A novel navigation signal modulation method based on nonlinear frequency modulation subcarrier

Abstract

The present application relates to a novel navigation signal modulation method based on a nonlinear frequency modulation subcarrier. The method comprises: constructing a first parameter and a second parameter according to the maximum frequency and initial frequency of the nonlinear frequency modulation signal; constructing an expression of the nonlinear signal according to the first parameter and the second parameter; wherein the phase and frequency of the nonlinear signal are periodic functions that change nonlinearly with time; and multiplying a spread spectrum signal with a subcarrier formed by the nonlinear signal to obtain a navigation signal based on a nonlinear frequency modulation subcarrier. The use of this method can improve the anti-interference capability of the satellite navigation signal system.

Description

Technical Field

[0001] The present application relates to the field of navigation technology, and in particular to a novel navigation signal modulation method based on a nonlinear frequency modulation subcarrier. Background Art

[0002] At present, the typical satellite navigation system signal system is similar, and the transmitted signal is a BPSK signal or a BOC signal. The BOC signal achieves spectrum separation of military and civilian signals by using binary sine and cosine subcarriers, but this signal system also has certain limitations, such as the high amplitude of the autocorrelation function peak, which is prone to false lock during capture and tracking, reducing the reception performance of satellite navigation signals. In the future, with the addition of low-orbit satellite navigation enhancement signals, the number of satellite navigation signals will further increase, which will inevitably bring challenges in compatibility and anti-interference performance, and put forward new requirements for the satellite navigation enhancement signal system. Summary of the invention

[0003] Based on this, it is necessary to provide a new navigation signal modulation method based on nonlinear frequency modulation subcarrier to address the above technical problems.

[0004] A novel navigation signal modulation method based on nonlinear frequency modulation subcarrier, the method comprising:

[0005] Constructing a first parameter and a second parameter according to the maximum frequency and the initial frequency of the nonlinear frequency modulation signal;

[0006] According to the first parameter and the second parameter, construct an expression of a nonlinear signal; wherein the phase and frequency of the nonlinear signal are periodic functions that vary nonlinearly with time;

[0007] The spread spectrum signal is multiplied by a subcarrier formed by the nonlinear signal to obtain a navigation signal based on a nonlinear frequency modulation subcarrier.

[0008] In one embodiment, the first parameter is constructed according to the maximum frequency and the initial frequency of the hyperbolic frequency modulation signal. and the second parameter They are:

[0009] ;

[0010] ;

[0011] in, represents the initial frequency, Indicates the maximum frequency.

[0012] In one embodiment, the method further comprises: constructing an expression of a nonlinear signal according to the first parameter and the second parameter, comprising:

[0013] According to the first parameter and the second parameter, an expression of a nonlinear signal is constructed:

[0014] ;

[0015] in, An expression representing a nonlinear signal, Indicates the cycle.

[0016] In one of the embodiments, the time domain expression of the navigation signal based on the nonlinear frequency modulation subcarrier is:

[0017] ;

[0018] in, is the time domain expression of the navigation signal of the nonlinear frequency modulated subcarrier, represents a spread spectrum signal, represents the subcarrier signal, Represents a symbolic function.

[0019] A novel navigation signal modulation device based on nonlinear frequency modulation subcarrier, the device comprising:

[0020] A parameter setting module, used for constructing a first parameter and a second parameter according to a maximum frequency and an initial frequency of the nonlinear frequency modulation signal;

[0021] A nonlinear signal construction module, used to construct an expression of a nonlinear signal according to the first parameter and the second parameter; wherein the phase and frequency of the nonlinear signal are periodic functions that vary nonlinearly with time;

[0022] The navigation signal generating module is used for multiplying the spread spectrum signal with the subcarrier formed by the nonlinear signal to obtain a navigation signal based on the nonlinear frequency modulation subcarrier.

[0023] In one embodiment, the parameter setting module is further used to construct a first parameter according to the maximum frequency and the initial frequency of the hyperbolic frequency modulation signal. and the second parameter They are:

[0024] ;

[0025] ;

[0026] in, represents the initial frequency, Indicates the maximum frequency.

[0027] In one embodiment, the nonlinear signal construction module is further used to construct an expression of a nonlinear signal according to the first parameter and the second parameter:

[0028] ;

[0029] in, An expression representing a nonlinear signal, Indicates the cycle.

[0030] In one of the embodiments, the time domain expression of the navigation signal based on the nonlinear frequency modulation subcarrier is:

[0031] ;

[0032] in, is the time domain expression of the navigation signal of the nonlinear frequency modulated subcarrier, represents a spread spectrum signal, represents the subcarrier signal, Represents a symbolic function.

[0033] A computer device comprises a memory and a processor, wherein the memory stores a computer program, and when the processor executes the computer program, the following steps are implemented:

[0034] Constructing a first parameter and a second parameter according to the maximum frequency and the initial frequency of the nonlinear frequency modulation signal;

[0035] According to the first parameter and the second parameter, construct an expression of a nonlinear signal; wherein the phase and frequency of the nonlinear signal are periodic functions that vary nonlinearly with time;

[0036] The spread spectrum signal is multiplied by a subcarrier formed by the nonlinear signal to obtain a navigation signal based on a nonlinear frequency modulation subcarrier.

[0037] A computer-readable storage medium stores a computer program, which, when executed by a processor, implements the following steps:

[0038] Constructing a first parameter and a second parameter according to the maximum frequency and the initial frequency of the nonlinear frequency modulation signal;

[0039] According to the first parameter and the second parameter, construct an expression of a nonlinear signal; wherein the phase and frequency of the nonlinear signal are periodic functions that vary nonlinearly with time;

[0040] The spread spectrum signal is multiplied by a subcarrier formed by the nonlinear signal to obtain a navigation signal based on a nonlinear frequency modulation subcarrier.

[0041] Compared with the traditional BOC, the above-mentioned new navigation signal modulation method based on nonlinear frequency modulation subcarrier replaces the original binary sine and cosine subcarrier with a periodic binary nonlinear frequency modulation waveform, changes the signal's autocorrelation function and spectrum characteristics, and thus improves the anti-interference capability of the satellite navigation signal system. BRIEF DESCRIPTION OF THE DRAWINGS

[0042] Figure 1 It is a flowchart of a novel navigation signal modulation method based on nonlinear frequency modulation subcarrier in one embodiment;

[0043] Figure 2 Schematic diagram of theoretical power spectral density function of BOC-nonlinear (0.5, 1, 1, 1ms) and BOC-nonlinear (1, 0.5, 1, 1ms) signals in one embodiment;

[0044] Figure 3 is a comparison diagram of code tracking performance of BOC-nonlinear (0.5, 1, 1, 1ms), BOC-nonlinear (1, 0.5, 1, 1ms) signals and traditional satellite navigation signals BOC (1, 1) and BPSK in one embodiment;

[0045] Figure 4 is a comparison diagram of BOC-nonlinear (0.5, 1, 1, 1ms), BOC-nonlinear (1, 0.5, 1, 1ms) signals and traditional satellite navigation signals BOC (1, 1) and BPSK in terms of multipath suppression performance in one embodiment;

[0046] Figure 5 is a comparison diagram of BOC-nonlinear (0.5, 1, 1, 1ms), BOC-nonlinear (1, 0.5, 1, 1ms) signals and traditional satellite navigation signals BOC (1, 1) and BPSK in terms of anti-matching spectrum interference performance in one embodiment;

[0047] Figure 6 A comparison diagram of BOC-nonlinear (0.5, 1, 1, 1ms), BOC-nonlinear (1, 0.5, 1, 1ms) signals and traditional satellite navigation signals BOC (1, 1) and BPSK in terms of anti-narrowband interference performance in an embodiment;

[0048] Figure 7is a comparison diagram of BOC-nonlinear (0.5, 1, 1, 1ms), BOC-nonlinear (1, 0.5, 1, 1ms) signals and traditional satellite navigation signals BOC (1, 1) and BPSK in terms of anti-band-limited white noise interference performance in one embodiment;

[0049] Figure 8 is a structural block diagram of a novel navigation signal modulation device based on nonlinear frequency modulation subcarrier in one embodiment;

[0050] Fig. 9 FIG. 4 is a diagram showing the internal structure of a computer device in one embodiment. DETAILED DESCRIPTION

[0051] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0052] In one embodiment, Figure 1 As shown, a novel navigation signal modulation method based on nonlinear frequency modulation subcarrier is provided, comprising the following steps:

[0053] Step 102: construct a first parameter and a second parameter according to the maximum frequency and the initial frequency of the nonlinear frequency modulation signal.

[0054] Step 104: construct an expression of the nonlinear signal according to the first parameter and the second parameter.

[0055] A nonlinear signal is a periodic function whose phase and frequency vary nonlinearly with time.

[0056] Step 106: multiply the spread spectrum signal and the subcarrier formed by the nonlinear signal to obtain a navigation signal based on the nonlinear frequency modulation subcarrier.

[0057] In the above-mentioned new navigation signal modulation method based on nonlinear frequency modulation subcarrier, compared with the traditional BOC, the subcarrier uses a periodic binary nonlinear frequency modulation waveform to replace the original binary sine and cosine subcarrier, changing the signal's autocorrelation function and spectral characteristics, thereby improving the anti-interference ability of the satellite navigation signal system.

[0058] In one embodiment, the first parameter is constructed according to the maximum frequency and the initial frequency of the nonlinear frequency modulation signal. and the second parameter They are:

[0059] ;

[0060] ;

[0061] in, represents the initial frequency, Indicates the maximum frequency.

[0062] In another embodiment, according to the first parameter and the second parameter, an expression for constructing a nonlinear signal is:

[0063] ;

[0064] in, An expression representing a nonlinear signal, Indicates the cycle.

[0065] In the traditional BOC modulation technology, the BOC signal constructed by multiplying the spread spectrum code signal with the binary sine and cosine subcarrier signal successfully moves the single main lobe non-split spectrum of the spread spectrum code signal to both sides of the center frequency, thereby forming a split spectrum modulation signal. signal, where is the subcarrier frequency, is the spreading code rate, and its time domain expression is:

[0066] ;

[0067] Where: ——Spread spectrum code signal, ——Symbolic function, - subcarrier frequency, .

[0068] In the present invention, the nonlinear frequency modulation signal is a frequency modulation signal whose instantaneous frequency changes with time in accordance with the law of nonlinear type. This signal has a wide range of applications in the fields of radar, sonar, communication, etc., especially in the occasions where high-resolution ranging and speed measurement are required. Similar to BOC modulation, the spread spectrum code signal is multiplied by the binary periodic subcarrier to construct a binary offset nonlinear carrier modulation based on nonlinear subcarrier, which is denoted as , where the initial frequency of the nonlinear subcarrier is , the bandwidth of the nonlinear subcarrier is , the spreading code rate is , T is the period of the nonlinear subcarrier.

[0069] In one of the embodiments, the time domain expression of the navigation signal based on the nonlinear frequency modulation subcarrier is:

[0070] ;

[0071] in, is the time domain expression of the navigation signal of the nonlinear frequency modulated subcarrier, represents a spread spectrum signal, represents the subcarrier signal, Represents a sign function. In this embodiment, the waveform change and performance improvement are achieved by changing the implementation method of SC(t). Compared with the traditional BOC signal in which SC(t) is a binary sine and cosine, the SC(t) here becomes a binary nonlinear signal. Within period T, the subcarrier is a continuous binary wave, that is, the waveform after the nonlinear frequency modulation signal is binarized. After multiplying the subcarrier and the spread spectrum code signal, a BOC-nonlinear signal is obtained. Compared with traditional BOC modulation, BOC-nonlinear modulation has a binary subcarrier whose frequency changes with time in each period, which changes the characteristics of the spread spectrum code signal in the time domain and frequency domain.

[0072] The above embodiment provides a specific form of a novel navigation signal modulation method based on a nonlinear frequency modulation subcarrier, and its performance is analyzed below.

[0073] Figure 2 It is a schematic diagram of the theoretical power spectral density function of BOC-nonlinear (0.5, 1, 1, 1ms) and BOC-nonlinear (1, 0.5, 1, 1ms) signals;

[0074] Among the four parameters of the signal, a determines the starting frequency of the subcarrier, b determines the bandwidth of the subcarrier, n determines the pseudo code rate of the signal, and T determines the period of the subcarrier. The values ​​of a and b largely determine the time-frequency domain characteristics of the signal.

[0075] Figure 3 This is a comparison chart of the code tracking performance of BOC-nonlinear (0.5, 1, 1, 1ms), BOC-nonlinear (1, 0.5, 1, 1ms) signals and the traditional satellite navigation signals BOC (1, 1) and BPSK;

[0076] When there is no interference, and the signal receiving loop and the signal carrier-to-noise ratio parameters are constant, for different signal systems, the spread spectrum code tracking measurement accuracy is determined by the integral of the following formula, which is expressed as:

[0077] ;

[0078] The code tracking performance of the signal system is characterized by Gabor bandwidth. Assuming that the front-end filter bandwidth is 1~20MHz, it can be seen that BOC-nonlinear(1,0.5,1,1ms) has the best tracking performance. Taking the front-end bandwidth of 10MHz as an example, its tracking performance is improved by 17.46% compared with BOCc(1,1). Compared with BOCc(1,1), its performance in code tracking has greater potential.

[0079] Figure 4 Used to illustrate the anti-multipath envelope performance of BOC-nonlinear signals.

[0080] In the actual environment, multipath signals are unavoidable. Multipath refers to the phenomenon that the signal reaches the receiving end through multiple paths from the transmitter. The receiver will receive both the direct signal and the multipath signal at the same time. The multipath signal will cause the amplitude and phase of the received signal to change, thus causing carrier and pseudo-range measurement errors. To simplify the analysis, the assumption of one multipath signal is generally used in the navigation signal performance evaluation, and the amplitude ratio of one signal to the direct signal is defined as The delay difference is defined as , then the baseband signal can be expressed as

[0081] ;

[0082] in is the complex envelope of the transmitted signal, is the propagation delay of the direct signal, is the amplitude of the direct signal, is the phase of the direct signal. The multipath signal mainly causes the zero-crossing point offset of the discriminator curve. After receiving, processing and calculation, the error caused by the multipath signal can be obtained. When the correlator interval Approaching 0, and The relationship can be approximately expressed as

[0083] ;

[0084] in, is the delay of the multipath signal relative to the direct signal; is the multipath direct reach ratio; is the normalized power spectral density of each signal within the transmission bandwidth, is the signal bandwidth.

[0085] Based on the multipath error envelope, the average multipath error envelope can be used to make a more intuitive evaluation of the multipath error. Its expression is:

[0086] ;

[0087] In the formula, The direct multipath phase difference is 0 degrees, and the multipath delay is The multipath error, The direct multipath phase difference is 180 degrees, and the multipath delay is multipath error.

[0088] The simulation analyzes the anti-multipath performance of BOC-nonlinear signals. The multipath is assumed to be a multipath signal and the amplitude ratio of the multipath signal to the direct signal is -6dB. The front-end bandwidth is set to 10MHz and the correlation interval is 0.1 code. The average multipath error envelope is simulated and analyzed. As a reference analysis, the anti-multipath performance of BOCs(1,1), BOCc(1,1), BPSK and other signals are added for comparison.

[0089] When the front-end bandwidth is 10MHz and the correlation interval is 0.1 chip, the hyperbolic frequency modulation signals BOC-nonlinear (0.5,1,1,1ms) and BOC-nonlinear (1,0.5,1,1ms) are better than BOCs (1,1) in the scenario of 0 to 500 meters, and are only slightly lower than the BOCc (1,1) signal in some multipath delay scenarios. The total multipath envelope area of ​​BOC-nonlinear (0.5,1,1,1ms) is 7.99% lower than that of BOCc (1,1) signal. Overall, the anti-multipath performance is better than that of the traditional BOC signal.

[0090] Figure 5 , Figure 6 and Figure 7 In terms of interference performance, the comparison chart of BOC-nonlinear (0.5, 1, 1, 1ms), BOC-nonlinear (1, 0.5, 1, 1ms) signals and traditional satellite navigation signals BOC (1, 1) and BPSK;

[0091] In the evaluation of satellite navigation signal anti-interference performance, virtual white noise is usually used to calculate the carrier-to-noise ratio based on the influence of equivalent thermal noise and non-white noise to evaluate the quality of GNSS signal anti-interference performance. The carrier-to-noise ratio is defined as the equivalent carrier-to-noise ratio. Its expression is:

[0092] ;

[0093] in is the quality factor for interference immunity, is the spreading code rate, is the expected signal power received, is the received interference signal power. The higher the equivalent carrier-to-noise ratio, the better the anti-interference performance.

[0094] The calculation of equivalent carrier-to-noise ratio is relatively complicated. To simplify the analysis, the anti-interference quality factor can also be used to characterize the anti-interference performance of the signal. Assuming that the front-end filter of the receiver is an ideal low-pass filter, the expression of the anti-interference quality factor is:

[0095] ;

[0096] in is the front-end filter bandwidth of the signal.

[0097] Common interference sources include narrowband interference, matched spectrum interference, and band-limited white noise interference. When the interference source is narrowband interference, the interference signal can be equivalent to an impulse function, and the signal's quality factor for narrowband interference resistance is

[0098] ;

[0099] When the interference source is matching spectrum interference, the interference signal has the same power spectrum as the desired signal, such as multiple access interference or an interference waveform with a spectrum similar to the original signal, then the signal's anti-matching interference quality factor is

[0100] ;

[0101] When the interference source is band-limited white noise interference, the interference signal power spectrum is flat and the center frequency is , and the frequency range is , the power spectral density is , then the signal's anti-matching interference quality factor is

[0102]

[0103] The larger the value of the anti-interference quality factor, the higher the equivalent carrier-to-noise ratio and the better the anti-interference performance. Therefore, the larger the value of the anti-interference factor, the better.

[0104] Figure 5 , Figure 6 , Figure 7 In the case of non-coherent early-subtraction-late amplitude phase detection, the front-end filter bandwidth is 1~99MHz, and the center frequency of the narrowband interference is the center frequency of the signal main lobe. The performance comparison of anti-narrowband interference, anti-matching spectrum interference and anti-band-limited interference shows that the quality factor of anti-matching spectrum interference of BOC-nonlinear (0.5,1,1,1ms) and BOC-nonlinear (1,0.5,1,1ms) is better than that of traditional BOC(1,1) signal and BPSK(2). In the case of front-end bandwidth of 20MHz, the anti-matching spectrum interference performance of BOC-nonlinear(0.5,1,1,1ms) is improved by 32.11% compared with BOCc(1,1).

[0105] It can be seen that BOC-nonlinear (0.5,1,1,1ms) has the best anti-narrowband interference performance, and its advantage is obvious, followed by BOC-nonlinear (1,0.5,1,1ms). When the front-end bandwidth is 20MHz, the anti-narrowband interference performance of BOC-nonlinear (0.5,1,1,1ms) is 14.73% higher than that of BOCc (1,1).

[0106] The anti-interference capabilities of BOC- nonlinear (0.5,1,1,1ms) and BOC- nonlinear (1,0.5,1,1ms) are similar to those of BOCc(1,1) and better than those of BOCs(1,1).

[0107] It should be understood that although Figure 1 The steps in the flowchart are shown in sequence as indicated by the arrows, but these steps are not necessarily executed in the order indicated by the arrows. Unless otherwise specified in this document, there is no strict order restriction for the execution of these steps, and these steps can be executed in other orders. Moreover, Figure 1 At least part of the steps may include multiple sub-steps or multiple stages. These sub-steps or stages are not necessarily executed at the same time, but can be executed at different times. The execution order of these sub-steps or stages is not necessarily sequential, but can be executed in turn or alternately with other steps or at least part of the sub-steps or stages of other steps.

[0108] In one embodiment, Figure 8 As shown, a novel navigation signal modulation device based on nonlinear frequency modulation subcarrier is provided, comprising: a parameter setting module 802, a nonlinear signal construction module 804 and a navigation signal generation module 806, wherein:

[0109] A parameter setting module 802 is used to construct a first parameter and a second parameter according to the maximum frequency and the initial frequency of the hyperbolic frequency modulation signal;

[0110] A nonlinear signal construction module 804 is used to construct an expression of a nonlinear signal according to the first parameter and the second parameter; wherein the expression of the nonlinear signal is a periodic function of frequency varying with time;

[0111] The navigation signal generating module 806 is used to multiply the spread spectrum signal with the subcarrier of the nonlinear signal to obtain a navigation signal based on a periodic binary hyperbolic frequency modulation subcarrier.

[0112] In one embodiment, the parameter setting module 802 is further configured to construct a first parameter according to the maximum frequency and the initial frequency of the hyperbolic frequency modulation signal. and the second parameter They are:

[0113] ;

[0114] ;

[0115] in, represents the initial frequency, Indicates the maximum frequency.

[0116] In one embodiment, the nonlinear signal construction module 804 is further configured to construct an expression of a nonlinear signal according to the first parameter and the second parameter:

[0117] ;

[0118] in, An expression representing a nonlinear signal, Indicates the cycle.

[0119] In one of the embodiments, the time domain expression of the navigation signal based on the nonlinear frequency modulation subcarrier is:

[0120] ;

[0121] in, is the time domain expression of the navigation signal of the nonlinear frequency modulated subcarrier, represents a spread spectrum signal, represents the subcarrier signal, Represents a symbolic function.

[0122] For the specific definition of the novel navigation signal modulation device based on nonlinear frequency modulation subcarrier, please refer to the definition of the novel navigation signal modulation method based on nonlinear frequency modulation subcarrier in the above text, which will not be repeated here. Each module in the above novel navigation signal modulation device based on nonlinear frequency modulation subcarrier can be implemented in whole or in part by software, hardware and a combination thereof. Each of the above modules can be embedded in or independent of the processor in the computer device in the form of hardware, or can be stored in the memory in the computer device in the form of software, so that the processor can call and execute the operations corresponding to each of the above modules.

[0123] In one embodiment, a computer device is provided. The computer device may be a terminal, and its internal structure diagram may be as follows: Fig. 9As shown. The computer device includes a processor, a memory, a network interface, a display screen and an input device connected through a system bus. Among them, the processor of the computer device is used to provide computing and control capabilities. The memory of the computer device includes a non-volatile storage medium and an internal memory. The non-volatile storage medium stores an operating system and a computer program. The internal memory provides an environment for the operation of the operating system and the computer program in the non-volatile storage medium. The network interface of the computer device is used to communicate with an external terminal through a network connection. When the computer program is executed by the processor, a new navigation signal modulation method based on nonlinear frequency modulation subcarrier is implemented. The display screen of the computer device can be a liquid crystal display screen or an electronic ink display screen, and the input device of the computer device can be a touch layer covered on the display screen, or a key, trackball or touchpad set on the computer device shell, or an external keyboard, touchpad or mouse, etc.

[0124] Those skilled in the art will understand that Fig. 9 The structure shown in the figure is only a block diagram of a part of the structure related to the solution of the present application, and does not constitute a limitation on the computer device to which the solution of the present application is applied. The specific computer device may include more or fewer components than those shown in the figure, or combine certain components, or have a different arrangement of components.

[0125] In one embodiment, a computer device is provided, including a memory and a processor, wherein the memory stores a computer program, and the processor implements the steps of the method in the above embodiment when executing the computer program.

[0126] In one embodiment, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a processor, the steps of the method in the above embodiment are implemented.

[0127] Those of ordinary skill in the art can understand that all or part of the processes in the above-mentioned embodiment methods can be implemented by instructing the relevant hardware through a computer program, and the computer program can be stored in a non-volatile computer-readable storage medium. When the computer program is executed, it can include the processes of the embodiments of the above-mentioned methods. Among them, any reference to memory, storage, database or other media used in the embodiments provided in this application may include non-volatile and / or volatile memory. Non-volatile memory may include read-only memory (ROM), programmable ROM (PROM), electrically programmable ROM (EPROM), electrically erasable programmable ROM (EEPROM) or flash memory. Volatile memory may include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in many forms, such as static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double data rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous link (Synchlink) DRAM (SLDRAM), memory bus (Rambus) direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM), etc.

[0128] The technical features of the above embodiments may be combined arbitrarily. To make the description concise, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0129] The above-described embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention. It should be pointed out that, for a person of ordinary skill in the art, several modifications and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the attached claims.

Claims

1. A novel navigation signal modulation method based on nonlinear frequency modulation subcarrier, characterized in that: The method comprises: Constructing a first parameter and a second parameter according to the maximum frequency and the initial frequency of the nonlinear frequency modulation signal; According to the first parameter and the second parameter, construct an expression of a nonlinear signal; wherein the phase and frequency of the nonlinear signal are periodic functions that vary nonlinearly with time; Multiplying the spread spectrum signal with the subcarrier formed by the nonlinear signal to obtain a navigation signal based on the nonlinear frequency modulation subcarrier; According to the maximum frequency and the minimum frequency of the hyperbolic frequency modulation signal, the first parameter and the second parameter are constructed, including: According to the maximum frequency and initial frequency of the hyperbolic frequency modulation signal, the first parameter is constructed. and the second parameter They are: ； ； in, represents the initial frequency, Indicates the maximum frequency; According to the first parameter and the second parameter, constructing an expression of a nonlinear signal includes: According to the first parameter and the second parameter, an expression of a nonlinear signal is constructed: ； in, An expression representing a nonlinear signal, Indicates the cycle.

2. The method according to claim 1, characterized in that The time domain expression of the navigation signal based on nonlinear frequency modulation subcarrier is: ； in, is the time domain expression of the navigation signal of the nonlinear frequency modulated subcarrier, represents a spread spectrum signal, represents the subcarrier signal, Represents a symbolic function.

Images