A method and system for identifying and demodulating QPSK and 8PSK

Abstract

The present invention discloses a method and system for QPSK and 8PSK identification and demodulation. The method identifies the modulation type of an input signal, performs M-th power calculation on the input signal according to the modulation type, and calculates the index corresponding to the maximum value of the amplitude spectrum power; calculates the coarse frequency deviation point corresponding to the index and the corresponding compensation signal, calculates the frequency point value corresponding to the maximum value of the phase difference value of the compensation signal, and uses the frequency point value to perform frequency compensation on the input signal to obtain a frequency-free signal; calculates the position of each point of the frequency-free signal on the phase-free standard constellation diagram corresponding to each point on the constellation diagram to obtain a phase-free standard signal; corrects the phase deviation between the phase-free standard signal and the frequency-free signal, takes the average of the corrected phase deviation to obtain the phase deviation to be compensated, and performs phase deviation compensation on the frequency-free signal to obtain a phase-free signal. The modulation type identification of the input signal is automatically completed during the frequency deviation estimation process, and the frequency deviation estimation and phase deviation estimation process have fewer steps and a simpler process.

Description

Technical Field

[0001] The present invention relates to the field of digital communication technology, and in particular to a method and system for identifying and demodulating QPSK and 8PSK. Background Art

[0002] Phase Shift Keying (PSK) is a digital modulation scheme and a form of phase modulation. 8PSK corresponds to PSK with eight states, while QPSK corresponds to PSK with four states. 8PSK is less robust to noise than QPSK, but offers higher data throughput. Both signals are widely used in communications. Due to their strong similarities, many algorithms struggle to accurately identify and demodulate them. Therefore, the identification, frequency offset estimation, and phase offset estimation of these two signals are crucial in communications. Currently, methods for identifying and demodulating QPSK and 8PSK typically prioritize identification followed by demodulation. This approach utilizes the signal's instantaneous characteristic parameters combined with digital modulation signal recognition algorithms to identify the signal, which is then demodulated. Coherent demodulation is a common method, but it utilizes multiple modules, resulting in numerous computational steps and a lengthy process. Summary of the Invention

[0003] The object of the present invention is to provide a method and system for QPSK and 8PSK identification and demodulation, which automatically completes the modulation type identification of the input signal during the frequency offset estimation process, and the process steps of frequency offset estimation and phase offset estimation are fewer and simpler.

[0004] To achieve the above objectives, this application provides the following solutions:

[0005] In one aspect, the present application provides a method for identifying and demodulating QPSK and 8PSK, comprising the following steps:

[0006] S1. Acquire the input signal after clock synchronization and identify the modulation type of the input signal, which includes 8PSK and QPSK.

[0007] S2. Perform M-th power calculation on the input signal according to the modulation type, where the value of M corresponds to the modulation type, and calculate the index MaxIdx corresponding to the maximum value of the amplitude spectrum power of the input signal after the M-th power calculation;

[0008] S3. Calculate the coarse-estimated frequency offset point corresponding to the index MaxIdx, calculate the compensation signal corresponding to the coarse-estimated frequency offset point, calculate the frequency point value corresponding to the maximum phase difference value of the compensation signal, and use the frequency point value to perform frequency compensation on the input signal to obtain a signal without frequency offset;

[0009] S4. Calculate the position of each point on the constellation diagram corresponding to the frequency-free signal on the standard constellation diagram without phase deviation, and obtain the standard signal without phase deviation;

[0010] S5. Calculate the phase deviation between the standard signal without phase deviation and the signal without frequency deviation, correct the phase deviation, average the corrected phase deviations to obtain the phase deviation to be compensated, and perform phase deviation compensation on the signal without frequency deviation according to the phase deviation to be compensated to obtain a signal without phase deviation.

[0011] In some specific implementation schemes, the specific process of identifying the modulation type of the input signal in step S1 is:

[0012] S11, calculating a power of the input signal, where the exponent of the power is a first preset value, to obtain a first input signal;

[0013] S12. Calculate the amplitude spectrum power of the first input signal to obtain an amplitude data set, and calculate the maximum value, the index corresponding to the maximum value, and the average value in the amplitude data set;

[0014] S13. Compare the N-times average value with the maximum value. If the N-times average value is less than the maximum value, determine that the modulation type of the input signal is QPSK. If the N-times average value is greater than or equal to the maximum value, determine that the modulation type of the input signal is 8PSK.

[0015] S14. When the modulation type of the input signal is QPSK, M is 4; when the modulation type of the input signal is 8PSK, M is 8.

[0016] In some specific implementation schemes, the specific process of step S3 is:

[0017] S31. Calculate the rough estimated frequency offset point corresponding to the index MaxIdx according to the index MaxIdx corresponding to the maximum value. , L represents the data length of the input signal;

[0018] S32, calculate the compensation signal corresponding to the rough estimated frequency offset point EF , calculate the maximum phase difference value corresponding to the rough frequency offset point EF according to the compensation signal P 0;

[0019] S33, set the search step value, find the left and right frequency points on both sides of the rough estimated frequency offset point according to the search step value, calculate the compensation signal and the maximum phase difference value of the left and right frequency points respectively, and obtain the compensation signal corresponding to the left frequency point S l The maximum value of the phase difference P l , the compensation signal corresponding to the right frequency point S r The maximum value of the phase difference P r ;

[0020] S34, from the maximum phase difference value P 0. Maximum phase difference value P l The maximum value of the phase difference P r Select the largest value as P max , update the frequency value of the rough estimated frequency offset point EF to P max Corresponding frequency value;

[0021] S35, update the search step value, repeat steps S33-S34 until the search step value reaches the preset threshold value and outputs the compensation frequency corresponding to the rough estimated frequency offset point EF F est ;

[0022] S36, according to the compensation frequency F est The compensated frequency offset is calculated and used to compensate the input signal to obtain a frequency-offset-free signal.

[0023] In some specific implementation schemes, the initial setting value of the search step value step is step=1 / L, and each time the search step value is updated, the updated search step value is set to half of the current search step value.

[0024] In some specific implementation schemes, when the modulation type of the input signal is QPSK, the specific process of step S4 is:

[0025] S41, calculating the maximum phase value corresponding to the frequency-free signal, and calculating the absolute value of the difference between the maximum phase value and π;

[0026] S42, determining whether the absolute value of the difference is less than a second threshold; if the absolute value of the difference is less than or equal to the second threshold, rotating the frequency-offset-free signal by π / 8 to obtain a frequency-offset-free corrected signal;

[0027] S43, repeating steps S41-S42 for the frequency-offset-free correction signal until the absolute value of the difference is greater than a second threshold, and then outputting a final frequency-offset-free signal;

[0028] S44. Number the final frequency-offset-free signal on the constellation diagram, calculate the position of the final frequency-offset-free signal on the standard constellation diagram without phase offset, and obtain the standard signal without phase offset.

[0029] In some embodiments, the phase-bias-free standard signal is calculated The specific calculation process is:

[0030] calculate , Sig1(n) represents a signal with no frequency deviation;

[0031] Perform round calculation on Sig2(n) to obtain the number z of the frequency-free signal on the constellation diagram ( n ):

[0032]

[0033]

[0034] According to z ( n ), get the standard signal without phase deviation :

[0035]

[0036] ;

[0037] Wherein, j represents an imaginary unit, M represents a corresponding value determined according to the modulation type of the input signal, and round represents rounding to the nearest integer.

[0038] In some specific embodiments, according to z( n ) Calculate the standard signal without phase deviation The front also includes z ( n ) is corrected by: changing z ( n ) plus M for every number less than 0.

[0039] In some specific implementation schemes, the specific process of correcting the phase deviation in step S5 is:

[0040] Determine whether there is a value greater than π in the phase deviation α , α If it exists, correct the value to α- 2π.

[0041] In a second aspect, the present application provides a system for QPSK and 8PSK identification and demodulation, comprising:

[0042] Frequency offset estimation and compensation module, specifically including:

[0043] The signal recognition module is used to obtain the input signal that has completed clock synchronization and identify the modulation type of the input signal, which includes 8PSK and QPSK;

[0044] Perform M-th power calculation on the input signal according to the modulation type, where the value of M corresponds to the modulation type, and calculate the index MaxIdx corresponding to the maximum value of the amplitude spectrum power of the input signal after the M-th power calculation;

[0045] The frequency offset rough estimation module is used to calculate the rough estimated frequency offset frequency point corresponding to the index MaxIdx;

[0046] The frequency offset estimation module is used to calculate the compensation signal corresponding to the coarse frequency offset point and the frequency point value corresponding to the maximum phase difference value of the compensation signal;

[0047] The frequency offset compensation module is used to perform frequency compensation on the input signal using the frequency point value to obtain a signal without frequency offset;

[0048] Phase deviation estimation and compensation module, specifically including:

[0049] The constellation diagram numbering and standard signal calculation module is used to calculate the position of the frequency-free signal corresponding to each point on the constellation diagram on the standard constellation diagram without phase deviation, and obtain the standard signal without phase deviation;

[0050] The phase deviation estimation and compensation module is used to calculate the phase deviation between the standard signal without phase deviation and the signal without frequency deviation, correct the phase deviation, take the average of the corrected phase deviation to obtain the phase deviation to be compensated, and compensate the phase deviation of the signal without frequency deviation based on the phase deviation to obtain a signal without phase deviation.

[0051] The present invention has the beneficial effects:

[0052] Compared with the existing technology of first identifying and then demodulating QPSK and 8PSK, the instantaneous characteristic parameters of the signal are combined with the digital modulation signal recognition algorithm to identify the signal and then demodulate it. The commonly used method is coherent demodulation, and the calculation process is complicated.

[0053] In this application, the identification and demodulation of QPSK and 8PSK can automatically complete two types of identification during the frequency offset estimation process, and the process steps of frequency offset estimation and phase offset estimation are fewer and simpler, which reduces the computational complexity of identification, frequency offset estimation and phase offset estimation. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 Flowchart of the QPSK and 8PSK identification and demodulation method provided by an embodiment of the present invention;

[0055] Figure 2 A flow chart of a method for identifying the modulation type of an input signal provided by an embodiment of the present invention;

[0056] Figure 3 A flow chart of a method for frequency offset estimation and compensation provided in an embodiment of the present invention;

[0057] Figure 4 This is a block diagram of the QPSK and 8PSK identification and demodulation system provided in an embodiment of the present invention. DETAILED DESCRIPTION

[0058] The following will be combined with the accompanying drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, rather than all the embodiments. The following description of at least one exemplary embodiment is actually only illustrative and is in no way intended to limit the present invention and its application or use. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0059] Unless otherwise specifically stated, the relative arrangement of components and steps, the numerical expressions and numerical values ​​set forth in these embodiments do not limit the scope of the present invention.

[0060] At the same time, it should be understood that for the convenience of description, the sizes of the various parts shown in the drawings are not drawn according to the actual proportional relationship.

[0061] Additionally, descriptions of well-known structures, functions, and configurations may be omitted for clarity and conciseness. Those skilled in the art will recognize that various changes and modifications can be made to the examples described herein without departing from the spirit and scope of the present disclosure.

[0062] Technologies, methods and equipment known to ordinary technicians in the relevant art may not be discussed in detail, but where appropriate, such technologies, methods and equipment should be considered part of the authorization specification.

[0063] In all examples shown and discussed herein, any specific values ​​should be interpreted as merely exemplary and not limiting. Therefore, other examples of the exemplary embodiments may have different values.

[0064] Before introducing the specific implementation methods of this application, the following concepts are explained:

[0065] Example 1

[0066] like Figure 1 As shown, this embodiment provides a method for QPSK and 8PSK identification and demodulation, including the following steps:

[0067] S1. Acquire the input signal after clock synchronization and identify the modulation type of the input signal, which includes 8PSK and QPSK.

[0068] Specifically, if Figure 2 As shown, the specific process of identifying the modulation type of the input signal in step S1 is:

[0069] S11, calculating a power of the input signal, where the exponent of the power is a first preset value, to obtain a first input signal;

[0070] S12. Calculate the amplitude spectrum power of the first input signal to obtain an amplitude data set, and calculate the maximum value, the index corresponding to the maximum value, and the average value in the amplitude data set;

[0071] S13. Compare the N-times average value with the maximum value. If the N-times average value is less than the maximum value, determine that the modulation type of the input signal is QPSK. If the N-times average value is greater than or equal to the maximum value, determine that the modulation type of the input signal is 8PSK.

[0072] S14. When the modulation type of the input signal is QPSK, M is 4; when the modulation type of the input signal is 8PSK, M is 8.

[0073] S2. Perform M-th power calculation on the input signal according to the modulation type, where the value of M corresponds to the modulation type, and calculate the index MaxIdx corresponding to the maximum value of the amplitude spectrum power of the input signal after the M-th power calculation;

[0074] The first preset value is set to 4. When the modulation type of the input signal is QPSK, step S2 directly calls the maximum value, the index corresponding to the maximum value, and the average value calculated in step S12. When the modulation type of the input signal is 8PSK, step S2 corrects the value of M to 8, and repeats steps S11-S12 to calculate the maximum value corresponding to 8PSK, the index corresponding to the maximum value, and the average value.

[0075] S3. Calculate the coarse-estimated frequency offset point corresponding to the index MaxIdx, calculate the compensation signal corresponding to the coarse-estimated frequency offset point, calculate the frequency point value corresponding to the maximum phase difference value of the compensation signal, and use the frequency point value to perform frequency compensation on the input signal to obtain a signal without frequency offset;

[0076] Specifically, if Figure 3 As shown, the specific process of step S3 is:

[0077] S31. Calculate the rough estimated frequency offset point corresponding to the index MaxIdx according to the index MaxIdx corresponding to the maximum value. , L represents the data length of the input signal;

[0078] S32, calculate the compensation signal corresponding to the rough estimated frequency offset point EF , calculate the maximum phase difference value corresponding to the rough frequency offset point EF according to the compensation signal P 0;

[0079] S33, set the search step value, find the left and right frequency points on both sides of the rough estimated frequency offset point according to the search step value, calculate the compensation signal and the maximum phase difference value of the left and right frequency points respectively, and obtain the compensation signal corresponding to the left frequency point Sl The maximum value of the phase difference P l , the compensation signal corresponding to the right frequency point S r The maximum value of the phase difference P r ;

[0080] S34, from the maximum phase difference value P 0. Maximum phase difference value P l The maximum value of the phase difference P r Select the largest value as P max , update the frequency value of the rough estimated frequency offset point EF to P max Corresponding frequency value;

[0081] S35, update the search step value, repeat steps S33-S34 until the search step value reaches the preset threshold value and outputs the compensation frequency corresponding to the rough estimated frequency offset point EF F est ;

[0082] S36, according to the compensation frequency F est The compensated frequency offset is calculated and used to compensate the input signal to obtain a frequency-offset-free signal.

[0083] S4. Calculate the position of each point on the constellation diagram corresponding to the frequency-free signal on the standard constellation diagram without phase deviation, and obtain the standard signal without phase deviation;

[0084] Specifically, calculate the phase-bias-free standard signal The specific calculation process is:

[0085] calculate , Sig1(n) represents a signal with no frequency deviation;

[0086] Perform round calculation on Sig2(n) to obtain the number z of the frequency-free signal on the constellation diagram ( n ):

[0087]

[0088]

[0089] For z ( n ) is corrected by: z ( n ) plus M for every number less than 0.

[0090] According to the corrected z( n), get the standard signal without phase deviation :

[0091]

[0092] ;

[0093] Wherein, j represents an imaginary unit, M represents a corresponding value determined according to the modulation type of the input signal, and round represents rounding to the nearest integer.

[0094] When the modulation type of the input signal is QPSK (which has phase offset), if any point on the constellation diagram of the input QPSK (which has phase offset) is located above the X or Y axis, it will affect the subsequent phase offset estimation result. Therefore, the input QPSK is rotated until no point on the constellation diagram is located above the X or Y axis. Therefore, when the modulation type of the input signal is QPSK, the specific process of step S4 is as follows:

[0095] S41, calculating the maximum phase value corresponding to the frequency-free signal, and calculating the absolute value of the difference between the maximum phase value and π;

[0096] S42, determining whether the absolute value of the difference is less than a second threshold; if the absolute value of the difference is less than or equal to the second threshold, rotating the frequency-offset-free signal by π / 8 to obtain a frequency-offset-free corrected signal;

[0097] S43, repeating steps S41-S42 for the frequency-offset-free correction signal until the absolute value of the difference is greater than a second threshold, and then outputting a final frequency-offset-free signal;

[0098] S44. Number the final frequency-offset-free signal on the constellation diagram, calculate the position of the final frequency-offset-free signal on the standard constellation diagram without phase offset, and obtain the standard signal without phase offset.

[0099] S5. Calculate the phase deviation between the standard signal without phase deviation and the signal without frequency deviation, and correct the phase deviation. The specific process of correcting the phase deviation is as follows:

[0100] Determine whether there is a large π value in the phase deviation α , α If it exists, correct the value to α- 2π.

[0101] An average value of the corrected phase deviation is taken to obtain the phase deviation to be compensated, and phase deviation compensation is performed on the frequency-free signal according to the phase deviation to be compensated to obtain a phase-free signal.

[0102] Input signal For example, the specific process includes:

[0103] 1. Frequency offset estimation and compensation

[0104] Step 1-1: Input signal Sig ( n ) is the baseband IQ signal that has completed clock synchronization, and the data length is L, where n =1, 2, ... …, L.

[0105] right Sig ( n ) to calculate the Mth power, because we don’t know Sig ( n ) is QPSK or 8PSK, first uniformly set the first preset value to M = 4, that is, the first input signal for the next step is .

[0106] Step 1-2: Calculation The amplitude spectrum power of After performing fast Fourier transform and calculating the amplitude, we get Find out The maximum value MaxAbs and the index MaxIdx corresponding to the maximum value are calculated at the same time Average value .

[0107] Step 1-3: 10 times Compared with MaxAbs, if , then the input signal is QPSK, otherwise, , the input signal is 8PSK, modify M=8, and recalculate The index MaxIdx corresponding to the maximum value of the amplitude spectrum power.

[0108] Step 1-4: Calculate the frequency corresponding to MaxIdx At this time, EF is also a rough estimate of the frequency deviation.

[0109] Step 1-5: Calculate the compensation signal corresponding to EF ,in k =0, 1, 2, ... ..., L-1. Calculate the corresponding maximum phase difference value , where angle, sort, diff, and max are commonly used in MATLAB software. angle means returning the phase angle in the interval [-π, π] for each element of the complex array, sort means sorting the elements of the array in ascending order, diff means finding the difference, and max means finding the maximum value of the array. The calculation search step is step = 1 / L. The compensation signal and the maximum phase difference value of the left and right frequency points of EF are calculated according to the step step, and the compensation signal corresponding to the left frequency point (EF-step) is obtained respectively. S lCompensation signal corresponding to the right frequency point (EF+step) S r and its corresponding maximum phase difference value P l and P r , and find out P 0. P l and P r The maximum value in P max Update the EF frequency value to P max Corresponding frequency value and update search step , repeat this process until , terminate the loop.

[0110] It should be noted that is the termination condition, where 0.0001 can be adjusted to other values ​​as needed: the smaller the value, the more calculations are performed, the slower the calculation speed, and the higher the accuracy of the estimated frequency deviation value.

[0111] Step 1-6: At this point, the final P max The corresponding compensation frequency F est , calculate the compensation frequency offset ,right Compensation is performed to obtain the compensated frequency-deviation-free signal Sig1(n), that is, .

[0112] 2. Phase bias estimation and compensation

[0113] Step 2-1: Calculate the phase .

[0114] Step 2-2: When the signal is QPSK and M=4, calculate The absolute value of the difference between the maximum value in and π, that is, calculate ,contrast With a size of 0.001, if , rotate Sig1(n) by π / 8 and update ,renew , calculate the new ,contrast Repeat this process with a size of 0.001 until >0.001, terminate the loop and transfer the latest Assign to As a frequency-free signal.

[0115] Step 2-3: Calculation , , Round is a commonly used term in MATLAB software, meaning rounding to the nearest integer. Then, z(n) is corrected by adding M to every number in z(n) that is less than 0.

[0116] If the input signal is QPSK, the numbers in z(n) are 0, 1, 2, 3; if the input signal is 8PSK, the numbers in z(n) are 0, 1, 2, 3, 4, 5, 6, 7.

[0117] Steps 2-4: Calculation and calculate the phase-bias-free standard signal .

[0118] Steps 2-5: Calculation ,like There are values ​​greater than π in α , then the value is corrected to α- 2π, after the correction of the completed value The average value is the phase deviation β to be compensated. After phase deviation compensation, we can get , that is, a phase-biased signal is obtained.

[0119] Example 2

[0120] like Figure 4 As shown, this embodiment provides a system for QPSK and 8PSK identification and demodulation, including:

[0121] 1. Frequency offset estimation and compensation module, specifically including:

[0122] 1.1 Signal recognition module:

[0123] 1.1.1 Signal processing module, used to calculate the Mth power of the input signal that has completed clock synchronization to obtain a first input signal M. The first preset value can be set to 4 to facilitate subsequent signal recognition and frequency offset estimation;

[0124] 1.1.2 Amplitude power spectrum calculation module, used to calculate the amplitude of the first input signal, as well as the average value, maximum value and index corresponding to the maximum value of the amplitude, in preparation for the next step of recognition.

[0125] 1.1.3 Identification module, used to compare the average value of 10 times the amplitude with the maximum value. If the average value of 10 times the amplitude is less than the maximum value, the modulation type of the input signal is determined to be QPSK. If the average value of N times the amplitude is greater than or equal to the maximum value, the modulation type of the input signal is determined to be 8PSK.

[0126] 1.1.4 Output module, used to determine when the modulation type of the input signal is QQSK, and output the average value, maximum value, and index corresponding to the maximum value of the amplitude currently calculated by the amplitude power spectrum calculation module as input to the frequency offset rough estimation module;

[0127] When the modulation type of the input signal is 8PSK, the M value is corrected to 8, and the signal processing module and the amplitude power spectrum calculation module are recalculated. Then the average value, maximum value and index corresponding to the maximum value are output as the input of the frequency offset rough estimation module.

[0128] 1.2 Frequency offset rough estimation module, used to calculate the rough estimated frequency offset frequency point corresponding to the index MaxIdx;

[0129] 1.3 Frequency offset estimation module, used to calculate the compensation signal corresponding to the coarse frequency offset point, and calculate the frequency point value corresponding to the maximum phase difference value of the compensation signal;

[0130] 1.4 Frequency deviation compensation module, used to use the frequency point value to compensate the input signal to obtain a frequency deviation-free signal;

[0131] 2. Phase deviation estimation and compensation module, specifically including:

[0132] 2.1QPSK Special Processing Module

[0133] When the modulation type of the input signal is QPSK, this module is executed to prevent the points on the input QPSK (with phase offset) constellation diagram from being above the X or Y axis, which would affect the subsequent phase offset estimation results. The input QPSK corresponding frequency offset-free signal is rotated until no points on the constellation diagram are above the X or Y axis. Specifically, it includes:

[0134] 2.1.1 Phase calculation module, used to calculate the phase of the signal without frequency deviation and the absolute value of the difference between the maximum phase value and π;

[0135] 2.1.2 QPSK rotation module, used to determine whether the absolute value of the difference is less than a second threshold. If the absolute value of the difference is less than or equal to the second threshold, the frequency-free signal is rotated by π / 8 to obtain a frequency-free corrected signal. The phase calculation module is called again until the absolute value of the difference is greater than the second threshold, and the final frequency-free signal is output;

[0136] 2.2 Constellation diagram numbering module, used to calculate the position of each point on the constellation diagram corresponding to the frequency-free signal on the standard constellation diagram without phase deviation;

[0137] 2.3 Standard signal calculation module, used to calculate the phase-bias-free standard signal based on the output of the constellation diagram numbering module;

[0138] 2.4 Phase deviation estimation and compensation module, used to calculate the phase deviation between the standard signal without phase deviation and the signal without frequency deviation, correct the phase deviation, take the average of the corrected phase deviation to obtain the phase deviation to be compensated, and compensate the frequency deviation signal according to the phase deviation to be compensated to obtain a signal without phase deviation.

[0139] The above description is merely a preferred embodiment of the present invention and does not constitute any form of limitation to the present invention. Based on the technical essence of the present invention and within the spirit and principles of the present invention, any simple modification, equivalent replacement and improvement of the above embodiment shall still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A method for identifying and demodulating QPSK and 8PSK, characterized in that: The following steps are involved: S1. Acquire the input signal after clock synchronization and identify the modulation type of the input signal, which includes 8PSK and QPSK. S2. Perform M-th power calculation on the input signal according to the modulation type, where the value of M corresponds to the modulation type, and calculate the index MaxIdx corresponding to the maximum value of the amplitude spectrum power of the input signal after the M-th power calculation; S3. Calculate the coarse-estimated frequency offset point corresponding to the index MaxIdx, calculate the compensation signal corresponding to the coarse-estimated frequency offset point, calculate the frequency point value corresponding to the maximum phase difference value of the compensation signal, and use the frequency point value to perform frequency compensation on the input signal to obtain a signal without frequency offset; The specific process of step S3 is: S31. Calculate the rough estimated frequency offset point corresponding to the index MaxIdx according to the index MaxIdx corresponding to the maximum value. L represents the data length of the input signal; S32, calculating the compensation signal S0(n) corresponding to the coarse-estimated frequency offset point EF, and calculating the maximum phase difference value P0 corresponding to the coarse-estimated frequency offset point EF based on the compensation signal; S33, set the search step value, find the left and right frequency points on the left and right sides of the rough estimated frequency offset point according to the search step value, calculate the compensation signal and the maximum phase difference value of the left and right frequency points respectively, and obtain the compensation signal S corresponding to the left frequency point respectively. l and the maximum phase difference value P l , the compensation signal S corresponding to the right frequency point r and the maximum phase difference value P r ; S34, from the maximum phase difference value P0, the maximum phase difference value P l and the maximum phase difference value P r Select the largest value as P max , update the frequency value of the rough estimated frequency offset point EF to P max Corresponding frequency value; S35, update the search step value, repeat steps S33-S34 until the search step value reaches the preset threshold value and outputs the compensation frequency F corresponding to the rough estimated frequency offset point EF. est ; S36, according to the compensation frequency F est Calculate the compensation frequency deviation and use it to compensate the input signal to obtain a signal without frequency deviation; S4. Calculate the position of each point on the constellation diagram corresponding to the frequency-free signal on the standard constellation diagram without phase deviation, and obtain the standard signal without phase deviation; S5. Calculate the phase deviation between the standard signal without phase deviation and the signal without frequency deviation, correct the phase deviation, average the corrected phase deviations to obtain the phase deviation to be compensated, and perform phase deviation compensation on the signal without frequency deviation according to the phase deviation to be compensated to obtain a signal without phase deviation.

2. The method for identifying and demodulating QPSK and 8PSK according to claim 1, wherein: The specific process of identifying the modulation type of the input signal in step S1 is: S11, calculating a power of the input signal, where the exponent of the power is a first preset value, to obtain a first input signal; S12. Calculate the amplitude spectrum power of the first input signal to obtain an amplitude data set, and calculate the maximum value, the index corresponding to the maximum value, and the average value in the amplitude data set; S13. Compare the N-times average value with the maximum value. If the N-times average value is less than the maximum value, determine that the modulation type of the input signal is QPSK. If the N-times average value is greater than or equal to the maximum value, determine that the modulation type of the input signal is 8PSK. S14. When the modulation type of the input signal is QPSK, M is 4; when the modulation type of the input signal is 8PSK, M is 8.

3. The method for identifying and demodulating QPSK and 8PSK according to claim 1, wherein: The initial setting value of the search step value step is step=1 / L. Each time the search step value is updated, the updated search step value is set to half of the current search step value.

4. The method for identifying and demodulating QPSK and 8PSK according to claim 1, wherein: When the modulation type of the input signal is QPSK, the specific process of step S4 is: S41, calculating the maximum phase value corresponding to the frequency-free signal, and calculating the absolute value of the difference between the maximum phase value and π; S42, determining whether the absolute value of the difference is less than a second threshold; if the absolute value of the difference is less than or equal to the second threshold, rotating the frequency-offset-free signal by π / 8 to obtain a frequency-offset-free corrected signal; S43, repeating steps S41-S42 for the frequency-offset-free correction signal until the absolute value of the difference is greater than a second threshold, and then outputting a final frequency-offset-free signal; S44. Number the final frequency-offset-free signal on the constellation diagram, calculate the position of the final frequency-offset-free signal on the standard constellation diagram without phase offset, and obtain the standard signal without phase offset.

5. The method for identifying and demodulating QPSK and 8PSK according to claim 1, wherein: The specific calculation process of calculating the phase-bias-free standard signal SigR(n) is as follows: calculate Sig1(n) represents a signal with no frequency deviation; Round Sig2(n) to obtain the number z(n) of the frequency-free signal on the constellation diagram: z(n)=round(angle(Sig2(n))·Factor) Factor=M / 2π According to z(n), the standard signal without phase deviation SigR(n) is obtained: Wherein, j represents an imaginary unit, M represents a corresponding value determined according to the modulation type of the input signal, and round represents rounding to the nearest integer.

6. The method for identifying and demodulating QPSK and 8PSK according to claim 5, wherein: Before calculating the phase-bias-free standard signal SigR(n) based on z(n), z(n) is corrected. The correction method is: add M to each number smaller than 0 in z(n).

7. The method for identifying and demodulating QPSK and 8PSK according to claim 5, wherein: The specific process of correcting the phase deviation in step S5 is as follows: It is determined whether there is a value α greater than π in the phase deviation. If α exists, the value α is corrected to α-2π.

8. A system for QPSK and 8PSK identification and demodulation, characterized in that: include: Frequency offset estimation and compensation module, specifically including: The signal recognition module is used to obtain the input signal that has completed clock synchronization and identify the modulation type of the input signal, which includes 8PSK and QPSK; Perform M-th power calculation on the input signal according to the modulation type, where the value of M corresponds to the modulation type, and calculate the index MaxIdx corresponding to the maximum value of the amplitude spectrum power of the input signal after the M-th power calculation; The frequency offset rough estimation module is used to calculate the rough estimated frequency offset frequency point corresponding to the index MaxIdx; The frequency offset estimation module is used to calculate the compensation signal corresponding to the coarse frequency offset point and the frequency point value corresponding to the maximum phase difference value of the compensation signal; The frequency offset compensation module is used to perform frequency compensation on the input signal using the frequency point value to obtain a signal without frequency offset; The specific process of obtaining a frequency-free signal is as follows: According to the index MaxIdx corresponding to the maximum value, calculate the rough estimated frequency offset point corresponding to the index MaxIdx L represents the data length of the input signal; Calculate the compensation signal S0(n) corresponding to the coarse-estimated frequency offset point EF, and calculate the maximum phase difference value P0 corresponding to the coarse-estimated frequency offset point EF based on the compensation signal; Set the search step value, find the left and right frequency points on both sides of the rough estimated frequency offset point according to the search step value, calculate the compensation signal and the maximum phase difference value of the left and right frequency points respectively, and obtain the compensation signal S corresponding to the left frequency point. l and the maximum phase difference value P l , the compensation signal S corresponding to the right frequency point r and the maximum phase difference value P r ; From the maximum phase difference value P0, the maximum phase difference value P l and the maximum phase difference value P r Select the largest value as P max , update the frequency value of the rough estimated frequency offset point EF to P max Corresponding frequency value; Update the search step value and reset the search step value, repeat the above process of updating the frequency value of the rough estimated frequency offset frequency point according to the search step value, until the search step value reaches the preset threshold value and outputs the compensation frequency F corresponding to the rough estimated frequency offset frequency point EF est ; According to the compensation frequency F est Calculate the compensation frequency deviation and use it to compensate the input signal to obtain a signal without frequency deviation; Phase deviation estimation and compensation module, specifically including: The constellation diagram numbering and standard signal calculation module is used to calculate the position of the frequency-free signal corresponding to each point on the constellation diagram on the standard constellation diagram without phase deviation, and obtain the standard signal without phase deviation; The phase deviation estimation and compensation module is used to calculate the phase deviation between the standard signal without phase deviation and the signal without frequency deviation, correct the phase deviation, take the average of the corrected phase deviation to obtain the phase deviation to be compensated, and compensate the phase deviation of the signal without frequency deviation based on the phase deviation to obtain a signal without phase deviation.

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