CN102183770A - GPS (Global Positioning System) pseudo-random code tracking loop for preventing multi-path interference and method for preventing multi-path interference thereof - Google Patents

Abstract

The invention provides a GPS (Global Positioning System) pseudo-random code tracking loop for preventing multi-path interference and a method for preventing the multi-path interference thereof. The loop comprises a mixer, a correlator, an integration accumulator, a small wave phase detector, a loop filter and a local pseudo-random code generator. In the invention, the GPS pseudo-random code tracking loop adopts the small wave phase detector to detect a discontinuity point wherein the self-correlation function curve slope changes into a positive value from a zero value, is more accurate in the phase detection result, is free from the influence of the number of multi-path signals, and does not need to estimate the multi-path signals. In the invention, the pseudo code tracking accurate of the GPS pseudo-random code tracking loop is higher than the tracking accuracy of the typical sooner-later pseudo code delay locking loop so that the measurement accuracy of the pseudo range is improved; therefore, the invention is beneficial to positioning accurately.

Description

GPS pseudo-random code track loop and anti-multipath interference method thereof that a kind of anti-multipath disturbs

Technical field

The invention belongs to the radio navigation field, be specifically related to GPS pseudo-random code track loop and anti-multipath interference method thereof that a kind of multipath disturbs.

Background technology

GPS (GPS) is based on radionavigational, has the characteristics of global, round-the-clock, continuity and real-time, can provide the location to the user, test the speed and service such as time service.The distance measuring signal of the broadband pseudo-random code of receiver user by obtaining satellites transmits in the horizon range, then according to local clock is calculated accurately, obtain the actual time of arrival of signal, thereby determine and the distance of each satellite that the communication infrastructure of system is spread spectrum communication.Every satellite all uses unique pseudo-random code, and receiver user can be distinguished the distance measuring signal of a series of gps satellites that receive by obtaining and follow the tracks of unique pseudo-random code.

Inevitably can be subjected to surrounding environment and the interference of self during the GPS operation of receiver and produce measuring error, receiver was with cisco unity malfunction when mushing error was serious.Main source of error in the measurement and positioning has satellite clock error, satellite ephemeris error, ionosphere delay error, tropospheric delay error, receiver noise error, thermonoise and multipath error etc.Along with the raising of gps system up-to-dateness and the development of reception technique, many error sources can reduce or revise by technology such as difference, empirical model and predictions, multipath error then is difficult to handle, multipath disturbs the error that causes to become pinpoint main source of error, because the existence of multipath signal, make the autocorrelation function of pseudo-random code be distorted, cause originally the distortion that becomes of S-shaped phase demodulation curve, identified result is no longer accurate.So the multipath interference mitigation technology has become one of research focus in the gps system navigator fix.The multipath interference mitigation technology has obtained deep research in communication system.

At present a lot of at the research of satelline radio-navigation systems anti-multipath aspect at present at satellite, mainly be divided into two classes, one class is by insensitive correlator of multipath signal or Discr. are designed, to reach the purpose that reduces multipath error, as narrow correlation technique, Gated Correlator and HRC (High Resolution Correlator) etc., these class methods realize simple, but the multipath rejection can't satisfy high-precision range finding requirement usually.Another kind of method is to utilize the benchmark related function that the parameter of direct signal and multipath signal is estimated, and utilizes results estimated to eliminate the influence of multipath signal.Most of Estimation of Parameters method all is based on the maximal possibility estimation criterion, as MEDLL, VC (Vision Correlator), FIMLA technology such as (Fast Iterative Maxim-Likelihood Algorithm).Although be considered to optimum usually based on the method for maximal possibility estimation criterion, it realizes very complicated, is restricted in actual applications.People such as Chung-Liang Chang has proposed a kind of multipath inhibition method that adopts auto-adaptive filtering technique in addition, and its basic thought is that the signal model that will receive is assumed to be the FIR filter model, signal parameter is estimated to be converted into the coefficient estimation of wave filter.But, its precision also depends on the selection of filter order, big filter order no doubt can improve estimated accuracy, but increase along with filter order, algorithm the convergence speed also can be slack-off, and when the received signal limited bandwidth, even also can produce bigger measuring error under the condition of no multipath, so the actuality of this algorithm application is limited.

Summary of the invention

At problems of the prior art, the invention provides GPS pseudo-random code track loop and anti-multipath interference method thereof that a kind of anti-multipath disturbs, with the pseudo-random code autocorrelation function is point of penetration, utilize wavelet transformation to detect the starting point of autocorrelation function, thereby reach the purpose of differentiating the pseudo-random code error, utilize the small echo phase detector to substitute traditional sign indicating number ring phase detector.

The present invention proposes the GPS pseudo-random code track loop that a kind of anti-multipath disturbs, and comprises frequency mixer, correlator, integration totalizer, small echo phase detector, loop filter and local pseudo-noise code generator.

Described frequency mixer is used for carrier wave that this locality is produced and the intermediate-freuqncy signal s that receives _IF(n) carry out mixing, peel off carrier wave, the input end of frequency mixer receives local carrier wave and the intermediate-freuqncy signal s that produces _IF(n), the local carrier wave that produces is local carrier digital controlled oscillator (carrier wave NCO) transfers to frequency mixer through cosine table a carrier wave, the M road pseudo-random code that the output terminal of frequency mixer and the pseudo-random code that local pseudo-noise code generator produces are delayed time after (delay cycle is a sampling period) is carried out relevant respectively in M correlator, the span of M is 1.5N≤M≤2N, and N is the sampling number of a chip.

After correlated process is finished, the output of this M road correlator being sent to the integration that M integration totalizer carry out a pseudo-random code cycle respectively adds up again, the output terminal of each correlator is connected with the input end of an integration totalizer respectively, is used for the effect of low-pass filter.Each integration totalizer output terminal all is connected with the small echo phase detector, obtain slope variation in the autocorrelation function curve that M integral accumulation by integration totalizer output form catastrophe point (slope by null value become on the occasion of point), carry out the pseudo-random code phases error and differentiate, obtain pseudo-random code phase demodulation error.Then the pseudo-random code phase demodulation error that obtains is exported in the loop filter, so that signal (the pseudo-random code phase demodulation error) generation of input loop filter is estimated accurately at the loop filter output terminal, signal after the output mixing, the exponent number of loop filter and noise bandwidth have determined the dynamic response situation of loop filter to signal; The signal of local pseudo-noise code generator after the output terminal output mixing of local pseudo-random code digital controlled oscillator reception loop filter, generation is sent into the correlator input end through adjusted local pseudo-random code and is correlated with.

Described small echo phase detector is made up of wavelet transformer and phase demodulation Error Calculator, N is the sampling number of a chip, wavelet transformer receives M integration accumulation result by M integration totalizer output, select the wavelet function of energy detected slope catastrophe point that input signal is carried out wavelet transformation, obtain the positional information L (L is greater than 1 value less than M) of slope catastrophe point, and positional information sent into the phase demodulation Error Calculator, the effect of phase demodulation Error Calculator is that the positional information of input is converted to the output of phase demodulation error.

The present invention proposes a kind of anti-multipath interference method of GPS pseudo-random code track loop of anti-multipath interference, specifically may further comprise the steps:

Step 1: the pseudo-random code in the received signal and the pseudo-random code that local pseudo-noise code generator produces are carried out relevant, obtain the autocorrelation function curve of pseudo-random code.

The carrier wave that described received signal produces for the local carrier digital controlled oscillator after cosine table transfers to frequency mixer with the intermediate-freuqncy signal s that receives _IF(n) carry out the signal that obtains after the mixing; The pseudo-random code that this locality produces is carried out the time-delay of M road, the time-delay of every road is a sampling period, the span of M is 1.5N≤M≤2N, N is the sampling number of a chip, carry out relevant respectively after integration adds up with the signal after the mixing with the time-delay of this M road pseudo-random code then, obtain M integral accumulation, form the autocorrelation function curve of pseudo-random code by M integral accumulation.

Step 2: utilize autocorrelation function slope of a curve that the small echo phase detector detects pseudo-random code by null value become on the occasion of catastrophe point, obtain the phase demodulation error of pseudo-random code.

The small echo phase detector utilizes wavelet function that the autocorrelation function curve of the pseudo-random code that obtains in the step 1 is carried out wavelet transformation, with the autocorrelation function rate of curve that obtains pseudo-random code by null value become on the occasion of catastrophe point, obtain pseudo-random code phase demodulation error thus.

Step 3: utilize the pseudo-random code phase demodulation error that obtains to carry out pseudo-random code and follow the tracks of.

By the pseudo-random code phase demodulation error that step 2 obtains, pass through loop filter, local pseudo-random code digital controlled oscillator and local pseudo-noise code generator in turn, adjust the phase place of pseudo-random code, realize the tracking of pseudo-random code.

The invention has the advantages that:

(1) the present invention proposes GPS pseudo-random code track loop and the anti-multipath interference method thereof that a kind of anti-multipath disturbs, and suppresses multipath by the structure of improving GPS pseudo-random code track loop and disturbs, and realizes simply, and having preferably, multipath suppresses real-time and stability;

(2) the present invention proposes GPS pseudo-random code track loop and the anti-multipath interference method thereof that a kind of anti-multipath disturbs, adopt the small echo phase detector, be used to detect the autocorrelation function rate of curve by null value become on the occasion of the catastrophe point point, identified result is more accurate, and be not subjected to the influence of multipath signal number, not needing to carry out multipath signal estimates, the pseudo-code tracing precision of GPS pseudo-random code track loop of the present invention is higher than the tracking accuracy of typical morning of slow pseudo-code delay-locked loop, thereby improved the measuring accuracy of pseudorange, helped accurate location.

Description of drawings

Fig. 1: the structural representation of the GPS pseudo-code tracing loop that a kind of anti-multipath that the present invention proposes disturbs;

Fig. 2: the structural representation of the small echo phase detector among the present invention;

Fig. 3-A: the pseudo-random code autocorrelation function curve when not having multipath signal;

Fig. 3-B: the pseudo-random code autocorrelation function when having a multipath signal;

Fig. 3-C: the pseudo-random code autocorrelation function when having two multipath signals;

Fig. 3-D: the pseudo-random code autocorrelation function when having three multipath signals;

Fig. 4: the autocorrelation function curve among the present invention in the pseudo-code tracing process;

Fig. 5: signal to noise ratio snr=-10dB, the present invention and early slow pseudo-code delay-lock loop pseudo-code tracing result when having a multipath signal;

Fig. 6: signal to noise ratio snr=-20dB, the present invention and early slow pseudo-code delay-lock loop pseudo-code tracing result when having three multipath signals.

Among the figure: the 1-frequency mixer; The 2-correlator; 3-integration totalizer; 4-small echo phase detector;

The 5-loop filter; The local pseudo-noise code generator of 6-; The local pseudo-random code digital controlled oscillator of 7-;

The 8-cosine table; 9-local carrier digital controlled oscillator; The 10-wavelet transformer;

11-phase demodulation Error Calculator.

Embodiment

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

The present invention proposes the GPS pseudo-random code track loop that a kind of anti-multipath disturbs, and as shown in Figure 1, comprises frequency mixer 1, correlator 2, integration totalizer 3, small echo phase detector 4, loop filter 5 and local pseudo-noise code generator 6.

Described frequency mixer 1 is used for carrier wave that this locality is produced and the intermediate-freuqncy signal s that receives _IF(n) carry out mixing, peel off carrier wave, the input end of frequency mixer 1 receives local carrier wave and the intermediate-freuqncy signal s that produces _IF(n), the local carrier wave that produces is local carrier digital controlled oscillator 9 (carrier wave NCO) transfers to frequency mixer 1 through cosine table 8 a carrier wave, the M road pseudo-random code that the output terminal of frequency mixer 1 and the pseudo-random code that local pseudo-noise code generator 6 produces are delayed time after (delay cycle is a sampling period) is carried out relevant respectively in M correlator 2, the related data that is adopted is in a leading side of in-phase branch, the span of M is 1.5N≤M≤2N, and N is the sampling number of a chip.

After correlated process is finished, the output of this M road correlator 2 being sent to the integration that M integration totalizer 3 carry out a pseudo-random code cycle respectively adds up again, the output terminal of each correlator 2 is connected with the input end of an integration totalizer 3 respectively, is used for the effect of low-pass filter.Each integration totalizer 3 output terminal all is connected with small echo phase detector 4, obtain slope variation in the autocorrelation function curve that M integral accumulation by integration totalizer 3 output form catastrophe point (slope by null value become on the occasion of point), carry out the pseudo-random code phases error and differentiate, obtain pseudo-random code phase demodulation error.Then the pseudo-random code phase demodulation error that obtains is exported in the loop filter 5, so that signal (the pseudo-random code phase demodulation error) generation of input loop filter 5 is estimated accurately at loop filter 5 output terminals, signal after the output mixing, the exponent number of loop filter 5 and noise bandwidth have determined the dynamic response situation of 5 pairs of signals of loop filter; Local pseudo-noise code generator 6 is exported mixing (filtering) signal afterwards through the output terminal that local pseudo-random code digital controlled oscillator 7 receives loop filter 5, adjusts local pseudo-random code phases through local pseudo-random code digital controlled oscillator, local pseudo-noise code generator respectively.Generation is sent into correlator 2 input ends through adjusted local pseudo-random code and is correlated with.

As shown in Figure 2, described small echo phase detector 4 is made up of wavelet transformer 10 and phase demodulation Error Calculator 11, N is the sampling number of a chip, M the integration accumulation result that wavelet transformer 10 receives by 3 outputs of M integration totalizer, select the wavelet function of energy detected slope catastrophe point that input signal is carried out wavelet transformation, obtain the positional information L (L is greater than 1 value less than M) of slope catastrophe point, and positional information sent into phase demodulation Error Calculator 11, the effect of phase demodulation Error Calculator 11 is that the positional information of input is converted to the output of phase demodulation error.

At first, successfully capture after gps signal finishes in the GPS receiving system, enter tracking phase, the phase deviation of local pseudo-code and the pseudo-code error that receives is determined local pseudo-code initial phase in ± 0.5 chip.Then, the intermediate-freuqncy signal that receives is carried out mixing with the local carrier wave that produces, and carries out relevantly with the pseudo-code that this locality produces again, obtains each value after adding up through integration and obtains the autocorrelation function curve.The starting point of utilizing small echo phase detector 4 to find the autocorrelation function rate of curve to begin to change again draws code phase error.At last code phase error is sent into loop filter 5, form closed circuit, carry out the loop adjustment, up to the tracking fully that realizes pseudo-code.

The GPS pseudo-random code track loop that a kind of anti-multipath that the present invention proposes disturbs is the improvement technology that multipath signal is handled, to multipath signal is insensitive, be not subjected to the influence of multipath signal bar number, do not need to carry out the estimation of multipath signal parameter, can reduce the complexity of the signal Processing of whole GPS pseudo-code tracing loop and necessity, and improve the accuracy of further processing.

The GPS pseudo-random code track loop that a kind of anti-multipath that the present invention proposes disturbs is not subjected to the influence of multipath signal bar number, and is as follows to the insensitive concrete foundation of multipath signal:

Because the intermediate-freuqncy signal that receives of GPS receiver is the composite signal of the multipath signal of reflected by objects around satellite direct signal and the GPS receiver, then the intermediate-freuqncy signal s (t) that receives of GPS receiver is expressed as:

$s\left(t\right)=\underset{i=0}{\overset{M}{\mathrm{\Σ}}}{a}_i\mathrm{Ad}\left(t\right)c(t-{\mathrm{\τ}}_i)\cos [{\mathrm{\ω}}_{0}t+{\mathrm{\φ}}_i\left(t\right)]---\left(1\right)$

Wherein: i=0 represents that this road intermediate-freuqncy signal is a direct signal, and other are multipath signal for M road intermediate-freuqncy signal, and M represents the bar number of multipath signal; A represents carrier amplitude; a _iThe attenuation coefficient of expression intermediate-freuqncy signal amplitude, when i=0, a _i=a ₀The attenuation coefficient of=1 expression direct signal amplitude; T express time variable, τ _iRepresent the pseudo-random code time-delay of i road signal; D (t) expression navigation data information; C (t-τ _i) expression different delayed time the GPS pseudo-random code; ω ₀Be the IF-FRE of intermediate-freuqncy signal, direct signal has identical frequency with multipath signal; φ _i(t) phase place of expression i road intermediate-freuqncy signal.

If carrier amplitude A=1, navigation data information d (t) is constant amount, i.e. d (t)=1, and then the intermediate-freuqncy signal s (t) that receives of GPS receiver is expressed as:

$s\left(t\right)=\underset{i=0}{\overset{M}{\mathrm{\Σ}}}{a}_{i}c(t-{\mathrm{\τ}}_i)\cos [{\mathrm{\ω}}_{0}t+{\mathrm{\φ}}_i]---\left(2\right)$

If in the pseudo-random code tracing process, carrier wave has been realized correct tracking, and then local carrier digital controlled oscillator 9 through the in-phase branch carrier wave that cosine table 8 produces is

And

The phase estimation of expression direct signal carrier wave, φ ₀The carrier phase of expression direct signal reality; The GPS pseudo-random code that local pseudo-noise code generator 6 produces is

In the formula

Expression direct signal pseudo-random code time delay is estimated.The carrier signal that produces with this locality respectively of the intermediate-freuqncy signal of Jie Shouing then

With the GPS pseudo-random code

Carry out related operation, obtain the aligning correlation I of in-phase branch _pFor

$I_p=\underset{i=0}{\overset{M}{\mathrm{\Σ}}}\frac{a_i}{2}R({\widehat{\mathrm{\τ}}}_0-{\mathrm{\τ}}_i)\cos ({\mathrm{\φ}}_i-{\widehat{\mathrm{\φ}}}_0)=\underset{i=0}{\overset{M}{\mathrm{\Σ}}}\frac{a_i}{2}R({\widehat{\mathrm{\τ}}}_0-{\mathrm{\τ}}_i)$

(3)

$=\underset{i=0}{\overset{M}{\mathrm{\Σ}}}\frac{a_i}{2}R(\mathrm{\Δ}{\widehat{\mathrm{\τ}}}_0+{\mathrm{\τ}}_0-{\mathrm{\τ}}_i)=\frac{a_0}{2}R\left(\mathrm{\Δ}{\widehat{\mathrm{\τ}}}_0\right)+\underset{i=1}{\overset{M}{\mathrm{\Σ}}}\frac{a_i}{2}R(\mathrm{\Δ}{\widehat{\mathrm{\τ}}}_0+{\mathrm{\τ}}_0-{\mathrm{\τ}}_i)$

Wherein,

The chip error of the pseudo-random code that produces for direct signal pseudo-random code and local pseudo-noise code generator 6, Expression direct signal pseudo-random code time delay is estimated τ ₀The actual time delay of expression direct signal pseudo-random code.Because the pseudo-random code time delay of multipath signal is greater than the pseudo-random code time delay of direct signal, i.e. 0＜τ ₀≤ τ ₁≤ τ ₂≤ τ _M, τ ₀-τ _i≤ 0, i=1,2 ... M, R (τ) is the autocorrelation function of the pseudo-random code of GPS, is expressed as

$R\left(\mathrm{\&tau;}\right)=\left\{\begin{array}{cc}1-\frac{\mathrm{\&tau;}}{{\mathrm{\&tau;}}_c}& \left|\mathrm{\&tau;}\right|\&le;{\mathrm{\&tau;}}_{\mathrm{<figure-callout\; id="0"\; label="c"\; filenames="HDA0000062570300000013.png,HDA0000062570300000014.png"\; state="\{\{state\}\}">c</figure-callout>}}\\ 0& \left|\mathrm{\&tau;}\right|\&GreaterEqual;{\mathrm{\&tau;}}_c\end{array}\right.---\left(4\right)$

Wherein, the τ express time postpones, τ _cThe symbol width of C/A sign indicating number of expression GPS, the autocorrelation function R ' of pseudo-random code that then has the GPS of multipath signal (τ) is expressed as

$R^{\&prime;}\left(\mathrm{\&tau;}\right)=\frac{a_0}{2}R\left(\mathrm{\&tau;}\right)+\underset{i=1}{\overset{M}{\mathrm{\&Sigma;}}}\frac{a_i}{2}R(\mathrm{\&tau;}+{\mathrm{\&tau;}}_0-{\mathrm{\&tau;}}_i),-{\mathrm{\&tau;}}_c\&le;\mathrm{\&tau;}\&le;{\mathrm{\&tau;}}_c---\left(5\right)$

By formula (4) and (5), postpone τ by-τ when the time _c-T _cChange to τ _cProcess in, the autocorrelation function of the pseudo-random code of GPS begins to occur the point and formula (5) discipline of nonzero value

Have nothing to do, promptly have nothing to do with multipath signal, provided respectively shown in shown in Fig. 3-A, Fig. 3-B, Fig. 3-C and Fig. 3-D, having provided and do not had multipath signal, multipath signal of existence, two multipath signals of existence and have three GPS pseudo-random code autocorrelation function curves under the multipath signal situation, as can be seen from the figure, though multipath signal is different, the catastrophe point that the autocorrelation function rate of curve occur to change be slope by null value become on the occasion of point be changeless.

Therefore, as long as find the pseudo-random code autocorrelation function slope of GPS the catastrophe point that changes to occur, just can release the position of the pseudo-random code autocorrelation function peak value of GPS, thereby can obtain the phase error (chip) of the pseudo-random code of GPS at this moment, reach the purpose of phase demodulation, again the phase demodulation error is sent into loop filter 5 and carried out the loop adjustment,, realize pseudo-code tracing through the continuous adjustment of loop.

Wavelet analysis is a kind of new Time-Frequency Analysis Method that developed in the last few years, and it can carry out wavelet transformation to signal by choosing different wavelet functions, thereby finds some unique point of signal function.The present invention utilize discrete wavelet transformer to bring to detect GPS the pseudo-random code autocorrelation function slope by null value become on the occasion of catastrophe point, phase demodulation is carried out in the position that obtains suddenling change.

If the length of a chip of pseudo-random code is τ _c, the sampling number of a chip is N, for obtaining the pseudo-random code autocorrelation function that multipath disturbs GPS down (mainly get the peak point left side a section), with the signal I of in-phase branch generation _PForward every a sampled point, (span of M is 1.5N≤M≤2N promptly earlier the pseudo-random code of local pseudo-noise code generator 6 to be carried out the time-delay of M road, N is the sampling number of a chip, with guarantee to detect the autocorrelation function slope by zero become on the occasion of point), the time-delay of every road is a sampling period, carrying out relevant back integration respectively with the signal after the mixing and this M road pseudo-code then adds up, obtain M integral accumulation, thereby obtain the autocorrelation function curve formed by M integral accumulation, as shown in Figure 4, horizontal ordinate is the chip time-delay, when time-delay is 0 τ _cThe time correspondence be in-phase branch I _P, ordinate is the autocorrelation value of pseudo-random code.When pseudo-code realized following the tracks of fully, the pseudo-random code that local pseudo-noise code generator 6 produces was synchronous through time-delay back, M road with the pseudo-random code that will follow the tracks of.Like this, utilize wavelet transformation just can find the position of the catastrophe point of autocorrelation function.

When pseudo-random code realized following the tracks of fully, the starting point of autocorrelation function should be at 1 τ _c(position of the super previous chip of in-phase branch) supposes the t moment in the pseudo-random code tracing process, and the starting point that detects autocorrelation function is at n τ _cThe position, phase demodulation error D that then should be constantly _ErrBe expressed as

D _err＝(n-1)τ _c (6)

Small echo phase detector 4 has changed traditional phase detector structure, adopts wavelet transformation to calculate pseudo-code error.The precision of phase demodulation is relevant with the sampling number of a chip, and sampled point is many more, and identified result is accurate more, if the sampling number of a chip is N, then the degree of accuracy of phase demodulation is a 1/N chip, but increases hard-wired complexity the degree of accuracy raising time.To sum up, the GPS pseudo-random code track loop that a kind of anti-multipath proposed by the invention disturbs can suppress the interference of multipath signal, realizes that adjustment loop realizes the purpose of tracking through small echo phase detector 4 output phase demodulation errors.

The present invention proposes a kind of anti-multipath interference method of GPS pseudo-random code track loop of anti-multipath interference, specifically may further comprise the steps:

Step 1: the pseudo-random code in the received signal and the pseudo-random code that local pseudo-noise code generator 6 produces are carried out relevant, obtain the autocorrelation function curve of pseudo-random code;

Described received signal is that the carrier wave that produces of local carrier digital controlled oscillator 9 is through cosine table 8 transfers to frequency mixer 1 after and the intermediate-freuqncy signal s that receives _IF(n) carry out the signal that obtains after the mixing; The pseudo-random code that this locality produces is carried out the time-delay of M road, the time-delay of every road is a sampling period, the span of M is 1.5N≤M≤2N, N is the sampling number of a chip, carry out relevant respectively after integration adds up with the signal after the mixing with the time-delay of this M road pseudo-random code then, obtain M integral accumulation, form the autocorrelation function curve of pseudo-random code by M integral accumulation.

Step 2: utilize autocorrelation function slope of a curve that small echo phase detector 4 detects pseudo-random codes by null value become on the occasion of catastrophe point, obtain the phase demodulation error of pseudo-random code;

Small echo phase detector 4 utilizes wavelet function that the autocorrelation function curve of the pseudo-random code that obtains in the step 1 is carried out wavelet transformation, with the autocorrelation function rate of curve that obtains pseudo-random code by null value become on the occasion of catastrophe point, obtain pseudo-random code phase demodulation error thus.

Step 3: utilize the pseudo-random code phase demodulation error that obtains to carry out pseudo-random code and follow the tracks of;

By the pseudo-random code phase demodulation error that step 2 obtains, pass through loop filter 5, local pseudo-random code digital controlled oscillator 7 and local pseudo-noise code generator 6 in turn, adjust the phase place of pseudo-random code, realize the tracking of pseudo-random code.

Be that instantiation illustrates performance of the present invention with antagonism GPS multipath signal below.The computer simulation program simulation produces the C/A sign indicating number of GPS, the employing code length is 1023 pseudo-random code, code check is 1.023MHz, and the sampling number of establishing a chip is 100 times, because carrier wave is very little to the influence of multipath signal, can suppose simultaneously that then carrier wave is synchronous fully, the GPS pseudo-random code track loop that the simple the present invention of investigation proposes is to the inhibition effect of multipath signal, and contrasts under different signal to noise ratio (S/N ratio)s with traditional leading-hysteresis phase detecting method (early pseudo-random code delay locked loop) late.As shown in Figure 5, when signal to noise ratio snr=-during 10dB, suppose only to exist a multipath signal, the present invention and traditional morning slow pseudo-code delay locked loop the code tracking result, the attenuation coefficient a of multipath signal wherein ₁=0.6, sign indicating number time-delay τ ₁=0.4 τ _cAs can be seen from the figure, after error was stable, traditional morning, slow pseudo-random code delay locked loop existed bigger tracking error, and GPS pseudo-random code track loop of the present invention can be followed the tracks of pseudo-code accurately.As shown in Figure 6, when signal to noise ratio snr=-during 20dB, suppose to exist three multipath signals, the present invention and traditional morning slow pseudo-random code delay locked loop the code tracking result, wherein the attenuation coefficient of multipath signal is respectively a ₁=0.6, a ₂=0.2, a ₃=0.3, the sign indicating number time-delay is respectively τ ₁=0.4 τ _c, τ ₂=0.2 τ _c, τ ₃=0.3 τ _cAs can be seen from the figure, after error was stable, traditional morning, slow pseudo-random code delay locked loop existed bigger tracking error, and GPS pseudo-random code track loop of the present invention can be followed the tracks of pseudo-random code accurately.

Claims (7)

1. the GPS pseudo-random code track loop that anti-multipath disturbs is characterized in that: comprise frequency mixer, correlator, integration totalizer, small echo phase detector, loop filter and local pseudo-noise code generator;

Obtaining M road pseudo-random code after the pseudo-random code that local pseudo-noise code generator is produced is delayed time carries out relevant respectively in M correlator with the pseudo-random code that frequency mixer is exported, the output terminal of each correlator is connected with the input end of an integration totalizer respectively, obtain M integral accumulation, each integration totalizer output terminal all is connected with the small echo phase detector, obtain slope null value in the autocorrelation function curve that M integral accumulation form become on the occasion of point, carry out the pseudo-random code phases error and differentiate, obtain pseudo-random code phase demodulation error; Then pseudo-random code phase demodulation error is exported in the loop filter, adjust local pseudo-random code phases through local pseudo-random code digital controlled oscillator, local pseudo-noise code generator respectively then.

2. the GPS pseudo-random code track loop that a kind of anti-multipath according to claim 1 disturbs, it is characterized in that: described small echo phase detector is made up of wavelet transformer and phase demodulation Error Calculator.

3. the GPS pseudo-random code track loop that a kind of anti-multipath according to claim 1 disturbs is characterized in that: described frequency mixer carries out mixing with intermediate-freuqncy signal that receives and the carrier wave that the local carrier digital controlled oscillator that receives by cosine table produces.

4. the GPS pseudo-random code track loop that a kind of anti-multipath according to claim 1 disturbs is characterized in that: the related data that adopts when described correlator is correlated with is in a leading side of in-phase branch.

5. the GPS pseudo-random code track loop that a kind of anti-multipath according to claim 1 disturbs is characterized in that: the delay cycle that the pseudo-random code that described local pseudo-noise code generator produces is delayed time is a sampling period.

6. the GPS pseudo-random code track loop that a kind of anti-multipath according to claim 1 disturbs, it is characterized in that: the span of the number M of described correlator is 1.5N≤M≤2N, wherein N is the sampling number of a chip.

7. the anti-multipath interference method of the GPS pseudo-random code track loop disturbed of an anti-multipath is characterized in that: may further comprise the steps:

Step 1: the carrier wave that the local carrier digital controlled oscillator produces after cosine table transfers to frequency mixer with the intermediate-freuqncy signal s that receives _IF(n) carry out the mixed frequency signal that obtains after the mixing; The pseudo-random code that this locality produces is carried out the time-delay of M road; Carry out relevant respectively after integration adds up with the signal after the mixing with the time-delay of this M road pseudo-random code then, obtain M integral accumulation, form the autocorrelation function curve of pseudo-random code by M integral accumulation;

Step 2: the small echo phase detector utilizes wavelet function that the autocorrelation function curve of the pseudo-random code that obtains in the step 1 is carried out wavelet transformation, the autocorrelation function rate of curve that obtains pseudo-random code by null value become on the occasion of catastrophe point, obtain pseudo-random code phase demodulation error thus;

Step 3: utilize the pseudo-random code phase demodulation error that obtains to carry out pseudo-random code and follow the tracks of;

By the pseudo-random code phase demodulation error that step 2 obtains, pass through loop filter, local pseudo-random code digital controlled oscillator and local pseudo-noise code generator in turn, adjust the phase place of pseudo-random code, realize the tracking of pseudo-random code.

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