CN104076373A - Receiver carrier wave tracking implementation method and system based on multi-information fusion assistance - Google Patents

Abstract

The invention discloses a receiver carrier wave tracking implementation method based on multi-information fusion assistance. According to the method, the radial speed of a satellite relative to a user is calculated according to information such as a satellite orbit and the position and speed of the user, and the Doppler frequency shift of a received carrier wave is predicated, wherein the information is obtained after a receiver is positioned; the actually measured value of the Doppler frequency shift of the carrier wave is output by a tracking loop in the receiver; correction is carried out on measurement remnants of the Doppler frequency shift through the Kalman filtering method, and the corrected optimal estimated value of the Doppler frequency shift is fed back to the tracking loop. According to the loop design method, dynamic influences caused due to the fact that the satellite moves relative to the user, a loop filter can be designed to work under a narrow noise bandwidth, the loop filtering effect is enhanced, and a system integrates robustness and high sensitivity. According to the Kalman filtering method adopted in the method and system, gain can be adjusted dynamically, optimal estimation of feedback of the Doppler frequency shift is achieved, and therefore the method and system have high commercial value.

Description

A kind of based on the auxiliary carrier wave tracing method of many information fusion and system

Technical field

The present invention relates to a kind of receiver carrier track implementation method, specifically track loop method for designing and the system based on information such as positioning calculation gained satellite orbit and customer location, speed.

Background technology

Along with the widespread use of GPS navigation positioning system in every profession and trade, people have proposed more and more higher requirement for the quality that improves robustness and the sensitivity of GPS receiver tracking satellite-signal and improve GPS measured value.In the design of receiver, the design of noise bandwidth and above-mentioned performance index are closely bound up.Noise bandwidth is narrower, and because the noise of fewer frequency content is allowed to enter loop, loop filtering effect is just better, and loop is also just more accurate to the tracking of signal.Yet noise bandwidth can not be at random little.Because high dynamic stress can cause the significantly change that receives signal(-) carrier frequency and phase place, and then the fierceness that causes frequency and phase tracking error is vibrated, so noise bandwidth must be greatly to tolerating the carrier frequency that causes due to high dynamic stress and the normal fluctuation of phase place, to guarantee the lasting accurate tracking of loop to signal; Otherwise, if noise bandwidth is too little, in the carrier frequency due to high dynamic stress and phase place change useful high-frequency signal composition together with together with noise by filtering, this has destroyed the authenticity that receives signal, causes loop losing lock, robustness variation.Traditional carrier tracking loop method for designing is taked balance to consider after low noise and high dynamic requirements that a common larger noise bandwidth value is chosen in compromise and is realized second order or three rank carrier loops, its root problem is the noisiness that larger noise bandwidth has improved loop, make the noiseproof feature variation of loop, the degree of accuracy of signal trace lowers, and can not realize high sensitivity and the robustness of signal trace.

As everyone knows, the impact that dynamic stress produces mainly refers to that Doppler shift that satellite and receiver relative motion bring and the clock of receiver clock float.Wherein the clock of receiver clock floats normally unknown and unpredictable, and the reflection of the Doppler effect of satellite and receiver relative motion is the variation speed of distance between signal emitting-source and signal receiver, be the projection of the relative receiver travelling speed of satellite on signal incident direction, this is the amount that can solve.The information such as the satellite orbit that the method that the present invention adopts is utilized gained behind location just and customer location, speed are predicted the Doppler shift of satellite and receiver relative motion generation, and by Kalman filtering algorithm, eliminate the impact of this Doppler shift, thereby can design carrier loop is operated under narrower noise bandwidth, reduced the noise of carrier loop, promote the degree of accuracy of carrier loop signal trace, reached the effect that high sensitivity is followed the tracks of.

Summary of the invention

It is a kind of based on the auxiliary carrier wave tracing method of many information fusion and system that technical purpose of the present invention is to provide, utilize the relative users' of information calculating satellite such as resulting satellite orbit and customer location speed behind receiver location radial velocity, and then the Doppler shift of prediction reception carrier, by receiver carrier loop, obtained the actual measured value of Doppler shift simultaneously, adopt again the method for Kalman filtering to proofread and correct processing to Doppler shift measurement remnants, optimum Doppler shift after proofreading and correct is fed back to track loop, thereby meeting the filtering bandwidth that reduces signal trace loop under high dynamic prerequisite, and then the measurement noise in reduction loop, improve signal to noise ratio (S/N ratio), entire system block diagram of the present invention can be with reference to accompanying drawing 1.

For achieving the above object, technical scheme of the present invention comprises three partial contents, is specially:

First is the radial velocity that obtains the relative receiver motion of satellite, thereby can predict the Doppler frequency being produced by satellite motion.Travelling speed is v ^(s)satellite launch frequency be f, the carrier wave that respective wavelength is λ (as L1 signal), and the speed of receiver is v, the Doppler shift of the satellite-signal that this receiver receives is so:

$f_d=\frac{(v-v^{\left(s\right)})\·l^{\left(s\right)}}{\mathrm{\λ}}\≈-\frac{(v^{\left(s\right)}-v)\·l^{\left(s\right)}}{\mathrm{\λ}}=\frac{(-\stackrel{\·}{r})}{\mathrm{\λ}}=\frac{-u}{\mathrm{\λ}}---\left(1\right)$

L wherein ^(s)for the unit measurement vector of satellite at receiver place, represent satellite and the derivative of receiver geometric distance r to the time, when satellite relative with receiver away from time, value is being for just, for negative.U is the size of the relative user's radial velocity of satellite.

By the known hypothesis of (1) formula k Doppler shift constantly, be f _k, k+1 Doppler shift predicted value is constantly

$f_{k+1}=f_k+\mathrm{\Δ}{f}_d=f_k+\frac{\mathrm{\Δu}}{\mathrm{\λ}}---\left(2\right)$

Second portion is the actual measurement Doppler frequency that obtains receiver.Receiver carrier tracking loop route frequency mixer, relevant and coherent integration device, Discr., loop filter and carrier number controlled oscillator (DCO) form, and adopt I/Q demodulation method to help the carrier wave of input signal to peel off the task with phase demodulation.After the preliminary examination operations such as input digital medium-frequency signal is through I/Q mixing, relevant and coherent integration, obtain two-way coherent integration energy and deliver to carrier wave ring Discr..The phase difference of loop filter to Discr. output _eor difference on the frequency f _ecarry out filtering, obtain filtering result and be frequency adjustment word M and deliver to DCO and regulate its output phase and frequency.Knownly according to DCO principle of work with respect to the Doppler shift of intermediate frequency, be now

$f_o=\frac{{\mathrm{Mf}}_c}{2^N}---\left(3\right)$

F wherein _cfor sampling clock frequency, the figure place that N is digital controlled oscillator, f _obe the actual measurement Doppler frequency of receiver.

Third part is Kalman filtering, obtains optimal estimation Doppler shift and feeds back.Here we introduce the system model of a discrete control procedure, and the variable quantity using the relative user path of satellite to speed is as system control variable.Because the optimum Doppler shift feeding back has comprised the dynamic of the relative user movement introducing of satellite, so the loop filter in receiver tracking passage can be used narrow noise bandwidth parameter instead, thereby reach the effect that improves tracking sensitivity.

Technique effect of the present invention is: with respect to traditional second order or three rank carrier tracking loops, the Doppler shift that the present invention brings satellite motion feeds back to track loop, eliminated the measurable part during dynamic stress exerts an influence, made track loop realize high robust.Owing to having eliminated the dynamic effects of the relative user movement of satellite, receiver loop can design under narrow noise bandwidth and work, and has reduced the noise of carrier loop, has promoted tracking sensitivity simultaneously.The kalman filter method adopting herein can dynamically regulate yield value, realizes the optimal estimation to feedback Doppler shift, thereby has higher commercial value.

Accompanying drawing explanation

Accompanying drawing 1 is entire system block diagram of the present invention.

Accompanying drawing 2 is realization flow figure of the present invention.

Accompanying drawing 3 solves satellite with respect to the schematic diagram of user's radially speed u (t) for the present invention.

The carrier wave ring design drawing that accompanying drawing 4 is used for the present invention.

Accompanying drawing 5 is that the present invention is a kind of based on the auxiliary carrier track apparatus structure schematic diagram of many information fusion.

Embodiment

Basic thought of the present invention is to build Kalman filter model according to the Doppler shift actual measured value of the Doppler shift being gone out by the relative user movement prediction of speed of satellite and the output of receiver inside carrier track loop; Gained is measured to remnants and process correction, optimum Doppler frequency estimation value after being proofreaied and correct feeds back to track loop and regulates, make receiver grasp in real time the up-to-date motion state of satellite, thereby copy exactly the satellite signal carrier phase place (or frequency) that will receive.

Provided by the present invention based on the auxiliary carrier wave tracing method of many information fusion and system below in conjunction with the drawings and specific embodiments detailed description, but be not construed as limiting the invention.

Accompanying drawing 2 is specific embodiment of the invention process flow diagram, as shown in Figure 2, specifically comprise following four-stage: the first stage: after receiver stable position, according to the satellite transit orbit information in satellite ephemeris and customer location velocity information, calculate satellite with respect to user's radial velocity size u (t), and then obtain Doppler shift predicted value.

Accompanying drawing 3, for the present invention solves satellite with respect to the schematic diagram of user's radially speed u (t), from accompanying drawing 3, completes behind location at receiver, and from satellite ephemeris and positioning result, we can obtain receiver location coordinate vector [x y z] ^twith velocity vector v=[v _xv _yv _z] ^t, the position coordinates vector [x of satellite n ⁽ⁿ⁾y ⁽ⁿ⁾z ⁽ⁿ⁾] ^tand the velocity vector of satellite $v^{\left(s\right)}{\left[\begin{array}{ccc}{v}_x^{\left(s\right)}& v_y^{\left(s\right)}& v_z^{\left(s\right)}\end{array}\right]}^T,$ According to above-mentioned information, solve satellite as follows with respect to the step of user's radially speed u (t):

Step 1. receiver is to the geometric distance r of satellite n ⁽ⁿ⁾for

$r^{\left(n\right)}=\left|\right|x^{\left(n\right)}-x\left|\right|=\sqrt{{(x^{\left(n\right)}-x)}^2+{(y^{\left(n\right)}-y)}^2+{(z^{\left(n\right)}-z)}^2}---\left(4\right)$

The measurement vector l of step 2. unit $\left(n\right)=\left[\begin{array}{c}{l}_x^{\left(n\right)}\\ l_y^{\left(n\right)}\\ l_z^{\left(n\right)}\end{array}\right]=\frac{-1}{r^{\left(n\right)}}\left[\begin{array}{c}{x}^{\left(n\right)-x}\\ y^{\left(n\right)}-y\\ z^{\left(n\right)-z}\end{array}\right]---\left(5\right)$

It is u (t)=(v to velocity vector that step 3. can obtain the relative user path of satellite by (5) formula ^(s)-v) l ⁽ⁿ⁾, its velocity magnitude u (t)=|| u (t) ||.

Obtaining radially after speed u (t), is measurable next Doppler shift constantly by formula (2).Subordinate phase: receiver inside carrier loop carries out phase demodulation (frequency discrimination) filtering to incoming carrier and local replica carrier wave, output Doppler shift actual measured value.

The carrier wave ring design drawing that accompanying drawing 4 is used for the present invention.Carrier wave ring workflow is described in summary of the invention.From accompanying drawing 4, carrier loop is closed-loop system, it is input as digital medium-frequency signal, loop filter output frequency regulates word M, after each renewal, can be kept in corresponding register, in the ppu of having no progeny from register, read this value and calculate current time the actual measurement Doppler shift value Z while being k _k.Its computing formula is as follows:

$Z_k=f_k=\frac{{\mathrm{Mf}}_c}{2^N}---\left(6\right)$

F wherein _cfor sampling clock frequency, N is the figure place of carrier wave number of rings controlled oscillator, Z _kbe the actual measurement Doppler frequency of receiver.Phase III: utilize Kalman filter correcting measuring remaining, obtain optimization Doppler estimated value.

First, we first will introduce the system of a discrete control procedure.This system can be described with a linear random differential equation:

X(k)＝AX(k-1)+BU(k-1)+W(k-1) (7)

Add the measured value of system:

Z(k)＝HX(k)+V(k) (8)

In upper two formulas, X (k) is k system state constantly, and U (k-1) is the k controlled quentity controlled variable to system constantly.A and B are systematic parameters, and for Multi-model System, they are matrix.Z (k) is k measured value constantly, and H is the parameter of measuring system, and for many measuring systems, H is matrix.W and V represent respectively the noise of process and measurement, and hypothesis is all white Gaussian noise here, and its covariance is respectively Q, R (we suppose that they do not change with system state change here).For the condition (linear random differential system, process and measurement are all white Gaussian noises) meeting above, Kalman filter is optimum message handler.In conjunction with the concrete condition of this single model, system model can abbreviation be:

$\left(k\right)=X(k-1)+\frac{U(k-1)}{\mathrm{\λ}}+W(k-1)$

$=X(k-1)+\frac{\mathrm{\Δu}(k-1)}{\mathrm{\λ}}+W(k-1)---\left(9\right)$

Z(k)＝X(k)+V(k) (10)

A=1 in this model, H=1, x (k) is k prediction Doppler shift constantly, and U (k-1) be k-1 moment satellite with respect to receiver radially rate variation amount, here U (k-1)=Δ u (k-1)=u _k-1-u _k-2, u _k-1for the radially speed of k-1 satellite constantly with respect to receiver.Z _kfor actual Doppler's observed reading,

We need utilize the process model of said system, predict the system of NextState.Suppose that present system state is k, according to the model of system, laststate that can be based on system and predict present status:

$X\left(k\right|k-1)=X(k-1|k-1)+\frac{\mathrm{\Δu}(k-1)}{\mathrm{\λ}}---\left(11\right)$

X (k|k-1) is the Doppler shift that utilizes laststate prediction, and X (k-1|k-1) is the Doppler shift of laststate optimum.

Till now, Kalman model system results is upgraded.Next upgrade the covariance corresponding to X (k|k-1).We represent covariance with P:

P(k|k-1)＝P(k-1|k-1)+Q (12)

In expression formula (12), P (k|k-1) is the covariance that X (k|k-1) is corresponding, and P (k-1|k-1) is the covariance that X (k-1|k-1) is corresponding, and Q is the covariance of systematic procedure.

Expression formula (11) and (12) are that the Doppler of present status predicts the outcome, and can be obtained the Doppler measurement value of present status by subordinate phase.In conjunction with Doppler's predicted value and Doppler measurement value, can obtain optimization Doppler's estimated value X (k|k) of present status k:

X(k|k)＝X(k|k-1)+Kg(k)(Z(k)-X(k|k-1)) (13)

Wherein Kg is kalman gain (Kalman Gain):

Kg (k)=P (k|k-1)/(P (k|k-1)+R) (14) till now, have obtained estimated value X (k|k) optimum under k state.In order to make Kalman filter constantly move, also need to upgrade the covariance of X under k state (k|k):

P(k|k)＝(1-Kg(k))P(k|k-1) (15)

When system enters k+1 state, P (k|k) is exactly the P (k-1|k-1) of formula (12).Like this, algorithm just can go down in autoregressive computing, and the X at every turn trying to achieve (k|k) is optimization Doppler's estimated value in this moment.In order to make Kalman filter start working, Kalman's initial value in two zero moment need to be set, be X (0|0) and P (0|0).X (0|0) can be by calculate, utilize the movement rate of the relative receiver of satellite of trying to achieve for the first time after locating successfully to calculate.For P (0|0), at will establish a value just passable, but generally do not get 0, because may make like this Kalman filter think that given X (0|0) is system optimal, thereby algorithm can not be restrained.

Fourth stage: optimization Doppler estimated value X (k|k) is converted into carrier frequency and regulates word Mk to feed back to carrier wave ring DCO, its mutual relationship is shown below:

$M_k=\frac{X\left(k\right|k)*2^N}{f_c}---\left(16\right)$

F wherein _cfor sampling clock frequency, the figure place that N is digital controlled oscillator.

The apparatus structure schematic diagram that accompanying drawing 5 is the embodiment of the present invention, the present invention can realize with this device, but is not limited to accompanying drawing 5 shown devices.Whole device comprises: receiving antenna, radio-frequency module, GPS Base-Band Processing passage, processor and process software.Wherein, receiving antenna is responsible for the reception of signal, the amplification of radio-frequency module settling signal, filtering and down coversion, and the analog-to-digital conversion of signal, and to GPS Base-Band Processing passage output digital medium-frequency signal and sampled clock signal.GPS Base-Band Processing passage comprises trapping module, tracking module, bit synchronization and frame synchronization module and data demodulation module, completes to catch, follow the tracks of and demodulate navigation message for digital medium-frequency signal.Process software is divided into ephemeris processing and PVT resolves, Doppler's prediction and three parts of Kalman filtering, and specific algorithm is realized the elaboration in relevant each stage of invention realization flow that can see above.The Doppler shift measured value that is input as navigation message, Satellite Phase measured value and loop filter output of process software, and be output as Doppler shift optimal estimation value.Processor is responsible for moving process software and detection, control GPS Base-Band Processing passage.

5 shown device structural representations by reference to the accompanying drawings, the invention process flow process is: the intermediate-freuqncy signal of GPS Base-Band Processing passage received RF module output, processor is by the initiation parameter of bus configuration Base-Band Processing passage modules, the acquisition and tracking of Base-Band Processing passage settling signal with synchronize after obtain carrier phase measurement value and code phase measuring value and navigation message, and be then stored in register with the sampling period sampling of fixing, to processor, produce and interrupt simultaneously.In processor response, have no progeny, by bus, read phase measurement and the navigation message in register, ephemeris processing in process software and PVT resolve part and obtain the information such as satellite position speed and customer location speed, then dope Doppler shift value now by Doppler's predicted portions.Simultaneously the carrier wave ring module in GPS Base-Band Processing passage is carried out phase demodulation filtering processing to reception carrier signal and local replica carrier signal, and output Doppler shift actual measured value is now stored in register, and wait processor is read away.Kalman filtering in process software partly completes for the filtering of residual error between the Doppler shift predicted value calculating and the measured value read from register and processes, and the Real-time solution optimal estimation value that goes out Doppler shift is converted into frequency adjustment word and feeds back to the digital controlled oscillator in carrier wave ring, be used for regulating the carrier wave of local replica.

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

Claims (7)

1. one kind based on the auxiliary carrier wave tracing method of many information fusion and system, specifically based on satellite orbit and customer location, the carrier tracking loop method for designing of the information such as speed, it is characterized in that, comprise three parts: according to satellite, with respect to user's radial velocity, predict next Doppler shift constantly, output by receiver carrier wave ring module intermediate ring road wave filter obtains Doppler shift actual observed value, thereby and utilize Kalman filter to proofread and correct Doppler shift measurement residual error to obtain optimum Doppler frequency estimation value and feed back to loop digital controlled oscillator, wherein, the calculating of the relative user's radial velocity of satellite comprises following two processes:

1) by satellite ephemeris, calculated position coordinates and the travelling speed vector of satellite.By the location of receiver user, the result that tests the speed, obtain customer location coordinate and velocity vector.

2) according to 1) in the satellite and the customer location coordinate that solve calculate satellite with respect to user's unit measurement vector, the dot product of this unit measurement vector user movement velocity vector relative to satellite is satellite with respect to user's radial velocity.

2. the method for claim 1, is characterized in that, obtains after the radial velocity of satellite with respect to user, the carrier doppler frequency displacement that utilizes Doppler shift computing formula to predict to receive.

3. the method for claim 1, is characterized in that, adopts a kind of typical carrier wave ring design, the loop filter output Doppler shift observed reading in receiver carrier wave ring module.

4. the method for claim 1, is characterized in that, sets up the Kalman filter model of Doppler shift: using satellite with respect to user's radially rate variation amount as system control variable, obtain next Doppler shift predicted value constantly; Using the Doppler shift of receiver carrier wave ring module intermediate ring road wave filter output as actual measured value; Utilize Kalman filtering algorithm by the difference between Doppler shift predicted value and measured value, measure remnants, process correction, the optimum Doppler frequency estimation value after being proofreaied and correct.

5. the method for claim 1, is characterized in that: the optimum Doppler frequency estimation value Real-time Feedback after proofreading and correct is regulated to track loop digital controlled oscillator, make receiver grasp the up-to-date motion state of satellite.

6. based on the auxiliary carrier track device of many information fusion, it is characterized in that, described device comprises: GPS Base-Band Processing passage and process software; Wherein,

Described GPS Base-Band Processing passage, for obtaining phase measurement and the navigation message of each satellite, carrier wave ring output Doppler shift measured value wherein;

Described process software, it is input as each Satellite Phase measured value, navigation message and Doppler shift measured value, for obtaining optimum Doppler frequency estimation value, feeds back to copying of carrier wave number of rings controlled oscillator adjusting local carrier.

7. device according to claim 6, is characterized in that, described process software is divided into ephemeris processing and resolves with PVT, Doppler's prediction and three parts of Kalman filtering, and its processing procedure comprises:

According to each satellite carrier phase place and code phase measuring value and navigation message, calculate satellite and user's position and speed information; By the many information of gained, solve the relative user path of satellite to speed; By gained radially speed solve Doppler shift predicted value; Utilize Kalman filtering algorithm to proofread and correct Doppler shift measurement residual error, finally obtain Doppler shift optimal estimation value.