CN115441900B - Information-assisted high-dynamic weak spread spectrum signal rapid capturing method and device - Google Patents
Information-assisted high-dynamic weak spread spectrum signal rapid capturing method and device Download PDFInfo
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- CN115441900B CN115441900B CN202211400692.XA CN202211400692A CN115441900B CN 115441900 B CN115441900 B CN 115441900B CN 202211400692 A CN202211400692 A CN 202211400692A CN 115441900 B CN115441900 B CN 115441900B
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/69—Spread spectrum techniques
- H04B1/707—Spread spectrum techniques using direct sequence modulation
- H04B1/7073—Synchronisation aspects
- H04B1/7075—Synchronisation aspects with code phase acquisition
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/38—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system
- G01S19/39—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system the satellite radio beacon positioning system transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
- G01S19/42—Determining position
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01S—RADIO DIRECTION-FINDING; RADIO NAVIGATION; DETERMINING DISTANCE OR VELOCITY BY USE OF RADIO WAVES; LOCATING OR PRESENCE-DETECTING BY USE OF THE REFLECTION OR RERADIATION OF RADIO WAVES; ANALOGOUS ARRANGEMENTS USING OTHER WAVES
- G01S19/00—Satellite radio beacon positioning systems; Determining position, velocity or attitude using signals transmitted by such systems
- G01S19/38—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system
- G01S19/39—Determining a navigation solution using signals transmitted by a satellite radio beacon positioning system the satellite radio beacon positioning system transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
- G01S19/52—Determining velocity
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/69—Spread spectrum techniques
- H04B1/707—Spread spectrum techniques using direct sequence modulation
- H04B1/7073—Synchronisation aspects
- H04B1/7087—Carrier synchronisation aspects
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B7/00—Radio transmission systems, i.e. using radiation field
- H04B7/01—Reducing phase shift
Abstract
The application relates to a method and a device for quickly capturing high-dynamic weak spread spectrum signals with the aid of information. The method comprises the following steps: acquiring position information and real-time speed information of the space station according to a GNSS receiver carried on the space station, and calculating the position information to obtain the radial speed of the space station relative to a ground base station; calculating according to the radial velocity and the carrier frequency of the spread spectrum signal to obtain the Doppler frequency shift of the carrier; compensating the intermediate frequency signal after the down-conversion according to the Doppler frequency shift to obtain the actual intermediate frequency of the received signal; the actual intermediate frequency of the received signal is a search result of the received signal in a frequency domain; estimating code Doppler according to the Doppler frequency shift, the carrier frequency and the pseudo code rate, and further adjusting the locally generated pseudo code rate; and (4) searching the time domain of the received signal in a parallel mode to obtain a search result of the received signal in the time domain. The method can realize the rapid acquisition of the space station spread spectrum signal.
Description
Technical Field
The present invention relates to the field of spatial time-frequency transmission technologies, and in particular, to a method and an apparatus for quickly capturing a high-dynamic weak spread spectrum signal with information assistance.
Background
With the development of the manned space station technology in China, for the capture of satellite spread spectrum signals, most typically satellite navigation signals broadcast by a satellite navigation system, a ground receiver realizes the solution of pseudorange and carrier phase measurement values by receiving the satellite navigation signals, and the position of the receiver can be solved according to the measurement results of at least four satellites. The satellite navigation system satellite mainly comprises a Geostationary Earth Orbit (GEO) satellite and a Medium Earth Orbit (MEO) satellite, and for acquisition of satellite navigation signals, the essence of the acquisition is to perform two-dimensional search of a time domain and a frequency domain on received signals to respectively obtain a doppler frequency shift and a pseudo code phase of the received signals. Compared with a navigation satellite signal, a spread spectrum signal in a microwave link time-frequency transmission system carried on a space station has lower satellite orbit height, so that the high dynamic characteristic is more prominent, the speed and acceleration change range between a ground receiver and the space station is larger, the Doppler frequency shift change range is larger, and the Doppler frequency shift change rate is larger; however, in the reception and detection of a weak signal, it is necessary to increase the integration time to improve the detection sensitivity, and thus the contradiction between the two is significant.
Aiming at signal capture under a high dynamic condition, the direct influence of the method is that the Doppler frequency shift change range is larger, so that the range of frequency domain search for signals is enlarged, and the frequency can be searched in parallel by a search method based on fast Fourier transform, so that the calculation amount required by signal capture is reduced, the capture speed is accelerated, and sufficient time can be reserved for increasing coherent integration time. Meanwhile, the change rate of the Doppler frequency shift is increased under the high dynamic condition, and the increase of the coherent integration time is limited. On one hand, the signal capture is required under the high dynamic condition, and the two-dimensional searching speed of the time domain and the frequency domain is as high as possible; on the other hand, to improve the signal acquisition sensitivity, it is necessary to increase the coherent integration time and use a non-coherent integration method. It is necessary to propose a new method to achieve the compromise and the comprehensive consideration of the two.
Disclosure of Invention
Therefore, in order to solve the above technical problems, a method and an apparatus for fast capturing a high dynamic weak spread spectrum signal are provided, which can fast capture a space station or a low orbit satellite-ground microwave time-frequency ratio link spread spectrum signal.
A method for information-assisted fast acquisition of a high-dynamic weak spread spectrum signal, the method comprising:
acquiring position information and real-time speed information of the space station according to a GNSS receiver carried on the space station, and calculating the position information to obtain angle information between the ground stations;
calculating by utilizing the real-time speed information and the angle information between the ground stations to obtain the radial speed of the space station relative to the ground base station;
calculating according to the radial velocity and the carrier frequency of the spread spectrum signal to obtain the Doppler frequency shift of the carrier;
carrying out down-conversion on the carrier, and compensating the intermediate frequency signal after down-conversion according to Doppler frequency shift to obtain the actual intermediate frequency of the received signal; the actual receiving signal intermediate frequency is used as a capturing search result of the receiving signal in a frequency domain;
estimating code Doppler according to the Doppler frequency shift, the carrier frequency and the pseudo code rate to obtain a local pseudo code rate; generating local pseudo codes by using the local pseudo code rate;
the method comprises the steps of searching a receiving number phase in parallel, multiplying and mixing digital intermediate-frequency signals with local copy sine carrier signals and local copy cosine carrier signals on an I branch and a Q branch respectively after the digital intermediate-frequency signals collected by an analog-to-digital converter are obtained, and obtaining a mixing result; the frequency of the local copy sine carrier signal and the local copy cosine carrier signal is the actual receiving signal intermediate frequency;
performing Fourier transform on the frequency mixing result in a complex form, multiplying the transform result by the conjugate of the Fourier transform result of the local pseudo code, and performing Fourier inverse transform on the product to obtain the acquisition search result of the received signal and the local signal in a time domain; and the acquisition search result of the received signal in the frequency domain and the acquisition search result of the received signal in the time domain are signal acquisition results.
In one embodiment, the position information and the real-time speed information output by the GNSS receiver continuously and repeatedly at the current time are used for estimating the doppler information of the space station relative to the ground at the next time, and the high-order compensation is performed on the doppler frequency shift caused by the movement of the space station relative to the ground base station according to the obtained doppler frequency shift prediction estimation value.
In one embodiment, the distance between the space station and the ground station is calculated according to the space station position coordinates output by the GNSS receiver, and the signal transmission delay is determined by using the distance between the space station and the ground station; determining a time domain code phase capturing range according to the signal transmission delay;
determining a signal transmission delay as a function of the distance between the space station and the ground station
Wherein the content of the first and second substances,
the position coordinates of the ground base station are represented,
representing spatial stations at time of day
The location information of (a) is stored in the storage unit,
indicating the time of day
The distance between the space station and the ground base station,
indicating the speed of light.
In one embodiment, calculating the position information to obtain the angle information between the ground stations comprises:
the position information is calculated to obtain the angle information between the ground stations as
In one embodiment, the calculating by using the real-time speed information and the angle information between the ground stations to obtain the radial speed of the space station relative to the ground base station includes:
calculating by utilizing the real-time speed information and the angle information between the ground stations to obtain the radial speed of the space station relative to the ground base station
Wherein the content of the first and second substances,
representing spatial stations at time of day
Real-time speed information.
In one embodiment, calculating the doppler shift of the carrier according to the radial velocity and the carrier frequency of the spread spectrum signal includes:
calculating according to the radial velocity and the carrier frequency of the spread spectrum signal to obtain the Doppler frequency shift of the carrier wave as
Wherein, in the step (A),
which represents the carrier frequency of the spread-spectrum signal,
indicating the speed of light.
In one embodiment, the compensating the down-converted intermediate frequency signal according to the doppler shift to obtain the actual intermediate frequency of the received signal includes:
compensating the intermediate frequency signal after down-conversion according to the Doppler frequency shift to obtain the intermediate frequency of the actual receiving signal
Wherein, in the process,
representing an intermediate frequency signal.
In one embodiment, estimating code doppler according to doppler shift, carrier frequency, and pseudo code rate to obtain local pseudo code rate includes:
estimating code Doppler according to Doppler frequency shift, carrier frequency and pseudo code rate to obtain code Doppler
Wherein, in the process,
representing a pseudo code rate of a ground station transmission;
and adding the code Doppler and the pseudo code rate to obtain the local pseudo code rate.
An information-assisted high-dynamic weak spread spectrum signal fast acquisition device, the device comprising:
the radial velocity calculation module is used for acquiring the position information and the real-time velocity information of the space station according to the GNSS receiver carried on the space station, and calculating the position information to obtain the angle information between the ground stations; calculating by utilizing the real-time speed information and the angle information between the ground stations to obtain the radial speed of the space station relative to the ground base station;
the Doppler frequency shift calculation module is used for calculating according to the radial velocity and the carrier frequency of the spread spectrum signal to obtain the Doppler frequency shift of the carrier;
the signal frequency domain searching module is used for carrying out down-conversion on the carrier wave, compensating the down-converted intermediate frequency signal according to Doppler frequency shift and obtaining the actual intermediate frequency of the received signal; the actual receiving signal intermediate frequency is used as a capturing search result of the receiving signal in a frequency domain;
the signal time domain searching module is used for estimating code Doppler according to the Doppler frequency shift, the carrier frequency and the pseudo code rate to obtain a local pseudo code rate; generating a local pseudo code by using the local pseudo code rate; the method comprises the steps of searching a receiving number phase in parallel, multiplying and mixing digital intermediate-frequency signals with local copy sine carrier signals and local copy cosine carrier signals on an I branch and a Q branch respectively after the digital intermediate-frequency signals collected by an analog-to-digital converter are obtained, and obtaining a mixing result; the frequency of the local copy sine carrier signal and the local copy cosine carrier signal is the actual intermediate frequency of the received signal; performing Fourier transform on the frequency mixing result in a complex form, multiplying the transform result by the conjugate of the Fourier transform result of the local pseudo code, and performing Fourier inverse transform on the product to obtain the acquisition search result of the received signal and the local signal in a time domain; and the acquisition search result of the received signal in the frequency domain and the acquisition search result of the received signal in the time domain are signal acquisition results.
According to the information-assisted high-dynamic weak spread spectrum signal rapid capturing method, the information-assisted high-dynamic weak spread spectrum signal rapid capturing device, the computer equipment and the storage medium, the GNSS receiver carried on the space station is used for obtaining the position information and the real-time speed information of the space station, and the radial speed change of the space station relative to the ground base station is obtained through calculation based on the position information and the real-time speed information, so that the Doppler frequency offset of a carrier wave of a spread spectrum signal is obtained through estimation, the Doppler frequency offset of the signal can be obtained through rapid and accurate estimation, the integration time can be effectively prolonged, the signal integration gain is improved, and the weak signal capturing capability is enhanced; estimating code Doppler according to the carrier Doppler frequency shift, the carrier frequency and the pseudo code rate obtained by calculation, and further adjusting the rate of locally generated pseudo codes to generate local pseudo codes; and (3) searching a received signal time domain in a parallel mode, multiplying and mixing the digital intermediate frequency signal with a local copy sine carrier signal and a copy cosine carrier signal on an I branch and a Q branch respectively after the digital intermediate frequency signal acquired by the analog-to-digital converter is obtained, wherein the local copy carrier frequency is the actual received signal intermediate frequency considering Doppler frequency shift. Fourier transformation is carried out on the frequency mixing result in a complex form, the transformation result is multiplied by the conjugate of the Fourier transformation result of the local pseudo code, then inverse Fourier transformation is carried out on the product, the correlation result of the received signal and the local signal in a time domain is obtained, the time domain and frequency domain two-dimensional searching process of traditional signal capturing is simplified into a time domain one-dimensional searching process, and the capturing speed is obviously improved.
Drawings
Fig. 1 is a schematic flowchart illustrating a method for fast acquisition of a highly dynamic weak spread spectrum signal with information assistance according to an embodiment;
FIG. 2 is a diagram illustrating calculation of Doppler shift of a carrier wave caused by motion of a spatial station in one embodiment;
FIG. 3 is a diagram illustrating signal acquisition decisions in one embodiment;
FIG. 4 is a diagram illustrating GNSS receiver information in two consecutive time instances to assist in calculating Doppler shift caused by the motion of the space station platform relative to the ground base station in another embodiment;
fig. 5 is a block diagram of an apparatus for fast acquisition of information-aided high-dynamic weak spread spectrum signals according to an embodiment.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the present application is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.
In one embodiment, as shown in fig. 1, there is provided an information-aided fast acquisition method for a high-dynamic weak spread spectrum signal, comprising the following steps:
102, acquiring position information and real-time speed information of a space station according to a GNSS receiver carried on the space station, and calculating the position information to obtain angle information between ground stations; and calculating by utilizing the real-time speed information and the angle information between the ground stations to obtain the radial speed of the space station relative to the ground base station.
And 104, calculating according to the radial velocity and the carrier frequency of the spread spectrum signal to obtain the Doppler frequency shift of the carrier.
The method comprises the steps that a GNSS receiver carried on a space station is used for obtaining position information and real-time speed information of the space station, and radial speed change of the space station relative to a ground base station is obtained through calculation based on the position information and the real-time speed information, so that Doppler frequency offset of spread spectrum signals is obtained through estimation, the Doppler frequency offset of the signals can be obtained through rapid and accurate estimation, integration time can be effectively prolonged, signal integration gain is improved, and weak signal capturing capacity is enhanced.
The method for searching the parallel code phase is adopted, the code phase search in the capture range is completed at one time through Fourier transform, the time domain and frequency domain two-dimensional search process of the traditional signal capture is simplified into a time domain one-dimensional search process, the frequency domain dimension search is completed by means of information assistance, and the capture speed is obviously improved.
In the information-assisted high-dynamic weak spread spectrum signal rapid capturing method, the GNSS receiver carried on the space station is used for obtaining the position information and the real-time speed information of the space station, and the radial speed change of the space station relative to the ground base station is calculated and obtained based on the position information and the real-time speed information, so that the Doppler frequency offset of the carrier wave of the spread spectrum signal is obtained by estimation, the Doppler frequency offset of the signal can be quickly and accurately obtained by estimation, the integral time can be effectively prolonged, the signal integral gain is improved, and the weak signal capturing capability is enhanced; estimating code Doppler according to the carrier Doppler frequency shift, the carrier frequency and the pseudo code rate obtained by calculation, and further adjusting the rate of locally generated pseudo codes to generate local pseudo codes; and (3) searching a received signal time domain in a parallel mode, multiplying and mixing the digital intermediate frequency signal with a local copy sine carrier signal and a copy cosine carrier signal on an I branch and a Q branch respectively after obtaining the digital intermediate frequency signal collected by the analog-to-digital converter, wherein the local copy carrier frequency is the actual received signal intermediate frequency considering Doppler frequency shift. And Fourier transformation is carried out on the frequency mixing result in a complex form, the transformation result is multiplied by the conjugate of the Fourier transformation result of the local pseudo code, and then Fourier inversion is carried out on the product to obtain the relevant result of the received signal and the local signal in a time domain.
In one embodiment, the position information and the real-time speed information output by the GNSS receiver continuously and repeatedly at the current time are used for estimating the doppler information of the space station relative to the ground at the next time, and the high-order compensation is performed on the doppler frequency shift caused by the movement of the space station relative to the ground base station according to the obtained doppler frequency shift prediction estimation value.
In a specific embodiment, the doppler information of the space station relative to the ground can be predicted in advance by using the auxiliary information output by the GNSS receiver for a plurality of times in succession, so as to improve the instantaneous accuracy. In consideration of the solving delay, the data transmission delay and the data output frequency limitation of the GNSS receiver, the microwave link load receives auxiliary information of the GNSS receiver with a certain delay, and under a high dynamic condition, the information delay can cause large deviation and influence the capturing performance.
The high-order compensation can be performed on the Doppler frequency shift caused by the movement of the space station platform relative to the ground base station by using the position coordinates and the velocity vector output values of the GNSS receiver at two continuous moments, so that the high-order compensation can be more suitable for dynamic conditions under the condition that the output frequency of the GNSS receiver is limited, the estimation precision of the Doppler frequency shift is improved, the coherent integral gain loss is reduced, and the capture sensitivity is improved.
As shown in fig. 4, in order to estimate and compensate the doppler shift more accurately, the doppler shift in a short time can be modeled as a linear change by using the output measurement values of the GNSS receiver at two consecutive time instants. Therefore, the method can better adapt to dynamic conditions under the condition that the output frequency of the GNSS receiver is limited, improve the estimation precision of the Doppler frequency shift, further reduce the coherent integration gain loss and improve the capture sensitivity.
GNSS receiver carried by space station platform
，
And
time-of-day respectively output position coordinates
，
，
The instantaneous velocity vectors are respectively
，
，
Wherein
Then, then
Mean value of velocity component of space station platform in direction of connecting with ground base station at time
Can be expressed as
Considering that the time interval between two successive positioning and speed measurement results output by the GNSS receiver is generally short, the platform speed variation can be approximately linear fit, and in this case, the platform speed variation is then
-
The acceleration in the time interval may be expressed as
Then is at
To
At any time within a time interval
The velocity component of the space station platform in the direction of the connection line of the space station platform and the ground base station
Can be expressed as:
similarly, the next time the GNSS receiver output aiding information is received in the microwave link
Previously, it was assumed that the relative velocity was uniformly changed and the acceleration was
On the basis of the above-mentioned operation, can be used for
And forecasting the satellite-ground relative speed in the time period to provide prior information for the acquisition of the load signal of the microwave link.
At any time within a time interval
Velocity component of space station platform in direction of connecting line of space station platform and ground base station
Can be expressed as:
further can obtain
Time of day, estimated Doppler shift of received signal due to satellite platform motion
Then according to the above formula, utilize
，
Time GNSS receiver output value pair
And predicting and estimating the Doppler frequency shift of the time receiving signal to obtain:
according to
The output value of the GNSS receiver at the moment is directly obtained by calculation
The Doppler frequency shift of the carrier wave of the received signal at the moment is as follows:
under the condition that the output information frequency of the GNSS receiver is 1Hz in the dynamic environment, the carrier Doppler estimated error obtained by adopting the method provided by the invention is as follows
And the signal acquisition requirement can be met.
In one embodiment, the distance between the space station and the ground station is calculated according to the space station position coordinates output by the GNSS receiver, and the signal transmission delay is determined by using the distance between the space station and the ground station; determining a time domain code phase capturing range according to the signal transmission delay;
determining signal transmission time delay by using distance between space station and ground station
Wherein the content of the first and second substances,
the location coordinates of the terrestrial base stations are represented,
representing spatial stations at time of day
The location information of (a) is stored in the storage unit,
indicating the time of day
The distance between the space station and the ground base station,
indicating the speed of light.
In a specific embodiment, the signal transmission delay is roughly determined by using auxiliary information output by a space station platform carrying GNSS receiver, so that the time domain code phase capturing range is shortened, and the capturing efficiency is improved. Because the transmission link of the space station for receiving the signal transmitted by the ground station is longer, compared with the code phase at the transmitting moment, the receiving code phase is generated for the time length
The pseudo code rate is also shifted by the doppler shift, resulting in uncertainty in the delay of the received code phase compared to the transmitted code. The GNSS receiver outputs the position coordinates of the space station platform, the distance between the space station platform and the ground station is calculated, the signal transmission time delay is estimated, namely, the TOA (time of arrival) estimation is carried out, the signal code phase is captured on the basis, the code phase searching range is reduced to the equivalent magnitude of the estimated residual error of the signal transmission time delay, and the code phase searching can be carried outThe speed is remarkably improved.
In one embodiment, calculating the position information to obtain the angle information between the ground stations includes:
the position information is calculated to obtain the angle information between the ground stations as
In one embodiment, the calculating by using the real-time speed information and the angle information between the ground stations to obtain the radial speed of the space station relative to the ground base station includes:
calculating by utilizing the real-time speed information and the angle information between the ground stations to obtain the radial speed of the space station relative to the ground base station
Wherein the content of the first and second substances,
representing spatial stations at time of day
Real-time speed information.
In one embodiment, calculating the doppler shift of the carrier according to the radial velocity and the carrier frequency of the spread spectrum signal includes:
calculating according to the radial velocity and the carrier frequency of the spread spectrum signal to obtain the Doppler frequency shift of the carrier wave as
Wherein, in the step (A),
which represents the carrier frequency of the spread-spectrum signal,
indicating the speed of light.
In one embodiment, compensating the down-converted intermediate frequency signal according to the doppler shift to obtain an actual intermediate frequency of the received signal includes:
compensating the intermediate frequency signal after down-conversion according to the Doppler frequency shift to obtain the intermediate frequency of the actual receiving signal
Wherein, in the step (A),
representing the intermediate frequency signal.
In one embodiment, estimating code doppler according to doppler shift, carrier frequency and pseudo code rate to obtain local pseudo code rate, includes:
estimating the code Doppler according to the Doppler frequency shift, the carrier frequency and the pseudo code rate to obtain the code Doppler
Wherein, in the step (A),
representing a pseudo code rate of a ground station transmission;
and adding the code Doppler and the pseudo code rate to obtain the local pseudo code rate.
In a specific embodiment, as shown in fig. 2, the space station platform operates on a low earth orbit with an orbit height of 400KM, which requires receiving the signals transmitted by the capture ground station at a carrier frequency of
The pseudo code rate is
Because the orbit of the space station platform is low, the received signal needs to face the conditions of large frequency deviation and high dynamic. If it isBy adopting the Ka frequency band link commonly used in the existing satellite-ground communication, the Doppler frequency offset of the link reaches hundreds of kHz magnitude, and the traditional acquisition method cannot complete the search.
The GNSS receiver carried on the space station platform can give the time of the space station platform under the WGS-84 coordinate system
Position information of
Instantaneous velocity of
Meanwhile, under the coordinate system, the ground base station selects the coordinates of a place and the position in China
The data is stored in the memory of the space station platform and can also be uploaded by means of instructions. The time of day can be calculated
Distance between space station platform and ground base station
According to the relevant coordinate information, the angle information between the ground stations can be obtained:
further, using vector decomposition, the radial velocity between the space station and the ground base station
Can be expressed as:
further calculating to obtain the frequency due to the motion of the space station
Doppler shift of the carrier wave of
；
And a GNSS receiver carried on the space station platform is utilized to obtain an estimated value of the Doppler frequency shift through information calculation, and the estimated result is sent to a signal acquisition module. The receiver receives a frequency of
The carrier wave of (2) is down-converted to obtain an intermediate frequency signal with a frequency of
Then consider the actual received signal intermediate frequency after introducing the Doppler frequency shift to be
When the above result is directly used as the receiver for receiving signal acquisition,
to
And in the time interval, searching in the frequency domain. Using the frequency calculation result, the local carrier generated by local carrier NCO is mixed with the received signal to strip the carrier, and the received signal is receivedThe signal is a baseband signal obtained from the intermediate frequency, so that time domain code phase searching is further facilitated.
When searching for the code phase, the code doppler change caused by considering the carrier doppler frequency offset brought by the high dynamic scene also cannot be ignored, otherwise, the correlation result is seriously influenced. In the application, after the estimated value of carrier Doppler frequency offset is obtained by using the prior information of the GNSS receiver, the estimated value of code Doppler can be obtained by calculation by using the ratio of carrier frequency to code rate, and the rate of locally generated pseudo code is adjusted accordingly;
i.e. acquisition, the actual rate of the locally generated pseudo-code in real time should be 9.99977165 x 10 7 Hz to improve the correlation gain.
In order to improve the capturing speed, a parallel code phase searching method is adopted, and the code phase searching in the capturing range can be completed at one time through Fourier transform.
As shown in fig. 3, the time domain search of the received signal adopts a parallel mode, and after the digital intermediate frequency signal collected by the analog-to-digital converter is obtained, the digital intermediate frequency signal is respectively compared with the digital intermediate frequency signal
Branch and
on the branch having a frequency of
The local copy sine and the copy cosine carrier signals are multiplied and mixed, and then the obtained result is obtained
And
by a plurality of
Performing a fourier transform; and multiplying the transform result by the conjugate of the Fourier transform result of the local code sequence, finally carrying out Fourier inverse transform on the product to obtain the result of the received signal and the local signal in a time domain, and carrying out peak detection on the result to finish the search of the phase dimension of the received number.
It should be understood that, although the steps in the flowchart of fig. 1 are shown in order as indicated by the arrows, the steps are not necessarily performed in order as indicated by the arrows. The steps are not performed in the exact order shown and described, and may be performed in other orders, unless explicitly stated otherwise. Moreover, at least some of the steps in fig. 1 may include multiple sub-steps or multiple stages that are not necessarily performed at the same time, but may be performed at different times, and the order of performing the sub-steps or stages is not necessarily sequential, but may be performed alternately or alternately with other steps or at least some of the sub-steps or stages of other steps.
In one embodiment, as shown in fig. 5, there is provided an information-assisted high-dynamic weak spread spectrum signal fast acquisition apparatus, including: a radial velocity calculating module 502, a doppler shift calculating module 504, a signal frequency domain searching module 506, and a signal time domain searching module 508, wherein:
a radial velocity calculation module 502, configured to obtain position information and real-time velocity information of a space station according to a GNSS receiver mounted on the space station, and calculate the position information to obtain angle information between ground stations; calculating by utilizing the real-time speed information and the angle information between the ground stations to obtain the radial speed of the space station relative to the ground base station;
a doppler shift calculation module 504, configured to calculate according to the radial velocity and the carrier frequency of the spread spectrum signal, so as to obtain a doppler shift of the carrier;
a signal frequency domain searching module 506, configured to perform down-conversion on a carrier, and compensate the down-converted intermediate frequency signal according to the doppler frequency shift, so as to obtain an actual received signal intermediate frequency; the actual receiving signal intermediate frequency is used as a capturing search result of the receiving signal in a frequency domain;
a signal time domain searching module 508, configured to estimate code doppler according to the doppler frequency shift, the carrier frequency, and the pseudo code rate to obtain a local pseudo code rate; generating local pseudo codes by using the local pseudo code rate; the method comprises the steps of searching a receiving number phase in parallel, multiplying and mixing digital intermediate-frequency signals with local copy sine carrier signals and local copy cosine carrier signals on an I branch and a Q branch respectively after the digital intermediate-frequency signals collected by an analog-to-digital converter are obtained, and obtaining a mixing result; the frequency of the local copy sine carrier signal and the local copy cosine carrier signal is the actual intermediate frequency of the received signal; performing Fourier transform on the frequency mixing result in a complex form, multiplying the transform result by the conjugate of the Fourier transform result of the local pseudo code, and performing Fourier inverse transform on the product to obtain the acquisition search result of the received signal and the local signal in a time domain; and the acquisition search result of the received signal in the frequency domain and the acquisition search result of the received signal in the time domain are signal acquisition results.
In one embodiment, the radial velocity calculation module 502 is further configured to calculate the position information to obtain the angle information between the ground stations, including:
the position information is calculated to obtain the angle information between the ground stations as
Wherein the content of the first and second substances,
the location coordinates of the terrestrial base stations are represented,
representing spatial stations at time of day
The location information of (a) is stored in the storage unit,
indicating the time of day
Distance of space station and ground base station.
In one embodiment, the radial velocity calculating module 502 is further configured to calculate, by using the real-time velocity information and the angle information between the ground stations, a radial velocity of the space station relative to the ground base station, including:
calculating by utilizing the real-time speed information and the angle information between the ground stations to obtain the radial speed of the space station relative to the ground base station
Wherein, the first and the second end of the pipe are connected with each other,
representing spatial stations at time of day
Real-time speed information.
In one embodiment, the doppler shift calculation module 504 is configured to calculate, according to the radial velocity and the carrier frequency of the spread spectrum signal, a doppler shift of the carrier, and includes:
calculating according to the radial velocity and the carrier frequency of the spread spectrum signal to obtain the Doppler frequency shift of the carrier as
Wherein, in the step (A),
which represents the carrier frequency of the spread-spectrum signal,
indicating the speed of light.
In one embodiment, the signal frequency domain searching module 506 is configured to down-convert the carrier, and compensate the down-converted intermediate frequency signal according to the doppler shift to obtain the actual intermediate frequency of the received signal, and includes:
carrying out down-conversion on the carrier, compensating the intermediate frequency signal after down-conversion according to Doppler frequency shift, and obtaining the intermediate frequency of the actual received signal
Wherein, in the step (A),
representing the intermediate frequency signal.
In one embodiment, the signal time domain searching module 508 is further configured to estimate code doppler according to the doppler shift, the carrier frequency, and the pseudo code rate to obtain a local pseudo code rate, including:
estimating code Doppler according to Doppler frequency shift, carrier frequency and pseudo code rate to obtain code Doppler
Wherein, in the step (A),
representing a pseudo code rate of a ground station transmission;
and adding the code Doppler and the pseudo code rate to obtain the local pseudo code rate.
For a specific limitation of an information-assisted high-dynamic weak spread spectrum signal fast acquisition apparatus, reference may be made to the above limitation on an information-assisted high-dynamic weak spread spectrum signal fast acquisition method, which is not described herein again. The modules in the above-mentioned information-aided high-dynamic weak spread spectrum signal fast acquisition device can be wholly or partially implemented by software, hardware and their combination. The modules can be embedded in a hardware form or independent of a processor in the computer device, and can also be stored in a memory in the computer device in a software form, so that the processor can call and execute operations corresponding to the modules.
The technical features of the above embodiments can be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the above embodiments are not described, but should be considered as the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments only express several embodiments of the present application, and the description thereof is more specific and detailed, but not construed as limiting the scope of the invention. It should be noted that, for a person skilled in the art, several variations and modifications can be made without departing from the concept of the present application, and these are all within the scope of protection of the present application. Therefore, the protection scope of the present patent shall be subject to the appended claims.
Claims (9)
1. A method for fast acquisition of information-aided high-dynamic weak spread spectrum signals, the method comprising:
acquiring position information and real-time speed information of a space station according to a GNSS receiver carried on the space station, and calculating the position information to obtain angle information between ground stations;
calculating by utilizing the real-time speed information and the angle information between the ground stations to obtain the radial speed of the space station relative to the ground base station;
calculating according to the radial velocity and the carrier frequency of the spread spectrum signal to obtain the Doppler frequency shift of the carrier;
carrying out down-conversion on the carrier, and compensating the intermediate frequency signal after down-conversion according to the Doppler frequency shift to obtain the actual intermediate frequency of the received signal; the actual receiving signal intermediate frequency is used as a capturing search result of the receiving signal in a frequency domain;
estimating code Doppler according to the Doppler frequency shift, the carrier frequency and the pseudo code rate to obtain a local pseudo code rate; generating a local pseudo code by using the local pseudo code rate;
the method comprises the steps of searching a receiving number phase in parallel, multiplying and mixing digital intermediate-frequency signals with local copy sine carrier signals and local copy cosine carrier signals on an I branch and a Q branch respectively after the digital intermediate-frequency signals collected by an analog-to-digital converter are obtained, and obtaining a mixing result; the frequency of the local copy sine carrier signal and the local copy cosine carrier signal is the actual intermediate frequency of the received signal;
performing Fourier transform on the frequency mixing result in a complex form, multiplying a transform result by a conjugate of a Fourier transform result of the local pseudo code, and performing inverse Fourier transform on the product to obtain a capture search result of the received signal and the local signal in a time domain; and the acquisition search result of the received signal in the frequency domain and the acquisition search result of the received signal in the time domain are signal acquisition results.
2. The method of claim 1, further comprising:
and estimating Doppler information of the space station relative to the ground at the next moment by using position information and real-time speed information output by the GNSS receiver continuously and repeatedly at the current moment, and performing high-order compensation on Doppler frequency shift caused by the movement of the space station relative to the ground base station according to the obtained Doppler frequency shift prediction estimation value.
3. The method of claim 2, further comprising:
calculating the distance between the space station and the ground station according to the space station position coordinates output by the GNSS receiver, and determining signal transmission time delay by using the distance between the space station and the ground station; determining a time domain code phase capturing range according to the signal transmission delay;
determining a signal transmission delay of
Wherein the content of the first and second substances,
the position coordinates of the ground base station are represented,
representing spatial stations at time of day
The location information of (a) is stored in the storage unit,
indicating the time of day
The distance between the space station and the ground base station,
indicating the speed of light.
4. The method of claim 3, wherein calculating the position information to obtain angle information between ground stations comprises:
calculating the position information to obtain the angle information between the ground stations as
5. The method of claim 4, wherein calculating using the real-time velocity information and the angle information between the ground stations to obtain the radial velocity of the space station relative to the ground base station comprises:
calculating by using the real-time speed information and the angle information between the ground stations to obtain the radial speed of the space station relative to the ground base station
Wherein the content of the first and second substances,
representing spatial stations at time of day
Real-time speed information.
6. The method of claim 5, wherein calculating from the radial velocity and a carrier frequency of the spread spectrum signal to obtain a Doppler shift of the carrier comprises:
calculating according to the radial velocity and the carrier frequency of the spread spectrum signal to obtain the Doppler frequency shift of the carrier as
Wherein, in the process,
which represents the carrier frequency of the spread-spectrum signal,
indicating the speed of light.
7. The method of claim 6, wherein compensating the down-converted if signal according to the doppler shift to obtain an actual received signal if comprises:
compensating the intermediate frequency signal after down-conversion according to the Doppler frequency shift to obtain the intermediate frequency of the actual receiving signal
Wherein, in the step (A),
representing the intermediate frequency signal.
8. The method of claim 6, wherein estimating code doppler from the doppler shift, carrier frequency, and pseudo code rate to obtain local pseudo code rate comprises:
estimating code Doppler according to the Doppler frequency shift, the carrier frequency and the pseudo code rate to obtain code Doppler
Wherein, in the process,
representing a pseudo code rate of a ground station transmission;
and adding the code Doppler and the pseudo code rate to obtain a local pseudo code rate.
9. An information-assisted, high-dynamic, weak spread spectrum signal fast acquisition apparatus, comprising:
the system comprises a radial velocity calculation module, a data acquisition module and a data processing module, wherein the radial velocity calculation module is used for acquiring position information and real-time velocity information of a space station according to a GNSS receiver carried on the space station, and calculating the position information to obtain angle information between ground stations; calculating by utilizing the real-time speed information and the angle information between the ground stations to obtain the radial speed of the space station relative to the ground base station;
the Doppler frequency shift calculation module is used for calculating according to the radial velocity and the carrier frequency of the spread spectrum signal to obtain the Doppler frequency shift of the carrier;
the signal frequency domain searching module is used for carrying out down-conversion on the carrier wave, compensating the down-converted intermediate frequency signal according to the Doppler frequency shift, and obtaining the actual intermediate frequency of the received signal; the actual receiving signal intermediate frequency is used as a capturing search result of the receiving signal in a frequency domain;
the signal time domain searching module is used for estimating code Doppler according to the Doppler frequency shift, the carrier frequency and the pseudo code rate to obtain a local pseudo code rate; generating a local pseudo code by using the local pseudo code rate; the method comprises the steps that a receiving number phase is searched in parallel, after a digital intermediate frequency signal collected by an analog-to-digital converter is obtained, the digital intermediate frequency signal is multiplied and mixed with a local copy sine carrier signal and a local copy cosine carrier signal on an I branch and a Q branch respectively, and a mixing result is obtained; the frequency of the local copy sine carrier signal and the local copy cosine carrier signal is the actual intermediate frequency of the received signal; performing Fourier transform on the frequency mixing result in a complex form, multiplying a transform result by a conjugate of a Fourier transform result of the local pseudo code, and performing Fourier inverse transform on the product to obtain an acquisition search result of the received signal and the local signal in a time domain; and the acquisition search result of the received signal in the frequency domain and the acquisition search result of the received signal in the time domain are signal acquisition results.
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