KR20230151846A - Scatterometer system for ocean parameters monitoring using detected variable distance - Google Patents

Abstract

The scatterometer system for ocean displacement observation includes a transmission output adjustment unit, a variable error detection unit, a variable observation distance correction unit, a measurement data correction unit, an antenna radiation pattern extraction unit, a relative correction unit, and a backscattering coefficient generation unit. The variable error detection unit generates variable errors from marine observation data. The variable observation distance correction unit is connected to the variable error detection unit, and applies the variable error to raw data to perform variable correction into data related to the variable observation distance. The measurement data correction unit is connected to the transmission output adjustment unit and the variable observation distance correction unit, and generates absolutely corrected data using the variable correction data and reference value data authorized by the variable observation distance correction unit. The relative correction unit generates relative correction data by applying the antenna radiation pattern to the absolute correction data.

Description

Scatterometer system for observing ocean displacement using variable observation distance {SCATTEROMETER SYSTEM FOR OCEAN PARAMETERS MONITORING USING DETECTED VARIABLE DISTANCE}

The present invention relates to a scatterometer system for observing ocean displacement using a variable observation distance. More specifically, it relates to a scatterometer system for observing ocean displacement with improved accuracy by applying a variable observation distance to FMCW (Frequency Modulated Continuous Wave).

Global environmental research is a field that investigates the geology, ocean, and ecology of a vast area and includes field surveys, indoor experiments, and remote sensing.

Field investigation includes inspection using the naked eye or various investigation equipment by visiting the site directly, such as surface exploration, boring, and physical exploration. Because field surveys are highly accurate, they are still widely used in cases where precise measurements are required. Indoor experiments measure chemical and physical properties that are difficult to measure directly in the field using precision measuring equipment within the laboratory. Field surveys and indoor experiments have the advantage of high accuracy, but due to temporal and spatial constraints, they are not easy to apply to large areas, remote areas, remote areas, and the ocean.

Recently, due to the development of remote sensing technology, remote sensing using satellites, aircraft, etc. has become increasingly widely used. In particular, remote sensing is very useful in disaster situations such as volcanic eruptions, earthquakes, and typhoons, or in environmental monitoring such as glaciers, tides, waves, and marine pollution.

Common remote sensing equipment uses radar mounted on artificial satellites or aircraft. However, radar was initially developed for military purposes and has the advantage of detecting moving objects such as aircraft, but it cannot directly measure changes in the global environment such as waves, tides, volcanic ash, and typhoons.

Conventional remote sensing methods indirectly estimate changes in the global environment using distance measurement functions such as radar. However, waves, tides, volcanic ash, typhoons, etc. show real-time changes in seawater, fine particles, and clouds that do not easily reflect radio waves. Therefore, it is difficult to smoothly measure in response to various global environments using conventional remote sensing methods, and the reliability of measured values is low.

Research has been conducted to overcome the special characteristics of ocean displacement observations, that is, the characteristics of the sea surface where transmitted waves are totally reflected.

In the case of Republic of Korea Patent No. 10-1273183 (“Method for Calibration of Active Multi-Polarization Radar System”), a technology was developed to detect targets in a range that is difficult to detect with only one transmission wave using multi-polarization. However, when using multiple polarization, the existing FMCW system must be completely improved and changed to a system that transmits and receives multiple polarizations. Therefore, additional cost and time are required to develop a multi-polarization FMCW system.

In the case of Korea Registered Patent No. 10-Korea Patent No. 10-1784178 (“Scatterometer system for observing ocean displacement”), a technology to overcome low radio wave response characteristics was developed using a radio wave scattering model and a shortened delay demodulation technique. . However, because ocean displacement changes in real time and various noises exist, more accurate ocean displacement observation technology is required.

Republic of Korea Patent No. 10-1273183 (June 3, 2013) Republic of Korea Patent No. 10-1784178 (2017.9.27.) Republic of Korea Patent No. 10-1978555 (May 8, 2019)

The purpose of the present invention is to provide a scatterometer system for observing ocean displacement with improved accuracy by applying a variable observation distance to FMCW (Frequency Modulated Continuous Wave).

The scatterometer system for observing ocean displacement according to an embodiment of the present invention includes a waveform generator, a transmission output adjuster, a distributor, an antenna member, a mixer, a raw data generator, a reference value storage unit, a variable error detection unit, a variable observation distance correction unit, and measurement data. It includes a correction unit, an antenna radiation pattern extraction unit, a relative correction unit, and a backscattering coefficient generation unit. The waveform generator generates a signal with the same waveform as the transmitted wave. The transmission output adjusting unit is connected to the waveform generator and adjusts the transmission output of the transmission wave. The distributor is connected to the waveform generator and distributes the signal generated by the waveform generator to generate a distribution signal. The antenna member is connected to the distributor, transmits the distribution signal as the transmission wave toward the sea surface, and receives a reception wave in which the transmission wave is reflected from the sea surface. The mixer is connected to the distributor and the antenna member, and mixes the signal distributed by the distributor and the received wave. The raw data generator is connected to the mixer and generates raw data using the distribution signal and the received wave received from the mixer. The reference value storage unit is connected to the raw data generator and stores reference value data. The variable error detection unit generates variable errors from marine observation data. The variable observation distance correction unit is connected to the variable error detection unit and the raw data generation unit, and applies the variable error to the raw data to perform variable correction into data related to the variable observation distance. The measurement data correction unit is connected to the transmission output adjustment unit, the reference value storage unit, and the variable observation distance correction unit, and the variable correction data received from the variable observation distance correction unit and the reference value received from the reference value storage unit. Absolutely corrected data is created using the data. The antenna radiation pattern extractor is connected to the raw data generator and includes an area where the transmitted wave is projected onto the sea level from the raw data, a distortion characteristic of the received wave measured at each location on the sea level, and a correction coefficient. Outputs the antenna radiation pattern. The relative correction unit is connected to the measurement data correction unit and the antenna radiation pattern extraction unit, and generates relative correction data by applying the antenna radiation pattern to the absolute correction data. The backscattering coefficient generating unit is connected to the relative correction unit and generates a backscattering coefficient by normalizing the relative corrected data.

In one embodiment, the raw data generator generates transmission signal data (V _t ), received signal raw data (V _r ), and measurement data (u) as shown in [Equation 1] and [Equation 2] with radio wave response characteristics (s _vv ). _vv ), distance attenuation (1/r ² ), phase component (e ^-j2kr ), and transmit/receive signal attenuation (rt).

[Equation 1]

[Equation 2]

In one embodiment, the raw data generator applies the actual observation distance (r ₂ ) to the received wave reflected from the sea surface to generate transmission signal data (V _t,sea ) heading to the sea surface as in [Equation 3], from the sea surface. Transmitted wave (2) and received wave in data obtained through reflected received signal data (V _r2 ), distance attenuation (1/r ₂ ² ) and phase component (e ^-j2kr2 ) proportional to observation distance (r ₂ ) Raw data (S _{vv, sea} ) can be generated by reflecting the signal attenuation (rt) by the transmission and reception path in (4).

[Equation 3]

In one embodiment, the reference value data stored in the reference value storage unit may be reference value data generated regarding a metal sphere placed on the sea level. The reference value storage unit may further store the radar effective reflection area of the transmitted wave. The reference value data stored in the reference value storage unit may be reference value data generated with respect to a triangular passive radio reflector placed on the sea level. The reference value storage unit further stores the radar effective reflection area regarding the triangular passive radio reflector in addition to the radar effective reflection area regarding the metal sphere, and the measurement data correction unit stores the radar effective reflection area relating to the metal sphere and the radar effective reflection area relating to the metal sphere. The correction coefficient can be generated by comparing the radar effective reflection area with respect to the triangular passive radio reflector.

In one embodiment, the reference value data regarding the metal sphere disposed on the sea level is transmission signal data (V _t,sph ) directed to a metal sphere whose response characteristics are known to the raw data generator, from the metal sphere. By applying the reflected received signal data (V _r1 ), the distance between the antenna member 100 and the metal sphere (r ₁ ), and the radio wave response characteristics (S _{vv, sph} ) of the metal sphere to [Equation 4], distance attenuation Reference value data (s _{vv, sph} ) can be generated by reflecting the signal attenuation (rt) due to the transmission and reception paths of the transmitted and received waves in the data obtained through (1/r ₁ ² ) and the phase component (e ^-j2kr1 ). there is.

[Equation 4]

In one embodiment, the reference value storage unit can organize the signal attenuation (rt) caused by the metal sphere from [Equation 3] to [Equation 5].

[Equation 5]

In one embodiment, the variable error detection unit may detect the variable error by extracting tidal changes from the ocean observation data. The variable error detection unit may determine the variable error from distance information measured when the incident angle of the transmission wave is 0 degrees.

In one embodiment, the variable observation distance correction unit applies the variable observation distance (r ₂ + δr ) to the raw data (s _{vv, r2} ) as in [Equation 6] to obtain the variable correction data (s _{vv, cal1)} . ) can be created.

[Equation 6]

In one embodiment, the measurement data correction unit may generate the absolutely corrected raw data by multiplying the distance attenuation component and phase component of the variable observation distance by the received wave component, the transmitted wave component, and the reference value data.

In one embodiment, the measurement data correction unit calculates the distance attenuation component ((r ₂ + δr ) ² /r ₁ ² ) of the variable observation distance (r ₂ + δr ) compared to the _reference distance (r 1 ) as shown in [Equation 7] Phase component (e ^{-j2k(r1-r2-δr)} ), received wave component (V _r,sea /V _r,sp h), transmitted wave component (V _t,sph /V _t,sea ), and reference value data ( Absolutely corrected data (s _{vv, STCT) can be generated by multiplying s vv,} sph).

[Equation 7]

In one embodiment, the measurement data correction unit controls the transmission output adjustment unit to make the transmission output of the transmission wave equal to the transmission output of the reference value data stored in the reference value storage unit to obtain the transmission wave component ( The absolutely corrected data (s _vv,STCT ) where V _t,sph /V _t,sea ) is 1 can be generated.

[Equation 8]

In one embodiment, the relative correction unit adds the absolute correction data by applying the distortion characteristic and the correction coefficient to each pixel on the area where the sea level is projected, divides it by the area of the area projected on the sea level, and calculates the relative correction. Data can be generated.

In one embodiment, the relative correction unit 270 calculates absolute correction data (s _vv ) for each pixel (or position) (x _i , y _j ) on the sea level as shown in [Equation 9]. _,STCT ), the distortion characteristics (D) and correction coefficient (a) due to the antenna beam pattern are applied and added, and the relative correction data (S° _vv,sea ) is divided by the area where the antenna pattern is projected onto the sea level (A _ill ). ) can be obtained.

[Equation 9]

In one embodiment, the backscattering coefficient generator may generate the backscattering coefficient by normalizing the relatively corrected data (S° _vv,sea ) received from the relative correction unit.

[Equation 10]

According to the present invention as described above, the variable observation distance correction unit uses variable error ( δr ) to correct errors due to ocean observation data including tide changes, thereby reducing the error of the scatterometer system for observing ocean displacement.

The measurement data correction unit additionally performs an absolute calibration process (Single Target Calibration Technique; STCT) using the reference value data (s _{vv, sph} ) and signal attenuation (rt) received from the reference value storage unit. In addition, the measurement data correction unit and the transmission output adjustment unit adjust the transmission output (V _{t, sea} ) of the transmission wave transmitted to the sea surface to be equal to the reference value transmission output (V _{t, sph} ) corresponding to the metal sphere, thereby generating a separate transmission signal. The error of the scatterometer system for observing ocean displacement is reduced by eliminating external influences under the same measurement conditions (metal sphere/sea surface) where the interference signal is the same without measurement.

In addition, the relative correction process uses the area where the relative correction unit is projected onto the sea level (A _ill ), the distortion characteristic (D) due to the antenna pattern measured at each position (x _i , y _j ) on the sea surface, and the correction coefficient (a). Perform.

Therefore, the accuracy of sea level backscattering coefficient measurement is improved by performing a combination of correction using variable error ( δr ), absolute correction for comparing with the reference value, and relative correction for correcting the distortion characteristics due to the antenna pattern.

Figure 1 is a block diagram showing a scatterometer system for observing ocean displacement using a variable observation distance according to an embodiment of the present invention.
Figure 2 is an image showing the state in which the scattering system for ocean displacement observation using the variable observation distance shown in Figure 1 is installed at the Ieodo Marine Base.
FIG. 3 is a graph showing the variable observation distance generated by the variable error detection unit shown in FIG. 1.
Figure 4 is an image showing a scatterometer system for observing ocean displacement using the variable observation distance shown in Figure 1.
Figure 5 is a graph showing range profile and tidal changes by date measured when the incident angle of the transmitted wave is 0 degrees.
FIG. 6 is a graph showing the transmission wave interference signal for the measurement of FIG. 5.
Figure 7 is a graph showing the backscattered signal caused by the reflected wave of Figure 5.
Figures 8 to 13 show the backscatter coefficient measured without correction when the angle of incidence changes from 0° to 50° at 10° intervals, and the backscatter coefficient measured in a scatterometer system for observing ocean displacement using the variable observation distance shown in Figure 1. It represents a number.
Figure 14 shows the backscattering coefficient measured without correction when the wind speed is high and the backscattering coefficient measured in a scatterometer system for observing ocean displacement using the variable observation distance shown in Figure 1.
Figure 15 is for ocean displacement observation using the backscattering coefficient by vertical polarization (VV)/horizontal polarization (HH) of the theoretical scattering model (Integral Equation scattering Model (IEM)) and the variable observation distance shown in Figure 1 when the wind speed is low. Indicates the backscattering coefficient measured in the laying hen system.

Hereinafter, the present invention will be described in more detail with reference to the attached drawings. Since the present invention can be subject to various changes and have various forms, specific embodiments will be illustrated in the drawings and described in detail in the text. However, this is not intended to limit the present invention to a specific disclosed form, and should be understood to include all changes, equivalents, and substitutes included in the spirit and technical scope of the present invention.

While describing each drawing, similar reference numerals are used for similar components. In the attached drawings, the dimensions of the structures are enlarged from the actual size for clarity of the present invention.

Terms such as first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The above terms are used only for the purpose of distinguishing one component from another. For example, a first component may be referred to as a second component without departing from the scope of the present invention, and similarly, the second component may also be referred to as a first component. Singular expressions include plural expressions unless the context clearly dictates otherwise.

In this application, terms such as “comprise” or “have” are intended to designate the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, but are not intended to indicate the presence of one or more other features. It should be understood that this does not exclude in advance the possibility of the existence or addition of elements, numbers, steps, operations, components, parts, or combinations thereof.

Additionally, unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as generally understood by a person of ordinary skill in the technical field to which the present invention pertains. Terms defined in commonly used dictionaries should be interpreted as having a meaning consistent with the meaning in the context of the related technology, and unless explicitly defined in the present application, should not be interpreted in an ideal or excessively formal sense. No.

Figure 1 is a block diagram showing a scattering meter system for ocean displacement observation using a variable observation distance according to an embodiment of the present invention, and Figure 2 is a diagram showing a scattering meter system for ocean displacement observation using a variable observation distance shown in Figure 1. This is an image showing the state of installation at the marine base.

Referring to Figures 1 and 2, the scatterometer system for ocean displacement observation using a variable observation distance includes an antenna member 100, a waveform generator 150, a transmission output adjuster 160, a distributor 170, a mixer 205, Raw data generation unit 210, reference value storage unit 220, variable error detection unit 230, variable observation distance correction unit 240, measurement data correction unit 250, antenna radiation pattern extraction unit 260, relative information It includes a government unit 270, a backscattering coefficient generator 280, and an output unit 290. In one embodiment, a scattering system for ocean displacement observation using a variable observation distance may be installed at a base on the sea level, such as the Ieodo Marine Base. In another embodiment, a scatterometer system for observing ocean displacement using a variable observation distance may be mounted on a flying vehicle such as an aircraft, drone, or installed on a land facility on the coast.

The antenna member 100 transmits a transmission wave (2) to the sea surface and receives a reception wave (4) reflected from the sea surface. In this embodiment, the antenna member 100 includes a transmitting antenna 110, a receiving antenna 120, and a driving unit 130.

In this embodiment, the antenna member 100 includes a transmitting antenna 110 and a receiving antenna 120. In another embodiment, the antenna member 100 includes only one antenna, and transmission of the transmission wave 2 and reception of the reception wave 4 may be performed simultaneously through one antenna.

The transmission antenna 110 transmits the signal generated from the waveform generator 150 as a transmission wave (2). For example, the waveform generator 150 may generate a sawtooth wave (S_sawtooth).

The receiving antenna 120 receives the receiving wave 4 generated by reflection of the transmitted wave 2 from the sea surface.

The driving unit 130 is connected to the transmitting antenna 110 and the receiving antenna 120 and controls the transmission and reception directions of the transmitting antenna 110 and the receiving antenna 120. For example, the driver 130 can change the transmission and reception directions of the transmission antenna 110 and the reception antenna 120 from 0 degrees to 50 degrees at 10-degree intervals based on the direction perpendicular to the sea level. Those skilled in the art will know that the driving direction and spacing of the driving unit 130 can be freely changed depending on the target object. In another embodiment, the driving unit 130 may be omitted.

When the antenna member 100 is placed at a distance of less than 40 meters from the sea level, if the transmission/reception direction exceeds 70 degrees based on the direction perpendicular to the sea level, the distance between the antenna member 100 and the sea level exceeds 120 meters. do. If the distance between the antenna member 100 and the sea level exceeds 120 meters while the transmission/reception direction exceeds 70 degrees based on the direction perpendicular to the sea level, the sensitivity of the received wave 4 rapidly decreases and the error increases. .

The driving unit 130 may include a driving motor (not shown) and a driving circuit (not shown). In another embodiment, the transmission and reception directions of the transmission antenna 110 and the reception antenna 120 may be adjusted manually without a separate driving unit.

The waveform generator 150 generates a signal with the same waveform as the transmission wave 2. For example, the waveform generator 150 may generate a sawtooth wave (S_sawtooth) whose frequency increases uniformly over time and then resets at a predetermined period.

The transmission output adjustment unit 160 is connected to the waveform generator 150 and the measurement data correction unit 250 to adjust the transmission output. Specifically, the transmission output adjustment unit 160 adjusts the transmission power (V _t,sea ) and the reference value transmission power (V _t,sph ) of the transmission wave 2 transmitted to the sea surface. For example, the transmission power adjustment unit 160 can adjust the transmission power (V _t,sea ) and the reference value transmission power (V _t,sph ) of the transmission wave 2 transmitted to the sea surface.

The distributor 170 is connected to the waveform generator 150 and the antenna member 100. The distributor 170 distributes the signal generated by the waveform generator 150 and delivers it to the antenna member 100 and the mixer 205.

The mixer 205 mixes the distribution signal received through the distributor 170 and the received wave 4 received from the antenna member 100 and transmits it to the raw data generator 210.

The raw data generation unit 210 is connected to the mixer 205, the reference value storage unit 220, the variable error detection unit 240, and the antenna radiation pattern extraction unit 260. The raw data generator 210 generates raw data using the distribution signal received from the mixer 205 and the received wave 4.

The raw data generated by the raw data generator 210 is a radio wave response characteristic (s _vv ), and is composed of transmitted signal data (V _t ), received signal raw data (V _r ), and measurement data (u _vv) as shown in [Equation 1]. ), distance attenuation (1/r ² ), phase component (e ^-j2kr ), and transmit/receive signal attenuation (rt). In this embodiment, raw data refers to data including radio wave response characteristics.

[Equation 1]

If [Equation 1] is organized in the form of raw data (S _vv ), the raw data (S _vv ) generated by the raw data generator 210 is expressed as [Equation 2].

[Equation 2]

The raw data generator 210 may generate reference value data based on observations based on actual sea level observations and/or reference objects with known theoretical response characteristics (e.g., metal spheres).

In one embodiment, the raw data generator 210 applies the actual observation distance (r 2 ) at which the transmitted wave 2 and the received wave ₄ are observed by reflecting from the sea surface. The actual observation distance (r ₂ ) represents the distance between the antenna member 100 and the observation point on the sea level. When the actual observation distance (r ₂ ) is applied to the raw data generator 210, the transmission signal data (V _t,sea ) heading toward the sea surface, the reception signal data (V _r2 ) reflected from the sea surface, as shown in [Equation 3], _{Signal attenuation} ^{( _} rt) is reflected to generate raw data (S _{vv, sea} ).

[Equation 3]

In one embodiment, the raw data generator 210 transmits the transmitted signal data (V _t,sph ) where the transmitted wave 2 and the received wave 4 are directed to a metal sphere with known theoretical response characteristics, from the metal sphere. The reflected received signal data (V _r1 ) and the distance (r ₁ ) between the antenna member 100 and the metal sphere are applied to the raw data generator 210 as a reference value observation distance (r ₁ ) to generate reference value data (s _{vv, sph} ). The raw data generator 210 generates the transmission and reception paths of the transmission wave (2) and the reception wave (4) to the data obtained through the distance attenuation (1/r ₁ ² ) and the phase component (e ^-j2kr1 ) as shown in [Equation 4]. Reference value data (s _{vv, sph} ) is generated by reflecting the signal attenuation (rt) and stored in the reference value storage unit 220.

[Equation 4]

In one embodiment of the present invention, the signal attenuation (rt) due to the transmission and reception paths of the transmitting wave (2) and the receiving wave (4) is the same as the signal attenuation (rt) due to the corrected variable observation distance (r ₂ + δr ) or have almost similar values. It is not intended to limit the scope of the present invention by theory, but as long as the transmission and reception paths of the transmission wave 2 and the reception wave 4 are the same, it does not matter whether the target type is sea level or a metal ball.

If the signal attenuation (rt) is the same, it can be summarized by the signal attenuation (rt) as shown in [Equation 3] to [Equation 5] using a metal sphere.

[Equation 5]

The reference value storage unit 220 is connected to the raw data generation unit 210 and the measurement data correction unit 250, and provides information to the raw data generation unit 210 regarding the metal sphere to which the reference value observation distance (r ₁ ) is applied. The reference value data (s _{vv, sph} ), signal attenuation (rt), and radar effective reflection area (Radar Cross Section; RCS) generated by are stored. In one embodiment, the reference value storage unit 220 is a triangular passive propagation in addition to the reference value data (s _{vv, sph} ) and signal attenuation (rt) generated by the raw data generation unit 210 with respect to the metal sphere. Reference value data (s _vv,tri ), signal attenuation (rt), and radar effective cross section (RCS) generated by a trihedral corner reflector can be further stored.

The variable error detection unit 230 is connected to the variable observation distance correction unit 240 and generates variable error ( δr ) by correcting marine observation data including tide changes. Variable error ( δr ) is generated by observation altitude by comparing marine observation data including tidal changes with raw data (s _{vv, r2} ) generated by applying the actual observation distance (r ₂ ) to the raw data generator 210. do.

FIG. 3 is a graph showing the variable observation distance generated by the variable error detection unit shown in FIG. 1, and FIG. 4 is an image showing a scatterometer system for observing ocean displacement using the variable observation distance shown in FIG. 1.

Referring to Figures 1 to 4, the variable error ( δr ) represents the tidal change at a fixed observation altitude (h0). When the observation altitude (h0) of the antenna member 100 is 15 m to 100 m, the variable error ( δr ) observed at the Ieodo Marine Base in Korea may be -1.5 m to 1.5 m. For example, when the observation altitude is 24m, the final correction error generated by the variable error ( δr ) may be ±2dB.

The variable error detection unit 230 can determine the variable error δr from the range profile of marine observation data measured when the incident angle of the transmission wave 2 is 0 degrees. For example, since the angle of incidence of the transmission wave 2 is 0 degrees, the variable error ( δr ) may have the same value as the tidal change ( δh ).

The variable observation distance correction unit 240 is connected to the raw data generation unit 210, the variable error detection unit 230, and the measurement data correction unit 250. The variable observation distance correction unit 240 applies the variable error ( δr ) to the actual observation distance (r ₂ ) and converts the raw data (s _{vv, r2} ) about the actual observation distance (r ₂ ) into the variable observation distance (r). Variable correction is made with data (s _{vv,r2+ δ r} ) about ₂ + δr ).

Regarding the variable observation distance (r ₂ + δr ) corrected by the variable observation distance correction unit 240, the variable correction raw data (s _vv,cal1 ) can be expressed as [Equation 6].

[Equation 6]

The measurement data correction unit 250 is connected to the transmission output adjustment unit 160, the reference value storage unit 220, the variable observation distance correction unit 240, and the relative correction unit 270.

The measurement data correction unit 250 receives the corrected variable correction data (s _{vv, cal1} ) and the reference value storage unit 220 with respect to the variable observation distance (r ₂ + δr ) corrected by the variable observation distance correction unit 240. An absolute calibration process (Single Target Calibration Technique; STCT) is performed using the approved reference value data (s _{vv, sph} ) and signal attenuation (rt). If an absolute correction process is performed by directly applying the reference value to the actual observation distance (r ₂ ), errors may occur due to tidal changes, etc. However, in the embodiment of the present invention, rather than directly applying the reference value to the actual observation distance (r ₂ ), the reference value is applied to the variable observation distance (r ₂ + δr ) to which marine observation data such as tide changes are applied to variable-corrected data ( Perform the absolute correction process using s _vv,cal1 ). In one embodiment, the measurement data correction unit 250 performs an absolute correction process by applying response characteristics corresponding to the variable observation distance (r ₂ + δr ) and the distance to the metal sphere (r ₁ ).

The measurement data correction unit 250 applies the signal attenuation (rt) obtained by [Equation 5] to [Equation 6] to obtain the absolutely corrected data (s _{vv, STCT} ) as shown in [Equation 7].

[Equation 7]

Referring to [Equation 7], the measurement data correction unit 250 calculates the absolute corrected data (s _{vv, STCT} ) as a distance attenuation component ((r) of the variable observation distance (r ₂ + δr ) compared to the reference distance (r ₁ ). ₂ + δr ) ² /r ₁ ² ) and the phase component (e ^{-j2k(r1-r2-δr)} ), the received wave component (V _r,sea /V _r,sp h), and the transmitted wave component (V _t,sph ) /V _t,sea ), and the reference value data (s _vv,sph ) are multiplied to generate absolutely corrected data (s _vv,STCT ).

In one embodiment, the transmission output adjustment unit 160 may adjust the transmission output (V _t,sea ) of the transmission wave 2 transmitted to the sea surface to be equal to the reference value transmission output (V _t,sph ) corresponding to the metal sphere. there is. In one embodiment, the measurement data correction unit 250 compares the transmission output (V _{t, sea} ) of the transmission wave 2 with the reference value transmission output (V _{t, sph} ) corresponding to the metal sphere, and the transmission output adjustment unit 160 ) can be controlled. Therefore, the transmission wave 2 transmitted to the sea surface has the same measurement conditions (metal sphere/sea level) as the transmission wave 2 transmitted to the metal sphere, and external influences due to interference signals are eliminated without separate transmission signal measurement. .

If the transmission power (V _t,sea ) of the transmission wave (2) and the reference value transmission power (V _t,sph ) are the same, the transmission wave component (V _t,sph /V _t,sea ) in [Equation 7] is 1. The absolutely corrected data (s _{vv, STCT} ) is changed as shown in [Equation 8].

[Equation 8]

Referring to [Equation 8], when the measurement data correction unit 250 adjusts the transmission output adjustment unit 160 and the transmission wave component (V _t,sph /V _t,sea ) becomes 1, the measurement data correction unit 250 ) is the absolute corrected data (s _{vv , STCT} ) _is the distance attenuation component ((r ₂ + δr ) ² /r ₁ ² ) and phase component ( e ^{-j2k(r1-r2-δr)} ) is multiplied by the received wave component (V _r,sea /V _r,sp h) and the reference value data (s _vv,sph ) to obtain the absolutely corrected data (s _vv,STCT ). Create.

In addition, the measurement data correction unit 250 calculates the radar effective reflection area (RCS) for the metal sphere and the radar effective reflection area (RCS) for the trihedral corner reflector authorized by the reference value storage unit 220. Create a correction coefficient (a) using

The antenna radiation pattern extraction unit 260 is connected to the raw data generation unit 210 and the relative correction unit 270. The antenna radiation pattern extraction unit 260 transmits variables/constants related to the antenna pattern to the relative correction unit 270. Variables/constants related to the antenna pattern are the area projected on the sea surface (A _ill ), the distortion characteristic (D) caused by the antenna pattern of the received wave (4) measured at each location (x _i , y _j ) on the sea surface, and the correction coefficient. (a), etc. (i,j are natural numbers). The antenna radiation pattern extractor 260 may extract variables/constants related to the antenna radiation pattern from the raw data (S _vv,sea ) authorized by the raw data generator 210 or use preset values. For example, the distortion characteristic (D) caused by the antenna beam pattern measured at the area where the antenna pattern is projected onto the sea surface (A _ill ) and each position (x _i ,y _j ) on the sea surface is the raw data (S _vv,sea ). It is extracted from, and the correction coefficient (a) can use a preset value.

The relative correction unit 270 is connected to the measurement data correction unit 250 and the antenna radiation pattern extraction unit 260. The relative correction unit 270 generates relative correction data (S° vv, _sea ) by correcting the characteristics of the antenna pattern to the absolutely corrected data (s _{vv, STCT} ) approved by the measurement data correction unit 250. . In this embodiment, the relative correction data (S° _vv,sea ) is the area (A _ill ) where the antenna pattern is projected on the sea level to the absolute correction data (s _vv,STCT ) as in [Equation 9], and each position on the sea level. It is obtained by applying the distortion characteristic (D) and correction coefficient (a) due to the antenna beam pattern measured at (x _i ,y _j ).

[Equation 9]

In [Equation 9], the relative corrected data (S° _vv,sea ) is inversely proportional to the area on which the sea level is projected (A _ill ). The area where the sea surface is projected (A _ill , illuminated area) represents the area of the entire effective range where the antenna beam of the transmitted wave (2) is projected onto the sea surface. For example, when the transmission wave 2 is incident on the sea surface, a convex three-dimensional antenna beam pattern is oblique incidence on the sea surface. When a convex three-dimensional antenna beam pattern is incident on the sea surface at an angle, differential scatterers within the area where the antenna beam is projected (A _ill ) have different propagation paths based on the center of the antenna. In order to apply different propagation paths, changes in distance and angle of incidence must be reflected in the antenna beam pattern of the transmission wave (2). In order to reflect the distance change and incident angle change in the antenna beam pattern of the transmitted wave (2), the area projected on the sea surface considering the spatial/electrical characteristics of the transmitted wave (2) (e.g., gain/intensity change according to the incident angle change) (A _ill ) is decided. For example, the area projected onto the sea level (A _ill ) is expressed in area units.

Additionally, the relative corrected data (S° _vv,sea ) is inversely proportional to the correction coefficient (a). The correction coefficient (a) is determined by measuring the radar cross section (RCS) of two different targets that can be theoretically analyzed. For example, the measurement data correction unit 250 determines the correction coefficient (a) by comparing the effective radar reflection area for the metal sphere and the effective radar reflection area for the triangular passive radio reflector.

In one embodiment, the relative correction unit 270 calculates the distortion characteristic (D) due to the antenna beam pattern to the absolute correction data (s _{vv, STCT} ) for each pixel (or position) (x _i , y _j ) on the sea level. Relatively corrected data (S° _vv,sea ) can be obtained by applying the correction coefficient (a), adding it up, and dividing it by the area where the antenna pattern is projected onto the sea level (A _ill ).

The backscattering coefficient generating unit 280 is connected to the relative correction unit 270 and the output unit 290. The backscattering coefficient generator 280 normalizes the relatively corrected data (S° _vv,sea ) received from the relative correction unit 270 to generate a backscattering coefficient. In one embodiment, the backscattering coefficient generator 280 generates a backscattering coefficient from relatively corrected data (S° _vv,sea ) using [Equation 10].

[Equation 10]

The output unit 290 is connected to the backscattering coefficient generator 280 and outputs the backscattering coefficient received from the backscattering coefficient generator 280.

Experiment example

Sea level was observed using a scatterometer system for observing ocean displacement using a variable observation distance shown in Figure 1. In this experimental example, the scatterometer system for observing ocean displacement using a variable observation distance was implemented as a Frequency Modulated Continuous Wave (FMCW) radar with the following values.

The operating frequency was 9.65GHz, the bandwidth (BW) was 498MHz, the output power was up to 3W, and the modulation rate (chirp rate, Kr = BW/Tr) was 498×10 ⁹ Hz/s. , the sampling frequency (f _ADC ) was (approximately) 1.2MHz, the maximum ranging (R _max ) was 198m, the distance difference (ΔR) was (approximately) 0.3m, and the The radar beamwidth was 12° in the elevation direction (θ _ev ) and 10° in the azimuth direction (ϕ _az ) based on the Half Power Beam Width (HPBW), and the polarization direction of the transmission wave (2) was It was vertical polarization (e.g. vv-polarization).

While changing the incident angle of the transmission wave (2) from 0° to 50°, the backscattering coefficient was measured at 10° intervals every 30 seconds.

Figure 5 is a graph showing range information (range profile) and tidal change ( δh ) measured by date when the incident angle of the transmitted wave is 0 degrees. In Figure 5, the distance (range) represents the distance (m) from the antenna member 100 to the sea level observation point, and the date (date) is from August 4 to August 10, 2020 at the Ieodo Marine Research Station. Indicates the measurement date, and intensity (dB) represents the intensity of the distance information (range profile).

Referring to Figure 5, the correction error due to tidal changes ranged from -2dB to 2dB, the standard deviation ( σ ) of the correction error was 0.79dB, the average of the maximum tidal value was 7.61m, and the maximum tidal value was The standard deviation was 9.5mm.

FIG. 6 is a graph showing the transmitted wave interference signal for the measurement of FIG. 5, and FIG. 7 is a graph showing the backscattered signal due to the reflected wave of FIG. 5. In Figures 6 and 7, the horizontal axis represents the observation date, the vertical axis of the upper figure represents the normalized intensity of tidal change (dB), and the vertical axis of the lower figure represents the tidal value (m).

Referring to FIG. 6, since the amount of change in transmission output is adjusted to be the same by the transmission output adjustment unit 160 and the measurement data correction unit 250 (V _f,sea /V _f,sph = 1), the tidal value (m) The standard deviation was 0.0095m, which was virtually close to 0. Specifically, because the amount of change in transmission output was adjusted to be the same, external influences were removed under the same measurement conditions (metal ball/sea level) of the interference signal without separate measurement of the transmission signal. Since the output of the transmission output adjuster 160 and the waveform generator 150 can be corrected only with relative changes rather than absolute values, the standard deviation of the tidal value was close to 0.

Referring to Figure 7, the average backscattering coefficient intensity of the received wave (4) reflected from the sea surface was 4.32dB, the average observation distance was 31.29m, the tidal change (δh) was ±1.5m, and the standard deviation was 0.77. It was m.

Figures 8 to 13 show the backscatter coefficient measured without correction when the angle of incidence changes from 0° to 50° at 10° intervals, and the backscatter coefficient measured in a scatterometer system for observing ocean displacement using the variable observation distance shown in Figure 1. It represents a number. In each of FIGS. 8 to 13, the upper drawing shows the backscattering coefficient measured without correction, and the lower drawing shows the backscattering coefficient measured in a scatterometer system for observing ocean displacement using the variable observation distance shown in FIG. 1. 8 to 13, the horizontal axis represents time and the vertical axis represents the backscattering coefficient.

Referring to FIG. 8, when the incident angle was 0° and there was no correction, the average backscattering coefficient was -15.16dB and the standard deviation was 1.1dB. On the other hand, in the case of the scatterometer system for observing ocean displacement using the variable observation distance shown in Figure 1 at the same angle of incidence, the average backscattering coefficient was -14.67dB and the standard deviation was 0.98dB.

Therefore, when the angle of incidence is 0°, the standard deviation decreased by 0.12dB from 1.1dB to 0.98dB, improving the accuracy of the backscattering coefficient by 10.9%.

Referring to Figure 9, when the incident angle was 10° and there was no correction, the average backscattering coefficient was -21.77dB and the standard deviation was 1.82dB. On the other hand, in the case of the scatterometer system for observing ocean displacement using the variable observation distance shown in Figure 1 at the same angle of incidence, the average backscattering coefficient was -21.79 dB and the standard deviation was 0.91 dB.

Therefore, when the angle of incidence was 10°, the standard deviation was significantly reduced by 0.91dB from 1.82dB to 0.91dB, improving the accuracy of the backscattering coefficient by 50%.

Referring to Figure 10, when the incident angle was 20° and there was no correction, the average backscattering coefficient was -32.71dB and the standard deviation was 1.12dB. On the other hand, in the case of the scatterometer system for observing ocean displacement using the variable observation distance shown in Figure 1 at the same angle of incidence, the average backscattering coefficient was -29.35dB and the standard deviation was 0.92dB.

Therefore, when the angle of incidence was 20°, the standard deviation decreased by 0.2dB from 1.12dB to 0.92dB, improving the accuracy of the backscattering coefficient by 17.8%.

Referring to FIG. 11, when the angle of incidence was 30° and there was no correction, the average backscattering coefficient was -39.32dB and the standard deviation was 0.89dB. On the other hand, in the case of the scatterometer system for observing ocean displacement using the variable observation distance shown in Figure 1 at the same angle of incidence, the average backscattering coefficient was -38.61 dB and the standard deviation was 1.09 dB.

Therefore, when the angle of incidence was 30°, the standard deviation increased by 0.2dB from 0.89dB to 1.09dB, and the accuracy of the backscattering coefficient deteriorated.

Referring to FIG. 12, when the incident angle was 40° and there was no correction, the average backscattering coefficient was -41.95dB and the standard deviation was 0.46dB. On the other hand, in the case of the scatterometer system for observing ocean displacement using the variable observation distance shown in Figure 1 at the same angle of incidence, the average backscattering coefficient was -41.94dB and the standard deviation was 0.55dB.

Therefore, when the angle of incidence was 40°, the standard deviation increased by 0.09 dB from 0.46 dB to 0.55 dB, and the accuracy of the backscattering coefficient deteriorated.

Referring to FIG. 13, when the incident angle was 50° and there was no correction, the average backscattering coefficient was -43.89dB and the standard deviation was 0.23dB. On the other hand, in the case of the scatterometer system for observing ocean displacement using the variable observation distance shown in Figure 1 at the same angle of incidence, the average backscattering coefficient was -43.59 dB and the standard deviation was 0.24 dB.

Therefore, when the angle of incidence was 50°, the standard deviation increased by 0.01 dB from 0.23 dB to 0.24 dB, and the accuracy of the backscattering coefficient deteriorated.

8 to 13, when the incident angle of the transmission wave 2 was 10°, the accuracy of the backscattering coefficient was improved by 50%, showing the best effect. On the other hand, when the incident angle of the transmitted wave (2) exceeds 30°, the accuracy of the backscattering coefficient slightly decreased. However, when the angle of incidence exceeds 30°, the standard deviation of the backscattering coefficient itself has a small value, so the need for correction is low.

Although it is not intended to limit the scope of the present invention by theory, the reason why the accuracy of the backscattering coefficient increases when the incident angle of the transmission wave 2 is low is because the tidal change is a displacement in the vertical direction. Therefore, according to the embodiment of the present invention, the accuracy of the backscattering coefficient is improved even if the incident angle of the transmission wave 2 is low.

Figure 14 shows the backscattering coefficient measured without correction when the wind speed is high and the backscattering coefficient measured in a scatterometer system for observing ocean displacement using the variable observation distance shown in Figure 1. In Figure 14, the horizontal axis represents the angle of incidence of the transmission wave and the vertical axis represents the backscattering coefficient. The backscattering coefficient measured in the scatterometer system for observing ocean displacement using the variable observation distance shown in Figure 1 is generated by the backscattering coefficient generator using [Equation 10].

Referring to FIG. 14, when the wind speed was blowing strongly at 6 m/s to 9.5 m/s, the backscattering coefficient showed a lower value compared to the backscattering coefficient measured without correction at an incident angle of 10° to 20°.

Figure 15 is for ocean displacement observation using the backscattering coefficient by vertical polarization (VV)/horizontal polarization (HH) of the theoretical scattering model (Integral Equation scattering Model (IEM)) and the variable observation distance shown in Figure 1 when the wind speed is low. Indicates the backscattering coefficient measured in the laying hen system. In Figure 15, the horizontal axis represents the angle of incidence of the transmission wave and the vertical axis represents the backscattering coefficient. The backscattering coefficient measured in the scatterometer system for observing ocean displacement using the variable observation distance shown in Figure 1 is generated by the backscattering coefficient generator using [Equation 10].

Referring to FIG. 15, when the wind speed blows weakly at 2.5 m/s to 4 m/s, the backscattering coefficient measured by the scatterometer system for observing ocean displacement using the variable observation distance shown in FIG. 1 is based on the theoretical scattering model (Integral Equation) It was almost identical to the backscattering coefficient by vertical polarization (VV) among the scattering model (IEM). The reason is that in this experimental example, the transmitted wave 2 is vertically polarized. Anyone with ordinary knowledge and experience in the relevant technical field will understand that if the transmission wave (2) is horizontally polarized, it will match the backscattering coefficient due to horizontal polarization (HH) among the theoretical scattering models (IEM).

Therefore, the backscattering coefficient according to the present invention was almost identical to the theoretical scattering model (IEM).

According to the embodiment of the present invention as described above, the variable observation distance correction unit 240 uses variable error ( δr ) to correct errors due to ocean observation data, including tide changes, to provide a scatterometer system for observing ocean displacement. The error decreases.

The measurement data correction unit 250 additionally performs an absolute calibration process (Single Target Calibration Technique; STCT) using the reference value data (s _{vv, sph} ) and signal attenuation (rt) approved by the reference value storage unit 220. . In addition, the measurement data correction unit 250 and the transmission output adjustment unit 160 set the transmission output (V _t,sea ) of the transmission wave (2) transmitted to the sea level to the reference value transmission output (V _t,sph ) corresponding to the metal sphere. By adjusting it to be the same as that, the interference signal is removed under the same measurement conditions (metal ball/sea level) without separate transmission signal measurement, thereby reducing the error of the scatterometer system for observing ocean displacement.

In addition, the relative correction unit 270 uses the area projected onto the sea level (A _ill ), the distortion characteristic (D) due to the antenna pattern measured at each position (x _i , y _j ) on the sea surface, and the correction coefficient (a). Then perform the relative correction process.

Therefore, the accuracy of sea level backscattering coefficient measurement is improved by performing a combination of correction using variable error ( δr ), absolute correction for comparing with the reference value, and relative correction for correcting the distortion characteristics due to the antenna pattern.

Since tidal changes are mainly displacements of the vertical component, errors increase when the incident angle of the transmitted wave is low. However, according to an embodiment of the present invention, accuracy is improved, especially at low angles of incidence, so errors due to tidal changes can be corrected.

The present invention has industrial applicability for purposes such as ocean exploration, remote sensing, satellite exploration, aircraft exploration, exploration using a floating experimental device, bird exploration, and meteorological exploration.

Although the above has been described with reference to examples, those skilled in the art can make various modifications and changes to the present invention without departing from the spirit and scope of the present invention as described in the scope of the utility model registration claims below. You will be able to understand that it exists.

10: Real-time sampling data 11: Average Doppler information
12: Average distance information 14: Backscattering coefficient data
16: Beat frequency-distance two-dimensional data 18: Distance-Doppler two-dimensional data
100: antenna member 110: transmission antenna
120: receiving antenna 130: driving unit
150: waveform generator 160: distributor
205: mixer 210: primary generation unit
220: primary divider 230: average distance extraction unit
240, 245: backscattering coefficient extraction unit 250: distance correction unit
260, 265: Secondary generation unit 270, 275: Distance extraction unit
280, 285: relative speed extraction unit 290: output unit

Claims (10)

A waveform generator that generates a signal with the same waveform as the transmitted wave;
A transmission output adjustment unit connected to the waveform generator to adjust the transmission output of the transmission wave;
a distributor connected to the waveform generator and generating a distribution signal by distributing the signal generated by the waveform generator;
an antenna member connected to the distributor, transmitting the distribution signal as the transmission wave toward the sea surface, and receiving a reception wave in which the transmission wave is reflected from the sea surface;
a mixer connected to the distributor and the antenna member and mixing the signal distributed by the distributor and the received wave;
a raw data generator connected to the mixer and generating raw data using the distribution signal and the received wave received from the mixer;
a reference value storage unit connected to the raw data generation unit and storing reference value data;
A variable error detection unit that generates variable errors from marine observation data;
a variable observation distance correction unit connected to the variable error detection unit and the raw data generation unit, and applying the variable error to the raw data to variably correct it into data related to the variable observation distance;
It is connected to the transmission output adjustment unit, the reference value storage unit, and the variable observation distance correction unit, and uses the variable correction data authorized by the variable observation distance correction unit and the reference value data authorized by the reference value storage unit to determine absolute A measurement data correction unit that generates corrected data;
It is connected to the raw data generator and outputs an antenna radiation pattern including an area where the transmitted wave is projected onto the sea level from the raw data, a distortion characteristic of the received wave measured at each location on the sea level, and a correction coefficient. Antenna radiation pattern extraction unit;
a relative correction unit connected to the measurement data correction unit and the antenna radiation pattern extraction unit, and generating relatively corrected data by applying the antenna radiation pattern to the absolutely corrected data; and
A scatterometer system for observing ocean displacement using a variable observation distance, which is connected to the relative correction unit and includes a backscatter coefficient generator that normalizes the relative correction data to generate a backscatter coefficient. The scatterometer system for observing ocean displacement using a variable observation distance according to claim 1, wherein the reference value data stored in the reference value storage unit is reference value data generated with respect to a metal sphere placed on the sea surface. The scatterometer system for observing ocean displacement using a variable observation distance according to claim 2, wherein the reference value storage unit further stores the effective radar reflection area of the transmitted wave. The scatterometer system for observing ocean displacement using a variable observation distance according to claim 3, wherein the reference value data stored in the reference value storage unit is reference value data generated with respect to a triangular passive radio reflector disposed on the sea surface. The method of claim 4, wherein the reference value storage unit further stores the radar effective reflection area regarding the triangular passive radio reflector in addition to the radar effective reflection area regarding the metal sphere, and the measurement data correction unit stores the radar effective reflection area relating to the metal sphere. A scatterometer system for observing ocean displacement using a variable observation distance, characterized in that the correction coefficient is generated by comparing the radar effective reflection area with the radar effective reflection area of the triangular passive radio reflector. The scatterometer system for observing ocean displacement using a variable observation distance according to claim 1, wherein the variable error detection unit detects the variable error by extracting tidal changes from the ocean observation data. The scatterometer system for observing ocean displacement using a variable observation distance according to claim 6, wherein the variable error detection unit determines the variable error from distance information measured when the incident angle of the transmission wave is 0 degrees. According to claim 1, wherein the measurement data correction unit generates the absolutely corrected raw data by multiplying the distance attenuation component and the phase component of the variable observation distance by the received wave component, the transmitted wave component, and the reference value data. A scatterometer system for observing ocean displacement using observation distance. The method of claim 1, wherein the measurement data correction unit controls the transmission output adjustment unit to make the transmission output of the transmission wave equal to the transmission output of the reference value data stored in the reference value storage unit. Scatterometer system for ocean displacement observation. The method of claim 1, wherein the relative correction unit adds the absolute correction data by applying the distortion characteristic and the correction coefficient to each pixel on the area where the sea level is projected, divides it by the area of the area projected on the sea level, and performs the relative correction. A scatterometer system for observing ocean displacement using a variable observation distance, characterized by generating data.