WO2016140230A1 - Dispositif de radar - Google Patents

Dispositif de radar Download PDF

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Publication number
WO2016140230A1
WO2016140230A1 PCT/JP2016/056312 JP2016056312W WO2016140230A1 WO 2016140230 A1 WO2016140230 A1 WO 2016140230A1 JP 2016056312 W JP2016056312 W JP 2016056312W WO 2016140230 A1 WO2016140230 A1 WO 2016140230A1
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WO
WIPO (PCT)
Prior art keywords
antenna
clutter
radar
statistical model
ground surface
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PCT/JP2016/056312
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English (en)
Japanese (ja)
Inventor
田川哲也
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株式会社次世代技術研究所
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Publication of WO2016140230A1 publication Critical patent/WO2016140230A1/fr

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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
    • G01S7/00—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00
    • G01S7/02—Details of systems according to groups G01S13/00, G01S15/00, G01S17/00 of systems according to group G01S13/00
    • G01S7/28—Details of pulse systems
    • G01S7/285—Receivers
    • G01S7/32—Shaping echo pulse signals; Deriving non-pulse signals from echo pulse signals

Definitions

  • the present invention relates to a radar signal processing method and a radar apparatus that reduce clutter.
  • the conventional method can suppress the sea surface clutter mixed from the antenna main lobe, but it is difficult to apply to the sea surface clutter mixed from the antenna side lobe. Even in the same range cell, the irradiation pattern of the antenna main lobe and the irradiation pattern of the antenna side lobe are greatly different. Further, the method of reducing clutter by calculating simulated data of a range profile as in Patent Document 2 is limited in application when the weather echo from rainfall or the like is stronger than the ground surface echo. In this method, there is also a problem that the calculation result depends on assumptions such as the radar scattering cross section of the ground surface used for calculation of simulated data and the antenna gain.
  • the first invention estimates the clutter power mixed from the antenna main lobe and the antenna side lobe based on the statistics of the received signal obtained by scanning the antenna beam, and reduces the clutter.
  • the fluctuation of the antenna side lobe due to the thermal and mechanical changes of the radar is parameterized, thereby enabling more accurate clutter reduction.
  • the third aspect of the present invention it is possible to more accurately reduce clutter by specifying a clutter generation region due to an antenna irradiation pattern in terms of area and distance using a radar range resolution function and using the positional relationship.
  • the fourth invention enables more accurate clutter reduction in consideration of the strength and weakness of echoes from the ground surface observed by scanning the antenna beam due to unevenness of the ground surface and non-uniformities such as rainfall. To.
  • the radar equation representing the surface echo intensity Ps is represented by the following equation (1).
  • the positional relationship between the radar and the ground surface, and the coordinate system are shown in FIG. 1 (a radar equation representing ground surface echo is shown in Non-Patent Document 1, etc.).
  • FIG. 1 when the antenna main lobe receives an echo from the target body 5, the ground surface irradiated with the antenna side lobe from the ground surface (area S, indicated as 6) in the same range as the target body 5.
  • the echo shows that it becomes the ground clutter.
  • the strength of the ground clutter can be obtained by integrating the product of the ground surface radio wave scattering intensity (per unit area) and the antenna gain over the ground surface area S within the same range.
  • Ps (r, k) is the ground echo (mW) received from the range bin at the distance r
  • k is a number assigned for each antenna beam direction
  • Pt is the power (mW) transmitted from the radar
  • Q (r , k) is determined by antenna gain (transmission: Gt, k reception: Gr, k), transmission pulse waveform u, radar scattering cross section ⁇ 0 of the ground surface, and radio wave attenuation A in the propagation path between the radar and the ground surface.
  • the integral value, r ′ is the distance from the radar to a position on the ground surface
  • S is the ground surface at the same distance as the range bin at the position of distance r.
  • the antenna gain is expressed as a function of the incident angle ⁇ and the azimuth angle ⁇ , and any of a model, a simulation value, and an actually measured antenna gain using a Gaussian function or a sinc function can be used.
  • a model formula based on the sinc function is shown in Patent Document 1 and the like.
  • the transmission pulse waveform u any of a rectangular function, a model using a Gaussian function or a sinc function, or an actually measured pulse waveform can be used.
  • a Gaussian function it is expressed by the equation (2).
  • c is the speed of light
  • t is the -6 dB width of the transmission / reception pulse.
  • the relationship between the range cell and the antenna gain when a rectangular pulse waveform is assumed as the transmission pulse waveform u can be illustrated as shown in FIG. (Some other resolution functions may be used as the transmission pulse waveform u)
  • the range cells are the same, when the antenna gain is increased or decreased by the antenna beam scanning, the position where a strong ground echo is generated is shifted accordingly.
  • the distance at which the range cell is maximized does not necessarily match the region irradiated with the antenna side lobe.
  • the degree of coincidence between the range cell and the region irradiated by the antenna side lobe is larger.
  • the ground clutter is generated by the bottom of the transmission pulse (Equation 2) represented by a Gaussian function being applied to the ground surface. This is also true when the antenna main lobe observes the vicinity of the radar direct point.
  • the range bin in which a strong ground echo is generated is determined by the positional relationship between the range cell and the antenna gain footprint (main lobe and side lobe).
  • statistical processing is performed focusing on the positional relationship of received signals for each beam scanning, for each beam direction, and for each range bin, and clutter power is estimated to reduce ground surface clutter.
  • the radar When the radar is mounted on a platform such as an aircraft or an artificial satellite, a plurality of points are observed as shown in FIG. 3 according to the movement of the platform and beam scanning.
  • the beam pointing accuracy changes due to the thermal, electrical, and mechanical changes of the radar device. Therefore, in FIG.
  • the antenna beam is exemplified when the beam pointing accuracy is low.
  • the antenna side lobe also fluctuates due to thermal, electrical, and mechanical changes of the radar apparatus.
  • l lower-case el
  • n a range bin number
  • k a number assigned for each antenna beam direction
  • t g (l, n, k), etc.
  • fitting parameter ⁇ for the radar observation P (t) is a vector consisting of J fitting parameters ⁇ _1, ⁇ _2, ...
  • the estimated value of k can be expressed as The fitting parameter ⁇ varies depending on the fluctuation of numerical values on the system such as antenna pattern, irradiation area (depending on the range bin, antenna gain, radar and target positional relationship), ⁇ ⁇ 0 value, rainfall, etc.
  • the value of ⁇ is obtained as follows.
  • Residual M_i P (t_i) -m [t, ⁇ ] is a random variable that follows a normal distribution with expected value 0 and standard deviation ⁇ _i, and when M_i is measured independently of each other, the measured value is P (t_i) The probability p [P (t_i)] It becomes.
  • a stochastic differential equation, Bayesian estimation, maximum likelihood method, or the like is used. Substituting Equation 5 into Equation 4 gives Equation 6. Due to the unimodality of the normal distribution, the probability p [P (t_1), P (t_2), ...
  • Equation 8 P (t_I)] is When the normalized residual sum of squares V ( ⁇ ) of Equation 7 is minimum, the maximum (maximum likelihood) is obtained. At ⁇ that minimizes V ( ⁇ ), the gradient grad (V) of V becomes zero. Therefore, ⁇ is the solution of the simultaneous equations expressed by Equation 8.
  • Equation 9 The observed value P ′ (t) (true number) after the reduction of the ground surface clutter is expressed by Equation 9.
  • the beam direction k and the range bin number n correspond to the beam direction k and the distance r of the clutter power Ps (r, k) estimated. Since there are thermal, electrical and mechanical changes in the radar device including the platform to be mounted and antenna gain fluctuations, the fitting parameter ⁇ needs to be updated in a timely manner. Suppressing the factors on the system side that fluctuate ⁇ , the clutter power Ps (r, k) due to fluctuations in the observation side of the radar scattering cross section ⁇ 0 and the attenuation A on the ground surface is estimated as shown in Equation 1.
  • the radar observation P (t) is the sum of the ground surface echo, the noise power of the receiver, and the true number of meteorological echoes
  • the radar observation P (t) is replaced with the receiver noise.
  • X (t) and Y (t) can be converted into one or both of the frequencies / polarized waves.
  • X (t) is converted to ⁇ 0 (or ⁇ 0A) or echo profile converted by the radar equation (methods such as Non-Patent Document 1 and Patent Document 3).
  • ⁇ 0, Y (t) calculated based on the radar observation value P (t) [or P (t)-P_noise (k) (subtraction with an exact value, P_noise (k) is the noise power in the direction of the received beam),
  • P_noise (k) is the noise power in the direction of the received beam
  • the first embodiment of the present invention will be described based on the principle described above.
  • the beam direction k is a certain combination (for example, the radar direct direction 25 and the diagonal direction 1 as shown in FIG. 3)
  • the ratio between the antenna gain in the direct direction and the antenna gain in the diagonal direction is W_25 (t).
  • P_noise (k) at reception is an exact value
  • X (t_25) P (t_25) ⁇ P_noise (25)
  • Y (t_1) P (t_1) ⁇ P_noise (1).
  • the beam directions 25 and 1 can be freely selected from 1 to K.
  • the antenna gain ratio W (t) any of a simulation value, a theoretical value, and an actual measurement value of the antenna gain can be used.
  • the product of the transmission antenna gain: Gt, k and the reception antenna gain: Gr, k since the product of the transmission / reception antenna gain may be used as W (t). Since there is a thermal / electrical / mechanical change of the radar apparatus including the platform to be mounted and a variation of the antenna gain, the ratio of the antenna gain depends on the variable t. Further, in order to suppress the influence of temporal antenna gain fluctuations, it may be limited to observation data of adjacent beam scanning.
  • the expression representing the approximate surface by (non-linear) multiple regression analysis on the scatter diagram of FIG. 4 is the function m of Formula 3 in this embodiment (the approximate surface is a plane or a curved surface). Become).
  • the combination of k among l, n, and k at the time of observation is considered, but in the second embodiment, the combination is n (range bin).
  • n the range bin where the ground echo is maximum when the antenna main lobe is observing the direction directly below the radar.
  • the range bin used for the estimation of the side lobe clutter is n- ⁇ based on the coincidence of the concentric circle with the region irradiated by the antenna side lobe ( ⁇ is an integer).
  • t_n means the value of t when n is fixed.
  • t_ (n- ⁇ ) means the value of t when n is fixed to n- ⁇ .
  • X (t) and Y (t) may be corrected according to weather conditions (water vapor, precipitation, etc.).
  • a (nonlinear) regression analysis is performed on the scatter diagram of FIG. 5, ⁇ having the largest determination coefficient is selected, and the regression equation is the function m in the present embodiment (the regression equation is linear or nonlinear). . Since the positional relationship between the range cell and the region irradiated by the antenna side lobe changes as the platform moves, the value of ⁇ changes depending on the moving speed, the combination of the beam directions k and k ′, and the like.
  • the combination is l (scan number).
  • the (1, L-1) point or The (1, L + 1) point refers to data having a closer positional relationship.
  • the increment direction of k and the increment direction of L are not completely orthogonal.
  • t_l means the value of t when l (lowercase letter L) is fixed.
  • t_l ′ means the value of t when fixed to l ′.
  • the ground surface echo is affected by the state of the ground surface (unevenness, surface cover, lake, etc.).
  • l and l ′ each consist of a large number of scan numbers.
  • the attenuation amount A ( ⁇ , f) of the ground surface echo changes depending on the weather condition such as precipitation. Precipitation and the like are spatially non-uniform, and even if the same range cell is scanned by scanning the antenna beam, an echo emphasizing different portions in the range cell is received (Patent Document 3).
  • the range bin where the ground surface echo is maximum does not match the ground surface position by the digital elevation model (DEM) or the like. Even in such a case, the range bin offset by the integer ⁇ in the second embodiment is effective.
  • ⁇ is a real number. Since the variables l, n, and k are observed independently, Embodiments 1 to 3 can be combined with each other, and a scatter diagram matrix as shown in FIG. 6 can be created. The combination of variables in the scatterplot matrix in Fig.
  • FIG. 7 is a configuration diagram of the radar apparatus according to the first, second, and third embodiments of the present invention.
  • a pulsed radio wave 11b is transmitted from the transmitter 13b through the transmission antenna 12b, and the reflected wave 11a is received through the reception antenna 12a. This operation is performed for each polarization and each transmission / reception frequency.
  • the transmission / reception polarization is selected from horizontal / vertical polarization and right / left-hand circular polarization.
  • the frequency of radio waves to be transmitted / received is selected so that the attenuation characteristics due to water vapor, precipitation, etc. differ.
  • the receiver 13a receives the received wave and the reference signal 16 from the transmitter.
  • the transmitting / receiving antenna beam is formed by mechanical scanning, electrical scanning, digital beam forming, or the like.
  • the -6 dB width of the transmission / reception pulse in Equation 2 can be defined by the -6 dB width of the BPF output pulse waveform when the transmission pulse is input to the bandpass filter (BPF) of the receiver.
  • Radio signal transmission / reception and beam direction control are performed by the controller 15, and the signal processing device 14 performs data collection, coordinate determination, database (DEM, ground cover) reference, statistic calculation, and clutter reduction processing.
  • Equation 11 can be applied in combination with the first, second, and third embodiments of the present invention, and in particular, the degree of coincidence between the range cell directly below the radar and the irradiation region of the side lobe can be improved by the offset value ⁇ of the range bin. Equation 11 is calculated for each distance r.
  • Ps (r, k) is an observed value
  • function F is a regression equation.
  • the elements constituting the expression are different from the method using the irradiation pattern of equation (11) in Patent Document 1, the ⁇ 0 value varies. This is the same purpose in that the accuracy of clutter estimation is improved by the method of least squares.
  • This equation can be used in the same way by replacing X (t) with other converted values such as P (t), ⁇ 0A value, and radar reflection factor Z.
  • the industrial applicability of the present invention is not limited to the main lobe / antenna side lobe of the antenna, even if there is a change in the antenna irradiation pattern or radar scattering cross section, and the propagation path attenuates radio waves due to rain. Even if it occurs, it helps to reduce ground surface clutter.
  • Patent 4481078 "Radar equipment” US Patent 8138962 METHOD FOR PROCESSING MEASURED VERTICAL PROFILES OF THE POWER OF ECHOES RETURNED FOLLOWINGA TRANSMISSION OF RADAR SIGNALS Japanese Patent Application 2014-037601 "Radar Device”

Abstract

[Problème] Avec les procédés conventionnels il est possible de limiter les échos parasites de surface de la mer qui introduisent une contamination en provenance d'un lobe principal d'antenne, mais il est difficile d'appliquer ces procédés aux échos parasites de surface de la mer qui introduisent la contamination en provenance de lobes latéraux d'antenne. Même avec la même cellule de portée, le diagramme de rayonnement du lobe principal d'antenne et le diagramme de rayonnement des lobes latéraux d'antenne diffèrent de manière significative l'un par rapport à l'autre. En outre, des procédés servant à réduire les échos parasites en calculant des données simulées d'un profil de portée sont limités à être appliqués aux cas dans lesquels des échos météorologiques en provenance de la pluie qui tombe ou analogue sont plus forts que des échos de surface du sol. Ces procédés présentent un problème en ce que les résultats du calcul sont influencés par des hypothèses de la section transversale de dispersion de radar sur la surface du sol et le gain d'antenne, par exemple, utilisé pour calculer les données simulées. [Solution] Dans la présente invention, les échos parasites sont réduits par l'estimation de la puissance électrique des échos parasites introduisant la contamination en provenance du lobe principal d'antenne et des lobes latéraux d'antenne, en fonction de statistiques se rapportant à un signal reçu obtenu par balayage d'un faisceau d'antenne.
PCT/JP2016/056312 2015-03-01 2016-03-01 Dispositif de radar WO2016140230A1 (fr)

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CN108226891A (zh) * 2018-01-26 2018-06-29 中国电子科技集团公司第三十八研究所 一种扫描雷达回波计算方法

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JPH0682548A (ja) * 1992-09-02 1994-03-22 Mitsubishi Heavy Ind Ltd クラッタマップデータの作成方法
JPH07311256A (ja) * 1994-05-20 1995-11-28 Japan Radio Co Ltd クラッタ抑圧回路
JP2001091633A (ja) * 1999-09-20 2001-04-06 Toshiba Corp 模擬クラッタ発生装置
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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN108226891A (zh) * 2018-01-26 2018-06-29 中国电子科技集团公司第三十八研究所 一种扫描雷达回波计算方法
CN108226891B (zh) * 2018-01-26 2021-09-03 中国电子科技集团公司第三十八研究所 一种扫描雷达回波计算方法

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