CN101630000B - System for estimating influence of interference signal on GPS performance - Google Patents
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Abstract
The invention discloses a system for estimating influence of interference signal on GPS performance based on a GPS software receiver. The system comprises a GPS antenna module and radio frequency module subsystem, an interference signal simulation subsystem, a GPS software receiver subsystem, and a GPS software receiver estimation subsystem, wherein the GPS antenna module and radio frequency module subsystem is used for converting the received GPS signal from the radio frequency to the intermediate frequency by down-frequency conversion, and outputting the digital intermediate frequency signal obtained by sampling to the GPS software receiver subsystem; the interference signal simulation subsystem is used for generating the digital interference signal, and outputting the generated digital interference signal to the GPS software receiver subsystem; the GPS software receiver subsystem is used for performing signal acquisition, signal tracking, bit synchronization and frame synchronization, pseudo range computation and computation of a satellite position and a user position on the inputted digital intermediate frequency signal and digital interference signal, and outputting the results to the GPS software receiver estimation subsystem; and the GPS software receiver estimation subsystem is used for performing error analysis on the received results to realize estimation of the influence of the interference signal on GPS performance. The system can determine which aspects in the interference signal are main factors of influencing the GPS performance.
Description
Technical field
The present invention relates to the satellite navigation technical field, relate in particular to a kind of based on the system of GPS software receiver assessment interference (artificial interference (jamming) or interference (interference)) signal to the GPS performance impact.
Background technology
GPS adopts direct sequence spread spectrum skill to have certain anti-interference capability, but the gps signal that arrives ground is very faint, to ground reception place gps signal power pact-160dBW, because when the receiver signal despreading is handled, processing gain just obtains after taking place in that pseudo-code is relevant, to such an extent as to receiver can be easy to be subjected to variously have a mind to, Radio frequency interference (RFI) unintentionally.Relevant influence can reduce the carrier noise density of all gps signals than (C/N0) to Radio frequency interference (RFI) to sign indicating number.If C/N0 drops to below the tracking thresholding of GPS receiver, just make GPS receiver losing lock, lose the ability that obtains measured value from gps signal.So the Anti-Jamming Technique of GPS receiver becomes the important component part of gps system interference protection measure.
Radio frequency interference (RFI) is divided into selective interference, broadband interference and ultra broadband and disturbs.The method that a lot of inhibition GPS undesired signals have been arranged at present, but a lot of methods are carried out on various GPS hardware receivers, be difficult to change the needs that all kinds of parameters of receiver are handled with adaptation signal when needing to increase hardware supported, the more important thing is the different of hardware and receiver architecture, be difficult to determine which aspect of undesired signal is the principal element that influences the GPS performance.
In recent years, software radio is used widely as a kind of new technology.The software wireless method for electrically has weakened the requirement to hardware greatly.Along with the fast development of computing machine, the calculated load that signal Processing causes weakens greatly, is easy to research and develop new interference removal method.The GPS software receiver only need be done less change just can express analysis, emulation, all kinds of algorithms of realization, particularly catch, follow the tracks of and locate what signal baseband was handled, be to realize fully by software, can accomplish under identical situation, to analyze and compare undesired signal, thereby which aspect that can determine undesired signal is the principal element that influences the GPS performance to the GPS Effect on Performance.
Summary of the invention
(1) technical matters that will solve
In view of this, it is a kind of based on the system of GPS software receiver assessment undesired signal to the GPS performance impact that fundamental purpose of the present invention is to provide, and is the principal element that influences the GPS performance with which aspect of determining undesired signal.
(2) technical scheme
For achieving the above object, the invention provides a kind ofly based on the system of GPS software receiver assessment undesired signal to the GPS performance impact, this system comprises:
Gps antenna module and radio-frequency module subsystem are used to receive the gps signal of gps satellite emission, with the gps signal that receives by radio frequency down-conversion to intermediate frequency, and behind over-sampling, obtain digital medium-frequency signal and export to GPS software receiver subsystem;
The Jamming Signal Simulation subsystem is used to produce the digital interference signal, and the digital interference signal that produces is exported to GPS software receiver subsystem;
GPS software receiver subsystem, be used for the digital medium-frequency signal and the digital interference signal of input are carried out signal capture, signal trace, bit synchronization and frame synchronization, its computation of pseudoranges, and satellite position and customer location calculating, and with signal capture, signal trace, its computation of pseudoranges, and satellite position and customer location result of calculation are exported to GPS software receiver evaluation subsystem;
GPS software receiver evaluation subsystem is used for signal capture, signal trace, its computation of pseudoranges to receiving, and satellite position and customer location result of calculation carries out error analysis, realizes the assessment of undesired signal to the GPS performance impact.
In the such scheme, described gps antenna module and radio-frequency module subsystem comprise gps antenna, radio-frequency front-end and digital collection card at least, gps antenna receives the gps signal of gps satellite emission, and the gps signal that receives amplified through low noise and bandpass filtering treatment after export to radio-frequency front-end; Gps signal is downconverted to Low Medium Frequency after entering radio-frequency front-end, and the output digital medium-frequency signal is to GPS software receiver subsystem after the sampling of digital collection card.
In the such scheme, described Jamming Signal Simulation subsystem is realized by the Matlab software in the computing machine, is used to generate the digital interference signal under the various situations, comprises at least: narrow-band digital undesired signal, wideband digital undesired signal and ultra-broadband digital undesired signal.
In the such scheme, described GPS software receiver subsystem carries out signal capture to the digital medium-frequency signal and the digital interference signal of input, be the first step that gps signal is handled, be used to obtain the roughly carrier frequency of satellite-signal and the code phase of C/A sign indicating number, for follow-up signal trace provides starting condition; And this signal capture be thick synchronously, be used for the signal that will receive and local signal phase differential narrow down to chip of pseudo-code or more among a small circle in.
In the such scheme, described GPS software receiver subsystem carries out signal trace to the digital medium-frequency signal and the digital interference signal of input, carries out after signal capture is finished, and is used to obtain navigation data; This signals tracking process will be caught the code phase of the roughly carrier frequency that obtains and C/A sign indicating number as starting condition, comprise two loops: follow the tracks of the sign indicating number loop of C/A sign indicating number and follow the tracks of the carrier loop of carrier frequency, the sign indicating number loop tracks adopts delay locked loop DLL, carrier loop is followed the tracks of and is adopted the Costas phaselocked loop, and these two loops are coupled; The correlation integral that tracking results is output as 1ms adds up; This signals tracking process is a fine synchronization, the phase change of local reference signal accurate tracking received signal.
In the such scheme, described GPS software receiver subsystem carries out bit synchronization and frame synchronization to the digital medium-frequency signal and the digital interference signal of input, is used for the result of signal trace is converted into navigation message; After the result of signal trace is converted into navigation message, carry out parity checking, this parity checking is divided into two verifications: first verification is that the 25th～30bit of each subframe is a parity check bit, satisfies parity arithmetic; Second verification is that the 29th～30bit is a parity code 00 in the 2nd character code HOW of each subframe; Behind bit synchronization, frame synchronization and checksum verification, in the 2nd character code HOW of each subframe, the 20th～22bit is the subframe sequence number; According to the form of subframe sequence number and navigation message, all satellite ephemeris, the satellite clock that navigation message comprises be can calculate and parameter and temporal information corrected, and the satellite position that calculates unit when any.
In the such scheme, described GPS software receiver subsystem is as follows to the digital medium-frequency signal and the digital interference signal process of carrying out its computation of pseudoranges of input: remove satellite star clock error, gps satellite sends identical subframe at synchronization, receiver is received identical subframe in the different moment, and same sub arrives the delay inequality of receiver antenna and represents the distance of satellite to receiver; Each subframe repetition time is 30s, and above-mentioned delay inequality is 19ms to the maximum, as long as delay inequality is in 19ms, can think that same sub is that synchronization at different satellites sends; Because in the software receiver image data is handled afterwards, there is not the local reference time, sample frequency information just becomes unique available temporal information, the interval of the sampled data points of the subframe starting point correspondence of each satellite can be arrived the delay inequality of antenna as satellite subframe starting point; The travel-time that gps satellite signal arrives ground receiver is generally 67～86ms, and a constant can artificially be set, and supposes that this constant is 68ms, and this constant is added the signal travel-time of delay inequality, and described pseudorange just equals this travel-time and multiply by the light velocity.
In the such scheme, described GPS software receiver subsystem is to the digital medium-frequency signal of input and the digital interference signal carries out satellite position and the customer location calculation process is as follows: utilize geocentric inertial coordinate system ECI to measure and determine the track of gps satellite, utilize the earth's core body-fixed coordinate system ECEF to calculate the position of GPS receiver; The numerical value of the satellite ephemeris in the navigation message is under the ECI, in order to calculate the position of GPS receiver, satellite ephemeris to be transformed to the ECEF coordinate system from ECI; And the time changes in ECEF, for the position of determining the user will provide a gps time t
cAccording to gps time t
cAnd satellite ephemeris, under the ECI coordinate system, try to achieve the position of satellite, utilize coordinate system transformation to try to achieve the position of satellite under the ECEF coordinate system then, try to achieve the position of receiver at last according to the location column system of equations of the pseudorange of receiver to four satellite and four satellites.
In the such scheme, described GPS software receiver evaluation subsystem comprises the assessment of following three partial contents at least: catch error analysis assessment, tracking error analysis and evaluation and the assessment of pseudorange analysis of Positioning Error.
In the such scheme, various narrow-band interference signals, wideband interferer signal and ultra broadband undesired signal that described GPS software receiver evaluation subsystem utilizes Matlab software to generate enter with the gps signal stack respectively carries out signal capture, signal trace and pseudorange positioning calculation process in the GPS software receiver, the situation of catching in this process, tracking situation and pseudorange are located situation and do not had the situation of catching, tracking situation and pseudorange location situation under the various disturbed conditions to compare analysis, obtain qualitative and quantitative result; For same type interference, also can under amplitude, frequency and the bandwidth situation of undesired signal, compare, obtain qualitative and quantitative results.
(3) beneficial effect
Provided by the invention this based on the system of GPS software receiver assessment undesired signal to the GPS performance impact, interface definition between each subsystem module is clear and definite, as long as satisfy interface requirement, the realization of inside modules just can have multiple implementation, also can not influence in the system other module.Can make like this under the situation of software design being changed seldom, just can test, and then can determine which aspect of undesired signal is the principal element that influences the GPS performance various dissimilar antenna structures, signal form, processing mode and analytical approach.
Description of drawings
Fig. 1 is provided by the invention based on the structural representation of GPS software receiver assessment undesired signal to the system of GPS performance impact;
Fig. 2 is provided by the invention based on the functional schematic of GPS software receiver assessment undesired signal to the system of GPS performance impact.
Embodiment
For making the purpose, technical solutions and advantages of the present invention clearer, below in conjunction with specific embodiment, and with reference to accompanying drawing, the present invention is described in more detail.
Provided by the invention this based on the system of GPS software receiver assessment undesired signal to the GPS performance impact, comprise gps antenna module and radio-frequency module subsystem, Jamming Signal Simulation subsystem, GPS software receiver subsystem and GPS software receiver evaluation subsystem.
Structurally, as shown in Figure 1, the present invention can be divided into input, handles and analyze three parts, wherein the importation comprises gps antenna module and radio-frequency module subsystem, and Jamming Signal Simulation subsystem, GPS software receiver subsystem belongs to the processing section, and analysis part is a GPS software receiver evaluation subsystem.Gps antenna module and radio-frequency module subsystem belong to hardware components, and Jamming Signal Simulation subsystem, GPS software receiver subsystem and GPS software receiver evaluation subsystem are based on the software section of PC.
Wherein, gps antenna module and radio-frequency module subsystem are used to receive the gps signal of gps satellite emission, with the gps signal that receives by radio frequency down-conversion to intermediate frequency, and behind over-sampling, obtain digital medium-frequency signal and export to GPS software receiver subsystem.The Jamming Signal Simulation subsystem is used to produce the digital interference signal, and the digital interference signal that produces is exported to GPS software receiver subsystem.GPS software receiver subsystem, be used for the digital medium-frequency signal and the digital interference signal of input are carried out signal capture, signal trace, bit synchronization and frame synchronization, its computation of pseudoranges, and satellite position and customer location calculating, and with signal capture, signal trace, its computation of pseudoranges, and satellite position and customer location result of calculation are exported to GPS software receiver evaluation subsystem.GPS software receiver evaluation subsystem is used for signal capture, signal trace, its computation of pseudoranges that receives, and satellite position and customer location result of calculation carries out error analysis, realizes the assessment of undesired signal to the GPS performance impact.
Described gps antenna module and radio-frequency module subsystem comprise gps antenna, radio-frequency front-end and digital collection card at least, gps antenna receives the gps signal of gps satellite emission, and the gps signal that receives amplified through low noise and bandpass filtering treatment after export to radio-frequency front-end; Gps signal is downconverted to Low Medium Frequency after entering radio-frequency front-end, and the output digital medium-frequency signal is to GPS software receiver subsystem after the sampling of digital collection card.
Described Jamming Signal Simulation subsystem is realized by the Matlab software in the computing machine, is used to generate the digital interference signal under the various situations, comprises at least: narrow-band digital undesired signal, wideband digital undesired signal and ultra-broadband digital undesired signal.
On function, as shown in Figure 2, the gps signal of launching from gps satellite is received by gps antenna, through radio-frequency front-end with its by radio frequency down-conversion to intermediate frequency, exist on the hard disk through the form with file behind the over-sampling.Utilize the Matlab software on the PC to produce digital interference signal miscellaneous simultaneously, also the form with file exists on the hard disk.Matlab software among the PC is handled the input of back as GPS software receiver subsystem with the signal and the signal in the digital interference file of digital intermediate frequency file.The GPS software receiver to input signal catch, tracking and its computation of pseudoranges, obtain positioning result at last.GPS software receiver evaluation subsystem to catch, the error of tracking and its computation of pseudoranges and positioning result analyzes.
Below to constituting provided by the invention thisly be described in detail respectively based on GPS software receiver assessment undesired signal each ingredient to GPS performance impact system.
1) Anneta module and radio-frequency module subsystem
Anneta module and radio-frequency module subsystem are based on hard-wired, and the kind of antenna is a lot, and the signal that receives is handled through low noise amplifier and bandpass filter, outputs to radio-frequency module.Signal is down-converted to Low Medium Frequency after entering radio-frequency module, output digital medium-frequency signal after the sampling of digital collection card, and data are stored in the hard disc of computer temporarily.
Only at the L1 wave band 1575.42MHz of GPS, the structure of tube antenna is not how in the present invention, and the centre frequency of antenna all will satisfy above-mentioned frequency.The effect of the down coversion in the radio-frequency module is exactly that the radiofrequency signal of 1575.42MHz is become the Low Medium Frequency signal, and the typical frequency of the signal of this Low Medium Frequency is 4.309MHz.The selection of capture card sampling rate needs only the intermediate frequency carrier according to radio-frequency module output, and satisfying is to lose this special law of sampling, and considers the design of simplifying frequency synthesizer simultaneously, should reduce sampling rate as far as possible, so that improve the reliability of system, reduce requirement to hardware, typical sample frequency is 12MHz.
2) Jamming Signal Simulation subsystem
Radio frequency interference (RFI) is divided into selective interference, broadband interference and ultra broadband and disturbs.Utilize Matlab software can generate digital interference signal under the various situations.
3) GPS software receiver subsystem
Widely used common receiver is based on special IC (Application SpecificIntegrated Circuit at present, ASIC) receiver of structure, and ASIC has limited dirigibility, the research staff is difficult to new algorithm is tested, analyzed and uses, and software receiver then is a kind of fine selection of receiver design.Software receiver is not the processing of carrying out signal capture and tracking in hardware but in software, with respect to common receiver, software receiver exploitation new algorithm does not need corresponding new hardware supported, so have that structure is general, a flexible function, advantage such as system improves and upgrading is convenient.
3.1 signal capture
Signal capture is the first step in gps signal is handled, and purpose is to obtain the roughly carrier frequency of satellite-signal and the code phase of C/A sign indicating number, for follow-up signal trace provides starting condition.Catch be thick synchronously, received signal and local signal phase differential can be narrowed down to chip of pseudo-code or more among a small circle in.
3.2 signal trace
In a single day signal captures with regard to entering signal and follows the tracks of link, and this link purpose is to obtain navigation data.Follow the tracks of processing from catching the roughly carrier frequency that obtains and the code phase of C/A sign indicating number as starting condition.Need two loops in order to follow the tracks of gps signal: follow the tracks of the sign indicating number loop of C/A sign indicating number and follow the tracks of the carrier loop of carrier frequency.Traditional sign indicating number loop tracks employing delay locked loop (Delay Lock Loop, DLL), the general normal classical Costas phaselocked loop that adopts of carrier track, these two loops are coupled.The correlation integral that tracking results is output as 1ms adds up.Tracking is a fine synchronization, allows the phase change of local reference signal accurate tracking received signal.
3.3 bit synchronization and frame synchronization
According to tracking results, just can recover navigation message through bit synchronization and frame synchronization.Next step is parity checking, and this parity checking is divided into two verifications, and first verification is that the 25th～30bit of each subframe is a parity check bit, satisfy parity arithmetic; Second verification is in the 2nd character code of each subframe (HOW), and bit29～30 are parity code (00).Behind bit synchronization, frame synchronization and checksum verification, in the 2nd character code of each subframe (HOW), bit20～22 are the subframe sequence number.According to the form of subframe sequence number and navigation message, just can calculate all satellite ephemeris, the satellite clock that navigation message comprises and correct parameter and temporal information etc., can calculate the satellite position of unit when any.
3.4 its computation of pseudoranges
Gps satellite sends identical subframe at synchronization (removing satellite star clock error), and receiver is received identical subframe in the different moment, and same sub arrives the delay inequality of receiver antenna and represents the distance of satellite to receiver.Each subframe repetition time is 30s, and above-mentioned delay inequality is 19ms to the maximum.In other words, as long as delay inequality is in 19ms, just can think that same sub is in the synchronization transmission of different satellites.Because in the software receiver image data is handled afterwards, there is not the local reference time, sample frequency information just becomes unique available temporal information, can arrive the interval of the sampled data points of the subframe starting point correspondence of each satellite as satellite subframe starting point the delay inequality of antenna.In addition, the travel-time that gps satellite signal arrives ground receiver is generally 67～86ms, constant hypothesis 68ms can artificially be set add the signal travel-time of delay inequality, and pseudorange just equals this travel-time and takes advantage of the light velocity.
3.5 satellite position and customer location calculate
Measure and the track of definite gps satellite, utilize geocentric inertial coordinate system (Earth-CenteredInteria, ECI); Calculate the position of GPS receiver, utilize the earth's core body-fixed coordinate system (Earth-Centered, Earth-Fixed, ECEF).The numerical value of the satellite ephemeris in the navigation message is under the ECI, in order to calculate the position of GPS receiver, satellite ephemeris must be transformed to the ECEF coordinate system from ECI.And the time changes in ECEF, so will provide a gps time t for the position of determining the user
cAccording to gps time t
cAnd satellite ephemeris, under the ECI coordinate system, try to achieve the position of satellite, utilize coordinate system transformation to try to achieve the position of satellite under the ECEF coordinate system then.Try to achieve at last the position of receiver according to the location column system of equations of the pseudorange of receiver to four satellite and four satellites.
4) GPS software receiver evaluation subsystem
GPS software receiver evaluation subsystem comprises the assessment of three partial contents: catch error analysis assessment, tracking error analysis and evaluation and the assessment of pseudorange analysis of Positioning Error.
Processes such as various narrow-band interference signals, wideband interferer signal and the ultra broadband undesired signal of utilizing Matlab software to generate enters in the GPS software receiver with the gps signal stack respectively and catch, tracking and pseudorange location Calculation, the situation of catching, tracking situation and the pseudorange of this process are located situation and do not had the situation of catching, tracking situation and pseudorange location situation under the various disturbed conditions to compare analysis, obtain qualitative and quantitative result.
For same type interference, can under the various situations such as amplitude, frequency and bandwidth of undesired signal, compare, thereby also can obtain qualitative and quantitative results.
Above-described specific embodiment; purpose of the present invention, technical scheme and beneficial effect are further described; institute is understood that; the above only is specific embodiments of the invention; be not limited to the present invention; within the spirit and principles in the present invention all, any modification of being made, be equal to replacement, improvement etc., all should be included within protection scope of the present invention.
Claims (10)
1. one kind based on the system of GPS software receiver assessment undesired signal to the GPS performance impact, it is characterized in that this system comprises:
Gps antenna module and radio-frequency module subsystem are used to receive the gps signal of gps satellite emission, with the gps signal that receives by radio frequency down-conversion to intermediate frequency, and behind over-sampling, obtain digital medium-frequency signal and export to GPS software receiver subsystem;
The Jamming Signal Simulation subsystem is used to produce the digital interference signal, and the digital interference signal that produces is exported to GPS software receiver subsystem;
GPS software receiver subsystem, be used for the digital medium-frequency signal and the digital interference signal of input are carried out signal capture, signal trace, bit synchronization and frame synchronization, its computation of pseudoranges, and satellite position and customer location calculating, and with signal capture, signal trace, its computation of pseudoranges, and satellite position and customer location result of calculation are exported to GPS software receiver evaluation subsystem;
GPS software receiver evaluation subsystem is used for signal capture, signal trace, its computation of pseudoranges to receiving, and satellite position and customer location result of calculation carries out error analysis, realizes the assessment of undesired signal to the GPS performance impact.
2. according to claim 1 based on the system of GPS software receiver assessment undesired signal to the GPS performance impact, it is characterized in that, described gps antenna module and radio-frequency module subsystem comprise gps antenna, radio-frequency front-end and digital collection card at least, gps antenna receives the gps signal of gps satellite emission, and the gps signal that receives amplified through low noise and bandpass filtering treatment after export to radio-frequency front-end; Gps signal is downconverted to Low Medium Frequency after entering radio-frequency front-end, and the output digital medium-frequency signal is to GPS software receiver subsystem after the sampling of digital collection card.
3. according to claim 1 based on the system of GPS software receiver assessment undesired signal to the GPS performance impact, it is characterized in that, described Jamming Signal Simulation subsystem is realized by the Matlab software in the computing machine, be used to generate the digital interference signal under the various situations, comprise at least: narrow-band digital undesired signal, wideband digital undesired signal and ultra-broadband digital undesired signal.
4. according to claim 1 based on the system of GPS software receiver assessment undesired signal to the GPS performance impact, it is characterized in that, described GPS software receiver subsystem carries out signal capture to the digital medium-frequency signal and the digital interference signal of input, it is the first step that gps signal is handled, be used to obtain the roughly carrier frequency of satellite-signal and the code phase of C/A sign indicating number, for follow-up signal trace provides starting condition; And this signal capture be thick synchronously, be used for the signal that will receive and local signal phase differential narrow down to chip of pseudo-code or more among a small circle in.
5. according to claim 1 based on the system of GPS software receiver assessment undesired signal to the GPS performance impact, it is characterized in that, described GPS software receiver subsystem carries out signal trace to the digital medium-frequency signal and the digital interference signal of input, after signal capture is finished, carry out, be used to obtain navigation data; This signals tracking process will be caught the code phase of the roughly carrier frequency that obtains and C/A sign indicating number as starting condition, comprise two loops: follow the tracks of the sign indicating number loop of C/A sign indicating number and follow the tracks of the carrier loop of carrier frequency, the sign indicating number loop tracks adopts delay locked loop DLL, carrier loop is followed the tracks of and is adopted the Costas phaselocked loop, and these two loops are coupled; The correlation integral that tracking results is output as 1ms adds up; This signals tracking process is a fine synchronization, the phase change of local reference signal accurate tracking received signal.
6. according to claim 1 based on the system of GPS software receiver assessment undesired signal to the GPS performance impact, it is characterized in that, described GPS software receiver subsystem carries out bit synchronization and frame synchronization to the digital medium-frequency signal and the digital interference signal of input, is used for the result of signal trace is converted into navigation message; After the result of signal trace is converted into navigation message, carry out parity checking, this parity checking is divided into two verifications: first verification is that the 25th～30bit of each subframe is a parity check bit, satisfies parity arithmetic; Second verification is that the 29th～30bit is a parity code 00 in the 2nd character code HOW of each subframe; Behind bit synchronization, frame synchronization and checksum verification, in the 2nd character code HOW of each subframe, the 20th～22bit is the subframe sequence number; According to the form of subframe sequence number and navigation message, all satellite ephemeris, the satellite clock that navigation message comprises be can calculate and parameter and temporal information corrected, and the satellite position that calculates unit when any.
7. according to claim 1 based on the system of GPS software receiver assessment undesired signal to the GPS performance impact, it is characterized in that described GPS software receiver subsystem is as follows to the digital medium-frequency signal and the digital interference signal process of carrying out its computation of pseudoranges of input:
Remove satellite star clock error, gps satellite sends identical subframe at synchronization, and receiver is received identical subframe in the different moment, and same sub arrives the delay inequality of receiver antenna and represents the distance of satellite to receiver; Each subframe repetition time is 30s, and above-mentioned delay inequality is 19ms to the maximum, as long as delay inequality is in 19ms, can think that same sub is that synchronization at different satellites sends; Because in the software receiver image data is handled afterwards, there is not the local reference time, sample frequency information just becomes unique available temporal information, the interval of the sampled data points of the subframe starting point correspondence of each satellite can be arrived the delay inequality of antenna as satellite subframe starting point; The travel-time that gps satellite signal arrives ground receiver is generally 67～86ms, and a constant can artificially be set, and this constant is added the signal travel-time of delay inequality, and described pseudorange just equals this travel-time and multiply by the light velocity.
8. according to claim 1 based on the system of GPS software receiver assessment undesired signal to the GPS performance impact, it is characterized in that, described GPS software receiver subsystem to the input digital medium-frequency signal and the digital interference signal carries out satellite position and the customer location calculation process is as follows:
Utilize geocentric inertial coordinate system ECI to measure and determine the track of gps satellite, utilize the earth's core body-fixed coordinate system ECEF to calculate the position of GPS receiver; The numerical value of the satellite ephemeris in the navigation message is under the ECI, in order to calculate the position of GPS receiver, satellite ephemeris to be transformed to the ECEF coordinate system from ECI; And the time changes in ECEF, for the position of determining the user will provide a gps time t
cAccording to gps time t
cAnd satellite ephemeris, under the ECI coordinate system, try to achieve the position of satellite, utilize coordinate system transformation to try to achieve the position of satellite under the ECEF coordinate system then, try to achieve the position of receiver at last according to the location column system of equations of the pseudorange of receiver to four satellite and four satellites.
9. according to claim 1 based on the system of GPS software receiver assessment undesired signal to the GPS performance impact, it is characterized in that described GPS software receiver evaluation subsystem comprises the assessment of following three partial contents at least: catch error analysis assessment, tracking error analysis and evaluation and the assessment of pseudorange analysis of Positioning Error.
10. according to claim 1 based on the system of GPS software receiver assessment undesired signal to the GPS performance impact, it is characterized in that, the various narrow-band interference signals that described GPS software receiver evaluation subsystem utilizes Matlab software to generate, wideband interferer signal and ultra broadband undesired signal enter with the gps signal stack respectively carries out signal capture in the GPS software receiver, signal trace and pseudorange positioning calculation process, with the situation of catching in this process, tracking situation and pseudorange location situation and the situation of catching that does not have under the various disturbed conditions, tracking situation and pseudorange location situation compare analysis, obtain qualitative and quantitative result; For same type interference, also can under amplitude, frequency and the bandwidth situation of undesired signal, compare, obtain qualitative and quantitative results.
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| CN107576975B (en) * | 2017-08-14 | 2019-07-30 | 北京航空航天大学 | The treating method and apparatus of the model of error evaluation applied to satellite navigation system |
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| CN110018441A (en) * | 2019-04-12 | 2019-07-16 | 相维(北京)科技有限公司 | A kind of appraisal procedure of TOA |
| CN111175697B (en) * | 2019-12-31 | 2023-09-19 | 中国电子科技集团公司第三十六研究所 | Unmanned aerial vehicle self-positioning precision evaluation method and device |
| CN111385046B (en) * | 2020-04-14 | 2024-10-01 | 北京航天广通科技有限公司 | Amplitude modulation broadcast interference assessment method and device |
| CN111766612A (en) * | 2020-07-09 | 2020-10-13 | 广东电网有限责任公司电力科学研究院 | Method, device and equipment for evaluating influence degree of electromagnetic interference on positioning result |
| CN113655503A (en) * | 2021-07-27 | 2021-11-16 | 西安广和通无线通信有限公司 | Method, device and system for testing positioning function and storage medium |
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