CN114594500B - GNSS/LEO fusion positioning receiver system and positioning method - Google Patents

GNSS/LEO fusion positioning receiver system and positioning method Download PDF

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CN114594500B
CN114594500B CN202210124398.4A CN202210124398A CN114594500B CN 114594500 B CN114594500 B CN 114594500B CN 202210124398 A CN202210124398 A CN 202210124398A CN 114594500 B CN114594500 B CN 114594500B
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gnss
leo
module
processing module
frequency offset
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CN114594500A (en
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程莉
李莎
王怀兴
马云秀
马晓萌
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Hubei University of Education
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Hubei University of Education
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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
    • G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/13—Receivers
    • G01S19/33—Multimode operation in different systems which transmit time stamped messages, e.g. GPS/GLONASS
    • 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
    • G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/13—Receivers
    • G01S19/24—Acquisition or tracking or demodulation of signals transmitted by the system
    • G01S19/29—Acquisition or tracking or demodulation of signals transmitted by the system carrier including Doppler, related
    • 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
    • G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/13—Receivers
    • G01S19/24—Acquisition or tracking or demodulation of signals transmitted by the system
    • G01S19/30—Acquisition or tracking or demodulation of signals transmitted by the system code related
    • 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
    • G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/13—Receivers
    • G01S19/35—Constructional details or hardware or software details of the signal processing chain
    • G01S19/36—Constructional details or hardware or software details of the signal processing chain relating to the receiver frond end
    • 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
    • G01S19/01—Satellite radio beacon positioning systems transmitting time-stamped messages, e.g. GPS [Global Positioning System], GLONASS [Global Orbiting Navigation Satellite System] or GALILEO
    • G01S19/13—Receivers
    • G01S19/35—Constructional details or hardware or software details of the signal processing chain
    • G01S19/37—Hardware or software details of the signal processing chain
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02D—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN INFORMATION AND COMMUNICATION TECHNOLOGIES [ICT], I.E. INFORMATION AND COMMUNICATION TECHNOLOGIES AIMING AT THE REDUCTION OF THEIR OWN ENERGY USE
    • Y02D30/00—Reducing energy consumption in communication networks
    • Y02D30/70—Reducing energy consumption in communication networks in wireless communication networks

Abstract

The invention discloses a GNSS/LEO fusion positioning receiver system and a positioning method. The receiver system adopts the same crystal oscillator to provide clock signals for the LEO signal receiving radio frequency front end, the GNSS signal receiving radio frequency front end and the GNSS/LEO combined baseband processing module; the combined baseband processing module obtains GNSS/LEO ephemeris information through demodulating satellite signals, provides the ephemeris and observation value information to the GNSS/LEO combined PVT resolving module, utilizes a least square algorithm or a Kalman filtering algorithm to estimate the position and the speed of a receiver, and inputs the estimated GNSS pseudo-range/Doppler frequency offset and the LEO pseudo-range/Doppler frequency offset to the combined baseband processing module as feedback information, so that the capturing, tracking and positioning resolving performance of a fusion positioning receiver on satellite signals under weak GNSS signals can be further improved.

Description

GNSS/LEO fusion positioning receiver system and positioning method
Technical Field
The invention belongs to the field of global navigation satellite systems (Global Navigation Satellite System, GNSS), and particularly relates to a GNSS/LEO fusion positioning receiver system and a positioning method.
Background
Global satellite navigation systems (Global Navigation Satellite System, GNSS) refer to space-based radio navigation systems that provide all-day, all-weather three-dimensional positioning, speed measurement, and time service capabilities for users of earth-pointing and near-ground spaces. The chinese beidou satellite navigation system (BDS), the global satellite positioning system (GPS) in the united states, the russian GLONASS system (GLONASS) and the european Galileo satellite navigation system (Galileo) together constitute a global four-large satellite navigation system. GNSS plays a great role in civilian and military applications, and its application is limited only by the imagination of people.
In open space, the GNSS receiver can receive signals with higher power, and has good performance. However, since GNSS satellites are mostly medium earth orbit satellites, the orbit is about 2 tens of thousands of kilometers, the space loss of signals is large, the ground power is low, the signal-to-noise ratio is further reduced in the area where signals are blocked or interfered, and the positioning performance of the receiver is poor. In addition, many application scenes need to be positioned in real time, the transmission rate of navigation messages in the existing global satellite navigation system is low, and the speed and instantaneity of positioning navigation service are affected to a certain extent.
Assisted-GNSS (a-GNSS) can more quickly acquire and locate GNSS signals by externally assisting ephemeris information. The receiver inputs assistance information, typically including the visible satellite number, ephemeris, almanac and even precise time information, navigation data bit information, etc., from an external device prior to acquisition of the satellite signal. Assisted receivers are faster than unassisted receivers, but a-GNSS technology assisted by a ground reference site, cellular data network, has significant disadvantages in terms of service coverage, enhanced service is not available in areas where it is difficult to establish a ground enhanced site, and a-GNSS system applications are limited to blocking interference or network disruption.
On the other hand, the low orbit satellite orbit has lower height, generally about hundreds of kilometers to two thousands of kilometers, and has smaller space loss of transmitting signals, so that the LEO satellite can be used for navigation and positioning to widen service range and application scene. Secondly, the LEO satellite has very high speed relative to a ground receiver, has good Doppler observability, can be singly used for carrying out rough Doppler positioning, and can be used as a supplementary positioning system when GNSS cannot be used. Finally, low orbit satellites are commonly used for applications such as communication telemetry, and the information transmission speed is high, for example, iridium satellites are used, and the transmission speed is 50kbps and 1000 times of the transmission speed of GPS navigation messages. Based on these characteristics, LEO satellites are currently mainly used for positioning and aiding GNSS systems. As a stand-alone positioning system, LEO signals achieve positioning by signal-of-opportunity doppler frequencies. In addition, LEO satellites have the ability to transmit navigation signals. Now also low orbit satellites can transmit PRN signals like GNSS systems to improve the accuracy of positioning. Therefore, the advantages of the low-orbit satellite system and the GNSS system can be complemented, and the problem that the GNSS receiver is difficult to effectively solve the problems of capturing, tracking and positioning resolving of satellite signals under the condition of weak signals is solved.
Disclosure of Invention
GNSS receivers have low positioning performance in weak and complex signal environments, while A-GNSS technology is limited by the construction of ground-based augmentation sites on one hand, and on the other hand, the coverage of the technology is limited by the fight time or network disruption. Therefore, the invention provides a GNSS/LEO fusion positioning receiver system and a positioning method which are not limited to the two conditions and can effectively improve the capturing speed, tracking sensitivity and positioning performance of the GNSS receiver. The idea of the invention is as follows:
and the receiver comprises an LEO signal receiver radio frequency front end and a GNSS signal receiver radio frequency front end, and the two parts of radio frequencies share the same crystal oscillator. The shared crystal oscillator can ensure the time accuracy and stability of the GNSS/LEO combined baseband processing module, and is beneficial to the fusion positioning receiver to lock GNSS and low-orbit satellite signals in real time. The combined baseband processing module of the GNSS/LEO fusion positioning receiver can utilize the LEO baseband signal processing module to extract Doppler information and GNSS satellite ephemeris information emitted by LEO satellites to assist in capturing and tracking GNSS satellite signals. On the one hand, according to the Doppler auxiliary information, the frequency search interval and the code phase search interval of satellite signals can be greatly reduced, and the capturing efficiency is improved; on the other hand, the coherent integration time is prolonged in an auxiliary way through the navigation message carried by the low-orbit satellite, the bandwidth is effectively compressed, and the tracking performance sensitivity is improved. In addition, the position and speed information calculated by the GNSS/LEO combined PVT resolving module and the signal Doppler of the low-orbit satellite and each GNSS satellite are fed back to the GNSS/LEO combined baseband processing module, so that the positioning precision of the GNSS/LEO combined positioning receiver system can be further improved, and the capturing, tracking and positioning resolving performance of the combined positioning receiver to satellite signals under weak GNSS signals can be improved.
In order to solve the technical problems, the invention adopts the following technical scheme:
according to one aspect of the present invention, there is provided a GNSS/LEO fusion positioning receiver system comprising:
the system comprises an LEO signal receiving radio frequency front end, a GNSS signal receiving radio frequency front end, a crystal oscillator, a GNSS/LEO combined baseband processing module and a GNSS/LEO combined PVT resolving module;
the LEO signal receiving radio frequency front end, the GNSS signal receiving radio frequency front end and the GNSS/LEO combined baseband processing module share one crystal oscillator, the LEO signal receiving radio frequency front end and the GNSS signal receiving radio frequency front end are connected with the GNSS/LEO combined baseband processing module, and the GNSS/LEO combined baseband processing module is in bidirectional connection with the GNSS/LEO combined PVT resolving module.
Preferably, the GNSS/LEO joint baseband processing module includes: the system comprises an LEO baseband signal processing module, a GNSS capture module, a GNSS tracking module and a GNSS information demodulation module;
the LEO baseband signal processing module is respectively connected with the GNSS capture module and the GNSS tracking module, the GNSS capture module is connected with the GNSS tracking module, and the GNSS tracking module is connected with the GNSS information demodulation module;
the GNSS/LEO joint PVT resolving module comprises: the system comprises a PVT resolving module, an LEO speed projection module and a GNSS speed projection module;
the PVT resolving module is respectively connected with the LEO speed projection module and the GNSS speed projection module.
Preferably, the GNSS capturing module includes: a first mixer, a first correlator, a signal detector and a logic control circuit;
the logic control circuit is connected with the LEO baseband signal processing module, and is also respectively connected with the first mixer and the first correlator, and the first correlator is connected with the signal detector;
the GNSS tracking module comprises: the second mixer, the second correlator, the integral zero clearing module, the discriminator, the loop filter and the carrier NCO module;
the second mixer is connected with the signal detector, the second mixer is also connected with the second correlator, the second correlator is connected with the LEO baseband signal processing module, the second correlator is connected with the integral zero clearing module, the integral zero clearing module is connected with the discriminator, the discriminator is connected with the loop filter, the loop filter is connected with the carrier NCO module, and the carrier NCO module is connected with the second mixer.
Preferably, the LEO signal receiving radio frequency front end and the GNSS signal receiving radio frequency front end are respectively connected with corresponding antennas.
According to another aspect of the present invention, the present invention provides a positioning method of a GNSS/LEO fusion positioning receiver system, implemented based on the GNSS/LEO fusion positioning receiver system, including the steps of:
s1: the LEO signal receiving radio frequency front end receives LEO digital intermediate frequency signals through an antenna and sends the LEO digital intermediate frequency signals to the GNSS/LEO combined baseband processing module;
s2: the GNSS signal receiving radio frequency front end receives GNSS digital intermediate frequency signals through an antenna and sends the GNSS digital intermediate frequency signals to the GNSS/LEO combined baseband processing module;
s3: the GNSS/LEO combined baseband processing module inputs the receiver preliminary positioning result obtained by the resolution of the LEO baseband signal processing module into the GNSS capturing module, and estimates GNSS Doppler frequency offset and code phase information of captured satellites;
s4: the GNSS/LEO joint baseband processing module inputs Doppler frequency offset, code phase information and satellite PRN output by the GNSS capturing module to the GNSS tracking module, and tracks carrier waves and code phases of satellite signals;
s5: the GNSS/LEO joint baseband processing module performs bit synchronization and frame synchronization processing on satellite signals through the GNSS information demodulation module, acquires navigation messages, outputs GNSS/LEO ephemeris information, and sends the GNSS/LEO ephemeris and observation value information to the GNSS/LEO joint PVT resolving module;
s6: the GNSS/LEO joint PVT resolving module estimates the position and the speed of the GNSS/LEO fusion positioning receiver through a preset algorithm based on the GNSS/LEO ephemeris and the observation value information to obtain GNSS pseudo-range/Doppler frequency offset and LEO pseudo-range/Doppler frequency offset;
s7: and the GNSS/LEO joint PVT resolving module sends the estimated GNSS pseudo-range/Doppler frequency offset and the LEO pseudo-range/Doppler frequency offset to the GNSS/LEO joint baseband processing module as feedback information for assisting in capturing and tracking.
Preferably, S3 comprises the steps of:
a1: the LEO baseband signal processing module performs preliminary positioning on the ground receiver, determines the current visible GNSS satellite number PRN according to the demodulated GNSS ephemeris information and the preliminary positioning result, and calculates the GNSS preliminary satellite Doppler frequency offset and the preliminary pseudo range;
a2: and utilizing the GNSS initial Doppler frequency offset and the initial pseudo range to sequentially pass through a first mixer, a first correlator and a signal detector by the GNSS digital intermediate frequency signal, searching the Doppler frequency offset and the code phase by adopting a serial searching method, and estimating GNSS Doppler frequency offset and code phase information of the captured satellites.
Preferably, in step A2, the navigation message provided by the LEO satellite is used to eliminate the bit flip effect in the GNSS signal, and the logic control circuit is used to prolong the coherent integration time of the GNSS receiver, so as to improve the capturing speed and sensitivity of the receiver;
preferably, S4 comprises the steps of:
b1: the GNSS digital intermediate frequency signal captured by the GNSS capturing module is mixed with a local carrier wave through a second mixer, the mixing result is subjected to correlation operation with the pseudo code through a second correlator, and the signal after the pseudo code is stripped is subjected to integral zero clearing module to obtain a coherent integral value;
b2: after the signal is subjected to coherent integration, incoherent integration can be performed according to the requirement, and then the result is input into the discriminator;
b3: the carrier tracking error obtained by the discriminator is filtered by a loop filter, and is used as an input together with GNSS Doppler frequency offset output by the combined PVT resolving module as auxiliary information to accurately adjust carrier NCO, so that the local carrier frequency and the frequency of a received signal are kept consistent.
Preferably, in step B1, during the coherent integration operation, the coherent integration of the GNSS signal is assisted by using the GNSS navigation ephemeris obtained by the LEO baseband signal processing module, so as to prolong the time of the coherent integration.
Preferably, S6 and S7 comprise the steps of:
c1: the LEO ephemeris and observation values and the GNSS ephemeris and observation values are used as input values of a PVT resolving module, and the combined position and speed resolving is carried out by utilizing a least square or Kalman filtering method to respectively obtain LEO satellite position and speed information and GNSS satellite position and speed information;
c2: and inputting LEO satellite position and speed information obtained by the PVT resolving module into the LEO speed projection module to obtain LEO pseudo-range and Doppler frequency offset, and inputting GNSS satellite position and speed information obtained by the PVT resolving module into the GNSS speed projection module to obtain GNSS pseudo-range and Doppler frequency offset, wherein the LEO pseudo-range/Doppler frequency offset and the GNSS pseudo-range/Doppler frequency offset are used as the output of the GNSS/LEO combined PVT resolving module and fed back to the GNSS/LEO combined baseband processing module to assist in capturing and tracking satellite signals.
The technical scheme provided by the invention has the beneficial effects that:
(1) The capturing and tracking sensitivity and the positioning performance of the GNSS receiver under the weak signal conditions such as shielding or interference are effectively improved;
(2) The navigation message information transmitted by the low-orbit satellite is utilized to assist in prolonging the coherence time, so that the bandwidth can be effectively compressed, and the capturing and tracking sensitivity can be improved;
(3) The LEO signal receiving radio frequency front end and the GNSS signal receiving radio frequency front end share the same crystal oscillator, so that Doppler assistance on a GNSS tracking channel is more accurate;
(4) The coverage range of the positioning service can be improved under the condition that a ground base station cannot be erected by using the low-orbit satellite assisted GNSS receiver, and the low-orbit satellite assisted information does not need an additional synchronous system and information coding, so that engineering realization is facilitated.
(5) The GNSS/LEO fusion positioning receiver can use the LEO ephemeris and the observed value and the GNSS ephemeris and the observed value as the input of the combined positioning PVT resolving module together, so that the positioning precision of the receiver can be improved. In addition, the PVT resolving module feeds the LEO pseudo-range/Doppler frequency offset and the GNSS pseudo-range/Doppler frequency offset back to the forward GNSS/LEO combined baseband processing module respectively, so that the capturing and tracking performance of LEO and GNSS satellite signals can be further improved.
Drawings
The invention will be further described with reference to the accompanying drawings and examples, in which:
FIG. 1 is a block diagram of a GNSS/LEO fusion positioning receiver system in accordance with the present invention;
FIG. 2 is a block diagram of a GNSS/LEO fusion positioning acquisition assistance architecture of the present invention;
FIG. 3 is a GNSS/LEO fusion positioning tracking assistance architecture diagram of the present invention;
FIG. 4 is a block diagram of a GNSS/LEO joint PVT solution of the present invention.
Detailed Description
For a clearer understanding of technical features, objects and effects of the present invention, a detailed description of embodiments of the present invention will be made with reference to the accompanying drawings.
The NCO appearing hereinafter represents a digitally controlled oscillator and PRN represents the identification code of the satellite.
Referring to fig. 1, fig. 1 is a block diagram of a GNSS/LEO fusion positioning receiver system according to the present invention. The GNSS/LEO fusion positioning receiver system of the invention comprises: LEO signal receiving radio frequency front end, GNSS signal receiving radio frequency front end, crystal oscillator, GNSS/LEO joint baseband processing module and GNSS/LEO joint PVT resolving module. The LEO signal receiving radio frequency front end and the GNSS signal receiving radio frequency front end are both connected with a GNSS/LEO combined baseband processing module, and the GNSS/LEO combined baseband processing module is in bidirectional connection with a GNSS/LEO combined PVT resolving module. The same crystal oscillator module is adopted to provide clock signals for the LEO signal receiving radio frequency front end, the GNSS signal receiving radio frequency front end and the GNSS/LEO combined baseband processing module. The GNSS/LEO joint baseband processing module provides the LEO ephemeris and observation values and the GNSS ephemeris and observation values to the GNSS/LEO joint PVT resolving module, the GNSS/LEO joint PVT resolving module utilizes a least square algorithm or a Kalman filtering algorithm to estimate the position and the speed, and the module inputs the estimated LEO pseudo-range/Doppler frequency offset and the GNSS pseudo-range/Doppler frequency offset to the GNSS/LEO joint baseband processing module as feedback information, so that the capturing and tracking performance of signals can be improved.
In this embodiment, the GNSS/LEO joint baseband processing module includes: the system comprises an LEO baseband signal processing module, a GNSS capture module, a GNSS tracking module and a GNSS information demodulation module;
the LEO baseband signal processing module is respectively connected with the GNSS capture module and the GNSS tracking module, the GNSS capture module is connected with the GNSS tracking module, and the GNSS tracking module is connected with the GNSS information demodulation module.
Referring to FIG. 2, FIG. 2 is a block diagram illustrating the GNSS/LEO fusion positioning acquisition assistance of the present invention. The GNSS acquisition module comprises: a first mixer, a first correlator, a signal detector and a logic control circuit; the logic control circuit is connected with the LEO baseband signal processing module, and is also connected with the first mixer and the first correlator respectively, and the first correlator is connected with the signal detector.
The preliminary positioning information provided by the LEO baseband signal processing module may reduce the frequency search range and the code phase search range for satellite signals. The GNSS ephemeris information demodulated by the LEO baseband signal processing module can eliminate bit reversal influence in GNSS signals, prolong coherent integration time and improve the capturing sensitivity of a GNSS receiver.
The GNSS/LEO fusion positioning receiver signal capturing method provided by the invention specifically comprises the following steps:
(1) The LEO baseband signal processing module performs preliminary positioning on a ground receiver, determines a current visible GNSS satellite number PRN according to demodulated GNSS ephemeris information and a preliminary positioning result, and calculates a GNSS preliminary satellite Doppler frequency offset and a preliminary pseudo range;
(2) And utilizing the estimated preliminary GNSS Doppler frequency offset and pseudo range information to sequentially pass through a first mixer, a first correlator and a signal detector by GNSS digital intermediate frequency signals, searching Doppler frequency offset and code phase by adopting a serial search method, and estimating GNSS Doppler frequency offset and code phase information of the captured satellites.
Referring to FIG. 3, FIG. 3 is a block diagram illustrating the GNSS/LEO fusion positioning tracking assistance of the present invention. The GNSS tracking module comprises: the second mixer, the second correlator, the integral zero clearing module, the discriminator, the loop filter and the carrier NCO module;
the second mixer is connected with the signal detector, the second mixer is also connected with the second correlator, the second correlator is connected with the LEO baseband signal processing module, the second correlator is connected with the integral zero clearing module, the integral zero clearing module is connected with the discriminator, the discriminator is connected with the loop filter, the loop filter is connected with the carrier NCO module, and the carrier NCO module is connected with the second mixer.
And the LEO baseband signal processing module utilizes the satellite navigation ephemeris obtained by demodulation to assist the correlation integration of the GNSS tracking module, and prolongs the coherent integration time. The GNSS Doppler frequency offset obtained by combining the PVT resolving module assists a tracking loop, shortens the loop bandwidth, and improves the tracking sensitivity of the fusion positioning receiver to GNSS signals.
The signal tracking method of the GNSS/LEO fusion positioning receiver provided by the invention specifically comprises the following steps:
(1) The GNSS digital intermediate frequency signal captured by the GNSS capturing module is mixed with a local carrier wave through a second mixer, the mixing result is subjected to correlation operation with the pseudo code through a second correlator, and the signal after the pseudo code is stripped is subjected to integral zero clearing module to obtain a coherent integral value;
(2) After the signal is subjected to coherent integration, incoherent integration can be performed according to the requirement, and then the result is input into the discriminator;
(3) The carrier tracking error obtained by the discriminator is filtered by a loop filter, and is used as an input together with GNSS Doppler frequency offset output by the combined PVT resolving module as auxiliary information to accurately adjust carrier NCO, so that the local carrier frequency and the frequency of a received signal are kept consistent.
Referring to fig. 4, fig. 4 is a view showing a combined GNSS/LEO PVT calculation structure according to the present invention. The GNSS/LEO joint PVT resolving module comprises: the system comprises a PVT resolving module, an LEO speed projection module and a GNSS speed projection module; the PVT resolving module is respectively connected with the LEO speed projection module and the GNSS speed projection module.
The GNSS/LEO joint PVT resolving module can respectively calculate LEO pseudo-range/Doppler frequency offset and GNSS pseudo-range/Doppler frequency offset and feed the LEO pseudo-range/Doppler frequency offset back to the GNSS/LEO joint baseband processing module, so that capture and tracking performances of LEO and GNSS satellite signals are further improved. The method specifically comprises the following steps:
(1) The LEO ephemeris and observation value and the GNSS ephemeris and observation value are used as input values of a PVT resolving module, and the combined position and speed resolving is carried out by utilizing a least square or Kalman filtering method, so that LEO satellite position and speed information and GNSS satellite position and speed information can be obtained respectively;
(2) LEO satellite position and speed information obtained by the PVT resolving module are input to the LEO speed projection module to obtain LEO pseudo-range and Doppler frequency offset, and meanwhile GNSS satellite position and speed information obtained by the PVT resolving module are input to the GNSS speed projection module to obtain GNSS pseudo-range and Doppler frequency offset. The LEO pseudo-range/Doppler frequency offset and the GNSS pseudo-range/Doppler frequency offset can be used as the output of the GNSS/LEO joint PVT resolving module and fed back to the GNSS/LEO joint baseband processing module to assist in capturing and tracking satellite signals.
It should be noted that, in this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or system that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or system. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or system that comprises the element.
The foregoing embodiment numbers of the present invention are merely for the purpose of description, and do not represent the advantages or disadvantages of the embodiments. In the unit claims enumerating several means, several of these means may be embodied by one and the same item of hardware. The use of the terms first, second, third, etc. do not denote any order, but rather the terms first, second, third, etc. are used to interpret the terms as labels.
The foregoing description is only of the preferred embodiments of the present invention, and is not intended to limit the scope of the invention, but rather is intended to cover any equivalents of the structures or equivalent processes disclosed herein or in the alternative, which may be employed directly or indirectly in other related arts.

Claims (10)

1. A GNSS/LEO fusion positioning receiver system, comprising:
the system comprises an LEO signal receiving radio frequency front end, a GNSS signal receiving radio frequency front end, a crystal oscillator, a GNSS/LEO combined baseband processing module and a GNSS/LEO combined PVT resolving module;
the LEO signal receiving radio frequency front end, the GNSS signal receiving radio frequency front end and the GNSS/LEO combined baseband processing module share one crystal oscillator, the LEO signal receiving radio frequency front end and the GNSS signal receiving radio frequency front end are connected with the GNSS/LEO combined baseband processing module, and the GNSS/LEO combined baseband processing module is in bidirectional connection with the GNSS/LEO combined PVT resolving module;
the GNSS/LEO joint baseband processing module comprises: the system comprises an LEO baseband signal processing module, a GNSS capture module, a GNSS tracking module and a GNSS information demodulation module;
the LEO signal receiving radio frequency front end receives LEO digital intermediate frequency signals through an antenna and sends the LEO digital intermediate frequency signals to the GNSS/LEO combined baseband processing module;
the GNSS signal receiving radio frequency front end receives GNSS digital intermediate frequency signals through an antenna and sends the GNSS digital intermediate frequency signals to the GNSS/LEO combined baseband processing module;
the GNSS/LEO combined baseband processing module inputs the receiver preliminary positioning result obtained by the resolution of the LEO baseband signal processing module into the GNSS capturing module, and estimates GNSS Doppler frequency offset and code phase information of captured satellites;
the GNSS/LEO joint baseband processing module inputs Doppler frequency offset, code phase information and satellite PRN output by the GNSS capturing module to the GNSS tracking module, and tracks carrier waves and code phases of satellite signals;
the GNSS/LEO combined baseband processing module inputs the receiver preliminary positioning result obtained by the resolution of the LEO baseband signal processing module into the GNSS capturing module, and estimates GNSS Doppler frequency offset and code phase information of captured satellites;
the GNSS/LEO joint baseband processing module inputs Doppler frequency offset, code phase information and satellite PRN output by the GNSS capturing module to the GNSS tracking module, and tracks carrier waves and code phases of satellite signals;
the GNSS/LEO joint baseband processing module performs bit synchronization and frame synchronization processing on satellite signals through the GNSS information demodulation module, acquires navigation messages, outputs GNSS/LEO ephemeris information, and sends the GNSS/LEO ephemeris and observation value information to the GNSS/LEO joint PVT resolving module;
the GNSS/LEO joint PVT resolving module estimates the position and the speed of the GNSS/LEO fusion positioning receiver through a preset algorithm based on the GNSS/LEO ephemeris and the observation value information to obtain GNSS pseudo-range/Doppler frequency offset and LEO pseudo-range/Doppler frequency offset;
and the GNSS/LEO joint PVT resolving module sends the estimated GNSS pseudo-range/Doppler frequency offset and the LEO pseudo-range/Doppler frequency offset to the GNSS/LEO joint baseband processing module as feedback information for assisting in capturing and tracking.
2. A GNSS/LEO fusion positioning receiver system as claimed in claim 1,
the LEO baseband signal processing module is respectively connected with the GNSS capture module and the GNSS tracking module, the GNSS capture module is connected with the GNSS tracking module, and the GNSS tracking module is connected with the GNSS information demodulation module;
the GNSS/LEO joint PVT resolving module comprises: the system comprises a PVT resolving module, an LEO speed projection module and a GNSS speed projection module;
the PVT resolving module is respectively connected with the LEO speed projection module and the GNSS speed projection module.
3. The GNSS/LEO fusion positioning receiver system of claim 2, wherein the GNSS capture module comprises: a first mixer, a first correlator, a signal detector and a logic control circuit;
the logic control circuit is connected with the LEO baseband signal processing module, and is also respectively connected with the first mixer and the first correlator, and the first correlator is connected with the signal detector;
the GNSS tracking module comprises: the second mixer, the second correlator, the integral zero clearing module, the discriminator, the loop filter and the carrier NCO module;
the second mixer is connected with the signal detector, the second mixer is also connected with the second correlator, the second correlator is connected with the LEO baseband signal processing module, the second correlator is connected with the integral zero clearing module, the integral zero clearing module is connected with the discriminator, the discriminator is connected with the loop filter, the loop filter is connected with the carrier NCO module, and the carrier NCO module is connected with the second mixer.
4. The GNSS/LEO fusion positioning receiver system of claim 1, wherein the LEO signal receiving radio frequency front end and the GNSS signal receiving radio frequency front end are each coupled to a corresponding antenna.
5. Positioning method of a GNSS/LEO fusion positioning receiver system, implemented on the basis of a GNSS/LEO fusion positioning receiver system according to any of the claims 3-4, comprising the steps of:
s1: the LEO signal receiving radio frequency front end receives LEO digital intermediate frequency signals through an antenna and sends the LEO digital intermediate frequency signals to the GNSS/LEO combined baseband processing module;
s2: the GNSS signal receiving radio frequency front end receives GNSS digital intermediate frequency signals through an antenna and sends the GNSS digital intermediate frequency signals to the GNSS/LEO combined baseband processing module;
s3: the GNSS/LEO combined baseband processing module inputs the receiver preliminary positioning result obtained by the resolution of the LEO baseband signal processing module into the GNSS capturing module, and estimates GNSS Doppler frequency offset and code phase information of captured satellites;
s4: the GNSS/LEO joint baseband processing module inputs Doppler frequency offset, code phase information and satellite PRN output by the GNSS capturing module to the GNSS tracking module, and tracks carrier waves and code phases of satellite signals;
s5: the GNSS/LEO joint baseband processing module performs bit synchronization and frame synchronization processing on satellite signals through the GNSS information demodulation module, acquires navigation messages, outputs GNSS/LEO ephemeris information, and sends the GNSS/LEO ephemeris and observation value information to the GNSS/LEO joint PVT resolving module;
s6: the GNSS/LEO joint PVT resolving module estimates the position and the speed of the GNSS/LEO fusion positioning receiver through a preset algorithm based on the GNSS/LEO ephemeris and the observation value information to obtain GNSS pseudo-range/Doppler frequency offset and LEO pseudo-range/Doppler frequency offset;
s7: and the GNSS/LEO joint PVT resolving module sends the estimated GNSS pseudo-range/Doppler frequency offset and the LEO pseudo-range/Doppler frequency offset to the GNSS/LEO joint baseband processing module as feedback information for assisting in capturing and tracking.
6. The positioning method of a GNSS/LEO fusion positioning receiver system as claimed in claim 5, wherein S3 comprises the steps of:
a1: the LEO baseband signal processing module performs preliminary positioning on the ground receiver, determines the current visible GNSS satellite number PRN according to the demodulated GNSS ephemeris information and the preliminary positioning result, and calculates the GNSS preliminary satellite Doppler frequency offset and the preliminary pseudo range;
a2: and utilizing the GNSS initial Doppler frequency offset and the initial pseudo range to sequentially pass through a first mixer, a first correlator and a signal detector by the GNSS digital intermediate frequency signal, searching the Doppler frequency offset and the code phase by adopting a serial searching method, and estimating GNSS Doppler frequency offset and code phase information of the captured satellites.
7. The positioning method of a GNSS/LEO fusion positioning receiver system as claimed in claim 6, wherein in step A2, the navigation message provided by the LEO satellite is used to eliminate bit flip effect in GNSS signals, and the logic control circuit is used to prolong the coherent integration time of the GNSS receiver and improve the capturing speed and sensitivity of the receiver.
8. The positioning method of a GNSS/LEO fusion positioning receiver system as claimed in claim 5, wherein S4 comprises the steps of:
b1: the GNSS digital intermediate frequency signal captured by the GNSS capturing module is mixed with a local carrier wave through a second mixer, the mixing result is subjected to correlation operation with the pseudo code through a second correlator, and the signal after the pseudo code is stripped is subjected to integral zero clearing module to obtain a coherent integral value;
b2: after the signal is subjected to coherent integration, incoherent integration is performed according to the requirement, and then the result is input into a discriminator;
b3: the carrier tracking error obtained by the discriminator is filtered by a loop filter, and is used as an input together with GNSS Doppler frequency offset output by the combined PVT resolving module as auxiliary information to accurately adjust carrier NCO, so that the local carrier frequency and the frequency of a received signal are kept consistent.
9. The positioning method of a GNSS/LEO fusion positioning receiver system as claimed in claim 8, wherein in step B1, the coherent integration of the GNSS signals is assisted by using GNSS navigation ephemeris obtained by the LEO baseband signal processing module during the coherent integration operation, so as to prolong the time of the coherent integration.
10. The positioning method of a GNSS/LEO fusion positioning receiver system according to claim 5, wherein S6 and S7 include the steps of:
c1: the LEO ephemeris and observation values and the GNSS ephemeris and observation values are used as input values of a PVT resolving module, and the combined position and speed resolving is carried out by utilizing a least square or Kalman filtering method to respectively obtain LEO satellite position and speed information and GNSS satellite position and speed information;
c2: and inputting LEO satellite position and speed information obtained by the PVT resolving module into the LEO speed projection module to obtain LEO pseudo-range and Doppler frequency offset, and inputting GNSS satellite position and speed information obtained by the PVT resolving module into the GNSS speed projection module to obtain GNSS pseudo-range and Doppler frequency offset, wherein the LEO pseudo-range/Doppler frequency offset and the GNSS pseudo-range/Doppler frequency offset are used as the output of the GNSS/LEO combined PVT resolving module and fed back to the GNSS/LEO combined baseband processing module to assist in capturing and tracking satellite signals.
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