CN209446772U - A kind of Beidou three generations satellite-signal simulation system - Google Patents

Abstract

The utility model discloses a kind of Beidou three generations satellite-signal simulation systems, it is to complete real-time information interaction through RS232 serial ports and FPGA using host computer, user-defined data are issued FPGA by host computer, meanwhile, the information back that itself is stored is used to show by FPGA to host computer.FPGA and DSP completes the real-time, interactive of information by EMIF address wire, and when interrupting arrival, the various parameters of calculating are transmitted to FPGA by DSP, meanwhile, the specific data of storage is returned to DSP and is used to verify by FPGA.Later, the signal of generation is transmitted to up-converter module by FPGA after D/A conversion module, is finally launched by transmitting antenna or radio-frequency cable.The method that the utility model uses program module to share, baseband board completes the processing to baseband signal using the mode that DSP+FPGA is combined, to effectively shorten the R&D cycle, reduces simulator hardware cost, facilitates test environment construction.

Description

A kind of Beidou three generations satellite-signal simulation system

Technical field

The utility model relates to Technique of Satellite Navigation and Positioning, specifically a kind of Beidou three generations satellite-signal simulation system.

Background technique

GNSS (Global Navigation Satellite System) is that satellite is led i.e. " Global Navigation Satellite System " The general designation of boat system, the GPS comprising the U.S., Russia GLONASS, China BDS, European Union Galileo system.So far Until, can be realized the worldwide navigation positioning system of Global coverage only there are two, one be the U.S. GPS global positioning satellite system System, the other is the GLONASS system of Russia.Currently, the establishment of Beidou II satellite navigation system is perfect not enough, it can not Realize Global coverage, coverage is limited only to the Asian-Pacific area.It is that the whole world mentions to make Beidou satellite navigation system preferably For service, China will finally emit 35 Beidou navigation satellites, and (+3 inclination geostationary orbits of 5 satellites are defended + 27, star middle circular orbit satellites), using the passive Global Satellite Navigation System combined with active navigation mode.Beidou three generations Two generation navigation system before relatively in signal system (including frequency, signal modulation mode, bit rate, message format etc.) and connect There is very big adjustment in the design of receipts machine.All these designs have to find a kind of most reasonable by constantly verifying Design is to determine final design.Beidou three generations satellite navigation system in the near future can be to provide accurate position for the whole world Positioning service is set, is even more especially qualitative leap to China military navigation field.The development of Beidou three generations's satellite signal simulator, It is most important for the development of receiver, test of the complex environments such as high dynamic for receiver can be just simulated in laboratory, It is especially even more so for the high dynamic user of military aircraft, guided missile and spacecraft one kind.

The frequency of Beidou three generations's satellite signal simulator BIC is adjusted to 1575.42MHz, signal increase BOC modulation, Very big adjustment has been done in bit rate and message format, while having further related to the technology of many high point essences, and technical difficulty is very big.But It is the navigation system that Beidou three generations's satellite navigation system is China's independent research, the terminal of military receiver is researched and developed and navigated System verifying has very big significance.Therefore, satellite signal simulator key technology is broken through, high performance Beidou three generations is developed Satellite signal simulator, it is most important for the development of China's military and civilian.

Utility model content

The purpose of this utility model is to provide for a kind of Beidou three generations satellite-signal simulation system, to realize that Beidou three generations defends The simulation of star signal, to meet the development and testing requirement of Beidou three generations's receiver.

To solve the above problems, the utility model is achieved through the following technical solutions:

A kind of Beidou three generations satellite-signal simulation system, DSP core core, FPGA signal processing mould including sequential connection Block, up-converter module and transmitting antenna/output cable module, in which:

DSP core core is connect with host computer, the data for receiving host computer transmission is carried out classification storage, and according to transmission The data to come over carry out text and write；

FPGA signal processing module adds up to the carrier wave nco value and code nco value that are transmitted by DSP core core, together When generate to interrupt to count and send DSP core core to, for the writing and transmit of text, the calculating and biography of nco value in DSP core core It is defeated；

The baseband signal that carrier modulation block exports is up-converted to radiofrequency signal, and is sent into transmitting day by up-converter module Line；

Transmitting antenna goes out emission of radio frequency signals.

The FPGA signal processing module has data interaction, carrier wave NCO and code nco value between DSP core core Accumulation calculating and the data such as text storage and the functions such as pseudo-code generation, spreading code modulation, carrier modulation, in which:

Pseudo-code generates, and generates pseudo-code, and pseudo-code is sent into band spectrum modulation；

Spreading code modulation is sent into carrier modulation after text and pseudo-code are carried out band spectrum modulation；

Carrier modulation carries out carrier modulation to the signal of feeding, and generates baseband signal；

The beneficial effects of the utility model are:

1) controllability: can taking human as selected or removal true environment in sorts of systems error, can enable or shield Cover the signal of any one system or a navigation satellite.

It 2) can repeatability: repeated test can be carried out under identical test environment conditions, thus eventually to navigation The positioning performance and locating effect at end carry out quantitative analysis.

3) broad applicability: can be with analog simulation any time, the Navigational Movements state in any place can emulate quiet Only, the navigation signal in the environment of low dynamic and high dynamic.

4) availability: the research and development that satellite navigation receives chip are typically all to be exactly prior to the preparation of satellite navigation system It said before navigational satellite system completion, it is necessary to the signal of corresponding navigation satellite transmitting can be obtained.Navigation satellite mould Quasi- device can according to need the navigational satellite system of simulation any kind completely, to keep land exploitation same with deep space satellite When correctly work.

5) save the cost: being tested using navigation satellite simulator, can save during the experiment a large amount of manpowers and Efficiency is continuously improved in equipment cost under the premise of ensuring product reliable quality, saves exploitation and test period.

Detailed description of the invention

Fig. 1 is the structural block diagram of the utility model embodiment Beidou three generations satellite information simulation system；

Fig. 2 is the schematic diagram of the utility model embodiment DSP message processing module；

Fig. 3 is the utility model embodiment FPGA one-channel signal generating principle figure；

Fig. 4 is the modulated process figure of the utility model embodiment BOC navigation signal；

Fig. 5 is the implementation schematic diagram of the utility model embodiment BOC navigation signal.

Specific embodiment

Embodiment:

A kind of Beidou three generations New System satellite signal simulator system, is mainly made of host computer and hardware platform.System As shown in Figure 1, hardware platform includes DSP signal processing module, FPGA signal processing module, D/A conversion module, up-conversion mould Block and antenna.

User can input longitude and latitude, time, the ephemeris file of customized global any position by host computer.It is upper Machine is converted according to the file that user is inputted, and data are transferred to hardware platform later.Host computer also has certain simultaneously Computing function calculates the azimuth and the elevation angle of satellite according to information such as ephemeris file, longitude and latitude and the times received.

DSP signal processing module is connect with FPGA signal processing module by EMIF, is received host computer and is passed through FPGA signal Information that processing module transmits, including ephemeris parameter, simulation moment, user location etc..DSP signal processing module according to These parameters carry out text and write the calculating with satellite position.Later, satellite position calculation obtained by calculation goes out pseudorange, code Phase, carrier phase, code frequency control word and carrier frequency control word.

FPGA signal processing module be connected with host computer complete data transmit in real time with reception.Host computer makes user by oneself Emulation moment of justice, user location, the information such as ephemeris parameter are by issuing DSP, FPGA signal processing module and DSP after processing Signal processing module is connected by EMIF, DSP is transmitted through the active user coordinate come, the information such as time are transmitted to host computer and show. By interrupting between FPGA and DSP, the real-time, interactive of information is completed.FPGA signal processing module believes the calculated text of DSP The information of breath, carrier frequency control word and code frequency control word is stored into register.By the pseudo-code signal of generation and navigation electricity Literary mould two adds, and after BPSK modulation, then using BOC modulation, generates digital medium-frequency signal later, finally will be in the number of multi-satellite D/A conversion module is given in output after frequency signal carries out numbers pile up.

The modulation power spectrum of above-mentioned BOC navigation signal, which has, splits spectral property, and main lobe has split into the two sides of centre frequency. In this way, their power spectrum degree of overlapping is very low, effectively reduces signal when BOC signal and traditional bpsk signal band sharing Between mutual interference, improve the compatibility of navigation system.Furthermore under the premise of identical bit rate, BOC navigation signal correlation letter Several main peaks is more precipitous than traditional bpsk signal, and be more good positioning accuracy can be provided for navigation system and inhibits multipath Energy.

The digital medium-frequency signal that FPGA signal processing module generates is converted into analog if signal by D/A conversion module, it Up-converter module is transferred to after amplification afterwards；

The analog if signal that D/A conversion module transmits is mixed by up-converter module with local oscillation signal, is transformed into north The frequency of the radiofrequency signal of bucket three generations, exports eventually by transmitting antenna or output cable.

A kind of Beidou three generations New System satellite signal simulator design method that above system is realized, including walk as follows It is rapid:

Step 1, Beidou three generations satellite signal simulator, is mainly made of host computer and hardware platform.Hardware platform includes DSP core core, FPGA baseband board, up-converter module and transmitting antenna or output cable；

Step 2, longitude and latitude, time, motion profile, the ephemeris etc. of global any position can be arranged in host computer by user's subjectivity Information.These information are carried out integration processing by host computer, generate the document scene of certain format.Pass through serial ports tool later, it will These data are sent to DSP core core and are handled；

Step 3, the data for receiving host computer transmission are carried out classification storage by DSP core core.According to the star transmitted It counts one by one and is write according to progress text, calculate pseudorange, code phase, carrier phase, code according to information such as user location, time, ephemeris The information such as frequency control word and carrier frequency control word；

Step 4, every 8ms, which is interrupted, arrives, and the information such as carrier wave nco value and code nco value are transferred to FPGA by EMIF by DSP, FPGA carries out accumulation process to the nco value transmitted, is handled by accumulator and generates carrier wave and pseudo-code；

Step 5, the text transmitted, carrier wave, pseudo-code are modulated by modulator, first carry out pseudo-code and navigation message BPSK modulation, carries out BOC modulation later；

Fig. 4 shows that the modulated process of BOC navigation signal, navigation message are multiplied with PRN code (i.e. pseudo noise code) first Spread spectrum is completed in method operation, is then multiplied again with a square wave subcarrier with higher bit rate, is obtained base band BOC signal.Most Afterwards, the radiofrequency signal for being used to emit will be obtained in base band BOC signal modulation to carrier wave.The frequency spectrum of base band BOC signal splits into two A part, is equivalent to the superposition after two bpsk signal frequency spectrums or so are moved, and the value that left and right is moved is equal to the frequency of subcarrier Value.The mathematic(al) representation of base band BOC signal is as follows:

Wherein, P is signal power, c_iFor PRN code (pseudo noise code), p_aIt (t) is unit rectangular pulse, d_iIt (t) is navigation Text, T_cFor the chip period of PRN code, s_i(t) it is square wave subcarrier, and its mathematical model is as follows:

Wherein, N is the number of pulses of subcarrier, h_lFor the symbol (its value is -1,1) of the 1st pulse, T_sFor subcarrier Pulse width, and T_s=T_c/N。

BOC navigation signal is generally denoted as BOC (M, N), and wherein M indicates that the ratio of subcarrier and reference frequency, N indicate pseudo- The ratio of random bit rate and reference frequency, that is, meet f_sc=M*f_refAnd f_prn=N*f_ref.Wherein, f_refIndicate reference frequency, Usual value 1.023MHz.Furthermore, it is possible to distinguish sinusoidal and cosine BOC modulation system by increasing lower target mode, i.e., just String and cosine BOC modulation can be expressed as BOC respectively_S(M, N) and BOC_C(M,N)。

In Beidou three generations's satellite signal simulator, the modulated signal of BOC and carrier wave are modulated generation intermediate-freuqncy signal； The complex envelope of signal can be expressed as

s_B1C(t)=s_{B1C_data}(t)+js_{B1C_pilot}(t)

Wherein, s_{B1C_data}It (t) is data component, by navigation message data D_{B1C_data}(t) and ranging code C_{B1C_data}(t) it passes through Subcarrier SC_{B1C_data}(t) modulation generates, using sinusoidal BOC (1,1) modulation system； s_{B1C_pilot}It (t) is weight of pilot frequency, by surveying Away from code C_{B1C_pilot}(t) through subcarrier SC_{B1C_pilot}(t) modulation generates, using QMBOC (6, Isosorbide-5-Nitrae/33) modulation system；Data point Amount and the power ratio of weight of pilot frequency are 1:3.The expression formula of two components is as follows:

Step 6, the intermediate-freuqncy signal of generation generates radiofrequency signal by mixing, is launched by antenna.

The utility model relates to key technology are as follows:

1, Beidou three generations ranging code structure

B1C signal ranging code is made of using layering code structure primary key and subcode phase exclusive or.The chip width of subcode and master The period of code is identical, the initial time close alignment of subcode chip initial time and first chip of primary key.B1C signal primary key by Weil code is generated by truncation, and the Weil code sequence that a code length is N may be defined as

W(k；W)=L ((k+w) modN), k=0,1,2....N-1

In formula, L (k) is the legendre sequence that code length is N；W indicates the phase difference between two legendre sequences.Code The legendre sequence L (k) of a length of N can define according to the following formula generation:

And there are integer x, so that k=x²modN

Wherein, mod indicates Modulo division.

By carrying out circulation interception to the weil code sequence that above-mentioned code length is N, it is N that code length, which can be obtained,₀Ranging code, that is, cut Disconnected sequence are as follows:

c(n；w；P)=W ((n+p-1) modN；W), n=0,1,2...N₀-1

In formula, p is intercept point, and expression is intercepted since the pth position of weil code, and value range is 1~N.

The bit rate of B1C signal primary key is 1.023Mcps, and code length 10230 is passed through by the Weil code that length is 10243 Truncation generates, and w value range is 1~5121.

2, Beidou three generations navigation message structure

Length of the subframe 1 before Error Correction of Coding is second counting (SOH) in 14 bits, including No. PRN and hour.Using BCH After (21,6)+BCH (51,8) coding, length is 72 sign bits.

g_21,6(x)=x⁶+x⁴+x²+x+1

g_51,8(x)=x⁸+x⁷+x⁴+x³+x²+x+1。

Claims (2)

1. a kind of Beidou three generations satellite-signal simulation system, it is characterized in that: including the DSP core core being linked in sequence, FPGA signal Processing module, up-converter module and transmitting antenna/output cable module, in which:

DSP core core is connect with host computer, and the data that will receive host computer transmission carry out classification storage, and according to transmitting Data carry out text write；

FPGA signal processing module adds up to the carrier wave nco value and code nco value that are transmitted by DSP core core, produces simultaneously It is raw interrupt to count sends DSP core core to, for the writing and transmit of text, the calculating and transmission of nco value in DSP core core；

The baseband signal that carrier modulation block exports is up-converted to radiofrequency signal, and is sent into transmitting antenna by up-converter module；

Transmitting antenna goes out emission of radio frequency signals.

2. Beidou three generations satellite-signal simulation system according to claim 1, it is characterized in that: the FPGA signal processing mould Block has depositing for the data such as the data interaction between DSP core core, the accumulation calculating of carrier wave NCO and code nco value and text Storage and pseudo-code generate, spreading code is modulated, carrier modulation function, in which:

Pseudo-code generates, and generates pseudo-code, and pseudo-code is sent into band spectrum modulation；

Spreading code modulation is sent into carrier modulation after text and pseudo-code are carried out band spectrum modulation；

Carrier modulation carries out carrier modulation to the signal of feeding, and generates baseband signal.