CN105116426A - Time domain raised cosine three-level offset carrier modulation method - Google Patents

Abstract

The invention aims to provide a time domain raised cosine three-level offset carrier (TDRC-TOC (m, n, Rho)) modulation method, comprising the processes of: first, determining a spreading code frequency fc, a subcarrier frequency fsc, a sine or cosine phase subcarrier modulation mode and a time domain raised cosine pulse time width duty ratio Rho, and constructing time domain raised cosine three-level sine or cosine phase subcarrier signals; and second, utilizing a pseudorandom sequence to perform spread spectrum on navigation signals, then performing subcarrier modulation, and finally performing orthogonal branch carrier modulation on obtained signals. The method can generate signals of constant amplitudes to flexibly adjust the main lobe and side lobe split degree of a signal power spectrum, thereby allowing the navigation signals to possess the characteristics of good code tracking performance, high anti-interference and anti-multipath capability, and great compatible capability with signals of other systems; meanwhile the method can avoid side blobs of large amplitudes, and improve frequency spectrum efficiency, and is especially suitable for the satellite navigation service employing a high efficiency nonlinear amplifier and having the power and bandwidth limited.

Description

A kind of based on time domain raised cosine pulse three grades of symbol offset carrier modulating methods

Technical field:

The present invention relates to a kind of implementation method of satellite navigation system signals, be specifically related to a kind of based on time domain raised cosine pulse three grades of symbol offset carrier modulating methods.

Background technology:

Navigation Signal System is in the position of most critical in the Top-layer Design Method of satellite navigation system, the Navigation and localization performance of the direct decision systems of quality of its performance, and navigation signal modulation is the most important thing in Navigation Signal System design.GLONASS (Global Navigation Satellite System) (GlobalNavigationSatelliteSystem can be shared better to make multi-signal, GNSS) limited frequency, improve distance accuracy and the interference free performance of signal further, new signal madulation mode constantly presents simultaneously.Binary offset carrier (BinaryOffsetCarrier, BOC (n, m)) be a kind of new type of modulation mode that can meet above-mentioned requirements, wherein spreading code frequency is m × 1.023MHz, sub-carrier frequencies is n × 1.023MHz, its implementation refers to document Betz.J, " TheOffsetCarrierModulationforGPSModernization, " IONNTM, SanDiego, CA, January25-27,1999.

Betz.J document " BinaryOffsetCarrierModulationsforRadionavigation; " Navigation:JournaloftheInstituteofNavigation, vol.48, No.4, Winter2001-2002. point out in, the same band, take same band and signal projector and receiver are done to same simple designs condition under, the Performance Ratio BPSK modulation signal of BOC modulation signal is more superior.BOC modulation has been widely used in the GPS (Global Position System) such as GPS, Galileo and Compass at present.

Along with the continuous increase of satellite navigation signals quantity, frequency spectrum resource is nervous, and the interference improved under finite bandwidth between signal performance and reduction adjacent signals becomes current research emphasis.The BOC modulator approach provided in article can cause band outer significantly secondary lobe that power amplification efficiency is reduced, and the code tracking performance of signal, anti-multipath and antijamming capability are still not ideal enough, for above-mentioned deficiency, the present invention proposes a kind of based on time domain raised cosine pulse three grades of symbol offset carrier modulating method (TimeDomainRaisedCosineThree-levelsOffsetCarrier, TDRC-TOC (n, m, ρ)), wherein sub-carrier signal can value be ± 1 and 0, and ± 1 signal waveform is represented by time domain raised cosine pulse, the design that the method is not only navigation signal provides more choices, and effectively can reduce power spectrum significantly secondary lobe, reduce the interference to signal between neighbour, improve the power usefulness of navigation signal, both had better code tracking performance concurrently simultaneously, anti-multipath and antijamming capability, important meaning is had to the Navigation and localization ability promoting navigational system.

Summary of the invention:

The object of the invention is to propose a kind of can the main lobe of flexible power spectrum signal and the splitting degree of secondary lobe, make navigation signal have good code tracking performance, anti-interference and ability of anti-multipath, with other system signal compatibility based on time domain raised cosine pulse three grades of symbol offset carrier modulating methods.

The object of the present invention is achieved like this:

(1) spreading code cycle T is first determined _c, subcarrier cycle T _sc, time domain raised cosine pulse time width dutycycle ρ, sinusoidal or cosine phase subcarrier modulation modes, constructs or cosine phase sub-carrier signal sinusoidal based on time domain raised cosine pulse three grades of symbols, is specifically expressed as:

Based on time domain raised cosine pulse three grades of symbol sinusoidal phase sub-carrier signal q _s(t, ρ) is:

$q_s(t,\mathrm{\ρ})=sign\left(sin\right(2{\mathrm{\πf}}_{sc}t\left)\right)\×\underset{i=0}{\overset{+\mathrm{\∞}}{\Σ}}{P}_{\frac{T_{sc}}{2}}(t-i\frac{T_{sc}}{2},\mathrm{\ρ}),t>0;$

Based on time domain raised cosine pulse three grades of symbol cosine phase sub-carrier signal q _c(t, ρ) is:

$q_c(t,\mathrm{\ρ})=sign\left(cos\right(2{\mathrm{\πf}}_{sc}t\left)\right)\×\underset{i=0}{\overset{+\mathrm{\∞}}{\Σ}}{P}_{\frac{T_{sc}}{4}}(t-i\frac{T_{sc}}{4},\mathrm{\ρ}),t>0;$

Wherein P _τthe time domain raised cosine pulse shape of (t, ρ) to be time width be ρ τ, namely sign (t) is sign function, namely $sign\left(t\right)=\left\{\begin{array}{cc}1,& t>0\\ -1,& t<0\end{array}\right.;$

(2) according to the spreading code cycle T determined _cwith subcarrier cycle T _scpseudo-random sequence is utilized to carry out spread spectrum to navigation signal, then the spread-spectrum signal obtained and step (1) determined sine or cosine phase sub-carrier signal are carried out time domain multiplication, obtain a kind of based on time domain raised cosine pulse three grades of symbols sines or cosine phase offset carrier baseband modulation signal, be specifically expressed as:

Based on time domain raised cosine pulse three grades of symbol sinusoidal phase offset carrier baseband modulation signal S _{tDRC-TOCs (n, m, ρ)}(t) be:

$S_{TDRC-TOCs(n,m,\mathrm{\&rho;})}\left(t\right)=d\left(t\right)\underset{l=0}{\overset{L-1}{\&Sigma;}}{a}_{l}rect(t-{\mathrm{lT}}_c)\&times;q_s(t,\mathrm{\&rho;}),t>0;$

Based on time domain raised cosine pulse three grades of symbol cosine phase offset carrier baseband modulation signal S _{tDRC-TOCc (n, m, ρ)}(t) be:

$S_{TDRC-TOCc(n,m,\mathrm{\&rho;})}\left(t\right)=d\left(t\right)\underset{l=0}{\overset{L-1}{\&Sigma;}}{a}_{l}rect(t-{\mathrm{lT}}_c)\&times;q_c(t,\mathrm{\&rho;}),t>0;$

Wherein d (t) is navigation signal data channel information; a _ll spreading code of pseudorandom spreading sequence; L is the chip lengths of pseudo-random sequence; Rect (t) is rectangular door function, namely or $n=\frac{1}{T_{sc}\&times;1.023MHz};m=\frac{f_c}{1.023MHz}$ Or $m=\frac{1}{T_c\&times;1.023MHz};$

(3) by a kind of carrier modulation of carrying out quadrature branch based on time domain raised cosine pulse three grades of symbols sines or cosine phase offset carrier baseband modulation signal described in step (2), finally obtain described one based on time domain raised cosine pulse three grades of symbols sines or cosine phase offset carrier (boc) modulated signals, be specifically expressed as:

Based on time domain raised cosine pulse three grades of symbol sinusoidal phase offset carrier (boc) modulated signals M _{tDRC-TOCs (n, m, ρ)}(t) be:

$\begin{array}{c}{M}_{TDRC-TOCs(n,m,\mathrm{\&rho;})}\left(t\right)=\&lsqb;d\left(t\right)\underset{l=0}{\overset{L-1}{\&Sigma;}}{a}_{l}rect(t-{\mathrm{lT}}_c)\&times;sign\left(\sin \right(2{\mathrm{\&pi;f}}_{sc}t\left)\right)\&times;\underset{i=0}{\overset{+\mathrm{\&infin;}}{\&Sigma;}}{P}_{\frac{T_{sc}}{2}}(t-i\frac{T_{sc}}{2},\mathrm{\&rho;})\&rsqb;\cos \left(2{\mathrm{\&pi;f}}_{car}t\right)\\ +\&lsqb;p\left(t\right)\underset{l=0}{\overset{L-1}{\&Sigma;}}{b}_{l}rect(t-{\mathrm{lT}}_c)\&times;sign\left(\sin \right(2{\mathrm{\&pi;f}}_{sc}t\left)\right)\&times;\underset{i=0}{\overset{+\mathrm{\&infin;}}{\&Sigma;}}{P}_{\frac{T_{sc}}{2}}(t-i\frac{T_{sc}}{2},\mathrm{\&rho;})\&rsqb;\sin \left(2{\mathrm{\&pi;f}}_{car}t\right)\end{array};$

Based on time domain raised cosine pulse three grades of symbol cosine phase offset carrier (boc) modulated signals M _{tDRC-TOCc (n, m, ρ)}(t) be:

$\begin{array}{c}{M}_{TDRC-TOCc(n,m,\mathrm{\&rho;})}\left(t\right)=\&lsqb;d\left(t\right)\underset{l=0}{\overset{L-1}{\&Sigma;}}{a}_{l}rect(t-{\mathrm{lT}}_c)\&times;sign\left(\cos \right(2{\mathrm{\&pi;f}}_{sc}t\left)\right)\&times;\underset{i=0}{\overset{+\mathrm{\&infin;}}{\&Sigma;}}{P}_{\frac{T_{sc}}{4}}(t-i\frac{T_{sc}}{4},\mathrm{\&rho;})\&rsqb;\cos \left(2{\mathrm{\&pi;f}}_{car}t\right)\\ +\&lsqb;p\left(t\right)\underset{l=0}{\overset{L-1}{\&Sigma;}}{b}_{l}rect(t-{\mathrm{lT}}_c)\&times;sign\left(\cos \right(2{\mathrm{\&pi;f}}_{sc}t\left)\right)\&times;\underset{i=0}{\overset{+\mathrm{\&infin;}}{\&Sigma;}}{P}_{\frac{T_{sc}}{4}}(t-i\frac{T_{sc}}{4},\mathrm{\&rho;})\&rsqb;\sin \left(2{\mathrm{\&pi;f}}_{car}t\right)\end{array};$

Wherein d (t) is navigation signal data channel information; P (t) is pilot channel information, and value is complete+1 or-1; a _ll spreading code of in-phase branch pseudorandom spreading sequence; b _kit is a kth spreading code of quadrature branch pseudorandom spreading sequence; f _carit is carrier frequency.

(4) a kind of Performance Evaluation carrying out navigation signal based on time domain raised cosine pulse three grades of symbol offset carrier (boc) modulated signals will obtained in step (3), if the code tracking precision of signal, anti-multipath and compatibility do not meet designed navigational system performance requirement and constraint condition, then return step (1), redefine spreading code cycle T _c, subcarrier cycle T _sc, sinusoidal or cosine phase subcarrier modulation modes, and time domain raised cosine pulse time width dutycycle ρ.

The present invention can also comprise:

Described spreading code frequency f _cwith sub-carrier frequencies f _scvalue be the integral multiple of 1.023MHz.

Described based on time domain raised cosine pulse three grades of symbol sinusoidal phase offset carrier baseband modulation signal power spectrum density G _{tDRC-TOCs (n, m, ρ)}(f) be:

Described based on time domain raised cosine pulse three grades of symbol cosine phase offset carrier baseband modulation signal power spectrum density G _{tDRC-TOCc (n, m, ρ)}(f) be:

Wherein h is modulation index, namely or

The principal feature of method of the present invention is as follows:

(1) power efficiency is high: the power spectrum side lobe attenuation speed of modulation signal of the present invention is faster and amplitude is lower, and encircled energy is higher.

(2) tracking accuracy is high: in receiver bandwidth, and the power spectrum of modulation signal of the present invention has splitting ability and amplitude is comparatively large, under the condition of Bandwidth-Constrained, has higher Gabor bandwidth and lower code tracking error.

(3) ability of anti-multipath is strong: modulation signal of the present invention has permanent envelope trait, is particularly suitable for adopting the power of efficient non-linear amplifiers and all limited the urban satellite navigation service of bandwidth, its multipath error envelope decay faster and amplitude is lower.

(4) compatible high: the power spectrum side lobe attenuation speed of modulation signal of the present invention is faster and amplitude is lower, less to other navigation signal interference of same frequency range.

(5) dirigibility of Design of Signal is high: time domain raised cosine pulse duty ratio of time in adjustment sub-carrier signal flexibly, for the design of navigation signal provides more choices, and by selected suitable parameter, can the main lobe of flexible power spectrum signal and the splitting degree of secondary lobe.

Accompanying drawing explanation

Fig. 1 is TDRC-TOC signal madulation model and implementation method process flow diagram;

Fig. 2 is TDRC-TOC channel distortion experienced signal waveform;

Fig. 3 is the power spectrum density of TDRC-TOC signal embodiment under different time domain raised cosine pulse duty ratio of time ρ;

The power spectrum density of the TDRC-TOC embodiment signal that Fig. 4 carries for traditional BOC and the present invention;

The Gabor bandwidth of the TDRC-TOC embodiment signal that Fig. 5 carries for traditional BOC and the present invention;

The code tracking precision of the TDRC-TOC embodiment signal that Fig. 6 carries for traditional BOC and the present invention;

The multipath error envelope of the TDRC-TOC embodiment signal that Fig. 7 carries for traditional BOC and the present invention;

The average multipath error of the TDRC-TOC embodiment signal that Fig. 8 carries for traditional BOC and the present invention.

Embodiment:

Below in conjunction with drawings and Examples, the invention will be further described:

Fig. 1 and Fig. 2 is respectively the TDRC-TOC signal madulation model that the present invention carries, implementation method process flow diagram and sub-carrier signal waveform, and each symbol wherein in Fig. 1 is defined as follows:

D (t): navigation signal data channel information;

P (t): pilot channel information;

A _l: the pseudorandom spread spectrum code sequence of in-phase branch;

B _l: the pseudorandom spread spectrum code sequence of quadrature branch;

Rec (t): rectangular door function;

Q _s(t, ρ): described one is based on time domain raised cosine pulse three grades of symbol sinusoidal phase sub-carrier signal waveforms;

Q _c(t, ρ): described one is based on time domain raised cosine pulse three grades of symbol cosine phase sub-carrier signal waveforms;

M _tDRC-TOC(t, ρ): described one is based on time domain raised cosine pulse three grades of symbol offset carrier (boc) modulated signals;

F _c: spreading code frequency;

F _car: carrier frequency;

F _sc: sub-carrier frequencies;

Composition graphs 1, implementation method of the present invention is as follows:

(1) spreading code frequency f is first determined _cor spreading code cycle T _c(frequency and cycle each other inverse can determine arbitrarily one of them parameter), sub-carrier frequencies f _scor subcarrier cycle T _sc, time domain raised cosine pulse time width dutycycle ρ and sinusoidal or cosine phase subcarrier modulation modes, construct a kind of based on time domain raised cosine pulse three grades of symbols sines or cosine phase sub-carrier signal, be specifically expressed as:

Based on time domain raised cosine pulse three grades of symbol sinusoidal phase sub-carrier signal q _s(t, ρ) is:

$q_s(t,\mathrm{\&rho;})=sign\left(sin\right(2{\mathrm{\&pi;f}}_{sc}t\left)\right)\&times;\underset{i=0}{\overset{+\mathrm{\&infin;}}{\&Sigma;}}{P}_{\frac{T_{sc}}{2}}(t-i\frac{T_{sc}}{2},\mathrm{\&rho;}),t>0;$

Based on time domain raised cosine pulse three grades of symbol cosine phase sub-carrier signal q _c(t, ρ) is:

$q_c(t,\mathrm{\&rho;})=sign\left(\cos \right(2{\mathrm{\&pi;f}}_{sc}t\left)\right)\&times;\underset{i=0}{\overset{+\mathrm{\&infin;}}{\&Sigma;}}{P}_{\frac{T_{sc}}{4}}(t-i\frac{T_{sc}}{4},\mathrm{\&rho;}),t>0;$

Wherein P _τthe time domain raised cosine pulse shape of (t, ρ) to be time width be ρ τ, namely sign (t) is sign function, namely $sign\left(t\right)=\left\{\begin{array}{cc}1,& t>0\\ -1,& t<0\end{array}\right.;$

(2) according to the spreading code frequency f determined _cor spreading code cycle T _cwith sub-carrier frequencies f _scor subcarrier cycle T _scpseudo-random sequence is utilized to carry out spread spectrum to navigation signal, then the spread-spectrum signal obtained and step (1) determined sine or cosine phase sub-carrier signal are carried out time domain multiplication, obtain a kind of based on time domain raised cosine pulse three grades of symbols sines or cosine phase offset carrier baseband modulation signal, be specifically expressed as:

Based on time domain raised cosine pulse three grades of symbol sinusoidal phase offset carrier baseband modulation signal S _{tDRC-TOCs (n, m, ρ)}(t) be:

$S_{TDRC-TOCs(n,m,\mathrm{\&rho;})}\left(t\right)=d\left(t\right)\underset{l=0}{\overset{L-1}{\&Sigma;}}{a}_{l}rect(t-{\mathrm{lT}}_c)\&times;q_s(t,\mathrm{\&rho;}),t>0;$

Based on time domain raised cosine pulse three grades of symbol cosine phase offset carrier baseband modulation signal S _{tDRC-TOCc (n, m, ρ)}(t) be:

$S_{TDRC-TOCc(n,m,\mathrm{\&rho;})}\left(t\right)=d\left(t\right)\underset{l=0}{\overset{L-1}{\&Sigma;}}{a}_{l}rect(t-{\mathrm{lT}}_c)\&times;q_c(t,\mathrm{\&rho;}),t>0;$

Wherein d (t) is navigation signal data channel information; a _ll spreading code of pseudorandom spreading sequence; L is the chip lengths of pseudo-random sequence; Rect (t) is rectangular door function, namely or $n=\frac{1}{T_{sc}\&times;1.023MHz};m=\frac{f_c}{1.023MHz}$ Or $m=\frac{1}{T_c\&times;1.023MHz};$

(3) by a kind of carrier modulation of carrying out quadrature branch based on time domain raised cosine pulse three grades of symbols sines or cosine phase offset carrier baseband modulation signal described in step (2), finally obtain described one based on time domain raised cosine pulse three grades of symbols sines or cosine phase offset carrier (boc) modulated signals, be specifically expressed as:

Based on time domain raised cosine pulse three grades of symbol sinusoidal phase offset carrier (boc) modulated signals M _{tDRC-TOCs (n, m, ρ)}(t) be:

$\begin{array}{c}{M}_{TDRC-TOCs(n,m,\mathrm{\&rho;})}\left(t\right)=\&lsqb;d\left(t\right)\underset{l=0}{\overset{L-1}{\&Sigma;}}{a}_{l}rect(t-{\mathrm{lT}}_c)\&times;sign\left(\sin \right(2{\mathrm{\&pi;f}}_{sc}t\left)\right)\&times;\underset{i=0}{\overset{+\mathrm{\&infin;}}{\&Sigma;}}{P}_{\frac{T_{sc}}{2}}(t-i\frac{T_{sc}}{2},\mathrm{\&rho;})\&rsqb;\cos \left(2{\mathrm{\&pi;f}}_{car}t\right)\\ +\&lsqb;p\left(t\right)\underset{l=0}{\overset{L-1}{\&Sigma;}}{b}_{l}rect(t-{\mathrm{lT}}_c)\&times;sign\left(\sin \right(2{\mathrm{\&pi;f}}_{sc}t\left)\right)\&times;\underset{i=0}{\overset{+\mathrm{\&infin;}}{\&Sigma;}}{P}_{\frac{T_{sc}}{2}}(t-i\frac{T_{sc}}{2},\mathrm{\&rho;})\&rsqb;\sin \left(2{\mathrm{\&pi;f}}_{car}t\right)\end{array};$

Based on time domain raised cosine pulse three grades of symbol cosine phase offset carrier (boc) modulated signals M _{tDRC-TOCc (n, m, ρ)}(t) be:

$\begin{array}{c}{M}_{TDRC-TOCc(n,m,\mathrm{\&rho;})}\left(t\right)=\&lsqb;d\left(t\right)\underset{l=0}{\overset{L-1}{\&Sigma;}}{a}_{l}rect(t-{\mathrm{lT}}_c)\&times;sign\left(\cos \right(2{\mathrm{\&pi;f}}_{sc}t\left)\right)\&times;\underset{i=0}{\overset{+\mathrm{\&infin;}}{\&Sigma;}}{P}_{\frac{T_{sc}}{4}}(t-i\frac{T_{sc}}{4},\mathrm{\&rho;})\&rsqb;\cos \left(2{\mathrm{\&pi;f}}_{car}t\right)\\ +\&lsqb;p\left(t\right)\underset{l=0}{\overset{L-1}{\&Sigma;}}{b}_{l}rect(t-{\mathrm{lT}}_c)\&times;sign\left(\cos \right(2{\mathrm{\&pi;f}}_{sc}t\left)\right)\&times;\underset{i=0}{\overset{+\mathrm{\&infin;}}{\&Sigma;}}{P}_{\frac{T_{sc}}{4}}(t-i\frac{T_{sc}}{4},\mathrm{\&rho;})\&rsqb;\sin \left(2{\mathrm{\&pi;f}}_{car}t\right)\end{array};$

Wherein d (t) is navigation signal data channel information; P (t) is pilot channel information, and value is complete+1 or-1; a _ll spreading code of in-phase branch pseudorandom spreading sequence; b _kit is a kth spreading code of quadrature branch pseudorandom spreading sequence; f _carit is carrier frequency.

(4) a kind of Performance Evaluation carrying out navigation signal based on time domain raised cosine pulse three grades of symbol offset carrier (boc) modulated signals will obtained in step (3), if the code tracking precision of signal, anti-multipath and compatibility do not meet designed navigational system performance requirement and constraint condition, then return step (1), redefine spreading code frequency f _cor spreading code cycle T _c, sub-carrier frequencies f _scor subcarrier cycle T _sc, sinusoidal or cosine phase subcarrier modulation modes, and time domain raised cosine pulse time width dutycycle ρ.

Described spreading code frequency f _cwith sub-carrier frequencies f _scvalue be the integral multiple of 1.023MHz.

Described based on time domain raised cosine pulse three grades of symbol sinusoidal phase offset carrier baseband modulation signal power spectrum density G _{tDRC-TOCs (n, m, ρ)}(f) be:

Described based on time domain raised cosine pulse three grades of symbol cosine phase offset carrier baseband modulation signal power spectrum density G _{tDRC-TOCc (n, m, ρ)}(f) be:

Wherein h is modulation index, namely or

The power spectrum density of TDRC-TOC signal embodiment under different time domain raised cosine pulse time width dutycycle ρ that Fig. 3 carries for the present invention, as seen from the figure, by the change of time domain raised cosine pulse time width dutycycle ρ, we can change the separation degree of power spectrum signal main lobe flexibly, and along with the increase of ρ, the main lobe concentration degree of power spectrum can be higher.Therefore, in order to better compatible with existing navigation signal, realize better navigator fix performance, this adds the dirigibility of navigation signal design undoubtedly.

The power spectrum density of the TDRC-TOC embodiment signal that Fig. 4 carries for traditional BOC and the present invention, as shown in Figure 4, near zero-frequency, TDRC-TOCs (5,2,0.9) signal has lower power spectrum amplitude, can show with existing navigation signal BPSK better compatible, simultaneously near ± 10MHz, TDRC-TOCs (5,2,0.9) signal has higher power, and this contributes to the tracking accuracy and the ability of anti-multipath that improve navigation signal.At HFS, the side lobe attenuation speed of TDRC-TOCs (5,2,0.9) signal is faster and amplitude is lower, not only improves the power usefulness of signal, and reduces the interference to signal between same frequency range neighbour.

Fig. 5 and Fig. 6 is respectively the Gabor bandwidth sum code tracking precision of the TDRC-TOC embodiment signal that traditional BOC and the present invention put forward, its loop bandwidth B _l=1Hz.As shown in Figure 5, when receiver bandwidth is within the scope of 10-30MHz, TDRC-TOCs (5,2,0.9) the signal Gabor bandwidth that the present invention carries obviously is greater than BOCs (5,2,0.9) signal.For 24MHz commercial receiver conventional at present, TDRC-TOCs (5,2, the 0.9) signal that the present invention carries has higher Gabor bandwidth, can show better tracking performance.Meanwhile, as can be seen from Fig. 6 also, the TDRC-TOCs (5,2,0.9) that the present invention carries has lower code tracking error, can obtain higher tracking accuracy.

Fig. 7 and Fig. 8 is respectively the multipath error envelope of the TDRC-TOC embodiment signal that traditional BOC and the present invention carry and average multipath error curve.In emulation, choosing related interval is 0.1chip, and receiver bandwidth is 24MHz, and the Amplitude Ratio MDR of multipath signal and direct signal is-6dB.As can be seen from Figure 7, the TDRC-TOCs (5 that the present invention carries, 2, 0.9) signal is relative to BOCs (5, 2) signal has less multipath error amplitude, and the increase of extra latency along with the relative direct signal of multipath signal, TDRC-TOCs (5, 2, 0.9) the multipath error curve of signal has the rate of decay faster, can restrain faster, Fig. 8 shows TDRC-TOCs (5 simultaneously, 2, 0.9) the maximum average multipath error amplitude of signal is lower than BOCs (5, 2) signal, therefore, the TDRC-TOCs (5 that the present invention carries, 2, 0.9) signal embodiment has very strong ability of anti-multipath compared with traditional B OC signal.

In sum, the present invention is not restricted to the described embodiments, what describe in above-described embodiment and instructions just illustrates principle of the present invention, the one that the present invention carries is based on time domain raised cosine pulse three grades of symbol offset carrier modulating methods, navigation signal is made to have better code tracking performance, anti-interference, anti-multipath and the compatibility with other system signal, and effectively suppress power spectrum significantly secondary lobe improve the frequency usefulness of navigation signal, improve the dirigibility of navigation signal Waveform Design, signal waveform design for the following Compass satellite navigation system of China provides a new selection.

Claims (3)

1., based on time domain raised cosine pulse three grades of symbol offset carrier modulating methods, it is characterized in that comprising the following steps:

(1) spreading code cycle T is first determined _c, subcarrier cycle T _sc, time domain raised cosine pulse time width dutycycle ρ, sinusoidal or cosine phase subcarrier modulation modes, constructs or cosine phase sub-carrier signal sinusoidal based on time domain raised cosine pulse three grades of symbols, is specifically expressed as:

Based on time domain raised cosine pulse three grades of symbol sinusoidal phase sub-carrier signal q _s(t, ρ) is:

Based on time domain raised cosine pulse three grades of symbol cosine phase sub-carrier signal q _c(t, ρ) is:

Wherein P _τthe time domain raised cosine pulse shape of (t, ρ) to be time width be ρ τ, namely sign (t) is sign function, namely

(2) according to the spreading code cycle T determined _cwith subcarrier cycle T _scpseudo-random sequence is utilized to carry out spread spectrum to navigation signal, then the spread-spectrum signal obtained and step (1) determined sine or cosine phase sub-carrier signal are carried out time domain multiplication, obtain a kind of based on time domain raised cosine pulse three grades of symbols sines or cosine phase offset carrier baseband modulation signal, be specifically expressed as:

Based on time domain raised cosine pulse three grades of symbol sinusoidal phase offset carrier baseband modulation signal S _{tDRC-TOCs (n, m, ρ)}(t) be:

Based on time domain raised cosine pulse three grades of symbol cosine phase offset carrier baseband modulation signal S _{tDRC-TOCc (n, m, ρ)}(t) be:

Wherein d (t) is navigation signal data channel information; a _ll spreading code of pseudorandom spreading sequence; L is the chip lengths of pseudo-random sequence; Rect (t) is rectangular door function, namely or or

(3) by a kind of carrier modulation of carrying out quadrature branch based on time domain raised cosine pulse three grades of symbols sines or cosine phase offset carrier baseband modulation signal described in step (2), finally obtain described one based on time domain raised cosine pulse three grades of symbols sines or cosine phase offset carrier (boc) modulated signals, be specifically expressed as:

Based on time domain raised cosine pulse three grades of symbol sinusoidal phase offset carrier (boc) modulated signals M _{tDRC-TOCs (n, m, ρ)}(t) be:

Based on time domain raised cosine pulse three grades of symbol cosine phase offset carrier (boc) modulated signals M _{tDRC-TOCc (n, m, ρ)}(t) be:

Wherein d (t) is navigation signal data channel information; P (t) is pilot channel information, and value is complete+1 or-1; a _ll spreading code of in-phase branch pseudorandom spreading sequence; b _kit is a kth spreading code of quadrature branch pseudorandom spreading sequence; f _carit is carrier frequency.

(4) a kind of Performance Evaluation carrying out navigation signal based on time domain raised cosine pulse three grades of symbol offset carrier (boc) modulated signals will obtained in step (3), if the code tracking precision of signal, anti-multipath and compatibility do not meet designed navigational system performance requirement and constraint condition, then return step (1), redefine spreading code cycle T _c, subcarrier cycle T _sc, sinusoidal or cosine phase subcarrier modulation modes, and time domain raised cosine pulse time width dutycycle ρ.

2. according to claim 1ly to it is characterized in that based on time domain raised cosine pulse three grades of symbol offset carrier modulating methods, described spreading code frequency f _cwith sub-carrier frequencies f _scvalue be the integral multiple of 1.023MHz.

3. according to claim 1ly to it is characterized in that based on time domain raised cosine pulse three grades of symbol offset carrier modulating methods, described based on time domain raised cosine pulse three grades of symbol sinusoidal phase offset carrier baseband modulation signal power spectrum density G _{tDRC-TOCs (n, m, ρ)}(f) be:

Described based on time domain raised cosine pulse three grades of symbol cosine phase offset carrier baseband modulation signal power spectrum density G _{tDRC-TOCc (n, m, ρ)}(f) be:

Wherein h is modulation index, namely or