CN117201249A - Signal modulation mode identification method, system and device - Google Patents
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Abstract
The invention provides a signal modulation mode identification method, a system and a device, which belong to the technical field of signal processing, wherein the method comprises the following steps: collecting baseband IQ data for FM demodulation and outputting instantaneous frequency; estimating a signal code rate according to the instantaneous frequency, wherein if the signal code rate exists, the signal code rate is an FSK signal, otherwise, the signal code rate is an FM signal; dividing the instantaneous frequency into 64 intervals in sequence from large to small according to the amplitude of the instantaneous frequency, and calculating the instantaneous frequency point number of each interval; constructing a point sequence with the length of 64 according to the instantaneous frequency point number of each interval, and setting a threshold value of the point sequence; and determining the number of the extreme values according to the threshold value of the point sequence, and determining the modulation order of the FSK signal according to the number of the extreme values. The invention effectively improves the recognition efficiency of the FM and FSK signal modulation modes, and realizes that the order of the FSK signal can be recognized well under the condition of smaller modulation coefficient.
Description
Technical Field
The present invention relates to the field of signal processing technologies, and in particular, to a method, a system, and an apparatus for identifying a signal modulation mode.
Background
The signal monitoring and recognition mainly aims at real-time monitoring of a communication frequency spectrum in a specified frequency band, acquires relevant parameters, recognizes a modulation mode, determines signal portraits through a plurality of parameters, monitors whether illegal signals are detected, prevents illegal users from occupying and interfering the frequency spectrum, and achieves the aim of ensuring normal legal communication. In the field of communication application, the monitoring and recognition system is mostly composed of three parts, namely a receiving input stage (signal receiving and down-conversion), a modulation recognition (modulation mode classification) and an output stage (demodulation and information extraction), so that it can be seen that the modulation mode recognition is an important link between input and output, and the judgment result directly affects the subsequent steps of demodulation, information extraction and the like. FM modulation, which is one of analog modulation schemes, and FSK modulation, which is one of digital modulation schemes, are widely used in various communication fields. For example, the stereo broadcasting adopts FM modulation, and the DMR protocol adopts a 4FSK modulation scheme. Therefore, the modulation mode distinction of the FM signal and the FSK signal has higher practical significance.
In the prior art, the distinction between FM and FSK signals is typically accomplished by constructing a fourth order moment characteristic parameter that normalizes the zero center instantaneous frequency. However, constructing the fourth moment of normalized zero center instantaneous frequency requires obtaining the code rate of the signal, which increases a certain computational complexity. In addition, an appropriate threshold needs to be set to distinguish the FM signal from the FSK signal, and the success rate of the modulation mode identification is reduced due to the fact that the inappropriate threshold value.
In addition, the current modulation order identification scheme for the FSK signal is mainly implemented by the maximum value of the square spectrum of the number FSK signal, but the method has the following problems:
1. the signal needs to be subjected to square spectrum and fourier transform operations, which have high computational complexity.
3. The method has the advantages that the influence of the modulation index is larger, when the modulation index is smaller than 1, the number of the spectrum peaks of the FSK signal power spectrum is not ideal corresponding to the modulation order, namely 2 spectrum peaks appear in 2FSK, and 4 spectrum peaks appear in 4 FSK. But rather, a mutual superposition between adjacent spectral peaks occurs, thereby causing difficulty in statistical spectral peak estimation. Although the modulation index of the FSK signal is doubled after square conversion, the FSK signal still cannot be used for signals with the modulation index smaller than 0.5.
Disclosure of Invention
Aiming at the problems, the invention aims to provide a signal modulation mode identification method, a system and a device, which effectively improve the identification efficiency of FM and FSK signal modulation modes and realize that the order of the FSK signal can be better identified under the condition of smaller modulation coefficient.
The invention aims to achieve the aim, and the aim is achieved by the following technical scheme: a signal modulation mode identification method comprises the following steps:
s1: collecting baseband IQ data for FM demodulation and outputting instantaneous frequency;
s2: estimating a signal code rate according to the instantaneous frequency, wherein if the signal code rate exists, the signal modulation mode is FSK, otherwise, the signal modulation mode is FM;
s3: dividing the instantaneous frequency into 64 intervals in sequence from large to small according to the amplitude of the instantaneous frequency, and calculating the instantaneous frequency point number of each interval;
s4: constructing a point sequence with the length of 64 according to the instantaneous frequency point number of each interval, and setting a threshold value of the point sequence;
s5: and determining the number of the extreme values according to the threshold value of the point sequence, and determining the modulation order of the FSK signal according to the number of the extreme values.
Further, the step S1 includes:
collecting I-path data and Q-path data of a baseband to perform FM demodulation;
using the formulaObtaining the instantaneous frequency +.>；
Where n=1, … …, NS,is an in-phase component>For quadrature components, NS is the number of sampling points.
Further, the step S2 includes:
the minimum value of the instantaneous frequency f (n) is denoted as min_freq;
subtracting min_freq from each instantaneous frequency f (n), and setting the calculated instantaneous frequency value to be a positive value to obtain an instantaneous frequency sequence freq with the length of NS-1;
summing the instantaneous frequency sequences freq according to step length step to obtain instantaneous frequency sequences freq_temp with the lengths of (NS-1)/step respectively; wherein step=1, 2,3,4, the instantaneous frequency sequence freq_temp totals 4 groups;
calculating the peak-to-average ratio of each group of sequences freq_temp, and marking the instantaneous frequency sequence with the maximum peak-to-average ratio as freq_temp0;
the demodulation result of freq temp0 is multiplied by its delay component, and the corresponding result is denoted as power_freq.
Further, the step S2 further comprises
Performing fft computation on the power_freq, and performing left-right exchange of the fftshift to obtain a corresponding frequency spectrum fft_power_freq;
determining the maximum value in the frequency spectrum fft_power_freq as max_fft_power_freq;
the max_fft_power_freq 0.5 times is set as a threshold value, and sequences larger than the threshold value are screened out from the max_fft_power_freq and are marked as maximum value sequences peak_val.
Further, the step S2 further includes:
performing difference operation on the index value of each maximum value to obtain a difference sequence diff_peak_val;
if the values of the difference sequences diff_peak_val are equal, the signal modulation mode is FM, otherwise, the signal modulation mode is FSK.
Further, the step S3 includes,
the calculation process of the instantaneous frequency point number sequence count of each interval is specifically as follows:
temp_1=63×freq
temp_2=63×63×32768×freq
temp_3= fix(temp_2/max(temp_1))
count(fix(temp_3(n)/32768)+1) = count(fix(temp_3(n)/32768)+1)+1；
where n=1, … …, length (temp_3).
Further, the step S4 includes: the maximum value of the instantaneous frequency point number sequence count is set to 0.5 times the threshold value threshold.
Further, the step S5 includes:
counting the number count_peak of the modulated signal point number sequence count greater than the threshold value threshold;
if count_peak <3, the modulation mode is 2FSK;
if 3< count_peak <6, the modulation mode is 4FSK;
if count_peak >6, the modulation scheme is 8FSK.
Correspondingly, the invention also discloses a signal modulation identification system, which comprises:
the acquisition unit is configured to acquire baseband IQ data for FM demodulation and output instantaneous frequency;
the modulation mode identification unit is configured to determine a signal code rate according to the instantaneous frequency, if the signal code rate exists, the modulated signal is an FSK signal, otherwise, the modulated signal is an FM signal;
a point sequence calculating unit configured to divide the FSK signal into 64 sections in order from large to small according to its amplitude, and calculate instantaneous frequency points of each section;
a setting unit configured to construct a point sequence with a length of 64 according to the instantaneous frequency point number of each section, and set a threshold value of the instantaneous frequency point sequence;
the modulation order judging unit is configured to determine the number of the extreme values of the point sequence of the modulation signal according to the threshold value of the point sequence, and determine the modulation order of the FSK signal according to the number of the extreme values.
Correspondingly, the invention discloses a signal modulation mode identification device, which comprises:
the memory is used for storing a signal modulation mode identification program;
and the processor is used for realizing the steps of the signal modulation mode identification method when executing the signal modulation mode identification program.
Compared with the prior art, the invention has the beneficial effects that: the invention discloses a signal modulation mode identification method, a system and a device, comprising the following steps: collecting baseband IQ data to perform FM demodulation and output instantaneous frequency; estimating the signal code rate, if the code rate exists, judging the signal as an FSK signal, otherwise, judging the signal as an FM signal; dividing the instantaneous frequency into 64 intervals according to the order of magnitude from large to small; calculating the number of points of the modulation signal in each interval, and constructing a point sequence with the length of 64; calculating the maximum value of the point sequence; and outputting the modulation order of the FSK signal according to the maximum number. The invention can realize the identification of the signal modulation mode without knowing priori knowledge of the signal, such as carrier frequency, initial phase, symbol rate and the like, and effectively improves the identification efficiency of the FM and FSK signal modulation modes; and the order of the FSK signal can be well identified under the condition of smaller modulation coefficient.
It can be seen that the present invention has outstanding substantial features and significant advances over the prior art, as well as the benefits of its implementation.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required to be used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only embodiments of the present invention, and that other drawings can be obtained according to the provided drawings without inventive effort for a person skilled in the art.
FIG. 1 is a flow chart of a method of an embodiment of the present invention.
Fig. 2 is a schematic square diagram of a modulated signal according to an embodiment of the present invention.
Fig. 3 is a schematic diagram of a spectrum fft_power_freq according to an embodiment of the present invention.
Fig. 4 is a schematic diagram of the number of instantaneous frequency points in 64 intervals according to an embodiment of the present invention.
Fig. 5 is a system configuration diagram of an embodiment of the present invention.
In the figure, 1, an acquisition unit; 2. a modulation mode identification unit; 3. a point sequence calculation unit; 4. a setting unit; 5. modulation order determination unit.
Detailed Description
In order to better understand the aspects of the present invention, the present invention will be described in further detail with reference to the accompanying drawings and detailed description. It will be apparent that the described embodiments are only some, but not all, embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
Embodiment one:
as shown in fig. 1, the present invention provides a signal modulation recognition method, which includes the following steps:
s1: and collecting baseband IQ data for FM demodulation and outputting instantaneous frequency.
Specifically, firstly, I-path data and Q-path data of a baseband are collected to carry out FM demodulation; then use the formulaObtaining the instantaneous frequency +.>；
Where n=1, … …, NS,is an in-phase component>For quadrature components, NS is the number of sampling points.
S2: and determining the signal code rate according to the instantaneous frequency, wherein if the signal code rate exists, the signal is an FSK signal, and otherwise, the signal is an FM signal.
In a specific embodiment, the specific implementation flow of this step is as follows:
1. the minimum value of instantaneous frequency min_freq=min (f (n)) is estimated, all instantaneous frequencies f (n) are subtracted by min_freq, the instantaneous frequency value is set to a positive value, and the sequence freq with the length of NS-1 is obtained.
2. The instantaneous frequency values are summed in step (step=1, 2,3, 4), i.e. the average value is subtracted from the sum of every step points, resulting in 4 sets of sequences freq_temp of length (NS-1)/step, respectively.
3. The peak-to-average ratio of each set of sequences freq_temp is calculated and the sequence freq_temp with the largest peak-to-average ratio is selected.
4. The demodulation result freq_temp (1:end-4) is multiplied by its delay component freq_temp (5:end) to obtain a corresponding result sequence power_freq.
5. And performing fft computation on the result sequence power_freq, and performing left-right exchange of fftshift to obtain a corresponding frequency spectrum fft_power_freq.
6. Finding out the maximum value max_fft_power_freq of the fft_power_freq, taking 0.5 times of the max_fft_power_freq as a threshold, and finding out the maximum value sequence peak_val larger than the threshold.
7. And carrying out difference operation on the index values of the maximum values to obtain a difference sequence diff_peak_val=peak_val (2:end) -peak_val (1:end-1), judging the modulation signal as an FM signal if the values of the sequence diff_peak_val are equal, otherwise, judging the modulation signal as an FSK signal.
S3: according to the amplitude of the FSK signal, the FSK signal is divided into 64 sections in order from large to small, and the instantaneous frequency point number of each section is calculated.
In a specific embodiment, a value of 63×freq is calculated first to obtain temp_1, a value of 63×63×32768×freq is calculated to obtain temp_2, and a value of fix (temp_2/max (temp_1)) is calculated to obtain temp_3.
Then, calculating the instant frequency point number sequence count in each interval, wherein the specific calculation method comprises the following steps: count (fix (temp_3 (n)/32768) +1) =count (fix (temp_3 (n)/32768) +1, n=1, … …, length (temp_3).
S4: and constructing a point sequence with the length of 64 according to the instantaneous frequency point number of each interval, and setting a threshold value of the sequence.
In a specific embodiment, 0.5 times the maximum value of the instantaneous frequency point number sequence count is set as the threshold value threshold.
S5: and determining the number of the extreme values of the instantaneous frequency point number sequence according to the threshold value, and determining the modulation order of the FSK signal according to the number of the extreme values.
In a specific embodiment, the number count_peak of the count instant frequency point number sequence count is greater than a threshold value threshold and is the maximum value in a certain range (the left and right index ranges are respectively 3). If count_peak <3, then the signal decision is 2FSK; if 3< count_peak <6, then the signal decision is 4FSK; if count_peak >6, then the signal decision is 8FSK.
To illustrate the effectiveness of the method of the present invention, a diagram of the various identification processes for a 4FSK signal with a frequency offset coefficient of 0.25 is provided below. Wherein, the signal code rate is 192KHz, and the sampling rate is 3.84MHz. The square spectrum of the adjusted signal is shown in fig. 2, and it is easy to see that the frequency offset coefficient is smaller, and the signal has no obvious spectrum peak, so that the order of the signal is difficult to identify; the fft_power_freq (step=2) obtained in step S2 is shown in fig. 3, and the order of the signal can be clearly identified; the number of points in each section calculated in step S4 is shown in fig. 4, and in fig. 4, it is obvious that there are four spectral peaks, that is, the modulation signal is 4FSK, so that the effectiveness of the method is fully illustrated.
Embodiment two:
based on the first embodiment, as shown in fig. 5, the invention also discloses a signal modulation mode identification system, which comprises: the device comprises an acquisition unit 1, a modulation mode identification unit 2, a point sequence calculation unit 3, a setting unit 4 and a modulation order judgment unit 5.
And the acquisition unit 1 is configured to acquire baseband IQ data for FM demodulation and output instantaneous frequency.
The modulation mode identification unit 2 is configured to determine a signal code rate according to the instantaneous frequency, if the signal code rate exists, the modulation signal is an FSK signal, and if not, the modulation signal is an FM signal.
The point sequence calculating unit 3 is configured to divide the FSK signal into 64 sections in order from large to small according to the amplitude thereof, and calculate the instantaneous frequency point number of each section.
A setting unit 4 configured to construct a point sequence of length 64 according to the instantaneous frequency point number of each section, and set a threshold value of the point sequence.
The modulation order determining unit 5 is configured to determine the number of extremums of the instantaneous frequency point sequence according to the threshold value of the point sequence, and determine the modulation order of the FSK signal according to the number of extremums.
Embodiment III:
the embodiment discloses a signal modulation mode identification device, which comprises a processor and a memory; the processor executes the signal modulation recognition program stored in the memory to realize the following steps:
1. and collecting baseband IQ data for FM demodulation and outputting instantaneous frequency.
2. And determining the signal code rate according to the instantaneous frequency, wherein if the signal code rate exists, the signal is an FSK signal, and otherwise, the signal is an FM signal.
3. According to the amplitude of the instantaneous frequency, it is divided into 64 sections in order from large to small, and the instantaneous frequency point number sequence of each section is calculated.
4. And constructing a point sequence with the length of 64 according to the instantaneous frequency point of each interval, and setting a threshold value of the instantaneous frequency point sequence.
5. And determining the number of the extreme values of the point sequence according to the threshold value of the point sequence, and determining the modulation order of the FSK signal according to the number of the extreme values.
In summary, the invention effectively improves the recognition efficiency of the FM and FSK signal modulation modes, and realizes that the order of the FSK signal can be recognized well under the condition of smaller modulation coefficient.
In this specification, each embodiment is described in a progressive manner, and each embodiment is mainly described in a different point from other embodiments, so that the same or similar parts between the embodiments are referred to each other. For the method disclosed in the embodiment, since it corresponds to the system disclosed in the embodiment, the description is relatively simple, and the relevant points refer to the description of the method section.
Those of skill would further appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both, and that the various illustrative elements and steps are described above generally in terms of functionality in order to clearly illustrate the interchangeability of hardware and software. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.
In the several embodiments provided by the present invention, it should be understood that the disclosed systems, and methods may be implemented in other ways. For example, the system embodiments described above are merely illustrative, e.g., the division of the elements is merely a logical functional division, and there may be additional divisions when actually implemented, e.g., multiple elements or components may be combined or integrated into another system, or some features may be omitted or not performed. Alternatively, the coupling or direct coupling or communication connection shown or discussed with each other may be through some interface, system or unit indirect coupling or communication connection, which may be in electrical, mechanical or other form.
The units described as separate units may or may not be physically separate, and units shown as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the solution of this embodiment.
In addition, each functional module in the embodiments of the present invention may be integrated in one processing unit, or each module may exist alone physically, or two or more modules may be integrated in one unit.
Similarly, each processing unit in the embodiments of the present invention may be integrated in one functional module, or each processing unit may exist physically, or two or more processing units may be integrated in one functional module.
The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. The software modules may be disposed in Random Access Memory (RAM), memory, read Only Memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.
Finally, it is further noted that relational terms such as first and second, and the like are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
The method, the system and the device for identifying the signal modulation provided by the invention are described in detail. The principles and embodiments of the present invention have been described herein with reference to specific examples, the description of which is intended only to facilitate an understanding of the method of the present invention and its core ideas. It should be noted that it will be apparent to those skilled in the art that various modifications and adaptations of the invention can be made without departing from the principles of the invention and these modifications and adaptations are intended to be within the scope of the invention as defined in the following claims.
Claims (10)
1. The signal modulation mode identification method is characterized by comprising the following steps:
s1: collecting baseband IQ data for FM demodulation and outputting instantaneous frequency;
s2: determining a signal code rate according to the instantaneous frequency, wherein if the signal code rate exists, the signal modulation mode is FSK, otherwise, the signal modulation mode is FM;
s3: dividing the instantaneous frequency into 64 intervals in sequence from large to small according to the amplitude of the instantaneous frequency, and calculating the instantaneous frequency point number of each interval;
s4: constructing a point sequence with the length of 64 according to the instantaneous frequency point number of each interval, and setting a threshold value of the sequence;
s5: and determining the number of the extreme values of the instantaneous frequency point number sequence according to the threshold value, and determining the modulation order of the FSK signal according to the number of the extreme values.
2. The method for identifying a signal modulation scheme according to claim 1, wherein said step S1 comprises:
collecting I-path data and Q-path data of a baseband to perform FM demodulation;
using the formulaObtaining the instantaneous frequency +.>；
Where n=1, … …, NS,is an in-phase component>For quadrature components, NS is the number of sampling points.
3. The method for identifying a signal modulation scheme according to claim 1, wherein said step S2 comprises:
the minimum value of the instantaneous frequency f (n) is denoted as min_freq;
subtracting min_freq from each instantaneous frequency f (n), and setting the calculated instantaneous frequency value to be a positive value to obtain an instantaneous frequency sequence freq with the length of NS-1;
summing the instantaneous frequency sequences freq according to step length step to obtain instantaneous frequency sequences freq_temp with the lengths of (NS-1)/step respectively; wherein step=1, 2,3,4, the instantaneous frequency sequence freq_temp totals 4 groups;
calculating the peak-to-average ratio of each group of sequences freq_temp, and marking the instantaneous frequency sequence with the maximum peak-to-average ratio as freq_temp0;
the freq_temp0 (1:end-4) is multiplied by its delay component freq_temp0 (5:end), yielding the corresponding result denoted power_freq.
4. The method of signal modulation scheme identification according to claim 3 wherein said step S2 further comprises
Performing fft computation on the power_freq, and performing left-right exchange of the fftshift to obtain a corresponding frequency spectrum fft_power_freq;
determining the maximum value in the frequency spectrum fft_power_freq as max_fft_power_freq;
the max_fft_power_freq 0.5 times is set as a threshold value, and sequences larger than the threshold value are screened out from the max_fft_power_freq and are marked as maximum value sequences peak_val.
5. The method for identifying a signal modulation scheme according to claim 4, wherein said step S2 further comprises:
performing difference operation on the index value of each maximum value to obtain a difference sequence diff_peak_val;
if the values of the difference sequences diff_peak_val are equal, the signal modulation mode is FSK, otherwise, the signal modulation mode is FM.
6. The method for identifying a signal modulation scheme according to claim 5, wherein said step S3 comprises,
the calculation process of the instantaneous frequency point number sequence count of each interval is specifically as follows:
temp_1=63×freq
temp_2=63×63×32768×freq
temp_3= fix(temp_2/max(temp_1))
count(fix(temp_3(n)/32768)+1) = count(fix(temp_3(n)/32768)+1)+1；
where n=1, … …, length (temp_3).
7. The method for identifying a signal modulation scheme according to claim 6, wherein said step S4 comprises: the maximum value of the point sequence count is set to 0.5 times the threshold value threshold.
8. The method for identifying a signal modulation scheme according to claim 7, wherein said step S5 comprises:
counting the number count_peak of the instant frequency point number sequence count which is larger than the threshold value threshold;
if count_peak <3, the signal modulation mode is 2FSK;
if 3< count_peak <6, the signal modulation mode is 4FSK;
if count_peak >6, the signal modulation scheme is 8FSK.
9. A signal modulation scheme identification system, comprising:
the acquisition unit is configured to acquire baseband IQ data for FM demodulation and output instantaneous frequency;
the modulation mode identification unit is configured to determine a signal code rate according to the instantaneous frequency, if the signal code rate exists, the signal modulation mode is FSK, otherwise, the signal modulation mode is FM;
a point sequence calculation unit configured to divide the instantaneous frequency into 64 sections in order from large to small according to the amplitude of the instantaneous frequency, and calculate the instantaneous frequency point of each section;
a setting unit, configured to construct a point sequence with a length of 64 according to the instantaneous frequency point number of each interval, and set a threshold value of the point sequence;
the modulation order judging unit is configured to determine the number of the extreme values of the point sequence according to the threshold value of the point sequence, and determine the modulation order of the FSK signal according to the number of the extreme values.
10. A signal modulation recognition apparatus, comprising:
a memory for storing a signal modulation recognition program;
a processor for implementing the steps of the signal modulation recognition method according to any one of claims 1 to 8 when executing said signal modulation recognition program.
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