Low-orbit navigation element signal generating and processing method

Abstract

The invention discloses a low-orbit navigation element signal generation and processing method. The signal generation comprises the following steps: calculating the center frequency of an element signal; generating upper and lower sideband signal base bands; carrying out periodic subcarrier modulation; generating a baseband signal of the element signal; and generating and broadcasting the element signal radio frequency signal. Meanwhile, a receiving end adopts a meta-signal receiving and processing method, so that the code tracking measurement precision is improved. According to the invention, aiming at the requirement of broadcasting the double-frequency signal in low-orbit navigation enhancement, the interference on the same-frequency-band GNSS signal can be reduced, and the global all-time double-frequency signal landing is realized.

Description

Technical Field

[0001] The invention belongs to the field of satellite navigation, and in particular relates to a method for realizing a low-orbit navigation element signal. Background Art

[0002] In recent years, emerging industries represented by autonomous driving have increasingly urgent demands for real-time high-precision positioning, driving the rapid development of low-orbit navigation augmentation systems. Compared with medium- and high-orbit navigation satellites, low-orbit satellites move faster and their geometric configuration changes rapidly relative to ground users. When combined with medium- and high-orbit global navigation satellite systems (GNSS), they can accelerate the convergence of precise point positioning (PPP).

[0003] Both domestic and foreign governments have proposed to build low-orbit navigation augmentation systems and conduct technical experiments. It has become a consensus at home and abroad to achieve fast convergence and high-precision PNT services through low-orbit navigation augmentation systems. The implementation method is to broadcast low-orbit navigation augmentation dual-frequency signals. The frequency bands of low-orbit navigation augmentation signals are mainly concentrated in the L band, mainly in the GNSS L band and the 1518-1525MHz band. The purpose of broadcasting dual-frequency signals is to eliminate ionospheric errors. Broadcasting in the GNSS L band can share the RF receiving channel with the GNSS signal, reducing the complexity and cost of the receiving end.

[0004] However, broadcasting low-orbit navigation augmentation signals in the GNSS L-band faces compatibility issues. With the increase in low-orbit navigation augmentation satellites, how to reduce the interference of low-orbit navigation augmentation signals on GNSS signals and achieve compatibility has become a difficult problem; for non-traditional satellite navigation bands such as 1518-1525MHz, the business regulations of different countries are different, and it may not be guaranteed to be used for low-orbit navigation services worldwide. Summary of the invention

[0005] The technical problem solved by the present invention is: to overcome the shortcomings of the prior art and provide a low-orbit navigation enhancement meta-signal generation and processing method. In view of the need for broadcasting dual-frequency signals for low-orbit navigation enhancement, and the problem that some frequency points are difficult to implement globally, a meta-signal generation signal and production method are designed, which can meet the dual-frequency broadcasting requirements of low-orbit navigation signals and meet the compatibility with GNSS signals. When using signal reception and processing, it is expected to achieve higher code tracking accuracy.

[0006] The technical solution of the present invention is:

[0007] First,

[0008] A method for generating a low-orbit navigation meta-signal, comprising:

[0009] 1) Calculate the center frequency of the meta-signal to obtain the center frequency of the meta-signal of band 1 and the center frequency of the meta-signal of band 2; wherein, of the two frequency points of band 1, the frequency point with a lower frequency is called the lower sideband of band 1, and the frequency point with a higher frequency is called the upper sideband of band 1; of the two frequency points of band 2, the frequency point with a lower frequency is called the lower sideband of band 2, and the frequency point with a higher frequency is called the upper sideband of band 2;

[0010] 2) Generate upper and lower sideband baseband signals corresponding to frequency band 1 and frequency band 2 respectively; for frequency band i, i = 1 or 2, the lower sideband baseband signal of frequency band i is recorded as The upper sideband baseband signal of band i is denoted as t represents time;

[0011] 3) Perform periodic subcarrier modulation to convert the lower sideband baseband signal Modulate to the lower sideband and convert the upper sideband baseband signal Modulate to upper sideband;

[0012] 4) Generate a meta-signal baseband signal from the upper sideband signal and the lower sideband signal modulated by the periodic subcarrier;

[0013] 5) Generate and broadcast the meta-signal RF signal.

[0014] Preferably, in step 1), the center frequency of the meta-signal of frequency band 1 and the center frequency of the meta-signal of frequency band 2 are obtained, specifically:

[0015] The center frequency of the lower sideband of Band 1 is The center frequency of the upper sideband of Band 1 is The center frequency of the meta-signal of band 1 is

[0016] The center frequency of the lower sideband of Band 2 is The center frequency of the upper sideband of Band 2 is The center frequency of the meta-signal of band 2 is

[0017] Preferably, in step 2), the upper and lower sideband baseband signals corresponding to frequency band 1 and frequency band 2 respectively generated are specifically:

[0018] 21) Generate the spreading code sequence of the upper and lower sidebands; Generate the spreading code sequence of the lower sideband and Generate the spreading code sequence for the upper sideband and

[0019] 22) Generate the upper and lower sideband message symbols; Generate the lower sideband message symbols Message symbol with upper sideband

[0020] 23) Generate the lower sideband signal baseband; Spreading code sequence for lower sideband Perform baseband modulation to generate the lower sideband baseband signal of frequency band i:

[0021]

[0022] In the formula, represents the lower sideband baseband signal of frequency band i, is the spreading chip width of the lower sideband of band i, represents the chip modulation waveform, is a rectangular chip waveform; a rectangular chip waveform is defined as:

[0023]

[0024] 24) Generate the upper sideband signal baseband; Upper sideband spreading code sequence Perform baseband modulation to generate the upper sideband baseband signal of frequency band i:

[0025]

[0026] In the formula, represents the upper sideband baseband signal of frequency band i, is the spreading chip width of the upper sideband of band i, represents the chip modulation waveform, It is a rectangular chip waveform.

[0027] Preferably, in step 3), periodic subcarrier modulation is performed, specifically:

[0028] The lower sideband baseband signal of frequency band i is modulated by a periodic subcarrier to obtain a lower sideband signal modulated by a periodic subcarrier:

[0029]

[0030] In the formula, is an imaginary unit, is the lower sideband in-phase periodic subcarrier of band i, with a period of is the orthogonal phase periodic subcarrier of the lower sideband of band i, with a period of The period of the periodic subcarrier is The upper sideband baseband signal of frequency band i is modulated by a periodic subcarrier to obtain an upper sideband signal modulated by a periodic subcarrier:

[0031]

[0032] In the formula, is the upper sideband in-phase periodic subcarrier of band i, with a period of is the upper sideband orthogonal phase periodic subcarrier of band i, and the period of the periodic subcarrier is also

[0033] Preferably, the lower sideband of the frequency band i has an in-phase periodic subcarrier The lower sideband quadrature phase periodic subcarrier of band i The method for determining is as follows:

[0034] The lower sideband of band i is in phase with the periodic subcarrier With quadrature phase periodic subcarrier In a cycle The interior is divided into 8 equal parts, expressed as:

[0035]

[0036]

[0037] In the formula, and is the coefficient set of the lower sideband periodic subcarrier, m=1,2,……,7, these 8 coefficients are expressed as:

[0038]

[0039]

[0040] The upper sideband of band i is in phase with the periodic subcarrier With quadrature phase periodic subcarrier In a cycle The interior is divided into 8 equal parts, expressed as:

[0041]

[0042]

[0043] In the formula, and is the coefficient set of the upper sideband periodic subcarrier, m=1,2,……,7, and these 8 coefficients are respectively expressed as:

[0044]

[0045]

[0046] Preferably, the subcarrier coefficients in the coefficient set of the lower sideband periodic subcarrier are and Subcarrier coefficients in the coefficient set of the upper sideband periodic subcarrier and Obtained by the following method:

[0047] 321) Subcarrier coefficients and Subcarrier coefficient and The solution is transformed into a constrained nonlinear optimization problem

[0048]

[0049]

[0050] In the formula,

[0051]

[0052]

[0053]

[0054]

[0055] In the formula, the constraint equation Eq.1 is used to ensure that the baseband signal The constant envelope, the constraint equations Eq.2 and Eq.3 are used to ensure that the power ratio of the upper and lower sidebands is The constraint equation Eq.4 is used to ensure that the phase difference between the upper and lower sideband signals is Δθ (i) , the constraint equation Eq.5 is used to ensure that there is no harmonic signal in the band;

[0056] 322) Set the power ratio of the upper and lower sidebands Set the phase difference Δθ between the upper and lower sideband signals (i) ;

[0057] 323) A numerical optimization algorithm is used to solve the constrained nonlinear optimization problem and obtain the subcarrier coefficients and Subcarrier coefficient and

[0058] Preferably, the subcarrier coefficient and Subcarrier coefficient and The following update principles are met:

[0059] When you need to turn off the lower sideband signal, and Update to 0;

[0060] When you need to turn off the upper sideband signal, and Update to 0;

[0061] When you need to change the power distribution of the upper and lower sideband signals, reset The power ratio of the subcarrier coefficients is obtained by using a numerical optimization algorithm to solve the constrained nonlinear optimization problem. and Subcarrier coefficient and

[0062] Preferably, in step 4), the generating of the elementary signal baseband signal is specifically:

[0063] The baseband signal is expressed as:

[0064]

[0065] In the formula, represents the baseband signal of the element signal of frequency band i, Δθ (i) represents the phase difference between the upper and lower sideband signals of frequency band i, and

[0066] Further expressed as:

[0067]

[0068] In the formula, is the in-phase component of the baseband signal of the frequency band i, is the orthogonal component of the baseband signal of the element signal of frequency band i; and:

[0069]

[0070]

[0071] Generate cos(Δθ (i) ) and sin(Δθ (i) ), combined with the upper and lower sideband signals modulated by the periodic subcarrier, to complete the baseband signal generation of the meta-signal.

[0072] Preferably, in step 5), the meta-signal radio frequency signal is generated and broadcasted, specifically:

[0073] and The DAC is used to convert the analog signal, which is then up-converted, filtered, amplified, and broadcasted through the antenna. The RF signal of the meta-signal is generated and broadcasted through the antenna. The RF center frequency of the meta-signal is:

[0074]

[0075] The meta-signal RF signal is expressed as:

[0076]

[0077] Second,

[0078] A method for receiving and processing a low-orbit navigation meta-signal, receiving a meta-signal radio frequency signal obtained by a method for generating a low-orbit navigation meta-signal according to the first aspect, the receiving and processing method specifically comprising:

[0079] 101) The receiver antenna receives the RF signal after space propagation, amplifies it through a low noise amplifier, down-converts it, filters it, and converts it into a digital intermediate frequency signal after ADC sampling. T sample is the sampling rate, l represents the serial number of the sampling point;

[0080] 102) The digital intermediate frequency signal is multiplied by the local carrier generated by the receiver, and the carrier is stripped to obtain the received signal after the carrier is stripped. Specifically:

[0081]

[0082] 103) The receiver locally generates a forward reference signal of the baseband signal and reverse reference signal Specifically:

[0083]

[0084]

[0085] Wherein, q represents the sequence number of the sample value in the forward reference signal and the reverse reference signal, q∈[1,Q];

[0086] 104) The received signal after stripping the carrier and and Parallel correlation is performed respectively to obtain correlation values ​​corresponding to the Q forward reference signals and correlation values ​​corresponding to the Q reverse reference signals, which are specifically:

[0087]

[0088]

[0089] 105) Calculate the maximum amplitude of the correlation values ​​corresponding to the Q forward reference signals The maximum amplitude of the correlation value corresponding to Q reverse reference signals if Then select the forward reference signal in step 103) As the baseband signal generated locally by the receiver, the acquisition, tracking and demodulation process is completed; otherwise, the reverse reference signal in step 103) is selected As the baseband signal generated locally by the receiver, it completes the capture, tracking and demodulation processes.

[0090] The advantages of the present invention compared with the prior art are:

[0091] 1) The current low-orbit navigation signal is usually broadcast at two independent frequencies. The low-orbit navigation signal of the present invention is broadcast in two independent frequency bands, each of which includes two adjacent frequencies, and each frequency can broadcast a signal, so it is a dual-band four-frequency signal. When the signal of one frequency cannot land, it is possible to broadcast only the signal component of another frequency by updating the subcarrier coefficient to ensure that there is a signal broadcast in this frequency band, thereby ensuring the broadcast of the low-orbit dual-frequency navigation signal.

[0092] 2) Existing dual-frequency constant envelope signal generation methods are all designed for GNSS signals. They are either only applicable to the dual-frequency four-component case and implemented by a lookup table; or they require single-frequency constant envelope modulation first, and then dual-frequency constant envelope modulation, and the upper and lower sideband signal components use the same modulation method. The present invention is aimed at the dual-frequency two-component case, and is generated based on the meta-signal expression. It only requires solving four subcarrier coefficients to realize meta-signal generation, and the modulation methods of the upper and lower sideband signal components can be different.

[0093] 3) The meta-signal generation method proposed in the present invention can achieve this by simply setting the subcarrier coefficient of the corresponding sideband to 0 when turning off a sideband component, without affecting the signal of the other sideband and ensuring the continuity of the other sideband signal, which cannot be met by existing methods. BRIEF DESCRIPTION OF THE DRAWINGS

[0094] Figure 1 The method for generating low-orbit navigation meta-signals disclosed in the present invention;

[0095] Figure 2 The waveform diagram of the lower sideband periodic subcarrier when the upper and lower sideband power ratio is 1:2;

[0096] Figure 3 The upper sideband periodic subcarrier waveform diagram when the upper and lower sideband power ratio is 1:2;

[0097] Figure 4 It is the power spectrum of the element signal when the upper and lower sideband power ratio is 1:2;

[0098] Figure 5 This is the power spectrum of the meta-signal after turning off the lower sideband;

[0099] Figure 6 This is the power spectrum of the element signal when the upper and lower sideband power ratio is 3:1;

[0100] Figure 7 A graph showing the correlation function of single sideband signal reception processing;

[0101] Figure 8 This is a graph of related functions for meta-signal reception and processing. DETAILED DESCRIPTION

[0102] The purpose of the present invention is to address the need for broadcasting dual-frequency signals for low-orbit navigation enhancement, reduce interference with GNSS signals in the same frequency band, and achieve the problem of global all-day dual-frequency signal landing, and propose a low-orbit navigation element signal generation and processing method. In order to make the purpose, technical solution and advantages of the present invention clearer, the present invention is further described in detail with reference to the accompanying drawings.

[0103] The steps of the method for generating a low-orbit navigation element signal disclosed in the present invention are as follows: Figure 1 As shown, the details are as follows:

[0104] (1) Calculation of the center frequency of the meta-signal.

[0105] The two frequency bands are recorded as Band 1 and Band 2. The two frequency points of Band 1, the lower frequency point is called the lower sideband of Band 1, and the center frequency is The high frequency point is called the upper sideband of band 1, and the center frequency is The center frequency of the meta-signal of band 1 is There are two frequency points in band 2. The lower frequency point is called the lower sideband of band 2, and the center frequency is The high frequency point is called the upper sideband of band 2, and the center frequency is The center frequency of the meta-signal of band 2 is For example, is 1520.178MHz, is 1575.42MHz, then the center frequency of the elementary signal of band 1 is

[0106]

[0107] (2) Baseband generation of upper and lower sideband signals.

[0108] For frequency band i, i = 1 or 2, the pseudo code and telegram of the lower sideband signal are generated respectively, and baseband modulation is performed to generate the upper and lower sideband baseband signals corresponding to frequency band 1 and frequency band 2 respectively. The lower sideband baseband signal and the upper sideband baseband signal are both two-level modulation signals, which can be BPSK, BOC, or MCSK modulation signals. The lower sideband baseband signal of frequency band i is recorded as The upper sideband baseband signal of band i is denoted as t represents time.

[0109] The specific generation process is as follows:

[0110] 21) Generate the spreading code sequence of the upper and lower sidebands. Generate the spreading code sequence of the lower sideband and Generate the spreading code sequence for the upper sideband and

[0111] 22) Generate the lower sideband message symbols. Message symbol with upper sideband

[0112] 23) Generate the lower sideband signal baseband. Spreading code sequence for lower sideband Perform baseband modulation to generate the lower sideband baseband signal of frequency band i:

[0113]

[0114] In the formula, represents the lower sideband baseband signal of frequency band i, is the spreading chip width of the lower sideband of band i, Indicates the chip modulation waveform. When the lower sideband signal adopts the BPSK(2) signal, the code rate is 2.046Mcps and the spread spectrum chip width is at this time, is a rectangular chip waveform, defined as:

[0115]

[0116] 24) Upper sideband signal baseband generation. Upper sideband spreading code sequence Perform baseband modulation to generate the upper sideband baseband signal of frequency band i:

[0117]

[0118] In the formula, represents the upper sideband baseband signal of frequency band i, is the spreading chip width of the upper sideband of band i, Indicates the chip modulation waveform. When the upper sideband signal uses the BOC (4,2) signal, the code rate is 2.046Mcps and the spread spectrum chip width is is the square wave subcarrier chip wave of BOC(4,2), defined as:

[0119]

[0120] In the formula, f s =4*1.023MHz is the square wave subcarrier frequency of the BOC(4,2) signal. It can be seen that and It can be the same or different.

[0121] (3) Periodic subcarrier modulation.

[0122] The periodic subcarrier modulation modulates the lower sideband baseband signal Modulate to the lower sideband and convert the upper sideband baseband signal Modulate to the upper sideband. The lower sideband baseband signal of frequency band i is modulated by the periodic subcarrier to obtain the lower sideband signal modulated by the periodic subcarrier, which is specifically:

[0123]

[0124] In the formula, is an imaginary unit, is the lower sideband in-phase periodic subcarrier of band i, with a period of is the orthogonal phase periodic subcarrier of the lower sideband of band i, with a period of The period of the periodic subcarrier is The upper sideband baseband signal of frequency band i is modulated by a periodic subcarrier to obtain an upper sideband signal modulated by a periodic subcarrier, specifically:

[0125]

[0126] In the formula, is the upper sideband in-phase periodic subcarrier of band i, with a period of is the upper sideband orthogonal phase periodic subcarrier of band i, and the period of the periodic subcarrier is also

[0127] Furthermore, the lower sideband of band i has an in-phase periodic subcarrier With orthogonal phase periodic subcarrier In a cycle The inner part is divided into 8 equal parts, expressed as:

[0128]

[0129]

[0130] In the formula, and is the coefficient set of the lower sideband periodic subcarrier, m = 1, 2, ..., 7, these 8 coefficients are expressed as:

[0131]

[0132]

[0133] In the formula, only two subcarrier coefficients are needed and The lower sideband periodic subcarrier can be generated and

[0134] The upper sideband in-phase periodic subcarrier of band i With quadrature phase periodic subcarrier In a cycle The interior is divided into 8 equal parts, expressed as:

[0135]

[0136]

[0137] In the formula, and is the coefficient set of the upper sideband periodic subcarrier, m=1,2,……,7, and these 8 coefficients are respectively expressed as:

[0138]

[0139]

[0140] In the formula, only two subcarrier coefficients are needed and The upper sideband periodic subcarrier can be generated and

[0141] Solve for the lower sideband in-phase periodic subcarrier of band i The lower sideband quadrature phase periodic subcarrier of band i Subcarrier coefficients in the coefficient set of the lower sideband periodic subcarrier and Subcarrier coefficients in the coefficient set of the upper sideband periodic subcarrier and The process is as follows:

[0142] 321) Subcarrier coefficients and and The solution is transformed into the following constrained nonlinear optimization problem

[0143]

[0144]

[0145] In the formula,

[0146]

[0147]

[0148]

[0149]

[0150] In the formula, the constraint equation (Eq.1) can ensure that the baseband signal is a constant envelope, and the constraint equations (Eq.2) and (Eq.3) can ensure that the power ratio of the upper and lower sidebands is The constraint equation (Eq.4) can ensure that the phase difference between the upper and lower sideband signals is Δθ (i) , the constraint equation (Eq.5) can ensure that there is no harmonic signal in the band;

[0151] 322) Set the power ratio of the upper and lower sidebands Set the phase difference Δθ between the upper and lower sideband signals (i) ;

[0152] 323) A numerical optimization algorithm (such as the quasi-Newton method) is used to solve the constrained nonlinear optimization problem and obtain the lower sideband in-phase periodic subcarrier of frequency band i. The lower sideband quadrature phase periodic subcarrier of band i Subcarrier coefficient and Subcarrier coefficient and

[0153] set up Δθ (i) =0, the subcarrier coefficient is solved as The waveform of the lower sideband periodic subcarrier when the upper and lower sideband power ratio is 1:2 is as follows Figure 2 As shown, the upper sideband periodic subcarrier waveform when the upper and lower sideband power ratio is 1:2 is as follows Figure 3 shown.

[0154] The lower sideband in-phase periodic subcarrier of band i The lower sideband quadrature phase periodic subcarrier of band i Subcarrier coefficient and The following update principles are met:

[0155] When you need to turn off the lower sideband signal, and Update to 0;

[0156] When you need to turn off the upper sideband signal, and Update to 0;

[0157] When you need to change the power distribution of the upper and lower sideband signals, reset The power ratio of the subcarrier coefficients is obtained by using a numerical optimization algorithm to solve the constrained nonlinear optimization problem. and Subcarrier coefficient and

[0158] (4) Meta-signal baseband signal generation.

[0159] The signal modulated by the periodic subcarrier generates the baseband signal, which is expressed as:

[0160]

[0161] In the formula, represents the baseband signal of the element signal of frequency band i, Δθ (i) represents the phase difference between the upper and lower sideband signals of frequency band i, and

[0162] Further expressed as:

[0163]

[0164] In the formula, is the in-phase component of the baseband signal of the frequency band i, is the orthogonal component of the baseband signal of the element signal in frequency band i. And:

[0165]

[0166]

[0167] Generate cos(Δθ (i) ) and sin(Δθ (i) ), combined with the upper and lower sideband signals modulated by the periodic subcarrier, the baseband signal generation of the meta-signal can be completed.

[0168] The power spectrum of the baseband signal when the upper and lower sideband power ratio is 1:2 is as follows: Figure 4 The power spectrum of the baseband signal after closing the lower sideband is shown in Figure 5 The power spectrum of the baseband signal when the upper and lower sideband power ratio is 3:1 is shown in Figure 6 shown.

[0169] (5) Meta-signal RF signal generation and broadcasting.

[0170] and The DAC converts it into an analog signal, which is then up-converted, filtered, amplified, and broadcasted via the antenna. At this point, the RF center frequency of the element signal is Generate low-orbit navigation meta-signals and broadcast (i.e., meta-signal RF signals) and broadcast them through the antenna. The meta-signal RF signal is expressed as:

[0171]

[0172] The following reception and processing methods can be used for low-orbit navigation meta-signals:

[0173] The meta-signal is transmitted through space, received by the receiver antenna, amplified by a low-noise amplifier, down-converted, filtered, and converted into a digital intermediate frequency signal after ADC sampling. T sample is the sampling rate, and l represents the lth sampling point.

[0174] 102) The digital intermediate frequency signal is multiplied by the local carrier generated by the receiver, and the carrier is stripped to obtain the received signal after the carrier is stripped. The process is as follows:

[0175]

[0176] 103) The receiver locally generates two possible signals of the baseband signal (i.e., a forward reference signal and a reverse reference signal), q represents the sequence number of the sample value in the forward reference signal and the reverse reference signal, q∈[1,Q].

[0177]

[0178]

[0179] 104) stripping the received signal of the carrier wave and and Parallel correlation is performed respectively, and the correlation values ​​(i.e., the correlation values ​​corresponding to the Q forward reference signals and the correlation values ​​corresponding to the Q reverse reference signals) are obtained as follows:

[0180]

[0181]

[0182] 105) Calculate the maximum amplitude of the correlation values ​​corresponding to the Q forward reference signals The maximum amplitude of the correlation value corresponding to Q reverse reference signals if Then select the forward reference signal As the baseband signal generated locally by the receiver, the capture, tracking, demodulation and other processes are completed according to the traditional receiving and processing flow. Otherwise, the reverse reference signal is selected As the meta-signal baseband signal generated locally by the receiver, the capture, tracking, demodulation and other processes are completed according to the traditional receiving and processing flow.

[0183] For the case where the lower sideband is an NPSK(2) signal, the upper sideband is a BOC(4,2) signal, and the power spectrum ratio of the upper and lower sidebands is 1:2, if the traditional single-sideband signal reception and processing method is used, the correlation functions of the upper and lower sidebands are as follows: Figure 7 As shown in Figure 2, when the upper and lower sidebands are received and processed as a unified element signal, the correlation function is as follows: Figure 8 As shown in Figure 2, it can be seen that the main peak of the correlation function of the meta-signal receiving process is sharper, indicating that higher code tracking accuracy is expected to be achieved.

[0184] The present invention broadcasts low-orbit navigation signals in two frequency bands, each frequency band includes two adjacent frequency points, and each frequency point has one signal. The two signals of the two frequency points of the same frequency band adopt the meta-signal generation method, that is, they are generated as a unified constant envelope signal. When the signal of one frequency point cannot land, by adjusting the signal generation parameters, it can be changed to broadcast only the signal component of the other frequency point, ensuring that there is always a signal broadcast in this frequency band, so as to realize the broadcast of low-orbit dual-frequency navigation signals. When the landing power of the signal of one frequency point is higher than the allowed landing power, and the compatibility with GNSS is difficult to meet, by adjusting the signal generation parameters, the excess power can be allocated to the signal of another frequency point, thereby reducing the interference to the GNSS signal and meeting the compatibility. At the same time, the receiving end can adopt the meta-signal reception and processing method to improve the code tracking measurement accuracy.

[0185] Although the present invention has been disclosed as above with preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make possible changes and modifications to the technical solution of the present invention by using the above disclosed methods and technical contents without departing from the spirit and scope of the present invention. Therefore, any simple modification, equivalent change and modification made to the above embodiments according to the technical essence of the present invention without departing from the content of the technical solution of the present invention shall belong to the protection scope of the technical solution of the present invention. In the absence of conflict, the embodiments of the present application and the technical features in the embodiments can be combined with each other.

[0186] The contents not described in detail in the specification of the present invention belong to the common knowledge of those skilled in the art.

Claims

1. A method for generating low-orbit navigation element signals, characterized in that: include: 1) Calculate the center frequency of the meta-signal to obtain the center frequency of the meta-signal of band 1 and the center frequency of the meta-signal of band 2; wherein, of the two frequency points of band 1, the frequency point with a lower frequency is called the lower sideband of band 1, and the frequency point with a higher frequency is called the upper sideband of band 1; of the two frequency points of band 2, the frequency point with a lower frequency is called the lower sideband of band 2, and the frequency point with a higher frequency is called the upper sideband of band 2; 2) Generate upper and lower sideband baseband signals corresponding to frequency band 1 and frequency band 2 respectively; for frequency band i, i = 1 or 2, the lower sideband baseband signal of frequency band i is recorded as The upper sideband baseband signal of band i is denoted as t represents time; 3) Perform periodic subcarrier modulation to convert the lower sideband baseband signal Modulate to the lower sideband and convert the upper sideband baseband signal Modulate to upper sideband; 4) Generate a meta-signal baseband signal from the upper sideband signal and the lower sideband signal modulated by the periodic subcarrier; 5) Generate and broadcast the meta-signal RF signal using the generated meta-signal baseband signal.

2. A method for generating low-orbit navigation element signals according to claim 1, characterized in that: In step 1), the center frequency of the meta-signal of frequency band 1 and the center frequency of the meta-signal of frequency band 2 are obtained, specifically: The center frequency of the lower sideband of Band 1 is The center frequency of the upper sideband of Band 1 is The center frequency of the meta-signal of band 1 is The center frequency of the lower sideband of Band 2 is The center frequency of the upper sideband of Band 2 is The center frequency of the meta-signal of band 2 is 3. The method for generating low-orbit navigation element signals according to claim 2, characterized in that: In step 2), the upper and lower sideband baseband signals corresponding to frequency band 1 and frequency band 2 are generated, specifically: 21) Generate the spreading code sequence of the upper and lower sidebands; Generate the spreading code sequence of the lower sideband and Generate the spreading code sequence for the upper sideband and 22) Generate the upper and lower sideband message symbols; Generate the lower sideband message symbols Message symbol with upper sideband 23) Generate the lower sideband signal baseband; Spreading code sequence for lower sideband Perform baseband modulation to generate the lower sideband baseband signal of frequency band i: In the formula, represents the lower sideband baseband signal of band i, is the spreading chip width of the lower sideband of band i, represents the chip modulation waveform, is a rectangular chip waveform; a rectangular chip waveform is defined as: 24) Generate the upper sideband signal baseband; Upper sideband spreading code sequence Perform baseband modulation to generate the upper sideband baseband signal of frequency band i: In the formula, represents the upper sideband baseband signal of frequency band i, is the spreading chip width of the upper sideband of band i, represents the chip modulation waveform, It is a rectangular chip waveform.

4. The method for generating low-orbit navigation element signals according to claim 3, characterized in that: In step 3), periodic subcarrier modulation is performed, specifically: The lower sideband baseband signal of frequency band i is modulated by a periodic subcarrier to obtain a lower sideband signal modulated by a periodic subcarrier: In the formula, is an imaginary unit, is the lower sideband in-phase periodic subcarrier of band i, with a period of is the orthogonal phase periodic subcarrier of the lower sideband of band i, with a period of The period of the periodic subcarrier is The upper sideband baseband signal of frequency band i is modulated by a periodic subcarrier to obtain an upper sideband signal modulated by a periodic subcarrier: In the formula, is the upper sideband in-phase periodic subcarrier of band i, with a period of is the upper sideband orthogonal phase periodic subcarrier of band i, and the period of the periodic subcarrier is also 5. A method for generating low-orbit navigation element signals according to claim 4, characterized in that: The lower sideband of the frequency band i is in phase with the periodic subcarrier The lower sideband quadrature phase periodic subcarrier of band i The method for determining is as follows: The lower sideband of band i is in phase with the periodic subcarrier With quadrature phase periodic subcarrier In a cycle The interior is divided into 8 equal parts, expressed as: In the formula, and is the coefficient set of the lower sideband periodic subcarrier, m = 1, 2, ..., 7, these 8 coefficients are expressed as: The upper sideband of band i is in phase with the periodic subcarrier With quadrature phase periodic subcarrier In a cycle The interior is divided into 8 equal parts, expressed as: In the formula, and is the coefficient set of the upper sideband periodic subcarrier, m=1,2,……,7, these 8 coefficients are expressed as:

6. A method for generating low-orbit navigation element signals according to claim 5, characterized in that: The subcarrier coefficients in the coefficient set of the lower sideband periodic subcarrier and Subcarrier coefficients in the coefficient set of the upper sideband periodic subcarrier and Obtained by the following method: 321) Subcarrier coefficients and Subcarrier coefficient and The solution is transformed into a constrained nonlinear optimization problem In the formula, In the formula, the constraint equation Eq.1 is used to ensure that the baseband signal The constant envelope, the constraint equations Eq.2 and Eq.3 are used to ensure that the power ratio of the upper and lower sidebands is The constraint equation Eq.4 is used to ensure that the phase difference between the upper and lower sideband signals is Δθ (i) , the constraint equation Eq.5 is used to ensure that there is no harmonic signal in the band; 322) Set the power ratio of the upper and lower sidebands Set the phase difference Δθ between the upper and lower sideband signals (i) ; 323) A numerical optimization algorithm is used to solve the constrained nonlinear optimization problem and obtain the subcarrier coefficients and Subcarrier coefficient and 7. A method for generating low-orbit navigation element signals according to claim 6, characterized in that: The subcarrier coefficients in the coefficient set of the lower sideband periodic subcarrier and Subcarrier coefficients in the coefficient set of the upper sideband periodic subcarrier and The following update principles are met: When you need to turn off the lower sideband signal, and Update to 0; When you need to turn off the upper sideband signal, and Update to 0; When you need to change the power distribution of the upper and lower sideband signals, reset The power ratio of the subcarrier coefficients is obtained by using a numerical optimization algorithm to solve the constrained nonlinear optimization problem. and Subcarrier coefficient and 8. The method for generating low-orbit navigation element signals according to claim 7, characterized in that: In step 4), the baseband signal is generated as follows: The baseband signal is expressed as: In the formula, represents the baseband signal of the frequency band i, Δθ (i) represents the phase difference between the upper and lower sideband signals of frequency band i, and Further expressed as: In the formula, is the in-phase component of the baseband signal of the frequency band i, is the orthogonal component of the baseband signal of the element signal of frequency band i; and: Generate cos(Δθ (i) ) and sin(Δθ (i) ), combined with the upper and lower sideband signals modulated by the periodic subcarrier, to complete the baseband signal generation of the meta-signal.

9. A method for generating low-orbit navigation element signals according to claim 8, characterized in that: In step 5), the elementary signal radio frequency signal is generated and broadcasted, specifically: and The DAC is converted into an analog signal, up-converted, filtered, amplified, and broadcasted through the antenna; the meta-signal RF signal is generated and broadcasted through the antenna; wherein the RF center frequency of the meta-signal is: The meta-signal RF signal is expressed as:

10. A method for receiving and processing a low-orbit navigation meta-signal, receiving a meta-signal radio frequency signal obtained by a method for generating a low-orbit navigation meta-signal according to any one of claims 2 to 9, characterized in that: The receiving and processing method is as follows: 101) The receiver antenna receives the RF signal after space propagation, amplifies it through a low noise amplifier, down-converts it, filters it, and converts it into a digital intermediate frequency signal after ADC sampling. T sample is the sampling rate, l represents the serial number of the sampling point; 102) The digital intermediate frequency signal is multiplied by the local carrier generated by the receiver, and the carrier is stripped to obtain the received signal after the carrier is stripped. Specifically: 103) The receiver locally generates a forward reference signal of the baseband signal and reverse reference signal Specifically: Wherein, q represents the sequence number of the sample value in the forward reference signal and the reverse reference signal, q∈[1,Q]; 104) The received signal after stripping the carrier and and Parallel correlation is performed respectively to obtain correlation values ​​corresponding to the Q forward reference signals and correlation values ​​corresponding to the Q reverse reference signals, which are specifically: 105) Calculate the maximum amplitude of the correlation values ​​corresponding to the Q forward reference signals The maximum amplitude of the correlation value corresponding to Q reverse reference signals if Then select the forward reference signal in step 103) As the baseband signal generated locally by the receiver, the acquisition, tracking and demodulation process is completed; otherwise, the reverse reference signal in step 103) is selected As the baseband signal generated locally by the receiver, it completes the capture, tracking and demodulation processes.

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