CN104849732A - BOC radio frequency navigation signal tracking method - Google Patents

Abstract

Aiming to solve the multimodal problem of BOC signals, the invention provides a BOC radio frequency navigation signal tracking method which has a unique tracking idea, and is suitable for BOC (m, n) tracking. Firstly, a carrier wave signal substitutes for a subcarrier signal to generate a BPSK signal; signals are captured through a BPSK method to eliminate signal multimodal. When signals are captured, the signals are tracked through a BPSK method; meanwhile, in dependence on changes of a digital frequency synthesizer code phase accumulator used for generating spreading codes, subcarrier signals are generated in real time, and the subcarrier signals and the spreading codes are multiplied to generate new spreading codes. When carrier wave/code loop circuit tracking is stabilized, the local oscillator frequency parameter of a carrier wave digital frequency synthesizer is changed to generate new carrier waves; meanwhile the spreading codes are switched into new spreading codes, and the carrier waves are switched into new carrier waves to track signals and realize higher tracking precision. In the scheme, the BOC radio frequency navigation signal tracking method has the characteristics of simple structure, less resource consumption and strong versatility, and can effectively reduce FPGA power consumption.

Description

A kind of binary offset carrier radio frequency navigation signal trace method

Technical field

The present invention a kind of navigation signal tracking, particularly a kind of binary offset carrier radio frequency navigation signal trace method, belong to satellite navigation signals and receive field.

Background technology

Along with GPS, Galileo, GLONASS and Beidou navigation development, create novel signal modulation system, i.e. BOC (scale-of-two carrier modulation).Novel B OC signal has the frequency spectrum of fission, changes corresponding parameter and can change navigation signal frequency spectrum at center frequency point right position; BOC signal has multimodal and narrow relevant peaks characteristic, and narrow relevant peaks improves tracking accuracy and the antijamming capability of signal, and multimodal characteristic to correctly the catching of signal, follow the tracks of and propose certain challenge.

At present for the multimodal characteristic of BOC signal, Chinese scholars proposes much improves one's methods.The double-side band acquisition algorithm that Fishman proposes, BOC signal is regarded as the BPSK (m) of two sidebands and, by carrying out BPSK process after front end filter filtering.Its shortcoming comprises:

A) increase front end filter, add the complexity of system;

B) two wave filters are inconsistent also can bring error;

C) tracking accuracy of disposal route to signal of BPSK also has a certain impact.

The method for capturing and tracing of the BPSK_LIKE that Martin proposes is by BOC (n, m) signal and frequency are relevant with local pseudo-code after two carrier multiplication of FC-FS and FC+FS, implementation procedure is very simple, its autocorrelation function and BPSK very similar.BPSK_LIKE can solve multiple peak problem, and shortcoming is that the tracking accuracy of tracking accuracy relevant peaks narrower than BOC is far short of what is expected, is normal BOC narrow relevant peaks tracking accuracy half for BOC (1,1) its tracking accuracy.

Olivier Julien proposes ASPeCT correlation technique in its PhD dissertation, the method adopts cross correlation function two kinds of related functions of BOC modulation signal autocorrelation function and pseudo-code and BOC modulation signal to subtract each other, and eliminates the wing of BOC modulation signal autocorrelation function.The method shortcoming is only applicable to the subcarrier modulation signal identical with pseudo-bit rate.

The BOC tracking patented method that Yang Zaixiu, Geng Shengqun etc. of BJ University of Aeronautics & Astronautics deliver adopts three ring trackings, pseudo-code, subcarrier and carrier wave is adopted three loops to follow the tracks of respectively, wherein subcarrier is used as a yard ring and follows the tracks of.The method well solves the problem of multimodal, the method shortcoming complicated structure, and many subcarrier track loop, resource occupation amount is large.

In some documents at home, subcarrier null method is proposed.Utilize and estimate that the method for carrier wave carrys out estimator carrier wave, thus eliminate correlativity, produce an in-phase component and quadrature component (by the sub-carrier offset cycle) for subcarrier, be equivalent to by signal " sub-carrier space " and in Orthogonal Decomposition again.Specific practice is: first produce an in-phase component and quadrature component according to carrier wave; Then each component is decomposed further, namely produce one group of inphase/orthogonal component more respectively for subcarrier; These four signals are done respectively summed square after coherent integration with Received signal strength.The autocorrelation function finally obtained has good unimodality.The major defect of the method is complicated structure, needs a large amount of correlators.

Summary of the invention

The technical matters that the present invention solves is: overcome the deficiencies in the prior art, provide a kind of binary offset carrier radio frequency navigation signal trace method, combine the feature that BPSK follows the tracks of and BOC follows the tracks of, the tracking of binary offset carrier radio frequency navigation signal can be completed quickly and accurately, tracking accuracy is high, resource occupation is little, meets the demand of binary offset carrier radio frequency navigation signal trace to the full extent.

Technical solution of the present invention is: a kind of binary offset carrier radio frequency navigation signal trace method, and step is as follows:

(1) FPGA receives binary offset carrier radio frequency navigation signal BOC (n, m), and after radio frequency navigation signal BOC (n, m) is down-converted to intermediate-freuqncy signal, then to obtain intermediate frequency be f through analog to digital converter sampling ₀digital navigation signal BOC _iF(n, m);

(2) FPGA generates local BPSK spread spectrum codes C ode by code digital frequency synthesizer _bpsk_ local, the bit rate of described local BPSK spreading code is f _c=m*1.023MHz; The frequency control word of BPSK spreading code wherein N is the bit wide of phase accumulator in yard digital frequency synthesizer, f _clkfor the work master clock frequency of FPGA, will abbreviation is the fractional form not having minimum common divisor after, the phase accumulator bit wide of digital frequency synthesizer is expanded and equals N+m'-1 for N', described N';

(3) local subcarrier Code is generated according to the phase accumulator of BPSK spreading code change local in step (2) _{deputy_carr}_ local, described local subcarrier bit rate is f _c'=n*1.023MHz;

(4) adjust local BPSK spreading code and local subcarrier, make to be alignd by the upset moment that 0 jumps to 1 by the 0 upset moment jumping to 1 and local subcarrier at local spreading code;

(5) local intermediate frequency carrier Carr is generated by carrier wave digital frequency synthesizer _bpsk_ local, and utilize the local BPSK spreading code generating center frequency in local intermediate frequency carrier and step (2) to be (f ₀+ n*1.023) bpsk signal of MHz, described local intermediate frequency carrier centre frequency is f _iF=(f ₀+ n*1.023) MHz; The carrier frequency control word of local carrier digital frequency synthesizer is wherein M is the bit wide of phase accumulator in carrier wave digital frequency synthesizer;

(6) frequency obtained in step (5) is utilized to be (f ₀+ n*1.023) bpsk signal of MHz replaces the centre frequency obtained in step (1) to be f ₀intermediate frequency navigation signal BOC _iF(n, m) carries out navigation signal and catches, and obtains rough code phase and the carrier frequency frequency deviation of radio frequency navigation signal, and obtains centre frequency for (f ₀+ df _carr+ n*1.023) bpsk signal of MHz, wherein df _carrfor catching the carrier Doppler frequency obtained;

(7) carrier frequency and the code phase generating center frequency that utilize acquisition in step (6) are local trace intermediate frequency carrier and local trace BPSK spread spectrum codes C ode ' _{deputy_carr}_ local, the centre frequency of described local trace intermediate frequency carrier is (f ₀+ df _carr+ n*1.023) MHz; The bit rate of described local trace BPSK spreading code is ${f_c}^{\′}=(f_c+\frac{{\mathrm{df}}_{\mathrm{carr}}}{N1})\mathrm{MHz},$ Wherein described floor (x) represents that x integral part rounds downwards;

(8) local subcarrier Code ' is generated according to the phase accumulator of BPSK spreading code digital frequency synthesizer local in step (7) _{deputy_carr}_ local, described local subcarrier bit rate is

(9) the local trace intermediate frequency carrier of generation in step (7) and local trace BPSK spreading code is utilized to carry out the tracking of radio frequency navigation signal; Described tracking employing two ring is followed the tracks of, and is respectively carrier tracking loop and code tracking loop;

(10) carry out locking judgement to the second order filter of carrier wave phase demodulation ring and code phase demodulation ring respectively, whether the tracking of determining step (9) stablizes, and is specially:

The current output valve Acc_carr (n) of totalizer of carrier wave phase demodulation ring second order filter and last accumulator output values Acc_carr (n-1) are subtracted each other and obtains difference Accdt_carr, if difference Accdt_carr is continuous be less than default thresholding C1 for K1 time, then carrier loop is followed the tracks of stable, outgoing carrier loop-locking mark; Otherwise carrier loop is followed the tracks of unstable, carrier loop proceeds to follow the tracks of; Current for the totalizer of code second order filter output valve Acc_code (n) and last accumulator output values Acc_code (n-1) are subtracted each other and obtains difference Accdt_code, if difference Accdt_code is continuous be less than default thresholding C2 for K2 time, then code loop tracks is stablized, output code loop-locking mark; Otherwise code loop tracks is unstable, code loop proceeds to follow the tracks of;

If carrier loop and code loop all lock, then export loop lock flag, enter step (11);

(11) by local subcarrier Code ' that step (8) obtains _{deputy_carr}_ local and the middle local trace BPSK spread spectrum codes C ode ' produced of step (7) _{deputy_carr}_ local is multiplied, and produces a new local trace spread-spectrum code signals Code_boc=Code ' _bpsk_ local*Code ' _{deputy_carr}_ local; The bit rate of described local spread-spectrum code signals is ${f_c}^{\′\′\′}=\frac{2*n}{m}*1.023\mathrm{MHz};$

(12) local trace intermediate frequency carrier Carr ' ' is generated by carrier wave digital frequency synthesizer _boc_ local, the centre frequency of described local intermediate frequency carrier is f _iF=(f ₀+ df _carr) MHz;

(13) the local trace intermediate frequency carrier Carr ' ' generated in step (12) is utilized _bocthe local trace spread spectrum codes C ode_boc that _ local and step (11) produce carries out the tracking of radio frequency navigation signal; Described tracking employing two ring is followed the tracks of, and is respectively carrier tracking loop and code tracking loop;

(14) whether the carrier tracking loop in determining step (13) and code tracking loop lock, if carrier tracking loop and code tracking loop all lock, then carry out follow-up process, if losing lock, then return step (2), if carrier tracking loop and code tracking loop have a non-locking or equal non-locking, then return step (13), proceed to follow the tracks of.

Local subcarrier generation method in described step (3) and step (8) is specially:

Parameter obtain not having the mark of common divisor be after abbreviation the phase accumulator that code digital frequency synthesizer is not expanded is N, and the phase accumulator bit wide after expansion is that N', N' equal N+m'-1, order ${\mathrm{NCO}}^{\′}=\mathrm{Mod}\left(\frac{\mathrm{NCO}*n^{\′}}{2^N*m^{\′}}\right);$

The BOC signal subcarrier generating mode of sin type is:

the expression of described ceil (x) rounds up, if i is 0, then and Code _{deputy_carr}_ local equals 1, if i is 1, then and Code _{deputy_carr}_ local equals 0;

The BOC signal subcarrier generating mode of cos type is:

the expression of described ceil (x) rounds up, if i is 0 or 3, then and Code _{deputy_carr}_ local equals 1, if i is 1 or 2, then and Code _{deputy_carr}_ local equals 0.

The scope of described K1 is: the scope of 15 ~ 1000, C1 is: 30 ~ 500; The scope of K2 is: the scope of 15 ~ 1000, C2 is 3 ~ 300.

The present invention's beneficial effect is compared with the conventional method:

(1) the present invention first have employed BPSK tracking, the narrow relevant peaks that tracing process can be locked in radio frequency navigation signal is carried out, effectively can eliminate the multimodal that BOC signal produces, effectively improve the reliability of tracking, reduce the complexity that follow-up BOC follows the tracks of;

(2) the present invention adopts two stage tracking, and the first stage follows the tracks of the multimodal eliminating BOC signal and produce, and subordinate phase ensure that the precision of tracking, and tracking accuracy is high;

(3) in the present invention, the generation of each local subcarrier does not need additionally to increase local subcarrier generation module, produce according to code digital frequency synthesizer completely, Doppler's change is released according to the change of code digital frequency synthesizer, and resource occupation is few, is conducive to realizing in FPGA;

(4) the present invention can be applicable to the tracking of BOC (n, m) signal under different parameters condition, does not affect, highly versatile by multimodal.

Accompanying drawing explanation

Fig. 1 is process flow diagram of the present invention;

Fig. 2 is system architecture diagram of the present invention.

Embodiment

Figure 2 shows that system architecture diagram of the present invention, as shown in Figure 2, the system in the present invention comprises as lower module:

Carrier wave generation module, this module generates according to parameter needs carrier signal, carries out signal capture, tracking.

Code generation module: this module generates according to parameter needs spread-spectrum code signals, carries out signal capture, tracking

Signal capture module: adopt the acquisition mode of BPSK to catch signal, obtain the rough code phase/carrier phase of signal.

Integrate-dump block, for following the tracks of signal, produces instant, advanced, the lag correlation branch road correlation on I road and Q road, and is sent to that carrier wave/code loop module carries out phase demodulation, filtering, frequency control word calculate;

Carrier loop module: the phase demodulation of carrier wave is carried out to I, Q correlation of input, filtering, carrier frequency control word calculate.

Code loop module: the phase demodulation of pseudo-code is carried out to advanced, instant, the lag correlation value of input, filtering, code frequency control word calculate.

Carrier wave/code loop-locking detects: judge carrier loop, code loop-locking state, result of determination is fed back to carrier wave generation module and code generation module, carries out carrier wave/pseudo-code and switches, carry out meticulous tracking.

Be illustrated in figure 1 process flow diagram of the present invention, as shown in Figure 1, provided by the invention kind of binary offset carrier radio frequency navigation signal trace method, step is as follows:

(1) FPGA receives binary offset carrier radio frequency navigation signal BOC (n, m), and after radio frequency navigation signal BOC (n, m) is down-converted to intermediate-freuqncy signal, then to obtain intermediate frequency be f through analog to digital converter sampling ₀digital navigation signal BOC _iF(n, m);

(2) FPGA generates local BPSK spread spectrum codes C ode by code digital frequency synthesizer _bpsk_ local, the bit rate of described local BPSK spreading code is f _c=m*1.023MHz; The frequency control word of BPSK spreading code wherein N is the bit wide of phase accumulator in yard digital frequency synthesizer, f _clkfor the work master clock frequency of FPGA, will abbreviation is the fractional form not having minimum common divisor after, expand the phase accumulator bit wide of digital frequency synthesizer for N', described N' equals N+m'-1 bit wide.Such as BOC (15,10), will abbreviation is do not have the fractional form of minimum common divisor to be 2/3, and therefore in real figure frequency synthesizer, the bit wide of phase accumulator is N+2-1, and namely N' equals N+1 bit.

(3) local subcarrier Code is generated according to the phase accumulator of BPSK spreading code change local in step (2) _{deputy_carr}_ local, described local subcarrier bit rate is f _c'=n*1.023MHz;

Parameter obtain not having the mark of common divisor be after abbreviation the phase accumulator that code digital frequency synthesizer is not expanded is N, and the phase accumulator bit wide after expansion is that N', N' equal N+m'-1, order ${\mathrm{NCO}}^{\′}=\mathrm{Mod}\left(\frac{\mathrm{NCO}*n^{\′}}{2^N*m^{\′}}\right);$

The BOC signal subcarrier generating mode of sin type is:

the expression of described ceil (x) rounds up, if i is 0, then and Code _{deputy_carr}_ local equals 1, if i is 1, then and Code _{deputy_carr}_ local equals 0;

The BOC signal subcarrier generating mode of cos type is:

the expression of described ceil (x) rounds up, if i is 0 or 3, then and Code _{deputy_carr}_ local equals 1, if i is 1 or 2, then and Code _{deputy_carr}_ local equals 0.

(4) adjust local BPSK spreading code and local subcarrier, make to be alignd by the upset moment that 0 jumps to 1 by the 0 upset moment jumping to 1 and local subcarrier at local spreading code;

(5) local intermediate frequency carrier Carr is generated by carrier wave digital frequency synthesizer _bpsk_ local, and utilize the local BPSK spreading code generating center frequency in local intermediate frequency carrier and step (2) to be (f ₀+ n*1.023) bpsk signal of MHz, described local intermediate frequency carrier centre frequency is f _iF=(f ₀+ n*1.023) MHz; The carrier frequency control word of local carrier digital frequency synthesizer is wherein M is the bit wide of phase accumulator in carrier wave digital frequency synthesizer;

(6) the new frequency obtained in step (5) is utilized to be (f ₀+ n*1.023) bpsk signal of MHz replaces the centre frequency obtained in step (1) to be f ₀intermediate frequency navigation signal BOC _iF(n, m) carry out navigation signal to catch, the method of catching can select time domain sliding correlation method, matched filtering algorithm, based on time domain fast search algorithm and the larger frequency fast Acquisition algorithm of resource occupation according to design itself strategy, when the contact conditions of selected algorithm is greater than detection threshold, obtain rough code phase and the carrier frequency frequency deviation of radio frequency navigation signal, and obtain centre frequency for (f ₀+ df _carr+ n*1.023) bpsk signal of MHz, wherein df _carrfor catching the carrier Doppler frequency obtained;

(7) carrier frequency and the code phase generating center frequency that utilize acquisition in step (6) are local trace intermediate frequency carrier and local trace BPSK spread spectrum codes C ode ' _{deputy_carr}_ local, the centre frequency of described local trace intermediate frequency carrier is (f ₀+ df _carr+ n*1.023) MHz; The bit rate of described local trace BPSK spreading code is ${f_c}^{\′}=(f_c+\frac{{\mathrm{df}}_{\mathrm{carr}}}{N1})\mathrm{MHz},$ Wherein described floor (x) represents that x integral part rounds downwards;

(8) local subcarrier Code ' is generated according to the phase accumulator of BPSK spreading code digital frequency synthesizer local in step (7) _{deputy_carr}_ local, described local subcarrier bit rate is

Parameter obtain not having the mark of common divisor be after abbreviation the phase accumulator that code digital frequency synthesizer is not expanded is N, and the phase accumulator bit wide after expansion is that N', N' equal N+m'-1, order ${\mathrm{NCO}}^{\′}=\mathrm{Mod}\left(\frac{\mathrm{NCO}*n^{\′}}{2^N*m^{\′}}\right);$

The BOC signal subcarrier generating mode of sin type is:

the expression of described ceil (x) rounds up, if i is 0, then and Code _{deputy_carr}_ local equals 1, if i is 1, then and Code _{deputy_carr}_ local equals 0;

The BOC signal subcarrier generating mode of cos type is:

the expression of described ceil (x) rounds up, if i is 0 or 3, then and Code _{deputy_carr}_ local equals 1, if i is 1 or 2, then and Code _{deputy_carr}_ local equals 0.

(9) the local trace intermediate frequency carrier of generation in step (7) and local trace BPSK spreading code is utilized to carry out the tracking of radio frequency navigation signal; Described tracking employing two ring is followed the tracks of, and is respectively carrier tracking loop and code tracking loop;

(10) carry out locking judgement to the second order filter of carrier wave phase demodulation ring and code phase demodulation ring respectively, whether the tracking of determining step (9) stablizes, and is specially:

The current output valve Acc_carr (n) of totalizer of carrier wave phase demodulation ring second order filter and last accumulator output values Acc_carr (n-1) are subtracted each other and obtains difference Accdt_carr, if difference Accdt_carr is continuous be less than default thresholding C1 for K1 time, then carrier loop is followed the tracks of stable, outgoing carrier loop-locking mark; Otherwise carrier loop is followed the tracks of unstable, carrier loop proceeds to follow the tracks of; The scope of K1 is: the scope of 15 ~ 1000, C1 is: 30 ~ 500;

Current for the totalizer of code second order filter output valve Acc_code (n) and last accumulator output values Acc_code (n-1) are subtracted each other and obtains difference Accdt_code, if difference Accdt_code is continuous be less than default thresholding C2 for K2 time, then code loop tracks is stablized, output code loop-locking mark; Otherwise code loop tracks is unstable, code loop proceeds to follow the tracks of; The scope of K2 is: the scope of 15 ~ 1000, C2 is: 3 ~ 300;

If carrier loop and code loop all lock, then export loop lock flag, enter step (11);

(11) by local subcarrier Code ' that step (8) obtains _{deputy_carr}_ local and the middle local trace BPSK spread spectrum codes C ode ' produced of step (7) _{deputy_carr}_ local is multiplied, and produces a new local trace spread-spectrum code signals Code_boc=Code _b' _psk_ local*Code ' _{deputy_carr}_ local; The bit rate of described local spread-spectrum code signals is ${f_c}^{\′\′\′}=\frac{2*n}{m}*1.023\mathrm{MHz};$

(12) local trace intermediate frequency carrier Carr ' ' is generated by carrier wave digital frequency synthesizer _boc_ local, the centre frequency of described local intermediate frequency carrier is f _iF=(f ₀+ df _carr) MHz;

(13) the local trace intermediate frequency carrier Carr ' ' generated in step (12) is utilized _bocthe local trace spread spectrum codes C ode_boc that _ local and step (11) produce carries out the tracking of radio frequency navigation signal; Described tracking employing two ring is followed the tracks of, and is respectively carrier tracking loop and code tracking loop;

(14) whether the carrier tracking loop in determining step (13) and code tracking loop lock, if carrier tracking loop and code tracking loop all lock, then carry out follow-up process, if losing lock, then return step (2), if carrier tracking loop and code tracking loop have a non-locking or equal non-locking, then return step (13), proceed to follow the tracks of.

Embodiment

Now with the B1 frequency signal BOC (1,1) of Galileo for example, the implementation process of described patent is described.The frequency of the B1 frequency of Galileo is 1575.42MHz, supposes the centre frequency 30MHz after down coversion, and FPGA system work clock is 100MHz.Concrete steps are as follows:

(1) the digital navigation signal BOC that intermediate frequency is 30MHz is obtained through down coversion, analog to digital converter after adopting _30MHz(n, m);

(2) local BPSK spread spectrum codes C ode is generated by code digital frequency synthesizer _bpsk_ local, the bit rate of described local BPSK spreading code is f _c=1.023MHz, if digital frequency synthesizer phase accumulator bit wide is 32bit, described BOC's (1,1) without minimum common divisor, namely 1/1, real figure frequency synthesizer phase accumulator bit wide 32+1-1, equals 32bit; , FPGA system work clock is the frequency control word of 100MHz, BPSK spreading code ${\mathrm{FCW}}_{\mathrm{Code}}=\frac{f_c*2^N}{f_{\mathrm{clk}}}=\frac{1.023*2^{32}}{100}=43937515.43808,$ Frequency control word after rounding downwards in FPGA is 43937515;

(3) local subcarrier Code is generated according to the phase accumulator of BPSK spreading code change local in step (2) _{deputy_carr}_ local, described local subcarrier bit rate is f _c'=1.023MHz;

Generative process is: code digital frequency synthesizer phase accumulator instantaneous phase is NCO, and bit wide is N', i.e. 32bit, parameter obtain not having the mark of common divisor be after abbreviation order the expression of described ceil (x) rounds up.If i is even number and 0≤i<n*m-1, then Code _{deputy_carr}_ local equals 1, if i is odd number and 0<i≤n*m-1, then and Code _{deputy_carr}_ local equals 0;

(4) in FPGA, adjust local BPSK spreading code and local subcarrier, make to be alignd by the upset moment that 0 jumps to 1 by the 0 upset moment jumping to 1 and local subcarrier at local spreading code;

(5) local intermediate frequency carrier Carr is generated by carrier wave digital frequency synthesizer _bpsk_ local, and utilize the local BPSK spreading code generating center frequency in local intermediate frequency carrier and step (2) to be the bpsk signal of 31.023MHz; Suppose that carrier wave digital frequency synthesizer phase accumulator M is 32bit, the carrier frequency control word of described local carrier digital frequency synthesizer is ${\mathrm{FCW}}_{\mathrm{Carr}1}=\frac{f_{\mathrm{IF}}*2^M}{\mathrm{fclk}}=\frac{31.023*2^32}{100}=1332427704.23808,$ In order to realize in FPGA, get its integral part as the frequency control word in FPGA, namely 1332427704;

(6) the new frequency obtained in step (5) is utilized to be that the bpsk signal of 31.023MHz replaces centre frequency that in step (1), down coversion obtains to be the intermediate frequency navigation signal BOC of 30MHz _30MHz(1,1) carry out navigation signal to catch, catching method adopts time domain sliding correlation method, i.e. slip carrier frequency in the time domain and code phase, export a code cycle 10ms carrier frequency and signal energy corresponding to code phase, when signal energy is greater than detection threshold 100000, obtain rough code phase and the carrier frequency frequency deviation of radio frequency navigation signal, suppose that carrier frequency frequency deviation is 100Hz, obtain centre frequency for (f _c+ df _carr+ n*1.023) bpsk signal of MHz, i.e. 31.123MHz;

(7) carrier frequency and the code phase generating center frequency that utilize acquisition in step (6) are local trace intermediate frequency carrier and local trace BPSK spread spectrum codes C ode ' _bpsk_ local, the centre frequency of described local trace intermediate frequency carrier is 31.123MHz; The bit rate of described local trace BPSK spreading code is wherein 154 be calculated as follows formula described floor (x) represents that x integral part rounds downwards.Keep institute in (6) to catch the rough code phase obtained, only change the frequency control word change of the code digital frequency synthesizer caused because bit rate change, namely code frequency control word is by original 43937515.43808 changes 43937543.43808.

(8) local subcarrier Code ' is generated according to the phase accumulator of BPSK spreading code change local in step (7) _{deputy_carr}_ local;

Generative process is: the instant phase place of code digital frequency synthesizer phase accumulator is NCO, and bit wide is N', i.e. 32bit, parameter obtain not having the mark of common divisor be after abbreviation order the expression of described ceil (x) rounds up.If i is even number and 0≤i<n*m-1, then Code _{deputy_carr}_ local equals 1, if i is odd number and 0<i≤n*m-1, then and Code _{deputy_carr}_ local equals 0;

(9) the local trace intermediate frequency carrier of generation in step (7) and local trace BPSK spreading code is utilized to carry out the tracking of radio frequency navigation signal; Described tracking employing two ring is followed the tracks of, and is respectively carrier tracking loop and code tracking loop;

(10) carry out locking judgement to the second order filter of carrier wave phase demodulation ring and code phase demodulation ring respectively, whether the tracking of determining step (9) stablizes, and is specially:

The current output valve Acc_carr (n) of totalizer of carrier wave phase demodulation ring second order filter and last accumulator output values Acc_carr (n-1) are subtracted each other and obtains difference Accdt_carr, if difference Accdt_carr is continuous be less than default thresholding 100 for 25 times, then carrier loop is followed the tracks of stable, is locked by carrier loop; Otherwise carrier loop is followed the tracks of unstable, carrier loop proceeds to follow the tracks of;

Current for the totalizer of code second order filter output valve Acc_code (n) and last accumulator output values Acc_code (n-1) are subtracted each other and obtains difference Accdt_code, if difference Accdt_code is continuous be less than default thresholding 50 for 25 times, then code loop tracks is stablized, by code loop-locking; Otherwise code loop tracks is unstable, code loop proceeds to follow the tracks of;

If carrier loop and code loop all lock, then export loop lock flag, enter step (11);

(11) by local subcarrier Code ' that step (8) obtains _{deputy_carr}_ local and the middle local trace BPSK spread spectrum codes C ode ' produced of step (7) _bpsk_ local is multiplied, and produces a new local trace spread-spectrum code signals Code_boc=Code ' _bpsk_ local*Code ' _{deputy_carr}_ local; The bit rate of described local spread-spectrum code signals is 2.04600129MHz;

(12) local trace intermediate frequency carrier Carr ' ' is generated by carrier wave digital frequency synthesizer _boc_ local, the centre frequency of described local intermediate frequency carrier is f _iF=(f ₀+ df _carr) MHz=(300+0.1) MHz=30.1MHz

(13) the intermediate frequency carrier Carr ' ' of the local trace 30.1MHz generated in step (12) is utilized _bocthe bit rate that _ local and step (11) produce is the tracking that the local trace spread spectrum codes C ode_boc of 2.04600129MHz carries out radio frequency navigation signal; Described tracking employing two ring is followed the tracks of, and is respectively carrier tracking loop and code tracking loop;

(14) whether the carrier tracking loop in determining step (13) and code tracking loop lock, determination methods is identical with step (10), if carrier tracking loop and code tracking loop all lock, then carry out follow-up process, if losing lock, then return step (2), if carrier tracking loop and code tracking loop route non-locking or all non-locking, then return step (13), proceed to follow the tracks of.

The present invention can follow the tracks of in the narrow relevant peaks of BOC signal, and tracking accuracy is high; Effectively can eliminate the multiple peak problem of BOC signal, resource occupation amount is little, solves and consumes more resource or to reduce precision for cost to eliminate multimodal, is adapted at realizing in FPGA the catching of signal, follows the tracks of, data demodulates; Highly versatile, is suitable for the catching of BOC (n, m) signal, follows the tracks of, data demodulates; Following GPS, GLONESS, GALIEO, BEIDU, in order to realize the relevant compatible interoperation of four Iarge-scale system, have all modulated BOC signal at B1 frequency, all need the catching of BOC signal, follow the tracks of, data demodulates.The present invention can be applicable to the reception of BOC signal in following navigation signal receiver.

The content be not described in detail in instructions of the present invention belongs to the known technology of professional and technical personnel in the field.

Claims (3)

1. a binary offset carrier radio frequency navigation signal trace method, is characterized in that step is as follows:

(1) FPGA receives binary offset carrier radio frequency navigation signal BOC (n, m), and after radio frequency navigation signal BOC (n, m) is down-converted to intermediate-freuqncy signal, then to obtain intermediate frequency be f through analog to digital converter sampling ₀digital navigation signal BOC _iF(n, m);

(2) FPGA generates local BPSK spread spectrum codes C ode by code digital frequency synthesizer _bpsk_ local, the bit rate of described local BPSK spreading code is f _c=m*1.023MHz; The frequency control word of BPSK spreading code wherein N is the bit wide of phase accumulator in yard digital frequency synthesizer, f _clkfor the work master clock frequency of FPGA, will abbreviation is the fractional form not having minimum common divisor after, the phase accumulator bit wide of digital frequency synthesizer is expanded and equals N+m'-1 for N', described N';

(3) local subcarrier Code is generated according to the phase accumulator of BPSK spreading code change local in step (2) _{deputy_carr}_ local, described local subcarrier bit rate is f _c'=n*1.023MHz;

(4) adjust local BPSK spreading code and local subcarrier, make to be alignd by the upset moment that 0 jumps to 1 by the 0 upset moment jumping to 1 and local subcarrier at local spreading code;

(5) local intermediate frequency carrier Carr is generated by carrier wave digital frequency synthesizer _bpsk_ local, and utilize the local BPSK spreading code generating center frequency in local intermediate frequency carrier and step (2) to be (f ₀+ n*1.023) bpsk signal of MHz, described local intermediate frequency carrier centre frequency is f _iF=(f ₀+ n*1.023) MHz; The carrier frequency control word of local carrier digital frequency synthesizer is wherein M is the bit wide of phase accumulator in carrier wave digital frequency synthesizer;

(6) frequency obtained in step (5) is utilized to be (f ₀+ n*1.023) bpsk signal of MHz replaces the centre frequency obtained in step (1) to be f ₀intermediate frequency navigation signal BOC _iF(n, m) carries out navigation signal and catches, and obtains rough code phase and the carrier frequency frequency deviation of radio frequency navigation signal, and obtains centre frequency for (f ₀+ df _carr+ n*1.023) bpsk signal of MHz, wherein df _carrfor catching the carrier Doppler frequency obtained;

(7) carrier frequency and the code phase generating center frequency that utilize acquisition in step (6) are local trace intermediate frequency carrier and local trace BPSK spread spectrum codes C ode ' _{deputy_carr}_ local, the centre frequency of described local trace intermediate frequency carrier is (f ₀+ df _carr+ n*1.023) MHz; The bit rate of described local trace BPSK spreading code is ${f_c}^{\&prime;}=(f_c+\frac{{\mathrm{df}}_{\mathrm{carr}}}{N1})\mathrm{MHz},$ Wherein described floor (x) represents that x integral part rounds downwards;

(8) local subcarrier Code ' is generated according to the phase accumulator of BPSK spreading code digital frequency synthesizer local in step (7) _{deputy_carr}_ local, described local subcarrier bit rate is

(9) the local trace intermediate frequency carrier of generation in step (7) and local trace BPSK spreading code is utilized to carry out the tracking of radio frequency navigation signal; Described tracking employing two ring is followed the tracks of, and is respectively carrier tracking loop and code tracking loop;

(10) carry out locking judgement to the second order filter of carrier wave phase demodulation ring and code phase demodulation ring respectively, whether the tracking of determining step (9) stablizes, and is specially:

The current output valve Acc_carr (n) of totalizer of carrier wave phase demodulation ring second order filter and last accumulator output values Acc_carr (n-1) are subtracted each other and obtains difference Accdt_carr, if difference Accdt_carr is continuous be less than default thresholding C1 for K1 time, then carrier loop is followed the tracks of stable, outgoing carrier loop-locking mark; Otherwise carrier loop is followed the tracks of unstable, carrier loop proceeds to follow the tracks of; Current for the totalizer of code second order filter output valve Acc_code (n) and last accumulator output values Acc_code (n-1) are subtracted each other and obtains difference Accdt_code, if difference Accdt_code is continuous be less than default thresholding C2 for K2 time, then code loop tracks is stablized, output code loop-locking mark; Otherwise code loop tracks is unstable, code loop proceeds to follow the tracks of;

If carrier loop and code loop all lock, then export loop lock flag, enter step (11);

(11) by local subcarrier Code ' that step (8) obtains _{deputy_carr}_ local and the middle local trace BPSK spread spectrum codes C ode ' produced of step (7) _{deputy_carr}_ local is multiplied, and produces a new local trace spread-spectrum code signals Code_boc=Code ' _bpsk_ local*Code ' _{deputy_carr}_ local; The bit rate of described local spread-spectrum code signals is ${f_c}^{\&prime;\&prime;\&prime;}=\frac{2*n}{m}*1.023\mathrm{MHz};$

(12) local trace intermediate frequency carrier Carr is generated by carrier wave digital frequency synthesizer " _boc_ local, the centre frequency of described local intermediate frequency carrier is f _iF=(f ₀+ df _carr) MHz;

(13) the local trace intermediate frequency carrier Carr generated in step (12) is utilized " _bocthe local trace spread spectrum codes C ode_boc that _ local and step (11) produce carries out the tracking of radio frequency navigation signal; Described tracking employing two ring is followed the tracks of, and is respectively carrier tracking loop and code tracking loop;

(14) whether the carrier tracking loop in determining step (13) and code tracking loop lock, if carrier tracking loop and code tracking loop all lock, then carry out follow-up process, if losing lock, then return step (2), if carrier tracking loop and code tracking loop have a non-locking or equal non-locking, then return step (13), proceed to follow the tracks of.

2. a kind of binary offset carrier radio frequency navigation signal trace method according to claim 1, is characterized in that: the local subcarrier generation method in described step (3) and step (8) is specially:

Parameter obtain not having the mark of common divisor be after abbreviation the phase accumulator that code digital frequency synthesizer is not expanded is N, and the phase accumulator bit wide after expansion is that N', N' equal N+m'-1, order ${\mathrm{NCO}}^{\&prime;}=\mathrm{Mod}\left(\frac{\mathrm{NCO}*n^{\&prime;}}{2^N*m^{\&prime;}}\right);$

The BOC signal subcarrier generating mode of sin type is:

the expression of described ceil (x) rounds up, if i is 0, then and Code _{deputy_carr}_ local equals 1, if i is 1, then and Code _{deputy_carr}_ local equals 0;

The BOC signal subcarrier generating mode of cos type is:

the expression of described ceil (x) rounds up, if i is 0 or 3, then and Code _{deputy_carr}_ local equals 1, if i is 1 or 2, then and Code _{deputy_carr}_ local equals 0.

3. a kind of binary offset carrier radio frequency navigation signal trace method according to claim 1, is characterized in that: the scope of described K1 is: the scope of 15 ~ 1000, C1 is: 30 ~ 500; The scope of K2 is: the scope of 15 ~ 1000, C2 is 3 ~ 300.