CN106597490A - Method for L1 assisting L2P (Y) of dual-frequency GPS receiver - Google Patents

Abstract

The invention provides a method for L1 assisting in L2P (Y) of a dual-frequency GPS receiver. The method includes the following steps: firstly capturing a L1-C/A code, obtaining the Doppler shift an initial code phase of a L1 signal, tracking the L1-C/A code, resolving the navigation message of the L1-C/A code, and acquiring current time from the navigation message; then removing the P code of a Q branch of the L1 signal, obtaining a L1_w signal containing w code; removing a local carrier of a L2P(Y), obtaining the signal containing P code and W code; removing the P code of the L2P(Y) signal, obtaining a signal which only contains the W code; finally removing an encrypted W code of the L2P(Y) code, obtaining the data of the L2P(Y). According to the invention, the method can substantially reduce the complexity of the dual-frequency GPS receiver and reduce operation amount.

Description

A kind of method that double-frequency GPS receiver L1 auxiliary L2P (Y) tracks

Technical field

The invention belongs to field of satellite navigation, is a kind of side for aiding in L2P (Y) to track suitable for double-frequency GPS receiver L1 Method.

Background technology

Double-frequency GPS receiver is while receiving the receiver of 2 frequency carrier signals, the receiver is using two frequencies to electricity It is different that absciss layer postpones, and can eliminate the impact that ionosphere postpones to electromagnetic wave.For all of GPS observation data, electricity The error of absciss layer is all intrinsic, but by the moonscope information with reference to two frequencies, can be effective by setting up model Eliminate this error.Therefore, double-frequency GPS receiver can be provided more rapidly, more accurately than single frequency receiving, more reliable positioning Test the speed.How simultaneously L1 and L2P (Y) signal carried out capturing, track and become crucial.

The method of traditional double-frequency GPS receiver is individually capture, two signals of tracking, search multiplicity and computational complexity It is very big, and be very difficult to except encryption W codes.

The content of the invention

In order to overcome the deficiencies in the prior art, the present invention to provide a kind of method that L1 auxiliary L2P (Y) tracks, make full use of The characteristics of L1, L2P (Y) signal time is synchronous, propagation path is identical, saves L2 captures, 3 big functions of L2-P code generators and decryption Module, is greatly reduced the complexity of double-frequency GPS receiver.

The technical solution adopted for the present invention to solve the technical problems is comprised the following steps：

Step one, captures L1-C/A codes, obtains the Doppler frequency shift f of L1 signals_d-l1With initial code phase positions C_phase-l1；

Step 2, tracks L1-C/A codes, calculates the navigation message of L1-C/A codes, and therefrom obtains current time t；

Step 3, generates the P code L1-P of L1 signals；

Step 4, removes the P codes of L1 signal Q branch roads, obtains the signal L1_w containing W codes；

Step 5, generates the local carrier of L2P (Y) signalWherein, f_I0It is local preferable load Ripple, f_l1For L1 signal frequency points, f_l2For L2P (Y) signal frequency point；

Step 6, removes the local carrier of L2P (Y), obtains the signal I of code containing P and W codes_l2-p-wAnd Q_l2-p-w；

Step 7, generates P codes L2_P (the t)=L1_P (t- τ) of L2P (Y) signal；Wherein, τ is the phase between L1-P and L2-P Potential difference is different；

Step 8, removes the P codes of L2P (Y) signal, obtains the signal I containing only W codes_l2-wAnd Q_l2-w；

Step 9, removes the encryption W codes of L2P (Y) signal, obtains data I of L2P (Y) signal_l2And Q_l2。

The invention has the beneficial effects as follows：

1. frequency proportions relation of the step five of the present invention according to L1, L2P (Y), the Doppler frequency shift by L1 signals are direct The Doppler frequency shift of L2P (Y) signal is obtained, tracking phase is directly entered, is saved L2P (Y) trapping module, greatly reduce computing Amount.

2. the step seven of the present invention directly generates L2-P, eliminates L2-P code generator modules by time delay L1-P, simplifies Computing.

3. the step nine of the present invention removes P code signal I with the L1_w signals of L1 signals and the carrier wave that goes of L2P (Y) signal_l2-w, Q_l2-wIt is multiplied, saves decryption functional module, simplified operation.

Description of the drawings

Fig. 1 is method of the present invention schematic diagram.

Specific embodiment

The present invention is further described with reference to the accompanying drawings and examples, and the present invention includes but are not limited to following enforcements Example.

As shown in figure 1, embodiments of the invention are comprised the following steps：

Step one：Capture L1-C/A codes, obtain the Doppler frequency shift f of L1 signals_d-l1With initial code phase positions C_phase-l1。

The signal capture of GPS is a search procedure, generally by carrier frequency and code phase to the satellite-signal This two dimension is scanned formula search to complete.Once signal it is searched to and confirmed, it is possible to obtain many of L1 signals General Le frequency displacement f_d-l1With initial code phase positions C_phase-l1。

Step 2：Tracking L1-C/A codes, calculate the navigation message of L1-C/A codes, and therefrom obtain current time t.

During tracking, receiver copies carrier wave and pseudo-code signal simultaneously, and both again respectively with receive Carrier wave and pseudo-code in the satellite-signal keeps synchronous, and replicating carrier wave and reception signal carries out mixing and can realize that carrier wave is peeled off, Duplication pseudo-code carries out being multiplied with reception signal and can realize that pseudo-code is peeled off, at this moment a data left code in signal is received, therefrom Obtain current time t.

Step 3：Generate the P code L1-P of L1 signals.

According to initial code phase positions C that step one is obtained_phase-l1And current time t that step 2 is obtained, generate by P codes public Formula obtains L1-P codes.

Step 4：Remove the P codes of L1 signal Q branch roads, obtain the signal L1_w containing W codes.

As the C/A codes of L1 signal I branch roads, when P codes and the P codes L1-P phase places complete for replicating of L1 signal Q branch roads During cause, both are multiplied and can just peel off the P codes of L1 signal Q branch roads, obtain the W code signal L1_w of L1.

Step 5：Generate the local carrier f of L2P (Y) signal_I-l2。

As L1 is identical with L2P (Y) propagation path, and the Doppler frequency shift of L1 signals is obtained by step one f_d-l1, the local carrier f of L2P (Y) signal can be obtained according to the proportionate relationship of L1 and L2P (Y)_I-l2, calculating process such as formula (1) It is shown.

Step 6：Remove the local carrier of L2P (Y), obtain the signal I of code containing P and W codes_l2-p-wAnd Q_l2-p-w。

I_{L2_p_w}=L2P (Y) × L_{2_carrier_I} (3)

Q_{L2_p_w}=L2P (Y) × L_{2_carrier_Q} (4)

Wherein, L2P (Y) is radio-frequency input signals, L_{2_carrier_I}It is L2P (Y) signal local carrier f_I-l2Cosine component, L_{2_carrier_Q}It is L2P (Y) signal local carrier f_I-l2Sinusoidal component, I_l2-p-w、Q_l2-p-wIt is that L2P (Y) signal removes carrier wave respectively In-phase branch signal afterwards and quadrature branch signal, they are all containing P codes and W codes.

Step 7：Generate the P code L2-P of L2P (Y) signal.

Due to the P codes adjusted in the P codes modulated in L1 signals and L2P (Y) signal be in same group of code, therefore step 3 it is raw Into L1 frequencies P code L1-P be exactly L2 frequencies P code L2-P, only due to due to ionosphere time delay and radio frequency time delay, The phase difference τ for having very little between L1-P and L2-P, Jing is caused to test the length that the difference value is probably 1 to 2 chips, calculated Shown in journey such as formula (2).

Step 8：Remove the P codes of L2P (Y) signal, obtain the signal I containing only W codes_l2-wAnd Q_l2-w.Calculating process such as formula (5), shown in formula (6).

I_l2-w=I_l2-p-w×L2_P (5)

Q_l2-w=Q_l2-p-w×L2_P (6)

I_l2-w、Q_l2-wIt is that L2P (Y) signal removes carrier wave, removes the signal after P codes, they are containing only W codes.

Step 9：Remove the encryption W codes of L2P (Y) signal, obtain data I of L2P (Y) signal_l2And Q_l2.Calculating process is such as Shown in formula (7) and formula (8).

I_l2=I_l2-w×L1_w (7)

Q_l2=Q_l2-w×L1_w (8)

Obtain pure information data I of L2P (Y) signal_l2And Q_l2Afterwards, subsequently just can complete to position, test the speed.

More than, nine steps can realize double-frequency GPS receiver L1 auxiliary L2P (Y) tracking, while tracing into L1 letters Number and L2P (Y) signal, so as to eliminate ionosphere effect, realize double-frequency GPS receiver it is quick, accurately, hi-Fix.

Claims (1)

1. a kind of method that double-frequency GPS receiver L1 auxiliary L2P (Y) tracks, it is characterised in that comprise the steps：

Step one, captures L1-C/A codes, obtains the Doppler frequency shift f of L1 signals_d-l1With initial code phase positions C_phase-l1；

Step 2, tracks L1-C/A codes, calculates the navigation message of L1-C/A codes, and therefrom obtains current time t；

Step 3, generates the P code L1-P of L1 signals；

Step 4, removes the P codes of L1 signal Q branch roads, obtains the signal L1_w containing W codes；

Step 5, generates the local carrier of L2P (Y) signalWherein, f_I0It is local desired carrier, f_l1For L1 signal frequency points, f_l2For L2P (Y) signal frequency point；

Step 6, removes the local carrier of L2P (Y), obtains the signal I of code containing P and W codes_l2-p-wAnd Q_l2-p-w；

Step 7, generates P codes L2_P (the t)=L1_P (t- τ) of L2P (Y) signal；Wherein, τ is the phase contrast between L1-P and L2-P It is different；

Step 8, removes the P codes of L2P (Y) signal, obtains the signal I containing only W codes_l2-wAnd Q_l2-w；

Step 9, removes the encryption W codes of L2P (Y) signal, obtains data I of L2P (Y) signal_l2And Q_l2。