CN102590835B - GPS/INS tightly integrated tracking loop Gauss code phase discriminator and design method thereof - Google Patents

Abstract

The invention proposes a GPS/INS deep combined tracking loop Gaussian code phase discriminator and a design method thereof. The Gaussian code phase discriminator of the present invention is constructed by adding an INS code phase discriminator module and a Gaussian code phase discriminator module on the basis of the traditional code phase discriminator. In the design method of the Gaussian code phase discriminator, the INS system uses the real-time code phase information generated by the GPS receiver code tracking loop to establish a synchronously working INS code phase discriminator, and will calculate the traditional code phase discriminator and the INS code phase discriminator in real time. The mean square error of the output data of the phase discriminator is used as a weight coefficient to measure the phase discriminator error of the traditional code phase discriminator and the INS code phase discriminator, thereby combining into a Gaussian code phase discriminator. The invention can increase the autocorrelation peak value of the pseudo-random code, improve the output characteristic of the phase detection under multi-path interference, and effectively reduce the phase tracking error of the code.

Description

The dark combined tracking loop of a kind of GPS/INS Gauss's code phase Discr. and method for designing thereof

Technical field

The present invention relates to GNSS (GPS (Global Position System))/INS (inertial navigation system) integrated navigation field, relate in particular to when multipath signal disturbs,, designed the dark combined tracking loop of a kind of GPS/INS Gauss code phase Discr. assisting down of INS information.

Background technology

According to the difference of the satellite receiver data source that information fusion adopted, generally the GPS/INS integrated navigation system is divided into pine combination, tightly combination and dark combination, GPS represents Global Positioning System (GPS), INS represents inertial navigation system.Dark combination has pine combination and tight combination incomparable advantage, it is the current research direction of GPS/INS integrated navigation system, dark combination technique has broken through the working method of the original track loop of satellite receiver, therefore, the redesign of track loop is become the research focus.The code phase Discr. is the key component of code tracking loop (DLL), and it has directly determined the discriminating precision of code phase, influences the code phase tracking error, so the code phase Discr. has influenced noise and the dynamic dispatching important performance of DLL to a great extent.

In DLL, the C/A sign indicating number elder generation that the local code generator produces carries out related operation with the C/A sign indicating number in the received signal, determines code phase error by the code phase Discr. then, and traditional code phase Discr. has:

(a) the incoherent hysteresis amplitude Discr. that subtracts in advance, before being called for short, it subtracts back amplitude Discr., it is more common a kind of code phase Discr. of usefulness, because this Discr. needs to calculate respectively leading, hysteresis auto-correlation amplitude, and these auto-correlation amplitudes all need just can try to achieve through opening radical sign, so calculated amount is bigger than normal, efficiency ratio is lower.For the relevant spacing of 0.5 code element, in ± 0.5 code element error originated from input scope, it produces good tracking error.But after the normalization, for the relevant spacing of 0.5 code element, error originated from input produces good tracking error during less than ± 1.5 code elements, and error originated from input was greater than ± 1.5 o'clock, and its can be because become unstable divided by 0.Owing to only need information leading, two branch roads that lag behind, so need two pairs of correlators to get final product.

(b) the incoherent after-power Discr. that subtracts in advance, it is that the non-coherent integration power on leading branch road and the hysteresis branch road is subtracted each other, this incoherent after-power method that subtracts in advance can be removed out the radical sign computing from, so subtract in advance for incoherent that hysteresis amplitude method calculated amount is little, efficient is high.Yet,, thereby adopt the incoherent after-power Discr. that subtracts in advance can produce certain phase demodulation error because auto-correlation amplitude curve and powertrace do not coincide.As long as to subtract hysteresis amplitude Discr. in advance the same also two pairs of correlators with incoherent, and error performance is also similar.

(c) patibhaga-nimitta is done long-pending power Discr., this code phase Discr. no longer adopts the non-coherent integration result, but the direct coherent integration value of utilizing on leading, instant and three branch roads that lag behind, so it needs three pairs of correlators at least, the needed calculated amount of relevant dot product power method that is adopted is all lower than preceding two kinds of incoherent type Discr.s, for the relevant spacing of 0.5 code element, in ± 0.5 code element error originated from input scope, the real error output of its approximate generation.

(d) relevant dot product power Discr., this Discr. is a kind of special case that patibhaga-nimitta is done long-pending power Discr., promptly when the carrier wave ring adopts the form of phaselocked loop and phaselocked loop to be operated in stable state again, all power of received signal concentrate in the same way on the branch road all, and the signal on the quadrature branch approaches zero.Method that this Discr. adopted is calculated the simplest, yet the power concentration that it requires signal is on branch road in the same way.If carrier wave adopts FLL, if perhaps the phaselocked loop as the carrier wave ring does not also reach stable state, a part of power of received signal can run off in quadrature branch so, and the signal power of exporting on this feasible branch road does not in the same way reach maximum, thereby causes this Discr. performance decrease.

When carrier is done motion in the good environment of signal, traditional phase detector can both be finished phase discrimination function, but under multipath disturbs, code phase is followed the tracks of and has been subjected to having a strong impact on of undesired signal, these code phase Discr.s can not identify code phase error in real time, and then track loop will enter out-of-lock condition.Therefore, many scholars have proposed a series of anti-multipath algorithm of interference based on the code phase Discr., mainly contain multipath separation method and narrow correlation technique method based on maximal possibility estimation.Yet, poor based on the noise robustness of the multipath separation method of maximal possibility estimation, promptly can estimate very exactly the amplitude and the phase place of multipath undesired signal under the situation of noise not having, and the accuracy of its estimation descends greatly when having noise.There is its intrinsic limitation in narrow correlation technique: because related interval can not be 0, therefore adopting narrow correlation technique is impossible eliminate fully by multipath to disturb the C/A code tracking error of introducing; In addition, the receiver signal passage is under the condition of infinite bandwidth, reduce related interval d and can constantly reduce multipath error, and this condition obviously can't satisfy in actual applications.

Summary of the invention

The present invention is directed under the multipath signal disturbed condition, traditional code phase Discr. can not effectively suppress the interference of multipath, its phase demodulation error precision that improves algorithm is also not ideal enough, bad in actual applications realization has proposed a kind of based on the dark combined tracking loop of GPS/INS Gauss's code phase Discr. and method for designing thereof.

It is a kind of based on the dark combined tracking loop of GPS/INS Gauss code phase Discr. that the present invention proposes, the improvement that traditional receiver DLL loop has been carried out, on the basis of conventional code phase-shift discriminator, increased INS code phase Discr. module and Gauss's code phase Discr. module, the information source that specifically makes up Gauss's code phase Discr. of the present invention comprises local carrier generator, local C/A code generator, correlator, frequency mixer, integration totalizer, GPS receiver tracking loop circuit code phase Discr., Gaussian function generator and INS code phase Discr..The local carrier generator produces the carrier wave reproducing signals of 90 ° of phasic differences mutually on branch road in the same way and quadrature branch, local code C/A code generator is in that branch road and quadrature branch produce respectively in advance in the same way, instant and hysteresis replica code, intermediate-freuqncy signal respectively simultaneously by a frequency mixer and local carrier generator in the same way with the carrier wave reproducing signals multiplicative mixing of quadrature two branch roads generation, the mixing results that obtains again with local code C/A code generator branch road and quadrature branch in the same way produce respectively leading, immediately, the hysteresis replica code carries out the related operation of time, and the signal that obtains added up by an integration totalizer respectively, obtain the relevant output I of the leading branch road of in-phase branch _E, I _PAnd I _L, and the relevant output Q that reaches the hysteresis branch road in advance, immediately of quadrature branch _E, Q _PAnd Q _LThe relevant output I of the instant branch road of in-phase branch _PRelevant output Q with the instant branch road of quadrature branch _PIntroduce in the Gaussian function generator, the code phase information that the Gaussian function generator utilizes DLL to introduce is again according to relevant information μ _INS, Make up synchronous advanced code phase function G _EWith hysteresis code phase function G _L, utilize advanced code phase function G _EWith hysteresis code phase function G _LMake up INS code phase Discr., upgrade, obtain the square error MSE of GPS receiver tracking loop circuit code phase Discr. by loop _GPSSquare error MSE with INS code phase Discr. _INS, two square errors are adjusted the output of GPS receiver tracking loop circuit code phase Discr. and INS code phase Discr. as weight coefficient, make up Gauss's code phase Discr. D _GAUSS

The above-mentioned a kind of method of design that the present invention proposes based on the dark combined tracking loop of GPS/INS Gauss code phase Discr., concrete steps are as follows:

Step 1: at first analyze the influence of multipath interference,, obtain the relevant output I of the leading branch road on the in-phase branch then according to code tracking loop principle of work to the code tracking loop _E, instant branch road relevant output I _P, the hysteresis branch road relevant output I _L, the relevant output Q of the leading branch road on the quadrature branch _E, instant branch road relevant output Q _PAnd the relevant output Q of hysteresis branch road _L

In the GPS navigation system, under the situation of not considering modulating data and noise, the signal model S (t) that receiver receives is

$S\left(t\right)=A\·x[(1+\mathrm{\ζ})t-{\mathrm{\τ}}_0]\cos [({\mathrm{\ω}}_c+{\mathrm{\ω}}_d)t+{\mathrm{\θ}}_0]+\underset{i=1}{\overset{M}{\mathrm{\Σ}}}{\mathrm{\α}}_i\·x[(1+\mathrm{\ζ})t-{\mathrm{\τ}}_i]\cos [({\mathrm{\ω}}_c+{\mathrm{\ω}}_d)t+{\mathrm{\θ}}_i]$

Wherein, A is the amplitude of direct signal; X (t) is a t C/A sign indicating number constantly, and ζ is the ratio of Doppler shift and carrier frequency, i.e. ζ=ω _d/ ω _c, ω _cBe carrier frequency, ω _dBe Doppler shift, τ ₀The C/A sign indicating number time delay of expression direct signal, α _i=b _iA is the amplitude of i bar multipath signal, b _iIt is i bar multipath signal and the amplitude ratio of direct signal; θ ₀And θ _iBe respectively the carrier phase deviation of direct signal and i bar multipath signal, M represents the bar number of multipath signal.

Step 2: choose GPS receiver tracking loop circuit code phase Discr. DGPS

The present invention adopts the incoherent after-power type code phase Discr. D that subtracts in advance _GPSAs treating improved initial code phase positions Discr., its expression formula is:

D _GPS＝(I _E ²+Q _E ²)-(I _L ²+Q _L ²)

The relevant output I of the leading branch road on the in-phase branch that step 1 is obtained _E, the hysteresis branch road relevant output I _L, the relevant output Q of the leading branch road on the quadrature branch _E, the hysteresis branch road relevant output Q _LSubstitution initial code phase positions Discr. D _GPSIn, obtain the D under the multipath interference _GPSPhase demodulation function: D _GPS=D _n+ D _Err, wherein, D _nIncoherent phase demodulation output when not existing multipath to disturb, D _ErrDisturb the incoherent phase demodulation output that causes for multipath.

Obtain the D under the multipath interference _GPSBehind the phase demodulation function, it is carried out normalized.

Step 3: utilize the real-time code phase error of GPS receiver, make up INS advanced code phase function G _EWith hysteresis code phase function G _L

Measured Gaussian function:

$G\left(t\right)=\frac{1}{\sqrt{2\mathrm{\π}{\mathrm{\σ}}^2}}\exp [-\frac{{(t-\mathrm{\μ})}^2}{{2\mathrm{\σ}}^2}]$

Make up synchronous Gaussian function generator, the Gaussian function G (γ that this Gaussian function generator is adopted earlier in conjunction with the output information of INS with from GPS receiver DLL information again _GPS) as follows:

$G\left({\mathrm{\γ}}_{\mathrm{GPS}}\right)=\frac{1}{\sqrt{{2\mathrm{\π\σ}}_{\mathrm{INS}}^2}}\exp [-\frac{{({\mathrm{\γ}}_{\mathrm{GPS}}-{\mathrm{\μ}}_{\mathrm{INS}})}^2}{{2\mathrm{\σ}}_{\mathrm{INS}}^2}]$

Wherein, γ _GPSFor deriving from the code phase error that receiver DLL produces in real time,

Be local code phase delay; τ ₀The C/A sign indicating number time delay of expression direct signal, μ _INSBe the code phase error of INS system estimation,

Be the code phase square error of INS system estimation,, choose here for synchronous with gps system work

Consistent with the correlator interval d of DLL.

There is under the situation of i bar multipath signal interference the leading Gaussian function G that the Gaussian function generator produces _EWith hysteresis Gaussian function G _LBe respectively::

$G_E=G({\mathrm{\γ}}_{\mathrm{GPS}}+d)+G({\mathrm{\γ}}_{\mathrm{GPS}}+d-\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\left({\mathrm{\Δ\τ}}_i\right))$

$=\frac{1}{\sqrt{{2\mathrm{\π\σ}}_{\mathrm{INS}}^2}}\left\{\exp \right[-\frac{{({\mathrm{\γ}}_{\mathrm{GPS}}+d-{\mathrm{\μ}}_{\mathrm{INS}})}^2}{{2\mathrm{\σ}}_{\mathrm{INS}}^2}]+\exp [-\frac{{({\mathrm{\γ}}_{\mathrm{GPS}}+d-{\mathrm{\μ}}_{\mathrm{INS}}-\underset{i-1}{\overset{n}{\mathrm{\Σ}}}\left({\mathrm{\Δ\τ}}_i\right))}^2}{{2\mathrm{\σ}}_{\mathrm{INS}}^2}\left]\right\}$

$G_L=G({\mathrm{\γ}}_{\mathrm{GPS}}-d)+G({\mathrm{\γ}}_{\mathrm{GPS}}-d-\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\left({\mathrm{\Δ\τ}}_i\right))$

$=\frac{1}{\sqrt{{2\mathrm{\π\σ}}_{\mathrm{INS}}^2}}\left\{\exp \right[-\frac{{({\mathrm{\γ}}_{\mathrm{GPS}}-d-{\mathrm{\μ}}_{\mathrm{INS}})}^2}{{2\mathrm{\σ}}_{\mathrm{INS}}^2}]+\exp [-\frac{{({\mathrm{\γ}}_{\mathrm{GPS}}-d-{\mathrm{\μ}}_{\mathrm{INS}}-\underset{i=1}{\overset{n}{\mathrm{\Σ}}}\left({\mathrm{\Δ\τ}}_i\right))}^2}{{2\mathrm{\σ}}_{\mathrm{INS}}^2}\left]\right\}$

Wherein, Δ τ _iBe the C/A sign indicating number time delay of i bar multipath signal with respect to direct signal, Δ τ _i=τ _i-τ ₀, τ ₀C/A sign indicating number time delay for direct signal.If when having only a multipath signal, n gets 1,

τ ₁C/A sign indicating number time delay for this multipath signal.If there are two multipath signals, n gets 2,

Δ τ ₂=τ ₂-τ ₀, τ ₂C/A sign indicating number time delay for the second multipath signal.In like manner, can calculate G under many multipath signals _EAnd G _L

Step 4: utilize advanced code phase function G _EWith hysteresis code phase function G _L, structure INS code phase Discr. D _INS:

D _INS＝G _E ²-G _L ²

With the advanced code phase function G that obtains in the step 3 _EWith hysteresis code phase function G _LSubstitution obtains the D under the multipath interference _INSThe phase demodulation function be:

$D_{\mathrm{INS}}={G_E}^2-{{\mathrm{<figure-callout\; id="2"\; label="G\; L"\; filenames="HDA0000139796580000022.png,HDA0000139796580000023.png"\; state="\{\{state\}\}">G</figure-callout>}}_L}^2$

$\&ap;B\left\{\exp \right[-{({\mathrm{\&gamma;}}_{\mathrm{GPS}}+d-{\mathrm{\&mu;}}_{\mathrm{INS}})}^2/d]-\exp [-{({\mathrm{\&gamma;}}_{\mathrm{GPS}}-d-{\mathrm{\&mu;}}_{\mathrm{INS}})}^2/d\left]\right\}$

$+B\left\{\exp \right[-2({\mathrm{\&gamma;}}_{\mathrm{GPS}}+d-{\mathrm{\&mu;}}_{\mathrm{INS}}){\mathrm{\&Delta;\&tau;}}_1^2/d]-\exp [-2({\mathrm{\&gamma;}}_{\mathrm{GPS}}-d-{\mathrm{\&mu;}}_{\mathrm{INS}}){\mathrm{\&Delta;\&tau;}}_1^2/d\left]\right\}$

$+2B\left\{\exp \right[-2{({\mathrm{\&gamma;}}_{\mathrm{GPS}}+d-{\mathrm{\&mu;}}_{\mathrm{INS}})}^2+{\mathrm{\&Delta;\&tau;}}_1^2/\left(2d\right)]-\exp [-2{({\mathrm{\&gamma;}}_{\mathrm{GPS}}-d-{\mathrm{\&mu;}}_{\mathrm{INS}})}^2+{\mathrm{\&Delta;\&tau;}}_1^2/\left(2d\right)\left]\right\}$

Wherein, B=1/ (2 π d).

With the D under the multipath interference that obtains _INSThe phase demodulation function carry out normalized.

Step 5: determine GPS receiver tracking loop circuit code phase Discr. D _GPSSquare error MSE _GPSWith INS code phase Discr. D _INSSquare error MSE _INS, specifically:

Setting the loop update times is nf, and the renewal of loop each time for wherein all obtains corresponding relevant output I _E, Q _E, I _L, Q _L, and G _E, G _L, so code phase Discr. D _GPSWith INS code phase Discr. D _INSUpgrade nf time, determine their average then Then can obtain MSE _GPSAnd MSE _INS, their expression formula is as follows:

${\mathrm{MSE}}_{\mathrm{GPS}}=\sqrt{\left[\underset{i=1}{\overset{\mathrm{nf}}{\mathrm{\&Sigma;}}}{(D_{\mathrm{GPS}}\left(i\right)-{\stackrel{\&OverBar;}{D}}_{\mathrm{GPS}})}^2\right]/\mathrm{nf}}$

${\mathrm{MSE}}_{\mathrm{INS}}=\sqrt{\left[\underset{i=1}{\overset{\mathrm{nf}}{\mathrm{\&Sigma;}}}{(D_{\mathrm{INS}}\left(i\right)-{\stackrel{\&OverBar;}{D}}_{\mathrm{INS}})}^2\right]/\mathrm{nf}}$

Step 6: make up Gauss's code phase Discr. D _GAUSS:

D _GAUSS＝(D _GPS/MSE _GPS)+(D _INS/MSE _INS)

Carry out after the normalization be:

$D_{\mathrm{GAUSS}}=\frac{{\mathrm{MSE}}_{\mathrm{INS}}{D}_{\mathrm{GPS}}+{\mathrm{MSE}}_{\mathrm{GPS}}{D}_{\mathrm{INS}}}{{\mathrm{MSE}}_{\mathrm{GPS}}+{\mathrm{MSE}}_{\mathrm{INS}}}$

The D that normalization obtains _GAUSSGauss's code phase Discr. that will make up exactly.

Advantage of the present invention and good effect are:

(1) the INS system introduces the instant branch road code phase information of GPS receiver DLL in the Gaussian function generator, make up INS code phase Discr., again with DLL in the code phase Discr. superpose by square error, be combined into Gauss's code phase Discr., changed the structure of traditional GPS receiver DLL, simulating, verifying under multipath signal disturbs, this Gauss's code phase Discr. can effectively improve the phase demodulation output characteristics really, reduce the code phase tracking error, also verified simultaneously the feasibility of design Gauss code phase Discr. method, provide some guided bone effects for further inquiring into the dark combined tracking loop design of GPS/INS.

(2) receiver is under multipath signal disturbs, set up the INS code phase Discr. of synchronous GPS operation of receiver according to inertial navigation information, come auxiliary receiver work then, the Gaussian function that utilizes the INS system to produce, improve C/A sign indicating number autocorrelation function peak-peak, and make the slope slope of both sides, autocorrelation function main peak top bigger, can effectively improve the precision of measuring the main peak apical position, improve the phase demodulation output characteristics of Discr. under multipath disturbs, reduce the code phase tracking error, thereby make under identical carrier-to-noise ratio condition, detection probability increases, help carrying out reacquisition after the signal losing lock, can effectively improve the efficient of signal reacquisition.

Description of drawings

Fig. 1 (a) is the structural drawing that makes up conventional code phase-shift discriminator information needed source;

Fig. 1 (b) is the structural drawing that makes up Gauss's code phase Discr. information needed of the present invention source;

Fig. 2 is leading, the hysteresis code phase analogous diagram that is used to make up INS code phase Discr.;

Fig. 3 (a) is the C/A sign indicating number autocorrelation function curve of independent GPS and C/A sign indicating number autocorrelation function curve that INS estimates;

C/A sign indicating number autocorrelation function curve after Fig. 3 (b) stack;

Fig. 4 (a) is under two multipath signals disturb, D _GPSEliminate the phase demodulation curve after multipath disturbs;

Fig. 4 (b) is under two multipath signals disturb, D _GAUSSEliminate the phase demodulation curve after multipath disturbs;

Fig. 5 (a) is along with loop upgrades, D _GPSAnd D _GAUSSThe code phase error analogous diagram of output;

Fig. 5 (b) is along with loop upgrades, D _GPSAnd D _GAUSSThe code phase error analogous diagram of output accumulation;

Fig. 6 is the process flow diagram that makes up Gauss's code phase Discr..

Embodiment

The present invention is further elaborated below in conjunction with accompanying drawing.

The conventional code phase-shift discriminator does not use the instant branch road code phase information in the DLL structure, and in the present invention, the instant branch road code phase information of DLL is as one of source that makes up INS code phase Discr. module information needed.The instant branch road code phase information of GPS receiver DLL is incorporated in the Gaussian function generator of INS system, in conjunction with the input of INS system, makes up INS code phase Discr..Continual renovation by loop, calculate the square error of conventional code phase-shift discriminator output data and the square error of INS code phase Discr. output data, with the weight coefficient of square error as measurement conventional code phase-shift discriminator and INS code phase Discr. precision, thereby be combined into Gauss's code phase Discr., it can increase the auto-correlation peak value of C/A sign indicating number, under multipath disturbs, improve the phase demodulation output performance, effectively reduce the code phase tracking error.

As Fig. 1 (a) is to make up the incoherent information source structural drawing (list of references 1: Yu Hailiang that subtracts after-power type code phase Discr. in advance of tradition, based on the auxiliary GPS receiver of INS and the research (D) of tracking technique, master thesis, Changsha: the National University of Defense technology, 2007,31-34), make up its needed information source and be mainly local carrier generator 1, frequency mixer 2, local C/A code generator 3, correlator 4, integration totalizer 5 and GPS receiver tracking loop circuit code phase Discr. 6.Fig. 1 (b) is improved on the basis of Fig. 1 (a), it is the structural drawing that Gauss's code phase Discr. of proposing of the present invention makes up, with respect to Fig. 1 (a), making up Gauss's code phase Discr. of the present invention has increased information source: Gaussian function generator 7 and INS code phase Discr. D _INS8, GPS receiver tracking loop circuit code phase Discr. D _GPS6 and INS code phase Discr. D _INS8 have further made up Gauss's code phase Discr. D of the present invention _GAUSS9.In Fig. 1 (b), local carrier generator 1 produces the carrier wave reproducing signals of 90 ° of phasic differences mutually on branch road in the same way and quadrature branch, local C/A code generator 3 produces respectively in advance in branch road and quadrature branch in the same way, immediately, the hysteresis replica code.Intermediate-freuqncy signal at first by frequency mixer 2 and local carrier generator 1 in the carrier wave reproducing signals multiplicative mixing that produces with quadrature two branch roads in the same way, realize that carrier wave peels off; Leading, instant, the hysteresis replica code carries out the some time respectively by a correlator 4 related operation that mixing results i, q produce in branch road and quadrature branch in the same way with local code C/A code generator 3 again generate i at branch road in the same way _E, i _PAnd i _LSignal generates q in quadrature branch _E, q _PAnd q _LSignal, at this moment, the C/A sign indicating number in the input signal is stripped from.In order further to improve signal to noise ratio (S/N ratio), the i that will obtain through correlator 4 _E, i _P, i _L, q _E, q _PAnd q _LAfter signal carries out the integration accumulation by integration totalizer 5 respectively, become the relevant output I that reaches the hysteresis branch road in advance, immediately of in-phase branch respectively _E, I _PAnd I _L, and the relevant output Q that reaches the hysteresis branch road in advance, immediately of quadrature branch _E, Q _PAnd Q _LWherein, I _E, I _L, Q _EAnd Q _LBe used for making up traditional incoherent after-power type code phase Discr. that subtracts in advance, shown in Fig. 1 (a).Relevant output I _PAnd Q _PBe introduced in the Gaussian function generator 7, the code phase information that Gaussian function generator 7 utilizes DLL to introduce is again according to relevant information μ _INS,

Make up synchronous advanced code phase function G _EWith hysteresis code phase function G _L, so make up INS code phase Discr. 8 with them.Upgrade by loop, obtain GPS receiver tracking loop circuit code phase Discr. D respectively _GPS6 square error MSE _GPSWith INS code phase Discr. D _INS8 square error MSE _INS, two square errors are adjusted GPS receiver tracking loop circuit code phase Discr. D as weight coefficient _GPS6 and INS code phase Discr. D _INS8 output, thus make up high-precision Gauss's code phase Discr. D _GAUSS9.

What the present invention considered is the signal trace link, and temporary transient putative signal is successfully caught, and some major parameters of constructing Gauss's code phase Discr. of the present invention are as follows: the local code frequency f _LO=1.023MHz, the intermediate frequency carrier frequency f _IF=1575.42MHz, sample frequency f _s=5MHz, carrier loop bandwidth 16Hz, sign indicating number loop bandwidth 8Hz, damping factor ξ=0.707, sign indicating number loop gain K _Code=1, carrier wave ring gain K _Carr=0.5 π, loop update times nf=400, correlator spacing d=0.5 chip.The C/A code phase time delay of direct signal and multipath signal is 0 and 0.75 chip, and amplitude is respectively 1 and 0.65.

The present invention makes up the method for designing based on the dark combined tracking loop of GPS/INS Gauss code phase Discr. shown in Fig. 1 (b), and as shown in Figure 6, concrete steps are:

Step 1: at first analyze the influence of multipath interference, obtain the relevant output I of the leading branch road on the in-phase branch to the code tracking loop _E, instant branch road relevant output I _P, the hysteresis branch road relevant output I _L, the relevant output Q of the leading branch road on the quadrature branch _E, instant branch road relevant output Q _PAnd the relevant output Q of hysteresis branch road _L

In the GPS navigation system, under the situation of not considering modulating data and noise, the signal model S (t) that receiver receives is

$S\left(t\right)=A\&CenterDot;x[(1+\mathrm{\&zeta;})t-{\mathrm{\&tau;}}_0]\cos [({\mathrm{\&omega;}}_c+{\mathrm{\&omega;}}_d)t+{\mathrm{\&theta;}}_0]+\underset{i=1}{\overset{M}{\mathrm{\&Sigma;}}}{\mathrm{\&alpha;}}_i\&CenterDot;x[(1+\mathrm{\&zeta;})t-{\mathrm{\&tau;}}_i]\cos [({\mathrm{\&omega;}}_c+{\mathrm{\&omega;}}_d)t+{\mathrm{\&theta;}}_i]---\left(1\right)$

Wherein, A is the amplitude of direct signal; X (t) is a t C/A sign indicating number constantly, and ζ is the ratio of Doppler shift and carrier frequency, i.e. ζ=ω _d/ ω _c, ω _cBe carrier frequency, ω _dBe Doppler shift, τ ₀The C/A sign indicating number time delay of expression direct signal, α _i=b _iA is the amplitude of i bar multipath signal, b _iIt is i bar multipath signal and the amplitude ratio of direct signal; τ _iThe C/A sign indicating number time delay of representing i bar multipath signal, θ ₀And θ _iBe respectively the carrier phase deviation of direct signal and i bar multipath signal, M represents the bar number of multipath signal.

Consider under the situation of a multipath signal, this moment M=i=1, the signal that receiver receives can get through down coversion and Phase Tracking:

S(t)＝A·x[(1+ζ)t-τ ₀]cos(ψ)+b ₁A·x[(1+ζ)t-τ ₀-Δτ ₁]cos(ψ+β ₁) (2)

Wherein, the carrier phase deviation of estimation

Be the carrier phase of local estimated signal, Δ τ ₁=τ ₁-τ ₀Be the C/A sign indicating number time delay of a multipath signal with respect to direct signal, τ ₁The C/A sign indicating number time delay of a multipath signal of expression, β ₁=θ ₁-θ ₀Be the carrier phase deviation of multipath signal with respect to direct signal, θ ₁The carrier phase deviation of a multipath signal of expression.

If local C/A sign indicating number sequence is

Be local code phase delay, carrier is ζ＜＜1 when non-high dynamic motion, temporarily ignores the influence of Doppler shift, and local C/A sign indicating number is

With the input signal S (t) carry out relevant:

(3)

In the following formula,

Be direct signal C/A code phase delay evaluated error, the autocorrelation function R (γ) of C/A sign indicating number sequence can be approximated to be:

$R\left(\mathrm{\&gamma;}\right)=\left\{\begin{array}{cc}{T}_c-\left|\mathrm{\&gamma;}\right|& \left|\mathrm{\&gamma;}\right|\&le;{\mathrm{<figure-callout\; id="0"\; label="T\; c"\; filenames="HDA0000139796580000021.png,HDA0000139796580000022.png"\; state="\{\{state\}\}">T</figure-callout>}}_c\\ 0& \left|\mathrm{\&gamma;}\right|>T_c\end{array}\right.---\left(4\right)$

In the following formula, T _cBe the time that chip continued of C/A sign indicating number.Be that direct signal or multipath signal all comprise carrier wave, C/A sign indicating number and three kinds of information of data, one of them C/A sign indicating number comprises 1023 chips, and time span is 1 millisecond, so T in direct signal and the multipath signal _CBeing the same, all is 1/1023 millisecond on the time.

By code tracking loop principle of work, getting the correlator spacing is d, the relevant output I of the leading branch road of in-phase branch _E, instant branch road relevant output I _PAnd the relevant output I of hysteresis branch road _LBe respectively:

$I_E=\frac{A}{\sqrt{2}}[\cos \left(\mathrm{\&psi;}\right)R(\mathrm{\&gamma;}+d)+{\mathrm{<figure-callout\; id="1"\; label="b"\; filenames="HDA0000139796580000022.png,HDA0000139796580000023.png"\; state="\{\{state\}\}">b</figure-callout>}}_1\cos (\mathrm{\&psi;}+{\mathrm{\&beta;}}_1)R(\mathrm{\&gamma;}+d-{\mathrm{\&Delta;\&tau;}}_1)]---\left(5\right)$

$I_P=\frac{A}{\sqrt{2}}[\cos \left(\mathrm{\&psi;}\right)R\left(\mathrm{\&gamma;}\right)+{\mathrm{<figure-callout\; id="1"\; label="b"\; filenames="HDA0000139796580000022.png,HDA0000139796580000023.png"\; state="\{\{state\}\}">b</figure-callout>}}_1\cos (\mathrm{\&psi;}+{\mathrm{\&beta;}}_1)R\left(\mathrm{\&gamma;}{-\mathrm{\&Delta;\&tau;}}_1\right)]---\left(6\right)$

$I_L=\frac{A}{\sqrt{2}}[\cos \left(\mathrm{\&psi;}\right)R(\mathrm{\&gamma;}-d)+{\mathrm{<figure-callout\; id="1"\; label="b"\; filenames="HDA0000139796580000022.png,HDA0000139796580000023.png"\; state="\{\{state\}\}">b</figure-callout>}}_1\cos (\mathrm{\&psi;}+{\mathrm{\&beta;}}_1)R(\mathrm{\&gamma;}-d-{\mathrm{\&Delta;\&tau;}}_1)]---\left(7\right)$

In advance, immediately the relevant output that reaches the hysteresis branch road that in like manner can calculate quadrature branch is respectively Q _E, Q _P, Q _L:

$Q_E=\frac{A}{\sqrt{2}}[\sin \left(\mathrm{\&psi;}\right)R(\mathrm{\&gamma;}+d)+{\mathrm{<figure-callout\; id="1"\; label="b"\; filenames="HDA0000139796580000022.png,HDA0000139796580000023.png"\; state="\{\{state\}\}">b</figure-callout>}}_1\sin \left(\mathrm{\&psi;}{+\mathrm{\&beta;}}_1\right)R(\mathrm{\&gamma;}+d-{\mathrm{\&Delta;\&tau;}}_1)]---\left(8\right)$

$Q_P=\frac{A}{\sqrt{2}}[\sin \left(\mathrm{\&psi;}\right)R\left(\mathrm{\&gamma;}\right)+{\mathrm{<figure-callout\; id="1"\; label="b"\; filenames="HDA0000139796580000022.png,HDA0000139796580000023.png"\; state="\{\{state\}\}">b</figure-callout>}}_1\sin (\mathrm{\&psi;}+{\mathrm{\&beta;}}_1)R\left(\mathrm{\&gamma;}{-\mathrm{\&Delta;\&tau;}}_1\right)]---\left(9\right)$

$Q_L=\frac{A}{\sqrt{2}}[\sin \left(\mathrm{\&psi;}\right)R(\mathrm{\&gamma;}-d)+{\mathrm{<figure-callout\; id="1"\; label="b"\; filenames="HDA0000139796580000022.png,HDA0000139796580000023.png"\; state="\{\{state\}\}">b</figure-callout>}}_1\sin \left(\mathrm{\&psi;}{+\mathrm{\&beta;}}_1\right)R(\mathrm{\&gamma;}-d-{\mathrm{\&Delta;\&tau;}}_1)]---\left(10\right)$

Step 2: choose GPS receiver tracking loop circuit code phase Discr. D _GPS

The present invention adopts the incoherent after-power type code phase Discr. D that subtracts in advance _GPSAs treating improved initial code phase positions Discr., its expression formula is:

D _GPS＝(I _E ²+Q _E ²)-(I _L ²+Q _L ²) (11)

After the relevant output substitution formula (11) that step 1 is obtained, obtain the D of multipath under disturbing _GPSThe phase demodulation function, employing formula (12) is carried out normalized:

$D_{\mathrm{GPS}}=\frac{({{\mathrm{<figure-callout\; id="2"\; label="I\; E"\; filenames="HDA0000139796580000022.png,HDA0000139796580000023.png"\; state="\{\{state\}\}">I</figure-callout>}}_E}^2+{Q_E}^2)-({{\mathrm{<figure-callout\; id="2"\; label="I\; L"\; filenames="HDA0000139796580000022.png,HDA0000139796580000023.png"\; state="\{\{state\}\}">I</figure-callout>}}_L}^2+{Q_L}^2)}{({{\mathrm{<figure-callout\; id="2"\; label="I\; E"\; filenames="HDA0000139796580000022.png,HDA0000139796580000023.png"\; state="\{\{state\}\}">I</figure-callout>}}_E}^2+{Q_E}^2)+({{\mathrm{<figure-callout\; id="2"\; label="I\; L"\; filenames="HDA0000139796580000022.png,HDA0000139796580000023.png"\; state="\{\{state\}\}">I</figure-callout>}}_L}^2+{Q_L}^2)}---\left(12\right)$

Because its this code phase Discr. has utilized in the same way and quadrature branch simultaneously, performance is independent of the carrier phase locking ring, the dynamic range that is suitable for is bigger, can handle the signal of lower signal to noise ratio (S/N ratio), and its calculated amount is less, the computing velocity influence of the auxiliary back of adding inertia information is little, and inertia information can help, and its auto-correlation amplitude curve and powertrace are approaching to be overlapped.Bring formula (5) (7) (8) and (10) into (11) and can get the D of multipath under disturbing _GPSThe phase demodulation function is:

$D_{\mathrm{GPS}}=\frac{A^2}{2}[R^2(\mathrm{\&gamma;}+d/2)-R^2(\mathrm{\&gamma;}-d/2)]+\frac{A^2}{2}\left\{{\mathrm{<figure-callout\; id="1"\; label="b"\; filenames="HDA0000139796580000022.png,HDA0000139796580000023.png"\; state="\{\{state\}\}">b</figure-callout>}}_1^2\right[R^2(\mathrm{\&gamma;}+d/2-\mathrm{\&Delta;\&tau;})-R^2(\mathrm{\&gamma;}-d/2-{\mathrm{\&Delta;\&tau;}}_1)]$

$+2{\mathrm{<figure-callout\; id="1"\; label="b"\; filenames="HDA0000139796580000022.png,HDA0000139796580000023.png"\; state="\{\{state\}\}">b</figure-callout>}}_1\cos \left({\mathrm{\&beta;}}_1\right)[R(\mathrm{\&gamma;}+d/2)R(\mathrm{\&gamma;}+d/2-{\mathrm{\&Delta;\&tau;}}_1)-R(\mathrm{\&gamma;}-d/2)R(\mathrm{\&gamma;}-d/2-{\mathrm{\&Delta;\&tau;}}_1)]\}---\left(13\right)$

$=D_n+D_{\mathrm{err}}$

In the formula (13),

D _Err=D _GPS-D _n, D _nIncoherent phase demodulation output when not existing multipath to disturb; D _ErrDisturb the incoherent phase demodulation output that causes for multipath.

Step 3: the code phase information that Gaussian function generator 7 utilizes DLL to introduce, again according to relevant information μ _INS,

Make up synchronous advanced code phase function G _EWith hysteresis code phase function G _L

Measured Gaussian function

$G\left(t\right)=\frac{1}{\sqrt{{2\mathrm{\&pi;\&sigma;}}^2}}\exp [-\frac{{(t-\mathrm{\&mu;})}^2}{{2\mathrm{\&sigma;}}^2}]---\left(14\right)$

Again in conjunction with the output information of INS with to make up synchronous Gaussian function earlier from GPS receiver DLL information as follows:

$G\left({\mathrm{\&gamma;}}_{\mathrm{GPS}}\right)=\frac{1}{\sqrt{{2\mathrm{\&pi;\&sigma;}}_{\mathrm{<figure-callout\; id="2"\; label="INS"\; filenames="HDA0000139796580000022.png,HDA0000139796580000023.png"\; state="\{\{state\}\}">INS</figure-callout>}}^2}}\exp [-\frac{{({\mathrm{\&gamma;}}_{\mathrm{GPS}}-{\mathrm{\&mu;}}_{\mathrm{INS}})}^2}{{2\mathrm{\&sigma;}}_{\mathrm{INS}}^2}]---\left(15\right)$

Wherein, γ _GPSDerive from the code phase error that receiver DLL produces in real time,

Be local code phase delay; τ ₀The C/A sign indicating number time delay of expression direct signal, μ _INSBe the code phase error of INS system estimation,

Be the code phase square error of INS system estimation,, choose here for synchronous with gps system work

Consistent with the code phase device interval d of DLL.

In order to make the INS system estimation go out code phase error, similar with DLL code generator principle of work, under the situation that multipath signal disturbs, the Gaussian function generator also needs to produce leading Gaussian function G _E, hysteresis Gaussian function G _L:

$G_E=G({\mathrm{\&gamma;}}_{\mathrm{GPS}}+d)+G({\mathrm{\&gamma;}}_{\mathrm{GPS}}+d-\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}\left({\mathrm{\&Delta;\&tau;}}_i\right))$

$=\frac{1}{\sqrt{{2\mathrm{\&pi;\&sigma;}}_{\mathrm{INS}}^2}}\left\{\exp \right[-\frac{{({\mathrm{\&gamma;}}_{\mathrm{GPS}}+d-{\mathrm{\&mu;}}_{\mathrm{INS}})}^2}{{2\mathrm{\&sigma;}}_{\mathrm{INS}}^2}]+\exp [-\frac{{({\mathrm{\&gamma;}}_{\mathrm{GPS}}+d-{\mathrm{\&mu;}}_{\mathrm{INS}}-\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}\left({\mathrm{\&Delta;\&tau;}}_i\right))}^2}{{2\mathrm{\&sigma;}}_{\mathrm{INS}}^2}\left]\right\}---\left(16\right)$

$G_L=G({\mathrm{\&gamma;}}_{\mathrm{GPS}}-d)+G({\mathrm{\&gamma;}}_{\mathrm{GPS}}-d-\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}\left({\mathrm{\&Delta;\&tau;}}_i\right))$

$=\frac{1}{\sqrt{{2\mathrm{\&pi;\&sigma;}}_{\mathrm{INS}}^2}}\left\{\exp \right[-\frac{{({\mathrm{\&gamma;}}_{\mathrm{GPS}}-d-{\mathrm{\&mu;}}_{\mathrm{INS}})}^2}{{2\mathrm{\&sigma;}}_{\mathrm{INS}}^2}]+\exp [-\frac{{({\mathrm{\&gamma;}}_{\mathrm{GPS}}-d-{\mathrm{\&mu;}}_{\mathrm{INS}}-\underset{i=1}{\overset{n}{\mathrm{\&Sigma;}}}\left({\mathrm{\&Delta;\&tau;}}_i\right))}^2}{{2\mathrm{\&sigma;}}_{\mathrm{INS}}^2}\left]\right\}---\left(17\right)$

In formula (16) and (17), Δ τ _iBe i bar multipath signal with respect to the C/A sign indicating number time delay of direct signal if.If when having only a multipath signal, the n in formula (16) and (17) gets 1,

τ ₁Be the C/A sign indicating number time delay of this multipath signal, τ ₀C/A sign indicating number time delay for direct signal.If there are two multipath signals, n gets 2,

Δ τ ₂=τ ₂-τ ₀, τ ₂C/A sign indicating number time delay for the second multipath signal.In like manner, can calculate G under many multipath signals _EAnd G _L

Step 4: utilize advanced code phase function G _EWith hysteresis code phase function G _L, structure INS code phase Discr. D _INS

INS utilizes GPS receiver DLL information to set up out the code phase Discr. D of INS system _INS, its expression formula is:

D _INS＝G _E ²-G _L ² (18)

The advanced code phase function G that step 3 is obtained _EWith hysteresis code phase function G _LBring formula (18) into, obtain the D under the multipath interference _INSThe phase demodulation function, the D under the multipath that obtains disturbed _INSThe phase demodulation function adopt formula (19) to carry out normalized:

D _INS＝(G _E ²-G _L ²)/(G _E ²+G _L ²) (19)

Bring formula (16) (17) into formula (18), obtain multipath and disturb D down _INSThe phase demodulation function be:

$D_{\mathrm{INS}}={G_E}^2-{{\mathrm{<figure-callout\; id="2"\; label="G\; L"\; filenames="HDA0000139796580000022.png,HDA0000139796580000023.png"\; state="\{\{state\}\}">G</figure-callout>}}_L}^2$

$\&ap;B\left\{\exp \right[-{({\mathrm{\&gamma;}}_{\mathrm{GPS}}+d-{\mathrm{\&mu;}}_{\mathrm{INS}})}^2/d]-\exp [-{({\mathrm{\&gamma;}}_{\mathrm{GPS}}-d-{\mathrm{\&mu;}}_{\mathrm{INS}})}^2/d\left]\right\}$ (20)

$+B\left\{\exp \right[-2({\mathrm{\&gamma;}}_{\mathrm{GPS}}+d-{\mathrm{\&mu;}}_{\mathrm{INS}}){\mathrm{\&Delta;\&tau;}}_1^2/d]-\exp [-2({\mathrm{\&gamma;}}_{\mathrm{GPS}}-d-{\mathrm{\&mu;}}_{\mathrm{INS}}){\mathrm{\&Delta;\&tau;}}_1^2/d\left]\right\}$

$+2B\left\{\exp \right[-2{({\mathrm{\&gamma;}}_{\mathrm{GPS}}+d-{\mathrm{\&mu;}}_{\mathrm{INS}})}^2+{\mathrm{\&Delta;\&tau;}}_1^2/\left(2d\right)]-\exp [-2{({\mathrm{\&gamma;}}_{\mathrm{GPS}}-d-{\mathrm{\&mu;}}_{\mathrm{INS}})}^2+{\mathrm{\&Delta;\&tau;}}_1^2/\left(2d\right)\left]\right\}$

Wherein, B=1/ (2 π d).

Step 5: ask for D respectively _GPSSquare error MSE _GPSAnd D _INSSquare error MSE _INS

Need solve D _GPSMSE _GPSAnd D _INSSquare error MSE _INS, just can set up Gauss's code phase Discr..MSE _GPSAnd MSE _INSSolution procedure similar, by setup parameter, the loop update times is nf=400, upgrades for loop each time, the DLL of GPS receiver has the I of corresponding real-time change _E, Q _E, I _L, Q _L, and also all there is the G of pair change in the INS system _E, G _LSo, code phase Discr. D _GPSD with new structure _INSAlso to upgrade 400 times, can obtain their average like this

Then can obtain MSE _GPSAnd MSE _INS, their expression formula is as follows,

${\mathrm{MSE}}_{\mathrm{GPS}}=\sqrt{\left[\underset{i=1}{\overset{400}{\mathrm{\&Sigma;}}}{(D_{\mathrm{GPS}}\left(i\right)-{\stackrel{\&OverBar;}{D}}_{\mathrm{GPS}})}^2\right]/400}---\left(21\right)$

${\mathrm{MSE}}_{\mathrm{INS}}=\sqrt{\left[\underset{i=1}{\overset{400}{\mathrm{\&Sigma;}}}{(D_{\mathrm{INS}}\left(i\right)-{\stackrel{\&OverBar;}{D}}_{\mathrm{INS}})}^2\right]/400}---\left(22\right)$

Step 6: make up Gauss's code phase Discr. D _GAUSS

Because square error is to consider the index of unbiasedness and validity simultaneously, so the dark combined tracking loop of the GPS/INS D of the present invention's proposition _GAUSSAdopt D _GPSSquare error MSE _GPSAnd D _INSSquare error MSE _INS, as the weight coefficient of systematic error estimation.D _GAUSSExpression formula be:

D _GAUSS＝(D _GPS/MSE _GPS)+(D _INS/MSE _INS) (23)

After the normalization be:

$D_{\mathrm{GAUSS}}=\frac{{\mathrm{MSE}}_{\mathrm{INS}}{D}_{\mathrm{GPS}}+{\mathrm{MSE}}_{\mathrm{GPS}}{D}_{\mathrm{INS}}}{{\mathrm{MSE}}_{\mathrm{GPS}}+{\mathrm{MSE}}_{\mathrm{INS}}}---\left(24\right)$

As shown in Figure 2, be advanced code phase function G _EWith hysteresis code phase function G _LPhase place output in different loop updated time.The Gaussian function generator synchronously utilizes code phase in the GPS receiver and the information of INS, on the Gaussian function basis of standard, produces the leading function G of INS _E=G (γ _GPS-d) and hysteresis function G _L=G (γ _GPS+ d), and construct INS code phase Discr. D with similar GPS receiver code phase-shift discriminator aufbauprinciple _INS=(G _E ²-G _L ²)/(G _E ²+ G _L ²).

What provide above is the situation of a multipath signal, for many multipath signals, i.e. and M＞1 o'clock, the following footnote i value in the formula (1) is from 1 to M, the situation of a computation process and a multipath signal is similar.As when having two multipath signals, this moment M=2, the i value be from 1 to 2, the signal that receiver receives passes through down coversion and Phase Tracking can get:

S(t)＝A·x[(1+ζ)t-τ ₀]cos(ψ)+b ₁A·x[(1+ζ)t-τ ₀-Δτ ₁]cos(ψ+β ₁)

+b ₂A·x[(1+ζ)t-τ ₀-Δτ ₂]cos(ψ+β ₂) (25)

Wherein, Δ τ ₁=τ ₁-τ ₀With Δ τ ₂=τ ₂-τ ₀Be respectively the 1st and the 2nd multipath signal C/A sign indicating number time delay, τ with respect to direct signal ₁And τ ₂The C/A sign indicating number time delay of representing the 1st and the 2nd multipath signal respectively, β ₁=θ ₁-θ ₀And β ₂=θ ₂-θ ₀Be respectively the 1st and the 2nd multipath signal carrier phase deviation, θ with respect to direct signal ₁And θ ₂The carrier phase deviation of representing the 1st and the 2nd multipath signal respectively.

Core of the present invention is to utilize the GPS relevant information to set up the INS code phase Discr. of synchronous working, and obtains the square error of conventional code phase-shift discriminator output data and the square error of INS code phase Discr. output data in real time.This invention has changed traditional receiver DLL inner structure, by simulating, verifying should the invention feasibility, shown in Fig. 3～Fig. 5 (b).

From Fig. 3 (a) as can be seen, the C/A sign indicating number autocorrelation function peak of curve of GPS is 1 separately, and the C/A sign indicating number autocorrelation function peak of curve that INS estimates is approximately 0.6.Gauss's code phase Discr. can be found out the autocorrelation function peak of curve about 1.6 that obtains with their auto-correlation function value stack from Fig. 3 (b).By changing the autocorrelation function curve, improve the discriminating precision of code phase error, can effectively suppress multipath and disturb.

Comparison diagram 4 (a) and Fig. 4 (b) do not exist under the multipath undesired signal as can be seen, and the phase demodulation when C/A code phase time delay is 0 is output as 0, and exists under the situation of multipath undesired signal, and skew has taken place the zero point of phase demodulation output.Contrast D _GPSAnd D _GAUSSPhase demodulation output under multipath disturbs can be observed the designed D of the present invention _GAUSSCan better suppress the interference of multipath signal, simulation result has verified that the present invention can fundamentally eliminate the error of being brought by the multipath interference.

Can clearly find out traditional incoherent after-power type code phase Discr. D that subtracts in advance by Fig. 5 (a) _GPSWith the code phase error output of Gauss's code phase Discr. of the present invention in different loop updated time, contrast is found, Gauss's code phase Discr. D of the present invention _GAUSSCurve of output all be better than the incoherent after-power type code phase Discr. D that subtracts in advance in overshoot, time to peak and rise time _GPSOutput, the former code phase error precision is also better, simulating, verifying Gauss's code phase Discr. that the present invention set up be feasible.

Fig. 5 (b) is D _GPSAnd D _GAUSSThe code phase error cumulative curve changes corresponding to the code phase error value among Fig. 5 (a), upgrades in preceding 50 times D at loop _GAUSSAnd D _GPSError amount be negative value, so accumulated error constantly increases D _GAUSSMaximum accumulated error compares D _GPSLittle about two chips.

Claims (9)

1. one kind based on the dark combined tracking loop of GPS/INS Gauss code phase Discr., the information source that makes up this Gauss's code phase Discr. comprises local carrier generator, local C/A code generator, correlator, frequency mixer, integration totalizer and GPS receiver tracking loop circuit code phase Discr., it is characterized in that information source also comprises Gaussian function generator and INS code phase Discr.; The local carrier generator produces the carrier wave reproducing signals of 90 ° of phasic differences mutually on branch road in the same way and quadrature branch, local code C/A code generator is in that branch road and quadrature branch produce respectively in advance in the same way, instant and hysteresis replica code, intermediate-freuqncy signal respectively simultaneously by a frequency mixer and local carrier generator in the same way with the carrier wave reproducing signals multiplicative mixing of quadrature two branch roads generation, the mixing results that obtains again with local code C/A code generator branch road and quadrature branch in the same way produce respectively leading, immediately, the hysteresis replica code carries out the related operation of time, and the signal that obtains added up by an integration totalizer respectively, obtain the relevant output I of the leading branch road on the in-phase branch _E, instant branch road relevant output I _P, the hysteresis branch road relevant output I _L, and the relevant output Q that reaches the hysteresis branch road in advance, immediately of quadrature branch _E, Q _PAnd Q _LThe relevant output I of the instant branch road of in-phase branch _PRelevant output Q with the instant branch road of quadrature branch _PIntroduce in the Gaussian function generator, the code phase information that the Gaussian function generator utilizes DLL to introduce is again according to relevant information μ _INS,

Make up synchronous advanced code phase function G _EWith hysteresis code phase function G _L, μ _INSBe the code phase error of INS system estimation,

Be the code phase square error of INS system estimation, utilize advanced code phase function G _EWith hysteresis code phase function G _LMake up INS code phase Discr., upgrade, obtain the square error MSE of GPS receiver tracking loop circuit code phase Discr. by loop _GPSSquare error MSE with INS code phase Discr. _INS, two square errors are adjusted the output of GPS receiver tracking loop circuit code phase Discr. and INS code phase Discr. as weight coefficient, make up Gauss's code phase Discr. D _GAUSS

2. according to claim 1 a kind of based on the dark combined tracking loop of GPS/INS Gauss code phase Discr., it is characterized in that the structure parameter of described Gauss's code phase Discr. is: the local code frequency f _LO=1.023MHz, the intermediate frequency carrier frequency f _IF=1575.42MHz, sample frequency f _s=5MHz, carrier loop bandwidth 16Hz, sign indicating number loop bandwidth 8Hz, damping factor ξ=0.707, sign indicating number loop gain K _Code=1, carrier wave ring gain K _Carr=0.5 π, loop update times nf=400, correlator spacing d=0.5 chip, the C/A code phase time delay of direct signal and multipath signal is 0 and 0.75 chip, amplitude is respectively 1 and 0.65.

3. one kind is designed the described method based on the dark combined tracking loop of GPS/INS Gauss code phase Discr. of claim 1, it is characterized in that, specifically comprises the steps:

Step 1: at first analyze the influence of multipath interference to the code tracking loop: in the GPS navigation system, under the situation of not considering modulating data and noise, the signal model S (t) that receiver receives is:

Wherein, A is the amplitude of direct signal, and x (t) is a t C/A sign indicating number constantly, and ζ is Doppler shift ω _dWith carrier frequency ω _cRatio, τ ₀The C/A sign indicating number time delay of expression direct signal, α _i=b _iA is the amplitude of i bar multipath signal, b _iBe i bar multipath signal and the amplitude ratio of direct signal, τ _iThe C/A sign indicating number time delay of representing i bar multipath signal, θ ₀And θ _iBe respectively the carrier phase deviation of direct signal and i bar multipath signal, M represents the bar number of multipath signal; By code tracking loop principle of work, obtain the relevant output I of the leading branch road on the in-phase branch then _E, instant branch road relevant output I _P, the hysteresis branch road relevant output I _L, the relevant output Q of the leading branch road on the quadrature branch _E, instant branch road relevant output Q _PAnd the relevant output Q of hysteresis branch road _L

Step 2: adopt the incoherent after-power type code phase Discr. that subtracts in advance, as the initial code phase positions Discr. for the treatment of improved GPS receiver tracking loop circuit, this initial code phase positions Discr. D _GPSFor:

The relevant output I of the leading branch road on the in-phase branch that step 1 is obtained _E, the hysteresis branch road relevant output I _LRelevant output Q with leading branch road on the quadrature branch _E, the hysteresis branch road relevant output Q _LSubstitution formula (2) obtains the D under the multipath interference _GPSPhase demodulation function: D _GPS=D _n+ D _Err, wherein, D _nIncoherent phase demodulation output when not existing multipath to disturb, D _ErrDisturb the incoherent phase demodulation output that causes for multipath;

With the D under the multipath interference that obtains _GPSThe phase demodulation function carries out normalized;

Step 3: make up the Gaussian function generator, and obtain INS advanced code phase function G _EWith hysteresis code phase function G _L, detailed process is:

At first, measured Gaussian function

Again in conjunction with the output information of INS with from the synchronous Gaussian function generator of GPS receiver DLL information architecture, the Gaussian function G (γ that the Gaussian function generator is adopted _GPS) as follows:

Wherein, γ _GPSFor deriving from the code phase error that receiver DLL produces in real time,

Be local code phase delay, μ _INSBe the code phase error of INS system estimation,

Be the code phase square error of INS system estimation,, choose for synchronous with gps system work Consistent with the correlator interval d of DLL;

There is under the situation of i bar multipath signal interference the leading Gaussian function G that the Gaussian function generator produces _EWith hysteresis Gaussian function G _LBe respectively:

In formula (5)～(6), Δ τ _iBe the C/A sign indicating number time delay of i bar multipath signal with respect to direct signal, Δ τ _i=τ _i-τ ₀, τ ₀C/A sign indicating number time delay for direct signal;

Step 4: structure INS code phase Discr. D _INS:

The advanced code phase function G that then step 3 is obtained _EWith hysteresis code phase function G _LSubstitution formula (7) obtains the D under the multipath interference _INSThe phase demodulation function, and the D under the multipath that obtains disturbed _INSThe phase demodulation function carry out normalized;

Step 5: determine GPS receiver tracking loop circuit code phase Discr. D _GPSSquare error MSE _GPSWith INS code phase Discr. D _INSSquare error MSE _INS, specifically:

Wherein, nf is the loop update times, D _GPSThe value of the GPS receiver tracking loop circuit code phase Discr. when the i time loop upgraded during (i) expression was upgraded for nf time,

The average of representing the GPS receiver tracking loop circuit code phase Discr. that nf loop renewal obtains; D _INSThe value of the INS code phase Discr. when (i) showing the i time loop renewal,

The average of representing the INS code phase Discr. that nf loop renewal obtains;

Step 6: make up Gauss's code phase Discr. D _GAUSS:

Carry out after the normalization be:

Through type (11) obtains final Gauss's code phase Discr. D that will make up _GAUSS

4. a kind of method for designing according to claim 3 based on the dark combined tracking loop of GPS/INS Gauss code phase Discr., it is characterized in that, in the described step 1, under the situation of considering a multipath signal, the relevant output I of the leading branch road on the in-phase branch of acquisition _E, instant branch road relevant output I _P, the hysteresis branch road relevant output I _L, the relevant output Q of the leading branch road on the quadrature branch _E, instant branch road relevant output Q _PAnd the relevant output Q of hysteresis branch road _LBe respectively:

Wherein,

Be the carrier phase deviation of estimating,

Be direct signal C/A code phase delay evaluated error, Be the carrier phase of local estimated signal, Δ τ ₁=τ ₁-τ ₀Be the C/A sign indicating number time delay of a multipath signal with respect to direct signal, τ ₁The C/A sign indicating number time delay of a multipath signal of expression, β ₁=θ ₁-θ ₀Be the carrier phase deviation of multipath signal with respect to direct signal, θ ₁The carrier phase deviation of a multipath signal of expression, d represents the correlator spacing, the autocorrelation function R (γ) of C/A sign indicating number sequence is approximately:

In the formula, T _cBe the time that chip continued of C/A sign indicating number.

5. according to claim 3 or 4 described a kind of methods for designing based on the dark combined tracking loop of GPS/INS Gauss code phase Discr., it is characterized in that, described correlator spacing d=0.5 chip, the C/A code phase time delay of direct signal and multipath signal is 0 and 0.75 chip, and amplitude is respectively 1 and 0.65.

6. a kind of method for designing based on the dark combined tracking loop of GPS/INS Gauss code phase Discr. according to claim 3 is characterized in that the D described in the step 2 _GPSThe phase demodulation function, under the situation that has a multipath signal, its expression formula is:

Wherein,

7. a kind of method for designing based on the dark combined tracking loop of GPS/INS Gauss code phase Discr. according to claim 3 is characterized in that, the leading Gaussian function G that the Gaussian function generator in the described step 3 produces _EWith hysteresis Gaussian function G _L, be under one the situation, to be specially at multipath signal:

。

8. a kind of method for designing based on the dark combined tracking loop of GPS/INS Gauss code phase Discr. according to claim 3 is characterized in that the loop update times nf=400 described in the step 3.

9. a kind of method for designing based on the dark combined tracking loop of GPS/INS Gauss code phase Discr. according to claim 3 is characterized in that the INS code phase Discr. D described in the step 4 _INS, under the situation that has a multipath signal be:

Wherein, B parameter=1/ (2 π d).

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