Adjacent multi-frequency satellite navigation signal multiplexing method, transmitting end, receiving end and system

Abstract

This invention belongs to the field of satellite navigation signal multiplexing technology, and discloses a method, transmitter, receiver, and system for multiplexing adjacent multi-frequency satellite navigation signals. This invention provides a specific implementation method and system for adjacent multi-frequency satellite navigation signal multiplexing technology, enabling the multiplexing of multiple navigation or communication signals at the middle frequency, both sides of the middle frequency, or the upper and lower sidebands of the middle frequency, solving the current problem of no multiplexing of adjacent multi-frequency satellite navigation or communication signals in the BeiDou system. It can be widely applied in satellite navigation systems, various ranging systems, communication systems, broadcasting systems, and control systems.

Description

Technical Field

[0001] This invention belongs to the field of satellite navigation signal multiplexing technology, and more specifically, relates to a method, transmitter, receiver and system for multiplexing adjacent multi-frequency satellite navigation signals. Background Technology

[0002] Due to the limited frequency resources of satellite navigation, in addition to using traditional technologies for frequency reuse, navigation satellites of various satellite navigation systems have developed dedicated offset carrier and complex subcarrier modulation technologies. These technologies reuse frequencies on both sides of a single frequency and on the upper and lower sidebands of the center frequency of adjacent dual frequencies. Offset carrier technologies include the TMBOC (Time Multiplexed Binary Offset Carrier) of the US GPS, the CBOC (Composite Binary Offset Carrier) of the European Galileo, and the QMBOC (Quadrature Multiplexed Binary Offset Carrier) of BeiDou. Complex subcarrier technologies include the AltBOC (Alternative Binary Offset Carrier) of Galileo and the ACE-BOC (Asymmetric Constant Envelope Binary Offset Carrier) of BeiDou.

[0003] Offset carrier implementation technology uses two square wave subcarriers of different frequencies. GPS uses the power ratio method to sporadically assign spreading code points in the time-division multiplexing time slot of the navigation spreading signal, and uses a frequency-doubled square wave subcarrier for modulation. Other code points are implemented by combining and modulating standard frequency square wave subcarriers and then modulating with the main carrier. Galileo synthesizes the navigation spreading signal by weighted addition or subtraction operations of square wave subcarriers of different frequencies, and then modulates it with the main carrier. BeiDou implements navigation spreading signal by modulating the complex subcarriers constructed by standard frequency square wave subcarriers, standard frequency square wave subcarriers and frequency-doubled square wave subcarriers.

[0004] Galileo uses complex subcarrier technology, which consists of imaginary phase orthogonal complex subcarriers formed by summing lead-lag phase square waves, to modulate two adjacent complex navigation signals with equal power. BeiDou uses the same complex subcarrier technology as Galileo, to modulate one navigation signal with unequal power. They can both achieve multiplexing of up to four satellite navigation signals.

[0005] Because BeiDou has not provided a technology to completely solve the problem of combining or synthesizing square wave subcarriers with the same or different frequencies or phases in terms of offset carrier implementation technology, nor has it provided a technology to solve the problem of complex subcarriers, the existing technology can only realize the multiplexing of adjacent dual-frequency navigation signals, but cannot realize the multiplexing of adjacent multi-frequency satellite navigation signals.

[0006] In addition, the short messages transmitted by the BeiDou navigation and communication satellites at the given communication frequency are implemented using narrowband direct spread spectrum and BPSK (Binary Phase Shift Keying) modulation, without frequency reuse. Summary of the Invention

[0007] This invention provides a method, transmitter, receiver, and system for multiplexing adjacent multi-frequency satellite navigation signals, thereby solving the problem that existing technologies cannot achieve multiplexing of adjacent multi-frequency satellite navigation or communication signals of BeiDou.

[0008] In a first aspect, the present invention provides a method for multiplexing adjacent multi-frequency satellite navigation signals, applicable to BeiDou navigation satellites, or applicable to the transmitter of a terminal device such as a satellite navigator or mobile phone, the method comprising the following steps:

[0009] Obtain satellite navigation messages transmitted by N adjacent navigation frequencies of Beidou navigation satellites, or obtain short messages transmitted by terminal devices of different satellite navigation devices or mobile phones operating on a given communication frequency of navigation and communication satellites;

[0010] Obtain the dedicated ranging code of the terminal equipment of Beidou navigation satellites, satellite navigation devices, or mobile phones;

[0011] The satellite navigation messages or short messages transmitted on each navigation or communication frequency are spread using the dedicated ranging code to obtain spread spectrum signals.

[0012] The spread spectrum signal is modulated with different carriers according to transmission requirements to obtain navigation satellite carrier modulated signals or navigation communication carrier modulated signals of each terminal device;

[0013] In this process, different carrier modulation signals of navigation satellites are superimposed to obtain a single-channel satellite carrier modulation signal of the navigation satellite;

[0014] Doppler frequency shifting and noise addition are performed on the single-channel satellite carrier modulation signal of the navigation satellite or the navigation communication modulation signal of each terminal device to obtain the baseband satellite signal of the navigation satellite or each terminal device;

[0015] The baseband satellite signal is modulated by radio frequency and amplified by power and then transmitted by the antenna of the navigation satellite or the antenna of each terminal device. The transmitted signals are transmitted at the middle frequency, both sides of the middle frequency, the upper and lower sidebands of the middle frequency, or both sides of the upper and lower sidebands of the middle frequency, respectively, of the adjacent navigation frequency of the navigation satellite or the communication frequency of the navigation and communication satellite.

[0016] Preferably, the navigation or communication frequency transmits single, dual, or multiple signals; the satellite navigation message is a satellite navigation message with a traditional frame structure D series, a data block structure B-CNAV series, or a hybrid frame structure B-CNAV series; the satellite navigation message or short message is transmitted serially or in parallel overlay.

[0017] Preferably, obtaining the dedicated ranging code of a BeiDou navigation satellite, satellite navigation device, or mobile phone terminal device includes the following sub-steps:

[0018] A pseudo-random code generator, consisting of two linear functions corresponding to given parameters or a nonlinear pseudo-random code generator containing different variables or functions, is started with the initial state value of a register. It uses the combined output of relevant register phase taps as a feedback value, or uses a weighted mixture of nonlinear functions or mutually driving values ​​as a feedback value. By shifting a portion of the register phase combination taps in the pseudo-random code generator, it generates an identification ranging code for a BeiDou navigation satellite, satellite navigation device, or mobile phone terminal device. The given parameters include frequency, number of levels, and code length.

[0019] The general ranging code required for N satellite navigation messages or short messages of terminal devices is generated by outputting the phase combination tap of another part of the register in the pseudo-random code generator.

[0020] The general ranging code required for the N satellite navigation messages of the navigation satellite or the short messages of each terminal device is XORed with the identification ranging code of the Beidou navigation satellite or the terminal device to obtain the special ranging code of the N satellite navigation messages of the Beidou navigation satellite or the short messages of each terminal device.

[0021] Preferably, the specific implementation method for obtaining the single-channel satellite carrier modulation signal of the navigation satellite, or the navigation communication modulation signal of each terminal device, is as follows:

[0022] The N spread spectrum navigation signals of navigation satellites, or a portion of the spread spectrum communication signals of satellite navigation devices or mobile phones, are modulated by BPSK or QPSK at different frequencies or at the same frequency but different phases to obtain phase shift keying modulation signals, which are then used as the first type of modulation signals for navigation satellites or various terminal devices.

[0023] Generate multiple square wave basic subcarriers with different frequencies or the same frequency but different phases;

[0024] Multiple different square wave basic subcarriers are combined or synthesized to form composite real or complex subcarriers. The composite subcarriers are used to modulate another part of N spread spectrum navigation signals or spread spectrum communication signals to obtain corresponding subcarrier modulation signals. Different subcarrier modulation signals are modulated with orthogonal or non-orthogonal main carriers to obtain offset carrier signals, which are used as the second type of modulation signals for navigation satellites or various terminal devices.

[0025] Using the obtained multiple different square wave basic subcarriers, a set of complex subcarriers with orthogonal imaginary parts and complex subcarriers with inverted phases are constructed; the remaining parts of N spread spectrum navigation signals or spread spectrum communication signals or subcarrier modulation signals are multiplied by the complex subcarriers with orthogonal imaginary parts respectively to obtain complex subcarrier modulation signals, which are used as the third type of modulation signals for navigation satellites or various terminal devices;

[0026] The spread spectrum signals transmitted at N navigation frequencies are multiplied together to obtain intermodulation signals; the intermodulation signals are multiplied together with the phase-inverted complex subcarriers to obtain intermodulation modulation signals, which are used as the fourth type of modulation signals for navigation satellites.

[0027] The first, second, third, and fourth type modulation signals of the navigation satellite are superimposed to obtain the single-channel satellite carrier modulation signal of the navigation satellite; while the first, second, and third type modulation signals of each terminal device are their respective navigation communication modulation signals.

[0028] Preferably, the specific implementation of combining or synthesizing multiple different square wave basic subcarriers to form a composite real or complex subcarrier, and constructing a set of complex subcarriers with orthogonal imaginary parts and phase-inverted complex subcarriers using multiple different square wave basic subcarriers, is as follows: synthesizing complex subcarriers by operating on multiple different square wave basic subcarriers.

[0029] The combined modulation rule is to use square wave basic subcarriers of the same or different frequencies or phases to modulate different numerical code points of the navigation spread spectrum signal or to modulate the spread spectrum codes of each segment of time division multiplexing, or to use square wave basic subcarriers of the same or different frequencies or phases to modulate according to different spread spectrum code distribution densities, or to use square wave basic subcarriers of different harmonics to modulate given spread spectrum code points in each segment of time division multiplexing, and to use square wave basic subcarriers of standard frequency to modulate the remaining spread spectrum code points.

[0030] The operation involves combining square wave basic subcarriers with the same or different frequencies, phases, or functions in the time or frequency domains through weighted addition, subtraction, multiplication, division, exponentiation, square root, XOR, or weighted mixed operations to synthesize composite real or complex subcarriers or complex subcarriers; the basic subcarriers used are at least one periodic or aperiodic binary, binary, binarized, multi-valued, multi-valued, or combination or mixed operation wave of the same or different types or frequencies or phases; the operations or basic subcarriers used can be reused in the synthesis process.

[0031] Preferably, during the process of obtaining the phase shift keying modulation signal, the offset carrier signal, and the complex subcarrier modulation signal, the spread spectrum navigation or communication signals or carrier signals are superimposed, or the spread spectrum navigation or communication signals are superimposed in the carrier phase.

[0032] Secondly, the present invention provides a method for multiplexing adjacent multi-frequency satellite navigation signals, applicable to BeiDou navigation satellites, or applicable to the receiving end of a terminal device such as a satellite navigator or mobile phone, the method comprising the following steps:

[0033] Receive satellite signals, and transmit each signal in the received satellite signals at the middle frequency, both sides of the middle frequency, the upper and lower sidebands of the middle frequency, or both sides of the upper and lower sidebands of the middle frequency, respectively, of adjacent navigation frequencies or given communication frequencies.

[0034] The received satellite signal is down-converted and amplified with low noise to obtain the baseband satellite signal;

[0035] The baseband satellite signal is decarrier processed to obtain a decarrier signal;

[0036] The decarrier signal is correlated and demodulated to obtain satellite navigation messages transmitted by N adjacent navigation satellites of Beidou navigation satellites, or to obtain short messages transmitted by terminal devices of different satellite navigation instruments or mobile phones operating at a given communication frequency of navigation and communication satellites.

[0037] Thirdly, the present invention provides a transmitting end, comprising:

[0038] The navigation message or short message acquisition module is used to acquire satellite navigation messages transmitted by N adjacent navigation frequencies of Beidou navigation satellites, or to acquire short messages transmitted by the terminal equipment of satellite navigators or mobile phones operating on a given communication frequency of navigation and communication satellites.

[0039] A dedicated ranging code implementation module is used to generate dedicated ranging codes for BeiDou navigation satellites, satellite navigation devices, or mobile phone terminal devices;

[0040] The spread spectrum module is used to spread the satellite navigation messages or short messages transmitted on each navigation or communication frequency using the dedicated ranging code, so as to obtain the spread spectrum signal transmitted on the navigation or communication frequency.

[0041] A carrier modulation module is used to modulate the spread spectrum signal transmitted at the navigation or communication frequency with different carriers according to the transmission requirements.

[0042] The signal superposition module is used to superimpose different carrier modulation signals of navigation satellites to obtain a single-channel satellite carrier modulation signal of the navigation satellite;

[0043] The baseband signal generation module is used to perform Doppler frequency shift and add noise to the single-channel satellite carrier modulation signal of the navigation satellite or the navigation communication carrier modulation signal of each terminal device to obtain the baseband satellite signal, which is then transmitted after radio frequency modulation and power amplification.

[0044] The transmitter is used to implement the steps in the above-described method for multiplexing adjacent multi-frequency satellite navigation signals.

[0045] Fourthly, the present invention provides a receiving end, comprising:

[0046] The baseband signal acquisition module is used to receive satellite signals and perform down-conversion and low-noise amplification on the satellite signals to obtain baseband satellite signals.

[0047] A decarrier module is used to perform decarrier processing on the baseband satellite signal to obtain a decarrier signal;

[0048] The correlation demodulation module is used to perform correlation demodulation on the carrier-decarrier signal to obtain satellite navigation messages transmitted by N adjacent navigation frequencies of the Beidou navigation satellite, or to obtain short messages transmitted by terminal devices of different satellite navigation instruments or mobile phones operating on a given communication frequency of the navigation and communication satellite.

[0049] The receiving end is used to implement the steps in the above-described method for multiplexing adjacent multi-frequency satellite navigation signals.

[0050] Fifthly, the present invention provides an adjacent multi-frequency satellite navigation signal multiplexing system, comprising: the aforementioned transmitter and the aforementioned receiver, wherein the transmitter and the receiver are communicatively connected.

[0051] One or more technical solutions provided in this invention have at least the following technical effects or advantages:

[0052] In this invention, at the transmitting end of a BeiDou navigation satellite, satellite navigator, or mobile phone terminal device, satellite navigation messages or short messages transmitted on adjacent BeiDou navigation frequencies or on the communication frequencies of navigation and communication satellites operated by the satellite navigator or mobile phone terminal device are first spread using different ranging codes, and then modulated with different carriers. The modulated signals of all carriers of the navigation satellite are superimposed to form a single-channel satellite carrier modulated signal. Then, Doppler frequency shifting and noise are added to obtain baseband satellite signals. Finally, after radio frequency modulation and power amplification, the signals are transmitted by their respective antennas. The signals in the transmitted satellite signals are transmitted at the middle frequency, both sides of the middle frequency, the upper and lower sidebands of the middle frequency, or both sides of the upper and lower sidebands of the middle frequency, respectively, realizing the multiplexing of adjacent multi-frequency satellite navigation signals or communication signals at the transmitting end. On the other hand, at the receiving end of the BeiDou navigation satellite, satellite navigator, or mobile phone terminal equipment system, the received satellite signal is down-converted and amplified with low noise to obtain the baseband satellite signal. Then, the baseband satellite signal undergoes decarrier processing to obtain a decarrier signal (i.e., removing the corresponding carrier at the middle frequency, both sides of the middle frequency, or the upper and lower sidebands of the middle frequency, respectively, between adjacent navigation or communication frequencies). Finally, the decarrier signal is subjected to correlation demodulation to obtain the satellite navigation message or short message transmitted at the corresponding frequency. This invention provides a specific implementation method for adjacent multi-frequency satellite navigation signal multiplexing technology. This invention can be widely applied to satellite navigation systems, and can also be used in various ranging systems, communication systems, broadcasting systems, and control systems. Furthermore, this invention also provides a specific implementation system for adjacent multi-frequency satellite navigation signal multiplexing technology, providing a specific technical solution for solving this technical problem in the field, and also contributing to further exploration in this field. Attached Figure Description

[0053] Figure 1 This is a flowchart illustrating a method for multiplexing adjacent multi-frequency satellite navigation signals provided in Embodiment 1 of the present invention;

[0054] Figure 2 It is the first navigation frequency CA code in Embodiment 1 of the present invention;

[0055] Figure 3 It is the first navigation frequency BPSK modulation signal in Embodiment 1 of the present invention;

[0056] Figure 4 It is the second navigation frequency subcarrier modulation signal in Embodiment 1 of the present invention;

[0057] Figure 5 It is the fourth navigation frequency subcarrier modulation signal in Embodiment 1 of the present invention;

[0058] Figure 6 It is the complex subcarrier modulation signal of the 5th to 6th navigation frequency in Embodiment 1 of the present invention;

[0059] Figure 7 It is the intermodulation signal of six adjacent navigation frequency signals in Embodiment 1 of the present invention;

[0060] Figure 8 This refers to the baseband satellite transmission signal in Embodiment 1 of the present invention;

[0061] Figure 9 This is a functional block diagram of an adjacent multi-frequency satellite navigation signal multiplexing system provided in Embodiment 4 of the present invention. Detailed Implementation

[0062] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0063] Example 1:

[0064] Example 1 provides a method for multiplexing adjacent multi-frequency satellite navigation signals, including the following two aspects:

[0065] (1) Applied to the transmitter of a BeiDou navigation satellite, or applied to a terminal device of a satellite navigation device or mobile phone, the method includes the following steps:

[0066] Obtain satellite navigation messages transmitted by N adjacent navigation frequencies of Beidou navigation satellites, or obtain short messages transmitted by terminal devices of different satellite navigation devices or mobile phones operating on a given communication frequency of navigation and communication satellites;

[0067] Obtain the dedicated ranging code of the terminal equipment of Beidou navigation satellites, satellite navigation devices, or mobile phones;

[0068] The satellite navigation messages or short messages transmitted on each navigation or communication frequency are spread using the dedicated ranging code to obtain spread spectrum signals.

[0069] The spread spectrum signal is modulated with different carriers according to transmission requirements to obtain navigation satellite carrier modulated signals or navigation communication carrier modulated signals of each terminal device;

[0070] In this process, different carrier modulation signals of navigation satellites are superimposed to obtain a single-channel satellite carrier modulation signal of the navigation satellite;

[0071] Doppler frequency shift and noise are applied to the single-channel satellite carrier modulation signal of the navigation satellite or the navigation communication carrier modulation signal of each terminal device to obtain the baseband satellite signal of the navigation satellite or the baseband satellite signal of each terminal device.

[0072] The baseband satellite signal is modulated by radio frequency and amplified by power and then transmitted by the antenna of the navigation satellite or the antenna of each terminal device. The transmitted signals are transmitted at the middle frequency of adjacent navigation frequencies or given communication frequencies, the two sides of the middle frequency, the upper and lower sidebands of the middle frequency, or the two sides of the upper and lower sidebands of the middle frequency.

[0073] (2) Applied to the receiving end of a BeiDou navigation satellite, or applied to a terminal device of a satellite navigation device or mobile phone, the method includes the following steps:

[0074] Receive satellite signals, and transmit each signal in the received satellite signals at the middle frequency, both sides of the middle frequency, the upper and lower sidebands of the middle frequency, or both sides of the upper and lower sidebands of the middle frequency, respectively, of adjacent navigation frequencies or given communication frequencies.

[0075] The received satellite signal is down-converted and amplified with low noise to obtain the baseband satellite signal;

[0076] The baseband satellite signal is decarrier processed to obtain a decarrier signal;

[0077] The decarrier signal is correlated and demodulated to obtain satellite navigation messages transmitted by N adjacent navigation frequencies of the Beidou navigation satellite, or to obtain short messages transmitted by terminal devices of different satellite navigation instruments or mobile phones operating on a given communication frequency of the navigation and communication satellite.

[0078] The following section, combining the corresponding methods and steps of the transmitting and receiving ends, takes the application of both the transmitting and receiving ends to BeiDou navigation satellites as an example to illustrate the complete method of multiplexing adjacent multi-frequency satellite navigation signals.

[0079] This invention provides a method for multiplexing adjacent multi-frequency satellite navigation signals, comprising the following steps:

[0080] S1. Obtain satellite navigation messages transmitted from N adjacent navigation frequencies of Beidou navigation satellites (each frequency can transmit single, dual, or multiple signals).

[0081] Among them, satellite navigation messages can be traditional frame structure D series, data block, or hybrid frame structure B-CNAV series.

[0082] S2. A pseudo-random code generator consisting of two linear functions corresponding to given parameters (frequency, level, and code length) or a nonlinear pseudo-random code generator consisting of different variables or functions is started with the initial state value of the register. The phase taps of the relevant registers are combined and output as feedback values, or the weighted mixed operation value or the mutually driving value through nonlinear functions is used as feedback values. A Beidou navigation satellite identification ranging code is generated by shifting a portion of the phase combination taps of the registers.

[0083] S3. Generate the common ranging codes required for the N navigation messages of each Beidou navigation satellite through the output of the phase combination taps of another part of the registers.

[0084] S4. Exclusive-OR the common ranging codes of each satellite navigation message with the ranging codes of the Beidou navigation satellite identifiers respectively to obtain the dedicated ranging codes of each satellite navigation message corresponding to the Beidou navigation satellite.

[0085] S5. Spread-spectrum the satellite navigation messages transmitted at each navigation frequency with the dedicated ranging codes of each satellite navigation message respectively to obtain spread-spectrum signals.

[0086] S6. Generate different square-wave basic subcarriers with a given standard frequency or frequency multiplication and different phases.

[0087] S7. Perform BPSK or QPSK modulation with different frequencies or phases on the spread-spectrum signals transmitted at the 1st to m (m < N) navigation frequencies respectively to obtain phase-shift keying modulation signals.

[0088] S8. Combine or synthesize a composite real or complex subcarrier according to a given rule with a certain power ratio by using multiple different square-wave basic subcarriers, or synthesize it through operations. Multiply or exclusive-OR the corresponding code bits of the spread-spectrum signals transmitted at the m + 1st to n (m < n < N) navigation frequencies respectively by using the obtained composite subcarrier to achieve subcarrier modulation, and obtain subcarrier modulation signals.

[0089] S9. Use complex subcarriers or other subcarriers composed of sin or cos function carriers or square-wave basic subcarriers with the same or different frequencies or phases to perform main carrier modulation on different subcarrier modulation signals respectively to obtain offset carrier signals.

[0090] S10. Respectively construct a set of complex subcarriers with orthogonal imaginary parts and complex subcarriers with inverted phases by using the square-wave basic subcarriers obtained in step S6.

[0091] S11. Multiply the spread-spectrum signals transmitted at the remaining (n + 1)st to Nth navigation frequencies respectively by the complex subcarriers with orthogonal imaginary parts.

[0092] S12. Multiply the spread-spectrum signals transmitted at N navigation frequencies respectively to obtain intermodulation signals.

[0093] S13. Multiply the intermodulation signals respectively by the complex subcarriers with inverted phases.

[0094] S14. Superimpose the different carrier modulation signals obtained in steps S7, S9, S11, and S13 into a single-channel satellite signal.

[0095] S15. Provide Doppler frequency shift and add noise to form a baseband satellite signal.

[0096] S16. After radio frequency modulation and power amplification, the signal is transmitted by the antenna. After the above multiplexing process, each navigation signal is transmitted at the middle frequency, both sides of the middle frequency, and the upper and lower sidebands of the middle frequency, respectively.

[0097] S17. The receiving end (e.g., a user multi-channel receiver) receives satellite signals.

[0098] S18. The satellite signal is down-converted, filtered by a broadband low-pass or band-pass filter, and amplified with low noise to obtain a baseband satellite signal.

[0099] S19. Use the Doppler frequency shift filtering method to remove the offset carrier or carrier to obtain the decarrier signal.

[0100] S20. Obtain the satellite navigation messages transmitted at N adjacent navigation frequencies through relevant demodulation.

[0101] In step S1, the BeiDou satellite navigation message implementation structure can be either a serial transmission mode or a parallel superposition transmission mode. That is, according to the superframe, frame, subframe, and word structure of the satellite navigation message, or according to the given code length, the satellite navigation message is grouped into short messages and transmitted in parallel superposition or different satellite navigation messages are transmitted in parallel superposition.

[0102] In step S2, the satellite ranging code used by each adjacent or non-adjacent navigation frequency is generated by a combination of different register phase taps of linear or nonlinear shift pseudo-random code generators with the same or different parameters, or by a combination thereof.

[0103] In steps S8 and S10, the combined modulation rule is to modulate different numerical code points of the navigation spread spectrum signal or the spread spectrum codes of each segment of time division multiplexing using square wave fundamental subcarriers of the same or different frequencies or phases, or to use square wave fundamental subcarriers of the same or different frequencies or phases to modulate the spread spectrum codes according to different spread spectrum code distribution densities, or to use square wave fundamental subcarriers of different harmonics to modulate the given spread spectrum code points in each segment of time division multiplexing, and to use square wave fundamental subcarriers of standard frequencies to modulate the remaining spread spectrum code points; the operation is performed in the time domain or Square wave basic subcarriers with the same or different frequencies, phases, or functions in the frequency domain are synthesized into composite real or complex subcarriers or complex subcarriers through weighted addition, subtraction, multiplication, division, exponentiation, square root, XOR, or their weighted mixed operations with a certain power ratio. These operations or square wave basic subcarriers can be reused in the synthesis process. The basic subcarriers used are at least one periodic or aperiodic binary, binary, binarized, multi-valued, multi-valued, or combination or mixed operation wave of the same or different types, frequencies, or phases.

[0104] In steps S7, S9 and S11, the spread spectrum signals or carrier signals of each satellite can be superimposed, or the spread spectrum signals of each satellite can be superimposed in the carrier phase.

[0105] In steps S9 and S10, square wave basic subcarriers with the same or different frequencies, phases, or functions in the time or frequency domain are transformed by weighted addition, subtraction, multiplication, division, exponentiation, square root, XOR, or weighted mixed operations to generate composite real or complex subcarriers or complex subcarriers. These operations or square wave basic subcarriers can be reused in the process of synthesizing composite real or complex subcarriers or complex subcarriers.

[0106] In steps S7, S9, and S10, each carrier phase is orthogonal or non-orthogonal, correlated or uncorrelated, and can respectively modulate a single-channel or complex dual-channel or multiplexed signal.

[0107] In steps S7, S9, S16, S18 and S20, the signal is realized using electrons, photons, quanta, protons, neutrons and mesons as carriers.

[0108] The following explanation will illustrate the principle of frequency reuse using six adjacent frequencies of the BeiDou system to transmit different navigation messages and employing different carrier waves. (See [link]). Figure 1 The implementation steps are as follows:

[0109] S1. Obtain satellite navigation messages transmitted by six adjacent BeiDou navigation frequencies (in this example, navigation frequencies 1 to 4 transmit single-channel navigation signals, and navigation frequencies 5 to 6 transmit multiple dual-channel navigation signals respectively);

[0110] S2, two linear shift pseudo-random code generators with a frequency of 1.023MHz, 11 levels, and a code length of 128, generate Beidou navigation satellite identification ranging codes by shifting a portion of the register phase combination taps;

[0111] S3. Generate the universal ranging code required for the navigation messages of the six satellites of each Beidou navigation satellite by using the phase combination taps of another part of the register.

[0112] S4. The universal ranging code of each satellite navigation message is XORed with the BeiDou navigation satellite identifier ranging code to obtain the dedicated ranging code for each satellite navigation message corresponding to that BeiDou navigation satellite. For example, the CA code of the first navigation frequency is as follows: Figure 2 As shown;

[0113] S5. Spread the satellite navigation messages of each channel using the dedicated ranging code of the Beidou navigation message to obtain spread spectrum navigation signals transmitted at 6 navigation frequencies.

[0114] S6 generates square wave signals with standard frequency, 2nd harmonic, 5th harmonic, and different phases;

[0115] S7. Modulate the first spread spectrum navigation signal using BPSK with a phase of 0°. The modulated signal (i.e., the first navigation frequency BPSK modulated signal) is as follows: Figure 3 As shown;

[0116] S8. Divide the 128-bit spreading code into 16 time slots. For the second spreading navigation signal, the 5th and 8th spreading code bits in the time slot are modulated with 2x and 5x frequency square waves respectively, and the remaining spreading code bits are modulated with standard frequency square waves. The modulated signal (i.e., the second navigation frequency subcarrier modulated signal) is as follows: Figure 4 As shown; for the third spread spectrum navigation signal, each spreading code is sequentially modulated using standard frequency, second harmonic, and fifth harmonic square waves, respectively; for the fourth spread spectrum navigation signal, a composite subcarrier obtained by mixing addition, subtraction, multiplication, and division operations on standard frequency, second harmonic, and fifth harmonic square waves is used for modulation. The modulated signal (the fourth navigation frequency subcarrier modulated signal) is as follows. Figure 5 As shown;

[0117] S9. Using sin or cos carriers with a frequency of 10.23MHz and phases of 10°, 30° and 50°, sin and cos carriers with phases of 20°, 40° and 60°, and sin and cos carriers with a phase of 70°, respectively, the second, third and fourth navigation frequency subcarrier modulation signals are modulated by the main carrier.

[0118] S10. Using a square wave with a frequency of 5.11MHz and phases of -45°, 0° and 45° respectively, the real part is obtained through XOR operation and addition operation, and the imaginary part is obtained through addition, multiplication and division operation. A set of complex subcarriers with orthogonal imaginary parts and complex subcarriers with inverted phases are constructed respectively.

[0119] S11, the complex subcarriers are multiplied by the spread spectrum complex navigation signals transmitted at the remaining two navigation frequencies (i.e., the 5th and 6th spread spectrum navigation signals), respectively, to obtain the complex subcarrier modulation signals for the 5th and 6th navigation frequencies as follows: Figure 6 As shown;

[0120] The spread spectrum navigation signals transmitted at the S12 and 6 navigation frequencies are multiplied to obtain the intermodulation signal, such as... Figure 7 As shown;

[0121] S13. The intermodulation signal is multiplied by a complex subcarrier with its phase reversed;

[0122] S14. The signals obtained in step S7 (i.e., the first navigation frequency BPSK modulation signal), the signals obtained in step S9 (i.e., the signals after the second, third, and fourth navigation frequency subcarrier modulation signals are modulated by the main carrier), the signals obtained in step S11 (i.e., the fifth and sixth navigation frequency complex subcarrier modulation signals), and the signals obtained in S13 (i.e., the signals after the intermodulation signal is multiplied by the phase-inverted complex subcarrier) are superimposed to obtain a single-path satellite navigation signal.

[0123] S15 provides a 500Hz Doppler frequency shift and adds -10dB Gaussian white noise to form a baseband satellite navigation signal, such as Figure 8 As shown;

[0124] S16. The baseband satellite navigation signal is transmitted through the antenna after being modulated by radio frequency and amplified by power. After the above multiplexing process, each navigation signal is transmitted at the middle frequency of adjacent frequencies, the two sides of the middle frequency, and the upper and lower sidebands of the middle frequency, respectively.

[0125] S17. The user's multi-channel receiver receives satellite navigation signals via an antenna;

[0126] S18. The satellite navigation signal is down-converted, broadband low-pass or band-pass filtered and amplified with low noise to obtain the baseband satellite navigation signal;

[0127] S19. Use the Doppler frequency shift filtering method to remove the offset carrier or carrier from the baseband satellite navigation signal to obtain the decarrier signal;

[0128] S20. Obtain satellite navigation messages transmitted at adjacent multiple frequencies through relevant demodulation.

[0129] Example 2:

[0130] Example 2 provides a transmitter, see [link to example]. Figure 9 ,include:

[0131] The navigation message or short message acquisition module is used to acquire satellite navigation messages transmitted by N adjacent navigation frequencies of Beidou navigation satellites, or to acquire short messages transmitted by the terminal equipment of satellite navigators or mobile phones operating on a given communication frequency of navigation and communication satellites.

[0132] A dedicated ranging code implementation module is used to generate dedicated ranging codes for BeiDou navigation satellites, satellite navigation devices, or mobile phone terminal devices;

[0133] The spread spectrum module is used to spread the satellite navigation messages or short messages transmitted on each navigation or communication frequency using the dedicated ranging code, so as to obtain the spread spectrum signal transmitted on the navigation or communication frequency.

[0134] A carrier modulation module is used to modulate the spread spectrum signal transmitted at the navigation or communication frequency with different carriers according to the transmission requirements.

[0135] The signal superposition module is used to superimpose different carrier modulation signals of navigation satellites to obtain a single-channel satellite carrier modulation signal of the navigation satellite;

[0136] The baseband signal generation module is used to perform Doppler frequency shift and add noise to the single-channel satellite carrier modulation signal of the navigation satellite or the navigation communication carrier modulation signal of each terminal device to obtain the baseband satellite signal, which is then transmitted after radio frequency modulation and power amplification.

[0137] The transmitter is used to implement the steps in the adjacent multi-frequency satellite navigation signal multiplexing method as described in Example 1.

[0138] Example 3:

[0139] Example 3 provides a receiving end, see Figure 9 ,include:

[0140] The baseband signal acquisition module is used to receive satellite signals and perform down-conversion and low-noise amplification on the satellite signals to obtain baseband satellite signals.

[0141] A decarrier module is used to perform decarrier processing on the baseband satellite signal to obtain a decarrier signal;

[0142] The correlation demodulation module is used to perform correlation demodulation on the carrier-decarrier signal to obtain satellite navigation messages transmitted by N adjacent navigation frequencies of the Beidou navigation satellite, or to obtain short messages transmitted by terminal devices of different satellite navigation instruments or mobile phones operating on a given communication frequency of the navigation and communication satellite.

[0143] The receiving end is used to implement the steps in the adjacent multi-frequency satellite navigation signal multiplexing method as described in Embodiment 1.

[0144] Example 4:

[0145] Example 4 provides an adjacent multi-frequency satellite navigation signal multiplexing system, including a transmitter as provided in Example 2 and a receiver as provided in Example 3. The transmitter and the receiver are communicatively connected. The overall system is described below. Figure 9 .

[0146] In summary, this invention enables the composite transmission of adjacent multi-frequency satellite navigation signals, and can multiplex multiple satellite signals at the middle frequency, both sides of the middle frequency, the upper and lower sidebands of the middle frequency, or both sides of the upper and lower sidebands of the middle frequency, between adjacent navigation frequencies or a given communication frequency. Furthermore, the carrier implementation technology in this invention is diversified, and various offset carriers, carriers, or complex subcarriers can be achieved through waveform combination or hybrid operations.

[0147] Finally, it should be noted that the above specific embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to examples, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A method for multiplexing adjacent multi-frequency satellite navigation signals, characterized in that, The method, applied to the transmitter of a BeiDou navigation satellite or a terminal device for a satellite navigation device or mobile phone, includes the following steps: Obtain satellite navigation messages transmitted by N adjacent navigation frequencies of Beidou navigation satellites, or obtain short messages transmitted by terminal devices of different satellite navigation devices or mobile phones operating on a given communication frequency of navigation and communication satellites; Obtain the dedicated ranging code of the terminal equipment of Beidou navigation satellites, satellite navigation devices, or mobile phones; The satellite navigation messages or short messages transmitted on each navigation or communication frequency are spread using the dedicated ranging code to obtain spread spectrum signals. The spread spectrum signal is modulated with different carriers according to transmission requirements to obtain navigation satellite carrier modulated signals or navigation communication carrier modulated signals of each terminal device; In this process, different carrier modulation signals of navigation satellites are superimposed to obtain a single-channel satellite carrier modulation signal of the navigation satellite; Doppler frequency shift and noise are added to the single-channel satellite carrier modulation signal of the navigation satellite or the navigation communication carrier modulation signal of each terminal device to obtain the baseband satellite signal of the navigation satellite or each terminal device; The baseband satellite signal is modulated by radio frequency and amplified by power and then transmitted by the antenna of the navigation satellite or the antenna of each terminal device. The transmitted signals are transmitted at the middle frequency, both sides of the middle frequency, the upper and lower sidebands of the middle frequency, or both sides of the upper and lower sidebands of the middle frequency, respectively, of the adjacent navigation frequency of the navigation satellite or the given communication frequency of the navigation and communication satellite.

2. The method for multiplexing adjacent multi-frequency satellite navigation signals according to claim 1, characterized in that, The navigation or communication frequency transmits single, dual, or multiple signals; the satellite navigation message is a satellite navigation message with a traditional frame structure D series, a data block structure B-CNAV series, or a hybrid frame structure B-CNAV series; the satellite navigation message or short message adopts serial transmission or parallel superposition transmission.

3. The method for multiplexing adjacent multi-frequency satellite navigation signals according to claim 1, characterized in that, Obtaining the dedicated ranging code from a BeiDou navigation satellite, satellite navigation device, or mobile phone terminal device includes the following sub-steps: A pseudo-random code generator, consisting of two linear functions corresponding to given parameters or a nonlinear pseudo-random code generator containing different variables or functions, is started with the initial state value of a register. It uses the combined output of relevant register phase taps as a feedback value, or uses a weighted mixture of nonlinear functions or mutually driving values ​​as a feedback value. By shifting a portion of the register phase combination taps in the pseudo-random code generator, it generates an identification ranging code for a BeiDou navigation satellite, satellite navigation device, or mobile phone terminal device. The given parameters include frequency, number of levels, and code length. The general ranging code required for N satellite navigation messages of navigation satellites or short messages of various terminal devices is generated by outputting the phase combination tap of another part of the register in the pseudo-random code generator. The general ranging code required for the N satellite navigation messages of the navigation satellite or the short messages of each terminal device is XORed with the identification ranging code of the Beidou navigation satellite or the terminal device to obtain the special ranging code of the N satellite navigation messages of the Beidou navigation satellite or the short messages of each terminal device.

4. The method for multiplexing adjacent multi-frequency satellite navigation signals according to claim 1, characterized in that, The specific implementation methods for obtaining the single-channel satellite carrier modulation signal of the navigation satellite, or the navigation communication modulation signal of each terminal device, are as follows: The N spread spectrum navigation signals of navigation satellites, or a portion of the spread spectrum communication signals of satellite navigation devices or mobile phones, are modulated by BPSK or QPSK at different frequencies or at the same frequency but different phases to obtain phase shift keying modulation signals, which are then used as the first type of modulation signals for navigation satellites or various terminal devices. Generate multiple square wave basic subcarriers with different frequencies or the same frequency but different phases; Multiple different square wave basic subcarriers are combined or synthesized to form a composite subcarrier. The composite subcarrier is a composite real subcarrier or a composite complex subcarrier. The composite subcarrier is used to modulate another part of N spread spectrum navigation signals or spread spectrum communication signals to obtain the corresponding subcarrier modulated signal. Different subcarrier modulation signals are modulated by orthogonal or non-orthogonal main carriers to obtain offset carrier signals, which are used as the second type of modulation signals for navigation satellites or various terminal devices; Using the obtained multiple different square wave basic subcarriers, a set of complex subcarriers with orthogonal imaginary parts and complex subcarriers with inverted phases are constructed; the remaining parts of N spread spectrum navigation signals or spread spectrum communication signals or subcarrier modulation signals are multiplied by the complex subcarriers with orthogonal imaginary parts respectively to obtain complex subcarrier modulation signals, which are used as the third type of modulation signals for navigation satellites or various terminal devices; The spread spectrum signals transmitted at N navigation frequencies are multiplied together to obtain intermodulation signals; the intermodulation signals are multiplied together with the phase-inverted complex subcarriers to obtain intermodulation modulation signals, which are used as the fourth type of modulation signals for navigation satellites. The first, second, third, and fourth type modulation signals of the navigation satellite are superimposed to obtain the single-channel satellite carrier modulation signal of the navigation satellite; while the first, second, and third type modulation signals of each terminal device are their respective navigation communication modulation signals.

5. The method for multiplexing adjacent multi-frequency satellite navigation signals according to claim 4, characterized in that, The specific implementation of using multiple different square wave basic subcarriers to combine or synthesize to form a composite subcarrier, and using multiple different square wave basic subcarriers to construct a set of complex subcarriers with orthogonal imaginary parts and complex subcarriers with inverted phases, is as follows: using multiple different square wave basic subcarriers to synthesize complex subcarriers through calculation. The combined modulation rule is to use square wave basic subcarriers of the same or different frequencies or phases to modulate different numerical code points of the navigation spread spectrum signal or to modulate the spread spectrum codes of each segment of time division multiplexing, or to use square wave basic subcarriers of the same or different frequencies or phases to modulate according to different spread spectrum code distribution densities, or to use square wave basic subcarriers of different harmonics to modulate the given spread spectrum code points in each segment of time division multiplexing, and to use square wave basic subcarriers of standard frequency to modulate the remaining spread spectrum code points. The operation involves transforming square wave basic subcarriers with the same or different frequencies, phases, or functions in the time or frequency domains, and then synthesizing composite subcarriers or complex subcarriers through weighted addition, subtraction, multiplication, division, exponentiation, square root, XOR, or a mixture of the above weighted operations. The basic subcarrier used is at least one periodic or aperiodic binary, binary, binarized, multi-valued, multi-valued, or combination or mixture of these operations of the same or different types or frequencies or phases. The operations or basic subcarriers used can be reused during the synthesis process.

6. The method for multiplexing adjacent multi-frequency satellite navigation signals according to claim 4, characterized in that, During the process of obtaining phase shift keying modulation signals, offset carrier signals, and complex subcarrier modulation signals, the spread spectrum navigation or communication signals or carrier signals are superimposed, or the spread spectrum navigation or communication signals are superimposed in the carrier phase.

7. A method for multiplexing adjacent multi-frequency satellite navigation signals, characterized in that, The method, applied to the receiving end of a BeiDou navigation satellite or a satellite navigation device or mobile phone terminal, includes the following steps: Receive satellite signals, and transmit each signal in the received satellite signals at the middle frequency, both sides of the middle frequency, the upper and lower sidebands of the middle frequency, or both sides of the upper and lower sidebands of the middle frequency, of the adjacent navigation signal frequency or the given communication frequency. The received satellite signal is down-converted and amplified with low noise to obtain the baseband satellite signal; The baseband satellite signal is decarrier processed to obtain a decarrier signal; The decarrier signal is correlated and demodulated to obtain satellite navigation messages transmitted by N adjacent navigation frequencies of the Beidou navigation satellite, or to obtain short messages transmitted by terminal devices of different satellite navigation instruments or mobile phones operating on a given communication frequency of the navigation and communication satellite.

8. A transmitter, characterized in that, include: The navigation message or short message acquisition module is used to acquire satellite navigation messages transmitted by N adjacent navigation frequencies of Beidou navigation satellites, or to acquire short messages transmitted by the terminal equipment of satellite navigators or mobile phones operating on a given communication frequency of navigation and communication satellites. A dedicated ranging code implementation module is used to generate dedicated ranging codes for BeiDou navigation satellites, satellite navigation devices, or mobile phone terminal devices; The spread spectrum module is used to spread the satellite navigation messages or short messages transmitted on each navigation or communication frequency using the dedicated ranging code, so as to obtain the spread spectrum signal transmitted on the navigation or communication frequency. A carrier modulation module is used to modulate the spread spectrum signal transmitted at the navigation or communication frequency with different carriers according to the transmission requirements. The signal superposition module is used to superimpose different carrier modulation signals of navigation satellites to obtain a single-channel satellite carrier modulation signal of the navigation satellite; The baseband signal generation module is used to perform Doppler frequency shift and add noise to the single-channel satellite carrier modulation signal of the navigation satellite or the navigation communication carrier modulation signal of each terminal device to obtain the baseband satellite signal, which is used to transmit the baseband satellite signal after radio frequency modulation and power amplification. The transmitter is used to implement the steps in the adjacent multi-frequency satellite navigation signal multiplexing method as described in any one of claims 1-6.

9. A receiving end, characterized in that, include: The baseband signal acquisition module is used to receive satellite signals and perform down-conversion and low-noise amplification on the satellite signals to obtain baseband satellite signals. A decarrier module is used to perform decarrier processing on the baseband satellite signal to obtain a decarrier signal; The correlation demodulation module is used to perform correlation demodulation on the carrier-decarrier signal to obtain satellite navigation messages transmitted by N adjacent navigation frequencies of the Beidou navigation satellite, or to obtain short messages transmitted by terminal devices of different satellite navigation instruments or mobile phones operating on a given communication frequency of the navigation and communication satellite. The receiving end is used to implement the steps in the adjacent multi-frequency satellite navigation signal multiplexing method as described in claim 7.

10. A system for multiplexing adjacent multi-frequency satellite navigation signals, characterized in that, include: The transmitter as described in claim 8 and the receiver as described in claim 9 are communicatively connected.

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