CN111200569A - Broadband signal detection and identification method and device - Google Patents
Broadband signal detection and identification method and device Download PDFInfo
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Abstract
The invention discloses a method and a device for detecting and identifying broadband signals, comprising the following steps: carrying out analog-to-digital conversion on a sampled and received broadband signal and then carrying out multi-stage digital channelized filtering processing on the broadband signal; performing frequency spectrum splicing and smoothing on the filtered signals; detecting the frequency and bandwidth of the independent frequency point of the signal by adopting a channel threshold judgment mode, and removing harmonic frequency from the signal to obtain the frequency and bandwidth of the broadband signal which meet the actual requirements; extracting characteristic parameters of the signals after the elimination processing, comparing the characteristic parameters with a preset threshold value, and determining a modulation mode of the signals in the effective channel according to a comparison result; and outputting the frequency and bandwidth of the broadband signal obtained by detection and the identification result of the signal modulation mode. The invention can efficiently realize the frequency measurement and the bandwidth measurement of the broadband signal, and can realize the identification of the analog/digital modulation mode of the broadband signal without any prior knowledge. Moreover, the whole implementation scheme has the advantages of low computation amount, less occupied processing resources and the like.
Description
Technical Field
The invention relates to the technical field of signal processing, in particular to a method and a device for detecting and identifying broadband signals.
Background
With the development of communication technology, the bandwidth of signals applied in the wireless communication field is larger and larger, and the modulation types of the signals are diversified. In the field of electronic reconnaissance, a reconnaissance receiver is designed to acquire information of an intercepted signal. In the process of acquiring the intercepted signal, the reconnaissance receiver has to have real-time processing capability and can process a large-bandwidth signal in the face of a complex electromagnetic environment.
The spy receiver generally includes both types of analog signal receivers and digital signal receivers. Analog signal receivers are gradually replaced by digital signal receivers due to their poor environmental suitability. The software radio technology is widely applied to the design of a digital signal receiver due to the characteristics of wide application range, strong hardware universality, medium-frequency broadband, functional software, software modularization and the like.
The technical implementation schemes adopted by the current digital signal receiver are numerous. In terms of detection identification functions, attention is often paid to single detection identification functions such as pulse width measurement, frequency measurement, signal modulation pattern identification, and the like. And each implementation scheme has advantages and disadvantages. Some research results are only limited to algorithm simulation, and practical implementation has a plurality of limitations. For the identification of most modulation patterns, the identification type thereof usually only relates to digital modulation patterns, and for the extraction of characteristic parameters in some implementations of modulation pattern identification, a priori knowledge is also required.
In summary, in a signal receiver, the existing implementation schemes for detecting and identifying broadband signals have the disadvantages of single function and complex implementation manners, so that the detection and identification of broadband signals cannot be conveniently and quickly implemented.
Disclosure of Invention
The invention aims to provide a method and a device for detecting and identifying broadband signals, so as to conveniently and efficiently finish the detection and identification processing of the broadband signals.
The purpose of the invention is realized by the following technical scheme:
a broadband signal detection and identification method comprises the following steps:
after analog-to-digital conversion is carried out on the broadband signals received by sampling, multi-stage digital channelized filtering processing is carried out on the broadband signals;
performing frequency spectrum splicing and smoothing on the filtered signals, wherein the frequency spectrum splicing operation is only performed on the passband region signals, and the smoothing is realized by adopting a sliding mean filtering mode with a fixed window length;
detecting the frequency and bandwidth of the independent frequency point of the signal by adopting a channel threshold judgment mode, and removing harmonic frequency from the signal to obtain the frequency and bandwidth of the broadband signal which are in line with the actual frequency and bandwidth;
and identifying the signal modulation mode of the signal after the rejection processing, wherein the identification operation comprises the following steps: extracting characteristic parameters of signals, comparing the characteristic parameters with preset threshold values of the characteristic parameters, and determining a modulation mode of the signals in an effective channel according to a comparison result, wherein the effective channel is a sub-channel where the frequency of the detected broadband signals is located;
and outputting the frequency and bandwidth of the broadband signal obtained by detection and the identification result of the signal modulation mode.
The filtering process of the multi-stage digital channelization comprises the following steps:
after M times of data extraction is carried out on the sampling signals, the sampling signals parallelly enter a K-level uniform band-pass filter to be subjected to channelized filtering processing, K is 2M, and half of overlapping exists in the passband frequency domain of adjacent level filters.
The step of detecting the frequency and the bandwidth of the signal independent frequency point comprises the following steps:
determining each subchannel threshold value according to the power spectrum of each smoothed subchannel signal and a set signal capture threshold value, determining the frequency range of each independent frequency point according to the subchannel threshold value, and determining the signals with the frequency spacing within 25KHz as the frequency range of the same independent frequency point;
and determining the frequency value of the independent frequency point meeting the requirement for the frequency signal detected in each sub-channel according to the set condition, and determining the bandwidth of the independent frequency point according to the frequency range of each independent frequency point.
The step of performing harmonic frequency rejection processing on the signal comprises the following steps:
according to the set frequency deviation parameter of the independent frequency points, n-order harmonic frequency components and the bandwidth thereof are removed from the determined frequency and bandwidth of each independent frequency point, wherein n is an integer greater than 1.
In the process of identifying the signal modulation mode, the extracted characteristic parameters of the signal specifically include:
first order absolute origin moment of zero-center normalized instantaneous amplitude: absEnv ═ E (| Acn)i|)；
First order absolute central moments of the absolute value of the zero-center normalized instantaneous amplitude: absEnv2 ═ E (| B)i-E(Bi)|)
First-order absolute origin moment of zero-center normalized mean filter instantaneous frequency: absFreqm ═ E (Fm 2)i)
First-order absolute central moments of zero-center normalized mean filter instantaneous frequencies: abSFreqm2 ═ E (| Fm 2)i-E(Fm2i)|)；
Maximum value of zero-center normalized instantaneous amplitude spectral density:
wherein the content of the first and second substances,
Bi＝|Acni|
Aiis the instantaneous amplitude of the signal; fmiThe nonlinear instantaneous frequency after mean filtering; FFT _ n is the number of points of fast Fourier transform; e (-) is the expected operation function of the vector; max (-) is the maximum arithmetic function of the vector; min (-) is the minimum operation function of the vector; FFT (-) is a fast Fourier transform operator function of the vector.
In the process of identifying the signal modulation mode, the preset threshold values of the characteristic parameters respectively include:
absEnv _ Thre1 was 0.4; absEnv _ Thre2 was 0.18; absEnv2_ Thre1 was 0.23; absEnv2_ Thre2 was 0.17; absFreqm _ Thre1 was 0.2; absFreqm2_ Thre1 is 0.1; absFreqm2_ Thre2 is 0.2; ymax _ Thre1 is 1.7X 104；
And, the process of determining the modulation mode of the signal in the effective channel based on the threshold value includes:
if the characteristic parameter of the signal satisfies
The modulation mode of the signal is CW;
if the characteristic parameter of the signal satisfies
The modulation mode of the signal is AM;
if the characteristic parameter of the signal satisfies
The modulation mode of the signal is FM;
if the characteristic parameter of the signal satisfies
The modulation mode of the signal is 2 PSK;
if the characteristic parameter of the signal satisfies
The modulation mode of the signal is 4 PSK;
if the characteristic parameter of the signal satisfies
The modulation mode of the signal is 2 FSK;
if the characteristic parameter of the signal satisfies
The modulation mode of the signal is 4 FSK;
if the characteristic parameter of the signal satisfies
The modulation mode of the signal is 2 ASK;
if the characteristic parameter of the signal satisfies
The modulation mode of the signal is 4 ASK.
A broadband signal detection identification apparatus comprising:
the AD sampling module is used for carrying out analog-to-digital conversion processing on the sampled and received broadband signals;
the signal preprocessing module is used for carrying out multi-stage digital channelized filtering processing on the signals processed by the AD sampling module and carrying out frequency spectrum splicing and smoothing processing on the signals after the filtering processing, the frequency spectrum splicing operation is only carried out on passband area signals, and the smoothing processing is realized by adopting a sliding mean value filtering mode with a fixed window length;
the signal detection module is used for detecting the frequency and the bandwidth of the independent frequency points of the signals processed by the signal preprocessing module and eliminating the harmonic frequency of the signals to obtain the frequency and the bandwidth of the broadband signals which are in accordance with the actual signals;
the signal modulation mode identification module is used for identifying the signal modulation mode of the signal which is subjected to rejection processing by the signal detection module, and the identification operation comprises the following steps: extracting characteristic parameters of the signals, comparing the characteristic parameters with a preset threshold value, and determining a modulation mode of the signals in an effective channel according to a comparison result, wherein the effective channel is a sub-channel where the frequency of the obtained broadband signals is detected;
and the result display module is used for outputting the frequency and the bandwidth of the detected broadband signal and the identification result of the signal modulation mode.
The signal preprocessing module comprises a K-level digital channelization module and a frequency splicing and smoothing module, wherein the K-level digital channelization module is used for enabling a sampling signal to enter a K-level uniform band-pass filter for digital channelization filtering after M times of data are extracted, K is 2M, and half of overlapping exists between passband frequency domains of adjacent level filters.
The signal detection module comprises a signal frequency measurement module, a signal bandwidth measurement module and a harmonic frequency elimination module; the signal frequency measurement module is used for determining each subchannel threshold value according to the smoothed power spectrum of each subchannel signal and the set signal capture threshold value, determining the frequency range of each independent frequency point according to the subchannel threshold value, specifically determining the signal with the frequency spacing within 25KHz as the frequency range of the same independent frequency point, and further determining the frequency value of each independent frequency point in the determined frequency range; and the signal bandwidth measuring module is used for determining the bandwidth of each independent frequency point according to the frequency range of each independent frequency point.
The harmonic frequency eliminating module is used for eliminating n-order harmonic frequency components and the bandwidth thereof from the determined frequency and bandwidth of each independent frequency point according to the set frequency offset parameter of the independent frequency point, wherein n is an integer greater than 1.
According to the technical scheme provided by the invention, the method and the device for detecting and identifying the broadband signal can efficiently realize frequency measurement and bandwidth measurement of the broadband signal, and can realize identification of an analog/digital modulation mode of the broadband signal without any priori knowledge. The whole implementation scheme has the advantages of low computation amount, less occupied processing resources and the like, and is convenient for real-time detection, identification and processing of broadband signals.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.
FIG. 1 is a schematic block diagram of a method provided by an embodiment of the invention;
fig. 2 is a block diagram of a processing structure of a K-level digital channelization module according to an embodiment of the present invention;
fig. 3 is a schematic diagram of a spectrum and a threshold after channelization in a signal detection module according to an embodiment of the present invention;
fig. 4 is a flowchart of a signal modulation pattern recognition decision scheme according to an embodiment of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention are clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments of the present invention without making any creative effort, shall fall within the protection scope of the present invention.
The embodiment of the invention provides a broadband signal detection and identification method, which mainly comprises the following steps:
specifically, the received wideband signal may be AD-converted at a high sampling rate Fs (e.g. 250MHz, etc.) to obtain a sampling signal x (N), where N is 1,2,3, … …, and N is the number of sampling points;
further, the number K and the bandwidth Bw of all uniformly divided channels of the K-level digital channelization module and the multiple M of sub-channel data extraction may be determined, and K is 2M; designing a prototype low-pass filter to obtain a filter coefficient; and half of overlapping exists between the frequency domains of the sub-channels; then, taking x (n) as the input of the filter, and obtaining channelized output v by K-stage digital channelizingk(n) after M times of data extraction is carried out on the sampling signals, the sampling signals parallelly enter a K-level uniform band-pass filter to carry out digital channelized filtering processing;
in the step, in view of the spectrum symmetry of the channel, the spectrum of the output signal of the K/2 level channel is taken for spectrum splicing and smoothing; only operating the passband region of the channel spectrum during splicing, namely abandoning the transition region; in the process of smoothing the frequency spectrum, a sliding mean filtering method with fixed window length can be adopted;
the process of determining the frequency and bandwidth of each independent frequency point may include: determining each subchannel threshold value according to the smoothed power spectrum of each subchannel signal and the set signal capture threshold value, and determining the frequency range of the independent frequency point; and then, determining candidate detection frequency and bandwidth of the independent frequency point in the frequency range, and determining the final detection frequency and bandwidth of the broadband signal after harmonic frequency elimination.
Specifically, the step 4 may include: calculating a signal power spectrum threshold (namely the sub-channel threshold value) of each channel in the taken K/2-level channel, setting a minimum interval for distinguishing independent frequency points to be 25KHz, determining candidate detection frequency and bandwidth of the signal by adopting a threshold judgment and independent frequency point determination scheme, determining a frequency offset fixed value (namely a set frequency offset parameter of the independent frequency point), checking the candidate frequency item by item from small to large, eliminating n-th harmonic frequency components of the candidate frequency and the corresponding bandwidth thereof (n is a positive integer greater than 1), and taking the remaining frequency and the bandwidth thereof after checking as the final measurement frequency and the final bandwidth obtained by signal detection;
and 5, identifying a signal modulation mode, wherein the identification operation comprises the following steps: extracting characteristic parameters of the signals, comparing the characteristic parameters with a preset threshold value, and determining the modulation mode of the signals in the effective channel;
specifically, it is determined that the sub-channel where each independent frequency point is located is an effective channel, that is, the sub-channel where the frequency of the detected wideband signal in step 4 is located is an effective channel. Extracting characteristic parameters from output signals in the effective channel, comparing the magnitude relation between the corresponding characteristic parameters and the corresponding predetermined threshold values, and identifying the modulation mode of the signals in the effective channel according to a set characteristic threshold judgment mode;
Therefore, the technical scheme can realize frequency measurement and bandwidth measurement of the broadband communication signal in real time and efficiently, and realize identification of the analog/digital modulation mode.
The embodiment of the invention also provides a broadband signal detection and identification device, the implementation structure of which is shown in fig. 1, and the device specifically comprises an AD sampling module, a signal preprocessing module, a signal detection module, a signal identification module and a result display module, and broadband signal data sequentially passes through the modules to complete detection and identification processing for broadband signals. Wherein:
(1) the AD sampling module is used for carrying out analog-to-digital conversion processing on the sampled and received broadband signals;
(2) the signal preprocessing module is used for carrying out multi-stage digital channelized filtering processing on the signals processed by the AD sampling module and carrying out frequency spectrum splicing and smoothing processing on the signals after the filtering processing, the frequency spectrum splicing operation is only carried out on passband area signals, and the smoothing processing is realized by adopting a sliding mean value filtering mode with a fixed window length;
the signal preprocessing module further comprises a K-level digital channelization module and a frequency splicing and smoothing module, and the two modules are connected in sequence, wherein:
the K-level digital channelized filtering module adopts a data extraction structure based on multi-phase filtering to reduce the operation amount, and specifically, after M times of data extraction is carried out on a sampling signal, the sampling signal enters a K-level uniform band-pass filter in parallel to carry out filtering processing, and K is 2M; thus, filtering output of a half of symmetrical corresponding channels of the whole frequency domain, namely K/2-level channels, can be screened out and transmitted to a subsequent frequency spectrum splicing and smoothing module;
the frequency spectrum splicing and smoothing module comprises a frequency spectrum splicing module and a frequency spectrum smoothing module; the frequency spectrum splicing module sequentially splices the passband regions of the frequency spectrum of the output signal of the K/2-level channel filter according to the frequency order to form a whole frequency band for subsequent processing; the frequency spectrum smoothing module adopts a mean value filtering technology to carry out smoothing processing so as to weaken the influence of the barrier effect;
(3) the signal detection module is used for detecting the frequency and the bandwidth of the independent frequency point of the signal processed by the signal preprocessing module in a channel threshold judgment mode, and eliminating the harmonic frequency of the signal to obtain the frequency and the bandwidth of the broadband signal which meet the actual requirements;
the signal detection module comprises a signal frequency measurement module, a signal bandwidth measurement module and a harmonic frequency elimination module, and the modules are connected in sequence, wherein:
the signal frequency measurement module is used for determining each subchannel threshold value according to the smoothed power spectrum of each subchannel signal and the set signal capture threshold value, determining the frequency range of the independent frequency point according to the subchannel threshold value, and further determining the frequency value of the independent frequency point in the frequency range; for example, the average of the power spectrum of the signal within the channel may be combined with a signal capture threshold to determine each sub-channel threshold; after the frequency range of the independent frequency points is determined according to the subchannel threshold value, assuming that the minimum distance between two adjacent independent frequency points is 25KHz, regarding the frequency with the distance within the value as the frequency range of the same independent frequency point, and taking the middle value of the frequency range as the frequency value of the independent frequency point;
the signal bandwidth measuring module is used for determining the bandwidth of the independent frequency point according to the frequency range of the independent frequency point, namely the core of the module is to determine the frequency range of the independent frequency point as the bandwidth of the independent frequency point;
the harmonic frequency eliminating module is used for eliminating n-order harmonic frequency components and bandwidths thereof from the frequency and the bandwidth of the determined independent frequency point according to the frequency offset parameter (namely the predetermined allowable frequency offset range) of the set independent frequency point, wherein n is an integer greater than 1;
(4) the signal identification module mainly comprises a signal modulation mode identification module which is used for identifying and processing the modulation mode of the signal, and the signal modulation mode identification adopts a characteristic threshold judgment scheme to realize real-time accurate judgment;
specifically, the signal modulation mode identification module is mainly used for identifying the signal modulation mode of the signal after the signal detection module is subjected to rejection processing, and the identification operation includes: extracting characteristic parameters of the signals, comparing the characteristic parameters with a preset threshold value (or called characteristic parameter threshold), and determining the modulation mode of the signals in the effective channel according to the comparison result, namely determining the modulation mode of the signals in the effective channel according to the magnitude relation between the characteristic parameters and the characteristic parameter threshold; the effective channel is a sub-channel where the frequency of the detected broadband signal is located;
(5) and the result display module is used for outputting the frequency and the bandwidth of the detected broadband signal and the identification result of the signal modulation mode.
The scheme for realizing the detection and identification of the broadband signal based on the digital channelization provided by the embodiment of the invention can realize the frequency measurement and bandwidth measurement of the broadband wireless communication signal and the identification of the analog/digital modulation mode in real time efficiently with low resource consumption, low computation amount and no need of priori knowledge in the process of identifying the modulation mode. The implementation scheme can be applied to the implementation of the electronic reconnaissance and interference functions of uncooperative signals in the field of communication, and is suitable for being applied to platforms such as an FPGA (field programmable gate array) and a DSP (digital signal processor). And the frequency accuracy is +/-2 ppm, and the average recognition rate reaches 99% when the signal-to-noise ratio is 10dB or more.
The following description of the embodiments of the present invention will be made with reference to the accompanying drawings:
specifically, the present invention provides a technical solution for realizing detection and identification functions of broadband wireless signals in real time with low computation based on digital channelized filtering, as shown in fig. 1, the corresponding realization device may include an AD sampling module, a signal preprocessing module, a signal detection module, a signal identification module, and a result display module;
(1) and the AD sampling module is used for realizing conversion processing from the analog quantity of the received signal to the digital quantity.
(2) The signal preprocessing module further comprises a K-level digital channelization module and a frequency spectrum splicing and smoothing module; the K-level digital channelization module is implemented by using a data extraction structure based on polyphase filtering, and a specific implementation manner of the K-level digital channelization module is shown in fig. 2. Specifically, a high-speed data stream collected by a superior AD sampling module is received, and the high-speed data stream enters a multiphase filter bank after M times of data extraction. The polyphase filter bank is divided into K-level uniform band-pass filters, which are modulated by a prototype low-pass filter. M and K satisfy the relationship: k is 2M.
Specifically, let the coefficients of the prototype low-pass filter be:
hυ(n)＝{h(0)，h(1)，h(2)，......，h(N-1)}
the output of the K (K-0, 1, … …, K-1) th channel after data decimation and polyphase filtering is:
wherein
The frequency spectrum splicing and smoothing module further comprises a frequency spectrum splicing module and a frequency spectrum smoothing module; the frequency spectrum splicing module is used for splicing the frequency spectrums of the output signals of the sub-channels after the channelized filtering into the frequency spectrum of the whole frequency domain by taking the partial frequency of the passband of the band-pass filter according to the frequency sequence; the frequency spectrum smoothing module is provided with a smoothing window length, and adopts a rectangular window sliding mean filtering technology to realize frequency spectrum smoothing.
(3) The signal detection module further comprises a signal frequency measurement module, a channel bandwidth measurement module and a harmonic frequency elimination module;
the signal frequency measurement module is realized by adopting a channel threshold judgment technology and an independent frequency point determination technology;
specifically, if the signal acquisition threshold is ACQ _ thread, the Power spectrum of each subchannel signal after the spectrum smoothing is Power _ k, the calculation formula of the subchannel threshold Power _ thread is as follows:
Pcwer_Threk＝mean(Pcwer_k)×ACQ_Thre；
where mean (-) is the mean calculation function of the vector.
The schematic diagram of the spectrum and the threshold obtained after the sub-channel threshold is corresponding to the whole frequency domain is shown in fig. 3, and in fig. 3, the frequency range corresponding to the part higher than the threshold is the region where the frequency point is located. And determining the signals with the frequency spacing within 25KHz as the frequency range of the same independent frequency point, and taking the middle value of the frequency range as the frequency value of the independent frequency point.
The signal bandwidth measuring module is immediately behind the signal frequency measuring module, and the difference value between the maximum frequency and the minimum frequency in the frequency range of each independent frequency point is calculated to serve as the bandwidth of each independent frequency point.
The harmonic frequency eliminating module is the last process of the signal detection module. The harmonic frequency eliminating module is realized by adopting a numerical eliminating technology. Specifically, the frequency offset Freq _ offset of an independent frequency point (i.e. the allowable size of the frequency deviation obtained by the preset independent frequency point) is set, and the nth harmonic frequency component and the bandwidth thereof (n is a positive integer greater than 1) are removed from the obtained independent frequency point frequency and bandwidth.
After the harmonic component is removed by the harmonic frequency removing module, the rest signals are the frequency and the bandwidth of the signal which is finally detected and output.
(4) The signal identification module is mainly used for completing the function of signal modulation mode identification;
as shown in fig. 4, the specific signal modulation scheme-identified characteristic threshold decision scheme is designed as follows,
first, the following 5 feature parameters of the signal are extracted:
the first order absolute origin moment of zero-centered normalized instantaneous amplitude absEnv,
the first order absolute central moment absEnv2 of the absolute value of the zero-center normalized instantaneous amplitude,
the first-order absolute origin moment absFreqm of the zero-center normalized mean filter instantaneous frequency,
the first-order absolute central moment absFreqm2 of the zero-center normalized mean filtered instantaneous frequency,
the maximum value Ymax of the zero-center normalized instantaneous amplitude spectral density.
The calculation formula of each of the above 5 kinds of characteristic parameters is as follows:
Bi＝|Acni|
absEnv-E(|Acni|)
absEnv2-E(|Bi-E(Bi)|)
absFreqrn-E(Frn2i)
absFreqrn2-E(|Frn2i-E(Frn2i)|)
wherein A isiIs the instantaneous amplitude of the signal; fmiThe nonlinear instantaneous frequency after mean filtering; FFT _ n is the number of points of fast Fourier transform; e (-) is the expected operation function of the vector; max (-) is the maximum arithmetic function of the vector; min (-) is the minimum operation function of the vector; FFT (-) is a fast Fourier transform operator function of the vector.
Then, setting the thresholds of the characteristic parameters as follows: absEnv _ Thre1, absEnv _ Thre2, absEnv2_ Thre1, absEnv2_ Thre2, absFreqm _ Thre1, absFreqm2_ Thre1, absFreqm2_ Thre2, Ymax _ Thre1
Specifically, the thresholds of the characteristic parameters may be, but are not limited to, respectively set as:
absEnv _ Thre1 was 0.4; absEnv _ Thre2 was 0.18; absEnv2_ Thre1 was 0.23; absEnv2_ Thre2 was 0.17; absFreqm _ Thre1 was 0.2; absFreqm2_ Thre1 is 0.1; absFreqm2_ Thre2 is 0.2; ymax _ Thre1 is 1.7X 104。
When the method is implemented on an FPGA platform, the bit width of a numerical expansion needs to be set, and numerical fixed-point processing is carried out.
And finally, comparing the size relationship between the extracted signal characteristic parameters and the characteristic parameter thresholds, and determining a signal modulation mode according to the size relationship. And the modulation mode of the judging signal is an analog modulation mode or a digital modulation mode.
Specifically, the modulation mode of the signal that can be identified by the above technical solution may include, but is not limited to: CW, AM, FM, 2PSK, 4PSK, 2FSK, 4FSK, 2ASK, 4 ASK.
Specifically, the implementation manner of the corresponding determination of the modulation mode of the identification signal is as follows:
if the characteristic parameters of the signal satisfy:
the modulation mode of the signal is CW;
if the characteristic parameters of the signal satisfy:
the modulation mode of the signal is AM;
if the characteristic parameters of the signal satisfy:
the modulation mode of the signal is FM;
if the characteristic parameters of the signal satisfy:
the modulation mode of the signal is 2 PSK;
if the characteristic parameters of the signal satisfy:
the modulation mode of the signal is 4 PSK;
if the characteristic parameters of the signal satisfy:
the modulation mode of the signal is 2 FSK;
if the characteristic parameters of the signal satisfy:
the modulation mode of the signal is 4 FSK;
if the characteristic parameters of the signal satisfy:
the modulation mode of the signal is 2 ASK;
if the characteristic parameters of the signal satisfy:
the modulation mode of the signal is 4 ASK.
By the technical scheme provided by the embodiment of the invention, the accurate measurement of the signal bandwidth and frequency can be carried out in real time with lower computation under the condition of less occupied resources, and the identification processing of the signal modulation mode can be carried out simultaneously. According to experimental determination, by adopting the technical scheme provided by the embodiment of the invention, when the required accuracy is +/-2 ppm and the signal-to-noise ratio is 10dB or more, the average recognition rate can reach 99 percent, and thus, the detection and recognition requirements of broadband signals can be well met.
The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (10)
1. A method for detecting and identifying broadband signals is characterized by comprising the following steps:
carrying out analog-to-digital conversion on a sampled and received broadband signal and then carrying out multi-stage digital channelized filtering processing on the broadband signal;
performing frequency spectrum splicing and smoothing on the filtered signals, wherein the frequency spectrum splicing operation is only performed on the passband region signals, and the smoothing is realized by adopting a sliding mean filtering mode with a fixed window length;
detecting the frequency and bandwidth of the independent frequency point of the signal by adopting a channel threshold judgment mode, and removing harmonic frequency from the signal to obtain the frequency and bandwidth of the actual broadband signal;
and identifying the signal modulation mode of the signal after the rejection processing, wherein the identification operation comprises the following steps: extracting characteristic parameters of signals, comparing the characteristic parameters with preset threshold values of the characteristic parameters, and determining a modulation mode of the signals in an effective channel according to a comparison result, wherein the effective channel is a sub-channel where the frequency of the detected broadband signals is located;
and outputting the frequency and bandwidth of the broadband signal obtained by detection and the identification result of the signal modulation mode.
2. The method of claim 1, wherein the multi-stage filtering process for digital channelization comprises:
after M times of data extraction, the sampling signals parallelly enter a K-level uniform band-pass filter for channelized filtering processing, K is 2M, and half of overlapping exists between passband frequency domains of adjacent level filters.
3. The method according to claim 1, wherein the step of detecting the frequency and bandwidth of the independent signal frequency point comprises:
determining each subchannel threshold value according to the power spectrum of each smoothed subchannel signal and a set signal capture threshold value, determining the frequency range of each independent frequency point according to the subchannel threshold value, and determining the signals with the frequency spacing within 25KHz as the frequency range of the same independent frequency point;
and determining the frequency value of the independent frequency point meeting the requirement for the frequency signal detected in each sub-channel according to the set condition, and determining the bandwidth of the independent frequency point according to the frequency range of each independent frequency point.
4. The method of claim 1, wherein the step of performing harmonic frequency rejection processing on the signal comprises:
according to the set frequency deviation parameter of the independent frequency points, n-order harmonic frequency components and the bandwidth thereof are removed from the determined frequency and bandwidth of each independent frequency point, wherein n is an integer greater than 1.
5. The method according to any one of claims 1 to 4, wherein, in the signal modulation pattern recognition process, the extracted characteristic parameters of the signal specifically include:
first order absolute origin moment of zero-center normalized instantaneous amplitude: absEnv = E (| Acn)i|)；
First order absolute central moments of the absolute value of the zero-center normalized instantaneous amplitude: absEnv2= E (| Bi-E (B)i)|)
First-order absolute origin moment of zero-center normalized mean filter instantaneous frequency: absFreqm = E (Fm 2)i)
First-order absolute central moments of zero-center normalized mean filter instantaneous frequencies: absFreqm2= E (| Fm2i-E (Fm2i)|)；
Maximum value of zero-center normalized instantaneous amplitude spectral density:
wherein the content of the first and second substances,
Bi＝|Acni|
Aiis the instantaneous amplitude of the signal; fmiThe nonlinear instantaneous frequency after mean filtering; FFT _ n is the number of points of fast Fourier transform; e (-) is the expected operation function of the vector; max (-) is the maximum arithmetic function of the vector; min (-) is the minimum operation function of the vector; FFT (-) is a fast Fourier transform operator function of the vector.
6. The method of claim 5, wherein the predetermined threshold value of the characteristic parameter comprises:
absEnv _ Thre1 was 0.4; absEnv _ Thre2 was 0.18; absEnv2_ Thre1 was 0.23; absEnv2_ Thre2 was 0.17; absFreqm _ Thre1 was 0.2; absFreqm2_ Thre1 is 0.1; absFreqm2_ Thre2 is 0.2; ymax _ Thre1 is 1.7X 104；
And, the process of determining the modulation mode of the signal in the effective channel based on the threshold value includes:
if the characteristic parameter of the signal satisfies
The modulation mode of the signal is CW;
if the characteristic parameter of the signal satisfies
The modulation mode of the signal is AM;
if the characteristic parameter of the signal satisfies
The modulation mode of the signal is FM;
if the characteristic parameter of the signal satisfies
The modulation mode of the signal is 2 PSK;
if the characteristic parameter of the signal satisfies
The modulation mode of the signal is 4 PSK;
if the characteristic parameter of the signal satisfies
The modulation mode of the signal is 2 FSK;
if the characteristic parameter of the signal satisfies
The modulation mode of the signal is 4 FSK;
if the characteristic parameter of the signal satisfies
The modulation mode of the signal is 2 ASK;
if the characteristic parameter of the signal satisfies
The modulation mode of the signal is 4 ASK.
7. A wideband signal detection and identification device, comprising:
the AD sampling module is used for carrying out analog-to-digital conversion processing on the sampled and received broadband signals;
the signal preprocessing module is used for carrying out multi-stage digital channelized filtering processing on the signals processed by the AD sampling module and carrying out frequency spectrum splicing and smoothing processing on the signals after the filtering processing, the frequency spectrum splicing operation is only carried out on passband area signals, and the smoothing processing is realized by adopting a sliding mean value filtering mode with a fixed window length;
the signal detection module is used for detecting the frequency and the bandwidth of the independent frequency points of the signals processed by the signal preprocessing module in a channel threshold judgment mode, and eliminating harmonic frequencies of the signals to obtain the frequency and the bandwidth of the broadband signals meeting the actual requirements;
the signal modulation mode identification module is used for identifying the signal modulation mode of the signal which is subjected to rejection processing by the signal detection module, and the identification operation comprises the following steps: extracting characteristic parameters of the signals, comparing the characteristic parameters with a preset threshold value, and determining a modulation mode of the signals in an effective channel according to a comparison result, wherein the effective channel is a sub-channel where the frequency of the obtained broadband signals is detected;
and the result display module is used for outputting the frequency and the bandwidth of the detected broadband signal and the identification result of the signal modulation mode.
8. The device according to claim 7, wherein the signal preprocessing module comprises a K-level digital channelization module and a frequency splicing and smoothing module, wherein the K-level digital channelization module is configured to perform filtering processing of digital channelization by entering a K-level uniform band-pass filter in parallel after extracting M times of data from the sampled signal, and K is 2M, and half of overlapping exists between pass-band frequency domains of adjacent level filters.
9. The apparatus of claim 7 or 8, wherein the signal detection module comprises a signal frequency measurement module, a signal bandwidth measurement module, and a harmonic frequency rejection module; the signal frequency measurement module is used for determining each subchannel threshold value according to the smoothed power spectrum of each subchannel signal and the set signal capture threshold value, determining the frequency range of each independent frequency point according to the subchannel threshold value, specifically determining the signal with the frequency spacing within 25KHz as the frequency range of the same independent frequency point, and further determining the frequency value of each independent frequency point in the determined frequency range; and the signal bandwidth measuring module is used for determining the bandwidth of each independent frequency point according to the frequency range of each independent frequency point.
10. The device according to claim 9, wherein the harmonic frequency eliminating module is configured to eliminate n-th harmonic frequency components and bandwidths thereof from the determined frequency and bandwidth of each independent frequency point according to a set frequency offset parameter of the independent frequency point, where n is an integer greater than 1.
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