CN105044744A - Non-cooperative navigation satellite identification method based on Doppler frequency shift characteristic - Google Patents
Non-cooperative navigation satellite identification method based on Doppler frequency shift characteristic Download PDFInfo
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- CN105044744A CN105044744A CN201510368579.1A CN201510368579A CN105044744A CN 105044744 A CN105044744 A CN 105044744A CN 201510368579 A CN201510368579 A CN 201510368579A CN 105044744 A CN105044744 A CN 105044744A
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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
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- G01S19/35—Constructional details or hardware or software details of the signal processing chain
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Abstract
The present invention discloses a non-cooperative navigation satellite identification method based on a Doppler frequency shift characteristic, and belongs to the non-cooperative spacecraft orbit determination technology field. The method of the present invention comprises the steps of obtaining the single carrier signals of different frequencies and the Doppler frequency shift measurement values by the codeless carrier recovery; calculating the Doppler frequency shift prior values according to the initial orbit parameters of a low-orbit user satellite and the navigation star ephemerides marked on a cycle; arranging the Doppler frequency shift measurement values containing the receiver frequency difference and the prior values into two sets of samples according to a descending order, and using a dichotomy to find a frequency difference estimated value efficiently to realize the two sets of consistent and corresponding frequencies; according to the proportion of the Doppler frequency shift matching residuals, adopting a global matching and local rejecting method to improve the global credibility of the satellite identification. The method provided by the present invention can identify a navigation satellite, and also can obtain the more accurate receiver frequency difference estimated value.
Description
Technical field
The present invention relates to a kind of non-cooperation Navsat based on Doppler shift feature and know method for distinguishing, belong to non-cooperative Spacecraft orbit determination technical field.
Background technology
In common satellite navigation, be the correlation properties utilizing pseudo-random code good, the mode of being mated by pseudo-code carrys out navigation by recognition satellite.But when satellite navigation system sends encryption navigation signal, by catching acquisition code phase, cannot can not complete the initialization of local code oscillator, thus can not navigation by recognition satellite.
Existing satellite recognition technology also has spectrogram to contrast identification satellite.User does spectrum analysis to what receive communications satellite signal, compares, identify satellite according to the display graphics of frequency spectrograph and the standard frequency spectrum figure of satellite.But receive signal spectrum to change due to the difference of pseudo-code, so said method is inapplicable when pseudo-code the unknown, but provide a kind of thought of comparison.
It is ephemeris parameter contrast identification satellite that another satellite knows method for distinguishing.Obtain the ephemeris parameter of the satellite carrying out ephemeris parsing in advance, obtain the ephemeris parameter of arbitrary satellite to be determined, judge whether the ephemeris parameter parameter matching condition meeting existing ephemeris parameter and satellite to be determined; If not, then determine that satellite to be determined is usable satellite; If so, then unavailable satellite is defined as.This technology just can reach the object of identification satellite by simple computation, improve the efficiency of satellite identification.But the prerequisite that the method uses is the ephemeris parameter obtaining satellite to be determined, can not realize when pseudo-code the unknown.
Under Pseudo-Random Noise Code unknown situation, utilize without the Continuous Tracking of code carrier estimation technology realization to target carrier, obtain a series of Doppler shift, but each Doppler shift which Navsat corresponding remains the unknown.
Summary of the invention
The present invention proposes a kind of non-cooperation Navsat based on Doppler shift feature and know method for distinguishing, utilize measured value and the priori value of the Doppler shift containing receiver frequency difference, set up the coupling index being easy to calculate, error hiding rate is low, and adopt dichotomy to obtain high-precision frequency difference estimation value efficiently; And the proportion of residual error is mated according to each Doppler shift, the strategy that employing global registration, local are rejected improves the overall confidence level of satellite identification.
The present invention adopts following technical scheme for solving its technical matters:
A method for distinguishing known by non-cooperation Navsat based on Doppler shift feature, comprises the steps:
(1) navigation satellite signal is converted to digital medium-frequency signal by the radio-frequency front-end of low rail user satellite receiver, utilizes the continuous carrier without code carrier auxiliary Technical Follow-Up intermediate-freuqncy signal, and obtains the Doppler shift measurement value of each navigation satellite signal;
(2) according to the preliminary orbit parameter of known low rail user satellite and the Navsat ephemeris of ground cycle upper note, the priori value of a series of Doppler shift is calculated;
(3) the Doppler shift priori value that Doppler shift measurement value step (1) obtained and step (2) obtain is arranged in two groups of samples according to sequence respectively, adopts dichotomizing search to make the consistent corresponding frequency difference estimation value of two class frequencys;
(4) according to the proportion of each Doppler shift coupling residual error, the method that employing global registration, local are rejected rejects the Navsat that it fails to match.
In described step (1), the Doppler shift measurement value of navigation satellite signal is expressed as
(1)
In formula,
λfor carrier wavelength,
for user's satellite is to the pseudorange rates true value of Navsat,
for user's satellite receiver clock frequency error,
nfor the measuring error of Doppler shift,
kbe
knavsat.
In described step (2), the priori value of Doppler shift is expressed as:
(2)
In formula,
with
be respectively
kthe position of Navsat and velocity;
with
be respectively position and the velocity of user's satellite;
with
be respectively the Distance geometry distance rate that user's satellite to Navsat contains error.
In described step (3), the frequency range of dichotomizing search is
, step-size in search is
,
be continuous function, and have
.
In described step (4), the condition of local rejecting Doppler shift measurement value can be expressed as:
In formula,
for frequency difference estimation value,
for Doppler shift measurement,
for the priori value of Doppler shift,
m
For threshold value.
Beneficial effect of the present invention is as follows:
1, the non-cooperation Navsat recognition methods based on Doppler shift that the present invention proposes can realize the identification of Navsat under pseudo-code unknown situation, supplementing as conventional satellite recognition methods, improves the recognition capability of nautical star under conflict condition.
2, the method comparing common pseudo-code match cognization Navsat only can realize the identification of nautical star, and the method that the present invention proposes not only can navigation by recognition satellite, can also obtain comparatively accurate receiver frequency difference estimation value.
3, search one by one of the prior art of comparing obtains frequency difference estimation value and compares, and the present invention adopts dichotomy to find frequency difference estimation value, improves search efficiency and numerical precision; And the application considers the impact of the factor such as noise and measuring error, propose the strategy of global registration, local rejecting, and give the index rejected and abandon, improve the overall confidence level of satellite identification.
Accompanying drawing explanation
Fig. 1 is based on the mentality of designing block diagram of the non-cooperation Navsat identification of Doppler shift feature.
Fig. 2 (a) is the situation of zero point between right half-court; Figure (b) is the situation of zero point between left half-court.
Embodiment
Below in conjunction with accompanying drawing, the invention is described in further details.
The method that the present invention proposes can when pseudo-code the unknown navigation by recognition satellite: navigation satellite signal is converted to digital medium-frequency signal by the radio-frequency front-end of low orbit satellite receiver, through without can obtaining the carrier signal of different frequency displacement after code carrier auxiliary technology and measuring its Doppler shift; Because the preliminary orbit of low rail user satellite is known, and the ephemeris of Navsat can by ground be noted, so can calculate the priori value of a series of Doppler shift; Doppler shift measurement value containing receiver frequency difference and priori value are arranged in two groups of samples according to sequence respectively, unanimously correspond to criterion to realize two class frequencys, adopt dichotomy effective search frequency difference estimation value; And the proportion of residual error is mated according to each Doppler shift, the strategy that employing global registration, local are rejected improves the overall confidence level of satellite identification.
Design basic ideas based on the non-cooperation Navsat identification of Doppler shift feature are: as shown in Figure 1, by user's satellite RF front end, navigation satellite signal is converted to digital medium-frequency signal, utilizes the continuous carrier without code carrier auxiliary Technical Follow-Up intermediate-freuqncy signal and measure the Doppler shift extracting each nautical star signal; By the nautical star ephemeris computation Doppler shift priori value of preliminary orbit parameter and upper note.The measured value of Doppler shift and priori value are arranged in two groups of samples according to sequence respectively, unanimously correspond to criterion to realize two class frequencys, adopt dichotomy fast search frequency difference estimation value; And the proportion of residual error is mated according to each Doppler shift, the strategy that employing global registration, local are rejected improves the overall confidence level of satellite identification.
1, based on nautical star identification and the frequency difference estimation index of frequency shift features
Suppose that user's satellite reception is to
kthe signal of Navsat, Doppler shift measurement value can be expressed as
(1)
In formula,
λfor carrier wavelength,
for user's satellite is to the pseudorange rates true value of Navsat,
for user's satellite receiver clock frequency error,
nfor the measuring error of Doppler shift.
The Navsat ephemeris of known preliminary orbit and upper note, can calculate the Doppler shift priori value of a series of estimation:
(2)
In formula,
with
be respectively position and the velocity of Navsat, obtained by the Navsat ephemeris of upper note;
with
be respectively position and the velocity of user's satellite, obtained by orbit prediction;
with
be respectively the Distance geometry distance rate that user's satellite to Navsat contains error.
From formula (1), (2), do not consider the impact of priori radical error and measuring error, the Doppler shift of measurement
with the Doppler shift of prior estimate
between difference on the frequency be the clock frequency error of user's satellite receiver.
Suppose that the some time is carved with
nvisible satellite, by the Doppler shift measurement value of visible satellite signal
(
krepresent the
kvisible satellite,
) and priori value
arrange from low to high respectively.Due to the existence of receiver clock frequency difference, the two has fixing difference on the frequency, introduces
reference quantity
, realize the consistent correspondence of two kinds of frequencies.Calculating contains
's
with
frequency difference absolute value sum
e; When
ethink when getting minimum value that two kinds of frequencies are unanimously corresponding, and by now
be called frequency difference estimation value
.
eobtain minimum value can be expressed as:
(3)
But, priori radical not precisely, the factor such as noise and measuring error makes two kinds of frequencies not mate completely.On the basis that most of frequency is alignd, adopt the strategy of global registration, local rejecting.Namely exist
ewhen minimum, if the ratio of the coupling residual error of certain satellite and global error exceedes threshold value
m, then corresponding actual measurement Doppler shift is rejected.The condition rejecting Doppler shift can be expressed as:
(4)
2, matching algorithm optimization
Receiver clock frequency error is bounded, so
span be also conditional.Suppose that frequency range to be searched is
, step-size in search is
, all estimation points so covering hunting zone are:
，
(5)
For above-mentioned search procedure, need search
individual Frequency point.Suppose that the inclined scope of receiver clock is
, the step-length of each search is
, so need search 201 Frequency points just can find frequency difference estimation value, calculation times is many, and efficiency is low, limits the speed of coupling.
When two class frequencys are unanimously corresponding,
ewhen obtaining minimum value, corresponding frequency difference sum
sbe 0, namely when
scorresponding when=0
for frequency difference estimation value.
Frequency difference sum can be expressed as:
(6)
In interval
on,
be continuous function, and have
, so use dichotomy constantly
zero point be divided into two between location, make interval two end points Step wise approximation zero points, and then obtain frequency difference estimation value.Make a concrete analysis of as follows:
1) frequency range to be searched is
, choose the coordinate at 1/2 interval place
,
mhunting zone is divided into two intervals
,
, make
sthe frequency of=0 is certain to drop on that one of them is interval, and two kinds of possible situations as shown in Figure 2;
2) calculate
,
if,
(now zero point is in interval
), as Fig. 2 (a), then give up interval
, order
; If
(now zero point is in interval
), as Fig. 2 (b), then give up interval
, order
;
3) repeat 1), 2), until
,
distance be less than setting accuracy
, now get
.
Adopt dichotomy and progressively change
acquisition frequency difference estimation value is compared, and calculated amount reduces greatly, improves the efficiency of coupling, can also obtain more accurate estimated value by improving setting accuracy.
3, simulating, verifying
In order to verify nautical star identification matching algorithm, the present invention has built satellite simulation platform, and wherein Navsat constellation is made up of 24 gps satellites, and the initial position of user's satellite is
, initial velocity is
.Signal carrier-to-noise ratio is 45dB-Hz, and after down coversion, the intermediate frequency of signal is 0.2046MHz, and intermediate frequency data sample frequency is 1.023MHz.The damping factor of phaselocked loop is 0.637, and loop bandwidth is 20Hz, and integral time is 5ms, and voltage controlled oscillator sensitivity is 0.0085Hz/V.Suppose receiver clock frequency error
, setting accuracy is
ε=2Hz.
Follow the tracks of 400ms without code carrier recovery loop to disappear a yard intermediate frequency data, every 5ms exports a Doppler shift measurement value (Doppler shifts of two frequency multiplication carrier waves).In the corresponding moment, calculate Doppler shift priori value.When containing measuring error, first run coupling is carried out to two class frequencys.When two class frequencys are unanimously to residual absolute value sum minimum value during correspondence
, frequency difference estimation value
.Doppler shift measurement value now containing frequency difference estimation value, priori value and the coupling residual error of the two are as shown in table 1.Judge each coupling residual error with
ratio whether exceed threshold value, and reject and exceed the Doppler shift corresponding to ratio of thresholding.Choose threshold value
, in table 1 the 4th, 7 satellite coupling residual error with
ratio be 0.28,0.4, therefore reject corresponding Doppler shift.Measured value after rejecting and priori value are mated, again when two class frequencys are unanimously to residual absolute value sum minimum value during correspondence
, frequency difference estimation value
.
The Doppler shift priori value of table 1 containing frequency difference estimation value, measured value and frequency difference absolute value
By analyzing above and simulating, verifying, the algorithm of the non-cooperation Navsat identification based on Doppler shift feature that the present invention proposes can realize mating of when pseudo-code is unknown Doppler shift and nautical star, and can obtain frequency difference estimation value comparatively accurately.The method that the present invention proposes can supplementing as conventional satellite recognition methods, improves the recognition capability of the nautical star under conflict condition.
Claims (5)
1. a method for distinguishing known by the non-cooperation Navsat based on Doppler shift feature, it is characterized in that, comprises the steps:
(1) navigation satellite signal is converted to digital medium-frequency signal by the radio-frequency front-end of low rail user satellite receiver, utilizes the continuous carrier without code carrier auxiliary Technical Follow-Up intermediate-freuqncy signal, and obtains the Doppler shift measurement value of each navigation satellite signal;
(2) according to the preliminary orbit parameter of known low rail user satellite and the Navsat ephemeris of ground cycle upper note, the priori value of a series of Doppler shift is calculated;
(3) the Doppler shift priori value that Doppler shift measurement value step (1) obtained and step (2) obtain is arranged in two groups of samples according to sequence respectively, adopts dichotomizing search to make the consistent corresponding frequency difference estimation value of two class frequencys;
(4) according to the proportion of each Doppler shift coupling residual error, the method that employing global registration, local are rejected rejects the Navsat that it fails to match.
2. method for distinguishing known by a kind of non-cooperation Navsat based on Doppler shift feature according to claim 1, and it is characterized in that, in step (1), the Doppler shift measurement value of navigation satellite signal is expressed as
(1)
In formula,
λfor carrier wavelength,
for user's satellite is to the pseudorange rates true value of Navsat,
for user's satellite receiver clock frequency error,
nfor the measuring error of Doppler shift,
kbe
knavsat.
3. method for distinguishing known by a kind of non-cooperation Navsat based on Doppler shift feature according to claim 1, and it is characterized in that, in step (2), the priori value of Doppler shift is expressed as:
(2)
In formula,
with
be respectively
kthe position of Navsat and velocity;
with
be respectively position and the velocity of user's satellite;
with
be respectively the Distance geometry distance rate that user's satellite to Navsat contains error,
λfor carrier wavelength.
4. method for distinguishing known by a kind of non-cooperation Navsat based on Doppler shift feature according to claim 1, and it is characterized in that, in step (3), the frequency range of dichotomizing search is
, step-size in search is
,
be continuous function, and have
.
5. method for distinguishing known by a kind of non-cooperation Navsat based on Doppler shift feature according to claim 1, it is characterized in that, in step (4), the condition of local rejecting Doppler shift measurement value can be expressed as:
In formula,
for frequency difference estimation value,
for Doppler shift measurement,
for the priori value of Doppler shift,
m
For threshold value.
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Cited By (5)
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| CN106054138A (en) * | 2016-07-29 | 2016-10-26 | 西安电子科技大学 | Jagged Doppler frequency shift selection method for DDMA waveform |
| CN106772502A (en) * | 2016-12-07 | 2017-05-31 | 中国电子科技集团公司第五十四研究所 | Low orbit satellite backup navigation system Doppler positioning calculation method |
| CN111221011A (en) * | 2018-11-26 | 2020-06-02 | 千寻位置网络有限公司 | GNSS positioning method and device based on machine learning |
| CN113109850A (en) * | 2021-05-14 | 2021-07-13 | 长沙学院 | GNSS satellite navigation positioning-free rapid rough frequency difference estimation method |
| CN115825996A (en) * | 2022-12-05 | 2023-03-21 | 中国民航大学 | Aircraft independent position verification method based on Doppler frequency shift change quantity |
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Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN106054138A (en) * | 2016-07-29 | 2016-10-26 | 西安电子科技大学 | Jagged Doppler frequency shift selection method for DDMA waveform |
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| CN113109850A (en) * | 2021-05-14 | 2021-07-13 | 长沙学院 | GNSS satellite navigation positioning-free rapid rough frequency difference estimation method |
| CN113109850B (en) * | 2021-05-14 | 2022-07-15 | 长沙学院 | GNSS satellite navigation positioning-free rapid coarse frequency difference estimation method |
| CN115825996A (en) * | 2022-12-05 | 2023-03-21 | 中国民航大学 | Aircraft independent position verification method based on Doppler frequency shift change quantity |
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