An adaptive FM and FSK blind demodulation method, system, device and terminal

Abstract

The application belongs to the technical field of signal modulation, and discloses a self-adaptive FM and FSK blind demodulation method, system, device and terminal, which performs FFT processing on an input signal, observes signal spectrum characteristics, and judges whether the signal has the characteristics of comb spectrum, calculates the center frequency and the interval of peaks according to the spectrum obtained by FFT, the interval of spectrum peaks and the sampling rate; the signal is differentially processed by using the principle of differential demodulation; the differentially processed signal is subjected to FFT processing, the spectrum of two signals is compared, and the two signals are distinguished through spectrum characteristics; the two signals are distinguished through software algorithm analysis of single frequency components in the spectrum according to the FFT result; the FSK signal demodulation circuit is gated, the FSK demodulation circuit is controlled to perform FSK demodulation, the FSK baseband digital signal is recovered, and the information transmitted is decoded by a single-chip microcomputer. The application compares the spectrum characteristics of FM and FSK signals, has fast response speed, high result accuracy, and realizes compatible demodulation.

Description

Technical Field

[0001] The present invention belongs to the technical field of signal modulation, and in particular relates to an adaptive FM and FSK blind demodulation method, system, equipment and terminal. Background Art

[0002] The complex and volatile nature of marine fisheries and the frequent typhoon activity present significant safety risks, making them an accident-prone industry. Therefore, fishery communications are crucial to ensuring safe and effective distress communications and improving the success rate of rescue efforts. Traditional fishery radio stations use FM modulation, with the primary interactive signal being analog voice. With the advancement of communication technology, digital fishery radio stations are increasingly being developed to meet the needs of modern fishery communications. Digital fishery radio stations typically employ specific digital modulation and demodulation techniques, such as FSK, to convert audio signals into digital data for greater communication efficiency and reliability. When traditional and digital fishery radio stations coexist, FM and FSK signals coexist. In these situations, the receiver must first identify the modulation scheme of the signal before taking appropriate measures to demodulate it. Because both FM and FSK signals utilize FM modulation, identification and discrimination require the extraction of complex characteristic parameters. In communication systems where FM and FSK coexist, it is often necessary to identify the modulation scheme and then adopt the appropriate demodulation method. Since the spectral characteristics of FM and FSK signals are similar and both use frequency modulation, traditional methods are difficult to distinguish between the two modulation methods. Existing literature has studied the use of neural networks to extract signal feature parameters to realize FM and FSK modulation identification, but it requires strong computing power support, and the system complexity and cost are very high.

[0003] An existing signal modulation recognition technology uses a neural network to extract the instantaneous frequency of the signal, uses the different characteristics of the instantaneous frequency to identify FSK and FM modulation, and then uses a fully digital method to complete FM and FSK demodulation.

[0004] Through the above analysis, the problems and defects of the existing technology are: the existing research on the technology of using neural networks to identify and demodulate signal modulation methods is highly complex, requires large resources, is difficult to maintain, is not suitable for embedded system implementation, and is costly and difficult to promote. Summary of the Invention

[0005] In view of the problems existing in the prior art, the present invention provides an adaptive FM and FSK blind demodulation method, system, device and terminal.

[0006] The present invention is achieved in that a self-adaptive FM and FSK blind demodulation method is provided, wherein the self-adaptive FM and FSK blind demodulation method comprises:

[0007] S1, perform FFT processing on the input signal, observe the signal spectrum characteristics, and determine whether it has comb spectrum characteristics. If there is no comb spectrum characteristics, it is determined to be an FM voice signal, and the FM signal demodulation circuit is selected to complete the demodulation and output of the FM signal; if there is a comb spectrum characteristic, it is determined to be an FSK signal or an FM single-tone signal, and step S2 is performed;

[0008] S2, based on the spectrum obtained by FFT, the center frequency f and the peak interval Δf are calculated according to the spectrum peak interval and sampling rate;

[0009] S3, adopts the principle of differential demodulation to perform ΔT differential processing on the signal;

[0010] S4, performing FFT processing on the signal after ΔT difference processing, comparing the two signal spectra, and distinguishing the two signals by their spectrum characteristics;

[0011] S5, based on the FFT results, the two signals are distinguished by analyzing the single frequency components in the spectrum through software algorithms;

[0012] S6, selects the FSK signal demodulation circuit, controls the FSK demodulation circuit to perform FSK demodulation, recovers the FSK baseband digital signal, and completes the channel decoding by the single chip microcomputer to restore the transmitted information;

[0013] S7, selecting the FM signal demodulation circuit, and controlling the FM demodulation circuit to demodulate and output the FM signal.

[0014] Furthermore, the ΔT difference principle is: ΔT = 1 / (2*Δf), where the signal to be processed is the time of delay ΔT; the delayed signal is multiplied by the original signal without delay through a multiplier, and the multiplier output passes through a low-pass filter with a cutoff frequency of fl, where fl <f / 2。

[0015] Furthermore, the process of FSK signal after ΔT differential processing is as follows:

[0016] FSK modulated signal:

[0017]

[0018]

[0019] FSK signal after ΔT difference:

[0020]

[0021] The signal obtained by multiplying the two signals by the multiplier may be:

[0022] cosω1t*cosv1t; cosv2t*cosω2t; cosω1t*cosv2t;

[0023] The signal frequency components are: 2f1, 2f2, f1+f2; f1-f2;

[0024] After passing through the corresponding low-pass filter, a signal with a frequency of f1-f2 alternating between a single-frequency sine wave and direct current can be obtained, which is the output of the FSK signal after ΔT differential processing.

[0025] Furthermore, in S5, according to the FFT results, the spectrum of the FM single-tone signal after ΔT differencing shows no obvious regularity. The frequency corresponding to the center point of the peak of the spectrum of the FSK signal after ΔT differencing is the FSK signal frequency deviation f1-f2, and the corresponding position is shown in the red box in the figure. From this, the FSK signal frequency deviation parameter information can be obtained. A software algorithm is used to determine whether the spectrum peak has a protrusion. If the spectrum peak has a protrusion and decreases outside the protrusion, it is determined to be an FSK signal and the process proceeds to step S6. If the peak interval corresponds to a frequency of 2 times Δf and there is no peak, it is an FM signal and the process proceeds to step S7.

[0026] Another object of the present invention is to provide an adaptive FM and FSK blind demodulation system using the adaptive FM and FSK blind demodulation method, the adaptive FM and FSK blind demodulation system comprising:

[0027] The FFT processing module is used to perform FFT processing on the input signal, observe the signal spectrum characteristics, and determine whether it has comb spectrum characteristics. If there is no comb spectrum characteristics, it is determined to be an FM voice signal, and the FM signal demodulation circuit is selected to complete the demodulation and output of the FM signal; if there is a comb spectrum characteristic, it is determined to be an FSK signal or an FM single-tone signal;

[0028] The differential processing module is used to perform ΔT differential processing on the signal using the principle of differential demodulation;

[0029] The post-differentiation signal processing module is used to perform FFT processing on the signal after ΔT difference processing, compare the two signal spectra, and distinguish the two signals based on the spectral characteristics;

[0030] Signal discrimination module, used to distinguish two signals by analyzing single-frequency components in the spectrum through software algorithms based on FFT results;

[0031] The demodulation output module is used to select the FM signal demodulation circuit and control the FM demodulation circuit to demodulate and output the FM signal.

[0032] Another object of the present invention is to provide a computer device, which includes a memory and a processor, wherein the memory stores a computer program, and when the computer program is executed by the processor, the processor executes the steps of the adaptive FM and FSK blind demodulation method.

[0033] Another object of the present invention is to provide a computer-readable storage medium storing a computer program, which, when executed by a processor, causes the processor to perform the steps of the adaptive FM and FSK blind demodulation method.

[0034] Another object of the present invention is to provide an information data processing terminal, which is used to implement the adaptive FM and FSK blind demodulation system.

[0035] In combination with the above technical solutions and the technical problems solved, the advantages and positive effects of the technical solutions to be protected by the present invention are as follows:

[0036] First, in view of the technical problems existing in the above-mentioned prior art and the difficulty of solving these problems, we closely combine the technical solutions to be protected by the present invention and the results and data during the research and development process, and conduct a detailed and in-depth analysis of how the technical solutions of the present invention solve the technical problems and some creative technical effects brought about by solving the problems. The specific description is as follows:

[0037] The present invention utilizes a single chip microcomputer, FM and FSK demodulation circuits to complete signal recognition and demodulation. The system circuit is simple, low in cost, easy to implement, and the sensitivity of the dedicated FM and FSK demodulation chips is higher.

[0038] The present invention can realize the recognition of FM and FSK signals by performing only two FFTs, has a simple algorithm, requires little resources, is easy to be implemented on an embedded system, and is convenient for large-scale promotion and popularization.

[0039] The present invention distinguishes the special case of FM single-tone signals from FSK and adopts a ΔT difference processing method for judgment, thereby avoiding misjudgment resulting in demodulation of erroneous signals.

[0040] Second, considering the technical solution as a whole or from the perspective of the product, the technical effects and advantages of the technical solution to be protected by the present invention are described in detail as follows:

[0041] The present invention utilizes two FFT results to identify FM and FSK signals, which greatly reduces the complexity of the algorithm and resource requirements. It can be directly implemented on an embedded system and is easy to maintain, has low power consumption, low cost, strong practicality, and high demodulation sensitivity.

[0042] The present invention uses the spectrum characteristics of FM and FSK signals for comparison, has a fast response speed, high result accuracy, and realizes compatible demodulation.

[0043] Third, the expected benefits and commercial value after the transformation of the technical solution of the present invention are: since the present invention can be used for compatible signal demodulation in the coexistence of traditional and new fishing stations, the system cost is low, the sensitivity is high, it is easy to implement, and it is convenient to promote. It can be directly upgraded to replace the demodulation function of existing fishing radio stations, and has great market value.

[0044] Whether the technical solution of the present invention overcomes technical prejudice: This system adopts a simple hardware structure and a low-complexity algorithm to realize blind demodulation of FM and FSK signals. It is compatible with demodulating the original fishery radio station and has the function of demodulating digital fishery radio stations. It does not require the use of neural networks or the calculation of high-order cumulative quantities, which greatly reduces the technical threshold and cost and can be promoted on a large scale.

[0045] Fourth, the adaptive FM and FSK blind demodulation method has multiple steps, each of which plays a key role in the overall demodulation process. The following are the significant technical advances achieved in each step:

[0046] S1: FFT processing and comb spectrum judgment

[0047] Technological progress: Through real-time frequency domain analysis, the input signal type can be quickly and accurately judged, avoiding the tedious time domain analysis and additional signal feature extraction process.

[0048] S2: Calculate center frequency and peak interval

[0049] Technological progress: The center frequency and frequency peak interval of the signal are determined, which provides key parameters for the subsequent demodulation process and improves the accuracy of demodulation.

[0050] S3: Differential demodulation

[0051] Technological progress: Through differential demodulation, frequency information is effectively converted into amplitude information, creating conditions for further differentiation of FSK and FM single-tone signals.

[0052] S4: FFT processing and comparison again

[0053] Technological advancement: Re-processing the differentiated signal with an FFT further clarifies the signal type. This step enhances the adaptive capabilities of the demodulation method, ensuring high accuracy.

[0054] S5: Software Algorithm Analysis

[0055] Technological advancement: Software algorithms can accurately distinguish between FSK signals and FM single-tone signals, which greatly reduces the risk of misinterpretation and ensures the accuracy of the demodulation process.

[0056] S6: FSK demodulation

[0057] Technological advancement: The demodulation circuit specifically designed for FSK signals ensures high-quality demodulation of FSK signals. Combined with the channel decoding of the microcontroller, it further ensures complete information recovery.

[0058] S7: FM demodulation

[0059] Technological progress: The demodulation circuit for FM voice signals ensures clear recovery of voice information, improving voice intelligibility and call quality.

[0060] In summary, this adaptive demodulation method combines multiple technical strategies to make FM and FSK blind demodulation more efficient and accurate, bringing significant technological progress to real-time communication systems. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0062] Figure 1 This is a block diagram of the system hardware principles provided by an embodiment of the present invention;

[0063] Figure 2 This is a flow chart of an adaptive FM and FSK blind demodulation method provided by an embodiment of the present invention;

[0064] Figure 3 : is a signal spectrum diagram provided by an embodiment of the present invention; wherein (a) is an FM single-tone signal, and (b) is an FSK signal;

[0065] Figure 4 2 is a schematic diagram of the ΔT difference principle provided by an embodiment of the present invention;

[0066] Figure 5 : This is the waveform after the score checking process provided by the embodiment of the present invention; wherein (a) is an FM single tone signal, and (b) is an FSK signal;

[0067] Figure 6 1 is a schematic diagram of the results of FFT after differential processing provided by an embodiment of the present invention; wherein (a) is an FM single-tone signal, and (b) is an FSK signal spectrum. DETAILED DESCRIPTION

[0068] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0069] In view of the problems existing in the prior art, the present invention provides an adaptive FM and FSK blind demodulation method, system, device and terminal. The present invention is described in detail below with reference to the accompanying drawings.

[0070] The following are the specific implementation schemes of the steps of the adaptive FM and FSK blind demodulation method provided by the present invention:

[0071] S1: FFT processing and comb spectrum judgment

[0072] Use Fast Fourier Transform (FFT) to transform the input signal into the frequency domain.

[0073] Analyze the obtained signal spectrum characteristics to see if there are obvious comb spectrum features.

[0074] If there is no comb spectrum feature, the system determines that the input signal is an FM voice signal and jumps to step S7 for FM demodulation.

[0075] If there is a comb spectrum feature, go to step S2.

[0076] S2: Calculate center frequency and peak interval

[0077] In the spectrum, find the frequency peaks and measure their separation.

[0078] The center frequency f and peak interval Δf of the signal are calculated using the FFT sampling rate.

[0079] S3: Differential demodulation

[0080] Using the principle of differential demodulation, the signal is subjected to time differential processing, which is usually used to convert frequency changes into amplitude changes, thereby preparing for the next step of FSK demodulation.

[0081] S4: FFT processing and comparison again

[0082] The signal after ΔT difference processing is subjected to FFT processing again.

[0083] Compare the spectra of the original signal and the signal after differential processing to distinguish the FSK signal from the FM single-tone signal.

[0084] S5: Software Algorithm Analysis

[0085] The spectral characteristics of the two signals are further analyzed using software algorithms.

[0086] It mainly analyzes the single-frequency components in the spectrum to more accurately distinguish FSK signals from FM single-tone signals.

[0087] S6: FSK demodulation

[0088] When it is determined that the input is an FSK signal, the FSK demodulation circuit is started.

[0089] The demodulation circuit is controlled to convert the FSK signal into its baseband digital signal.

[0090] Use a single-chip microcomputer to perform channel decoding on the demodulated digital signal to restore the original transmission information.

[0091] S7: FM demodulation

[0092] When it is determined that the input is an FM signal, the FM demodulation circuit is started.

[0093] The demodulation circuit is controlled to demodulate the FM signal to its original or baseband signal.

[0094] This adaptive demodulation method combines hardware circuits and software algorithms, and can perform fast and accurate blind demodulation based on the actual characteristics of the signal.

[0095] The embodiment of the present invention adopts a single chip microcomputer, a dedicated FM and FSK demodulation chip, an analog-to-digital converter, an LNA and a frequency conversion circuit, etc. to complete the recognition and demodulation functions of FM and FSK signals.

[0096] The hardware structure of the system is as follows Figure 1 As shown in the figure, the FM or FSK signal in the air is first amplified by the LNA. Then, it is converted by frequency converter 1 to obtain intermediate frequency signal 1, which is collected by the microcontroller and the modulation method is identified by the microcontroller. Then, it is converted by frequency converter 2 to obtain intermediate frequency signal 2, which is controlled by the microcontroller and sent to the FM demodulation circuit or FSK demodulation circuit for demodulation. Finally, the FSK demodulation result is sent to the microcontroller for channel decoding to restore the transmitted information.

[0097] In a specific embodiment, the single chip microcomputer may be an STM32H750 or an STMF407, the FM demodulation circuit may be a circuit composed of an MC3361 or a circuit composed of an RDA5820, and the FSK demodulation circuit may be a circuit composed of an SI4438 or an SI4463. The carrier frequency of the intermediate frequency signal 1 is 80 kHz, and the frequency of the intermediate frequency signal 2 is 10.7 MHz.

[0098] The function of frequency converter 1 is to move the signal to a low intermediate frequency suitable for ADC sampling in the microcontroller to realize modulation mode recognition; the function of frequency converter 2 is to move the signal to a high intermediate frequency suitable for the operating frequency of the demodulation chip to realize demodulation.

[0099] like Figure 2 As shown, the adaptive FM and FSK blind demodulation method provided by the embodiment of the present invention includes:

[0100] S1, perform FFT processing on the input signal, observe the signal spectrum characteristics, and determine whether it has comb spectrum characteristics. If there is no comb spectrum characteristics, it is determined to be an FM voice signal, and the FM signal demodulation circuit is selected to complete the demodulation and output of the FM signal; if there is a comb spectrum characteristic, it is determined to be an FSK signal or an FM single-tone signal, and step S2 is performed;

[0101] S2, based on the spectrum obtained by FFT, the center frequency f and the peak interval Δf are calculated according to the spectrum peak interval and sampling rate;

[0102] S3, adopts the principle of differential demodulation to perform ΔT differential processing on the signal;

[0103] S4, performing FFT processing on the signal after ΔT difference processing, comparing the two signal spectra, and distinguishing the two signals by their spectrum characteristics;

[0104] S5, based on the FFT results, the two signals are distinguished by analyzing the single frequency components in the spectrum through software algorithms;

[0105] S6, selects the FSK signal demodulation circuit, controls the FSK demodulation circuit to perform FSK demodulation, recovers the FSK baseband digital signal, and completes the channel decoding by the single chip microcomputer to restore the transmitted information;

[0106] S7, selecting the FM signal demodulation circuit, and controlling the FM demodulation circuit to demodulate and output the FM signal.

[0107] like Figure 3 As shown, Figure 3 (a) is the spectrum of FM signal, Figure 3 (b) is the FSK signal spectrum. Both signal spectra have comb spectrum characteristics and are difficult to distinguish.

[0108] In S1, a single-tone FM signal may appear in the actual FM signal, that is, the FM modulated signal is a single sine wave. For example, when FM is set to a stereo signal, there is a pilot signal or it is set to a CTCSS (Continuous Tone Coded Clean Smooth System) tone. Since the spectrum of the FM single-tone signal and the FSK signal both have comb spectrum characteristics, if there are comb spectrum characteristics, it is necessary to further determine the signal type.

[0109] like Figure 4 As shown, the ΔT difference principle is: ΔT = 1 / (2*Δf), where the signal to be processed is the time of delay ΔT; the delayed signal and the original signal without delay are multiplied by a multiplier, and the output of the multiplier is filtered by a low-pass filter with a cutoff frequency of fl, where fl <f / 2。

[0110] like Figure 5 As shown, Figure 5 (a) is the waveform of the FM single tone signal after ΔT differential processing, Figure 5(b) is the waveform of the FSK signal after ΔT difference processing. The time domain characteristics of the two signals are obviously different after ΔT difference processing.

[0111] The process of FSK signal after ΔT differential processing is as follows:

[0112] FSK modulated signal:

[0113]

[0114]

[0115] FSK signal after ΔT difference:

[0116]

[0117] The signal obtained by multiplying the two signals by the multiplier may be:

[0118] cosω1t*cosω1t; cosω2t*cosω2t; cosω1t*cosω2t;

[0119] The signal frequency components are: 2f1, 2f2, f1+f2; f1-f2;

[0120] After passing through the corresponding low-pass filter, a signal with a frequency of f1-f2 alternating between a single-frequency sine wave and direct current can be obtained, which is the output of the FSK signal after ΔT differential processing.

[0121] like Figure 6 As shown, Figure 6 (a) is the result of FFT after differential processing of FM single-tone signal. Figure 6 (b) is the result of FFT after differential processing of the FSK signal.

[0122] In S5, the FFT results show that the spectrum of the FM single-tone signal after ΔT differentiation has no obvious regularity. The frequency corresponding to the center point of the peak of the spectrum of the FSK signal after ΔT differentiation is the FSK signal frequency deviation f1-f2, and the corresponding position is shown in the red box in the figure. This can be used to obtain the FSK signal frequency deviation parameter information. A software algorithm determines whether the spectrum peak has a protrusion. If the spectrum peak has a protrusion and decreases outside the protrusion, it is determined to be an FSK signal and proceeds to step S6. If the peak interval corresponds to a frequency of 2 times Δf and there is no peak, it is an FM signal and proceeds to step S7.

[0123] Preferably, the present invention may process the signal using a 2-fold ΔT difference or a multiple ΔT difference, or may distinguish the two signal modulation types based on the time domain characteristics of the signal after ΔT difference processing.

[0124] FM and FSK can be implemented by using other demodulation chips, such as RDA5820, NE564, SI4432, etc., and STM32H750 can be replaced with other MCU models.

[0125] An application embodiment of the present invention provides a computer device, which includes a memory and a processor. The memory stores a computer program. When the computer program is executed by the processor, the processor executes the steps of an adaptive FM and FSK blind demodulation method.

[0126] An application embodiment of the present invention provides a computer-readable storage medium storing a computer program. When the computer program is executed by a processor, the processor executes the steps of an adaptive FM and FSK blind demodulation method.

[0127] An application embodiment of the present invention provides an information data processing terminal, which is used to implement an adaptive FM and FSK blind demodulation system.

[0128] The embodiments of the present invention provide identification and demodulation in the case of coexistence of FM and FSK. The demodulation of both signals uses dedicated circuits, which have high stability and can fully solve the problem of information identification and reception in the case of coexistence of traditional fishing platforms and new fishing platforms. The system is simple, has small resource requirements, low power consumption, and low overall cost. It has broad market prospects and is easy to promote on a large scale. The experimental results are shown in the following table.

[0129]

[0130] The following are two specific embodiments and their corresponding implementation solutions, based on the previously described adaptive FM and FSK blind demodulation methods:

[0131] Example 1: DSP-based implementation

[0132] Implementation plan:

[0133] 1. Hardware selection: Choose a high-performance digital signal processor (DSP) as the core processing unit.

[0134] 2. Software Development:

[0135] Use DSP-specific development environments and languages, such as C or C++, to write algorithms such as FFT processing, comb spectrum judgment, and differential demodulation.

[0136] Use the internal modules or libraries of DSP to perform FFT operations to improve processing speed.

[0137] 3. Interface design:

[0138] Design appropriate analog / digital converter (ADC / DAC) interfaces to convert analog signals into digital signals for DSP processing.

[0139] Implement communication interfaces with other hardware modules as needed.

[0140] 4. FSK / FM demodulation circuit: Integrate a specific demodulation chip or use the built-in function of DSP for FSK / FM demodulation.

[0141] Example 2: FPGA-based implementation

[0142] Implementation plan:

[0143] 1. Hardware selection: Use a field programmable gate array (FPGA) as the core processing unit, especially for applications that require high-speed real-time processing.

[0144] 2. Hardware Description Language Development:

[0145] Use VHDL or Verilog language to design and implement digital logic such as FFT processing, comb spectrum judgment, differential demodulation, etc.

[0146] Leverage the parallel processing capabilities of FPGAs to process multiple signals or perform multiple tasks simultaneously.

[0147] 3. Interface design:

[0148] FPGAs usually have built-in high-speed ADC / DAC modules that can directly access analog signal lines and complete analog / digital conversion.

[0149] As needed, realize communication functions with other hardware modules or external interfaces.

[0150] 4. FSK / FM demodulation circuit: Design the corresponding digital logic circuit inside the FPGA to complete FSK / FM demodulation, or combine it with a dedicated demodulation chip.

[0151] These two examples demonstrate how to implement the same demodulation method using different technology platforms. DSPs are processors specifically designed for digital signal processing and are suitable for applications requiring fast and powerful computing capabilities. FPGAs, on the other hand, offer users greater flexibility, allowing them to design dedicated hardware circuits to meet specific requirements.

[0152] It should be noted that the embodiments of the present invention can be implemented by hardware, software, or a combination of software and hardware. The hardware portion can be implemented using dedicated logic; the software portion can be stored in a memory and executed by an appropriate instruction execution system, such as a microprocessor or dedicated design hardware. Those skilled in the art will appreciate that the above-mentioned devices and methods can be implemented using computer-executable instructions and / or contained in processor control code, for example, such as a carrier medium such as a disk, CD or DVD-ROM, a programmable memory such as a read-only memory (firmware), or a data carrier such as an optical or electronic signal carrier. The devices and modules of the present invention can be implemented by hardware circuits such as very large-scale integrated circuits or gate arrays, semiconductors such as logic chips, transistors, or programmable hardware devices such as field programmable gate arrays, programmable logic devices, etc., can also be implemented by software executed by various types of processors, or can be implemented by a combination of the above-mentioned hardware circuits and software, such as firmware.

[0153] The above description is only a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent substitutions and improvements made by any technician familiar with this technical field within the technical scope disclosed by the present invention and within the spirit and principles of the present invention should be covered by the scope of protection of the present invention.

Claims

1. An adaptive FM and FSK blind demodulation method, characterized in that: Automatically distinguish FM and FSK signals by performing FFT processing on the input signal and observing the signal spectrum characteristics; when no comb spectrum characteristics are detected, the system determines it as an FM voice signal and demodulates it; when comb spectrum characteristics are detected, calculate using the spectrum peak interval and sampling rate, and then accurately distinguish the FSK signal from the FM tone signal through the differential demodulation principle and software algorithm analysis, and accordingly select an appropriate demodulation circuit for demodulation output; The adaptive FM and FSK blind demodulation method specifically includes: S1, Perform FFT processing on the input signal, observe the signal spectrum characteristics, and determine whether it has the characteristics of a comb spectrum. If there are no comb spectrum characteristics, it is determined as an FM voice signal, then select the FM signal demodulation circuit to complete the demodulation output of the FM signal; if there are comb spectrum characteristics, it is determined as an FSK signal or an FM tone signal, and proceed to step S2; S2, According to the spectrum obtained by FFT, calculate the center frequency f and the peak interval Δf based on the spectrum peak interval and the sampling rate; S3, Adopt the principle of differential demodulation to perform ΔT differential processing on the signal; S4, Perform FFT processing on the signal after ΔT differential processing, compare the spectra of the two signals, and distinguish the two signals through the spectrum characteristics; S5, According to the FFT result, analyze the single-frequency components in the spectrum through software algorithms to distinguish the two signals; S6, Select the FSK signal demodulation circuit, control the FSK demodulation circuit to perform FSK demodulation, recover the FSK baseband digital signal, and the single-chip microcomputer completes the channel decoding to restore the transmitted information; S7, Select the FM signal demodulation circuit, control the FM demodulation circuit to perform demodulation output on the FM signal; The method for calculating the center frequency and peak interval in S2 is: In the spectrum, find the frequency peak and measure its interval Calculate the center frequency f and peak interval Δf of the signal using the sampling rate of FFT; The method for performing differential demodulation in S3 is: Use the principle of differential demodulation to perform time differential processing on the signal, which is usually used to convert frequency changes into amplitude changes to prepare for the next FSK demodulation The method for performing the second FFT processing and comparison in S4 is: Perform FFT processing on the signal after ΔT differential processing again Compare the spectra of the original signal and the signal after differential processing to distinguish the FSK signal and the FM tone signal The method for performing software algorithm analysis in S5 is: Use software algorithms to further analyze the spectrum characteristics of the two signals Mainly analyze the single-frequency components in the spectrum to more accurately distinguish the FSK signal and the FM tone signal; [[ID=XXX]]The ΔT differential principle is: ΔT = 1 / (2*Δf), where the signal to be processed is the time delayed by ΔT; multiply the delayed signal and the original undelayed signal through a multiplier, and the output of the multiplier passes through a low-pass filter with a cut-off frequency of fl, where fl < f / 2; the process of the FSK signal through ΔT differential processing is as follows: FSK modulated signal: FSK signal after ΔT differential: The signals obtained after multiplying the two signals through a multiplier may be: cosω1t*cosω1t; cosω2t*cosω2t; cosω1t*cosω2t; The signal frequency components are: 2f1, 2f2, f1+f2; f1-f2; After passing through the corresponding low-pass filter, a signal with a frequency of f1-f2 alternating between a single-frequency sine wave and DC can be obtained, which is the output of the FSK signal after ΔT differential processing; In S5, according to the results obtained by FFT, the spectrum of the FM single-tone signal has no obvious rules after ΔT differential processing; the frequency corresponding to the center point of the spectrum peak protrusion of the FSK signal after ΔT differential processing is the FSK signal frequency deviation f1-f2, and the corresponding position is shown in the red box mark in the figure, from which the FSK signal frequency deviation parameter information can be obtained; the software algorithm is used to determine whether there is a protrusion in the spectrum peak. If there is a protrusion in the spectrum peak and it decreases outside the protrusion, it is judged to be an FSK signal, and step S6 is performed; if the peak interval corresponds to a frequency of 2 times Δf, and there is no protrusion in the peak, it is an FM signal, and step S7 is performed.

2. The adaptive FM and FSK blind demodulation method according to claim 1, wherein: The method for S1 to perform FFT processing and comb spectrum judgment is: Use Fast Fourier Transform (FFT) to convert the input signal into the frequency domain Analyze the obtained signal spectrum characteristics to see if there are obvious comb spectrum features If there is no comb spectrum feature, the system determines that the input signal is an FM voice signal and jumps to step S7 for FM demodulation. If there is a comb spectrum feature, go to step S2.

3. The adaptive FM and FSK blind demodulation method according to claim 1, wherein: The method for S6 to perform FSK demodulation is: When the input is determined to be an FSK signal, the FSK demodulation circuit is started Control the demodulation circuit to convert the FSK signal into its baseband digital signal Use the microcontroller to perform channel decoding on the demodulated digital signal to restore the original transmission information The method for S7 to perform FM demodulation is: When the input is determined to be an FM signal, the FM demodulation circuit is started The demodulation circuit is controlled to demodulate the FM signal to its original or baseband signal.

4. An adaptive FM and FSK blind demodulation system using the adaptive FM and FSK blind demodulation method according to any one of claims 1 to 3, characterized in that: Adaptive FM and FSK blind demodulation system includes: The FFT processing module is used to perform FFT processing on the input signal, observe the signal spectrum characteristics, and determine whether it has comb spectrum characteristics. If there is no comb spectrum characteristics, it is determined to be an FM voice signal, and the FM signal demodulation circuit is selected to complete the demodulation and output of the FM signal; if there is a comb spectrum characteristic, it is determined to be an FSK signal or an FM single-tone signal; The differential processing module is used to perform ΔT differential processing on the signal using the principle of differential demodulation; The post-differentiation signal processing module is used to perform FFT processing on the signal after ΔT difference processing, compare the two signal spectra, and distinguish the two signals based on the spectral characteristics; Signal discrimination module, used to distinguish two signals by analyzing single-frequency components in the spectrum through software algorithms based on FFT results; The demodulation output module is used to select the FM signal demodulation circuit and control the FM demodulation circuit to demodulate and output the FM signal.

5. An information data processing terminal, the information data processing terminal being used to implement the adaptive FM and FSK blind demodulation system as claimed in claim 1.

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