CN102253396A - High dynamic global positioning system (GPS) carrier loop tracking method - Google Patents

Abstract

The invention relates to a high dynamic global positioning system (GPS) carrier loop tracking method, which comprises the following steps that: a frequency locked loop (FLL) discriminator and a Kalman filter algorithm are used in an algorithm functionally; a four quadrant arc tangent discriminator is used in the FLL discriminator and is optimal at a high signal-to-noise ratio, and the slope is irrelevant to signal amplitude; and a phase difference is estimated by Kalman filtering. In a carrier tracking loop of the Kalman filtering, an output phase difference of a high-linearity four quadrant arc tangent discriminator is used as a measurement value, the phase difference is estimated by Kalman filtering, and the sensitivity of the carrier tracking loop is improved.

Description

A kind of high dynamic GPS carrier wave ring tracking

Technical field

The present invention relates to a kind of high dynamic GPS carrier loop track algorithm, can be applicable to the GPS software receiver under the high dynamic environment, realize the tracking of satellite-signal under the high dynamic environment.

Technical background

As far back as the latter stage fifties, in the world after first artificial satellite successful launch, people just begin the research that utilizes satellite to position and navigate, till today, it is the most ripe and extensive to count the GPS navigation system development, and economic benefit that its application industry obtained and social benefit also increase sharply, especially in the Gulf War and Kosovo War, GPS has brought into play crucial effects, and this has more evoked the upsurge of the exploitation of many countries, applying GPS.

China more developed country evening aspect the satellite navigation system exploitation, and American-European countries such as the U.S. are for safeguarding national security and safeguarding the needs of military power, relevant high dynamic technology is taked the blockade policy to China.At present GPS has following obvious deficiency in the application of China: 1. at home on the GPS application product market, the considerable part product is arranged directly from abroad; 2. mainly be the secondary development of carrying out product; 3. in mainly stressing, the applied research of low dynamic environment, the research in high dynamic application field relates to seldom.Low dynamically, in dynamically and height dynamically be that the movement velocity of carrier is according to target concluded: hang down dynamic receiver, its carrier movement speed is several meters to tens meters of per seconds; Middle dynamic receiver, movement velocity is 100m/s to 1km/s; High dynamic receiver, movement velocity are generally greater than 1km/s.Owing to above reason, China is developing the Big Dipper navigation positioning system of oneself, and this system will finally develop into worldwide navigation by present area navigation.The foundation of this system and operation, inevitable requirement scientific worker develops various types of navigation neceivers, and the performance study of the track loop of navigation neceiver under high dynamic condition must be the emphasis of research and development.In addition,, make the principle of work of the high dynamic subscriber's machine of GPS clear because external a lot of weapons have all equipped the high dynamic subscriber's machine of GPS, also can the high dynamic subscriber's machine of GPS provides theoretical foundation in order to design efficiently.

For the needs of national security, in the dependence of breaking away from aspect the satellite navigation its state, we should study and grasp the tracking technique of the navigation neceiver under the high dynamic condition, for the satellite navigation system of China's exploitation oneself provides technical support.

Summary of the invention

Technology of the present invention is dealt with problems and is: overcome existing technical deficiency, a kind of new high dynamic GPS track algorithm is provided.This algorithm has merged PLL/FLL algorithm and Kalman's algorithm, with the input of the output signal of FLL phase detector as Kalman filtering algorithm, go out carrier phase error through Kalman Filter Estimation, through feedback carrier maker then behind the loop filtering, to adjust the carrier frequency of local reproduction.

1, technical solution of the present invention is: a kind of high dynamic GPS carrier wave ring tracking is characterized in that may further comprise the steps:

(1) on function, this algorithm had both utilized the FLL Discr., had adopted Kalman filtering algorithm again;

(2) the FLL Discr. has adopted four-quadrant arc tangent Discr., and this Discr. is in high the best during signal to noise ratio (S/N ratio) where, and slope and signal amplitude are irrelevant; Utilize Kalman filtering that phase differential is estimated.

2, a kind of high dynamic GPS carrier wave ring tracking according to claim 1 is characterized in that both having utilized the FLL Discr., has adopted Kalman filtering algorithm again:

(a) intermediate-freuqncy signal of input is peeled off the C/A sign indicating number, by intersecting, obtain in-phase signal and orthogonal signal then with the output of carrier wave maker;

(b) with the input as the FLL phase detector of in-phase signal and orthogonal signal, by the phase detector phase demodulation, the result sends into Kalman filter with gained;

(c), set up the state equation and the observation equation of carrier phase with the observed reading of phase detector output as Kalman filter;

(d) with Kalman filter output through feedback carrier maker then behind the loop filtering, to adjust the carrier frequency of local reproduction.

Advantage of the present invention is to have merged FLL Discr. and Kalman filtering algorithm, thereby at first obtain phase delta θ (k) by the FLL phase detector by homophase and quadrature signal component to the intermediate frequency input, through behind the phase detector, phase place is only relevant with Doppler frequency, make that calculating is convenient and simple when estimating, by Kalman filtering (KF) algorithm phase place, its derivative (being Doppler frequency) and Doppler frequency rate of change are estimated, promptly set up the state vector of x (k)=[Δ θ (k) Δ ω (k) Δ α (k)].The output signal of Kalman filter feeds back to the carrier wave maker as phase compensation value through loop filtering, adjusts the frequency of local reproduction carrier wave, is the frequency of frequency lock input signal carrier wave.Selected for use linear four phase difference outputs of limitting the arc tangent Discr. mutually preferably to utilize Kalman filtering that phase differential is estimated in the carrier tracking loop of the Kalman filtering that the present invention is used, improved the sensitivity of carrier tracking loop as measuring value.

Description of drawings

Fig. 1 is a The general frame of the present invention;

Fig. 2 is a discrete linear systems;

Fig. 3 is discrete linear simplified system;

Fig. 4 is a loop filter.

Embodiment

As shown in Figure 1, a kind of high dynamic GPS tracking may further comprise the steps:

(a) intermediate-freuqncy signal of input is peeled off the C/A sign indicating number, by intersecting, obtain in-phase signal and orthogonal signal then with the output of carrier wave maker.

(b) with the input as the FLL phase detector of in-phase signal and orthogonal signal, by the phase detector phase demodulation, the result sends into Kalman filter with gained.FLL phase detector formula is:

$D_{\mathrm{FLL}}=\frac{{\tan }^{-1}\left(\frac{I_{E,1}\×Q_{E,2}-I_{E,2}\×Q_{E,1}}{I_{E,1}\×I_{E,2}+Q_{E,1}\×Q_{E,2}}\right)}{t_2-t_1}---\left(1\right)$

Wherein, I _{E, 1}, Q _{E, 1}Expression t ₁Sampling constantly, same I _{E, 2}, Q _{E, 2}Expression is moment t after a while ₂Sampling, the two adjacent sampling should be in same data bit time district.

(c) with the observed reading of phase detector output as Kalman filter, set up the state equation and the observation equation of carrier phase, as follows:

X _k＝Φ _k，k-1X _k-1+w _k (2)

Z _k＝H _kX _k+v _k (3)

Wherein, first formula is the phase differential state equation, X _kFor by estimated state amount, Φ _{K, k-1}Be a step transition matrix of phase state amount, w _kBe system noise; Second formula is for measuring equation, Z _kBe phase-shift discriminator measured value, H _kPhase-shift discriminator is measured battle array, v _kFor measuring noise matrix; W wherein _kAnd v _kVariance be respectively Q _kAnd R _k

The Kalman filtering flow process of carrier loop is:

1, computing mode one-step prediction:

${\hat{X}}_{k,k-1}={\mathrm{\Φ}}_{k,k-1}{\hat{X}}_k---\left(4\right)$

2, calculate phase differential state estimation value:

${\hat{X}}_k={\mathrm{\Φ}}_{k,k-1}{\hat{X}}_{h-1}+K_k(Z_k-H_k{\hat{X}}_{k,k-1})---\left(5\right)$

3, computer card Kalman Filtering gain:

$K_k=P_{k,k-1}{H}_k^T{[H_k{P}_{k,k-1}{H}_k^T+R_k]}^{-1}---\left(6\right)$

4, calculate the one-step prediction covariance matrix:

$P_{k,k-1}={\mathrm{\Φ}}_{k,k-1}{P}_{k-1}{\mathrm{\Φ}}_{k,k-1}^T+Q_k---\left(7\right)$

5, calculate square error:

P _k＝(I-K _kH _k)P _k，k-1 (8)

Wherein, K _kBe kalman gain matrix, reach minimum for making estimated mean-square; P _kFor the system model error causes, the reflection estimated accuracy; Error between expression measured value and the model predication value.

(d) with Kalman filter output through feedback carrier maker then behind the loop filtering, to adjust the carrier frequency of local reproduction.

The loop filter design:

The loop filter that this algorithm adopts is a second order, its block diagram as shown in Figure 2:

Now Fig. 2 is simplified to Fig. 3

The transport function of second-order loop filter is:

$F\left(z\right)=\frac{({\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="HDA0000066984480000012.png,HDA0000066984480000022.png"\; state="\{\{state\}\}">C</figure-callout>}}_1+C_2)-C_1{Z}^{-1}}{1-Z^{-1}}---\left(9\right)$

$N\left(z\right)=\frac{k_0{z}^{-1}}{1-z^{-1}}---\left(10\right)$

The concrete mechanism of F (z) is illustrated in fig. 3 shown below

The transfer function of second-order loop filter is:

$H_1\left(z\right)=\frac{(4{\mathrm{\&xi;w}}_n+{\left(w_{n}T\right)}^2)+2{\left(w_{n}T\right)}^2{z}^{-1}+({\left(w_{n}T\right)}^2-4{\mathrm{\&xi;w}}_{n}T)z^{-2}}{(4+4{\mathrm{\&xi;w}}_n+{\left(w_{n}T\right)}^2)+(2{\left(w_{n}T\right)}^2-8)z^{-1}+(4-4{\mathrm{\&xi;w}}_n+{\left(w_{n}T\right)}^2)z^{-2}}---\left(11\right)$

Get by Fig. 4

$H\left(z\right)=\frac{K_{d}F\left(z\right)N\left(z\right)}{1+K_{d}F\left(z\right)N\left(z\right)}$

$=\frac{K_0{K}_d({\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="HDA0000066984480000012.png,HDA0000066984480000022.png"\; state="\{\{state\}\}">C</figure-callout>}}_1+C_2)z^{-1}-K_0{K}_d{C}_1{z}^{-2}}{1+\left(K_0{K}_d({\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="HDA0000066984480000012.png,HDA0000066984480000022.png"\; state="\{\{state\}\}">C</figure-callout>}}_1+C_2)\right)z^{-1}+(1-K_0{K}_d{C}_1)z^{-2}}---\left(12\right)$

Formula (11) and (12) contrast can be got

${\mathrm{<figure-callout\; id="1"\; label="C"\; filenames="HDA0000066984480000012.png,HDA0000066984480000022.png"\; state="\{\{state\}\}">C</figure-callout>}}_1=\frac{1}{K_0{K}_d}\frac{8{\mathrm{\&xi;w}}_{n}T}{4+4{\mathrm{\&xi;w}}_{n}T+{\left(w_{n}T\right)}^2}---\left(13\right)$

${\mathrm{<figure-callout\; id="2"\; label="C"\; filenames="HDA0000066984480000012.png"\; state="\{\{state\}\}">C</figure-callout>}}_2=\frac{1}{K_0{K}_d}\frac{4{\left(w_{n}T\right)}^2}{4+4{\mathrm{\&xi;w}}_{n}T+{\left(w_{n}T\right)}^2}---\left(14\right)$

Formula (13) is crucial formula with formula (14), and the parameter modification theoretical foundation is provided when realizing for programming.In the formula, K ₀K _dBe loop gain, ξ is a damping ratio, w _nIt is the nature frequency.

Claims (2)

1. one kind high dynamic GPS carrier wave ring tracking is characterized in that may further comprise the steps:

(1) on function, this algorithm had both utilized the FLL Discr., had adopted Kalman filtering algorithm again;

(2) the FLL Discr. has adopted four-quadrant arc tangent Discr., and this Discr. is in high the best during signal to noise ratio (S/N ratio) where, and slope and signal amplitude are irrelevant; Utilize Kalman filtering that phase differential is estimated.

2. a kind of high dynamic GPS carrier wave ring tracking according to claim 1 is characterized in that both having utilized the FLL Discr., has adopted Kalman filtering algorithm again:

(a) intermediate-freuqncy signal of input is peeled off the C/A sign indicating number, by intersecting, obtain in-phase signal and orthogonal signal then with the output of carrier wave maker;

(b) with the input as the FLL phase detector of in-phase signal and orthogonal signal, by the phase detector phase demodulation, the result sends into Kalman filter with gained;

(c), set up the state equation and the observation equation of carrier phase with the observed reading of phase detector output as Kalman filter;

(d) with Kalman filter output through feedback carrier maker then behind the loop filtering, to adjust the carrier frequency of local reproduction.

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