CN102033234A - Improved binary-coded character modulation method of satellite navigation system signals - Google Patents

Abstract

The invention relates to an improved binary-coded character modulation method of satellite navigation system signals, belonging to the technical field of satellite navigation. On the basis of binary-coded characters, the traditional spread spectrum character is split into K units; each unit uses the character pulse waveform based on MSK (minimum shift keying) instead of the binary value waveform; and proper parameters are selected, thereby having the advantages of interference rejection, multipath resistance and compatibility of the binary-coded character, realizing the constant enveloping of MSK modulation, enhancing the efficiency of the power amplifier, realizing large side lobe attenuation and the like. The invention uses the improved binary-coded character modulation to enhance the code tracking performance, multipath resistance, interference rejection and compatibility with other navigation signals, thereby realizing constant enveloping of signals and avoiding the occurrence of large-amplitude side lobes.

Description

The improvement binary coded character modulator approach of satellite navigation system signals

Technical field

What the present invention relates to is a kind of method of satellite navigation system technical field, specifically is a kind of improvement binary coded character modulator approach of satellite navigation system signals.

Background technology

The quality of satellite navigation system signals system performance is navigation, the positioning performance of decision systems directly, and the navigation signal modulation is one of key in the design of navigation signal system.Binary coded character (Binary Coded Symbol, be called for short BCS) be a kind of novel navigation signal modulation system, C.J.Hegarty, J.W.Betz, A.Saidi writes articles " Binary Coded SymbolModulations for GNSS " .Proceedings of ION NTM 2005, San Diego, USA, pp.56-64, January2005. " modulation of GPS (Global Position System) binary coded character ", by selecting suitable parameter to improve the correlated performance of signal, anti-interference and ability of anti-multipath as navigational system, particularly under the various situation of current communication technology of satellite fast development and signal kinds, separate and compatibility with the frequency spectrum of effective realization navigation signal.The binary coded character modulation is split into K unit with traditional spread symbol, binary value (1 or+1) is freely selected in each unit, thus to realize the modulation of navigation signal power miscellaneous, be modulated to as signal power and improve anti-interference and compatibility on the both sides secondary lobe of carrier frequency.

The binary coded character modulation has been applied in the navigational system such as GPS, Galileo at present, what adopt as GPS C/A coded signal is BSPK (binary phase shift keying) modulation, and what signals such as GPS L1C and Galileo E1OS, E1PRS adopted is the modulation system of deriving of BOC (scale-of-two offset carrier) and BOC.Binary coded character modulation is with by improving signal performance on the both sides secondary lobe that signal power is modulated to carrier frequency, but the binary coded character modulator approach that provides in the article can bring outer secondary lobe significantly that power amplification efficiency is reduced, and the code tracking of signal, anti-multipath, anti-interference and not ideal enough in some cases with the compatible performance of other navigation signal.At above-mentioned deficiency, the present invention proposes a kind of improvement binary coded character modulation technique, it make navigation signal have good code tracking performance, anti-interference and ability of anti-multipath, with other system signal compatibility, and signal has permanent envelope so that high power amplifier can be operated in saturation point or improve the efficient of power amplifier near it, avoids the appearance of secondary lobe significantly simultaneously.Therefore, based on the binary coded character modulation, making up well behaved signal modulation system has important meaning for the navigation and the station-keeping ability that promote navigational system.

Summary of the invention

The present invention is directed to the prior art above shortcomings, a kind of improvement binary coded character modulator approach of satellite navigation system signals is provided, adopt and improve binary coded character modulation (Modified Binary Coded Symbol, be called for short M-BCS), promote navigation signal code tracking, anti-multipath, anti-interference and with the compatible performance of other navigation signal, realize the permanent envelope of signal, avoid the appearance of secondary lobe significantly simultaneously.

The present invention is achieved by the following technical solutions, the present invention is on the basis of binary coded character, traditional spread symbol is split into K unit, each unit is taked to replace the binary value waveform based on the sign pulse waveform of MSK (minimum shift keying), by the parameter of selecting to be fit to, thereby realize anti-interference, the anti-multipath and the compatible performance of existing binary coded character, can realize again the MSK modulation permanent envelope, improve characteristics such as power amplification efficiency and side lobe attenuation are big.

The present invention includes following steps:

Step 1: at first, determine the spreading code frequency f according to the demand and the constraint condition of satellite navigation system _cOr period T _c, definite number K that needs the division unit, the length of each unit is T _c/ K selects suitable symbol [s ₀, s ₁..., s _K-1], wherein: f _cBe spreading code frequency (getting the integral multiple of 1.023MHz), its T reciprocal _cBe the spreading code cycle, K be determine the division unit form, s ₀, s ₁..., s _K-1Being selected K symbol, each value of symbol gets+and 1 or-1:

Step 2: according to determined spreading code frequency f _cOr period T _cDetermine the modulation waveform of spread symbol, take following mode to operate:

Wherein: T _ScBe chip period;

Step 3: structure improves binary coded character modulation M-BCS ([s ₀, s ₁..., s _K-1], f _c), and obtain spread symbol:

Wherein:

Be Direct-Spread signal, a _kBe frequency expansion sequence, q (t) is a spread symbol, T _cBe the spreading code cycle,

Described improvement binary coded character modulation M-BCS ([s ₀, s ₁..., s _K-1], f _c) in: [s ₀, s ₁..., s _K-1] be each symbol, span is+1 or-1, the spreading code frequency is f _c* 1.023MHz=1/T _c, through improving binary coded character M-BCS ([s ₀, s ₁..., s _K-1], f _c) signal after the orthogonal modulation is:

$s_{M-\mathrm{BCS}}\left(t\right)=\underset{k=-\&infin;}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{a}_k\mathrm{rect}[(t-{\mathrm{kT}}_{\mathrm{sc}})/T_{\mathrm{sc}}]\cos [\mathrm{\&pi;}(t-{\mathrm{kT}}_{\mathrm{sc}})/T_{\mathrm{sc}}]q(t-{\mathrm{kT}}_c)\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="HDA0000038549370000011.png,HDA0000038549370000021.png"\; state="\{\{state\}\}">cos</figure-callout>}2\mathrm{\&pi;}{f}_{\mathrm{ca}}t$

$+j\underset{l=-\&infin;}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{b}_l\mathrm{rect}[(t-T_{\mathrm{sc}}/2-l{T}_{\mathrm{sc}})/T_c]\sin [\mathrm{\&pi;}(t-l{T}_{\mathrm{sc}})/T_{\mathrm{sc}}]q(t-k{T}_c)\sin 2\mathrm{\&pi;}{f}_{\mathrm{ca}}t,$

Wherein: a _kAnd b _lBe respectively the spread spectrum code sequence (a of homophase and quadrature branch _kAnd b _lValue gets+and 1 or-1), f _CaBe carrier frequency; As K=1 and K=2f _s/ f _cThe time, structure obtains M-BCS ([s ₀, s ₁..., s _K-1], f _c) special shape M-BPSK-R (f _c) and M-BOC (f _s, f _c).

Described improvement binary coded character modulation M-BCS ([s ₀, s ₁..., s _K-1], f _c) power spectrum density be:

Wherein: f _cBe the spreading code frequency, K be determine the division unit form, each symbol s _kGet+1 or-1;

Step 4: utilize following mode to M-BCS ([s ₀, s ₁..., s _K-1], f _c) carry out the orthogonal modulation of spread spectrum code sequence:

$s_{M-\mathrm{BCS}}\left(t\right)=\underset{k=-\&infin;}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{a}_k\mathrm{rect}[(t-{\mathrm{kT}}_{\mathrm{sc}})/T_{\mathrm{sc}}]\cos [\mathrm{\&pi;}(t-{\mathrm{kT}}_{\mathrm{sc}})/T_{\mathrm{sc}}]q(t-{\mathrm{kT}}_c)\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="HDA0000038549370000011.png,HDA0000038549370000021.png"\; state="\{\{state\}\}">cos</figure-callout>}2\mathrm{\&pi;}{f}_{\mathrm{ca}}t$ $+j\underset{l=-\&infin;}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{b}_l\mathrm{rect}[(t-T_{\mathrm{sc}}/2-l{T}_{\mathrm{sc}})/T_c]\sin [\mathrm{\&pi;}(t-l{T}_{\mathrm{sc}})/T_{\mathrm{sc}}]q(t-k{T}_c)\sin 2\mathrm{\&pi;}{f}_{\mathrm{ca}}t,$ Wherein:

a _kAnd b _lBe respectively the spread spectrum code sequence of homophase and quadrature branch, f _CaBe carrier frequency, T _cBe spreading code cycle, T _ScBe chip period:

Step 5: to the M-BCS ([s that is constructed ₀, s ₁..., s _K-1], f _c) signal performance is tested, if the permanent envelope error of signal power spectral density, code tracking precision and multipath does not satisfy designed navigational system performance need and constraint, return step 1 and reselect the spreading code frequency, divide unit number and tilde.

Compared with prior art, the improvement binary coded character modulation that the present invention proposes, by the parameter of selecting to be fit to, with anti-interference, anti-multipath and the compatible performance that realizes existing binary coded character, can realize again signal permanent envelope, improve characteristics such as power amplification efficiency and side lobe attenuation are big.

Description of drawings

Fig. 1 improves binary coded character modulation synoptic diagram.

Fig. 2 improves binary coded character modulation process flow diagram.

Fig. 3 adopts the symbol waveform of M-BCS ([1,1,1,1], 1) modulation embodiment.

Fig. 4 adopts the baseband frequency spectrum figure of M-BCS ([1,1,1,1], 1) modulation embodiment.

Fig. 5 adopts the code tracking precision analysis figure of M-BCS ([1,1,1,1], 1) modulation embodiment.

Fig. 6 adopts the multipath error analysis figure of M-BCS ([1,1,1,1], 1) modulation embodiment.

Embodiment

Below embodiments of the invention are elaborated, present embodiment is being to implement under the prerequisite with the technical solution of the present invention, provided detailed embodiment and concrete operating process, but protection scope of the present invention is not limited to following embodiment.

As shown in Figure 2, present embodiment is determined the spreading code frequency f at first according to navigational system performance need and constraint _c=1.023MHz, symbol [s is selected in number K=4 of determining to need to divide the unit ₀, s ₁..., s _K-1]=[-1,1,1,1]; Then according to determined spreading code frequency f _cDetermine the modulation waveform of spread symbol, structure improves binary coded character modulation M-BCS ([1,1,1,1], 1), and concrete steps are as follows:

Step 1: at first, determine the spreading code frequency f according to the demand and the constraint condition of satellite navigation system _cOr period T _c, definite number K that needs the division unit, the length of each unit is T _c/ K selects suitable symbol [s ₀, s ₁..., s _K-1], wherein: f _cBe spreading code frequency (getting the integral multiple of 1.023MHz), its T reciprocal _cBe the spreading code cycle, K be determine the division unit form, s ₀, s ₁..., s _K-1Being selected K symbol, each value of symbol gets+and 1 or-1;

Step 2: according to determined spreading code frequency f _cOr period T _cDetermine the modulation waveform of spread symbol, take following mode to operate:

Wherein: T _ScBe chip period:

Step 3: structure improves binary coded character modulation M-BCS ([s ₀, s ₁..., s _K-1], f _c), and obtain spread symbol, as shown in Figure 3:

Wherein:

Be Direct-Spread signal, a _kBe frequency expansion sequence, q (t) is a spread symbol, T _cBe the spreading code cycle,

Described improvement binary coded character modulation M-BCS ([s ₀, s ₁..., s _K-1], f _c) in: [s ₀, s ₁..., s _K-1] be each symbol, span is+1 or-1, the spreading code frequency is f _c* 1.023MHz=1/T _c, through improving binary coded character M-BCS ([s ₀, s ₁..., s _K-1], f _c) signal after the orthogonal modulation is:

$s_{M-\mathrm{BCS}}\left(t\right)=\underset{k=-\&infin;}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{a}_k\mathrm{rect}[(t-{\mathrm{kT}}_{\mathrm{sc}})/T_{\mathrm{sc}}]\cos [\mathrm{\&pi;}(t-{\mathrm{kT}}_{\mathrm{sc}})/T_{\mathrm{sc}}]q(t-{\mathrm{kT}}_c)\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="HDA0000038549370000011.png,HDA0000038549370000021.png"\; state="\{\{state\}\}">cos</figure-callout>}2\mathrm{\&pi;}{f}_{\mathrm{ca}}t$

$+j\underset{l=-\&infin;}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{b}_l\mathrm{rect}[(t-T_{\mathrm{sc}}/2-l{T}_{\mathrm{sc}})/T_c]\sin [\mathrm{\&pi;}(t-l{T}_{\mathrm{sc}})/T_{\mathrm{sc}}]q(t-k{T}_c)\sin 2\mathrm{\&pi;}{f}_{\mathrm{ca}}t,$

Wherein: a _kAnd b _lBe respectively the spread spectrum code sequence (a of homophase and quadrature branch _kAnd b _lValue gets+and 1 or-1), f _CaBe carrier frequency; As K=1 and K=2f _s/ f _cThe time, structure obtains M-BCS ([s ₀, s ₁..., s _K-1], f _c) special shape M-BPSK-R (f _c) and M-BOC (f _s, f _c).

Described improvement binary coded character modulation M-BCS ([s ₀, s ₁..., s _K-1], f _c) power spectrum density be:

Wherein: f _cBe the spreading code frequency, K be determine the division unit form, each symbol s _kGet+1 or-1:

Step 4: utilize following mode to M-BCS ([s ₀, s ₁..., s _K-1], f _c) carry out the orthogonal modulation of spread spectrum code sequence:

$s_{M-\mathrm{BCS}}\left(t\right)=\underset{k=-\&infin;}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{a}_k\mathrm{rect}[(t-{\mathrm{kT}}_{\mathrm{sc}})/T_{\mathrm{sc}}]\cos [\mathrm{\&pi;}(t-{\mathrm{kT}}_{\mathrm{sc}})/T_{\mathrm{sc}}]q(t-{\mathrm{kT}}_c)\mathrm{<figure-callout\; id="2"\; label="cos"\; filenames="HDA0000038549370000011.png,HDA0000038549370000021.png"\; state="\{\{state\}\}">cos</figure-callout>}2\mathrm{\&pi;}{f}_{\mathrm{ca}}t$ $+j\underset{l=-\&infin;}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{b}_l\mathrm{rect}[(t-T_{\mathrm{sc}}/2-l{T}_{\mathrm{sc}})/T_c]\sin [\mathrm{\&pi;}(t-l{T}_{\mathrm{sc}})/T_{\mathrm{sc}}]q(t-k{T}_c)\mathrm{<figure-callout\; id="2"\; label="sin"\; filenames="HDA0000038549370000011.png,HDA0000038549370000021.png"\; state="\{\{state\}\}">sin</figure-callout>}2\mathrm{\&pi;}{f}_{\mathrm{ca}}t,$ Wherein: a _kAnd b _lBe respectively the spread spectrum code sequence of homophase and quadrature branch, f _CaBe carrier frequency, T _cBe spreading code cycle, T _ScBe chip period;

Step 5: to the M-BCS ([s that is constructed ₀, s ₁..., s _K-1], f _c) signal performance is tested, if the permanent envelope error of signal power spectral density, code tracking precision and multipath does not satisfy designed navigational system performance need and constraint, return step 1 and reselect the spreading code frequency, divide unit number and tilde.

As shown in Figure 4, provided the comparison of M-BCS ([1,1,1,1], 1) and BCS ([1,1,1,1], 1) power spectrum density, the horizontal ordinate among the figure is represented frequency, and unit is Hz; Ordinate among the figure is expressed as the power spectrum amplitude, the dB of unit.To find out M-BCS ([1,1,1,1], 1) frequency spectrum of baseband modulation signal is when frequency deviation is 5MHz, and its amplitude is with respect to M-BCS ([1,1,1,1], 1) decay is apparent in view, and BCS ([1,1 is described, 1,1], 1) M-BCS ([1,1,1,1], 1) the modulated energy side lobe attenuation is big, can improve power amplification efficiency, is particularly suitable for being applied in the signal system of satellite navigation system.

As shown in Figure 5, provided M-BCS ([1,1,1,1], 1) and BCS ([1,1,1,1], 1) code tracking ratio of precision, the horizontal ordinate among the figure is represented the carrier-to-noise ratio of signal, and unit is dB-Hz; Ordinate among the figure is expressed as the code tracking error lower bound of signal, the m of unit.M-BCS ([1,1,1,1], 1) is modulated under the different signal carrier-to-noise ratios has code tracking and antijamming capability preferably than M-BCS ([1,1,1,1], 1).

As shown in Figure 6, provided the anti-multipath of M-BCS ([1,1,1,1], 1) and BCS ([1,1,1,1], 1) relatively, the horizontal ordinate among the figure is represented the multipath length of signal, and unit is m; Ordinate among the figure is expressed as the permanent envelope error of multipath of signal, the m of unit.M-BCS ([1,1,1,1], 1) modulated energy is realized the similar ability of anti-multipath with BCS ([1,1,1,1], 1), is 45m-80m and 150m-170m at the multipath distance range, can realize better anti-multipath ability.

Claims (3)

1. the improvement binary coded character modulator approach of a satellite navigation system signals is characterized in that, may further comprise the steps:

Step 1: at first, determine the spreading code frequency f according to the demand and the constraint condition of satellite navigation system _cOr period T _c, definite number K that needs the division unit, the length of each unit is T _c/ K selects suitable symbol [s ₀, s ₁..., s _K-1], wherein: f _cBe spreading code frequency (getting the integral multiple of 1.023MHz), its T reciprocal _cBe the spreading code cycle, K be determine the division unit form, s ₀, s ₁..., s _K-1Being selected K symbol, each value of symbol gets+and 1 or-1;

Step 2: according to determined spreading code frequency f _cOr period T _cDetermine the modulation waveform of spread symbol, take following mode to operate: Wherein: T _ScBe chip period:

Step 3: structure improves binary coded character modulation M-BCS ([s ₀, s ₁..., s _K-1], f _c), and obtain spread symbol: Wherein: Be Direct-Spread signal, a _kBe frequency expansion sequence, q (t) is a spread symbol, and T is the spreading code cycle,

Step 4: utilize following mode to M-BCS ([s ₀, s ₁..., s _K-1], f _c) carry out the orthogonal modulation of spread spectrum code sequence:

$s_{M-\mathrm{BCS}}\left(t\right)=\underset{k=-\&infin;}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{a}_k\mathrm{rect}[(t-{\mathrm{kT}}_{\mathrm{sc}})/T_{\mathrm{sc}}]\cos [\mathrm{\&pi;}(t-{\mathrm{kT}}_{\mathrm{sc}})/T_{\mathrm{sc}}]q(t-{\mathrm{kT}}_c)\cos 2\mathrm{\&pi;}{f}_{\mathrm{ca}}t$ $+j\underset{l=-\&infin;}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{b}_l\mathrm{rect}[(t-T_{\mathrm{sc}}/2-l{T}_{\mathrm{sc}})/T_c]\sin [\mathrm{\&pi;}(t-l{T}_{\mathrm{sc}})/T_{\mathrm{sc}}]q(t-k{T}_c)\sin 2\mathrm{\&pi;}{f}_{\mathrm{ca}}t,$ Wherein: a _kAnd b _lBe respectively the spread spectrum code sequence of homophase and quadrature branch, f _CaBe carrier frequency, T _cBe spreading code cycle, T _ScBe chip period;

Step 5: to the M-BCS ([s that is constructed ₀, s ₁..., s _K-1], f _c) signal performance is tested, if the permanent envelope error of signal power spectral density, code tracking precision and multipath does not satisfy designed navigational system performance need and constraint, return step 1 and reselect the spreading code frequency, divide unit number and tilde.

2. the improvement binary coded character modulator approach of satellite navigation system signals according to claim 1 is characterized in that, described improvement binary coded character modulation M-BCS ([s ₀, s ₁..., s _K-1], f _c) in: [s ₀, s ₁..., s _K-1] be each symbol, span is+1 or-1, the spreading code frequency is f _c* 1.023MHz=1/T _c, through improving binary coded character M-BCS ([s ₀, s ₁..., s _K-1], f _c) signal after the orthogonal modulation is:

$s_{M-\mathrm{BCS}}\left(t\right)=\underset{k=-\&infin;}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{a}_k\mathrm{rect}[(t-{\mathrm{kT}}_{\mathrm{sc}})/T_{\mathrm{sc}}]\cos [\mathrm{\&pi;}(t-{\mathrm{kT}}_{\mathrm{sc}})/T_{\mathrm{sc}}]q(t-{\mathrm{kT}}_c)\cos 2\mathrm{\&pi;}{f}_{\mathrm{ca}}t$

$+j\underset{l=-\&infin;}{\overset{\&infin;}{\mathrm{\&Sigma;}}}{b}_l\mathrm{rect}[(t-T_{\mathrm{sc}}/2-l{T}_{\mathrm{sc}})/T_c]\sin [\mathrm{\&pi;}(t-l{T}_{\mathrm{sc}})/T_{\mathrm{sc}}]q(t-k{T}_c)\sin 2\mathrm{\&pi;}{f}_{\mathrm{ca}}t,$

Wherein: a _kAnd b _lBe respectively the spread spectrum code sequence (a of homophase and quadrature branch _kAnd b _lValue gets+and 1 or-1), f _CaBe carrier frequency; As K=1 and K=2f _s/ f _cThe time, structure obtains M-BCS ([s ₀, s ₁..., s _K-1], f _c) special shape M-BPSK-R (f _c) and M-BOC (f _s, f _c).

3. the improvement binary coded character modulator approach of satellite navigation system signals according to claim 1 is characterized in that, described improvement binary coded character modulation M-BCS ([s ₀, s ₁..., s _K-1], f _c) power spectrum density be:

Wherein: f _cBe the spreading code frequency, K be determine the division unit form, each symbol s _kGet+1 or-1.

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