CN102721962B - Multi-channel time delay Doppler two-dimensional partition mapping multi-satellite and multi-time image enhanced imaging device - Google Patents
Multi-channel time delay Doppler two-dimensional partition mapping multi-satellite and multi-time image enhanced imaging device Download PDFInfo
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Abstract
The invention discloses a multi-channel time delay Doppler two-dimensional partition mapping multi-satellite and multi-time image enhanced imaging device, wherein a navigation satellite, an imaging device and an earth surface reflection surface form a reflection surface imaging system. A satellite direct signal is received by a right-handed antenna of a receiver, and a satellite reflected signal is received by a left-handed antenna of the receiver. When the satellite is in the range of field of vision of the receiver, specular reflection points of the satellite signal are tracked by the corresponding left-handed antenna to acquire signals, and a signal acquisition region forms a band. According to the imaging device, a plurality of satellites can be tracked at the same moment to form a plurality of bands, the bands formed by tracking each satellite signal have an overlapped region; and the device is used for processing each satellite signal acquired from the overlapped region, and the band region is imaged by utilizing reflection surface characteristic information included by the reflected signal.
Description
Technical Field
The present invention relates to an imaging device based on navigation satellite reflected signals, and more particularly, to an imaging device with multi-channel delay-doppler two-dimensional segmentation mapping multi-satellite multi-time image enhancement
Background
With the development of electronic technology, the requirements of the modern society for military and commercial satellite imaging are higher and higher. Conventional imaging satellites are mainly of the following two types: the first type is an optical imaging reconnaissance satellite, which mainly uses a CCD camera to take a visible light photograph of a ground target at present, and the principle is similar to that of a digital camera used at ordinary times. The existing optical imaging reconnaissance satellite also carries an infrared camera for night reconnaissance, but is easily restricted by meteorological conditions. The CCD camera is difficult to image under the weather conditions of dark night, rain, snow, sand storm, cloudy and the like. The second type is radar imaging reconnaissance satellites. The synthetic aperture radar carried by the satellite is used for transmitting radar waves, and imaging is carried out after receiving reflected waves of a ground target. The image is not as intuitive, fine and vivid as an optical imaging reconnaissance satellite, and the definition is slightly low. However, the radar beam emitted by the satellite can penetrate through the dark night, rain and snow, dense fog, cloud cover and even dry ground surface with a certain depth, so that the satellite has all-weather and twenty-four-hour reconnaissance capability. However, most of the currently used radar imaging satellites are monostatic radars and have many limitations, and the performance of the imaging satellites is far lower than that of bistatic radars, namely the survival capability of anti-radiation missiles, the detection capability of low-altitude targets, the suppression noise interference resistance and the anti-stealth capability. In addition, the existing imaging satellite has inconvenient signal receiving, lower time resolution, more expensive equipment and insufficient application flexibility.
In a real environment, a large number of radio signal sources such as artificial satellites, broadcasting stations, television stations and the like exist, and a convenient radiation source is provided for establishing a non-cooperative bistatic radar. Of these, with satellites as illumination sources, the sky-ground bistatic radar system with receivers on the ground has received increasing attention.
The satellite navigation system can provide high-precision positioning, navigation and time service information for users, and also provides an L-waveband microwave signal resource which is highly stable, can be used for a long time, has higher safety and globality, and can work all day long and all weather.
With the rapid development of the navigation satellite system, a plurality of navigation satellite systems coexist in the space, the navigation satellite signal resources are increasingly abundant, and the feasibility and effectiveness of the technical implementation of receiving the navigation satellite signals reflected by the target object by using the bistatic radar to image the target are increasingly strong.
Disclosure of Invention
The invention aims to provide a multi-channel receiving and processing multi-satellite and multi-time comprehensive enhanced imaging device based on navigation satellite reflected signals.
The invention relates to an imaging device for enhancing multi-satellite and multi-time images by multi-channel time delay Doppler two-dimensional segmentation mapping, which adopts a plurality of groups of receiving antennas capable of intelligently adjusting angles to collect direct and reflected signals, processes the signals by using a multi-channel receiver, images a target by using the time delay Doppler two-dimensional segmentation mapping, enhances the imaging effect in a multi-satellite signal and multi-time signal comprehensive mode, enlarges the imaging range by combining spatial region images and obtains a final image; the method is characterized in that: receiving a navigation satellite k by a certain group of antennasiDirect and reflected signals are connected to a multi-channel GNSS-R according to channelsThe receiver and the multi-channel GNSS-R receiver resolve the direct signal to obtain the basic information of the channel
And satellite signal informationThe orthogonal value and the in-phase value of the reflected signal obtained by processing the reflected signal are recorded as
The receiver sends the channel basic information
The multi-channel antenna receiving angle calculation module is given according to the channel, and the module calculates to obtain the receiving angle epsilon of each group of antennas at the next momentiFeeding back to the antenna servo module, the antenna servo module receiving the angle epsiloniAdjusting the corresponding left-handed antenna; the channel basic information
And satellite signal information
And correlation value of reflected signal
Giving a multi-channel multi-star multi-time image synthesis module; and each channel of the multi-channel GNSS-R receiver provides the basic information of each channel to the antenna servo module to adjust the corresponding angle of the left-handed antenna according to the processing process, provides the basic information of each channel, the satellite signal information and the correlation value of the reflection signal to the multi-channel multi-satellite multi-time image synthesis module, and obtains the image of the detected area after processing.
The satellite reflection signal imaging device has the following advantages:
1) and accumulating the signals of the plurality of navigation satellites simultaneously irradiated on the same area A, and comprehensively processing the signals irradiated on the same area A at different time periods, so that the signal intensity is increased, and the defect of low intensity of reflected signals is overcome.
Satellite ki，kjAt time t1Can illuminate a certain area A internally, for a satellite ki，kjAt time t1The reflected signal correlation power of (a) is accumulated. Satellite kp，kqAt a time period t2Can irradiate the area A and the time t1Inner satellite ki，kjRelative power of the reflected signal to satellite kp，kqAt a time period t2The reflected signal correlation power of (a) is accumulated. Satellite ki，kjSignal at time t3Then, the inner part is shot to the area A again, and t is shot to3Sum of signals in time t2And t1And accumulating the correlation power of the reflected signals in time.
2) Flexible control of imaging range
And accumulating in the same area, and flexibly selecting a measurement range: because of the global coverage of the GNSS satellite, the satellite can illuminate any region around the world, and for a certain imaging region S (including regions a, B, C, and the like), the regions a, B, C, and the like can be detected respectively, and the results are synthesized, so that the whole imaging of the region S can be obtained.
3) Because the navigation satellite signal resource is abundant, the whole day, the global coverage, so utilize this device formation of image not restricted by time, the time resolution is high.
4) The device is low in cost and low in consumption, can be suitable for common users, and has great advantages compared with the traditional imaging satellite receiving equipment which is expensive.
5) The left-handed antenna can adjust the receiving direction, the incident direction of the target object reflected signal is calculated through the motion information of the navigation satellite and the geometric relation between the navigation satellite and the receiver, the receiving direction of the left-handed antenna is adjusted to track the mirror reflection point, target imaging is realized, and the interference of other signals is effectively reduced.
6) The device adopts bistatic (multi-base) radar imaging, and the survival capability of the anti-radiation missile, the low-altitude target detection capability, the suppressed noise interference resistance and the anti-stealth capability of the device are far higher than those of a single-base radar.
7) Long-time signal acquisition, the degree of density of specular reflection points adopted in the physical area is improved.
8) The invention has strong usability and large development space, can increase the number of antennas when in use, and simultaneously tracks a plurality of satellites for imaging; the method is a two-dimensional imaging method, and can be expected to express the roughness of a reflecting surface by utilizing the actual correlation power peak value of a reflection signal and the delay tau at the reflection point of a mirror surface in the future, so that the three-dimensional imaging is realized.
Drawings
Fig. 1 is a block diagram of a conventional navigation satellite imaging apparatus.
FIG. 1A is a schematic view of an imaging strip of a navigation satellite imaging device.
Figure 2 is a single channel imaging process flow diagram of the present invention.
Fig. 3 is a schematic view of a geometric model.
FIG. 4 is a flow chart of the multi-channel multi-star multi-time image composition process of the present invention.
Fig. 5 is a schematic diagram of the relationship between the delay-doppler curve calculation coordinate system and the local coordinate system according to the present invention.
Figure 6 is a schematic of an equal delay line and an equal doppler line.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings.
The invention relates to a multi-satellite multi-time comprehensive enhanced imaging device for receiving and processing direct signals and reflected signals of a navigation satellite by multiple channels.
Referring to fig. 1, a conventional navigation satellite imaging device includes a ground processor, a multi-channel GNSS-R receiver, and a receiving antenna; the ground processor is connected with the multi-channel GNSS-R receiver through a lead, and the receiving antenna is arranged on an information access port of the multi-channel GNSS-R receiver. The receiving antenna comprises p right-handed antennas and p left-handed antennas. The ground processor is composed of a computer and processing software stored in the computer. In the present invention, the processing software running in the computer includes a multi-channel antenna receiving angle calculating module, a multi-channel multi-satellite multi-time image synthesizing module, p antenna angle servo modules and an image combining and processing module (as shown in fig. 2). The multi-channel antenna receiving angle calculating module, the multi-channel multi-satellite multi-time image synthesizing module and the image combining module are written by Microsoft Visual C + +.
In the invention, the lowest configuration of the computer is CPU 2GHz, memory 2GB and hard disk 20 GB; the operating system is windows 2000 and above.
Referring to FIG. 1A, a navigation satellite k is showniThe imaging device and the ground surface reflecting surface form a reflecting surface imaging system. At time t1The receiver receives a navigation satellite k by an ith group of right-handed antennasiDirect signal of
The ith group of left-handed antenna receives the satellite kiReflected signal ofAccompanying toiletThe geometrical relationship between the navigation satellite, the receiver and the reflecting surface changes as the star moves. The receiver antenna tracks the specular reflection point at time tiThe receiver receives a navigation satellite k by an ith group of right-handed antennasiDirect signal of
Navigation satellite k received by ith group of left-handed antennaiReflected signal of
By analogy, the navigation satellite kiWhen the satellite signal is in the visual field range of the receiver, the corresponding left-handed antenna tracks the specular reflection point of the satellite signal to acquire the signal, and the signal acquisition area forms a strip. The device can track a plurality of satellites at the same time to form a plurality of strips, the strips formed by tracking each navigation satellite signal have an overlapping area, the device processes each satellite signal acquired from the overlapping area, and the strip area is imaged by utilizing the characteristic information of the reflecting surface contained in the reflected signal. In practical application, a certain navigation satellite kiAfter the field of view of the corresponding receiving antenna is escaped, or when the receiving antenna is not trackable for other reasons, the setting can be changed to reacquire and track other satellites which can irradiate the same area.
Referring to fig. 2, the imaging device process is described by taking a single channel as an example as follows: receiving a navigation satellite k by a certain group of antennasiThe direct signals and the reflected signals are sent to a multi-channel GNSS-R receiver according to a channel, and the multi-channel GNSS-R receiver resolves the direct signals to obtain basic information of the channel
(including azimuth, altitude, satellite-to-receiver antenna distance, receiver ground clearance, satellite altitude, ionosphere and troposphere state factors, satellite signal-to-noise ratio, etc. of each group of satellites) and satellite signal information
(including signal Doppler and code phase information), the reflected signal is processed to obtain the orthogonal value and the in-phase value of the reflected signal, and the orthogonal value and the in-phase value are recorded as
The receiver sends the channel basic information
The multi-channel antenna receiving angle calculation module is given according to the channel, and the module calculates to obtain the receiving angle epsilon of each group of antennas at the next momentiFeeding back to the antenna servo module, the antenna servo module receiving the angle epsiloniAdjusting the corresponding left-handed antenna; the channel basic information
And satellite signal information
And correlation value of reflected signal
And a multi-channel multi-star multi-time image synthesis module is provided. And each channel of the multi-channel GNSS-R receiver provides the basic information of each channel to the antenna servo module to adjust the corresponding angle of the left-handed antenna according to the processing process, provides the basic information of each channel, the satellite signal information and the correlation value of the reflection signal to the multi-channel multi-satellite multi-time image synthesis module, and obtains the image of the detected area after processing.
The functions realized by each device and a processing module in the imaging device for enhancing the multi-satellite multi-time image by multi-channel time delay Doppler two-dimensional segmentation and mapping are as follows:
(I) right-handed antenna
In the present invention, a right-hand antenna is used for receiving navigation satellites (in k)iFor example) transmitted navigation signals, i.e. direct signalsThe direct signal
Gain amplification of the right-hand antenna forms right-hand circularly polarized signalsAnd outputting the signal to a multi-channel GNSS-R receiver.
(II) left-handed antenna
In the invention, the left-handed antenna is used for receiving the reflected signal reflected by the reflecting surface
The reflected signal
The left-handed circularly polarized signal is formed after the gain amplification of the left-handed antenna
To a multi-channel GNSS-R receiver.
(III) multichannel GNSS-R receiver
In the invention, the input end of the multi-channel GNSS-R receiver is respectively connected with p right-handed antennas and p left-handed antennas; the output end of the multi-channel GNSS-R receiver is connected to a computer of a ground processor.
The multichannel GNSS-R receiver comprises p channels, each channel corresponds to a group of receiving antennas, and at most, p satellite signals received by p groups of antennas can be simultaneously processed to obtain basic information and signal information of the satellite, and in-phase (I path) and quadrature (Q path) values of direct and reflected signals.
The working process of the multi-channel GNSS-R receiver is described by taking an i channel as an example: right-hand circularly polarized signal received by i antenna through i channel pair of multi-channel GNSS-R receiver
Left-handed circularly polarized signalThe treatment comprises the following steps:
(A) for received right-hand circularly polarized signal
Processing to obtain i channel basic informationAnd signal information
And to transmit the basic information
The corresponding channel is sent to a multi-channel antenna receiving angle calculation module to calculate the basic information of each channel
And signal information
The corresponding channel is provided for a multi-channel multi-star multi-time image synthesis module;
(B) for received left-hand circularly polarized signal
Processing to obtain in-phase and quadrature values of left-handed circularly polarized signal
Giving a multi-channel multi-star multi-time image synthesis module;
in the invention, the selected performance parameters of the GNSS-R receiver are as follows:
1) two input ports: p are connected with the right-handed antenna and p are connected with the left-handed antenna;
2) one output port: and receiving the computer.
3) Reflected signal measurement accuracy
Carrier phase measurement accuracy: 0.1 week
Code phase measurement accuracy: 0.01 chip
Doppler measurement accuracy: 3 Hz
4) Data update rate
Reflection signal observation update rate: not less than 1 Hz (optional)
5) Enabling open loop control of a motherboard
6) Conditions of use
Receiver sensitivity better than-175 dBW;
receiver dynamic acceleration: 10g, speed: 1000 m/s
Operating time: all-weather
7) Maximum power consumption: less than or equal to 6 watts
(IV) multichannel antenna receiving angle calculation module
In the invention, a multi-channel antenna receiving angle calculating module calculates the received position information of each satellite and the position information of a receiver to obtain the receiving angle of a left-handed antenna corresponding to the satellite at the next moment, and the calculating process is as follows:
as shown in FIG. 3, the direct navigation satellite signal received by the i antenna can be used to obtain k corresponding to the i antenna after passing through the multi-channel GNSS-R receiveriThe geometric information of the satellite comprises the satellite position and the satellite altitudeSatellite to receiver right-hand antenna distance
Height of receiver from ground
Altitude of satellite
And the like.
(A) When the receiver height is low and the detection range is small, the curvature of the earth is not considered. At this time, k corresponding to the i antenna in the inventioniThe geometric information relationship of the satellite is as follows:
wherein,
the distance of the satellite to the i-slice antenna,is kiThe distance of the satellite from the point of specular reflection,
is the distance of the specular reflection point to the i-left antenna.
Is i leftThe included angle between the rotary antenna and the direction of the nadir.
Is the vertical distance of the receiver from the ground.
(B) When the receiver position is higher, the curvature of the earth needs to be considered, and k corresponding to the i antenna in the inventioniThe geometric information relationship for satellite number (earth approximated as a standard sphere) is:
wherein,
is kiThe distance of the satellite from the i-slice antenna,is kiThe distance of the satellite from the point of specular reflection,
is the distance of the specular reflection point to the i-left antenna.
Is kiThe altitude angle of the satellite is set,
is the included angle between the incident electric wave at the point of the mirror reflection and the tangent plane of the point,
is the included angle between the i-shaped left-handed antenna and the direction of the nadir,
the distance between the receiver and the ground is vertical,
is the satellite vertical distance from the ground, and R is the radius of the earth.
(C) Multi-channel antenna receiving angle calculation module calculates angleThen the antenna servo module is given, and the reception angle of the i-left-handed antenna is adjusted accordingly.
Each channel obtains the receiving angle from the first group to the p-th group according to the processing mode
(V) antenna angle servo module
In the invention, the antenna servo module controls the levorotatory antenna to rotate according to the received azimuth angle and the included angle between the calculated levorotatory antenna and the nadir direction, thereby aligning the reflection point and finishing the collection of the reflection signal.
The antenna servo module is composed of two direct current servo motors, output shafts of the two motors are respectively installed on a clutch, and a left-handed antenna is installed on the other plate surface of the clutch and connected with the left-handed antenna. The mounting of the motor and the left-hand antenna is conventional and will not be described in detail herein.
(VI) multichannel multi-satellite multi-time image synthesis module
As shown in fig. 4, the multi-channel multi-satellite multi-time image synthesis module includes a multi-channel signal imaging processing sub-module, a multi-channel coordinate mapping sub-module, and an image synthesis enhancing module.
The multichannel signal imaging processing submodule receives orthogonal values and in-phase values of reflection signals of all channels transmitted by corresponding channels of the multichannel GNSS-R receiver
To
And carrying out correlation processing under the assistance of delay Doppler information of each channel to obtain a delay Doppler two-dimensional image p of each channel1(fd，τc) To pp(fd，τc) (ii) a And a channel corresponding to the delay Doppler two-dimensional image information is sent to a multi-channel coordinate mapping submodule, the multi-channel coordinate mapping submodule maps the delay Doppler two-dimensional image to an actual coordinate according to the channel, the actual coordinate image information of each channel image is sent to an image comprehensive enhancer module, the image comprehensive enhancer module synthesizes the image information of each channel to obtain a multi-satellite comprehensive image, and the multi-satellite comprehensive image in a certain period of time is processed according to the setting to obtain the multi-satellite multi-time comprehensive image.
The multi-channel signal imaging processing sub-module comprises p channels which respectively correspond to the p channels of the multi-channel GNSS-R receiver. Multi-channel GNSS-R receptionThe machine gives the corresponding basic information of each channel of the multi-channel signal imaging processing submodule according to the channel
To
Signal information
To
And the in-phase and quadrature values of the reflected signalTo
And the multi-channel imaging processing submodule processes the reflected signal to obtain a time delay Doppler two-dimensional image of the signal. Taking channel i as an example, the multi-channel GNSS-R receiver provides the i channel k of the multi-channel signal imaging processing submodule with the multi-channel signaliIn-phase (I-path) and quadrature (Q-path) values of signal reflected from satelliteAnd kiNumber satellite signal information
(including signal Doppler information fdAnd code phase information tauc) Multi-channel imaging processing sub-module pair kiProcessing the signal reflected by the satellite to obtain k corresponding to the channel iiTime delay Doppler two-dimensional image p of signal of satellitei(fd，τc)。
The multi-channel signal imaging processing submodule enables the time delay Doppler two-dimensional image and the basic information of each channel
And mapping the sub-modules to the multi-channel coordinate according to the channels. The multi-channel coordinate mapping submodule comprises a storage unit, a multi-channel equal delay line equal Doppler line calculation unit, a multi-channel map comparison unit and a multi-channel image mapping unit. The storage unit stores the basic information of each channel, a time delay Doppler two-dimensional image, a map of an area to be measured and a proper local two-dimensional coordinate system o-xy set according to the specific situation of the measured terrain, wherein the coordinate plane is a scattering plane of the measured terrain.
And a Doppler line calculation unit such as a multi-channel equal delay line calls the basic information of each channel from the storage unit and establishes a respective temporary coordinate system for calculating the mapping relation between the delay Doppler two-dimensional area division and the actual area in each channel. As shown in fig. 5, taking channel i as an example: establishing a temporary coordinate system on the reflecting surface and the scattering plane
With kiMirror reflection point of signal satellite
As the origin, the tangent plane of the earth at which the specular reflection point is located is taken as the XY plane, kiNumber satellite and specular reflection pointAnd the plane formed by the receiver is YZ plane, and the Y-axis direction points to kiThe Z axis of the satellite is the zenith direction, and the coordinate meets the right-hand principle. Since the measured range is small relative to the radius of the earth, it is considered here that
The z-0 plane of (a) coincides with the xy-plane of o-xy. According to the receiving angle of the i-left-handed antennaAnd kiDetermination of i-channel signal mirror reflection point by number satellite azimuth
Coordinates in the coordinate system o-xy. In a coordinate systemEqual delay line for determining i-channel signal
Hem Doppler line
Let kiNumber satellite to coordinate system
Z is 0 plane distance
Receiver to coordinate systemZ is 0 plane distance
In the present invention, the equal delay lines:
wherein X and Y are coordinate systems
Coordinates of lower, indicating equal delay lines in
A curve under a coordinate system; gamma rayiIs kiSignal satellite transmitter and i-channel signal mirror reflection point
Connecting line and coordinate system
Z is 0 plane angle; deltaiIs a set constant value of kiPath length from signal satellite transmitter to scattering point to receiver and kiThe difference in path length from the satellite transmitter to the specular reflection point to the receiver. In order to ensure the consistency between the delay-doppler two-dimensional area division of multiple channels and the actual area mapping, the same value of delta is usually taken for each channel.
In the present invention, the doppler lines:
wherein X and Y are coordinate systems
Coordinates of lower, indicating equal Doppler lines at
A curve under a coordinate system; gamma rayiIs kiSignal satellite transmitter and i-channel signal mirror reflection point
Connecting line and coordinate system
Z is 0 plane angle;
is the receiver to ground height;
respectively receiver speed according to
Vectors of coordinates in all directions;
are each kiNumber satellite velocity is
Vectors of coordinates in all directions;
the set i-channel signal Doppler value is constant; λ is the original wavelength of the wave source.
Coordinate system using the following coordinate conversion relation
The coordinate conversion relation of the lower i-channel signal under the condition that the equal delay line and the equal Doppler line are converted into the local coordinate system o-xy is as follows: <math>
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The multi-channel map comparison unit calls an actual map of the area to be measured from the storage unit (the coordinate of the actual map adopts a preset value coordinate system o-xy), obtains equal delay lines and equal Doppler line curves of all channels from the multi-channel equal delay line equal Doppler line calculation unit, compares the equal delay lines and the equal Doppler lines with the actual map near the mirror reflection point of each channel to obtain the corresponding relation between equal delay equal Doppler area segmentation and the actual physical area coordinate of each channel
The multi-channel image mapping unit calls the basic information of each channel and the time delay Doppler two-dimensional image of each channel from the storage unit, taking the i channel as an example, and receives the time delay Doppler two-dimensional image p of the i channeli(fd，τc) Later calling the corresponding relation obtained from the multi-channel map comparison unit
Mapping the time delay Doppler two-dimensional image to an actual physical area to obtain a receiving time tiSingle star image of real area
And imaging the reflecting surface is realized. And connect the actual zones of the channelsAnd the domain single star image is sent to the image comprehensive enhancement submodule according to the channel.
As shown in fig. 6, one area element of the two-dimensional delay-doppler image corresponds to two area elements formed by the equal delay area and the equal doppler area in the actual physical area. The invention solves the problem by controlling the antenna coverage area, and the left-handed antenna coverage area is designed to only comprise one of two area elements formed by an equal delay area and an equal Doppler area, so that the problem of signal imaging overlapping of the two areas is effectively avoided.
The image comprehensive enhancer module comprises a multi-star weight distribution unit, a multi-star image comprehensive enhancement unit, a storage unit A, a multi-time weight distribution unit, a multi-time image comprehensive enhancement unit and a storage unit B.
And the multi-satellite weight value distribution unit acquires the image information and the basic information of each channel from the multi-channel coordinate mapping submodule and distributes the multi-satellite weight value according to the basic information of each channel to counteract the influence of geometric factors, troposphere ionosphere and other factors on image enhancement processing. Taking channel i as an example, tiTime image informationThe multi-star weight value distribution unit distributes the multi-star weight value to the multi-star weight value distribution unit
The multi-satellite image comprehensive enhancement unit acquires each channel t from the multi-satellite weight distribution unitiThe time image information, the multi-satellite weight value and the basic information of each channel. Multi-satellite image comprehensive enhancement unit for enhancing basic information of each channel
Extracting troposphere and ionosphere state factors air in the process of collecting informationtiAnd carrying out comprehensive enhancement processing on the image information of each channel according to the coordinates of an o-xy coordinate system: <math>
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</msub>
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</msub>
<msub>
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</math>
whereinIs tiEach channel integrates the enhanced image information at all times,
is tiThe image information of the channel at the moment i has a multi-satellite weight,
is tiTime i channel image information.
The multi-star image comprehensive enhancing unit is used for enhancing tiTime-based comprehensive enhancement of image information of each channel
And the time tiIntegral tropospheric and ionospheric state factors airtiAnd storing the data in the memory unit A. The multi-time weight value distribution unit calls the multi-satellite comprehensive enhanced image at different moments from the storage unit A
According to the troposphere and ionosphere state factors air at each momenttiAnd distributing multi-time weights to offset the influences of factors such as troposphere and ionosphere states at different moments.
The multi-time image comprehensive enhancement unit acquires multi-satellite comprehensive enhancement images at different moments and multi-time weights at the moments from the multi-time weight distribution unit, and performs comprehensive enhancement processing according to coordinates of an o-xy coordinate system:
wherein,
is tiThe image information is comprehensively enhanced by a plurality of stars at the moment,
is tiMultiple time weight, P, of time-multiple star comprehensive enhanced imagesumAnd (x, y) is a multi-star multi-time comprehensive enhanced image. m is a time interval comprehensive index, and represents the frequency of image updating, namely imagingThe time resolution of (2) is set according to the specific situation.
The multi-time image comprehensive enhancement unit comprehensively enhances the image information P by multiple stars and multiple timessum(x, y) to the storage unit B, which outputs an image of the detected physical area upon receiving the output command.
(VII) image combination processing module
The image combination processing module combines the formed strip images according to the requirements so as to realize the imaging of a larger area and a more flexible area. The image combination processing module combines the images of the imaged strips according to a coordinate system o-xy:
by the way of analogy, the method can be used,
wherein, Pi(x, y) (i ═ 1, 2.. m) image information of a subregion of a certain whole region, or a certain whole region image information segmented representation;
imaging information for Ai regions; ps(x, y) is the integral imaging information of the combined area; n is the number of the spatial combination strips of the imaging area and can be set according to specific conditions.
According to the method, the direct and reflected signals of the navigation satellite are received and processed, the target area imaging function is completed by utilizing a time delay Doppler two-dimensional segmentation mapping method, and the image enhancement is performed by a multi-satellite multi-time comprehensive processing method. An imaging device is realized that is low in cost, high in spatial-temporal resolution, small in interference, flexible and scalable.
Claims (3)
1. A multi-channel time delay Doppler two-dimensional segmentation mapping multi-satellite multi-time image enhanced imaging device adopts multiple groups of receiving antennas capable of intelligently adjusting angles to collect direct and reflected signals, utilizes a multi-channel receiver to process the signals, utilizes time delay Doppler two-dimensional segmentation mapping to image a target, enhances the imaging effect in a multi-satellite signal multi-time signal comprehensive mode, and enlarges the imaging range through spatial region image combination to obtain a final image; the method is characterized in that: receiving a navigation satellite k by a certain group of antennasiDirect and reflected signals of the channel-by-channel multi-channel GNSS-R receiverThe direct signal is resolved by a multi-channel GNSS-R receiver to obtain the basic information of the channel
And satellite signal information
The orthogonal value and the in-phase value of the reflected signal obtained by processing the reflected signal are recorded asThe receiver sends the channel basic information
The receiving angle of each group of antennas at the next moment is calculated by a multi-channel antenna receiving angle calculating module according to the channelsFeeding back to the antenna servo module according to the received angle
Adjusting the corresponding left-handed antenna; the channel basic information
And satellite signal information
And correlation value of reflected signal
Giving a multi-channel multi-star multi-time image synthesis module; according to the processing procedure, each channel of the multi-channel GNSS-R receiver provides the basic information of each channel to the antenna servo module to adjust the corresponding angle of the left-handed antenna, and provides the basic information of each channel and the satellite signal informationAnd providing the correlation values of the information and the reflection signals to a multi-channel multi-satellite multi-time image synthesis module, and processing to obtain an image of the detected region.
2. The imaging device for multi-channel delay-doppler two-dimensional segmentation mapping multi-satellite multi-time image enhancement according to claim 1, wherein: the multi-channel antenna receiving angle calculating module calculates the received position information of each satellite and the position information of the receiver to obtain the receiving angle of the levorotatory antenna corresponding to the satellite at the next moment, and the calculating process is as follows:
the direct navigation satellite signal received by the i antenna can obtain k corresponding to the i antenna after passing through the multi-channel GNSS-R receiveriThe geometric information of the satellite comprises the satellite position and the satellite altitude
Satellite to receiver right-hand antenna distanceHeight of receiver from ground
Altitude of satellite
(A) When the receiver height is low and the detection range is small, the curvature of the earth is not considered; at this time, k corresponding to the i antennaiThe geometric information relationship of the satellite is as follows:
(B) when the receiver is at a higher position, the curvature of the earth needs to be considered, and k corresponding to the i antenna is the sameiThe geometric information relationship of the satellite is as follows:
wherein,is kiThe distance of the satellite from the i-slice antenna,
is kiThe distance of the satellite from the point of specular reflection,
is the distance from the specular reflection point to the i-left antenna;
is kiThe altitude angle of the satellite is set,
is the included angle between the incident electric wave at the point of the mirror reflection and the tangent plane of the point,
is the included angle between the i-shaped left-handed antenna and the direction of the nadir,
the distance between the receiver and the ground is vertical,
the vertical distance between the satellite and the ground, and R is the radius of the earth;
(C) multi-channel antenna receiving angle calculation module calculates angle
Then the antenna servo module is given, and the reception angle of the i-left-handed antenna is adjusted accordingly.
3. The imaging device for multi-channel delay-doppler two-dimensional segmentation mapping multi-satellite multi-time image enhancement according to claim 1, wherein: the multi-channel multi-satellite multi-time image synthesis module comprises a multi-channel signal imaging processing sub-module, a multi-channel coordinate mapping sub-module and an image synthesis enhancer module;
the multichannel signal imaging processing submodule receives orthogonal values and in-phase values of reflection signals of all channels transmitted by corresponding channels of the multichannel GNSS-R receiverTo
And carrying out correlation processing under the assistance of delay Doppler information of each channel to obtain a delay Doppler two-dimensional image p of each channel1(fd,τc) To pp(fd,τc) (ii) a The multi-channel coordinate mapping submodule maps the delay Doppler two-dimensional image to an actual coordinate according to the channel, the multi-channel coordinate mapping submodule sends the actual coordinate image information of each channel image to the image comprehensive enhancer module, the image comprehensive enhancer module synthesizes the image information of each channel to obtain a multi-satellite comprehensive image, and then the multi-satellite comprehensive image in a certain period of time is processed according to the setting to obtain a multi-satellite and multi-time comprehensive image;
the multi-channel signal imaging processing submodule enables the time delay Doppler two-dimensional image and the basic information of each channel
Mapping the sub-modules to the multi-channel coordinates according to the channels; the multi-channel coordinate mapping submodule comprises a storage unit, a multi-channel equal delay line equal Doppler line calculation unit, a multi-channel map comparison unit and a multi-channel image mapping unit; the storage unit stores basic information of each channel, a time delay Doppler two-dimensional image, a map of a region to be measured and a proper local two-dimensional coordinate system o-xy set according to the specific situation of the measured terrain, wherein the coordinate plane is a scattering plane of the measured ground;
a multi-channel equal delay line equal Doppler line calculation unit calls basic information of each channel from a storage unit and establishes respective temporary coordinate systems for calculating the mapping relation between the delay Doppler two-dimensional area division and the actual area in each channel;
according to the receiving angle of the i-left-handed antenna
And kiDetermination of i-channel signal mirror reflection point by number satellite azimuth
Coordinates in a coordinate system o-xy; in a coordinate system
Equal delay line for determining i-channel signal
Hem Doppler line
Let kiNumber satellite to coordinate system
Z is 0 plane distanceReceiver to coordinate system
Z is 0 plane distance
The equal delay line:
wherein X and Y are coordinate systems
Coordinates of lower, indicating equal delay lines in
A curve under a coordinate system; gamma rayiIs kiSignal satellite transmitter and i-channel signal mirror reflection pointConnecting line and coordinate system
Z is 0 plane angle; deltaiIs a set constant value of kiPath length from signal satellite transmitter to scattering point to receiver and kiThe difference of the path length from the signal satellite transmitter to the mirror reflection point to the receiver; in order to ensure the consistency of the time delay Doppler two-dimensional area division of the multiple channels and the actual area mapping, the same delta value is taken by each channel;
the equal Doppler lines: <math>
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wherein X and Y are coordinate systems
Coordinates of lower, indicating equal Doppler lines at
A curve under a coordinate system; gamma rayiIs kiSignal satellite transmitter and i-channel signal mirror reflection point
Connecting line and coordinate system
Z is 0 plane angle;
is the receiver to ground height;
respectively receiver speed according to
Vectors of coordinates in all directions;are each kiNumber satellite velocity isVectors of coordinates in all directions;
setting the Doppler value of the i-channel signal as a constant, wherein lambda is the wavelength of the original wave source;
coordinate system using the following coordinate conversion relationThe equal delay lines and the equal Doppler lines of the lower i-channel signals are converted to the local coordinate system o-xy:
the coordinate conversion relation is as follows: <math>
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wherein X and Y are coordinate systems
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The distance between the origin and the coordinate o-xy origin on the y-axis of the o-xy coordinate, β beingThe included angle between the X axis of the coordinate system and the X axis of the o-xy coordinate system;
the multi-channel map comparison unit calls an actual map of a region to be detected from the storage unit, obtains equal delay lines and equal Doppler line curves of all channels from the multi-channel equal delay line equal Doppler line calculation unit, compares the equal delay lines and the equal Doppler lines with the actual map near the mirror reflection point of each channel, and obtains the corresponding relation between equal delay equal Doppler region segmentation and actual physical region coordinates of each channel
The multi-channel image mapping unit calls the basic information of each channel and the time delay Doppler two-dimensional image of each channel from the storage unit, and for the channel i, the time delay Doppler two-dimensional image p of the channel i is receivedi(fd,τc) Later calling the corresponding relation obtained from the multi-channel map comparison unit
Mapping the time delay Doppler two-dimensional image to an actual physical area to obtain a receiving time tiSingle star image of real area
Realizing imaging of the reflecting surface; and the single star image of the actual area of each channel is sent to the image comprehensive enhancement submodule according to the channel.
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