CN101865992B - Method for smoothing pseudo range by using Doppler frequency shift - Google Patents
Method for smoothing pseudo range by using Doppler frequency shift Download PDFInfo
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- CN101865992B CN101865992B CN200910097849A CN200910097849A CN101865992B CN 101865992 B CN101865992 B CN 101865992B CN 200910097849 A CN200910097849 A CN 200910097849A CN 200910097849 A CN200910097849 A CN 200910097849A CN 101865992 B CN101865992 B CN 101865992B
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Abstract
The invention discloses a method for smoothing the pseudo range by using a Doppler frequency shift, comprising the following steps: calculating the pseudo range of a measured epoch by using the code phase measurement value; calculating the change rate of the pseudo range of the measured epoch by using the Doppler frequency shift; calculating the estimation value of the pseudo range of the current epoch by using the smoothed value of the last epoch and the change rate of the pseudo range of the current measured epoch; and endowing the measurement value and the estimation value of the pseudo range of the current epoch with different weight to obtain the smoothed value of the pseudo range of the current epoch. Because the error on the pseudo range measured by using the code phase in single time is great, the Doppler frequency shift is used for smoothing the pseudo range. Therefore, the error on the pseudo range can be reduced effectively, and further the positioning accuracy of the GPS can be improved.
Description
Technical field
The invention belongs to GPS receiver location technology; Relate to the method that improves GPS receiver bearing accuracy; Relate in particular to a kind of method of utilizing the Doppler shift smoothing pseudo range, it is to utilize Doppler shift information that pseudorange is carried out smoothly to obtain the method for the less pseudorange of error.
Background technology
GPS (GPS) is a kind of navigational system of utilizing satellite constellation to carry out round-the-clock 24 hours location by U.S. Department of Defense's exploitation.The ultimate principle that the GPS receiver positions is exactly the signal that receives at least four satellites; Utilize the navigation message of satellites transmits to calculate satellite position; Utilize the ranging code (C/A sign indicating number and/or P sign indicating number) of satellites transmits to calculate the line-of-sight distance that comprise certain deviation of user to satellite; Term is referred to as pseudorange, calculates user's Position, Velocity and Time (PVT) information in conjunction with satellite position and pseudorange.
The bearing accuracy of GPS receiver depends on the combined action of multiple complicated factor.The error that deviation when complicated factor mainly comprises satellite clock and user clock with respect to gps system, ephemeris error, signal are introduced by ionosphere, tropospheric refraction in transmission course, error that multipath effect and receiver noise are introduced or the like.Usually for the ease of the influence of analyzing various error to precision, all bring the influence of various error sources in the pseudo range measurement to each satellite, the error of introducing various error sources is regarded as the equivalent error in the pseudo range measurement.
The GPS receiver can provide sign indicating number and measure two kinds of measured values with carrier phase measurement, can calculate through these two kinds of measurements that to measure moment user be pseudorange to the distance of satellite, and pseudorange is the distance that comprises the measured deviation value.In sign indicating number is measured; The GPS receiver is through the C/A sign indicating number of reproduction satellites transmits; And will reappear the sign indicating number align with the transmitter code that receives; By the moment that receives this signal of receiver record and the difference of the launch time that is recorded in this signal in transmitting be exactly the travel-time of signal from the satellite to user, the travel-time multiply by the light velocity in the vacuum, obtains required pseudorange value.In carrier phase measurement, receiver is measured is the carrier signal phase that produced by receiver and the instantaneous value (being the value of measurement epoch) by the difference of the carrier phase of satellites transmits that receives.The carrier phase of measuring (reproduction signal and the carrier phase difference that transmits) be a complete cycle of less than the carrier phase value; Satellite to the distance of receiver then be a complete cycle of unknown complete cycle issue and less than phase place and, there is the integer ambiguity problem in it.Phase place like receiver locking satellite signal also keeps its Continuous Tracking; The unknown complete cycle number of twice measurement is constant; If a certain moment of receiver to the satellite losing lock, even the losing lock time is very of short duration, all will occur week jumping phenomenon; Promptly unknown complete cycle is counted the generation conversion, has introduced the problem of integer ambiguity.
Obviously, through the pseudorange that sign indicating number is measured and carrier phase measurement obtains, all can receive the influence of various error sources and introduce measuring error.Wherein clock jitter, ephemeris error and atmospheric envelope refraction are the same to the influence of two kinds of measurements, but receiver noise and the multipath measuring error that influence is introduced to carrier phase measurement has only one of percentage of sign indicating number being measured the introducing measuring error.Be not difficult to find that can directly obtain pseudorange though sign indicating number is measured, measuring error is bigger.And the carrier phase measurement precision is higher, but has the integer ambiguity problem.A lot of scientific research personnel study resolving the complete cycle number, though proposed a lot of methods, it still is cumbersome obtaining the complete cycle number in real time.How to solve above-mentioned sign indicating number and measure and the carrier phase measurement problem, obtain the higher pseudorange value of precision, just become the important topic that improves GPS receiver bearing accuracy with fairly simple method.
Prior art proposes the method with carrier phase smoothing code pseudorange, promptly uses the pseudorange variable quantity between twice measurement of phase difference calculating of twice measurement, removes the level and smooth yard pseudorange of measuring with this pseudorange variable quantity again.This method can be avoided the integer ambiguity problem in the carrier phase measurement when receiver keeps Continuous Tracking to satellite; Because when receiver keeps Continuous Tracking to satellite; This unknown complete cycle number is constant, can disappear through the difference to twice measurement.But in case losing lock midway will cause week to jump phenomenon, make that the unknown complete cycle number that is comprised in the phase place of twice measurement is different, and can't be through difference this unknown complete cycle number that disappears.In the reception environment of " urban canyons ", the phenomenon that gps signal is blocked is very common, occur jumping in week phenomenon ceaselessly losing lock, recapture, wave filter is initialization ceaselessly, thereby the application of this method is restricted.
Doppler shift is because satellite, has comprised satellite and user's velocity information with respect to the caused by relative motion of receiver user in the Doppler shift value, thereby provides possible for utilizing Doppler shift to calculate satellite to user's pseudorange information.And the measuring accuracy of Doppler shift is higher, and does not receive the influence of integer ambiguity problem.Prior art ISSN:1009-427X (2003) 02-0079-04 utilizes the observed quantity of GPS Doppler shift can obtain the high-accuracy speed measurement result, provides gps carrier phase observations equation in the literary composition.
Summary of the invention
The measuring error that the objective of the invention is in order to solve prior art pseudo range measurement method is bigger; The problem that has integer ambiguity and require Continuous Tracking; A kind of method of utilizing the Doppler shift smoothing pseudo range is provided, neither receives the influence of integer ambiguity, high measurement accuracy is arranged again; And can obtain the higher pseudorange of precision with this method neatly, thereby realize improving bearing accuracy.
The inventive method integrated use code phase measuring and Doppler shift information utilize code phase measuring directly to obtain pseudorange, and with Doppler shift information pseudorange are carried out smoothly, thereby reduce the error of pseudorange, improve locating accuracy.
Above-mentioned purpose technical scheme of the present invention realizes through following method: based on the gps satellite location receiving system that is made up of antenna, radio frequency processing module, baseband signal processing module, navigation processing module and PVT message output module, it utilizes the method for Doppler shift smoothing pseudo range to comprise the steps:
Step 1: based on receiving by antenna, and the measurement pseudorange ρ (n) of code phase measuring value calculating n epoch that after radio frequency processing module and baseband signal processing module are handled, obtains;
Step 2:, utilize Doppler shift to calculate the pseudorange variation delta ρ (n) of epoch (n-1) to n epoch in the navigation processing module;
Step 3:, the measurement pseudorange ρ (n) that obtains in the step 1 is obtained the pseudorange ρ behind n epoch level and smooth as smoothing processing with the pseudorange variation delta ρ (n) that obtains in the step 2 in the navigation processing module
Smooth(n).
Step 4:, utilize the pseudorange ρ behind obtain in the step 3 level and smooth in the navigation processing module
Smooth(n) resolve user PVT information, and through the output of PVT message output module.
Further, in above-mentioned steps 2, calculate epoch (n-1) algorithm of pseudorange variable quantity to n epoch with Doppler shift, its computing formula is:
In the formula, the pseudorange variable quantity between twice measurement epoch of Δ ρ (n) expression;
f
d(n) expression Doppler shift;
C representes the light velocity in the vacuum;
f
LExpression the nominal carrier frequency of the L-band signal that received;
T representes the time interval of twice measurement.
Said epoch n Doppler shift value f
d(n) be f through the Doppler shift value of revising
D' (n); It is by Doppler shift f
d(n) utilize the local clock frequency deviation that it is done to revise and obtain, be used for the accurately pseudorange variable quantity between twice measurement epoch of calculating:
Further, in the said step 103 the measurement pseudorange being made smoothing processing also comprises the steps:
Step 401:, then measure the initial value of pseudorange as smoothing pseudo range, i.e. ρ with this if obtain measuring for the first time pseudorange
Smooth(1)=ρ (1); If not obtain measuring pseudorange for the first time, then execution in step 402;
Step 402: with the smoothing pseudo range ρ of epoch (n-1)
Smooth(n-1) and the epoch that epoch, n obtained (n-1) to epoch n the pseudorange of pseudorange variance estimation n epoch;
Step 403: respectively to epoch n the measurement pseudorange with estimate that pseudorange gives certain weight, addition obtains the smoothing pseudo range ρ of n epoch
Smooth(n).
Weight in the said step 403 is provided with definite when initialization, and giving the weight of measuring pseudorange is 1 with giving the weight sum of estimating pseudorange.
During initialization, give and measure pseudorange weight limit value 1, give and estimate pseudorange minimal weight value 0;
Along with going deep into of smoothing processing, with the weighted value of measuring pseudorange by be used for the form that level and smooth epoch, quantity was inversely proportional to and reduce the corresponding weight of estimating pseudorange that also just increased gradually.
Substantial effect of the present invention:
1, there is not the challenge that resolves integer ambiguity in the carrier phase measurement.
2, solving sign indicating number measures and directly obtains pseudorange and have the bigger problem of measuring error.
3, gps signal runs into the common phenomenon of blocking in the reception environment of " urban canyons ", and the assurance application is not restricted to pseudorange is level and smooth after following the tracks of this satellite again, still to continue to use this method.
4, can obtain the higher pseudorange of precision with this method neatly, thereby realize improving bearing accuracy.
Description of drawings
Fig. 1 is that the GPS receiver constitutes the module schematic block diagram.
Among Fig. 1: 1-GPS receiver, the antenna of 11-GPS receiver, 12-radio frequency processing module, 14-baseband signal processing module, 15-navigation processing module, 16-PVT signal output module, 131～13n-GPS Navsat.
Fig. 2 is that the present invention is according to measured value smoothing pseudo range processing flow chart.
Fig. 3 is the process flow diagram that the present invention is based on Doppler shift compute pseudo-ranges rate of change.
Fig. 4 is the process flow diagram that the present invention calculates pseudo-level and smooth distance.
Embodiment
Below in conjunction with accompanying drawing and practical implementation instance the method for the invention and enforcement thereof are done further to specify.Through following detailed argumentation, those of ordinary skill in the art can deepen the understanding to the object of the invention, characteristics and advantage.
Fig. 1 shows the GPS receiver and forms module frame chart.GPS receiver 1 is by antenna 11, radio frequency processing module 12, and baseband signal processing module 14, navigation processing module 15 is formed with PVT message output module 16.The signal that antenna 11 receives from satellite 131,132,133～13n, the radiofrequency signal of 12 pairs of receptions of radio frequency processing module is handled the digital medium-frequency signal that obtains being fit to Base-Band Processing, and sends into baseband signal processing module 14.Baseband signal processing module 14 is further handled digital medium-frequency signal, to the sign indicating number measured value, obtains measured value to local carrier signal from carrier tracking loop from the code tracking loop rood.The measured value that obtains at baseband signal processing module 14 is sent into navigation processing module 15 and is carried out navigation processing, comprises compute pseudo-ranges, pseudorange is carried out smoothly, with the pseudorange location after level and smooth.At last, send into PVT message output module 16, export with specific format by the PVT information that navigation processing module 15 obtains.
Fig. 2 is that the embodiment of the invention is according to code phase measuring value compute pseudo-ranges and utilize Doppler shift that pseudorange is carried out level and smooth flow process.Present embodiment is described emphasis according to sign indicating number measured value compute pseudo-ranges and is utilized Doppler shift that pseudorange is carried out level and smooth process.
At first, extract the measured value of sign indicating number measured value and local carrier signal from baseband signal processing module 14 in step 201; Connect down step 202, the sign indicating number measured value that extracts and the measured value of local carrier signal are delivered in the navigation processing module 15, navigation processing module 1 is utilized sign indicating number measured value compute pseudo-ranges; In step 203, navigation processing module 15 is also utilized the carrier wave measured value to calculate Doppler shift and is converted the pseudorange rate of change into; Then, in step 204, the pseudorange that navigation processing module 15 utilizes the 203 pseudorange rate of change that obtain that step 202 is obtained carries out smoothing pseudo range to be handled, and obtains the pseudorange after level and smooth.
The concrete computation process of each step among following further explain Fig. 2.In the step 202, pseudorange is to obtain with the light velocity that the travel-time of signal multiply by in the vacuum, and signal propagation time is to obtain with the difference that is recorded in the x time in the signal time of reception through the signal that calculates the receiver measurement.Signal reception time can obtain through local clock, then from the navigation message that receives, reads and utilize the launch time of signal a yard measured value to calculate.
Satellite time provides high 17 of second word of each subframe of navigation message, and note is made TOW, and TOW is unit with 6s, representes the launch time of the 1bit of next subframe.But in order to calculate current measurement epoch pairing launch time, TOW is only arranged not enough, also need calculate from current subframe reference position to time that measurement epoch has disappeared.The calculating of this time will be used a yard measured value: epoch counting (comprise 20ms epoch with 1ms epoch), code phase, yard NCO phase place.Be total launch time:
Ts=TOW*6+20ms counts * 20/1000+1ms epoch and counts/1000++ code phase/(1023000)+sign indicating number NCO phase place/(sign indicating number NCO maximum cycle)/(1023000) epoch
Calculate the launch time of measurement epoch correspondence, just can confirm the pseudorange of measurement epoch receiver user to respective satellite thereupon.
Fig. 3 is the process flow diagram that the present invention is based on Doppler shift compute pseudo-ranges rate of change, has provided the calculation process of pseudorange rate of change.Owing to have relative motion between satellite and the receiver user, make signal frequency that receiver receives Doppler shift take place with respect to the signal frequency of satellites transmits.Suppose to represent the signal frequency of receiver actual reception, with f with f
IFThe signal frequency of expression satellites transmits, then Doppler shift is:
f
D＝f-f
IF
And in case satellite is gone up in tracking, the carrier tracking loop of baseband signal processing module will lock the frequency and the phase place of carrier signal, and keep its tracking.Therefore at first in step 301, from carrier tracking loop, extract measured value, and, calculate the Doppler shift of measuring in step 302.
If current epoch, the receiver clock frequency deviation was df, the nominal frequency of satellites transmits carrier wave is f
L(L1 is 1575.42MHz, and L2 is 1227.6MHz), then in step 303, calculate revised Doppler shift and be:
f
D′＝f
D-df*f
L
If satellite and the user relative velocity on direction of visual lines is v, pseudorange rate of change just, the light velocity in the vacuum is c, then Doppler shift is:
In time t, the variable in distance between satellite and the user is:
Δs＝v*t
Therefore, in step 304,, calculate twice pseudorange variable quantity between measurement epoch and be according to the revised Doppler shift value of local clock frequency deviation:
Fig. 4 has provided and has utilized twice pseudorange variable quantity between the measurement epoch that pseudorange is carried out level and smooth flow process, and embodiment has adopted the Hatch wave filter: pseudorange value ρ then
Smooth(n) calculate according to following formula:
ρ
smooth(n)＝mρ(n)+(1-m)(ρ
smooth(n-1)+Δρ(n))
In the formula: the n measurement epoch; M is the filter parameter value.
In the treatment scheme of Fig. 4, at first to confirm that filter parameter is the m value in step 401.The size of m has determined pseudorange that is calculated by the sign indicating number measured value and the pseudorange rate of change shared proportion in pseudorange is level and smooth that is obtained by the Doppler measurement value.Because it is bigger that sign indicating number is measured the error ratio of introducing in the pseudorange; And the measurement of Doppler shift is not vulnerable to the influence of various error sources, and present embodiment is done the initialization setting when beginning, and m is made as 1 with filter parameter; Later on along with the increase that is used for level and smooth measurement epoch n; Form according to being inversely proportional to n reduces the m value gradually, to reduce the weights of yard pseudorange, has also increased the weights of the estimation pseudorange that is obtained by Doppler shift simultaneously gradually.
After confirming filter parameter, in step 402, do initial value with the sign indicating number pseudorange that epoch, the n=1 value measured, promptly
ρ
smooth(1)＝ρ(1)
Then, in step 403, utilize each sign indicating number pseudorange and pseudorange rate of change of measuring that pseudorange is carried out smoothing processing, calculate smoothing pseudo range.Even cause of short duration losing lock owing to reason such as blocking midway, more still can be during this satellite on the secondary tracking according to the pseudorange converted quantity during pseudorange rate of change and the losing lock Time Calculation losing lock, thus continue pseudorange is done smoothing processing.
The present invention combines sign indicating number and measures and Doppler shift advantage separately, utilizes Doppler shift that sign indicating number is measured pseudorange and carries out smoothly having reduced the error of pseudorange, thereby having improved locating accuracy.
More than specified the course of work of the present invention, but this instantiation just lifting for the ease of understanding, should not be regarded as is limitation of the present invention.The common appointees of technical field all can make various possible equal change or replacements according to the description of the technical scheme of the present invention and the example under any, but all these changes or replacement all should belong to the protection domain of claim of the present invention.
Claims (4)
1. utilize the method for Doppler shift smoothing pseudo range; It is characterized in that; Based on the gps satellite location receiving system that is made up of antenna, radio frequency processing module, baseband signal processing module, navigation processing module and PVT message output module, it utilizes the method for Doppler shift smoothing pseudo range to comprise the steps:
Step 101: based on receiving by antenna, and the measurement pseudorange ρ (n) of code phase measuring value calculating n epoch that after radio frequency processing module and baseband signal processing module are handled, obtains;
Step 102:, utilize Doppler shift to calculate the pseudorange variation delta ρ (n) of epoch (n-1) to n epoch in the navigation processing module;
Step 103:, adopt the Hatch wave filter to obtain the pseudorange ρ behind n epoch level and smooth to the measurement pseudorange ρ (n) that obtains in the step 101 as smoothing processing with the pseudorange variation delta ρ (n) that obtains in the step 102 in the navigation processing module
Smooth(n):
ρ
smooth(n)＝mρ(n)+(1-m)(ρ
smooth(n-1)+Δρ(n))；
In the formula: n is a measurement epoch; M is the filter parameter value;
The measurement pseudorange is made smoothing processing also to be comprised the steps:
Step (1): confirm that filter parameter is the m value; If obtain measuring for the first time pseudorange value, then measure the initial value of pseudorange value as smoothing pseudo range, i.e. ρ with this
Smooth(1)=ρ (1); If not obtain measuring for the first time pseudorange, then execution in step (2);
Step (2): with the smoothing pseudo range ρ of epoch (n-1)
Smooth(n-1) and the epoch that epoch, n obtained (n-1) to epoch n the pseudorange of pseudorange variance estimation n epoch;
Step (3): utilize each measurement pseudorange and pseudorange variable quantity of measuring that pseudorange is carried out smoothing processing, calculate smoothing pseudo range, respectively to epoch n the measurement pseudorange give certain weight with the estimation pseudorange, addition obtains the smoothing pseudo range ρ of n epoch
Smooth(n);
Step 104:, utilize the pseudorange ρ behind obtain in the step 103 level and smooth in the navigation processing module
Smooth(n) resolve user PVT information, and through the output of PVT message output module.
2. method according to claim 1, its characteristic are that also in above-mentioned steps 102, with the algorithm of Doppler shift compute pseudo-ranges variable quantity, its computing formula is:
In the formula, Δ ρ (n) expression epoch (n-1) is to the pseudorange variable quantity of n epoch;
f
d(n) Doppler shift of expression n epoch;
C representes the light velocity in the vacuum;
f
LThe nominal carrier frequency of the L-band signal that expression is received;
T representes the time interval of twice measurement epoch.
3. method according to claim 2, its characteristic also be, said epoch n Doppler shift f
d(n) be f through the Doppler shift of revising
D' (n); It is by Doppler shift f
d(n) utilize the local clock frequency deviation that it is done to revise and obtain, be used for the accurately pseudorange variable quantity between twice measurement epoch of calculating:
4. method according to claim 1 is characterized in that, the weight in the said step (3) is provided with definite when initialization, and giving the weight of measuring pseudorange is 1 with giving the weight sum of estimating pseudorange;
During initialization, give and measure pseudorange weight limit value 1, give and estimate pseudorange minimal weight value 0; Later on along with the increase that is used for level and smooth measurement epoch n, reduce m value gradually according to the form that is inversely proportional to n, to reduce to measure the weights of pseudorange, the while also increases the weights of the estimation pseudorange that is obtained by Doppler shift gradually; Along with going deep into of smoothing processing, with the weighted value of measuring pseudorange by be used for the form that level and smooth epoch, quantity was inversely proportional to and reduce the corresponding weight of estimating pseudorange that also just increased gradually.
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| CN102426372A (en) * | 2011-10-31 | 2012-04-25 | 北京中微星通电子有限公司 | Carrier smoothing pseudo range method and device |
| CN103293537B (en) * | 2012-03-05 | 2016-01-06 | 安凯(广州)微电子技术有限公司 | A kind of GPS digital tracking method and GPS figure tracking ring efficiently |
| US10267920B2 (en) * | 2012-06-27 | 2019-04-23 | Mitsubishi Electric Corporation | Positioning method |
| CN104133231B (en) * | 2014-07-29 | 2016-09-21 | 南京理工大学 | A kind of navigation locating method based on integrated Doppler smoothing pseudo range |
| CN107193026A (en) * | 2017-05-06 | 2017-09-22 | 千寻位置网络有限公司 | Pseudorange positioning smooth method and system, positioning terminal |
| CN114442474A (en) * | 2022-02-09 | 2022-05-06 | 北京中科智易科技有限公司 | Off-line data acquisition equipment time synchronization method based on Beidou time service |
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