JP2015025744A - Radar device and flying target elevation calculation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radar device capable of acquiring altitude information with high accuracy even under a multipath environment.SOLUTION: The radar device includes: a DBF antenna 5 which receives beams reflected by a target which are different by elevation and azimuth and are in the same direction, and outputs a plurality of reception signals due to beams at a first nose angle as a first group of reception signals and outputs a plurality of reception signals due to beams at a second nose angle as a second group of reception signals; a processing unit 8 which outputs first amplitude data from the same target on the basis of the first group of reception signals and detects and outputs second amplitude data from the same target on the basis of the second group of reception signals; and a multipath goniometric processor 9 which calculates an elevation based on the first amplitude data as a first elevation and calculates an elevation based on the second amplitude data as a second elevation and compares a variation of the first nose angle relative to the second nose angle with a variation of the first elevation relative to the second elevation to determine one of the first elevation and the second elevation as the elevation of the target in accordance with the comparison result.

Description

  The present invention relates to a radar apparatus having a digital beam forming antenna and a flying object elevation angle calculation method.

  A radar apparatus generally observes target detection, measurement of a target position, flight status of a target, and the like by transmitting radio waves to space and receiving radio waves reflected by the target.

  That is, the radio wave transmitted from the antenna to the space is reflected by the target. This reflected wave is received again by the antenna and used as a received signal. This received signal includes a signal by a radio wave other than the radio wave reflected by the target.

  In order to detect the target, a signal (target signal) based on the radio wave reflected by the target is extracted. The extraction of the target signal is performed as follows. First, the received signal is A / D converted at a predetermined sampling interval to be converted into a digital signal, and unnecessary signal processing such as suppression of interference signals is performed on the digital signal. Then, the amplitude value of the digital signal that has been subjected to unnecessary signal processing is acquired at each sampling time, and if this amplitude value is greater than a preset threshold value, the digital received signal is a reflected wave signal (target Signal). That is, a signal having an amplitude value larger than a preset threshold value is extracted as the target signal.

  On the other hand, in order to know the target altitude, it is necessary to measure the distance to the target and the elevation angle. The distance measurement is a basic function of the radar apparatus, and the distance can be obtained from the round-trip time of the radio wave.

  Therefore, an amplitude comparison angle measurement process that measures the angle from the ratio of the amplitude value of the received signal obtained by changing the output angle of the radio wave, and at the same time, two types of beam patterns called a Σ beam pattern and a Δ beam pattern are formed. A method called monopulse angle measurement that obtains an azimuth and elevation angle by performing angle measurement processing has been put into practical use. A radar device that can obtain three-dimensional information such as distance information, azimuth information, and altitude information is called a three-dimensional radar device.

  In addition, a radar apparatus that obtains information related to a target continuously at predetermined time intervals by repeatedly performing transmission processing for transmitting radio waves while scanning a space to be observed has been put into practical use.

  In the case of the above three-dimensional radar apparatus, the accuracy of altitude information is greatly reduced due to the presence of multipath. FIG. 13 is a diagram for explaining multipath. The radio wave transmitted from the radar device is reflected by the target and received again by the radar device. At this time, there are a path in which the radio wave reflected by the target is further reflected by the ground or the sea surface and received, and a path that is received directly without being reflected by the ground or the like. Therefore, the radar apparatus may measure a radio wave on which a radio wave with a different path is superimposed even if it is a radio wave reflected from the target. I mentioned earlier that altitude is calculated from the elevation angle, but if the path is different, it means that the elevation angle is different, so if you do not calculate the altitude considering the existence of multipath properly, a large error will occur. .

  In addition, the influence of the multipath varies depending on the positional relationship between the target, the ground, the sea surface, etc., the frequency, weather conditions, etc. with respect to the radar apparatus. For this reason, as a general countermeasure against multipath, off-bore sight beam scanning that controls the elevation angle so that the beam does not irradiate the ground or the sea surface as much as possible, or received signals with different multipath effects by changing the transmission frequency Frequency diversity is performed to reduce the effect by combining

  However, off-bore sight beam scanning has the disadvantage that the target signal from a low elevation target near the ground or sea surface is weakened. On the other hand, frequency diversity has restrictions on the Radio Law for using a plurality of transmission frequencies.

  As another method, there is a method of reducing the influence of multipath by smoothing after the tracking process. However, the tracking process requires detection data of a plurality of scans. Further, since this coping method is based on the assumption that the influence of multipath due to the movement of the target is a change, it takes time for the change to occur. For this reason, it takes time to obtain altitude information with high accuracy.

  Therefore, Japanese Patent No. 3353991 proposes a radar apparatus that analytically removes the influence of multipath and calculates the angle of a direct wave. FIG. 14 is a schematic configuration diagram of a radar apparatus in Japanese Patent No. 3353991.

  The transmitter 102 generates a transmission pulse and outputs it to the aerial line 901, whereby radio waves are transmitted from the aerial line 901 to the space. Here, the antenna 901 forms a Σ beam pattern and a Δ beam pattern in the elevation direction as a monopulse system.

  On the other hand, the reflected wave is received by the antenna 901. The high-frequency received signal obtained by reception is A / D converted by the transceiver 902 and output to the signal processor 903 as a digital received signal. The signal processor 903 performs signal processing such as suppression of interference signals and suppression of unnecessary signals such as reflected signals from the ground and the sea surface.

  The received signal subjected to signal processing in this way is compared with a threshold value in the target signal detector 904, and a received signal having an amplitude equal to or larger than the threshold value is determined to be the target signal. Then, the amplitude value of the corresponding Σ beam pattern and the amplitude value of the Δ beam pattern are extracted, and using this, the complex divider 905 calculates Δ / Σ.

  The circle center calculator 906 uses Δ / Σ to calculate the radius of the circular locus 900 drawn on the complex plane as shown in FIG. 15 and its center coordinates. The angle converter 907 calculates the arrival angle of the direct wave from the radius and the center coordinates.

  This radar apparatus uses the characteristic that the value of Δ / Σ draws a circular locus as shown in FIG. 15 in a multipath environment. Therefore, in order to perform highly accurate angle measurement in a multipath environment, it is necessary to obtain the circular locus 900 with high accuracy.

  Therefore, radio waves having the same frequency are transmitted at certain intervals, and detected data is detected by observing three or more times. Then, the circle locus 900 is accurately obtained by obtaining three or more different Δ / Σ coordinates on the complex plane corresponding to the detection data.

  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 a change in the distance between the target and the observation point. By keeping the time interval of each observation to some extent, the observation points on the complex plane become observation points 901a, 901b, and 901c in FIG. 15, and are plotted in a positional relationship apart from each other. For this reason, the circular locus 900 can be obtained with high accuracy from the coordinates of each observation point.

  However, when the time interval of each observation is shortened, the observation points 901d, 901e, and 901f on the complex plane come closer to each other, so that it is difficult to accurately obtain the circular locus 900.

  Therefore, in order to obtain the circular locus 900 with high accuracy, the target needs to move to some extent during observation, and thus observation over a plurality of scans is required. That is, in this technique, it is necessary to observe a target such as a target aircraft for a long time in order to obtain altitude information from which the influence of multipath is removed.

Japanese Patent No. 3353991

  However, in the method according to Japanese Patent No. 3353991, there is a problem that a scan must be performed a plurality of times and observation must be performed for a long time in order to obtain an altitude with reduced multipath effects.

  That is, the method according to Japanese Patent No. 3353991 uses a change in the relative phase difference φ between the direct wave and the indirect wave due to a change in the distance of the moving target. 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 by observation points 901a, 901b, and 901c in FIG. Therefore, the circular locus 900 can be obtained with high accuracy from the coordinates of these observation points.

  However, when the time interval of each observation becomes short, each point approaches like observation points 901d, 901e, and 901f on the complex plane, so that it is difficult to accurately obtain the circular locus 900. Therefore, in order to obtain the circular locus 900 with high accuracy, the target needs to move to some extent during observation, and observation over a plurality of scans is necessary.

  Therefore, a main object of the present invention is to provide a radar apparatus and a flying object elevation angle calculation method capable of acquiring altitude information with high accuracy even in a multipath environment.

In order to solve the above-described problem, an invention relating to a radar apparatus for detecting a target receives beams of the same direction at different elevation angles that have been reflected by the target and the beam nose angle of the beam is the first nose angle and the beam A reception signal with a second nose angle different from the first nose angle is output, and a plurality of reception signals with a beam with a first nose angle are received at that time, a plurality of reception signals with a beam with a first nose angle and a beam with a second nose angle A DBF antenna that outputs a signal as a second group received signal, and amplitude data of a signal based on an incoming wave from the same target is output as first amplitude data based on the received signal included in the first group received signal, and the second group A processing unit that detects and outputs amplitude data of a signal based on an incoming wave from the same target as second amplitude data based on a received signal included in the received signal; The target elevation angle is calculated as the first elevation angle based on the width data, the target elevation angle is calculated as the second elevation angle based on the second amplitude data, and the amount of change between the first nose angle and the second nose angle; A multipath angle measurement processor that compares the amount of change between the first elevation angle and the second elevation angle, and determines a target elevation angle from an elevation angle relationship established according to the comparison result. .
In addition, the invention according to the flying object elevation angle calculation method for detecting a target receives a beam in the same direction with different elevation angle directions that are reflected by the target and the beam nose angle of the beam is the first nose angle and the first nose angle. A reception signal having a second nose angle different from the nose angle is output, and at this time, a plurality of reception signals by the beam of the first nose angle are converted into a first group reception signal, and a plurality of reception signals by the beam of the second nose angle are output. Based on the transmission / reception procedure output as the second group received signal and the received signal included in the first group received signal, the amplitude data of the signal from the same target is output as the first amplitude data, and the second group received signal An amplitude data detection procedure for detecting and outputting the amplitude data of a signal based on an incoming wave from the same target as the second amplitude data based on the received signal included in the first target; And calculating the target elevation angle as the first elevation angle based on the second amplitude data, calculating the target elevation angle as the second elevation angle based on the second amplitude data, and the amount of change between the first nose angle and the second nose angle, A multi-pass angle measurement procedure for comparing the amount of change between the first elevation angle and the second elevation angle, and determining one of the first elevation angle and the second elevation angle as a target elevation angle according to the comparison result. It is characterized by including.

  According to the present invention, a highly accurate elevation angle can be derived even in a multipath environment, and the reliability of target altitude information is improved.

1 is a block diagram of a radar apparatus according to a first embodiment of the present invention. It is a detailed block diagram of a DBF antenna. It is a detailed block diagram of an amplitude data extraction unit. It is a schematic diagram of the antenna gain of a receiving beam. FIG. 5 is a diagram showing the relationship between the elevation angle of a direct wave and the beam nose, where (a) is a case where the first elevation angle and the second elevation angle of the direct wave are larger than the first nose angle, and (b) When it is smaller than the second nose angle, (c) shows a case where the first elevation angle and the second elevation angle of the direct wave are between the first nose angle and the second nose angle. It is the flowchart which showed the derivation | leading-out procedure of the elevation angle in a radar apparatus. It is a block diagram of the radar apparatus concerning 2nd Embodiment. It is the flowchart which showed the derivation | leading-out procedure of the elevation angle in a radar apparatus. It is a block diagram of the radar apparatus concerning 3rd Embodiment. It is the flowchart which showed the derivation | leading-out procedure of the elevation angle in the radar apparatus concerning 3rd Embodiment. It is a block diagram of the radar apparatus concerning 4th Embodiment. It is the flowchart which showed the derivation | leading-out procedure of the elevation angle in the radar apparatus concerning 4th Embodiment. It is a figure explaining multipath. It is a schematic block diagram of the radar apparatus applied to description of related technology. It is a figure which shows the observation point on a complex plane applied to description of a related technique.

<First Embodiment>
A first embodiment of the present invention will be described. FIG. 1 is a block diagram of a radar apparatus 2A according to the present embodiment. FIG. 6 is a diagram showing a procedure for deriving a target elevation angle by the radar apparatus 2A.

  The radar apparatus 2A includes a processing unit including a beam controller 3, an excitation signal generator 4, a digital beam forming (DBF) antenna 5, a distributor 6, a weight generator 7, a first processing unit 8a, and a second processing unit 8b. 8. A multipath angle measuring processor 9 is provided. Hereinafter, each component will be described with reference to FIG.

  Steps SA1 and SA2: First, the radar apparatus 2A generates a transmission signal and transmits a radio wave toward the target, and receives the radio wave that has arrived after being reflected by the target. Such processing is performed by the beam controller 3, the excitation signal generator 4, and the DBF antenna 5.

  That is, the beam controller 3 outputs beam control data G1 for forming a transmission beam having a predetermined shape directed in a predetermined direction with respect to the DBF antenna 5. The excitation signal generator 4 generates an excitation signal G2 and outputs it to the DBF antenna 5.

  The DBF antenna 5 receives the beam control data G1 from the beam controller 3 and the excitation signal G2 from the excitation signal generator 4.

  FIG. 2 is a detailed block diagram of such a DBF antenna 5. The DBF antenna 5 includes a plurality of antenna units 20 (20a to 20n: n is a positive integer) in which a transmission antenna and a reception antenna form one unit. Although FIG. 2 shows the antenna unit 20 in which the transmission antenna and the reception antenna are integrated, a configuration in which the transmission antenna and the reception antenna are provided separately may be employed.

  Each antenna unit 20 includes an element antenna 21, a transmission / reception switch 22, a low noise amplifier 23, an A / D converter 24, a power amplifier 25, and a phase controller 26.

  In this specification, radio waves are transmitted and received from each element antenna 21 of the plurality of antenna units 20. A radio wave transmitted and received by each element antenna 21 is referred to as “radio wave”, and a result of combining the radio waves transmitted and received from the plurality of element antennas 21 is referred to as a beam. For this reason, even when the radio wave transmitted / received from one element antenna 21 does not have directivity, the beam has directivity. In FIG. 2, the symbol Pa indicates a transmission beam, and the symbol Pb indicates a reception beam. The transmission beam Pa is formed so as to include the reception beam Pb.

  The directivity and shape of the beam are set according to the arrangement configuration (layout) of the plurality of element antennas 21, the phase of the radio wave output from each element antenna 21, and the like. Information for setting the phase of the radio wave is included in the beam control data G 1 from the beam controller 3. The excitation signal G2 from the excitation signal generator 4 is modulated based on the beam control data G1, and the radio wave output from each element antenna 21 forms a beam Pa having a predetermined shape having directivity in a predetermined direction. .

  Specifically, the phase controller 26 modulates the phase of the excitation signal G2 based on the beam control data G1 to generate a transmission signal. By this phase modulation, the shape and directivity of the beam constituted by the radio wave output from each element antenna 21 are set. The power amplifier 25 amplifies the power of the transmission signal thus modulated.

  The transmission / reception switch 22 performs circuit control so that a transmission signal is output from the power amplifier 25 to the element antenna 21 during transmission, and performs circuit control so that a reception signal is output from the element antenna 21 to the low noise amplifier 23 during reception. .

  The element antenna 21 transmits a radio wave to the space when transmitting, and receives the radio wave when receiving. The received signal is output to the low noise amplifier 23 via the transmission / reception switch 22. The element antenna 21 has a configuration in which a plurality of element antennas 21 are arranged in parallel in the elevation direction in order to obtain a predetermined elevation beam, but may be a subarray antenna. Further, the synthesis in the azimuth direction may be either RF synthesis or digital synthesis.

  The low noise amplifier 23 amplifies the received signal, and the A / D converter 24 converts the amplified received signal into a digital signal. The digital reception signal G3 is output to the distributor 6. Since this reception signal G3 is output from each antenna unit 20, in the case of N antenna units 20, N reception signals G3 are obtained.

  Step SA3: The distributor 6 distributes each received signal G3 to the first processing unit 8a and the second processing unit 8b of the processing unit 8. As shown in FIG. 1, each of the first processing unit 8a and the second processing unit 8b includes four amplitude data extraction units 31. For this reason, the distributor 6 distributes the reception signal G3 from one antenna unit 20 into eight and outputs the signal to each amplitude data extraction unit 31. Accordingly, the reception signal G3 from each antenna unit 20 is input to each amplitude data extraction unit 31. That is, when N antenna units 20 are provided, eight received signals G3 are input to each amplitude data extraction unit 31. Hereinafter, the four received signals distributed to the first processing unit 8a are collectively referred to as a first group received signal G3_a, and the four received signals distributed to the second processing unit 8b are collectively referred to as a second. This is described as a group reception signal G3_b.

  Step SA4: Next, synthesis processing, gain adjustment processing, and unnecessary signal processing are performed on the reception signal G3 included in the first group reception signal G3_a and the second group reception signal G3_b. These processes are performed by the weight generator 7 and the processing unit 8.

  The weight generator 7 generates a weight for each reception signal G3 so that the plurality of reception signals G3 have a predetermined beam shape in the processing unit 8, and outputs this as a weight signal G6.

  The first processing unit 8a and the second processing unit 8b in the processing unit 8 include four amplitude data extraction units 31 (31a, 31b, 31c, 31d) having the same configuration. As shown in FIG. 3, the amplitude data extraction unit 31 includes a DBF processor 33, a gain corrector 34, an unnecessary signal processor 35, and a target detection processor 36.

  The DBF processor 33 receives the first group received signal G3_a and the second group received signal G3_b via the distributor 6 and the weight signal G6 from the weight generator 7. Therefore, the DBF processor 33 waits for the N received signals G3 constituting the first group received signal G3_a received from the DBF antenna 5 via the distributor 6 so as to obtain a predetermined beam in the elevation direction. By performing the weighting by G6, signals (reception beam signals) having the same beam nose elevation angle and different beams are formed.

  The gain corrector 34 corrects the reception beam signal from the DBF processor 33 so that the antenna gain becomes a predetermined value.

  The unnecessary signal processor 35 suppresses interference signals and unnecessary signals such as reflected signals from the ground or the sea surface with respect to the received beam signal corrected from the gain corrector 34 (unnecessary signal processing).

  Steps SA5 and SA6: The target detection processor 36 specifies a signal based on the target from the received beam signal that has undergone the synthesis process, gain adjustment process, and unnecessary signal process, and outputs the amplitude data G7. Accordingly, four pieces of amplitude data (hereinafter referred to as first amplitude data) are output from the first processing unit 8a, and four pieces of amplitude data (described as second amplitude data) are output from the second processing unit 8b. Is done. The first amplitude data is denoted as G7_a, and the second amplitude data is denoted as G7_b.

  In FIG. 1, the target signal specifying command G5 is output from the amplitude data extraction unit 31a to the other amplitude data extraction units 31b to 31d. This target signal specifying command G5 is such that the four amplitude data extraction units 31a to 31d detect the reception signal G3 from the same target and output the amplitude data G7 based on the detected reception signal G3. It is a command to secure. That is, the target signal specifying command G5 is output so that the other amplitude data extraction units 31b to 31d detect signals having the same distance as the signals detected by the amplitude data extraction unit 31a as reception signals from the same target. Since the four amplitude data extraction units 31 only need to extract the amplitude data of the received signal G3 from the same target, any one of the amplitude data extraction units 31a to 31d is used as the target signal specifying command G5. May be output to the amplitude data extraction unit.

  The target detection processor 36 compares the unnecessary signal processed signal with a preset threshold value. A signal equal to or greater than the threshold is determined as a signal from the target (target signal), and amplitude data G7 of the signal is detected. At this time, the target detection processor 36 outputs a target signal specifying command G5 indicating the target signal to the target detection processor 36 of the other amplitude data extraction unit 31. The target detection processor 36 of the other amplitude data extraction unit 31 does not perform target signal determination processing, detects signals having different beams at the same beam nose elevation angle indicated by the target signal specifying command G5, and outputs the amplitude data G7. Output. Whether or not the signal is a target signal is determined by specifying a received signal G3 having amplitude data of the same distance as the distance of the amplitude data detected by the target detection processor 36 that outputs the target signal specifying command G5. Is called. Therefore, the target signal specifying command G5 includes information regarding the distance of the amplitude data.

  Thus, the first amplitude data G7_a and the second amplitude data G7_b are output to the multipath angle measurement processor 9. Since each of the first amplitude data G7_a and the second amplitude data G7_b includes four amplitude data G7, a total of eight amplitude data G7 are input to the multipath angle measurement processor 9.

  Step SA8: The multipath angle measurement processor 9 uses the amplitude data G7 to calculate the elevation angle α of the reflected wave (direct wave) that has directly arrived after being reflected by the target based on the following principle. As shown in FIG. 13, the reflected waves that have arrived after being reflected by the target include indirect waves that have been reflected by the sea surface or the like in addition to the direct waves described above. However, there may be no object that reflects reflected waves such as the sea surface again in the vicinity, and in such a case, only direct waves are present. Therefore, an environment where direct waves and indirect waves exist is described as a multipath environment, and an environment where only direct waves exist is described as a non-multipath environment. It is assumed that the multipath angle measuring processor 9 is a signal received in a multipath environment. In this sense, the elevation angle obtained by the multipath angle measurement processor 9 is referred to as a multipath elevation angle.

First, the amplitude value Σ of the received signal G4 in a multipath environment is
Σ = {S (α) + γ · S (β) · exp (j · φ)} · k
Define in. Hereinafter, this formula is referred to as a basic formula. Here, the meaning of each symbol is as follows.
α: Elevation angle of direct wave (deviation from beam nose)
β: Elevation angle of indirect wave (deviation from beam nose)
γ: Relative amplitude ratio of indirect wave to direct wave φ: Relative phase difference of indirect wave to direct wave
S (θ): Antenna gain at elevation angle θ k: Value depending on target distance j: Imaginary number

The amplitude value of the received signal G3 included in the first group receive signals G3_a outputted from the first processing unit 8a, when the Σ ₁ ~Σ _4, amplitude values Σ ₁ ~Σ ₄ of each received signal G4 from the basic equation ,
Σ ₁ = {S ₁ (α) + γ · S ₁ (β) · exp (j · φ)} · k (1)
Σ ₂ = {S ₂ (α) + γ · S ₂ (β) · exp (j · φ)} · k (2)
Σ ₃ = {S ₃ (α) + γ · S ₃ (β) · exp (j · φ)} · k (3)
Σ ₄ = {S ₄ (α) + γ · S ₄ (β) · exp (j · φ)} · k (4)
It becomes. Here, S _{1 to} S ₄ are antenna gains of beams approximated by Gaussian functions with the same beam nose elevation angle but different beam widths.

As shown in FIG. 13, the reflected waves received by the radar device include direct waves and indirect waves. The antenna gains S _{1 to} S ₄ of the reception beam corresponding to the four reception signals G4 of the direct wave and the indirect wave can be shown as in the schematic diagram of FIG.

At this time, the antenna gain of the beam such as S ₁ (θ) is
S ₁ (θ) = G · exp (−a ₁ · θ ² ) (5)
S ₂ (θ) = G · exp (−a ₂ · θ ² ) (6)
S ₃ (θ) = G · exp (−a ₃ · θ ² ) (7)
S ₄ (θ) = G · exp (−a ₄ · θ ² ) (8)
Can be written. Here, G is a coefficient indicating the gain of the beam, and is corrected by the gain corrector 34 (see FIG. 3) so that the antenna gains of the four beams have the same value.

Solving Equation (1) to Equation (4) for the term γ · exp (j · φ)
γ · exp (j · φ) = {Σ ₁ / k−S ₁ (α)} / S ₁ (β) (9)
γ · exp (j · φ) = {Σ ₂ / k−S ₂ (α)} / S ₂ (β) (10)
γ · exp (j · φ) = {Σ ₃ / k−S ₃ (α)} / S ₃ (β) (11)
γ · exp (j · φ) = {Σ ₄ / k−S ₄ (α)} / S ₄ (β) (12)
It becomes.

Therefore, γ · exp (j · φ) is removed from Equation (9) and Equation (11), and
{Σ ₁ / k−S ₁ (α)} / S ₁ (β) = {Σ ₃ / k−S ₃ (α)} / S ₃ (β) (13)
Get.

When this equation (13) is modified and the equations (5) and (7) are used, the following equation (14) is obtained.
{Σ ₁ / k-S ₁ (α)} / {Σ ₃ / k-S ₃ (α)}
= S ₁ (β) / S ₃ (β)
= exp {-(a ₁ -a ₃ ) β ² } (14)

Similarly, the following equation (15) is obtained from the equations (10), (12), (6), and (8).
{Σ ₂ / k-S ₂ (α)} / {Σ ₄ / k-S ₄ (α)}
= S ₂ (β) / S ₄ (β)
= exp {-(a ₂ -a ₄ ) β ² } (15)

Furthermore, the following equation (16) is obtained from the equations (10), (11), (6), and (7).
{Σ ₂ / k-S ₂ (α)} / {Σ ₃ / k-S ₃ (α)}
= S ₂ (β) / S ₃ (β)
= exp {-(a ₂ -a ₃ ) β ² } (16)

here,
a ₁ -a ₃ = a ₂ -a ₄ = a ₂ -a ₃ ≠ 0 (17)
When deciding _a 1 ~a ₄ so that relationship is established,
{Σ ₁ / k-S ₁ (α)} / {Σ ₃ / k-S ₃ (α)}
= {Σ ₂ / k−S ₂ (α)} / {Σ ₄ / k−S ₄ (α)}
= {Σ ₂ / k−S ₂ (α)} / {Σ ₃ / k−S ₃ (α)} (18)
Is obtained.

And if k is deleted from equation (18),
(Σ ₁・ Σ ₄ -Σ ₂・ Σ ₃ ) / (Σ ₄・ S ₁ (α) -Σ ₁・ S ₄ (α) -Σ ₃・ S ₂ (α) -Σ ₂・ S ₃ (α) )
= (Σ ₂・ Σ ₃ -Σ ₂・ Σ ₄ ) / (Σ ₃・ S ₁ (α) -Σ ₂・ S ₃ (α) -Σ ₄・ S ₂ (α) -Σ ₂・ S ₄ (α ))… (19)
It becomes.

When this equation (19) is transformed and arranged,
A · S ₁ (α) + B · S ₂ (α) + C · S ₃ (α) + D · S ₄ (α) ≡G · F (α) = 0 (20)
It becomes. Where A = Σ ₂ · Σ ₃ · Σ ₄ −Σ ₂ · Σ ₄ ² (21)
B = -Σ ₁・ Σ ₃・ Σ ₄ + Σ ₁・ Σ ₄ ² (22)
C = Σ ₂ ² · Σ ₄ -Σ ₁ · Σ ₂ · Σ ₄ (23)
D = Σ ₁ · Σ ₂ · Σ ₃ −Σ ₂ ² · Σ ₃ (24)
F (θ) = A · exp (−a ₁ · θ ² ) + B · exp (−a ₂ · θ ² ) +
C · exp (−a ₃ · θ ² ) + D · exp (−a ₄ · θ ² ) (25)
It is.

A, B, C, and D are values calculated from the amplitude value of the reception signal G4 of each beam. a ₁ , a ₂ , a ₃ , and a ₄ are constants determined in advance by design, and the elevation angle α of the direct wave can be obtained by using a numerical analysis method such as Newton's method for Equation (25). It is.

  The elevation angle α of the direct wave obtained by the equation (25) is an absolute value of the deviation from the beam nose, and it remains undecided as to whether it is above or below the beam nose in the elevation angle direction. Therefore, it is necessary to determine the true elevation angle by determining whether the beam nose is above or below (see FIG. 5).

Therefore, in order to determine whether the direct wave is above or below the beam nose, another set of four reception beams having different beam noses is formed, and the same processing of equations (1) to (25) is performed. . That is, the elevation angle (hereinafter referred to as the first elevation angle α ₁ ) is obtained according to the equations (1) to (25) based on the four amplitude data G7_a from the first processing unit 8a, and the four amplitudes from the second processing unit 8b. Based on the data G7_b, the elevation angle (hereinafter referred to as the second elevation angle α ₂ ) is obtained according to the equations (1) to (25).

Now, the elevation angle of the beam nose is defined as a first nose angle φ ₁ and a second nose angle φ ₂ . At this time, the relationship between the elevation angles φ ₁ and φ _{2 of} the beam nose and the first elevation angle α ₁ and the second elevation angle α ₂ of the direct wave can be divided into three cases as shown in FIG. Note that φ ₁ > φ ₂ .

5A shows the case where the first elevation angle α ₁ and the second elevation angle α ₂ of the direct wave are larger than the first nose angle φ ₁ (case 1), and FIG. 5B shows the first elevation angle α of the direct wave. _{When 1} and the second elevation angle α ₂ are smaller than the second nose angle φ ₂ (case 2), in FIG. 5C, the first elevation angle α ₁ and the second elevation angle α ₂ of the direct wave are the first nose angle φ _1. when shows (case 3) when between the second nose angle phi _2.

Case 1 Case 3 is a case divided and the amount of change in the second elevation to the first elevation angle, the magnitude relation between the second nose angle phi ₂ of the variation with respect to the first nose angle phi _1. However, mathematically, the following expressions (26) to (28) are expressed to reflect that the first elevation angle, the second elevation angle, the first nose angle, and the second nose angle have positive and negative values. it can.
Case 1: φ ₁ -φ ₂ = α ₂ -α ₁ (26)
Case 2: φ ₁ -φ ₂ = α ₁ -α ₂ (27)
Case 3: φ ₁ −φ ₂ = α ₁ + α ₂ (28)

  Therefore, the elevation angle α of the direct wave can be specified by determining which relational expression of Expressions (26) to (28) holds. That is, the elevation angle α of the direct wave can be obtained, and this elevation angle α is a multipath elevation angle.

  As described above, the multipath angle measurement processor 9 uses the first amplitude data and the second amplitude data to calculate the elevation angle of the direct wave according to the elevation angle calculation principle under the multipath environment. Therefore, since the method according to the present embodiment does not require scanning, the method for obtaining the elevation angle based on detection data obtained by performing scanning a plurality of times can be performed in a short time and with high accuracy while reducing the size of the apparatus. The elevation angle can be measured.

Second Embodiment
Next, a second embodiment of the present invention will be described. In addition, about the same structure as 1st Embodiment, description is abbreviate | omitted suitably using the same code | symbol.

  The angle measurement processing in a multipath environment may increase the calculation processing load. However, generally, since multipath occurs locally, it is not necessary to perform angle measurement processing in a multipath environment for the entire region. That is, there is a case where radio waves reflected by the sea surface or the like are not received. Therefore, in this embodiment, multipath angle measurement processing is performed in a multipath environment, and normal amplitude comparison angle measurement processing is performed in a non-multipath environment where no multipath exists, thereby reducing the processing load. Plan.

  Here, the normal amplitude comparison angle measurement process is a known amplitude comparison angle measurement process as described in the background section. The elevation angle obtained by the amplitude comparison angle measurement process is referred to as an amplitude comparison elevation angle.

  FIG. 7 is a block diagram of the radar apparatus 2B according to the present embodiment. The radar apparatus 2B according to the present embodiment has a multipath environment or a non-multipath environment in which an amplitude comparison angle measurement processor 11 and a selector 12 are added to the radar apparatus 2A shown in FIG. The angle measurement process is changed according to whether it is.

  FIG. 8 is a flowchart showing a procedure for deriving an elevation angle in the radar apparatus 2B. Note that steps SB1 to SB7 in FIG. 8 are the same as steps SA1 to SA7 in FIG.

    Step SB8: Assuming that the received signal is a signal under a multipath environment, the multipath angle measurement processor 9 determines the elevation angle.

  Step SB9: On the other hand, if the user indicates that the signal is not in a multipath environment, the process proceeds from step SB6 to step SB9. Then, the amplitude comparison angle measurement processor 11 calculates an amplitude comparison elevation angle based on the first and second amplitude data.

  Therefore, when the user instructs the multipath environment, the multipath elevation processor 9 described in the first embodiment obtains the multipath elevation angle, and when the user instructs the nonpath environment. The amplitude comparison elevation angle processor 11 determines the amplitude comparison elevation angle. Therefore, the selector 12 outputs the multipath elevation angle from the multipath angle measurement processor 9 or the amplitude comparison elevation angle from the amplitude comparison angle measurement processor 11 according to the user instruction.

  In the above description, the amplitude comparison angle measurement processor 11 and the multipath angle measurement processor 9 have been described as being operated in parallel regardless of whether or not they are in a multipath environment. Also good. That is, the multipath angle measurement processor 9 operates in the multipath environment, and the amplitude comparison angle measurement processor 11 operates in the non-multipath environment.

  As a result, even if the angle measurement processing load in the multipath environment increases, the elevation angle of the direct wave can be specified in the multipath environment while suppressing an increase in the hardware scale.

<Third Embodiment>
Next, a third embodiment of the present invention will be described. In addition, about the same structure as each embodiment mentioned above, description is abbreviate | omitted suitably using the same code | symbol.

  FIG. 9 is a block diagram of the radar apparatus 2C according to the present embodiment. The processing unit 8 of the radar apparatus in each embodiment described so far includes the first processing unit 8a and the second processing unit. In contrast, in the present embodiment, the storage unit 8c is provided in the processing unit 8, and the second processing unit is omitted.

  A processing procedure in the radar apparatus 2C having such a configuration is shown in FIG. In FIG. 10, Steps SC1 to SC3, Steps SC5 to SC8, Steps SC10 to SC14 are the same as Steps SB1 to SB7 shown in FIG. That is, as a processing procedure for calculating the elevation angle according to the present embodiment, Step SC4 and Step SC9 are different from the processing so far.

  Step SC4: That is, in the embodiments so far, the first multipath elevation angle and the second multipath elevation angle are calculated by parallel processing, but in this embodiment, the first multipath elevation angle and the second multipath elevation angle are Calculate by sequential processing. Therefore, the second group received signal G3_b for calculating the second multipath elevation angle is temporarily stored in the storage unit 8c until the calculation of the first multipath elevation angle is completed.

  Step SC9: Then, when the first amplitude data G7_aG7_a is detected based on the first group received signal G3_a and outputted to the multipath angle measuring device 9, the second group received signal G3_b stored in the storage unit 8c. Is output to the first processing unit 8a via the distributor 6. During this time, the multipath angle measurement processor 9 calculates the first multipath elevation angle using the first amplitude data G7_aG7_a.

  The first processing unit 8a detects the second amplitude data G7_b based on the input second group received signal G3_b, and the multipath angle measuring processor 9 uses the second amplitude data G7_b to perform the second multipath. Calculate the elevation angle.

  Thereby, since the first multipath elevation angle and the second multipath elevation angle are aligned, the multipath angle measurement processor 9 specifies and derives the multipath elevation angle from the relationship between the first nose angle and the second nose angle.

  As described above, by providing the storage unit instead of the second processing unit, the multipath elevation angle can be calculated, and the radar apparatus can be downsized.

<Fourth embodiment>
Next, a fourth embodiment of the present invention will be described. In addition, about the same structure as each embodiment mentioned above, description is abbreviate | omitted suitably using the same code | symbol.

  In the second embodiment and the third embodiment, the user has instructed whether or not it is a multipath environment. In contrast, in the present embodiment, it is automatically determined whether or not a multipath environment is set.

  FIG. 11 is a block diagram of the radar apparatus 2D according to the present embodiment. As shown in the figure, the radar device 2D is additionally provided with a tracking processor 14 and a multipath angle measurement processing controller 15 with respect to the radar device 2C shown in FIG.

  FIG. 12 is a diagram showing a processing procedure of the radar apparatus 2D. In FIG. 12, steps SD1 to SD3, steps SD5 to SD8, and steps SD11 to SD17 are the same as steps SB1 to SB8 shown in FIG. That is, as a processing procedure for calculating the elevation angle according to the present embodiment, step SD4, step SD9, and step SD10 are different from the processing so far.

  Generally, in the target tracking process, the altitude is calculated from the elevation angle of the target, and the calculated altitude is smoothed to obtain the target altitude. However, if multipath exists, the target altitude varies greatly before and after smoothing. Therefore, in the present embodiment, whether the environment is a multipath environment or a non-multipath environment is determined according to the amount of change in altitude before and after the smoothing process.

    Step SD4: The reception signal G3 from the DBF antenna 5 is input to the first processing unit 8a, and reception signals of beams having different beam noses are temporarily stored in the storage unit 8c. Then, the first processing unit 8a detects the amplitude data G7 from the received signal, and the amplitude comparison angle measurement processor 11 calculates the amplitude comparison elevation angle by a known elevation angle calculation method using the amplitude data G7 (steps SD5 to SD5). Step SD8).

  Step SD9: The tracking processor 14 calculates the target altitude using the amplitude comparison elevation angle from the amplitude comparison angle measurement processor 11 and outputs it to the multipath angle measurement processing controller 15. The multipath angle measurement processing controller 15 performs high-level smoothing processing. Hereinafter, the altitude before the smoothing process is referred to as the pre-smoothing altitude, and the altitude after the smoothing process is referred to as the post-smoothing altitude.

  Step SD10: When the multipath angle measurement processing controller 15 obtains the smoothing processing height, it determines whether or not the amount of change from the pre-smoothing height is larger than a preset threshold value. If the amount of change is larger than the threshold, it is determined that the altitude accuracy is reduced due to the effect of multipath because it is in a multipath environment. to decide.

  The multipath angle measurement controller 15 instructs the selector 12 to output the amplitude comparison elevation angle from the amplitude comparison angle measurement processor 11 when the change amount is smaller than the threshold value.

  On the other hand, the multipath angle measurement processing controller 15 causes the first processing unit 8a to output the second group reception signal stored in the storage unit 8c via the weight generator 7. Thereby, the first processing unit 8a detects the second amplitude data based on the second group reception signal G3_b. The multipath angle measurement processor 9 calculates the multipath elevation angle according to the elevation angle calculation principle using the first amplitude data and the second amplitude data, and outputs the multipath elevation angle to the selector 12 (steps SD11 to SD15).

  The selector 12 receives from the multipath angle measurement processing controller 15 so as to output the multipath elevation angle. Accordingly, the selector 12 outputs the multipath elevation angle from the multipath angle measurement processor 9 (steps SD16 and SD17).

  As described above, it is possible to automatically determine whether or not it is a multipath area, and to change the elevation angle calculation method according to the determination result, so that an appropriate elevation angle calculation method can be selected while suppressing an increase in hardware. Thus, the elevation angle calculation load is reduced and altitude accuracy is improved.

A part or all of the above embodiment can be described as in the following supplementary notes, but is not limited thereto.
<Appendix 1>
A radar device for detecting a target,
Receiving a beam in the same direction with different elevation azimuths reflected by the target, outputting a received signal having a beam nose angle of the beam different from the first nose angle and the first nose angle; and A DBF antenna that outputs a plurality of received signals by the first nose angle beam as a first group received signal and a plurality of received signals by the second nose angle beam as a second group received signal,
Based on the received signal included in the first group received signal, the amplitude data of the signal based on the incoming wave from the same target is output as first amplitude data, and based on the received signal included in the second group received signal A processing unit for detecting and outputting the amplitude data of the signal of the incoming wave from the same target as the second amplitude data;
The target elevation angle is calculated as a first elevation angle based on the first amplitude data, and the target elevation angle is calculated as a second elevation angle based on the second amplitude data, so that the first nose angle and the second nose angle are calculated. A change amount with respect to an angle and a change amount between the first elevation angle and the second elevation angle are compared, and one of the first elevation angle and the second elevation angle is set to the target elevation angle according to the comparison result. And a multipath angle measuring processor for determining the radar device.
<Appendix 2>
The radar apparatus according to appendix 1, wherein
The processing unit is
A first processing unit for detecting the first amplitude data from the received signal included in the first group received signal;
A radar apparatus comprising: a second processing unit that has the same configuration as the first processing unit and detects the second amplitude data from the received signal included in the second group received signal.
<Appendix 3>
The radar apparatus according to appendix 1, wherein
The processing unit is
A storage unit for temporarily storing the second group received signal;
The first group received signal from the DBF antenna is received, the first amplitude data is detected from the first group received signal, and the second group received signal stored in the storage unit is captured. A radar apparatus comprising: a first processing unit that detects the second amplitude data from the second group received signal.
<Appendix 4>
The radar apparatus according to attachment 3, wherein
The first processing unit includes four amplitude data detection units, and one of the amplitude data detection units outputs a target signal specifying command for specifying a signal based on the incoming wave from the target to the other amplitudes. A radar apparatus that outputs to a data detection unit and detects the first amplitude data and the second amplitude data.
<Appendix 5>
The radar apparatus according to attachment 2, wherein
The second processing unit includes four amplitude data detection units, and one of the amplitude data detection units outputs a target signal specifying command for specifying a signal based on the incoming wave from the target to the other amplitudes. A radar apparatus that outputs to a data detection unit and detects the first amplitude data and the second amplitude data.
<Appendix 6>
The radar apparatus according to any one of appendices 1 to 5,
An amplitude comparison angle measurement processor that calculates the elevation angle of the target based on the amplitude data from the processing unit, assuming that the incoming wave received by the DBF antenna has arrived directly from the target;
A selector that selects and outputs either the elevation angle output from the multipath angle measurement processor or the elevation angle output from the amplitude comparison angle measurement processor; Radar device.
<Appendix 7>
The radar apparatus according to appendix 6, wherein
A tracking processor that takes the elevation angle from the amplitude comparison angle measurement processor and calculates the altitude of the target;
The altitude calculated by the tracking processor is smoothed, and when the amount of change before and after the smoothing is greater than a preset threshold, it is determined that multipath exists and the multipath angle measuring processor The selector is instructed to output an elevation angle, and when the amount of change before and after the smoothing is smaller than the threshold, it is determined that there is no multipath in the incoming wave, and the amplitude comparison angle measurement processor And a multipath angle measurement controller that instructs the selector to output the elevation angle.
<Appendix 8>
A flying object elevation angle calculation method for detecting a target,
Receiving a beam in the same direction with different elevation azimuths reflected by the target, outputting a received signal having a beam nose angle of the beam different from the first nose angle and the first nose angle; and A transmission / reception procedure for outputting a plurality of reception signals based on the first nose angle beam as a first group reception signal and a plurality of reception signals based on the second nose angle beam as a second group reception signal.
Based on the received signal included in the first group received signal, the amplitude data of the signal based on the incoming wave from the same target is output as first amplitude data, and based on the received signal included in the second group received signal An amplitude data detection procedure for detecting and outputting the amplitude data of the signal from the same wave from the same target as the second amplitude data;
The target elevation angle is calculated as a first elevation angle based on the first amplitude data, and the target elevation angle is calculated as a second elevation angle based on the second amplitude data, so that the first nose angle and the second nose angle are calculated. A change amount with respect to an angle and a change amount between the first elevation angle and the second elevation angle are compared, and one of the first elevation angle and the second elevation angle is set to the target elevation angle according to the comparison result. And a multi-pass angle measuring procedure for determining the flying object elevation angle.
<Appendix 9>
The flying object elevation angle calculating method according to appendix 8,
The amplitude data detection procedure includes:
A first amplitude data detection procedure for detecting the first amplitude data from the received signal included in the first group received signal;
And a second amplitude data detection procedure for detecting the second amplitude data from the received signal included in the second group received signal in the same procedure as the first amplitude data detecting procedure. The flying object elevation angle calculation method.
<Appendix 10>
The flying object elevation angle calculating method according to appendix 8,
The amplitude data detection procedure includes:
A storage procedure for temporarily storing the second group received signal;
The first group reception signal from the transmission / reception procedure is received, the first amplitude data is detected from the first group reception signal, and the second group reception signal stored in the storage procedure is captured. And a first amplitude data detection procedure for detecting the second amplitude data from the second group received signal.
<Appendix 11>
The flying object elevation angle calculation method according to any one of appendices 8 to 10,
An amplitude comparison angle measurement procedure for calculating an elevation angle of the target based on the amplitude data from the amplitude data detection procedure, assuming that the incoming wave received by the transmission / reception procedure has directly arrived from the target;
A flying object comprising: a selection procedure for selecting and outputting either the elevation angle output from the multipath angle measurement procedure or the elevation angle output from the amplitude comparison angle measurement procedure Elevation angle calculation method.
<Appendix 12>
A flying object elevation angle calculating method according to appendix 11,
A tracking process procedure for calculating the target altitude by taking the elevation angle from the amplitude comparison angle measurement procedure;
When the altitude calculated by the tracking processing procedure is smoothed and the amount of change before and after the smoothing is larger than a preset threshold, it is determined that multipath exists and the elevation angle from the multipath angle measurement procedure is determined. Is output, and when the amount of change before and after smoothing is smaller than the threshold, it is determined that there is no multipath in the incoming wave, and the amplitude comparison angle measurement procedure A flying object elevation angle calculation method comprising: a multipath angle measurement processing control procedure for instructing the selection procedure to output an elevation angle.

2A to 2D Radar device 3 Beam controller 4 Excitation signal generator 5 DBF antenna 6 Divider 7 Weight generator 8 Processing unit 8a First processing unit 8b Second processing unit 8c Storage unit 9 Multipath angle measurement processor 11 Amplitude comparison Angle measurement processor 12 Selector 14 Tracking processor 15 Multipath angle measurement processing controller 20 (20a to 20n) Antenna unit 21 Element antenna 22 Transmission / reception switch 23 Low noise amplifier 24 A / D converter 25 Power amplifier 26 Phase control 31 (31a to 31d) Amplitude data extraction unit 33 DBF processor 34 Gain corrector 35 Unnecessary signal processor 36 Target detection processor

Claims (12)

A radar device for detecting a target,
Receiving a beam in the same direction with different elevation azimuths reflected by the target, outputting a received signal having a beam nose angle of the beam different from the first nose angle and the first nose angle; and A DBF antenna that outputs a plurality of received signals by the first nose angle beam as a first group received signal and a plurality of received signals by the second nose angle beam as a second group received signal,
Based on the received signal included in the first group received signal, the amplitude data of the signal based on the incoming wave from the same target is output as first amplitude data, and based on the received signal included in the second group received signal A processing unit for detecting and outputting the amplitude data of the signal of the incoming wave from the same target as the second amplitude data;
The target elevation angle is calculated as a first elevation angle based on the first amplitude data, and the target elevation angle is calculated as a second elevation angle based on the second amplitude data, so that the first nose angle and the second nose angle are calculated. A change amount with respect to an angle and a change amount between the first elevation angle and the second elevation angle are compared, and one of the first elevation angle and the second elevation angle is set to the target elevation angle according to the comparison result. And a multipath angle measuring processor for determining the radar device. The radar apparatus according to claim 1,
The processing unit is
A first processing unit for detecting the first amplitude data from the received signal included in the first group received signal;
A radar apparatus comprising: a second processing unit that has the same configuration as the first processing unit and detects the second amplitude data from the received signal included in the second group received signal. The radar apparatus according to claim 1,
The processing unit is
A storage unit for temporarily storing the second group received signal;
The first group received signal from the DBF antenna is received, the first amplitude data is detected from the first group received signal, and the second group received signal stored in the storage unit is captured. A radar apparatus comprising: a first processing unit that detects the second amplitude data from the second group received signal. The radar apparatus according to claim 3,
The first processing unit includes four amplitude data detection units, and one of the amplitude data detection units outputs a target signal specifying command for specifying a signal based on the incoming wave from the target to the other amplitudes. A radar apparatus that outputs to a data detection unit and detects the first amplitude data and the second amplitude data. The radar apparatus according to claim 2,
The second processing unit includes four amplitude data detection units, and one of the amplitude data detection units outputs a target signal specifying command for specifying a signal based on the incoming wave from the target to the other amplitudes. A radar apparatus that outputs to a data detection unit and detects the first amplitude data and the second amplitude data. A radar apparatus according to any one of claims 1 to 5,
A monopath angle measurement processor that calculates the elevation angle of the target based on the amplitude data from the processing unit, assuming that the incoming wave received by the DBF antenna directly arrives from the target;
A radar comprising: a selector that selects and outputs either the elevation angle output from the multipath angle measurement processor or the elevation angle output from the monopath angle measurement processor. apparatus. The radar apparatus according to claim 6, wherein
A tracking processor that takes the elevation angle from the monopath angle processor and calculates the target altitude;
The altitude calculated by the tracking processor is smoothed, and when the amount of change before and after the smoothing is greater than a preset threshold, it is determined that multipath exists and the multipath angle measuring processor The selector is instructed to output an elevation angle, and when the amount of change before and after the smoothing is smaller than the threshold, it is determined that there is no multipath in the incoming wave, and the monopath angle measurement processor A radar apparatus comprising: a multipath angle measurement processing controller that instructs the selector to output the elevation angle. A flying object elevation angle calculation method for detecting a target,
Receiving a beam in the same direction with different elevation azimuths reflected by the target, outputting a received signal having a beam nose angle of the beam different from the first nose angle and the first nose angle; and A transmission / reception procedure for outputting a plurality of reception signals based on the first nose angle beam as a first group reception signal and a plurality of reception signals based on the second nose angle beam as a second group reception signal.
Based on the received signal included in the first group received signal, the amplitude data of the signal based on the incoming wave from the same target is output as first amplitude data, and based on the received signal included in the second group received signal An amplitude data detection procedure for detecting and outputting the amplitude data of the signal from the same wave from the same target as the second amplitude data;
The target elevation angle is calculated as a first elevation angle based on the first amplitude data, and the target elevation angle is calculated as a second elevation angle based on the second amplitude data, so that the first nose angle and the second nose angle are calculated. A change amount with respect to an angle and a change amount between the first elevation angle and the second elevation angle are compared, and one of the first elevation angle and the second elevation angle is set to the target elevation angle according to the comparison result. And a multi-pass angle measuring procedure for determining the flying object elevation angle. The flying object elevation angle calculation method according to claim 8,
The amplitude data detection procedure includes:
A first amplitude data detection procedure for detecting the first amplitude data from the received signal included in the first group received signal;
And a second amplitude data detection procedure for detecting the second amplitude data from the received signal included in the second group received signal in the same procedure as the first amplitude data detecting procedure. The flying object elevation angle calculation method. The flying object elevation angle calculation method according to claim 8,
The amplitude data detection procedure includes:
A storage procedure for temporarily storing the second group received signal;
The first group reception signal from the transmission / reception procedure is received, the first amplitude data is detected from the first group reception signal, and the second group reception signal stored in the storage procedure is captured. And a first amplitude data detection procedure for detecting the second amplitude data from the second group received signal. A flying object elevation angle calculation method according to any one of claims 8 to 10,
A monopath angle measurement procedure for calculating the elevation angle of the target based on the amplitude data from the amplitude data detection procedure, assuming that the incoming wave received by the transmission / reception procedure has arrived directly from the target;
A flying object elevation angle comprising: a selection procedure for selecting and outputting either the elevation angle output from the multipath angle measurement procedure or the elevation angle output from the monopath angle measurement procedure Calculation method. The flying object elevation angle calculation method according to claim 11,
A tracking process procedure for calculating the target altitude by taking the elevation angle from the monopath angle measurement procedure;
When the altitude calculated by the tracking processing procedure is smoothed and the amount of change before and after the smoothing is larger than a preset threshold, it is determined that multipath exists and the elevation angle from the multipath angle measurement procedure is determined. Is output, and when the amount of change before and after the smoothing is smaller than the threshold, it is determined that there is no multipath in the incoming wave, and the elevation angle from the monopath angle measurement procedure is determined. And a multi-pass angle measurement processing control procedure for instructing the selection procedure to output the flying object elevation angle calculation method.

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