4fsk non-coherent demodulation method and system based on chirp synchronization sequence

Abstract

The application belongs to the technical field of wireless communication, and provides a 4FSK non-coherent demodulation method and system based on a Chirp synchronization sequence. The method deeply integrates the Chirp synchronization sequence and the 4FSK non-coherent demodulation structure, uses a linear frequency modulation signal as a frame synchronization header, and adopts quaternary frequency shift keying modulation in the data segment of the same communication frame, thereby expanding the application scenario of the Chirp to the non-coherent demodulation field and optimizing the parameters to match the 4FSK system. Through the collaborative design of the synchronization sequence and the demodulation parameters, the application realizes the integrated optimization of "synchronization-demodulation", and improves the synchronization reliability and demodulation performance of the system in a complex channel with low signal-to-noise ratio and high dynamics.

Description

Technical Field

[0001] This application belongs to the field of wireless communication technology, and in particular relates to a 4FSK incoherent demodulation method and system based on Chirp synchronization sequence. Background Technology

[0002] 4FSK (Quadruple Frequency Shift Keying), as a digital modulation method, is widely used in short-range wireless communication due to its simplicity and good noise immunity. Its noncoherent demodulation structure does not require precise carrier synchronization; signal decision can be completed by detecting frequency components within a symbol period. Its hardware implementation complexity is low, making it suitable for resource-constrained terminal devices (such as IoT sensors and wireless remote controls). Currently, 4FSK incoherent demodulation systems primarily use traditional sequences such as PN codes and Barker codes for synchronization. Meanwhile, Chirp (linear frequency modulation) sequences, due to their linear frequency-time variation, have been used in synchronization and spread spectrum communication in standards such as IEEE 802.15.4a. In recent years, techniques combining Chirp and MFSK have emerged, such as demodulating MFSK symbols by outputting the correlation peak position using a Chirp pulse compressor. Furthermore, Chirp spread spectrum incoherent demodulation methods based on fractional Fourier transform have been proposed to reduce the impact of Doppler shift. However, existing technologies still have the following shortcomings: (1) The synchronization and demodulation parameters are designed independently, lacking coordinated optimization. In existing solutions, whether using traditional PN code synchronization or Chirp synchronization, the parameters of the synchronization sequence (frequency range, duration, modulation frequency, etc.) and the parameters of the 4FSK data symbols are designed independently. Additional calibration is required after synchronization before entering the demodulation process, increasing system latency and resource consumption. Even existing technologies combining Chirp and MFSK simply use Chirp as a demodulation tool, without addressing the coordinated design of parameters between the synchronization sequence and data demodulation.

[0003] (2) Weak resistance to Doppler frequency deviation In high-speed mobile scenarios (such as drones and vehicle-to-everything (V2X) communication, Doppler frequency offset can cause frequency detection deviations in 4FSK. Since noncoherent demodulation itself lacks a frequency offset compensation mechanism, this further degrades performance. When the frequency offset increases to 0.3 times the 4FSK frequency spacing, demodulation performance drops by more than 4 dB, severely impacting demodulation performance.

[0004] (3) Synchronization accuracy and demodulation window alignment depend on additional processing There is no natural parameter correspondence between the timing estimate output by the existing Chirp synchronization method and the data demodulation window. Additional interpolation or resampling is required to convert the synchronization result into the starting position of the demodulation window. Summary of the Invention

[0005] In view of this, this application aims to propose a 4FSK incoherent demodulation method and system based on Chirp synchronization sequences to solve at least one of the above problems.

[0006] To achieve the above objectives, the technical solution of this application is implemented as follows: In a first aspect, this application provides a 4FSK incoherent demodulation method based on Chirp synchronization sequences, including: The start frequency, end frequency, modulation frequency, and duration of the Chirp synchronization sequence are jointly determined based on the equally spaced 4FSK carrier frequencies and symbol periods, so that the Chirp scanning band covers the 4FSK carrier frequencies and has a frequency margin of a preset carrier frequency interval at both ends, so as to generate a communication frame that sequentially contains the Chirp synchronization sequence, spacer, and 4FSK data symbols. By performing up-scanning and down-scanning frequency domain correlation on the Chirp synchronization sequence in the received communication frame, timing estimates and frequency offset estimates are obtained. The timing estimates are used to determine the detection window for each 4FSK data symbol, and each carrier frequency is compensated according to the frequency offset estimates. The in-phase correlation and quadrature correlation quantities corresponding to the four carrier frequencies after compensation are calculated separately in each detection window. The energy value is obtained based on the sum of their squares, and the carrier frequency corresponding to the maximum energy value is determined as the transmitted symbol.

[0007] Secondly, based on the same inventive concept, this application also provides a 4FSK noncoherent demodulation system based on Chirp synchronization sequence, including a parameter coordination configuration module, a frame generation module, a receiving front end, a Chirp synchronization module, a frequency offset compensation module, a window control module, a 4FSK noncoherent demodulation module, and an output module. The parameter coordination configuration module is used to jointly configure the Chirp synchronization sequence according to four equally spaced 4FSK carrier frequencies and symbol periods, so that its scanning frequency band covers the four carrier frequencies and has frequency margin, the duration is an integer multiple of the symbol period, and the frequency change is 4 times the carrier frequency interval. The frame generation module is used to generate communication frames that sequentially contain a Chirp synchronization sequence, a spacer, and 4FSK data symbols. The Chirp synchronization module is used to perform up-sweep and down-sweep frequency domain correlation on the baseband signal output from the receiving front end and output timing estimate and frequency offset estimate. The frequency offset compensation module is used to compensate for the four 4FSK carrier frequencies; The window control module is used to establish a 4FSK detection window based on the timing estimate; The 4FSK incoherent demodulation module is used to calculate the energy of four in-phase and quadrature correlation channels and complete the maximum energy decision. The output module is used to output demodulated data.

[0008] Thirdly, based on the same inventive concept, this application also provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the method described in the first aspect.

[0009] Fourthly, based on the same inventive concept, this application also provides a non-transitory computer-readable storage medium, wherein the non-transitory computer-readable storage medium stores computer instructions for causing the computer to perform the method as described in the first aspect.

[0010] Compared with existing technologies, the 4FSK incoherent demodulation method and system based on Chirp synchronization sequences described in this application have the following advantages: This application achieves deep integration of Chirp synchronization sequence and 4FSK noncoherent demodulation through parameter co-design of Chirp synchronization sequence and 4FSK, filling the gap of low synchronization reliability in traditional 4FSK systems. Through parameter co-design and dynamic compensation mechanism, the integrated performance of synchronization and demodulation is optimized, especially in the environments of anti-Doppler frequency offset and low signal-to-noise ratio, thereby improving the synchronization reliability and demodulation performance of the system in complex channels such as low signal-to-noise ratio and high dynamics. Attached Figure Description

[0011] The accompanying drawings, which form part of this application, are used to provide a further understanding of this application. The illustrative embodiments and descriptions of this application are used to explain this application and do not constitute an undue limitation of this application. In the drawings: Figure 1 This is a schematic diagram of the Chirp-4FSK frame structure as described in the embodiments of this application; Figure 2 This is a flowchart of the Chirp synchronization algorithm described in the embodiments of this application; Figure 3 This is a graph showing the frequency offset resistance of 4FSK noncoherent demodulation as described in the embodiments of this application. Figure 4 This is a frequency offset immunity curve of the Chirp-4FSK system described in the embodiments of this application; Figure 5 This is a timing estimation performance curve of the Chirp-4FSK system described in the embodiments of this application; Figure 6 This is a block diagram of the system transmitter structure described in the embodiments of this application; Figure 7 This is a block diagram of the system receiver structure described in the embodiments of this application; Figure 8This is a schematic diagram of the hardware structure of the electronic device described in an embodiment of this application. Detailed Implementation

[0012] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with specific embodiments and the accompanying drawings.

[0013] It should be noted that, unless otherwise defined, the technical or scientific terms used in the embodiments of this application should have the ordinary meaning understood by one of ordinary skill in the art to which this application pertains. The terms "first," "second," and similar terms used in the embodiments of this application do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Terms such as "comprising" or "including" mean that the element or object preceding the word encompasses the elements or objects listed after the word and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are only used to indicate relative positional relationships; when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0014] The embodiments of this application are described in detail below with reference to the accompanying drawings.

[0015] The core of this application is the deep integration of the Chirp synchronization sequence and the 4FSK incoherent demodulation structure. It uses a linear frequency modulation (Chirp) signal as the frame synchronization header and employs quaternary frequency shift keying (4FSK) modulation in the data segment of the same communication frame. Through the coordinated design of the synchronization sequence and demodulation parameters, integrated optimization of "synchronization-demodulation" is achieved. The specific scheme is as follows: Example 1: Communication Frame Structure Design and Parameter Co-design of Chirp Sequence and 4FSK like Figure 1 As shown, a communication frame sequentially includes a Chirp synchronization sequence, a spacer, and 4FSK data symbols. The Chirp synchronization sequence serves as the frame preamble, and its sampling number is denoted as... The duration is recorded as The separator represents an idle time slot, with a duration of [duration missing]. Used to isolate synchronization sequences from data symbols to avoid spectral aliasing; the data segment contains 4FSK symbols, each symbol having a duration of Each 4FSK symbol carries two bits, and the four bit combinations 00, 01, 10, and 11 are mapped to... , , , The resulting carrier frequency set is .

[0016] Chirp synchronization sequences can be up-sweep sequences, down-sweep sequences, or a combination of both in a predetermined order. Taking baseband representation as an example, the chirp signal can be expressed as: , ; In the formula, The center frequency of the Chirp baseband signal is [value], and the instantaneous frequency is [value]. : At that time, the instantaneous frequency equals This corresponds to the start frequency of the Chirp sequence; At that time, the instantaneous frequency equals This corresponds to the Chirp sequence termination frequency; For frequency modulation ( For upscan frequency, (for the downsweep frequency) For amplitude, For the initial phase, ,by It expands symmetrically to the left and right from the center.

[0017] 1) Frequency parameter coordination Frequency range integration design: The frequency scanning range of the Chirp sequence covers the frequency range of the 4FSK carrier set. Let the minimum frequency in the 4FSK carrier set be... The maximum frequency is The frequency interval is Chirp sequence start frequency Termination frequency ; It needs to fully cover the 4FSK frequency band, with reserves on both the left and right sides. Frequency margin.

[0018] in, ; ; ; The center frequency of the Chirp baseband signal is equal to the center of the 4FSK baseband carrier frequency range.

[0019] Subtracting the two equations gives the bandwidth: ; The actual bandwidth is: ,therefore .

[0020] coefficient This refers to the single-sided frequency margin coefficient of the Chirp synchronization sequence when extended outward relative to the 4FSK carrier frequency range. Too small a margin will result in insufficient frequency headroom, and reduced resistance to Doppler and local oscillator frequencies. Excessive bandwidth consumption can lead to excessive Chirp bandwidth and increased hardware overhead. A value range of 0.2 to 0.5 is considered the optimal range for engineering applications, representing a trade-off between frequency offset resistance and hardware bandwidth overhead. Based on this range, we can obtain... The typical value is 4.

[0021] Physical significance: The frequency scan of the Chirp sequence covers the entire carrier frequency range of 4FSK with a certain margin, providing a more stable reference for subsequent frequency detection, ensuring that the frequency offset estimated during the synchronization stage can represent the actual frequency offset of each carrier frequency in 4FSK, so that the frequency offset estimation can be seamlessly used for carrier compensation in subsequent data demodulation. The lower limit is determined by the Cramer-Rao lower limit (CRLB) of the frequency offset estimation, and the upper limit is determined by the system bandwidth efficiency constraint.

[0022] Frequency modulation and carrier frequency spacing matching: frequency modulation of Chirp sequences Matching the carrier frequency spacing of 4FSK, the modulation frequency ,in, For matching coefficients, The typical value is 4.

[0023] Physical meaning: This constraint guarantees the chirp's full duration. Within this framework, the total sweep bandwidth of Chirp maintains a fixed multiple relationship with the 4FSK carrier frequency interval, ensuring that the time-frequency grid of Chirp is aligned with the demodulation grid of 4FSK without requiring additional time-frequency conversion. This applies to any sub-time segment. Within, the instantaneous frequency change of Chirp is It changes linearly with the length of the time segment.

[0024] 2) Time parameter coordination Duration of the Chirp sequence The symbol period should be consistent with that of a single 4FSK data symbol. Matching, there is a specific proportional relationship. ,in, This is the proportionality coefficient.

[0025] Physical meaning: This constraint ensures that there is an integer multiple of the symbol period between the start time of the first symbol of the Chirp sequence's ending 4FSK, so that the timing estimate of the synchronous capture can be directly used as the starting point of the 4FSK demodulation window.

[0026] Example 2: Chirp Sequence Synchronization Method Based on Coordination Parameters All signal expressions in this application are intermediate frequency baseband signals obtained by down-conversion of radio frequency signals; This refers to the baseband domain spectrum shift, not the radio frequency carrier. The transmitted chirp sequence and the local reference template have completely identical baseband center shift terms, ensuring correlation matching.

[0027] 1) Signal Definition: The RF front-end of the receiver performs filtering, low-noise amplification, and down-conversion on the received signal to obtain the baseband sampling sequence, which includes time delay. and frequency offset The received baseband signal is: ; In the formula, In order to send a signal, For noise. The Chirp synchronization module pre-stores an up-scanning reference sequence with parameters consistent with the transmitter. and downscan frequency reference sequence The reference sequence can be represented as: ; ; Calculate the FFT based on the upper and lower frequency sweep reference sequences: ; ; .

[0028] like Figure 2 As shown, this embodiment employs a Chirp signal synchronization algorithm based on FFT frequency domain correlation, specifically including the following steps: S101. The baseband sampling sequence is sent to the sliding window buffer unit. For the received signal... According to the sliding step size (like ) Frame division, length of each frame Pad with zeros to the length of the FFT. ,get .

[0029] S102, For the current window sequence Perform a fast Fourier transform to obtain The specific formula is as follows: ; S103, will Multiply by the frequency domain conjugates of the up-scan and down-scan reference sequences, respectively. The up-scan correlation is: ; The frequency-dependent features are: ; In the formula, and These represent the local up-scanning frequency reference sequence and down-scanning frequency reference sequence after FFT, respectively. Frequency domain value of each frequency unit; To take the conjugate of the corresponding complex frequency domain value; and These represent the frequency domain correlation products obtained by performing conjugate multiplication of the received window spectrum with the upper and lower frequency sweep reference spectra, respectively.

[0030] S104. Perform inverse fast Fourier transform on each, and calculate the modulus squared correlation power: ; ; ; ; In the formula, This indicates the inverse fast Fourier transform operation; and These represent the discrete time-domain correlation sequences obtained by inverse transformation of the frequency domain correlation products of the upper and lower sweep frequencies, respectively. Represents the discrete position index of the related sequence; and These represent the correlation sequences of the up-scan and down-scan frequencies at the 1st and 2nd frequencies, respectively. The relevant power at each location; This represents the square of the modulus of the result related to the complex number.

[0031] S105. Detect the peak value and peak position of the two related power channels. If the peak value does not reach the preset threshold (the preset threshold can be flexibly set according to the actual situation; this embodiment does not specify a specific threshold value), the window will slide according to the step size. Slide the curve and continue calculating the frequency domain correlation value; if the peak values ​​of the two paths reach the preset threshold, then proceed to parameter estimation, the formula of which is as follows: , ; , ; In the formula, This represents the peak position index of the frequency-sweep correlated power sequence; Indicates the peak position index of the downsweep frequency-correlated power sequence; Indicates index at discrete location Within the range of values, find the position where the relevant power reaches its maximum value; and These represent the peak values ​​of the correlation power sequences for the up-sweep and down-sweep frequencies, respectively.

[0032] S106. Perform parabolic interpolation using the peak position and adjacent sampling points. The interpolation positions for the upper and lower frequency sweep peaks are as follows: ; ; Timely estimate and frequency offset estimates It can be obtained according to the following formula: ; ; In the formula, and These represent the interpolation positions based on the positions of the correlation peaks from the upper and lower sweep frequencies, respectively. This indicates the sampling delay between the starting point of the current sliding window and the starting point of the receiving chirp; This represents the baseband signal bandwidth of Chirp.

[0033] Example 3: A 4FSK Incoherent Demodulation Method Based on Coordination Parameters 1) Demodulation window calibration Acquired by synchronous capture Based on this, the detection window for the 4FSK symbol is set to... To avoid timing errors; The 4FSK symbol number indicates that the current process is in the th order. 4FSK data symbols.

[0034] 2) Calculate the relevant parameters within the window. Since 4FSK has four possible frequencies, the receiver uses four parallel matched filters (or correlators), each matched to one possible transmission frequency. The formula is as follows: ; 3) Calculate the squared energy of the output of each correlator: ; in: (In-phase component); (Orthogonal components); In the formula, This indicates that the text was extracted from the first... Receive baseband signals through a 4FSK detection window; and They represent the first The integral values ​​of path correlation and orthogonal correlation; Indicates by and The sum of squares of the first Non-coherent correlation energy.

[0035] 4) Judgment Comparing 4 energy values , , , Choose the largest corresponding frequency That is, the decision is to send the symbol. : .

[0036] This embodiment employs a dynamic parameter collaborative adjustment mechanism, which specifically includes the following: Frequency modulation adjustment based on channel conditions: dynamically adjusting the frequency modulation of the Chirp sequence based on the channel signal-to-noise ratio (SNR) estimated at the receiver. When the SNR is low (< -5dB), increase the frequency modulation. Increase the broadband characteristics of the chirp sequence to enhance noise immunity; when the SNR is high (>5dB), reduce the modulation frequency. This reduces system complexity. When the tuning frequency changes, the start frequency, end frequency, and local reference sequence should be updated simultaneously, while maintaining [the necessary parameters]. And the condition of scanning frequency band covering 4FSK carrier frequencies. The above adjustments can be achieved through pre-agreed multiple sets of parameter configurations or link feedback.

[0037] Carrier frequency compensation based on Doppler frequency offset: Doppler frequency offset estimated during Chirp synchronization. Dynamic compensation is performed on each carrier frequency of 4FSK, and the compensated carrier frequencies are as follows: This makes frequency detection more adaptable to channel changes and improves demodulation accuracy. The design must ensure that the residual errors of Chirp detection (such as timing jitter and frequency offset residuals) are within the demodulation tolerance of 4FSK.

[0038] Example 4: Simulation Experiment of Chirp-4FSK The simulation conditions are set as follows: number of Chirp sampling points The Chirp signal bandwidth is 40MHz, the 4FSK carrier frequency spacing is 10MHz, the 4FSK symbol rate is 10Msymbol / s, the system complex baseband sampling rate is 40MHz, and the Chirp synchronization sliding step size is 128.

[0039] Figure 3 The following diagram shows the 4FSK incoherent demodulation performance without Chirp frequency offset estimation compensation. When the frequency offset is 0.15 times the carrier frequency spacing, the demodulation performance decreases by about 1 dB; when the frequency offset is 0.2 times the carrier frequency spacing, the decrease is about 2 dB; and when the frequency offset reaches 0.3 times the carrier frequency spacing, the decrease exceeds 4 dB.

[0040] Figure 4 The performance is shown after applying Chirp synchronization frequency offset estimation and compensation to four carrier frequencies. When the frequency offset is 0.3 times the carrier frequency interval, the curve basically coincides with the curve without frequency offset, indicating that the frequency offset estimation obtained in the Chirp synchronization stage can be used to improve the demodulation reliability under large frequency offset conditions in 4FSK.

[0041] Figure 5 The timing estimation performance of the Chirp-4FSK system is shown. When the signal-to-noise ratio (SNR) is greater than -6 dB, Chirp's timing error capture probability is less than 10%. -7 This indicates that the synchronization method still has good acquisition performance under low signal-to-noise ratio.

[0042] Example 5: Transmitter and Receiver Processing like Figure 6 As shown, the transmitter includes an input data interface, a 4FSK modulator, a chirp sequence generator, a framing module, and an RF transmission module. Input data is grouped into two-bit blocks. The 4FSK modulator selects the corresponding carrier frequency based on the mapping relationship, and the generation duration is... The 4FSK data symbols. The Chirp sequence generator follows the parameter co-configuration module. , , and Generate the Chirp synchronization sequence. The framing module follows... Figure 1 The sequence shown connects the Chirp synchronization sequence, the spacer (the spacer is used to reduce the transient effects between the Chirp synchronization sequence and the first 4FSK data symbol), and... Each 4FSK data symbol is transmitted after the RF transmission module performs digital-to-analog conversion, up-conversion, and power amplification on the obtained baseband communication frame.

[0043] like Figure 7As shown, the receiver includes an RF receiving module, a Chirp detector, a frequency offset compensator, a timing controller, and a 4FSK demodulator. The Chirp detector includes a sliding window buffer unit, an FFT (Fast Fourier Transform) unit, a frequency domain correlation unit, an IFFT (Inverse Fast Fourier Transform) unit, a correlation power calculation unit, a peak detection unit, and a parameter estimation unit. The frequency offset compensator is based on... Update four relevant frequencies; the timing controller updates according to... , , ( (These are fixed parameters pre-agreed upon by both the sender and receiver; the receiving end directly uses these parameters when calculating the first detection window.) The detection window is generated; the 4FSK demodulator includes four parallel correlators, a frequency energy calculation unit, and a symbol decision unit, used to calculate the in-phase and quadrature correlation energies of the four channels and perform the maximum energy decision. These modules can be implemented using a digital signal processor, a field-programmable gate array (FPGA), an application-specific integrated circuit (ASIC), or a combination thereof.

[0044] For ease of description, the above system is described by dividing it into various modules based on their functions. Of course, in implementing the embodiments of this application, the functions of each module can be implemented in one or more software and / or hardware.

[0045] The system described in the above embodiments is used to implement the corresponding method in any of the foregoing embodiments and has the beneficial effects of the corresponding method embodiments, which will not be repeated here.

[0046] It should be noted that the above description describes some embodiments of this application. Other embodiments are within the scope of the appended claims. In some cases, the actions or steps recorded in the claims can be performed in a different order than that shown in the above embodiments and still achieve the desired result. Furthermore, the processes depicted in the drawings do not necessarily require a specific or sequential order to achieve the desired result. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0047] Based on the same inventive concept, corresponding to the methods of any of the above embodiments, embodiments of this application also provide an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor executes the program to implement the methods described in any of the above embodiments.

[0048] Figure 8This embodiment illustrates a more specific hardware structure of an electronic device, which may include a processor 1010, a memory 1020, an input / output interface 1030, a communication interface 1040, and a bus 1050. The processor 1010, memory 1020, input / output interface 1030, and communication interface 1040 are interconnected internally via the bus 1050.

[0049] The processor 1010 can be implemented using a general-purpose CPU (Central Processing Unit), microprocessor, application-specific integrated circuit (ASIC), or one or more integrated circuits, and is used to execute relevant programs to implement the technical solutions provided in the embodiments of this specification.

[0050] The memory 1020 can be implemented in the form of ROM (Read Only Memory), RAM (Random Access Memory), static storage device, dynamic storage device, etc. The memory 1020 can store the operating system and other applications. When the technical solutions provided in the embodiments of this specification are implemented by software or firmware, the relevant program code is stored in the memory 1020 and is called and executed by the processor 1010.

[0051] The input / output interface 1030 is used to connect input / output modules to realize information input and output. The input / output modules can be configured as components in the device (not shown in the figure) or externally connected to the device to provide corresponding functions. Input devices may include keyboards, mice, touch screens, microphones, various sensors, etc., and output devices may include displays, speakers, vibrators, indicator lights, etc.

[0052] The communication interface 1040 is used to connect a communication module (not shown in the figure) to enable communication between this device and other devices. The communication module can communicate via wired means (such as USB, Ethernet cable, etc.) or wireless means (such as mobile network, WIFI, Bluetooth, etc.).

[0053] Bus 1050 includes a pathway for transmitting information between various components of the device, such as processor 1010, memory 1020, input / output interface 1030, and communication interface 1040.

[0054] It should be noted that although the above-described device only shows the processor 1010, memory 1020, input / output interface 1030, communication interface 1040, and bus 1050, in specific implementations, the device may also include other components necessary for normal operation. Furthermore, those skilled in the art will understand that the above-described device may only include the components necessary for implementing the embodiments of this specification, and not necessarily all the components shown in the figures.

[0055] The electronic devices described above are used to implement the corresponding methods in any of the foregoing embodiments and have the beneficial effects of the corresponding method embodiments, which will not be repeated here.

[0056] Based on the same inventive concept, corresponding to the methods of any of the above embodiments, this application also provides a non-transitory computer-readable storage medium that stores computer instructions for causing the computer to perform the methods described in any of the above embodiments.

[0057] The computer-readable medium of this embodiment includes permanent and non-permanent, removable and non-removable media, and information storage can be implemented by any method or technology. Information can be computer-readable instructions, data structures, program modules, or other data. Examples of computer storage media include, but are not limited to, phase-change memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), other types of random access memory (RAM), read-only memory (ROM), electrically erasable programmable read-only memory (EEPROM), flash memory or other memory technologies, CD-ROM, digital versatile optical disc (DVD) or other optical storage, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other non-transfer medium that can be used to store information accessible by a computing device.

[0058] The computer instructions stored in the storage medium of the above embodiments are used to cause the computer to perform the methods described in any of the above embodiments, and have the beneficial effects of the corresponding method embodiments, which will not be repeated here.

[0059] Although this application has been described in conjunction with specific embodiments thereof, many substitutions, modifications, and variations of these embodiments will be apparent to those skilled in the art from the foregoing description. For example, other memory architectures (e.g., dynamic RAM (DRAM)) may be used with the embodiments discussed.

[0060] The embodiments of this application are intended to cover all such substitutions, modifications, and variations that fall within the broad scope of the claims of this application. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the embodiments of this application should be included within the protection scope of this application.

Claims

1. A 4FSK incoherent demodulation method based on Chirp synchronization sequences, characterized in that, include: The start frequency, end frequency, modulation frequency, and duration of the Chirp synchronization sequence are jointly determined based on the equally spaced 4FSK carrier frequencies and symbol periods, so that the Chirp scanning band covers the 4FSK carrier frequencies and has a frequency margin of a preset carrier frequency interval at both ends, so as to generate a communication frame that sequentially contains the Chirp synchronization sequence, spacer, and 4FSK data symbols. By performing up-scanning and down-scanning frequency domain correlation on the Chirp synchronization sequence in the received communication frame, timing estimates and frequency offset estimates are obtained. The timing estimates are used to determine the detection window for each 4FSK data symbol, and each carrier frequency is compensated according to the frequency offset estimates. By calculating the in-phase correlation and quadrature correlation quantities corresponding to the four carrier frequencies after compensation within each detection window, the energy value is obtained based on the sum of their squares, and the carrier frequency corresponding to the maximum energy value is determined as the transmitted symbol. The frequency modulation of the Chirp synchronization sequence is adjusted based on the signal-to-noise ratio estimated at the receiver: When the signal-to-noise ratio is below the first threshold, the frequency modulation frequency is increased; when the signal-to-noise ratio is above the second threshold, the frequency modulation frequency is decreased. When adjusting the frequency modulation frequency, the frequency scan range of the Chirp synchronization sequence and the local reference sequence are updated synchronously to maintain the coordination with the 4FSK carrier frequency interval and symbol period.

2. The method according to claim 1, characterized in that: The frequency scan range of the Chirp synchronization sequence covers the frequency range of the 4FSK carrier frequency set. Let the minimum frequency in the 4FSK carrier frequency set be... The maximum frequency is The frequency interval is ; The start frequency of the Chirp synchronization sequence Termination frequency In the formula, For coefficients; And adjust the frequency In the formula, For matching coefficients, The duration of the Chirp synchronization sequence.

3. The method according to claim 1, characterized in that, The frequency domain correlation includes: The received sampling sequence is truncated according to the preset sliding step size. Each sliding window is padded with zeros to the preset fast Fourier transform length and then a fast Fourier transform is performed. The transform result is multiplied by the frequency domain conjugate of the local upper and lower frequency sweep reference sequences respectively, and then an inverse fast Fourier transform is performed. By calculating the squared modulus of the two inverse transform results, the upper-sweep frequency correlation power sequence and the lower-sweep frequency correlation power sequence are obtained.

4. The method according to claim 3, characterized in that: The peak value and peak position of the upper and lower frequency-correlated power sequences are determined respectively. When neither peak value reaches the detection threshold, the sliding window is moved. When both peak values ​​reach the detection threshold, parabolic interpolation is performed using each peak position and its adjacent sampling points. The timing estimate is determined based on the average of the two interpolated peak positions. The frequency offset estimate is determined based on the difference between the two interpolated peak positions.

5. The method according to claim 4, characterized in that: Dynamic compensation is performed on each carrier frequency of 4FSK based on the frequency offset estimate, and four parallel correlators are configured based on the compensated carrier frequencies, so that the frequency offset estimate obtained in the Chirp synchronization phase can be directly used for frequency calibration of the 4FSK data segment.

6. The method according to claim 5, characterized in that: Within each detection window, the in-phase correlation and quadrature correlation are calculated for the compensated carrier frequency. The energy value is obtained based on the in-phase correlation and quadrature correlation. By comparing the four energy values, the frequency corresponding to the largest energy value is selected and determined as the transmitted symbol.

7. A 4FSK incoherent demodulation system based on Chirp synchronization sequences, characterized in that: It includes a parameter coordination configuration module, a frame generation module, a receiving front end, a Chirp synchronization module, a frequency offset compensation module, a window control module, a 4FSK noncoherent demodulation module, and an output module; The parameter coordination configuration module is used to jointly configure the Chirp synchronization sequence according to four equally spaced 4FSK carrier frequencies and symbol periods, so that its scanning frequency band covers the four carrier frequencies and has frequency margin, the duration is an integer multiple of the symbol period, and the frequency change is 4 times the carrier frequency interval. The frame generation module is used to generate communication frames that sequentially contain a Chirp synchronization sequence, a spacer, and 4FSK data symbols. The Chirp synchronization module is used to perform up-sweep and down-sweep frequency domain correlation on the baseband signal output from the receiving front end and output timing estimate and frequency offset estimate. The frequency offset compensation module is used to compensate for the four 4FSK carrier frequencies; The window control module is used to establish a 4FSK detection window based on the timing estimate; The 4FSK incoherent demodulation module is used to calculate the energy of four in-phase and quadrature correlation channels and complete the maximum energy decision. The output module is used to output demodulated data.

8. A non-transitory computer-readable storage medium, characterized in that, in, The non-transitory computer-readable storage medium stores computer instructions for causing a computer to perform the method described in any one of claims 1-6.

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