CN105204036A - Tracking loop design method based on multi-path inhibiting signals - Google Patents

Abstract

The invention relates to a method for reducing errors in the process of demodulating navigation messages, in particular to a method for designing a tracking loop based on suppressing multipath signals, comprising the following steps: given the satellite navigation signal received by the antenna of the navigation receiver, the navigation receiver The received satellite navigation signal is digitally down-converted to obtain an intermediate frequency signal, and the intermediate frequency signal is quantized to obtain a quantized signal; the quantized signal is passed through a filter and autocorrelation operation, and the sequence input to the equalizer can be obtained; after the navigation receiver completes the acquisition of the intermediate frequency signal , the intermediate frequency signal is respectively calculated with the I branch carrier and the Q branch carrier output by the carrier tracking loop to complete the stripping of the carrier; the intermediate frequency signal that completes the stripping of the carrier is channel compensated by inputting an equalizer with a sequence, and finally enters the code tracking loop respectively Perform correlation tracking with the carrier tracking loop to realize demodulation of navigation messages. The tracking loop design method provided by the invention makes the tracking effect of the navigator more accurate and improves the positioning accuracy.

Description

A Tracking Loop Design Method Based on Suppressing Multipath Signals

technical field

The invention relates to a method for reducing errors in the process of demodulating navigation messages, in particular to a tracking loop design method based on suppressing multipath signals.

Background technique

As one of the fastest growing information industries, the satellite navigation industry has received more and more attention from the state. As a kind of information resource that can be shared by countless users, satellite navigation signal needs a satellite receiver capable of determining positioning information to capture and track navigation satellite signals. Therefore, the navigation receiver plays a vital role in the process of positioning solution.

From the current research, it can be concluded that the multipath effect has become the main source of error in the measurement of the navigation receiver, and it has time-varying and environmental characteristics. The harm of multipath effect will first distort the ranging code and navigation data modulated onto the navigation signal, and also cause the phase distortion of the carrier; it will also affect the quality of each measurement data; the most serious situation is that multiple The signal on the path will cause the loop of the receiver to lose lock.

Contents of the invention

In order to solve the problem that there will be errors in the tracking loop of the navigation receiver under the interference of multipath signals, the present invention provides an equalization technology in the tracking loop. The equalizer coefficient update adopts a CMA algorithm based on suppressing multiple Tracking loop design method for path signal.

The present invention is realized by adopting the following technical solutions: a tracking loop design method based on suppressing multipath signals, comprising the following steps:

Given the satellite navigation signal s ⁽ⁱ⁾ (t) received by the navigation receiver antenna, In the formula, i represents the serial number of the satellite, the subscripts I and Q are two branches respectively, A represents the signal amplitude, C represents the ranging code, D represents the data code modulated on the pseudo-code, f ₀ represents the carrier frequency, Represents the initial phase of the carrier, N'(t) represents the noise signal;

The satellite navigation signal s ⁽ⁱ⁾ (t) is digitally down-converted to obtain the intermediate frequency signal s ⁽ⁱ⁾ '(t), ${{\mathrm{the\; s}}^{\left(i\right)}}^{\′}\left(t\right)=\underset{i=0}{\overset{N}{\mathrm{\Σ}}}{\∂}_{i}AC(t-{\mathrm{\τ}}_i)\mathrm{D.}(t-{\mathrm{\τ}}_i)co\mathrm{the\; s}\[2\mathrm{\π}\left(f_{If}+f_d\right)t+{\mathrm{\φ}}_i\]+N^{\′}\left(t\right),$ In the formula, i=0 means satellite direct signal, i≠0 means multipath signal of other paths, N is the number of multipath signal, A means signal amplitude, Represents the signal amplitude fading coefficient, D(t) represents the data code of the navigation message, C(t) represents the C/A code, τ _i represents the chip delay, f _IF represents the frequency of the intermediate frequency signal, and f _d represents the Doppler frequency offset , Represents the i-th signal phase, N'(t) represents the noise signal;

Quantize the intermediate frequency signal s ⁽ⁱ⁾ '(t) to obtain the quantized signal s[n], where t _s is the sampling interval;

After the quantized signal s[n] undergoes filter and autocorrelation operations, the sequence W(n+1) input to the equalizer can be obtained, and the signal equalization is performed on this basis. The iterative formula of W(n+1) is as follows:

$\mathrm{<span\; class="notranslate">\; W</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; W</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; z</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&lsqb;</span>\mathrm{<span\; class="notranslate">\; z</span>}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; |</span>\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span>{<span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&rsqb;</span>{\mathrm{<span\; class="notranslate">\; x</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ,</span>$

$f\left(\mathrm{no}\right)=\left\{\begin{array}{cc}1,& \mathrm{sgn}\&lsqb;z{\left(\mathrm{no}\right)}^2-{\left|\widehat{\mathrm{\&alpha;}}\left(\mathrm{no}\right)\right|}^2\&rsqb;=\mathrm{sgn}\&lsqb;z{\left(\mathrm{no}\right)}^2-R\&rsqb;\\ 0,& \mathrm{sgn}\&lsqb;z{\left(\mathrm{no}\right)}^2-{\left|\widehat{\mathrm{\&alpha;}\left(\mathrm{no}\right)}\right|}^2\&rsqb;\&NotEqual;\mathrm{sgn}\&lsqb;z{\left(\mathrm{no}\right)}^2-R\&rsqb;\end{array}\right.;$ W(n+1) represents the equalization sequence at time n+1, W(n) represents the equalization sequence at time n, α represents the equalization coefficient, z(n) represents the signal quantization sequence at time n, Represents the modulus of the signal quantization sequence at n moments, X ^* (n) represents the satellite signal, and R represents the threshold;

After the navigation receiver completes the acquisition of the intermediate frequency signal, the intermediate frequency signal enters the tracking loop to start working, and the intermediate frequency signal is respectively calculated with the I branch carrier and the Q branch carrier output by the carrier tracking loop to complete the stripping of the carrier;

The intermediate frequency signal that has been stripped off the carrier is channel compensated by an equalizer with a sequence W(n+1), and finally enters the code tracking loop and carrier tracking loop for correlation tracking to realize demodulation of navigation messages.

This loop can effectively weaken the multipath effect. When there is multipath interference in the channel, the code tracking accuracy of the equalization algorithm introduced in the tracking loop is higher than that of the typical early and late DLL loop, thereby improving the pseudo-range The measurement accuracy can improve the positioning accuracy of the navigation receiver.

Description of drawings

Figure 1 Classic code tracking loop block diagram.

Figure 2 is a block diagram of a classic carrier tracking loop.

Fig. 3 is a block diagram of the receiver tracking loop of the present invention.

Detailed ways

A tracking loop design method based on suppressing multipath signals, comprising the following steps:

Given the satellite navigation signal s ⁽ⁱ⁾ (t) received by the navigation receiver antenna, In the formula, i represents the serial number of the satellite, the subscripts I and Q are two branches respectively, A represents the signal amplitude, C represents the ranging code, D represents the data code modulated on the pseudo-code, f ₀ represents the carrier frequency, Represents the initial phase of the carrier, N'(t) represents the noise signal;

The satellite navigation signal s ⁽ⁱ⁾ (t) received by the single-frequency civil navigation receiver is digitally down-converted to obtain the intermediate frequency signal s ⁽ⁱ⁾ '(t), ${{\mathrm{the\; s}}^{\left(i\right)}}^{\&prime;}\left(t\right)=\underset{i=0}{\overset{N}{\mathrm{\&Sigma;}}}{\&part;}_{i}AC(t-{\mathrm{\&tau;}}_i)\mathrm{D.}(t-{\mathrm{\&tau;}}_i)co\mathrm{the\; s}\&lsqb;2\mathrm{\&pi;}\left(f_{If}+f_d\right)t+{\mathrm{\&phi;}}_i\&rsqb;+N^{\&prime;}\left(t\right),$ In the formula, i=0 means satellite direct signal, i≠0 means multipath signal of other paths, N is the number of multipath signal, A means signal amplitude, Represents the signal amplitude fading coefficient, D(t) represents the data code of the navigation message, C(t) represents the C/A code, τ _i represents the chip delay, f _IF represents the frequency of the intermediate frequency signal, and f _d represents the Doppler frequency offset , Represents the i-th signal phase, N'(t) represents the noise signal;

Quantize the intermediate frequency signal s ⁽ⁱ⁾ '(t) to obtain the quantized signal s[n], where t _s is the sampling interval;

After the quantized signal s[n] undergoes filter and autocorrelation operations, the sequence W(n+1) input to the equalizer can be obtained, and the signal equalization is performed on this basis. The iterative formula of W(n+1) is as follows:

$\mathrm{<span\; class="notranslate">\; W</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; W</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; z</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&lsqb;</span>\mathrm{<span\; class="notranslate">\; z</span>}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; |</span>\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span>{<span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&rsqb;</span>{\mathrm{<span\; class="notranslate">\; x</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ,</span>$

$f\left(\mathrm{no}\right)=\left\{\begin{array}{cc}1,& \mathrm{sgn}\&lsqb;z{\left(\mathrm{no}\right)}^2-{\left|\widehat{\mathrm{\&alpha;}}\left(\mathrm{no}\right)\right|}^2\&rsqb;=\mathrm{sgn}\&lsqb;z{\left(\mathrm{no}\right)}^2-R\&rsqb;\\ 0,& \mathrm{sgn}\&lsqb;z{\left(\mathrm{no}\right)}^2-{\left|\widehat{\mathrm{\&alpha;}\left(\mathrm{no}\right)}\right|}^2\&rsqb;\&NotEqual;\mathrm{sgn}\&lsqb;z{\left(\mathrm{no}\right)}^2-R\&rsqb;\end{array}\right.;$ W(n+1) represents the equalization sequence at time n+1, W(n) represents the equalization sequence at time n, _α represents the equalization coefficient, z(n) represents the signal quantization sequence at time n, Represents the modulus of the signal quantization sequence at n moments, X ^* (n) represents the satellite signal, and R represents the threshold;

After the navigation receiver completes the acquisition of the intermediate frequency signal, the intermediate frequency signal enters the tracking loop to start working, and the intermediate frequency signal is respectively calculated with the I branch carrier and the Q branch carrier output by the carrier tracking loop to complete the stripping of the carrier;

The intermediate frequency signal that has been stripped off the carrier is channel compensated by an equalizer with a sequence W(n+1), and finally enters the code tracking loop and carrier tracking loop for correlation tracking to realize demodulation of navigation messages.

Claims (1)

1. a tracking loop design method based on suppressing multipath signal, it is characterized in that comprising the following steps: Given the satellite navigation signal s ⁽ⁱ⁾ (t) received by the navigation receiver antenna, In the formula, i represents the serial number of the satellite, the subscripts I and Q are two branches respectively, A represents the signal amplitude, C represents the ranging code, D represents the data code modulated on the pseudo-code, f ₀ represents the carrier frequency, Represents the initial phase of the carrier, N'(t) represents the noise signal; The satellite navigation signal s ⁽ⁱ⁾ (t) is digitally down-converted to obtain the intermediate frequency signal s ⁽ⁱ⁾ '(t), $S^{\left(i\right)}\&prime;\left(t\right)=\underset{i=0}{\overset{N}{\&Sigma;}}{\&part;}_{i}AC(t-{\mathrm{\&tau;}}_i)\mathrm{D.}(t-{\mathrm{\&tau;}}_i)co\mathrm{the\; s}\&lsqb;2\mathrm{\&pi;}(f_{If}+f_d)t+{\mathrm{\&phi;}}_i\&rsqb;+N^{\&prime;}\left(t\right),$ In the formula, i=0 means satellite direct signal, i≠0 means multipath signal of other paths, N is the number of multipath signal, A means signal amplitude, Represents the signal amplitude fading coefficient, D(t) represents the data code of the navigation message, C(t) represents the C/A code, τ _i represents the chip delay, f _IF represents the frequency of the intermediate frequency signal, and f _d represents the Doppler frequency offset , Represents the i-th signal phase, N'(t) represents the noise signal; Quantize the intermediate frequency signal s ⁽ⁱ⁾ '(t) to obtain the quantized signal s[n], where t _s is the sampling interval; After the quantized signal s[n] undergoes filter and autocorrelation operations, the sequence W(n+1) input to the equalizer can be obtained, and the signal equalization is performed on this basis. The iterative formula of W(n+1) is as follows: $\mathrm{<span\; class="notranslate">\; W</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; =</span>\mathrm{<span\; class="notranslate">\; W</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; \&alpha;</span>}\mathrm{<span\; class="notranslate">\; f</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span>\mathrm{<span\; class="notranslate">\; z</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&lsqb;</span>\mathrm{<span\; class="notranslate">\; z</span>}{<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; |</span>\stackrel{<span\; class="notranslate">\; ^</span>}{\mathrm{<span\; class="notranslate">\; a</span>}}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span>{<span\; class="notranslate">\; |</span>}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&rsqb;</span>{\mathrm{<span\; class="notranslate">\; x</span>}}^{<span\; class="notranslate">\; *</span>}<span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; no</span>}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; ,</span>$ $f\left(\mathrm{no}\right)=\left\{\begin{array}{cc}1,& \mathrm{sgn}\&lsqb;z{\left(\mathrm{no}\right)}^2-{\left|\widehat{\mathrm{\&alpha;}}\left(\mathrm{no}\right)\right|}^2\&rsqb;=\mathrm{sgn}\&lsqb;z{\left(\mathrm{no}\right)}^2-R\&rsqb;\\ 0,& \mathrm{sgn}\&lsqb;z{\left(\mathrm{no}\right)}^2-{\left|\widehat{\mathrm{\&alpha;}\left(\mathrm{no}\right)}\right|}^2\&rsqb;\&NotEqual;\mathrm{sgn}\&lsqb;z{\left(\mathrm{no}\right)}^2-R\&rsqb;\end{array}\right.,$ W(n+1) represents the equalization sequence at time n+1, W(n) represents the equalization sequence at time n, α represents the equalization coefficient, z(n) represents the signal quantization sequence at time n, Represents the modulus of the signal quantization sequence at n moments, X ^* (n) represents the satellite signal, and R represents the threshold; After the navigation receiver completes the acquisition of the intermediate frequency signal, the intermediate frequency signal enters the tracking loop to start working, and the intermediate frequency signal is respectively calculated with the I branch carrier and the Q branch carrier output by the carrier tracking loop to complete the stripping of the carrier; The intermediate frequency signal that has been stripped off the carrier is channel compensated by an equalizer with a sequence W(n+1), and finally enters the code tracking loop and carrier tracking loop for correlation tracking to realize demodulation of navigation messages.