CN103217696A - Navigation signal equivalent carrier-to-noise ratio computing method based on spread spectrum pseudo code discrete spectrum characteristics - Google Patents

Abstract

The invention relates to a navigation signal equivalent carrier-to-noise ratio computing method based on spread spectrum pseudo code discrete spectrum characteristics. The navigation signal equivalent carrier-to-noise ratio computing method based on the spread spectrum pseudo code discrete spectrum characteristics is characterized by comprising the following steps: firstly, the power spectral density of a navigation signal is computed; then the power spectral density of a narrow-band interference signal is computed; and lastly, an equivalent carrier-to-noise ratio is computed. The navigation signal equivalent carrier-to-noise ratio computing method is specific to a narrow-band interference environment and based on the spread spectrum pseudo code discrete spectrum characteristics. Due to the fact that the equivalent carrier-to-noise ratio of the navigation signal is computed, the influence mechanism of narrow-band interference on the performance of the navigation signal can be reflected more truly.

Description

Based on spread-spectrum pseudo code discrete spectrum characteristic navigation signal equivalence carrier-to-noise ratio computing method

Technical field

The invention belongs to the computing method of navigation signal equivalence carrier-to-noise ratio, relate to a kind ofly, relate in particular under a kind of selective interference condition based on spread-spectrum pseudo code discrete spectrum characteristic navigation signal equivalence carrier-to-noise ratio computing method based on spread-spectrum pseudo code discrete spectrum characteristic navigation signal equivalence carrier-to-noise ratio computing method.

Background technology

Electromagnetic interference (EMI) is the important component part of carrying out navigation signal, receiver design to the impact analysis of satellite navigation signals, at present, analyze the influence of electromagnetic interference (EMI) to navigation signal, generally ignore the influence of spread-spectrum pseudo code discrete spectrum characteristic, derive to navigation signal catch, data demodulates and code tracking Effect on Performance; But because the discrete feature of navigation signal spread-spectrum pseudo code frequency spectrum, original analysis can't reflect truly that interference is to navigation signal Effect on Performance mechanism.

Summary of the invention

The technical matters that solves

For fear of the deficiencies in the prior art part, the present invention proposes a kind of based on spread-spectrum pseudo code discrete spectrum characteristic navigation signal equivalence carrier-to-noise ratio computing method.

Technical scheme

A kind of based on spread-spectrum pseudo code discrete spectrum characteristic navigation signal equivalence carrier-to-noise ratio computing method, it is characterized in that step is as follows:

Step 1, calculating navigation signal power spectrum density:

$G_s\left(f\right)=\frac{1}{{\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="HDA00003087323100012.png"\; state="\{\{state\}\}">N</figure-callout>}}^2}\&CenterDot;T_d\underset{k=-\&infin;}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{\left|C_{\mathrm{prn}}\left(k\right)\right|}^2\sin c^2[(f-k\&CenterDot;\mathrm{\&Delta;f})\&CenterDot;T_d]\&CenterDot;S\left(k\right)$

$=T_d\underset{k=-\&infin;}{\overset{\&infin;}{\mathrm{\&Sigma;}}}\sin c^2((f-k\&CenterDot;\mathrm{\&Delta;f})\&CenterDot;T_d){\left|C\left(k\right)\right|}^2\&CenterDot;S\left(k\right)$

Wherein, C _PrnBe to be leaf transformation in the N point discrete Fourier of finite length sequence of N in the cycle, Δ f is the code weight complex frequency, and k is the spectral line index, and S (k) is the signal modulation style portions of the spectrum.C (k)=C _Prn/ N is the normalization DFT of spread spectrum code sequence, and the navigation data information chip time cycle is T _d

Step 2, calculating narrow-band interference signal power spectrum density: G _i(f)=δ (f-f _i), wherein, δ () represents Dirac function, f _iBe the selective interference centre frequency;

Step 3, calculate equivalent carrier-to-noise ratio:

${(C_s/N_0)}_{\mathrm{eff}}=\frac{(C_s/N_0){\&Integral;}_{-\mathrm{\&beta;r}}^{\mathrm{\&beta;r}}{G}_s\left(f\right)\mathrm{df}}{{\&Integral;}_{-\mathrm{\&beta;r}}^{\mathrm{\&beta;r}}{G}_s\left(f\right)\mathrm{df}+(C_i/N_0){\&Integral;}_{-\mathrm{\&beta;r}}^{\mathrm{\&beta;r}}{G}_i\left(f\right)G_s\left(f\right)\mathrm{df}}$

Wherein, C _sN ₀Represent the carrier-to-noise ratio when noiseless, C _iN ₀The expression interference-to-noise ratio, G _s(f), G _i(f) power spectrum density of expression navigation signal, undesired signal, β _rThe expression correlator bandwidth.

Beneficial effect

What the present invention proposed is a kind of based on spread-spectrum pseudo code discrete spectrum characteristic navigation signal equivalence carrier-to-noise ratio computing method, under the selective interference environment, based on spread-spectrum pseudo code discrete spectrum characteristic, navigation signal equivalence carrier-to-noise ratio is calculated, more can be reflected the performance impact mechanism of selective interference truly navigation signal.

Description of drawings

Fig. 1: BOC (2,1) modulation navigation signal power spectrum density analogous diagram;

Fig. 2: under the selective interference environment, analyze BOC (2,1) modulation navigation signal equivalence carrier-to-noise ratio analogous diagram based on continuous frequency spectrum;

Fig. 3: under the selective interference environment, analyze BOC (2,1) modulation navigation signal equivalence carrier-to-noise ratio analogous diagram based on discrete spectrum.

Embodiment

Now in conjunction with the embodiments, accompanying drawing is further described the present invention:

1) produce principle according to the navigational range sign indicating number, the generation cycle be N=1023 limit for length Gold spread-spectrum pseudo code, spread-spectrum code rate R arranged _c=1.023Mchip/s carries out leaf transformation in the N point discrete Fourier to this spread-spectrum pseudo code, obtains recurrent pulses modulating baseband BOC (2,1) modulation signal power spectrum density.That is,

$G_p\left(f\right)=\frac{1}{{\mathrm{<figure-callout\; id="2"\; label="N"\; filenames="HDA00003087323100012.png"\; state="\{\{state\}\}">N</figure-callout>}}^2}\underset{k=-\&infin;}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{\left|C_{\mathrm{prn}}\left(k\right)\right|}^2\mathrm{\&delta;}(f-k\&CenterDot;\mathrm{\&Delta;f})\&CenterDot;S\left(k\right)$

$=\frac{1}{{1023}^2}\underset{k=1}{\overset{1023\&times;10}{\mathrm{\&Sigma;}}}{\left|C_{\mathrm{prn}}\left(k\right)\right|}^2\&CenterDot;\sin c^2(\mathrm{\&pi;}\&CenterDot;\left(\frac{k}{1023}\right))\&CenterDot;{\tan }^2\left(\frac{\mathrm{\&pi;<figure-callout\; id="4"\; label="k"\; filenames="HDA00003087323100012.png"\; state="\{\{state\}\}">k</figure-callout>}}{4\&times;1023}\right)$

2) navigation data adopts random bit stream, and the data message bit rate is R _d=50bps, the data chips cycle is T _d=1R _d, recurrent pulses modulating baseband BOC (2, the 1) modulation signal of step 1) is carried out the navigation data modulation, the power spectrum density that obtains modulating navigation signal, promptly

$G_s\left(f\right)=T_d\underset{k=-\&infin;}{\overset{\&infin;}{\mathrm{\&Sigma;}}}\sin c^2\left(\right(f-k\&CenterDot;\mathrm{\&Delta;f})\&CenterDot;T_d{)\&CenterDot;\left|C\left(k\right)\right|}^2\&CenterDot;S\left(k\right)$

$=\frac{1}{{1023}^2}\&times;\frac{1}{50}\underset{k=1}{\overset{1023\&times;10}{\mathrm{\&Sigma;}}}{\left|C_{\mathrm{prn}}\left(k\right)\right|}^2\&CenterDot;\sin c^2((f-1000k)\&times;\frac{1}{50})\sin c^2(\mathrm{\&pi;}\&CenterDot;\left(\frac{k}{1023}\right))\&CenterDot;{\tan }^2\left(\frac{\mathrm{\&pi;<figure-callout\; id="4"\; label="k"\; filenames="HDA00003087323100012.png"\; state="\{\{state\}\}">k</figure-callout>}}{4\&times;1023}\right)$

Simulation result is referring to Fig. 1.

3) be 24MHz in receiving end correlated bandwidth, C _sN ₀=45dB, C _iN ₀During=50dB, with step 2) in modulation navigation signal power spectrum density substitution equivalence carrier-to-noise ratio expression formula in, then be in conjunction with pseudo-code spread spectrum discrete spectrum characteristic BOC (2,1) modulation navigation signal equivalence carrier-to-noise ratio,

${(C_s/N_0)}_{\mathrm{eff}}=\frac{{10}^{4.5}{\&Integral;}_{-{12\&times;16}^6}^{{12\&times;16}^6}{G}_s\left(f\right)\mathrm{df}}{{\&Integral;}_{-{12\&times;10}^6}^{{12\&times;16}^6}{G}_s\left(f\right)\mathrm{df}+{10}^5\&times;\left(\frac{1}{50}\right)\sin c^2((f-1000k)\&CenterDot;\left(\frac{1}{50}\right))\&CenterDot;{\left|c\left(k\right)\right|}^2\&CenterDot;S\left(k\right)}$

With compare based on continuous spectrum BOC (2,1) modulation navigation signal equivalence carrier-to-noise ratio, simulation result is respectively referring to Fig. 2, Fig. 3.As seen, more can reflect of the influence of selective interference interfering frequency position truly based on spread-spectrum pseudo code discrete spectrum characteristic navigation signal equivalence carrier-to-noise ratio computing method to navigation signal equivalence carrier-to-noise ratio.

Claims (1)

1. one kind based on spread-spectrum pseudo code discrete spectrum characteristic navigation signal equivalence carrier-to-noise ratio computing method, it is characterized in that step is as follows:

Step 1, calculating navigation signal power spectrum density:

$G_s\left(f\right)=\frac{1}{N^2}\&CenterDot;T_d\underset{k=-\&infin;}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{\left|C_{\mathrm{prn}}\left(k\right)\right|}^2\sin c^2[(f-k\&CenterDot;\mathrm{\&Delta;f})\&CenterDot;T_d]\&CenterDot;S\left(k\right)$

$=T_d\underset{k=-\&infin;}{\overset{\&infin;}{\mathrm{\&Sigma;}}}\sin c^2((f-k\&CenterDot;\mathrm{\&Delta;f})\&CenterDot;T_d){\left|C\left(k\right)\right|}^2\&CenterDot;S\left(k\right)$

Wherein, C _PrnBe to be leaf transformation in the N point discrete Fourier of finite length sequence of N in the cycle, Δ f is the code weight complex frequency, and k is the spectral line index, and S (k) is the signal modulation style portions of the spectrum.C (k)=C _Prn/ N is the normalization DFT of spread spectrum code sequence, and the navigation data information chip time cycle is T _d

Step 2, calculating narrow-band interference signal power spectrum density: G _i(f)=δ (f-f _i), wherein, δ () represents Dirac function, f _iBe the selective interference centre frequency;

Step 3, calculate equivalent carrier-to-noise ratio:

${(C_s/N_0)}_{\mathrm{eff}}=\frac{(C_s/N_0){\&Integral;}_{-\mathrm{\&beta;r}}^{\mathrm{\&beta;r}}{G}_s\left(f\right)\mathrm{df}}{{\&Integral;}_{-\mathrm{\&beta;r}}^{\mathrm{\&beta;r}}{G}_s\left(f\right)\mathrm{df}+(C_i/N_0){\&Integral;}_{-\mathrm{\&beta;r}}^{\mathrm{\&beta;r}}{G}_i\left(f\right)G_s\left(f\right)\mathrm{df}}$

Wherein, C _s/ N ₀Represent the carrier-to-noise ratio when noiseless, C _i/ N ₀The expression interference-to-noise ratio, G _s(f), G _i(f) power spectrum density of expression navigation signal, undesired signal, β _rThe expression correlator bandwidth.

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