Satellite navigation signal system design method based on hybrid modulation of direct sequence spread spectrum and frequency hopping

Abstract

The present invention relates to a satellite navigation signal system design method based on hybrid modulation of direct sequence spread spectrum and frequency hopping. The method comprises: spreading code sequences of multiple signal components being modulated and being then hybrid-multiplexed with signal components corresponding to a same frequency point, and forming a baseband code sequence on the basis of power allocation ratios of the signal components; on the basis of environment conditions, performing signal separation on the signal components corresponding to the baseband code sequence, in order to obtain separated radio frequency signals, and performing recombination and modulation on the signals; if the separated radio frequency signals are authorized signals, controlling a frequency hopping pattern by means of a frequency hopping code sequence, and performing hybrid frequency synthesis modulation on the basis of a center frequency point of the frequency hopping pattern and the frequency of the authorized signals; if the separated radio frequency signals are unauthorized signals, performing direct combining and radio frequency modulation on the unauthorized signals on the basis of a signal frequency point, in order to obtain recombined signal components; and performing signal power amplification on the basis of a center frequency point difference of the recombined signal components, in order to obtain direct sequence spread spectrum navigation signals. The method can greatly improve the anti-jamming capability of navigation signals.

Description

A satellite navigation signal system design method of direct spread frequency hopping hybrid modulation TECHNICAL FIELD

[0001] The present application relates to the field of global satellite navigation and positioning technology, in particular to a satellite navigation signal system design method of direct spread frequency hopping hybrid modulation. BACKGROUND

[0002] The anti-interference ability of a satellite navigation system is determined by the navigation system signal system and the anti-interference algorithm of the navigation terminal. At the terminal level, time domain anti-interference, frequency domain anti-interference, space domain anti-interference and various combined anti-interference technologies have been developed and perfected. At the system level, once the navigation signal system is determined, it is generally not changed easily, and the spread spectrum gain of the navigation signal directly determines the anti-interference ability of the signal. Moreover, the system anti-interference ability is greatly limited by the existing navigation signal system because the navigation signal frequency is public. The traditional satellite navigation signal generally uses direct sequence spread spectrum modulation to obtain higher signal gain, and frequency hopping technology is mainly applied in the field of mobile communication to improve the anti-interference ability of the communication system.

[0003] Through existing technical retrieval, the design of the traditional satellite navigation signal system is mainly based on the design of the GPS system signal system, combined with the signal system design constraints and service characteristics of satellite navigation systems in various countries, to design navigation signal systems of different frequencies. Chinese invention patent application (application publication number: CN109709578A), named a multi-frequency multi-value signal constant envelope multiplexing method, mainly determines the corresponding phase constraint expression according to the difference between the carrier frequency of the composite signal and each frequency in the N frequencies, combined with the phase lookup table, to realize multi-frequency constant envelope multiplexing of N independent signal components. Chinese invention patent application (application publication number: CN114279444A), named a GNSS-like indoor navigation signal system design system, mainly designs a larger signal bandwidth on the basis of the traditional satellite navigation signal system, simultaneously uses short period pulse design, and defines a protocol suitable for indoor environment, to realize a GNSS indoor navigation signal.

[0004] In the field of communication and navigation, there are some researches on direct spread + frequency hopping hybrid modulation signals. Chinese invention patent application (application publication number: CN110730018A), named anti-interference method of direct spread frequency hopping hybrid spread spectrum system, mainly aims to process the signal of the current frequency hopping frequency point, and detect the signal state of the next frequency hopping frequency point in advance by using the known frequency hopping pattern information, so as to realize the detection of twice frequency hopping period of the same frequency hopping frequency point, suppress the multi-tone interference signal residing in the frequency hopping frequency point, and improve the communication performance of the hybrid spread spectrum system in the multi-tone interference environment. Chinese invention patent application (application publication number: CN101571587A), named radio navigation system of spread frequency hopping system, mainly uses N transmitting stations distributed in different positions and navigation receivers (N≥3) to perform direct spread modulation and frequency hopping modulation on the navigation text in the spread frequency hopping modulation module, and then transmits the signal to the outside through the antenna after high-pass filter and power amplifier. Chinese invention patent application (application publication number: CN101592725A), named signal generator and signal generation method of spread frequency hopping system radio navigation system, mainly comprises a set of spread spectrum system navigation signal generation system composed of encoder, direct spread modulator, direct spread pseudo code generator, clock, frequency hopping modulator, frequency synthesizer and frequency hopping sequence generator, which can be applied to spread frequency hopping system radio navigation system.

[0005] In summary, the current satellite navigation signal system design method mainly follows the traditional GPS signal system design method, and various multipath constant envelope multiplexing methods are designed on the basis of BPSK spread spectrum modulation, or new text, subcarrier, secondary code sequence modulation methods are added, and the system anti-interference ability is still limited by the spread spectrum modulation of single frequency point signal. Another way is to directly quote the mature signal system design method in the field of communication, including OFDM modulation and frequency hopping modulation. Due to the constraints of various constraints of traditional navigation signal system design, it is not popularized and applied at present. It can be seen that the existing technology has some shortcomings in positioning and anti-interference ability under large bandwidth condition. SUMMARY

[0006] Therefore, it is necessary to provide a satellite navigation signal system design method of direct spread frequency hopping hybrid modulation capable of improving the anti-interference ability of satellite navigation signal.

[0007] A satellite navigation signal system design method of direct spread frequency hopping hybrid modulation, the navigation signal comprises a plurality of signal components, and the method comprises: obtaining a plurality of signal component design requirements. The plurality of signal component design requirements comprise: baseband code sequence generation design, signal separation and recombination design, frequency hopping modulation design and direct spread signal generation design.

[0008] The baseband code sequence of the multiple signal components is designed as a spread spectrum code sequence of the multiple signal components, which is modulated and mixed with the signal components corresponding to the same frequency point to form the baseband code sequence according to the power ratio of each signal component.

[0009] The signal components corresponding to the baseband code sequence are separated according to the navigation signal receiving environment conditions to obtain multiple separated radio frequency signals.

[0010] The multiple separated radio frequency signals are modulated by signal recombination. If the separated radio frequency signal corresponding to the current communication channel is an authorized signal, the frequency hopping pattern is controlled by the frequency hopping code sequence, and the mixed frequency synthesis modulation is performed according to the center frequency point of the frequency hopping pattern and the frequency of the authorized signal to obtain multiple modulated recombined signal components. If the separated radio frequency signal corresponding to the current communication channel is an unauthorized signal, the direct mixing radio frequency modulation is performed according to the preset signal frequency and the frequency of the unauthorized signal to obtain multiple modulated recombined signal components.

[0011] The signal power of each modulated recombined signal component is amplified according to the center frequency point difference of the multiple modulated recombined signal components to obtain multiple direct spread navigation signals for transmission.

[0012] A satellite navigation signal system design system for direct spread frequency hopping hybrid modulation, the system comprising: a spread spectrum primary code generation unit for generating a spread spectrum code of a navigation signal component, and outputting the spread spectrum code to a secondary code generation unit.

[0013] The secondary code generation unit is configured to modulate the spread spectrum code to generate a secondary code with a slow period, and output the secondary code to a subcarrier modulation unit.

[0014] The subcarrier modulation unit is configured to modulate the secondary code using a BOC modulation method to generate a ranging code sequence, and output the ranging code sequence to a navigation information modulation unit.

[0015] The navigation information modulation unit is configured to modulate the ranging code sequence with navigation message information to obtain a modulated spread spectrum code sequence, and output the modulated spread spectrum code sequence to a frequency hopping modulation unit and a frequency synthesizer.

[0016] The frequency hopping modulation unit is configured to generate a frequency hopping sequence for controlling a frequency hopping pattern by a frequency hopping sequence generator, and output the frequency hopping sequence to the frequency synthesizer.

[0017] The frequency synthesizer is configured to perform radio frequency synthesis on the frequency hopping sequence and the modulated spread spectrum code sequence to obtain a radio frequency modulated signal, and output the radio frequency modulated signal to a power amplifier as an amplified navigation signal.

[0018] In one of the embodiments, the spread spectrum primary code generating unit, the secondary code generating unit, the subcarrier modulating unit and the navigation information modulating unit adopt binary modulation, and the number of execution units is adjusted according to the design requirements of the multiple signal components in different satellite navigation signal modulation generation processes.

[0019] In one of the embodiments, the power amplifier is used for power amplifying the radio frequency modulated signal to obtain the direct spread navigation signal, and the direct spread navigation signal is output to the satellite transmitting antenna.

[0020] A computer device comprises a memory and a processor, the memory stores a computer program, and the processor implements the following steps when executing the computer program: the navigation signal comprises multiple signal components.

[0021] The design requirements of the multiple signal components are obtained. The design requirements of the multiple signal components include baseband code sequence generation design, signal separation and recombination design, frequency hopping modulation design and direct spread signal generation design.

[0022] The baseband code sequence generation design of the multiple signal components is designed as that the spread spectrum code sequence of the multiple signal components is modulated and mixed and multiplexed with the signal components corresponding to the same frequency point, and the baseband code sequence is composed according to the power ratio of each signal component.

[0023] The signal components corresponding to the baseband code sequence are separated according to the navigation signal receiving environment conditions to obtain multiple separated radio frequency signals.

[0024] The multiple separated radio frequency signals are modulated by signal recombination. If the separated radio frequency signal corresponding to the current communication channel is an authorized signal, the frequency hopping pattern is controlled by the frequency hopping code sequence, the mixed frequency synthesis modulation is performed according to the center frequency point of the frequency hopping pattern and the frequency of the authorized signal to obtain multiple modulated recombination signal components. If the separated radio frequency signal corresponding to the current communication channel is an unauthorized signal, the direct mixing radio frequency modulation is performed according to the preset signal frequency and the frequency of the unauthorized signal to obtain multiple modulated recombination signal components.

[0025] The signal power of each modulated recombination signal component is amplified according to the center frequency point difference of the multiple modulated recombination signal components to obtain multiple direct spread navigation signals for transmission.

[0026] The satellite navigation signal system design method of the direct spread frequency hopping hybrid modulation, first, through the baseband code sequence generation design, the spread spectrum code sequence of the multiple signal components is mixed and multiplexed after modulation with the signal components of the same frequency point, the baseband code sequence is generated according to the power ratio of each signal component, which improves the flexibility and adaptability of signal generation, and meets different navigation requirements. Secondly, according to the receiving environment conditions, the signal components corresponding to the baseband code sequence are separated to obtain multiple separated radio frequency signals. The separated signals are recombined and modulated, and the authorized signals and the unauthorized signals are processed respectively: for the authorized signals, the frequency hopping pattern is controlled by the frequency hopping code sequence, and the frequency synthesis modulation is performed; for the unauthorized signals, the radio frequency modulation is directly performed according to the preset signal frequency. Such signal separation and recombination ensures accurate demodulation and recombination of the signal, and improves the reliability and anti-interference ability of the navigation signal. In addition, through the frequency hopping modulation technology and the radio frequency modulation technology, the authorized signals and the unauthorized signals are effectively distinguished and processed, which enhances the anti-interference ability of the system, not only improves the adaptability of the navigation system in complex environment, but also enhances the security and stability of the system. Finally, the recombined signal components after modulation are amplified according to the center frequency difference, and the multiple direct spread navigation signals for transmission are obtained, which improves the transmission strength and coverage of the signal, ensures the stable transmission and wide coverage of the navigation signal, and improves the effectiveness and reliability of the navigation system. In summary, through the whole process design of the generation, separation, recombination, modulation and transmission of the multiple signal components, the multiple satellite navigation signals are separated and recombined under the satellite communication emergency conditions such as strong interference, the frequency of the signal carrier needing emergency frequency hopping is controlled by the frequency hopping code, which significantly improves the flexibility, adaptability and anti-interference ability of the navigation signal, and ensures the integrity, accuracy and stability of the signal. On the basis of the traditional direct spread navigation system, the frequency hopping signal system is introduced, which fully improves the anti-interference ability of the satellite navigation signal, while maintaining the high positioning precision of the direct spread signal under the condition of large bandwidth. BRIEF DESCRIPTION OF DRAWINGS

[0027] Fig. 1 is a flowchart of a satellite navigation signal system design method of a direct spread frequency hopping hybrid modulation in an embodiment; DETAILED DESCRIPTION

[0028] In order to make the purpose, technical scheme and advantages of the present application clearer, the present application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and do not limit the present application.

[0029] In one embodiment, as shown in Figure 1, a satellite navigation signal system design method of direct spread frequency hopping hybrid modulation is provided, which is applied to a satellite navigation signal system design system of direct spread frequency hopping hybrid modulation, wherein the system comprises: a spread spectrum primary code generation unit for generating a spread spectrum code of a navigation signal component, and outputting the spread spectrum code to a secondary code generation unit; the secondary code generation unit is used for modulating the spread spectrum code to generate a secondary code of a slow period, and outputting the secondary code to a subcarrier modulation unit; the subcarrier modulation unit is used for modulating the secondary code by using a BOC modulation mode to generate a ranging code sequence, and outputting the ranging code sequence to a navigation information modulation unit; the navigation information modulation unit is used for modulating the ranging code sequence by navigation message information to obtain a modulated spread spectrum code sequence, and outputting the modulated spread spectrum code sequence to a frequency hopping modulation unit and a frequency synthesizer; the frequency hopping modulation unit is used for generating a frequency hopping sequence for controlling a frequency hopping pattern by a frequency hopping sequence generator, and outputting the frequency hopping sequence to the frequency synthesizer; the frequency synthesizer is used for performing radio frequency synthesis on the frequency hopping sequence and the modulated spread spectrum code sequence to obtain a radio frequency modulation signal, and outputting the radio frequency modulation signal to a power amplifier as an amplified navigation signal; and the power amplifier is used for power amplifying the radio frequency modulation signal to obtain a direct spread navigation signal, and outputting the direct spread navigation signal to a satellite transmitting antenna. In addition, the spread spectrum primary code generation unit, the secondary code generation unit, the subcarrier modulation unit, and the navigation information modulation unit adopt binary modulation, and the number of execution units is adjusted according to the design requirements of the multiple signal components in different satellite navigation signal modulation generation processes.

[0030] Specifically comprising the following steps: step 102, obtaining multiple signal component design requirements.

[0031] The multiple signal component design requirements comprise: baseband code sequence generation design, signal separation and recombination design, frequency hopping modulation design, and direct spread signal generation design. The design requirements specifically comprise the following elements: (1) spread spectrum system design. At present, the satellite navigation signal system generally adopts BPSK modulation and BOC modulation, both of which are based on direct sequence spread spectrum technology. The BOC modulation generally adds a binary subcarrier to the BPSK signal for secondary spread spectrum on the basis of the original BPSK modulation. For simplicity, the spread spectrum system in the present application adopts BPSK modulation, and a spread spectrum code signal with a code rate of 2.046Mchips / s is adopted.

[0032] (2) Frequency Hopping Bandwidth Design. The selection of frequency bands is crucial for satellite navigation, as it must avoid interference with existing services while ensuring the service performance of navigation signals. According to the ITU's frequency allocation rules for radio navigation satellite services, currently available navigation signal frequency resources include: L-band (1164-1215MHz, 1215-1300MHz, 1559-1610MHz), S-band (2483.5-2500MHz), and C-band (5010-5030MHz). With the application and development of low-Earth orbit (LEO) satellite navigation systems, some high-frequency resources such as the Ku (10.7-18.1GHz) and Ka (26.5-40GHz) bands may also be used for satellite navigation in the future, further expanding the frequency hopping range of navigation signals. For the sake of simplicity, this invention only selects the L band for analysis, including two bands: 1231.692±67.518MHz and 1583.604±24.552MHz, with bandwidths of 135.036MHz and 49.104MHz, respectively.

[0033] (3) Frequency hopping frequency number and frequency hopping gap design. The frequency hopping gap refers to the frequency difference between two adjacent frequency hopping center points. In order to avoid spectral aliasing between the frequency hopping signals, the frequency hopping gap is set to 4.092MHz, and the corresponding frequency hopping frequency number is 45.

[0034] (4) Frequency hopping rate design. Frequency hopping rate refers to the number of frequency hops per second. Generally, the higher the frequency hopping rate, the more difficult the signal is to track. A typical medium-speed frequency hopping rate is 100-1000 hops / s.

[0035] (5) Frequency hopping pattern design. The anti-interference performance of a frequency hopping system is greatly affected by the frequency hopping pattern, and one of the key factors is to design a good frequency hopping code. To cover the above 45 frequency hopping numbers, this invention designs an n=6 shift register to generate m sequences.

[0036] Step 104: The baseband code sequence of the multi-channel signal components is generated by modulating the spread spectrum code sequence of the multi-channel signal components and mixing and multiplexing it with the signal components corresponding to the same frequency point, and forming the baseband code sequence according to the power ratio of each signal component.

[0037] Step 106: Separate the signal components corresponding to the baseband code sequence according to the navigation signal receiving environment conditions to obtain multi-channel separated radio frequency signals.

[0038] Step 108, the multi-channel separated radio frequency signals are modulated by signal recombination, if the separated radio frequency signal corresponding to the current communication channel is an authorized signal, then the frequency hopping pattern is controlled by the frequency hopping code sequence, the center frequency of the frequency hopping pattern is mixed with the frequency of the authorized signal for frequency synthesis modulation, and the multi-channel modulated recombined signal components are obtained. If the separated radio frequency signal corresponding to the current communication channel is an unauthorized signal, then the preset signal frequency is directly mixed with the frequency of the unauthorized signal for radio frequency modulation, and the multi-channel modulated recombined signal components are obtained.

[0039] Specifically, the pseudo-range residual vector is calculated under the preset alarm probability, the multi-channel separated radio frequency signals are modulated by signal recombination, if the separated radio frequency signal corresponding to the current communication channel is an authorized signal, then the frequency hopping pattern is controlled by the frequency hopping code sequence, the center frequency of the frequency hopping pattern is mixed with the frequency of the authorized signal for frequency synthesis modulation, and the multi-channel modulated recombined signal components are obtained. If the separated radio frequency signal corresponding to the current communication channel is an unauthorized signal, then the preset signal frequency is directly mixed with the frequency of the unauthorized signal for radio frequency modulation, and the multi-channel modulated recombined signal components are obtained. The chi-square non-centralization parameter under the condition of the multi-channel modulated recombined signal components is obtained, and the characteristic slope of the visible satellite group is obtained according to the chi-square non-centralization parameter.

[0040] Step 110, the multi-channel modulated recombined signal components are amplified by signal power according to the center frequency difference of the multi-channel modulated recombined signal components, and the multi-channel direct spread navigation signals used for transmission are obtained.

[0041] In the above method for designing a satellite navigation signal system with direct spread frequency hopping hybrid modulation, first, through baseband code sequence generation design, the spread spectrum code sequences of multiple signal components are modulated and mixed with the signal components at the same frequency point, and the baseband code sequence is generated according to the power ratio of each signal component, which improves the flexibility and adaptability of signal generation and meets different navigation requirements. Second, according to the receiving environment conditions, the signal components corresponding to the baseband code sequence are separated to obtain multiple separated radio frequency signals. The separated signals are recombined and modulated, and the authorized signals and non-authorized signals are processed respectively: for the authorized signals, the frequency hopping pattern is controlled by the frequency hopping code sequence, and frequency synthesis modulation is performed; for the non-authorized signals, direct combination radio frequency modulation is performed according to the preset signal frequency. Such signal separation and recombination ensures accurate demodulation and recombination of the signals, and improves the reliability and anti-interference ability of the navigation signals. In addition, through the frequency hopping modulation technology and the combination radio frequency modulation technology, the authorized signals and the non-authorized signals are effectively distinguished and processed, which enhances the anti-interference ability of the system, improves the adaptability of the navigation system in complex environments, and enhances the security and stability of the system. Finally, the recombined signal components after modulation are amplified in power according to the differences in center frequency to obtain multiple direct spread navigation signals for transmission, which improves the transmission strength and coverage of the signals, ensures stable transmission and wide coverage of the navigation signals, and thus improves the effectiveness and reliability of the navigation system. In summary, through the whole process design of multiple signal component generation, separation, recombination, modulation and transmission, the multiple satellite navigation signals are separated and recombined under strong interference and other satellite communication emergency conditions, the signal carrier frequency that needs to be jumped in emergency is controlled by the frequency hopping code, which significantly improves the flexibility, adaptability and anti-interference ability of the navigation signals, and ensures the integrity, accuracy and stability of the signals. On the basis of the traditional direct spread navigation system, the frequency hopping signal system is introduced to fully improve the anti-interference ability of the satellite navigation signal, while maintaining the high positioning accuracy of the direct spread signal under large bandwidth conditions.

[0042] In one embodiment, there are military and civilian multiple signal components in the multiple signal components, and each military and civilian multiple signal component is modulated by the same or different spread spectrum modulation method according to the baseband attribute.

[0043] It is worth noting that since the original navigation spread spectrum signal system is retained, the ranging performance of the navigation signal itself can be maintained without loss of navigation positioning accuracy. At the same time, under the condition of multiple signal multiplexing, by maintaining the modulation method of the civilian navigation signal, the normal service of the civilian signal in special scenarios can be maintained, and other risks can be avoided.

[0044] In one of the embodiments, the spread spectrum code sequence of the multi-path signal component is modulated and mixed with the signal component corresponding to the same frequency point by using constant envelope or non-constant envelope modulation mode, and the baseband code sequence is formed according to the power ratio of each signal component.

[0045] It is worth mentioning that the spread spectrum primary code generation unit generates a spread spectrum code for navigation positioning and outputs to the secondary code generation unit. Common satellite navigation spread spectrum primary code rates are 1.023Mcps, 2.046Mcps, 5.115Mcps, 10.23Mcps, etc. The secondary code generation unit generates a secondary code with a slower period, which is modulated on the spread spectrum primary code, can improve the cross-correlation characteristics between satellite signals and narrowband anti-interference ability, and improve the bit synchronization ability. The spread spectrum code sequence modulated with the secondary code is output to the subcarrier modulation unit. Common satellite navigation secondary code rates are 1kcps, 2kcps, etc. The subcarrier modulation unit usually uses BOC modulation mode, including BOCc, BOCs, CBOC and other types. The spread spectrum code sequence after subcarrier modulation has good correlation and can realize signal reception and ranging. The code sequence is output to the navigation information modulation unit.

[0046] In addition, the navigation information modulation unit mainly modulates navigation text information on the basis of the spread spectrum code sequence to facilitate the receiver to calculate the satellite position after demodulating the signal. Common satellite navigation text rates are 50bps, 100bps, 500bps, etc. After binary modulation by the four units, the generated spread spectrum code sequence is output to the input of the frequency hopping modulation unit. The frequency hopping sequence generator is a sub-module in the frequency hopping modulation unit, which is used to generate a frequency hopping sequence to control the frequency hopping pattern. It is usually controlled by m sequence, Gold sequence, etc. The output end is connected to the input end of the frequency synthesizer. The frequency synthesizer mainly synthesizes the corresponding radio frequency. The output end is connected to the input of the frequency hopping modulation unit. The output of the frequency hopping modulation unit is connected to the input of the power amplifier to realize power amplification of the frequency-hopped signal and the non-frequency-hopped signal. The output of the power amplifier is connected to the input of the transmitting antenna to complete the generation and transmission of the modulated signal.

[0047] In one of the embodiments, the frequency hopping code sequence is set according to the number of frequency hopping frequencies and the frequency hopping bandwidth. The code type of the frequency hopping code sequence includes m sequence, M code, Gold code and RS sequence.

[0048] In one of the embodiments, the recombined signal components include: part of the frequency-hopped modulated licensed signal and part of the non-frequency-hopped modulated unlicensed signal. If the carrier frequency difference between the frequency-hopped modulated licensed signal and the non-frequency-hopped modulated unlicensed signal is less than the power amplifier bandwidth limit of the current communication channel, the frequency-hopped modulated licensed signal and the non-frequency-hopped modulated unlicensed signal use the same power amplifier for signal power amplification to obtain the multiple direct spread navigation signals for transmission. If the carrier frequency difference between the frequency-hopped modulated licensed signal and the non-frequency-hopped modulated unlicensed signal is greater than or much greater than the power amplifier bandwidth limit of the current communication channel, the frequency-hopped modulated licensed signal and the non-frequency-hopped modulated unlicensed signal use independent power amplifiers for signal power amplification to obtain the multiple direct spread navigation signals for transmission.

[0049] It is worth mentioning that, due to the fusion of the frequency-hopped signal system, the overall signal bandwidth is expanded, and the frequency-hopping pattern can be controlled through the frequency-hopping code sequence, so that the center frequency point after frequency hopping becomes more unknown to the non-cooperative party, thereby greatly improving the anti-interference ability of the signal itself or the interference cost of the interference party. In addition, the method of designing the navigation signal system and the signal generation structure have no special requirements, so they are highly adaptable and convenient for transplantation into existing designs.

[0050] In one of the embodiments, the multiple direct spread navigation signals can be transmitted by the same antenna or transmitted by different antennas to the target receiver.

[0051] In one of the embodiments, as shown in FIG. 2, in the satellite navigation signal frequency spread spectrum signal generation process, the following steps are included: S1: generating the ranging code of each satellite navigation signal component. The design of the ranging code mainly considers its autocorrelation and cross-correlation characteristics. The traditional GPS L1 C / A code uses a Gold code with a code length of 1023 for the purpose of fast acquisition, and its essence is a composite code of two m sequences. The modern GPS L1 C signal uses a Weil code with a code length of 10230, and the Galileo E1 and E6 signals use a Random code. The present application supports the above-mentioned various types of primary codes of the ranging code, and as one of the embodiments, the Gold code is selected for illustration.

[0052] S2: generating the secondary code of each satellite navigation signal component. The secondary code is usually shorter in length to improve the correlation characteristics of the code while not reducing the acquisition performance. The GPS L1 C signal uses an NH code as its secondary code, and the Galileo E5 and E6 signals use a CS code. The present application supports the above-mentioned various types of secondary codes, and as one of the embodiments, the NH20 code is selected for illustration.

[0053] S4: Generate sub-carrier of each satellite navigation signal component. Typical satellite navigation sub-carrier modulation signal includes BOCc and BOCs signal, sub-carrier rate is the same as the spread spectrum code rate, usually an integer multiple of 1.023MHz. As an embodiment of the present application, the present application selects BOC(1,1) signal for illustration.

[0054] S5: Generate navigation message information of each satellite navigation signal component. Conventional navigation signal navigation message rate is usually 50bps, 100bps, 500bps, modulated on the navigation signal ranging code. Modern GNSS signal also introduces pilot channel, navigation data is not modulated on the ranging code, which can improve the tracking ability under weak signal condition. The embodiment of the present application selects the same navigation message of conventional GPS L1 signal.

[0055] S6: Signal multiplexing modulation. Each branch navigation signal component generated by S1-S5 is multiplexed and modulated in a combined signal component by using constant envelope technology, typical constant envelope multiplexing technology includes AltBOC, Dual-QPSK, TD-AltBOC, ACEBOC, etc., the embodiment of the present application selects Dual-QPSK modulation. GPS III L1 signal also attempts to use non-constant envelope modulation mode, in the future, with the increasing maturity of on-board power amplifier technology, non-constant envelope modulation will also become an important signal multiplexing mode.

[0056] S7: Authorized signal component frequency hopping modulation. In emergency conditions such as interference, for authorized signal component, the corresponding frequency hopping pattern is generated by the frequency synthesizer controlled by the frequency hopping code generator, forming the mapping relationship between the frequency hopping code and the frequency after frequency hopping, so as to complete the carrier modulation of the authorized signal component after frequency hopping. For non-authorized signal component, the fixed signal frequency specified in satellite navigation ICD is used to realize the carrier modulation of non-authorized signal component.

[0057] S8: Navigation signal power amplification. After the separation processing and partial signal frequency hopping of the plurality of signal components, the frequency hopping signal and the non-hopping signal use different carrier signal frequencies, when the difference between the two signal carrier frequencies is less than the power amplifier bandwidth limit, the two signals can still use the same power amplifier for amplification; if the difference between the two signal carrier frequencies is too large, in order to ensure the efficiency of the power amplifier, two signals are amplified independently by using two power amplifiers.

[0058] S9: Navigation signal transmission. When the difference between the carrier frequencies of two or more signal components is less than the bandwidth limit of the transmitting antenna, the two signals can still use the same antenna for transmission; if the difference between the two signal carrier frequencies is too large, different antennas must be used for transmission.

[0059] It should be appreciated that, although the steps in the flowcharts of FIGS. 1-2 are shown in sequential order, such that each step is completed before proceeding to the next step, the steps do not have to be performed in the order shown. Unless explicitly stated, the steps can be performed in any order. Moreover, at least some of the steps in FIGS. 1-2 can include multiple sub-steps or multiple stages, which can be performed at different times, and in which the order is not necessarily consecutive, but can be interleaved or alternating with at least a portion of another step or another step's sub-steps or stages.

[0060] The technical features of the above embodiments can be combined in any manner. For brevity, not all possible combinations of the technical features in the above embodiments are described, but it should be understood that any combination of the technical features is within the scope of the present disclosure as long as there is no contradiction.

[0061] The above embodiments only express several implementation manners of the present application, and the description is relatively specific and detailed, but it should not be understood as a limitation on the scope of the patent. It should be pointed out that, for those skilled in the art, some modifications and improvements can be made without departing from the concept of the present application, and these are within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the appended claims.

Claims

1. A method for designing a satellite navigation signal system with direct-sequence spread spectrum frequency hopping hybrid modulation, characterized in that, The navigation signal comprises multiple signal components, and the method comprises: obtaining multiple signal component design requirements; the multiple signal component design requirements comprise: baseband code sequence generation design, signal separation and recombination design, frequency hopping modulation design, and direct spread signal generation design; the baseband code sequence generation design of the multiple signal components is designed as the spread spectrum code sequence of the multiple signal components after modulation, and the signal components corresponding to the same frequency point are mixed and multiplexed, and the baseband code sequence is composed according to the power ratio of each signal component; the signal components corresponding to the baseband code sequence are separated according to the navigation signal receiving environment conditions to obtain multiple separated radio frequency signals; the multiple separated radio frequency signals are modulated by signal recombination, if the separated radio frequency signal corresponding to the current communication channel is an authorized signal, the frequency hopping pattern is controlled by the frequency hopping code sequence, the mixed frequency synthesis modulation is performed according to the center frequency of the frequency hopping pattern and the frequency of the authorized signal to obtain multiple modulated recombination signal components; if the separated radio frequency signal corresponding to the current communication channel is an unauthorized signal, the direct mixing radio frequency modulation is performed according to the preset signal frequency and the frequency of the unauthorized signal to obtain multiple modulated recombination signal components; the signal power of each modulated recombination signal component is amplified according to the center frequency difference of the multiple modulated recombination signal components to obtain multiple direct spread navigation signals for transmission.

2. The method of claim 1, wherein, There are military and civilian multiple signal components in the multiple signal components, and each military and civilian multiple signal component adopts the same or different spread spectrum modulation mode for spread spectrum code sequence modulation according to the baseband attribute.

3. The method of claim 1, wherein, After the spread spectrum code sequence of the multiple signal components is modulated, the signal components corresponding to the same frequency point are mixed and multiplexed, and the baseband code sequence is composed according to the power ratio of each signal component. After the spread spectrum code sequence of the multiple signal components is modulated, the signal components corresponding to the same frequency point are mixed and multiplexed by using constant envelope or non-constant envelope modulation mode, and the baseband code sequence is composed according to the power ratio of each signal component.

4. The method according to any one of claims 1 to 3, characterized in that, The frequency hopping code sequence is set according to the frequency hopping frequency and the frequency hopping bandwidth, and the code type of the frequency hopping code sequence comprises: m sequence, M code, Gold code and RS sequence.

5. The method of claim 4, wherein, The recombination signal components comprise: part of the authorized signal modulated by frequency hopping and part of the unauthorized signal without frequency hopping modulation; the signal power of each modulated recombination signal component is amplified according to the center frequency difference of the multiple modulated recombination signal components to obtain multiple direct spread navigation signals for transmission. If the carrier frequency difference between the frequency-hopped modulated authorized signal and the non-frequency-hopped modulated non-authorized signal is less than the power amplifier bandwidth limit of the current communication channel, the frequency-hopped modulated authorized signal and the non-frequency-hopped modulated non-authorized signal use the same power amplifier to perform signal power amplification, and obtain a plurality of direct spread navigation signals for transmission.

6. The method of claim 4, wherein, The plurality of direct spread navigation signals can be transmitted by using the same antenna or different antennas to the target receiver.

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