JP5392936B1 - Radar signal processing method and apparatus - Google Patents

Abstract

In a conventional data interpolation method, since data between sweep lines is interpolated using received power values at the same distance from a radar, generally a weather target whose radar reflection factor changes according to an atmospheric temperature profile or the like is set as an observation target. It is difficult to accurately interpolate the data.
The observation data is not limited to the observation data at the same distance from the radar, but the observation data is selected based on the temperature profile of the atmosphere, and interpolation processing is performed. In the case of a radar that transmits and receives radio waves in a plurality of frequency bands, after applying different weights between different frequencies, observation data is selected according to an atmospheric temperature profile or the like, and interpolation processing is performed.
[Selection] Figure 1

Description

  The present invention relates to a data interpolation method and apparatus in radar signal processing.

  The weather radar apparatus transmits radio waves while scanning an antenna beam, receives a reflected wave from a weather target such as precipitation, and makes it possible to estimate a precipitation distribution from the received power. The received power value can be expressed in a polar coordinate system with the origin being the function of the beam scanning angle and the distance from the radar, that is, the radar position. In the case where pixel dropout occurs when the received power value distribution is converted into the orthogonal coordinate system and displayed on the screen, in Patent Document 1, the observation data of the adjacent sweep line is used and the received power value at the same distance from the radar is used. Data interpolation is performed between sweep lines.

In the case of a radar installed on the ground, the positional relationship between the radar and the observation target (meteorological target, etc.) is in the horizontal direction or the sky direction when viewed from the radar, and the direction of scanning the antenna beam is above the horizontal direction. (In the case of Patent Document 4). On the other hand, in the case of a radar mounted on an aircraft or an artificial satellite, the antenna beam is scanned below the horizontal direction. Radars mounted on aircraft and artificial satellites can observe a wider area than radars installed on the ground.

In the conventional data interpolation method, the data between sweep lines is interpolated using the received power value at the same distance from the radar. Therefore, when the weather target whose radar reflection factor changes depending on the atmospheric condition is to be observed accurately It is difficult to interpolate data. When the observation range reaches several hundred km or more by antenna beam scanning, the influence of the altitude change from the ground surface becomes larger due to the roundness of the earth, and it becomes more difficult.

In addition, satellite radar and airborne radar reduce antenna beam pointing accuracy due to changes in the attitude of the aircraft and changes in the mechanical and thermal environment, so data interpolation or correction to compensate for beam pointing errors There is a need to do. The same applies to a radar mounted on a moving body such as an automobile.

In order to solve the above problems, the first invention is not limited to the observation data at the same distance from the radar , but the observation data is selected on the basis of the atmospheric temperature profile , and interpolation processing is performed. .

The second invention obtains the original beam direction based on the pointing error data of the antenna beam, selects the observation data with reference to the atmospheric temperature profile for the beam direction, and performs data interpolation processing.

In the case of a weather radar that transmits / receives radio waves in multiple frequency bands (C, X, Ku, Ka, W bands have different radio attenuation and radar reflection factors for each band), the third invention has different frequencies. After applying weighting to correct the attenuation and radar reflection factor, the observation data is selected based on the atmospheric temperature profile , and interpolation processing is performed. In a radar using a plurality of frequency bands, observation data can be converted and used between different frequencies. If the reflected data is below the noise level of the receiver due to the observation data in the frequency band with strong rain attenuation such as Ka and W bands, the simultaneous observation data of the low frequency (C, X, Ku band) is converted. And use it.

According to the present invention, in observation by a weather radar, it is possible to accurately interpolate radar reflected waves from a wide range of weather targets. In addition, in the processing of observation data by an artificial satellite or an airborne weather radar in which the pointing accuracy of the antenna beam is likely to be lowered, it is possible to accurately perform data interpolation and correction of the beam pointing error.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a positional relationship between weather radars and weather targets on various platforms, and FIG. 2 is a diagram showing an embodiment of a data interpolation method and apparatus in signal processing of the weather radar according to the present invention. FIG. 3 is a flowchart for explaining the data interpolation method.

FIG. 1 is a schematic diagram in the case of observing a wide area by any one of the weather radars 1 to 3 on various platforms. In particular, in the case of observation by an airborne radar, the observation directions 21 and 22 and data by the antenna 4 are shown. The positional relationship of the direction 20 which performs an interpolation process is shown. In the prior art (Patent Document 1), the interpolation value 10 is obtained by performing an interpolation process based on the observation data 11 and 12 at a position R equidistant from the radar. In the present invention, the observation selected by the atmospheric temperature profile is performed. Interpolation processing is performed based on the data 13 and 14.

As shown in FIG. 2, radio waves are transmitted and received through an antenna and a transmitter / receiver, and observation data for each antenna beam scanning angle and each range bin and coordinates of the data are obtained by a signal processing device.

In the processing in the data interpolation unit, first, the beam direction and the observation data / coordinates of the observation data are input, and the direction for the interpolation processing is given. When the beam pointing error is not 0, the direction in which interpolation processing is performed can be made the original beam direction, and data in that direction can also be obtained by interpolation processing (beam pointing error correction processing).

As shown in FIG. 1, the range bin is obtained based on the atmospheric temperature profile (ΔR1 and ΔR2 are obtained simultaneously), and the weights w1 and w2 are applied to the observation data 13 and 14, and the interpolation value in the direction 20 in which the data interpolation process is performed. Get 10. This process is repeated for each range bin.

In FIG. 1, only two directions (21, 22) are shown as observation directions, but in the case of a radar mounted on a flying object, there are many around the direction of the interpolation target according to the movement of the radar position and by antenna beam scanning. Will have the observation direction. The number of surrounding observation directions is n, including the case of using observation data of a plurality of frequencies (C, X, Ku, Ka, W band, etc.). Weights w1, w2,... Wn are obtained by a distance weighting method, a kriging method, a radial basis function method, or the like.

In actual observation data, the observation data spreads in the range direction due to the influence of the resolution function in the range direction, the antenna pattern, and the like, so that the observation data may be weighted accordingly. In that case, the weight can be expressed as a function of the distance r, w1 (r), w2 (r),... Wn (r).

ここでRはレーダからの距離、P(R)は受信電力(Watt)、Cはレーダのシステム定数、Z(R)は途中降雨減衰補正定数と大気減衰補正定数を含むレーダ反射因子(mm⁶/m³)である。Cはレーダの校正等により予め決められた値である。Z(R)は数１とP(R)の測定値から求められる。 The reflected wave (observation data) from the weather target can be expressed in the same manner as Equation (1) in Patent Document 2.

Where R is the distance from the radar, P (R) is the received power (Watt), C is the radar system constant, Z (R) is the radar reflection factor (mm ⁶ / m ³ ). C is a value determined in advance by radar calibration or the like. Z (R) is obtained from the measured value of Equation 1 and P (R).

First, Z (R) is considered as observation data used for interpolation processing. FIG. 4 shows an example of the vertical profile of Z (R) in the case of observing a state where there is a layer of ice particles in the sky above the rain zone as shown in FIG. For simplicity, the case where the vertical profiles of Z (R) in the directions 20 to 22 are the same is illustrated. Near the 0 ° C altitude, a strong scattering peak from the melting layer of precipitation appears. Near the ground surface, ground surface clutter reaches a certain altitude of 25.

In the prior art (Patent Document 1), since data at the same distance from the radar is used for interpolation, for example, in order to obtain data 10, interpolation processing is performed based on observation data 11 and 12. The radar reflection factor from the weather target is interpolated based on the atmospheric temperature profile , paying attention to the feature that it changes with the altitude (atmospheric temperature profile) from the ground surface according to the change of the state of the weather target (such as precipitation) Select the observation data (13, 14 in the example) used for. In the calculation, interpolation processing is performed according to Formula 2 or a calculation formula (Formula 3) of its logarithm (dB value).

Here, h is the altitude (m) from the ground, t0 is the temperature near the ground (° C.), and Γ is the temperature reduction rate (0.0065 ° C./m) of the standard atmosphere . The distribution of the 0 ° C altitude of the atmosphere varies depending on the latitude and longitude on the sea surface. Interpolation can also be performed according to the state of the weather target (solid precipitation such as rainfall and snowfall) by performing interpolation processing based on the 0 ° C. altitude and the atmospheric temperature profile.

The above is based on Z (R) as the observation data used for the interpolation process, but Ze (R), Ze (R) after performing attenuation correction on received power P (R), Z (R) The precipitation intensity (mm / h) obtained from the above can also be used for interpolation processing.

When using observation data of a plurality of frequencies (C, X, Ku, Ka, W band, etc.), data of a frequency with good reception quality is used as in Patent Document 3. In the example of the vertical profile of FIG. 4, the cross correlation of strong received echoes from the vicinity of the melted layer is obtained between a plurality of frequency bands, and the position where the correlation is maximum is used as the reference of the range bin for performing interpolation processing. When data of a plurality of frequency bands can be used, interpolation processing can be performed without depending on the database of the ground surface position by using the position where the correlation is maximum.

The invention described in the claims immediately before the division of the original application (Japanese Patent Application No. 2013-075637) in the divisional application will be appended below.
[1] means for scanning and transmitting radio waves by scanning an antenna beam;
Means for measuring the received signal for each beam scan;
In a radar apparatus equipped with a flying object , comprising means for interpolating a received signal between the beam scans with a linear or nonlinear function ,
The flying object mounted radar apparatus, wherein the interpolation means includes means for selecting a range bin of a received signal to be interpolated based on an altitude from the ground surface.
[2] Selecting the range bin of the received signal to be interpolated based on the altitude from the ground surface when the received signal obtained by the radar device mounted on the flying object is interpolated between the antenna beam scans by a linear or nonlinear function. An interpolation method characterized by
[3] projectile mounted radar apparatus according to claim 1, projectile mounted radar apparatus, characterized in that the received signal of the original beam direction based on the directional error data of the antenna beam obtained by said interpolation means.

The industrial applicability of the present invention is useful as an apparatus for interpolating data between antenna beam scans of a radar, particularly a weather radar mounted on a moving body such as an aircraft or an artificial satellite.

It is a figure which shows the positional relationship of the weather radar and weather target on various platforms. It is a figure which shows embodiment of this invention. It is a flowchart explaining a data interpolation method. It is a figure which shows the vertical profile of the radar reflection factor for every beam direction, and its positional relationship.

1-3: Radar equipment
4: Airborne radar of the airborne radar 10: Data obtained by interpolation 11-14: Data of the beam direction to be observed
20: Direction of interpolation target 21, 22: Observation beam direction 23: Equidistant line of distance R from radar 24: Contour line from ground surface 25: Altitude covered by ground clutter 31: Transceiver 32: Signal processing Device 33: Data interpolation unit

Patent 3734619 "Radar device and similar device and data interpolation method using the same device" Patent 2616773 "Meteorological radar equipment" Patent 3408943 "Dual-frequency measurement method and multi-frequency radar device" JP-A-9-257929 "Radar equipment"

Claims (4)

Means for transmitting and receiving radio waves by scanning an antenna beam;
Means for measuring a received signal for each observation direction obtained by beam scanning;
In a radar apparatus comprising interpolation means for interpolating a received signal between the beam scans by a linear or nonlinear function,
The radar apparatus according to claim 1, wherein the interpolation means includes means for selecting a range bin of a reception signal to be interpolated based on a positional relationship between an atmospheric temperature profile and a range bin . 2. The radar apparatus according to claim 1, wherein the radar apparatus transmits and receives radio waves in a plurality of frequency bands, and interpolates a received signal between frequencies. An interpolation method comprising: selecting a range bin of a reception signal to be interpolated based on a positional relationship between an atmospheric temperature profile and a range bin when interpolating a reception signal for each observation direction obtained by beam scanning by a radar apparatus . The radar apparatus according to claim 1, wherein the interpolation means obtains a received signal in an original beam direction based on antenna beam pointing error data.

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