CN105527635A - Method and device for capturing weak signals - Google Patents

Abstract

The invention provides a method for capturing weak signals. According to the method, the Doppler frequency offset and the transmission time of a captured strong signal satellite are acquired; the Doppler frequency offset of a non-captured weak signal satellite can be determined according to the Doppler frequency offset of the captured strong signal satellite; a spreading code period and a spreading code phase of the non-captured weak signal satellite can be determined according to the transmission time of the captured strong signal satellite. The invention further provides a device for capturing the weak signals.

Description

A kind of method and apparatus of catching feeble signal

Technical field

The present invention relates to auxiliary Beidou satellite airmanship, particularly relate to a kind of method and apparatus of catching feeble signal.

Background technology

At present, along with people are to the requirement of the feeble signal environment such as indoor and primary positioning time, assisted global navigational satellite system (Assisted-GlobalNavigationSatelliteSystem, A-GNSS) arises at the historic moment.A-GNSS by means of cordless communication network for navigation neceiver provides required supplementary, to support navigation neceiver station-keeping ability or the capture ability of enhanced navigation receiver under weak signal conditions.

Conventional navigation receiver realizes positioning function to be needed to capture 4 or above satellite-signal, and different satellite-signal has the pseudo-random code of different initial times and different Doppler shifts.Therefore, in order to search certain satellite-signal, navigation neceiver needs to carry out two-dimensional search usually, pseudo-random codes different to each initial time on each possible Doppler shift is searched for, and auxiliary type navigation neceiver utilizes the auxiliary time, ephemeris/almanac, navigation neceiver position can estimate Doppler frequency deviation that satellite motion causes thus shorten capture frequency search volume.But, the Doppler shift that local clock frequency deviation causes can not be estimated when there is no given local clock frequency deviation, and less local clock frequency deviation can produce the Doppler shift of thousand hertz (Hz), acquisition search space can be increased like this, affect primary positioning time.

3GPPTS36.171 defines the minimum supplementary collection of A-GNSS technology, comprise time supplementary, almanac/ephemeris supplementary, customer location supplementary etc., according to the definition of 3GPP standard, cordless communication network can provide two kinds of different time supplementary modes: during essence auxiliary (precision be ± 10 μ s) and thick time assist (precision is ± 2s).

Existing receiver is when essence under auxiliary positioning mode, by time of obtaining from cordless communication network, almanac/ephemeris, customer position information, Doppler frequency deviation and the code phase of satellite can be estimated, thus reduce the two-dimensional search space of acquiring satellite frequency and code phase.For GPS (GlobalPositioningSystem, and dipper system GPS), the length of ranging code is 1ms, time precision auxiliary during essence is less than 1ms, therefore the edge of navigation message bit can be estimated, the coherent integration time that further increase is caught, improves the sensitivity of catching, and realizes high sensitivity location under feeble signal environment.

But, receiver under auxiliary positioning mode, because time precision is greater than the length of a ranging code, can not be predicted code phase and navigation message bit edge when thick, therefore under identical supplementary, the sensitivity of catching when assisting when the sensitivity of catching can be less than essence.And, due to actual environment weather, the reason such as to block, a lot of satellite-signal power ratio is fainter, often can only capture stronger a little one or two satellite-signals, therefore can not complete location.

In sum, receiver is when thick under auxiliary positioning mode, and the fast Acquisition how realizing feeble signal has become urgent problem in assistant positioning system.

Summary of the invention

In view of this, the embodiment of the present invention is expected to provide a kind of method and apparatus of catching feeble signal, can make receiver when thick, realize the fast Acquisition of feeble signal under auxiliary positioning mode.

For achieving the above object, the technical scheme of the embodiment of the present invention is achieved in that

The embodiment of the present invention provides a kind of method of catching feeble signal, and the method comprises:

Obtain Doppler frequency deviation and the transmission time of the strong signal satellite of having caught;

The Doppler frequency deviation of the weak signal satellite of not catching is determined according to the Doppler frequency deviation of the obtained strong signal satellite of having caught;

Spreading code cycle and the spreading code phase place of the weak signal satellite of not catching is determined according to the transmission time of the obtained strong signal satellite of having caught.

In such scheme, the described Doppler frequency deviation according to the obtained strong signal satellite of having caught determines that the Doppler frequency deviation of the weak signal satellite of not catching comprises:

Utilize the ephemeris information of satellite, thick time non-cutting time and receiver reference position coordinate determine the Doppler frequency deviation estimated value of current visible satellite; The strong signal satellite of having caught described in described current visible satellite comprises and the weak signal satellite of not catching;

According to the obtained Doppler frequency deviation of the strong signal satellite of having caught and the Doppler frequency deviation estimated value of determined current visible satellite, determine the Doppler frequency deviation of the weak signal satellite of not catching.

In such scheme, the described transmission time according to the obtained strong signal satellite of having caught determines that the spreading code cycle of the weak signal satellite of not catching and spreading code phase place comprise:

Utilize the transmission time of the strong signal satellite of having caught obtained to correct the receiver reference time, obtain the receiver reference time after correcting;

According to ephemeris information and the receiver reference position coordinate of the receiver reference time after correction, satellite, determine spreading code cycle and the spreading code phase place of the weak signal satellite of not catching.

In such scheme, describedly utilize the ephemeris information of satellite, thick time non-cutting time and receiver reference position coordinate determine that the Doppler frequency deviation estimated value of current visible satellite comprises:

According to the ephemeris information of satellite, time thick, non-cutting time and receiver reference position coordinate determine the position coordinates of current visible satellite, and determine current visible satellite corresponding moment t non-cutting time when thick further _kspeed; Again according to determined current visible satellite at t _kthe speed in moment determines the Doppler frequency deviation estimated value of described current visible satellite signal.

In such scheme, the span of the number N1 of described strong signal satellite of having caught is 1≤N1≤3.

The embodiment of the present invention also provides a kind of device of catching feeble signal, and this device comprises: strong signal capture module, doppler correction module and spreading code estimation module; Wherein,

Described strong signal capture module, for obtaining Doppler frequency deviation and the transmission time of the strong signal satellite of having caught;

Described doppler correction module, for determining the Doppler frequency deviation of the weak signal satellite of not catching according to the Doppler frequency deviation of the obtained strong signal satellite of having caught;

Described spreading code estimation module, for determining spreading code cycle and the spreading code phase place of the weak signal satellite of not catching according to the transmission time of the obtained strong signal satellite of having caught.

In such scheme, described doppler correction module comprises Doppler's estimation module and Doppler's determination module; Wherein,

Described Doppler's estimation module, for utilizing the ephemeris information of satellite, thick time non-cutting time and receiver reference position coordinate determine the Doppler frequency deviation estimated value of current visible satellite; The strong signal satellite of having caught described in described current visible satellite comprises and the weak signal satellite of not catching;

Described Doppler's determination module, for according to the obtained Doppler frequency deviation of the strong signal satellite of having caught and the Doppler frequency deviation estimated value of determined current visible satellite, determines the Doppler frequency deviation of the weak signal satellite of not catching.

In such scheme, described spreading code estimation module is used for, and utilizes the transmission time of the strong signal satellite of having caught obtained to correct the receiver reference time, obtains the receiver reference time after correcting; According to ephemeris information and the receiver reference position coordinate of the receiver reference time after correction, satellite, determine spreading code cycle and the spreading code phase place of the weak signal satellite of not catching.

In such scheme, described Doppler's estimation module is used for, according to the ephemeris information of satellite, time thick, non-cutting time and receiver reference position coordinate determine the position coordinates of current visible satellite, and determine current visible satellite corresponding moment t non-cutting time when thick further _kspeed; Again according to determined current visible satellite at t _kthe speed in moment determines the Doppler frequency deviation estimated value of described current visible satellite signal.

In such scheme, the span of the number N1 of the strong signal satellite that described strong signal capture module has been caught is 1≤N1≤3.

The method and apparatus of feeble signal that what the embodiment of the present invention provided catch, obtains Doppler frequency deviation and the transmission time of the strong signal satellite of having caught; The Doppler frequency deviation of the weak signal satellite of not catching is determined according to the Doppler frequency deviation of the obtained strong signal satellite of having caught; Spreading code cycle and the spreading code phase place of the weak signal satellite of not catching is determined according to the transmission time of the obtained strong signal satellite of having caught.So, on the basis of the Doppler frequency deviation of the weak signal satellite accurately determining not catch, spreading code cycle and spreading code phase place, the two-dimensional search space of acquiring satellite frequency and code phase can be reduced, thus ensure that receiver realizes the fast Acquisition of feeble signal when thick under auxiliary positioning mode.

Accompanying drawing explanation

Fig. 1 is the realization flow schematic diagram that the embodiment of the present invention catches the method for feeble signal;

Fig. 2 is the specific implementation schematic flow sheet that the embodiment of the present invention catches the method for feeble signal;

Fig. 3 is the schematic diagram in the transmission time of the strong signal satellite that the embodiment of the present invention has been caught;

Fig. 4 is the composition structural representation that the embodiment of the present invention catches the device of feeble signal;

Fig. 5 is the composition structural representation that the embodiment of the present invention catches the doppler correction module in the device of feeble signal.

Embodiment

In embodiments of the present invention, Doppler frequency deviation and the transmission time of the strong signal satellite of having caught is obtained; The Doppler frequency deviation of the weak signal satellite of not catching is determined according to the Doppler frequency deviation of the obtained strong signal satellite of having caught; Spreading code cycle and the spreading code phase place of the weak signal satellite of not catching is determined according to the transmission time of the obtained strong signal satellite of having caught.

Below in conjunction with drawings and the specific embodiments, the present invention is further described in more detail.

Fig. 1 is the realization flow schematic diagram that the embodiment of the present invention catches the method for feeble signal, and as shown in Figure 1, the method that the embodiment of the present invention catches feeble signal comprises:

Step S10: the Doppler frequency deviation and the transmission time that obtain the strong signal satellite of having caught;

Here, due under auxiliary positioning mode when receiver is in thick, so the span of the number N1 of strong signal satellite that receiver has captured is 1≤N1≤3.

Step S11: the Doppler frequency deviation determining the weak signal satellite of not catching according to the Doppler frequency deviation of the obtained strong signal satellite of having caught;

Particularly, step S11 comprises the steps A and B; Wherein,

Steps A: utilize the ephemeris information of satellite, thick time non-cutting time and receiver reference position coordinate determine the Doppler frequency deviation estimated value of current visible satellite; The strong signal satellite of having caught described in described current visible satellite comprises and the weak signal satellite of not catching; Wherein, the span of the total N of current visible satellite is 2≤N≤34, and meets N=N1+N2; Wherein, N2 is the number of the weak signal satellite of not catching.

Particularly, according to the ephemeris information of satellite, time thick, non-cutting time and receiver reference position coordinate determine the position coordinates of current visible satellite, and determine current visible satellite corresponding moment t non-cutting time when thick further _kspeed; Again according to determined current visible satellite at t _kthe speed in moment determines the Doppler frequency deviation estimated value of described current visible satellite signal.

Step B: according to the obtained Doppler frequency deviation of the strong signal satellite of having caught and the Doppler frequency deviation estimated value of determined current visible satellite, determine the Doppler frequency deviation of the weak signal satellite of not catching.

Step S12: spreading code cycle and the spreading code phase place of determining the weak signal satellite of not catching according to the transmission time of the obtained strong signal satellite of having caught.

Particularly, first utilize the transmission time of the strong signal satellite of having caught obtained to correct the receiver reference time, obtain the receiver reference time after correcting; Again according to ephemeris information and the receiver reference position coordinate of the receiver reference time after correction, satellite, determine spreading code cycle and the spreading code phase place of the weak signal satellite of not catching.

Here, the described spreading code cycle refers to the integer number of spreading code within a navigation message bit cycle.For Big Dipper geostationary orbit (GEO) satellite, because the navigation message bit cycle is 2ms, therefore the value in spreading code cycle is less than or equal to 2ms; For native to this world geo-stationary orbit (NGEO) satellite, because the navigation message bit cycle is 20ms, therefore the value in spreading code cycle is less than or equal to 20ms.In addition, because a spreading code of big-dipper satellite comprises 2046 chips, so the value of spreading code phase place is less than or equal to 2046.

So, by the Doppler frequency deviation of the determined weak signal satellite of not catching of the embodiment of the present invention, doppler searching scope can be reduced, simultaneously, utilize the embodiment of the present invention determined weak signal satellite spreading code cycle of not catching and spreading code phase place, the edge of Big Dipper GEO satellite-signal navigation message and Neuman-Hoffman (NH) code phase of NGEO satellite can be calculated fast, increase the coherent integration time of catching further, thus realize the fast Acquisition of weak signal.

Fig. 2 is the specific implementation schematic flow sheet that the embodiment of the present invention catches the method for feeble signal, and as shown in Figure 2, the method that the embodiment of the present invention catches feeble signal comprises:

Step S20: the Doppler frequency deviation and the transmission time that obtain the strong signal satellite of having caught;

Step S21: utilize the ephemeris information of satellite, thick time non-cutting time and receiver reference position coordinate determine the Doppler frequency deviation estimated value of current visible satellite; The strong signal satellite of having caught described in described current visible satellite comprises and the weak signal satellite of not catching;

Particularly, described step S21 comprises:

Step 1, according to the ephemeris information of satellite, time thick, non-cutting time and receiver reference position coordinate determine the position coordinates of current visible satellite, and determine current visible satellite corresponding moment t non-cutting time when thick further _kspeed

Particularly, due to the position coordinates of Big Dipper GEO satellite and NGEO satellite and speed calculation method different, therefore need to calculate respectively, circular is as follows:

1) in GC2000 coordinate system, for NGEO satellite, according to the ephemeris information of satellite, the t that non-cutting time is corresponding when thick _kmoment, the position coordinates (X of current visible satellite _k, Y _k, Z _k) computing formula as follows:

${\mathrm{\Ω}}_k={\mathrm{\Ω}}_0+(\stackrel{.}{\mathrm{\Ω}}-{\stackrel{.}{\mathrm{\Ω}}}_e)*t_k-{\stackrel{.}{\mathrm{\Ω}}}_e*t_{\mathrm{oe}};$

$\left\{\begin{array}{c}{X}_k=x_k\cos {\mathrm{\Ω}}_k-y_k\cos i_k\sin {\mathrm{\Ω}}_k\\ Y_k=x_k\sin {\mathrm{\Ω}}_k-y_k\cos i_k\cos {\mathrm{\Ω}}_k\\ Z_k=y_k\sin i_k\end{array}\right.;$

Wherein, Ω _kfor right ascension of ascending node epoch (solid system), Ω ₀for the right ascension of ascending node calculated by the reference time, for right ascension of ascending node rate of change, for the earth rotation speed under CGCS2000 coordinate system, be 7.2921150*10e-5rad/s, t _kfor epoch of observation is to the mistiming with reference to epoch, t _oefor the ephemeris reference time, x _k, y _kfor the coordinate of satellite in orbit plane, i _kfor the orbit inclination after correction.

Further, NGEO satellite is at t _kthe speed in moment computing formula as follows:

$\left\{\begin{array}{c}{V}_x=-Y_k{{\mathrm{\Ω}}_k}^{\′}-(y_k^{\′}\cos i_k-y_k\sin i_k*{i_k}^{\′})\sin {\mathrm{\Ω}}_k\\ +x_k^{\′}\cos {\mathrm{\Ω}}_k\\ V_y=X_k{{\mathrm{\Ω}}_k}^{\′}+(y_k^{\′}\cos i_k-y_k\sin i_k*{i_k}^{\′})\cos {\mathrm{\Ω}}_k\\ +x_k^{\′}\sin {\mathrm{\Ω}}_k\\ V_z=y_k^{\′}\sin i_k+y_k{i}_k^{\′}\cos i_k\end{array}\right.;$

Wherein, x' _k, y' _kbe respectively x _k, y _kto t _kderivative, Ω _k', i _k' be respectively Ω _k, i _kto t _kderivative.

2) in GC2000 coordinate system, for GEO satellite, according to the ephemeris information of satellite, the t that non-cutting time is corresponding when thick _kmoment, the position coordinates (X of current visible satellite _k, Y _k, Z _k) computing formula as follows:

${\mathrm{\Ω}}_k={\mathrm{\Ω}}_0+\stackrel{.}{\mathrm{\Ω}}*t_k-{\stackrel{.}{\mathrm{\Ω}}}_e*t_{\mathrm{oe}};$

$\left\{\begin{array}{c}{X}_{\mathrm{GK}}=x_k\cos {\mathrm{\Ω}}_k-y_k\cos i_k\sin {\mathrm{\Ω}}_k\\ Y_{\mathrm{GK}}=x_k\sin {\mathrm{\Ω}}_k-y_k\cos i_k\sin {\mathrm{\Ω}}_k\\ Z_{\mathrm{GK}}=y_k\sin i_k\end{array}\right.;$

$\left\{\begin{array}{c}{X}_k=\cos \left(\mathrm{\φ}\right)\·X_{\mathrm{GK}}+k_1\·\sin \left(\mathrm{\φ}\right)\·Y_{\mathrm{GK}}+k_2\·\sin \left(\mathrm{\φ}\right)\·Z_{\mathrm{GK}}\\ Y_k=-\sin \left(\mathrm{\φ}\right)\·X_{\mathrm{GK}}+k_1\·\cos \left(\mathrm{\φ}\right)\·Y_{\mathrm{GK}}+k_2\·\cos \left(\mathrm{\φ}\right)\·Z_{\mathrm{GK}}\\ Z_k=-k_2\·Y_{\mathrm{GK}}+k_1\·Z_{\mathrm{GK}}\end{array}\right.;$

Wherein, k ₁=cos (-5 °), k ₂=sin (-5 °), Ω _kfor right ascension of ascending node epoch (solid system), Ω ₀for the right ascension of ascending node calculated by the reference time, for right ascension of ascending node rate of change, for the earth rotation speed under CGCS2000 coordinate system, be 7.2921150*10e-5rad/s, t _kfor epoch of observation is to the mistiming with reference to epoch, t _oefor the ephemeris reference time, x _k, y _kfor the coordinate of satellite in orbit plane, i _kfor the orbit inclination after correction.

Further, GEO satellite is at t _kthe speed in moment computing formula as follows:

$\left\{\begin{array}{c}{V}_x={\stackrel{.}{\mathrm{\Ω}}}_e\·Y_k+\cos \left(\mathrm{\φ}\right)\·{\stackrel{.}{X}}_{\mathrm{GK}}+\sin \left(\mathrm{\φ}\right).[k_1\·{\stackrel{.}{Y}}_{\mathrm{GK}}+k_2\·{\stackrel{.}{Z}}_{\mathrm{GK}}]\\ V_y=-{\stackrel{.}{\mathrm{\Ω}}}_e\·X_k-\sin \left(\mathrm{\φ}\right)\·{\stackrel{.}{X}}_{\mathrm{GK}}+\cos \left(\mathrm{\φ}\right)\·[k_1\·{\stackrel{.}{Y}}_{\mathrm{GK}}+k_2\·{\stackrel{.}{Z}}_{\mathrm{GK}}]\\ V_z=-k_2\·{\stackrel{.}{Y}}_{\mathrm{GK}}{+k}_1\·{\stackrel{.}{Z}}_{\mathrm{GK}}\end{array}\right.;$

Wherein, for to t _kderivative.

Step 2, according to the determined current visible satellite of step 1 at t _kthe speed in moment determine the Doppler frequency deviation estimated value f of described current visible satellite signal _d.

Particularly, described f _dcomputing formula as follows:

$f_d=f\frac{{\stackrel{.}{v}}^{\left(s\right)}\·e^{\left(s\right)}}{c};$

$e^{\left(s\right)}=\frac{\left(X_k^{\left(s\right)}{Y}_k^{\left(s\right)}{Z}_k^{\left(s\right)}\right)-\left(X_{\mathrm{rec}}{Y}_{\mathrm{rec}}{Z}_{\mathrm{rec}}\right)}{\left|\right|\left(X_k^{\left(s\right)}{Y}_k^{\left(s\right)}{Z}_k^{\left(s\right)}\right)-\left(X_{\mathrm{rec}}{Y}_{\mathrm{rec}}{Z}_{\mathrm{rec}}\right)\left|\right|};$

Wherein, the carrier frequency f=1561.098MHz of current visible satellite signal, be the relative velocity on s current visible satellite and receiver line direction, c is the light velocity.E ^(s)for current visible satellite signal at t _kmoment from receiver to the unit measurement vector of current visible satellite, (X _rec, Y _rec, Z _rec) be t _kreception machine position coordinates, for t _kthe position coordinates of moment s current visible satellite under CGCS2000 coordinate system.

Step S22: according to the obtained Doppler frequency deviation of the strong signal satellite of having caught and the Doppler frequency deviation estimated value of determined current visible satellite, determine the Doppler frequency deviation of the weak signal satellite of not catching.

Particularly, by the Doppler frequency deviation estimated value of all current visible satellite determined estimated by step S21 be ${\stackrel{.}{F}}_d=\left[\begin{array}{cccc}{f}_{d1}& f_{d2}& ......& f_{\mathrm{dN}}\end{array}\right],$ 2≤N≤34, two vectors can be split as with wherein, for the Doppler frequency deviation estimated value of strong signal satellite of having caught, for the Doppler frequency deviation estimated value of weak signal satellite do not captured, wherein, 1≤N1≤3, N=N1+N2.And the Doppler frequency deviation of the strong signal of having caught that receiver obtains is $\stackrel{.}{F_{\mathrm{ds}\_\mathrm{acq}}}=\left[\begin{array}{ccc}{f}_{\mathrm{ds}\_\mathrm{acq}1}& ......& f_{\mathrm{ds}\_\mathrm{acqN}1}\end{array}\right].$

Therefore, because Doppler's estimation of deviation that the clock of receiver is partially caused is wherein each component be the partially caused Doppler's estimation of deviation value of the clock of each the strong signal satellite captured.

It should be noted that, for a receiver, can think that receiver clock partial wave is dynamic very little, therefore, when the number N1 of the strong signal satellite captured meets 2≤N1≤3, by vector important being averaging obtain Δ F _d, and by Δ F _das the receiver frequency offset correction amount of the weak signal satellite of not catching.Certainly, when number N1=1 for the strong signal satellite captured, obviously, only has one-component Δ F _d, therefore can directly by Δ F _das the receiver frequency offset correction amount of the weak signal satellite of not catching.

Further, Δ F is utilized _dcorrect the Doppler frequency deviation estimated value of the weak signal satellite of not catching, the Doppler frequency deviation of the weak signal satellite of not caught is

Step S23: utilize the transmission time of the strong signal satellite of having caught obtained to correct the receiver reference time, obtain the receiver reference time after correcting;

Particularly, the schematic diagram in the transmission time of the strong signal satellite of having caught shown in Fig. 3, as shown in Figure 3, the transmission time of a kth strong signal satellite is TOT ^k=SOW ^k+ Δ T ^k, wherein, represent a kth strong signal satellite and find SOW ^knavigation bit number afterwards, represent the spreading code periodicity of a kth strong signal satellite, the whole millisecond number namely after kth strong signal satellite transmission last navigation message bit complete, represent the code phase of a kth strong signal satellite.Like this, the transmission time of a kth strong signal satellite k=1 ~ N1.

Further, according to the computing formula of the position coordinates of aforesaid satellite-signal at TOT ^kmoment obtains the coordinate of k strong satellite-signal k=1 ~ N1, and the travel-time of passing through a kth strong signal satellite computing formula ${\mathrm{TOF}}_s^k=\sqrt{{(X_s^k-X_{\mathrm{rec}})}^2+{(Y_s^k-Y_{\mathrm{rec}})}^2+{(Z_s^k-Z_{\mathrm{rec}})}^2}/c$ Try to achieve the travel-time of a kth strong signal satellite.

Therefore, the receiver reference time of a kth strong signal satellite can be obtained for

It should be noted that, when the number N1 of the strong signal satellite captured meets 2≤N1≤3, by being averaged the receiver reference time of obtained N1 strong signal satellite, obtaining the receiver reference time TOR after correcting _corrfor $\underset{k=1}{\overset{N1}{\mathrm{\Σ}}}{\mathrm{TOR}}_{\mathrm{corr}}^k/N1.$

So, by the step S23 of the embodiment of the present invention, the precision of local receive time effectively can be improved.

Step S24: according to ephemeris information and the receiver reference position coordinate of the receiver reference time after correction, satellite, determine spreading code cycle and the spreading code phase place of the weak signal satellite of not catching.

Particularly, step S24 comprises:

Step a, the computing formula according to the position coordinates of aforesaid satellite-signal is determined at TOR _corrthe co-ordinates of satellite of the weak signal that moment kth does not capture again according to formula ${\mathrm{TOF}}_w^k=\sqrt{{(X_w^k-X_{\mathrm{rec}})}^2+{(Y_w^k-Y_{\mathrm{rec}})}^2+{(Z_w^k-Z_{\mathrm{rec}})}^2}/c$ Calculate the travel-time of the weak signal satellite that kth does not capture further utilization obtain the transmission time of the weak signal satellite that kth does not capture

Step b, according to the transmission time of the weak signal satellite that obtained kth does not capture determine the spreading code cycle of the weak signal satellite that kth does not capture with spreading code phase place

Here, for Big Dipper GEO satellite, for NGEO satellite, $N_w^k=\mathrm{floor}(\mathrm{mod}({\mathrm{TOT}}_w^k,20\mathrm{ms})*1000).$

In addition, the spreading code phase place of weak signal satellite that do not capture of kth for $\mathrm{mod}({\mathrm{TOT}}_w^k,20\mathrm{ms})*2046000.$

So, by the Doppler frequency deviation of the determined weak signal satellite of not catching of embodiment of the present invention step S22, doppler searching scope can be reduced, simultaneously, utilize embodiment of the present invention step S24 determined weak signal satellite spreading code cycle of not catching and spreading code phase place, the edge of Big Dipper GEO satellite-signal navigation message and the NH code phase of NGEO satellite can be calculated fast, increase the coherent integration time of catching further, thus realize the fast Acquisition of weak signal.

Fig. 4 is the composition structural representation that the embodiment of the present invention catches the device of feeble signal, and as shown in Figure 4, the device that the embodiment of the present invention catches feeble signal comprises: strong signal capture module 10, doppler correction module 20 and spreading code estimation module 30; Wherein,

Described strong signal capture module 10, for obtaining Doppler frequency deviation and the transmission time of the strong signal satellite of having caught;

Here, due under auxiliary positioning mode when receiver is in thick, so the span of the number N1 of strong signal satellite that receiver can capture is 1≤N1≤3.

Described doppler correction module 20, for determining the Doppler frequency deviation of the weak signal satellite of not catching according to the Doppler frequency deviation of the obtained strong signal satellite of having caught;

Particularly, as shown in Figure 5, described doppler correction module 20 comprises Doppler's estimation module 21 and Doppler's determination module 22; Wherein,

Described Doppler's estimation module 21, for utilizing the ephemeris information of satellite, thick time non-cutting time and receiver reference position coordinate determine the Doppler frequency deviation estimated value of current visible satellite; The strong signal satellite of having caught described in described current visible satellite comprises and the weak signal satellite of not catching;

Particularly, described Doppler's estimation module 21 is according to the ephemeris information of satellite, and time thick, non-cutting time and receiver reference position coordinate determine the position coordinates of current visible satellite, and determines current visible satellite corresponding moment t non-cutting time when thick further _kspeed; Again according to determined current visible satellite at t _kthe speed in moment determines the Doppler frequency deviation estimated value of described current visible satellite signal.

Described Doppler's determination module 22, for according to the obtained Doppler frequency deviation of the strong signal satellite of having caught and the Doppler frequency deviation estimated value of determined current visible satellite, determines the Doppler frequency deviation of the weak signal satellite of not catching.

Described spreading code estimation module 30, for determining spreading code cycle and the spreading code phase place of the weak signal satellite of not catching according to the transmission time of the obtained strong signal satellite of having caught.

Particularly, described spreading code estimation module 30 first utilizes the transmission time of the strong signal satellite of having caught obtained to correct the receiver reference time, obtains the receiver reference time after correcting; Again according to ephemeris information and the receiver reference position coordinate of the receiver reference time after correction, satellite, determine spreading code cycle and the spreading code phase place of the weak signal satellite of not catching.

In actual applications, described strong signal capture module 10, doppler correction module 20, spreading code estimation module 30, Doppler's estimation module 21 and Doppler's determination module 22 all can be caught the realizations such as central processing unit (CPU), microprocessor (MPU), digital signal processor (DSP) or field programmable gate array (FPGA) in the device of feeble signal by the embodiment of the present invention; In addition, described strong signal capture module 10, doppler correction module 20 and submodule Doppler estimation module 21 thereof and Doppler's determination module 22 and spreading code estimation module 30 also can be realized by strong signal capture tracker, Doppler corrector and spreading code estimator respectively.

The above, be only preferred embodiment of the present invention, be not intended to limit protection scope of the present invention.

Claims (10)

1. catch a method for feeble signal, it is characterized in that, described method comprises:

Obtain Doppler frequency deviation and the transmission time of the strong signal satellite of having caught;

The Doppler frequency deviation of the weak signal satellite of not catching is determined according to the Doppler frequency deviation of the obtained strong signal satellite of having caught;

Spreading code cycle and the spreading code phase place of the weak signal satellite of not catching is determined according to the transmission time of the obtained strong signal satellite of having caught.

2. method according to claim 1, is characterized in that, the described Doppler frequency deviation according to the obtained strong signal satellite of having caught determines that the Doppler frequency deviation of the weak signal satellite of not catching comprises:

Utilize the ephemeris information of satellite, thick time non-cutting time and receiver reference position coordinate determine the Doppler frequency deviation estimated value of current visible satellite; The strong signal satellite of having caught described in described current visible satellite comprises and the weak signal satellite of not catching;

According to the obtained Doppler frequency deviation of the strong signal satellite of having caught and the Doppler frequency deviation estimated value of determined current visible satellite, determine the Doppler frequency deviation of the weak signal satellite of not catching.

3. method according to claim 1, is characterized in that, the described transmission time according to the obtained strong signal satellite of having caught determines that the spreading code cycle of the weak signal satellite of not catching and spreading code phase place comprise:

Utilize the transmission time of the strong signal satellite of having caught obtained to correct the receiver reference time, obtain the receiver reference time after correcting;

According to ephemeris information and the receiver reference position coordinate of the receiver reference time after correction, satellite, determine spreading code cycle and the spreading code phase place of the weak signal satellite of not catching.

4. method according to claim 2, is characterized in that, describedly utilize the ephemeris information of satellite, thick time non-cutting time and receiver reference position coordinate determine that the Doppler frequency deviation estimated value of current visible satellite comprises:

According to the ephemeris information of satellite, time thick, non-cutting time and receiver reference position coordinate determine the position coordinates of current visible satellite, and determine current visible satellite corresponding moment t non-cutting time when thick further _kspeed; Again according to determined current visible satellite at t _kthe speed in moment determines the Doppler frequency deviation estimated value of described current visible satellite signal.

5. method according to claim 1, is characterized in that, the span of the number N1 of described strong signal satellite of having caught is 1≤N1≤3.

6. catch a device for feeble signal, it is characterized in that, described device comprises: strong signal capture module, doppler correction module and spreading code estimation module; Wherein,

Described strong signal capture module, for obtaining Doppler frequency deviation and the transmission time of the strong signal satellite of having caught;

Described doppler correction module, for determining the Doppler frequency deviation of the weak signal satellite of not catching according to the Doppler frequency deviation of the obtained strong signal satellite of having caught;

Described spreading code estimation module, for determining spreading code cycle and the spreading code phase place of the weak signal satellite of not catching according to the transmission time of the obtained strong signal satellite of having caught.

7. device according to claim 6, is characterized in that, described doppler correction module comprises Doppler's estimation module and Doppler's determination module; Wherein,

Described Doppler's estimation module, for utilizing the ephemeris information of satellite, thick time non-cutting time and receiver reference position coordinate determine the Doppler frequency deviation estimated value of current visible satellite; The strong signal satellite of having caught described in described current visible satellite comprises and the weak signal satellite of not catching;

Described Doppler's determination module, for according to the obtained Doppler frequency deviation of the strong signal satellite of having caught and the Doppler frequency deviation estimated value of determined current visible satellite, determines the Doppler frequency deviation of the weak signal satellite of not catching.

8. device according to claim 6, is characterized in that, described spreading code estimation module is used for, and utilizes the transmission time of the strong signal satellite of having caught obtained to correct the receiver reference time, obtains the receiver reference time after correcting; According to ephemeris information and the receiver reference position coordinate of the receiver reference time after correction, satellite, determine spreading code cycle and the spreading code phase place of the weak signal satellite of not catching.

9. device according to claim 7, it is characterized in that, described Doppler's estimation module is used for, according to the ephemeris information of satellite, time thick, non-cutting time and receiver reference position coordinate determine the position coordinates of current visible satellite, and determine current visible satellite corresponding moment t non-cutting time when thick further _kspeed; Again according to determined current visible satellite at t _kthe speed in moment determines the Doppler frequency deviation estimated value of described current visible satellite signal.

10. device according to claim 6, is characterized in that, the span of the number N1 of the strong signal satellite that described strong signal capture module has been caught is 1≤N1≤3.