components as those shown in FIG.

  The second embodiment differs from the first embodiment in that a beam selector 5A and a multipath presence / absence determiner 6A are used instead of the beam selector 5 and the multipath presence / absence determiner 6 used in the first embodiment. In the first embodiment, the beam selector 5 uses two simultaneous beams including the beam from which the target signal is detected. In the second embodiment, the beam selector 5A includes the beam from which the target signal is detected. In addition to the configuration of the multipath presence / absence determiner 6, a correction value calculation unit 66 is added to the multipath presence / absence determiner 6A using three simultaneous beams.

  When the number of simultaneous multi-beams (several simultaneous Σ beams) formed by the beam former 3 is four or more, the beam selector 5A is calculated by three received beams (selected received beams) and the received beams. The received signal is selected, and the selection result (the elevation angle of the selected received beam and the received signal) is output to the multipath presence / absence determiner 6A.

  The beam selector 5A selects a reception beam necessary for angle measurement and a reception signal calculated by the reception beam based on the result determined by the multipath presence / absence determination unit 6A, and switches the selection result. To the device 7.

  When the number of simultaneous multi-beams formed by the beam former 3 is 3, the beam selector 5A multipaths all received beams (selected received beams) and received signals calculated by the received beams. Output to the presence / absence determiner 6A.

  Here, as shown in FIG. 10, among the three reception beams selected by the beam selector 5A and the reception signals obtained by the reception beams, two reception beams (the elevation angles of the two reception beams) and The reception signal obtained by the reception beam is sent to the correction value calculation unit 66 in the multipath presence / absence determiner 6A.

  Similar to the first embodiment, the proportionality coefficient output unit 63 outputs information necessary for calculating the predicted value of the phase difference to the phase difference prediction unit 62, and also receives the received signals (two) calculated by the correction value calculation unit 66. Information necessary for calculating the phase argΣ ′ of one of the specific reception beams) and the nose elevation angle θ ′ of one of the two specific reception beams (hereinafter also referred to as “corrected beam”). Also output.

The correction value calculation unit 66 is an example of a calculation unit. The correction value calculation unit 66 corrects the received signal based on the nose elevation angle and the phase of the received signal for the two received beams input from the beam selector 5A and the constant C input from the proportional coefficient output unit 63. The phase argΣ ₂ ′ of one of the two specific received beams and the nose elevation angle θ ₂ ′ of the corrected beam (one of the two specific received beams) are calculated and the phase argΣ of the corrected received signal ₂ ′ is output to the phase difference calculation unit 61, and the corrected nose elevation angle θ ₂ ′ of the beam is output to the phase difference prediction unit 62.

The corrected beam nose elevation angle θ ₂ ′ calculated by the correction value calculator 66 corresponds to the nose elevation angle θ ₂ of the beam 2 in the first embodiment, and the corrected received signal phase argΣ ₂ ′ is the beam in the first embodiment. order corresponding to the phase sigma ₂ received signals received at 2, phase difference calculation unit 61, the phase difference prediction portion 62, the allowable error setting unit 64, processing in the determining unit 65 are the same as in embodiment 1.

  When there is no multipath, the phase of the reception signal obtained by the three reception beams selected by the beam selector 5A is as follows from the equations (6) and (10).

Beam 1: arg Σ ₁ = arg [E ₁ (t, α)] + ψ (x ₁ )
= Arg [E ₁ (t, α)] + C · cos θ ₁ · (θ ₁ −α) (21)
Beam 2: arg Σ ₂ = arg [E ₁ (t, α)] + ψ (x ₂ )
= Arg [E ₁ (t, α)] + C · cos θ ₂ · (θ ₂ −α) (22)
Beam 3: arg Σ ₃ = arg [E ₁ (t, α)] + ψ (x ₃ )
= Arg [E ₁ (t, α)] + C · cos θ ₃ · (θ ₃ −α) (23)
FIG. 11 shows the relationship between the beam elevation angle and the phase of the received signal when there is no multipath, and FIG. 12 shows the relationship between the beam elevation angle and the phase of the received signal when there is a multipath. In each figure, the horizontal axis corresponds to the elevation angle θ, and the vertical axis corresponds to the phase argΣ of the received signal.

Assuming k = 1, 2, and 3, in each of the figures, the point (θ _k , argΣ _k ) indicated by the black circle has the phase of the received signal obtained when the beam nose elevation angle θ _k is argΣ _k . It is shown that.

Here, a straight line passing through the point (θ ₁ , arg Σ ₁ ) and having an inclination of C · cos θ ₁ is a solid line, and a straight line passing through the point (θ ₂ , arg Σ ₂ ) and having an inclination of C · cos θ ₂ is a dotted line. ₃ , arg Σ ₃ ), and a straight line having a slope of C · cos θ ₃ is represented by a one-dot broken line. In the absence of a Mars path, as shown in FIG. arg [E ₁ (t, α)]).

  On the other hand, when there is a Mars pass, normally three straight lines do not intersect at one point as shown in FIG.

  By utilizing this difference in characteristics, it is possible to determine the presence or absence of multipath. The procedure for determining the presence / absence of multipath is described below.

  FIG. 13 is a diagram for explaining the processing contents in the correction value calculation unit 66 using the relationship between the beam elevation angle and the phase of the received signal. In FIG. 13, the horizontal axis corresponds to the elevation angle θ, and the vertical axis corresponds to the phase argΣ of the received signal.

The two reception beams input from the beam selector 5A are referred to as reception beam 2 and reception beam 3, respectively, and the points obtained from the respective beams are defined as (θ ₂ , arg Σ ₂ ) and (θ ₃ , arg Σ ₃ ). At this time, in FIG. 13, a straight line having a slope of C · cos θ ₂ passing through the point (θ ₂ , argΣ ₂ ) and a straight line having a slope of C · cos θ ₃ passing through the point (θ ₃ , argΣ ₃ ) are drawn. This will give you an intersection. The horizontal axis coordinate of this intersection point corresponds to the nose elevation angle θ ₂ ′ of the corrected beam, and the vertical axis coordinate of the intersection point corresponds to the phase argΣ ₂ ′ of the corrected received signal. From this, the corrected phase argΣ ₂ ′ of the received signal and the corrected beam nose elevation angle θ ₂ ′ are calculated. The corrected phase argΣ ₂ of the received signal is arg [E ₁ (t, α)] in equation (21), and the corrected nose elevation angle θ ₂ ′ is the arrival wave direction α of the radio wave.

FIG. 14 shows the relationship between the phase of the received signal and the nose elevation angle of the received beam used to obtain the received signal when there is no multipath. In FIG. 14, black circles indicate points obtained from the received beam 1, and white circles indicate points obtained from the corrected beam. As shown in FIG. 11, the slope of the straight line passing through the black circle and the white circle in FIG. 14 is a constant value C · cos θ ₁ .

FIG. 15 shows the relationship between the phase of the received signal and the nose elevation angle of the received beam used to obtain the received signal when there are multipaths. In FIG. 15, black circles indicate points obtained from the received beam 1, and white circles indicate points obtained from the corrected beam. When there is no multipath, a black circle is on the straight line of the slope C · cos θ ₁ passing through the white circle as shown in FIG. 14, while the two points obtained when there is a multipath are slopes through the white circle. It can be seen that a black circle usually exists at a position deviating from the C · cos θ ₁ straight line.

By comparing FIG. 5 and FIG. 14 or FIG. 7 and FIG. 15, the nose elevation angle θ ₂ ′ of the corrected beam in the second embodiment corresponds to the nose elevation angle θ ₂ of the beam 2 in the first embodiment and is corrected. It can be seen that the phase argΣ ₂ ′ of the received signal corresponds to the phase Σ ₂ of the received signal received by the beam 2 in the first embodiment.

If the value that can be taken as the phase difference between the received signal Σ ₁ and the corrected received signal Σ ₂ ′ when there is no multipath is the phase difference predicted value φ ₀ , the following relationship holds.

φ ₀ = C · cos θ ₁ · (θ ₂ '−θ ₁ ) (24)
The determination unit 65 compares argΣ ₂ ′ −argΣ ₁ , which is a value calculated by the phase difference calculation unit 61, with the phase difference prediction value φ ₀ calculated by the phase difference prediction unit 62, and the difference between the two is an allowable error. If it is within the allowable error δφ set by the setting unit 64, it is determined that there is no multipath, and if it exceeds the allowable error δφ, it is determined that there is multipath, and the determination result is output to the beam selector 5A and the switch 7. To do.

  In the present embodiment, the beam former 3 forms three or more simultaneous Σ beams having different elevation angles, including the simultaneous Σ beams in which the target signal is detected, as a plurality of reception beams. The plurality of selective reception beams are three simultaneous Σ beams including the simultaneous Σ beams in which the target signal is detected among the three or more simultaneous Σ beams formed by the beam former 3. The correction value calculation unit 66 uses two elevations of two simultaneous Σ beams out of the three simultaneous Σ beams that are selected reception beams and two reception signals from the two simultaneous Σ beams. The elevation angle of one of the specific reception beams and the reception signal of the one specific reception beam are generated. The remaining one simultaneous Σ beam among the three simultaneous Σ beams that are the selective reception beams is the other specific reception beam of the two specific reception beams. The phase difference predicting unit 62 predicts the phase difference of the reception signals in the two specific reception beams in a situation where there is no multipath, based on the elevation angles of the two specific reception beams.

  For this reason, according to the radar apparatus 10 of the second embodiment, it is possible to determine the presence / absence of multipath even when the interval between the beams to be used is wide and the relationship of Expression (11) does not hold. Multipath countermeasure processing can be performed only when there are multipaths.

<Embodiment 3>
In the first and second embodiments, it is assumed that the amplitude comparison angle measurement method is adopted. However, in the third embodiment, the presence / absence of multipath can be determined even when the monopulse method is adopted.

  FIG. 16 is a block diagram illustrating a configuration of the multipath presence / absence determiner 6B according to the third embodiment. In FIG. 16, the same components as those shown in FIG.

  The third embodiment is different from the first embodiment in that a beam selector 5B and a multipath presence / absence determiner 6B are used instead of the beam selector 5 and the multipath presence / absence determiner 6, and the multipath presence / absence determiner 6B is The configuration is such that the proportional coefficient output unit 63 is removed from the configuration of the multipath presence / absence determiner 6.

  If the Σ beam pattern is S (θ) and the Δ beam pattern is D (θ), the received signals Σ and Δ in each received beam are expressed by the following equations, respectively.

Σ = R _t · exp (jχ _ΣΔ ) · [S (α) + γ · S (β) · exp (jψ _ΣΔ )]
... (25)
Δ = R _t · exp (jχ _ΣΔ ) · [D (α) + γ · D (β) · exp (jψ _ΣΔ )]
... (26)
α: Elevation angle of direct wave β: Elevation angle of multipath wave R _t : Amplitude intensity of direct wave χ _ΣΔ : Absolute phase of direct wave γ: Relative amplitude ratio of multipath wave to direct wave ψ _ΣΔ : Multipath wave to direct wave Relative phase difference Since no multipath wave is received in a situation where there is no multipath, the relative amplitude ratio γ of the multipath wave with respect to the direct wave becomes = 0, and from the equations (25) and (26), the following is obtained.

argΔ−argΣ = arg (D (α) / S (α)) (27)
Here, since it is known from Non-Patent Document 1 that D (α) / S (α) is a real number in Equation (27), the Σ and Δ signals obtained by the monopulse method in the absence of multipath Since the phase difference is 0 or π regardless of the number of antenna elements and the antenna element spacing, the following relationship is established.

φ ₀ = argΔ−argΣ = 0 or π (28)
Since the parameter C required in the first embodiment for obtaining the phase difference predicted value φ ₀ is not required, the proportional coefficient output unit 63 is not required in the third embodiment as shown in FIG.

  FIG. 17 is a diagram showing received signals Σ and Δ on a complex plane based on Expressions (25) and (26) in a situation where there is no multipath. A black circle indicates a Σ signal, and a black square indicates a Δ signal. FIG. 17 shows an example in which Δ / Σ takes a negative value, and it can be seen that the phase difference between the received signals Σ and Δ is π.

  On the other hand, FIG. 18 is a diagram showing received signals Σ and Δ on a complex plane based on Expressions (25) and (26) in a situation where there are multipaths. A black circle represents the received signal Σ, and a black square represents the received signal Δ. The dotted line indicates the contribution by the direct wave, and the broken line indicates the contribution by the multipath wave. Further, for comparison, the Σ signal in a situation without multipath is indicated by a white circle, and the Σ signal is indicated by a white square. It can be seen that the phase difference between the received signals Σ and Δ is neither 0 nor π.

Therefore, when the phase difference predicted value φ ₀ given by the equation (28) is compared with the phase difference values of the actually obtained received signals Σ and Δ, there is a multipath if both values are different. If both values are close, it can be estimated that there is no multipath.

The determination unit 65 compares argΔ−argΣ that is the value calculated by the phase difference calculation unit 61 with the phase difference prediction value φ ₀ output from the phase difference prediction unit 62, and the difference between the two is an allowable error setting unit 64. If it is within the permissible error δφ set in step 1, it is determined that there is no multipath, and if it exceeds the permissible error δφ, it is determined that there is multipath, and the determination result is output to the beam selector 5B and the switch 7.

  In the present embodiment, the external multi-path angle measurement processor 81 performs normal monopulse-type angle measurement processing (first angle measurement processing) without taking multi-path countermeasures, and the multi-path internal angle measurement processor 82 Then, monopulse type angle measurement processing (second angle measurement processing) with multipath countermeasures as shown in Patent Document 3 is performed.

  In the present embodiment, the beam former 3 forms a monopulse beam having a Σ beam and a Δ beam as a plurality of reception beams. The monopulse beam becomes a plurality of selective reception beams and two specific reception beams. For this reason, since it is possible to determine the presence or absence of multipath even when the angle measurement method is a monopulse method, it is possible to perform multipath countermeasure processing only when there is multipath as in the first embodiment.

<Embodiment 4>
In the first to third embodiments, the beam selector 5, 5 </ b> A or 5 </ b> B selects a set of data necessary for determining the presence / absence of multipath, such as the reception beam and the reception signal calculated by the reception beam, and the multipath presence / absence determination unit However, in the fourth embodiment, the presence / absence of multipath is determined by majority processing using a plurality of data necessary for determining the presence / absence of multipath. This improves the accuracy of the determination of the presence / absence of multipath.

  FIG. 19 is a block diagram illustrating a radar apparatus 10C according to the fourth embodiment. 19, the same components as those shown in FIG. 1 are denoted by the same reference numerals.

  The fourth embodiment is different from the first embodiment in that a memory 91 and a majority processor 92 are added to the configuration of the first embodiment. The memory 91 and the majority processor 92 are included in the determination processing unit C. In FIG. 19, instead of the beam selector 5 and the multipath presence / absence determiner 6, a beam selector 5A and a multipath presence / absence determiner 6A, or a beam selector 5B and a multipath presence / absence determiner 6B are used. Also good.

  When there is no multipath, the phase difference between the received signals obtained with different receive beams can be predicted, but when there is multipath, the influence of multipath is complicated by the antenna 1 and the target position and the radio wave propagation path. Therefore, it is usually impossible to predict the phase difference.

However, the phase difference of the received signal in the case of there multipath becomes a value within the tolerance δφ against accidental phase difference prediction value phi _0, can also occur when it is erroneously determined that no multipath in the determination unit 65.

FIG. 20 shows an example in which the phase difference between the received signals Σ ₁ and Σ _{2 in} the _first embodiment is the same as the phase difference predicted value φ ₀ when there is multipath. FIG. 20 shows an example in which the phase difference between the direct wave component and the multipath wave component in the received signal Σ ₁ is 0 and the phase difference between the direct wave component and the multipath wave component in the received signal Σ ₂ is π. in the embodiment 1, the received signal sigma _1, sigma ₂ for each, if the phase difference between the direct wave component and a multipath wave component becomes 0 or [pi, also multipath is present, the received signal sigma _1, sigma ₂ phase difference becomes a value within the tolerance δφ against accidental phase difference prediction value phi _0.

21 in the embodiment 3, an example where the phase difference in the case of there multipath assumes a value within the allowable error δφ to the phase difference prediction value phi _0. As in the case of the first embodiment, in the third embodiment, the received signal Σ, Δ is received even when multipath exists even if the phase difference between the direct wave component and the multipath wave component is 0 or π. signal sigma, the phase difference Δ is a value within the tolerance δφ against accidental phase difference prediction value phi _0.

  In this case, in spite of being affected by multipath, normal angle measurement processing without multipath countermeasures is performed, so that angle measurement accuracy is lowered.

However, while the phase difference of the received signal at no multipath time coincides always with the phase difference prediction value phi _0, case where the phase difference becomes equal chance retardation predicted value phi ₀ in the case of there multipath Since it is extremely rare, it is possible to increase the accuracy of determination by taking a plurality of data.

  As a plurality of data, for example, when a plurality of targets are detected within a close distance range, data obtained from the plurality of targets can be combined into a plurality of data.

  In the first and second embodiments that employ amplitude comparison angle measurement using simultaneous multi-beams, the beam selector 5 or 5A selects more than the number of reception beams necessary for the determination of the presence or absence of multipath, A plurality of data can be taken. For example, when four receiving beams are selected by the beam selector 5 in the first embodiment, the beam 1 and the beam 2, the beam 1 and the beam 3, the beam 1 and the beam 4, the beam 2 and the beam 3, and the beam 2 are combined as combinations. A total of six combinations of beam 4, beam 3, and beam 4 are possible.

  Multipath presence / absence determination results for a plurality of data obtained by the multipath presence / absence determiner 6, 6A or 6B are stored in the memory 91. When a predetermined number of combinations of data (multipath presence / absence determination result) are stored in the memory 91, these data are output to the majority processor 92.

  The majority processor 92 determines the presence / absence of a multipath by performing a majority process based on a plurality of determination results regarding the presence / absence of a multipath input from the memory 91. The majority processor 92 determines that there is no multipath if the number of data determined by the multipath presence / absence determiner 6, 6A or 6B is greater than or equal to a predetermined number, and determines that there is no multipath if it is less than the predetermined number. Judge that there is.

  In the present embodiment, the phase difference calculation unit 61 calculates the phase difference between the reception signals of the two specific reception beams for each combination of two specific reception beams specified from the plurality of selection reception beams. The phase difference prediction unit 62 predicts the phase difference of each reception signal in the two specific reception beams in a situation where there is no multipath for each combination of the two specific reception beams. The determination unit 65 determines the presence or absence of multipath based on the difference between the calculation result of the phase difference calculation unit 61 and the prediction result of the phase difference prediction unit 62 for each combination of two specific reception beams. The determination processing unit C determines the presence / absence of multipath based on the determination result of the determination unit 65 for each combination of two specific reception beams. The processing unit A performs first angle measurement processing when the determination processing unit C determines that there is no multipath, and performs second angle measurement processing when the determination processing unit C determines that there is multipath.

  For this reason, since the presence / absence of multipath is determined based on a plurality of determination results for each combination of two specific reception beams, the accuracy of determination of the presence / absence of multipath can be improved.

<Embodiment 5>
In the fourth embodiment, it is possible to reduce the probability of erroneously determining that there is no multipath when there is multipath by performing multipath presence determination using a plurality of data necessary for determining the presence or absence of multipath. However, in the fifth embodiment, by referring to past information regarding the presence / absence of multipath at a certain target distance, elevation angle, and azimuth, it is erroneously determined that there is no multipath compared to the fourth embodiment when there is multipath. It is possible to further reduce the probability of being played.

  FIG. 22 is a block diagram illustrating a configuration of a radar apparatus 10D according to the fifth embodiment. In FIG. 22, the same components as those shown in FIG. 19 are denoted by the same reference numerals.

  The fifth embodiment is different from the fourth embodiment shown in FIG. 19 in that a map generator 100 and a map memory 110 are added to the configuration of the fourth embodiment.

  The map generator 100 is an example of a determination control unit. The map generator 100 is a small area unit divided into a predetermined distance range, azimuth angle range, and beam elevation angle range from the target distance, azimuth angle detected by the target signal detector 4 and the beam elevation angle used for detection. In addition, the map information is generated by mapping the determination result of the multipath presence / absence by the majority processor 92, and the map information is output to the map memory 110.

  The map memory 110 is an example of a storage unit. The map memory 110 stores past map information, and the map information is updated when map information is newly generated by the map generator 100. The map information is an example of relationship history information that represents a history of relationship between target distance information, target azimuth information, and results of angle measurement processing by the processing unit A and determination results by the determination processing unit C. .

  Details of a method for generating map information related to the presence or absence of multipath in the map generator 100 will be described below.

  Past map information is input to the map generator 100 from the map memory 110, and the latest information is input from the target signal detector 4 and the majority processor 92. Information about the target distance, azimuth angle, and beam elevation angle used for detection are input from the target signal detector 4, and information about the presence / absence of multipath is input from the majority processor 92.

  The map generator 100 performs majority processing using the map information of the past multiple scans input from the map memory 110 and the latest information described above. The map generator 100 generates map information indicating that there is no multipath when the number of times determined that there is no multipath is a predetermined number or more, and if the number of times determined that there is no multipath is less than the predetermined number. Generates map information that multipath exists. The map generator 100 records the newly generated map information in the map memory 110, and updates the map information recorded in the map memory 110.

  The determination result of the presence / absence of multipath described in the map information in the map memory 110 is sent to the switch 7.

  In the present embodiment, the target signal detector 4 generates target distance information and target azimuth information based on the target signal. The map memory 110 stores map information (relation history information) representing a history of the relationship between the target distance information, the target azimuth angle information, the result of the angle measurement process of the processing unit A, and the determination result of the determination processing unit C. Remember. The map generator 100 determines the presence / absence of multipath based on the map information in the map memory 110. The processing unit A performs the first angle measurement process when the map generator 100 determines that there is no multipath instead of the determination processing unit C, and determines that the map generator 100 has multipath instead of the determination processing unit C. If so, the second angle measurement process is performed.

  For this reason, according to the radar apparatus 10D of the fifth embodiment, since the map information relating to the past multipath presence / absence is used, the probability of erroneously determining that there is no multipath is higher when there is multipath than in the fourth embodiment. Further reduction is possible.

  In each of the above embodiments, the signal processor B may be realized by a computer. In this case, the computer reads and executes a program recorded on a recording medium such as a CD-ROM (Compact Disk Read Only Memory) readable by the computer, and executes the function of the signal processor B. The recording medium is not limited to the CD-ROM and can be changed as appropriate.

  In each embodiment described above, the illustrated configuration is merely an example, and the present invention is not limited to the configuration.

DESCRIPTION OF SYMBOLS 1 Antenna # 1-#N Antenna 2 Transmitter / receiver 3 Beamformer 31 Variable phase shifter 32 Adder 4 Target signal detector 5, 5A, 5B Beam selector 6, 6A, 6B Multipath presence / absence determiner 61 Phase difference calculation Unit 62 Phase difference prediction unit 63 Proportional coefficient output unit 64 Allowable error setting unit 65 Judgment unit 66 Correction value calculation unit 7 Switcher 81 Multipath outside angle measuring processor 82 Multipath angle measuring processor 91 Memory 92 Majority processing unit 100 Map generator 110 Map memory 10, 10C, 10D Radar device A processing unit B signal processor C determination processing unit

Claims (10)

A beam forming unit that forms a plurality of reception beams having different elevation angles and extracts a reception signal in each reception beam;
A target detection unit for detecting a target signal indicating the presence of a target based on a reception signal in each reception beam;
A multipath presence / absence determination unit that determines presence / absence of multipath based on reception signals in a plurality of selection reception beams including a reception beam in which the target signal is detected among the plurality of reception beams;
When it is determined that there is no multipath, a first angle measurement process without multipath countermeasures is performed, and when it is determined that there is multipath, a second measurement with multipath countermeasures is performed. A processing unit for performing corner processing,
The multipath presence determination unit
A phase difference calculation unit for calculating a phase difference of reception signals in two specific reception beams specified from the plurality of selection reception beams;
A phase difference prediction unit that predicts a phase difference between the reception signals in the two specific reception beams in a situation where there is no multipath;
Based on the difference between the predicted results of the phase difference prediction unit and the calculation result of the phase difference calculating section, seen including and a determination unit for determining presence or absence of the multipath,
The beam forming unit forms, as the plurality of reception beams, two or more simultaneous Σ beams having different elevation angles including the simultaneous Σ beam in which the target signal is detected,
The multipath presence / absence determining unit further includes an output unit that outputs parameters necessary for predicting the phase difference to the phase difference predicting unit,
The phase difference prediction unit is a radar device that predicts the phase difference based on an elevation angle of the two specific reception beams and the parameter . A beam forming unit that forms a plurality of reception beams having different elevation angles and extracts a reception signal in each reception beam;
A target detection unit for detecting a target signal indicating the presence of a target based on a reception signal in each reception beam;
A multipath presence / absence determination unit that determines presence / absence of multipath based on reception signals in a plurality of selection reception beams including a reception beam in which the target signal is detected among the plurality of reception beams;
When it is determined that there is no multipath, a first angle measurement process without multipath countermeasures is performed, and when it is determined that there is multipath, a second measurement with multipath countermeasures is performed. A processing unit for performing corner processing,
The multipath presence determination unit
A phase difference calculation unit for calculating a phase difference of reception signals in two specific reception beams specified from the plurality of selection reception beams;
A phase difference prediction unit that predicts a phase difference between the reception signals in the two specific reception beams in a situation where there is no multipath;
Based on the difference between the predicted results of the phase difference prediction unit and the calculation result of the phase difference calculating section, seen including and a determination unit for determining presence or absence of the multipath,
The beam forming unit forms, as the plurality of reception beams, two or more simultaneous Σ beams having different elevation angles including the simultaneous Σ beam in which the target signal is detected,
The plurality of selective reception beams and the two specific reception beams are two simultaneous Σ beams including the simultaneous Σ beams in which the target signal is detected among the two or more simultaneous Σ beams,
The phase difference prediction unit is a radar device that predicts the phase difference based on an elevation angle of the two specific reception beams . A beam forming unit that forms a plurality of reception beams having different elevation angles and extracts a reception signal in each reception beam;
A target detection unit for detecting a target signal indicating the presence of a target based on a reception signal in each reception beam;
A multipath presence / absence determination unit that determines presence / absence of multipath based on reception signals in a plurality of selection reception beams including a reception beam in which the target signal is detected among the plurality of reception beams;
When it is determined that there is no multipath, a first angle measurement process without multipath countermeasures is performed, and when it is determined that there is multipath, a second measurement with multipath countermeasures is performed. A processing unit for performing corner processing,
The multipath presence determination unit
A phase difference calculation unit for calculating a phase difference of reception signals in two specific reception beams specified from the plurality of selection reception beams;
A phase difference prediction unit that predicts a phase difference between the reception signals in the two specific reception beams in a situation where there is no multipath;
Based on the difference between the predicted results of the phase difference prediction unit and the calculation result of the phase difference calculating section, seen including and a determination unit for determining presence or absence of the multipath,
The beam forming unit forms, as the plurality of reception beams, three or more simultaneous Σ beams having different elevation angles including the simultaneous Σ beam in which the target signal is detected,
The plurality of selective reception beams are three simultaneous Σ beams including the simultaneous Σ beams in which the target signal is detected among the three or more simultaneous Σ beams,
The multipath presence / absence determining unit is configured to determine the two specific identification signals based on elevation angles of two simultaneous Σ beams of the three simultaneous Σ beams and reception signals of the two simultaneous Σ beams. A calculation unit for generating one elevation angle of the reception beam and the one reception signal;
Of the three simultaneous Σ beams, the remaining one simultaneous Σ beam is the other of the two specific reception beams,
The phase difference prediction unit is a radar device that predicts the phase difference based on an elevation angle of the two specific reception beams . The radar apparatus according to any one of claims 1 to 3 ,
The multipath presence / absence determining unit further includes a setting unit that sets an allowable value of a difference between the calculation result of the phase difference calculation unit and the prediction result of the phase difference prediction unit,
The determination unit determines that the multipath exists when the difference between the calculation result of the phase difference calculation unit and the prediction result of the phase difference prediction unit is larger than the allowable value, and the difference is the allowable value. A radar apparatus that determines that the multipath does not exist when: The radar apparatus according to claim 1 , wherein
The beam forming unit forms, as the plurality of reception beams, two or more simultaneous Σ beams having different elevation angles including the simultaneous Σ beam in which the target signal is detected,
The plurality of selective reception beams and the two specific reception beams are two simultaneous Σ beams including the simultaneous Σ beams in which the target signal is detected among the two or more simultaneous Σ beams,
The phase difference prediction unit is a radar device that predicts the phase difference based on an elevation angle of the two specific reception beams. The radar apparatus according to claim 1 , wherein
The beam forming unit forms, as the plurality of reception beams, three or more simultaneous Σ beams having different elevation angles including the simultaneous Σ beam in which the target signal is detected,
The plurality of selective reception beams are three simultaneous Σ beams including the simultaneous Σ beams in which the target signal is detected among the three or more simultaneous Σ beams,
The multipath presence / absence determining unit is configured to determine the two specific identification signals based on elevation angles of two simultaneous Σ beams of the three simultaneous Σ beams and reception signals of the two simultaneous Σ beams. A calculation unit for generating one elevation angle of the reception beam and the one reception signal;
Of the three simultaneous Σ beams, the remaining one simultaneous Σ beam is the other of the two specific reception beams,
The phase difference prediction unit is a radar device that predicts the phase difference based on an elevation angle of the two specific reception beams. The radar apparatus according to any one of claims 1 to 6,
The phase difference calculation unit calculates a phase difference of reception signals in the two specific reception beams for each combination of two specific reception beams specified from the plurality of selection reception beams,
The phase difference prediction unit predicts a phase difference of each reception signal in the two specific reception beams in a situation where there is no multipath for each combination of the two specific reception beams,
The determination unit determines presence / absence of the multipath based on a difference between a calculation result of the phase difference calculation unit and a prediction result of the phase difference prediction unit for each combination of the two specific reception beams,
A determination processing unit that determines presence or absence of the multipath based on a determination result of the determination unit for each combination of the two specific reception beams;
The processing unit performs the first angle measurement process when the determination processing unit determines that the multipath is not present, and performs the second angle measurement process when the determination processing unit determines that the multipath is present. , Radar equipment. The radar apparatus according to claim 7, wherein
The target detection unit generates the target distance information and the target azimuth information based on the target signal,
A storage unit that stores relationship history information that represents a history of a relationship between the target distance information, the target azimuth information, and a result of the angle measurement processing of the processing unit and a determination result of the determination processing unit;
A determination control unit that determines the presence or absence of the multipath based on the relationship history information,
The processing unit performs the first angle measurement process when the determination control unit determines that there is no multipath instead of the determination processing unit, and the determination control unit replaces the multipath with the determination processing unit. A radar apparatus that performs the second angle measurement process when it is determined that there is. An angle measurement method in a radar device,
A beam forming step of forming a plurality of reception beams having different elevation angles and extracting a reception signal in each reception beam;
A target detection step of detecting a target signal indicating the presence of a target based on the received signal in each of the received beams;
A multipath presence / absence determination step for determining presence / absence of multipath based on reception signals in a plurality of selection reception beams including the reception beam in which the target signal is detected among the plurality of reception beams;
When it is determined that there is no multipath, a first angle measurement process without multipath countermeasures is performed, and when it is determined that there is multipath, a second measurement with multipath countermeasures is performed. Processing steps for performing corner processing,
The multipath presence determination step includes
A phase difference calculating step of calculating a phase difference of received signals in two specific received beams specified from the plurality of selected received beams;
A phase difference prediction step for predicting a phase difference between the reception signals in the two specific reception beams in a situation where there is no multipath;
Based on the difference between the predicted results of the phase difference between the calculation result of the phase difference, seen including and a determination step of determining whether the multipath,
In the beam forming step, as the plurality of reception beams, two or more simultaneous Σ beams having different elevation angles including the simultaneous Σ beam in which the target signal is detected are formed,
In the multipath presence / absence determination step, a parameter required for predicting the phase difference is further output to the phase difference prediction unit,
In the phase difference prediction step, the phase difference is predicted based on an elevation angle of the two specific reception beams and the parameter . On the computer,
A beam forming procedure for forming a plurality of reception beams having different elevation angles and extracting a reception signal in each reception beam;
A target detection procedure for detecting a target signal indicating the presence of a target based on a received signal in each of the received beams;
A multipath presence / absence determination procedure for determining presence / absence of multipath based on reception signals in a plurality of selective reception beams including a reception beam in which the target signal is detected among the plurality of reception beams;
When it is determined that there is no multipath, a first angle measurement process without multipath countermeasures is performed, and when it is determined that there is multipath, a second measurement with multipath countermeasures is performed. A processing procedure for performing corner processing, and
The multipath presence determination procedure includes:
A phase difference calculation procedure for calculating a phase difference of reception signals in two specific reception beams specified from the plurality of selection reception beams;
A phase difference prediction procedure for predicting a phase difference of each received signal in the two specific received beams in the absence of the multipath;
Based on the difference between the predicted results of the phase difference between the calculation result of the phase difference, seen including and a determination procedure for determining the presence or absence of the multipath,
In the beam forming procedure, as the plurality of received beams, two or more simultaneous Σ beams having different elevation angles including the simultaneous Σ beam in which the target signal is detected are formed,
In the multipath presence / absence determination procedure, further, a parameter necessary for predicting the phase difference is output to the phase difference prediction unit,
In the phase difference prediction procedure, the phase difference is predicted based on an elevation angle of the two specific reception beams and the parameter .

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