CN115801030B - Carrier automatic search system and search method thereof - Google Patents
Carrier automatic search system and search method thereof Download PDFInfo
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Abstract
The invention discloses an automatic carrier searching system and a searching method thereof, which mainly solve the problems of high signal level dynamic range and relatively high false detection and missing detection probability of signal searching when the noise substrate energy is uneven. The system comprises a hardware control module, a receiver, an intermediate frequency preprocessing module, a digital acquisition system, a signal searching module, an output and output control module, a rear-end processing database and a network data sharing module. The system utilizes a receiver, an intermediate frequency preprocessing module and a digital acquisition system to complete the functions of signal receiving, down-conversion, filtering, gain control, intermediate frequency preprocessing, digital acquisition and the like, and intermediate frequency sampling data are obtained. The system sets and controls hardware according to search requirements, processes and detects the intermediate frequency digital signals, combines detection results with a rear-end database to analyze and mine, completes signal screening, discovers signal change rules, calculates signal occupancy rate, and finally achieves electromagnetic situation analysis of an observed object.
Description
Technical Field
The invention belongs to the technical field of mobile communication, and particularly relates to an automatic carrier searching system and a searching method thereof.
Background
Signal searching refers to finding a signal in a multidimensional space and multiple sample values, determining the presence of the signal according to a certain criterion, and simultaneously intercepting the detected signal samples by a proper length for estimating basic parameters of the signal, such as center frequency, bandwidth, and the like. Studies have shown that a signal can be determined entirely by the time domain, frequency domain, polarization domain and incoming wave direction domain. Different existence domains are considered for the same signal to obtain different results, and as the communication signals occupy different frequency channels as the largest and most prominent characteristics, signal searching is completed in the frequency domain in most cases, namely, in a wider observation frequency band, signal blind detection is performed under the condition that parameters such as the number of signals, carrier frequency, bandwidth and signal to noise ratio are unknown. The signal search is a precondition for implementing effective monitoring, high-efficiency interference and acquiring information, and has important significance in the field of electromagnetic spectrum monitoring. At present, two methods of manual signal searching and automatic signal searching are mainly adopted as the methods for signal searching.
The manual signal searching means that by means of instruments such as a frequency spectrograph, an oscilloscope, a vector analyzer, a receiver and the like, a professional with abundant experience observes the frequency spectrum distribution and monitors sound, and meanwhile, the frequency of the receiver is manually tuned, so that the signal is searched and detected in a specified frequency band. The method has the advantages of low false detection probability, low missing detection probability in a smaller search frequency band range and the like, and is still commonly adopted in actual work. However, the method has low working efficiency, complex operation procedure and high requirements on quality of staff, and is difficult to meet the increasingly complex electromagnetic signal monitoring requirements. Therefore, the automatic signal search method has become an important point of research in the aspect of signal search.
The automatic signal searching method, also called as electric scanning signal searching method, is generally based on the software radio idea, and on a general hardware platform, the time domain, frequency domain or time-frequency domain characteristics of the captured broadband data are analyzed and compared by using developed signal analysis processing software, so as to realize the automatic searching and finding of the signals. The method has high speed and high efficiency, and the false detection and missing detection probability of automatic signal search is lower under the condition that the background level of the channel is relatively flat and the signal change is relatively small. For example, the signal search in a normal satellite channel has a good practical application effect. However, for satellite signals in a specific area, the noise floor energy is uneven due to the large dynamic range of the signal level, and the false detection and miss probability of signal search is relatively high.
Disclosure of Invention
The invention aims to provide an automatic carrier searching system and a searching method thereof, which mainly solve the problems of high signal level dynamic range and relatively high false detection and missing detection probability of signal searching when the noise substrate energy is uneven.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
a carrier automatic search system, comprising:
the hardware control module receives a control instruction of system software to realize control of system hardware;
a receiver that receives a sampling signal;
the intermediate frequency preprocessing module is used for performing intermediate frequency preprocessing on the sampling signals;
the digital acquisition system is used for carrying out digital acquisition to obtain an intermediate frequency sampling signal;
the signal searching module sends a signal searching instruction to the hardware control module, and processes and detects the intermediate frequency sampling signal;
the input/output control module is used for controlling the input/output data transmission of the signal search module;
and the rear-end processing database is used for analyzing and mining the detection result and the rear-end database, finishing signal screening, finding out a signal change rule, counting the signal occupancy rate and realizing electromagnetic situation analysis of an observed object.
Further, the invention also comprises a network data sharing module which is used for sharing the detection result of the signal searching module and the analysis result of the back-end processing database.
Based on the searching system, the invention also provides a carrier automatic searching method, which comprises the following steps:
s1, performing power spectrum estimation on a search channel by adopting a multi-window spectrum estimation method; according to the actual receiver bandwidth, a sliding window method with a stepping center frequency is adopted to realize signal spectrum estimation, and then a complete spectrum is obtained through a channel frequency band splicing technology;
s2, carrying out continuous wavelet transformation on the power spectrum of the obtained signal;
s3, preliminarily determining singular points according to extreme points of the large-scale wavelet transformation coefficients: assuming Pi (n) is a wavelet transform coefficient of scale i, there are:
wherein Pi' (n) is a modular extreme point array of Pi (n), and M is a comparison range of the determined extreme points selected according to actual conditions;
s4, removing the pseudo singular point through windowing and summation: selecting a proper window function, respectively solving part of Pi (n) by taking a large-scale wavelet transformation extreme point Pi' (n) as a center to obtain Pi "(n), wherein if Pi" (n) is greater than a preset threshold, n is a singular point position, otherwise, is a pseudo singular point; namely:
s5, dividing the broadband spectrum into a plurality of sub-band spectrums according to the singular point positions obtained in the step S4, and calculating the average power of each sub-band spectrum;
s6, calculating a detection threshold according to the average power of each sub-band, comparing the detection threshold with a set threshold L, and judging whether the detection threshold carries signals or not, thereby finishing signal searching; wherein, the judging process is as follows: the system adopts three related decision thresholds to realize the search of a signal: search threshold l, amplitude threshold a and bandwidth threshold b; firstly, determining an area with signal energy exceeding a search threshold l as a suspicious signal, and then roughly estimating relevant parameters of the suspicious signal: the relative amplitude, the estimated bandwidth and the center frequency are compared with a preset amplitude threshold a and a preset bandwidth threshold b respectively, if the two thresholds exceed the corresponding threshold, the search signal can be judged, and otherwise, the search signal is judged as noise.
Further, in the step S6, the method for calculating the detection threshold is as follows:
firstly, 2N+1 sub-bands are selected by taking the sub-band k to be determined as the center, the average power of the sub-bands is subjected to sequencing operation, then the signals with larger power are removed, the average power of the noise is obtained by averaging the rest data, and the average power of the noise is added with an experience constant to be used as a detection threshold, namely:
wherein xi epsilon (0, 1) is the scale factor,representing a rounding down, a +.>Representation pair->The ascending order is performed, C represents an empirical constant, and N is a constant.
Compared with the prior art, the invention has the following beneficial effects:
(1) The invention utilizes the receiver, the intermediate frequency preprocessing module and the digital acquisition system to complete the functions of signal receiving, down-conversion, filtering, gain control, intermediate frequency preprocessing, digital acquisition and the like, and obtains intermediate frequency sampling data. Considering satellite signals with frequencies up to several GHz, the system digitizes the signals using intermediate frequency bandpass sampling in order to reduce the requirements on the acquisition module and to reduce the amount of subsequent operational data. The actual receiving bandwidth of the receiver is often far smaller than the designated searching bandwidth of the system, so the system adopts the idea of stepping segmented receiving, namely, searching the designated bandwidth segment by changing the center frequency of the receiver. The hardware control module is used for setting and controlling hardware according to search requirements, processing and detecting the intermediate frequency digital signals, analyzing and mining the detection results and the rear-end database, completing signal screening, finding out a signal change rule, counting the signal occupancy rate, and finally realizing electromagnetic situation analysis of an observed object, thereby realizing automatic search of signals.
(2) The minimum carrier-to-noise ratio and the minimum bandwidth of the search signal are respectively limited by the amplitude threshold and the bandwidth threshold in the search method, the search signal can be set according to some priori knowledge of the current electromagnetic background, and if the search signal is properly set, the false alarm probability can be reduced, and the reliability of the signal search result can be improved.
Drawings
Fig. 1 is a schematic structural view of the present invention.
Fig. 2 shows a spectrum of an actual satellite signal in an embodiment of the invention.
FIG. 3 is a graph showing the effect of the singular point detection algorithm in the embodiment of the present invention.
Detailed Description
The invention will be further illustrated by the following description and examples, which include but are not limited to the following examples.
Examples
As shown in fig. 1, the carrier automatic search system disclosed by the invention comprises a hardware control module, a receiver, an intermediate frequency preprocessing module, a digital acquisition system, a signal search module, an input/output control module, a back-end processing database and a network data sharing module. The system utilizes a receiver, an intermediate frequency preprocessing module and a digital acquisition system to complete the functions of signal receiving, down-conversion, filtering, gain control, intermediate frequency preprocessing, digital acquisition and the like, and intermediate frequency sampling data are obtained. Considering satellite signals with frequencies up to several GHz, the system digitizes the signals using intermediate frequency bandpass sampling in order to reduce the requirements on the acquisition module and to reduce the amount of subsequent operational data. The actual receiving bandwidth of the receiver is often far smaller than the designated searching bandwidth of the system, so the system adopts the idea of stepping segmented receiving, namely, searching the designated bandwidth segment by changing the center frequency of the receiver. The hardware control module is used for setting and controlling hardware according to search requirements, processing and detecting the intermediate frequency digital signals, analyzing and mining the detection results and the rear-end database, completing signal screening, finding out a signal change rule, counting the signal occupancy rate, and finally realizing electromagnetic situation analysis of an observed object, thereby realizing automatic search of signals.
And the system is also provided with a network data sharing module which is used for sharing the detection result of the signal searching module and the analysis result of the back-end processing database.
In this embodiment, the carrier automatic search method is as follows:
s1, performing power spectrum estimation on a search channel by adopting a multi-window spectrum estimation method; according to the actual receiver bandwidth, a sliding window method with a stepping center frequency is adopted to realize signal spectrum estimation, and then a complete spectrum is obtained through a channel frequency band splicing technology;
s2, carrying out continuous wavelet transformation on the power spectrum of the obtained signal;
s3, preliminarily determining singular points according to extreme points of the large-scale wavelet transformation coefficients: assuming Pi (n) is a wavelet transform coefficient of scale i, there are:
wherein Pi' (n) is a modular extreme point array of Pi (n), and M is a comparison range of the determined extreme points selected according to actual conditions;
s4, removing the pseudo singular point through windowing and summation: selecting a proper window function, respectively solving part of Pi (n) by taking a large-scale wavelet transformation extreme point Pi' (n) as a center to obtain Pi "(n), wherein if Pi" (n) is greater than a preset threshold, n is a singular point position, otherwise, is a pseudo singular point; namely:
s5, dividing the broadband spectrum into a plurality of sub-band spectrums according to the singular point positions obtained in the step S4, and calculating the average power of each sub-band spectrum;
s6, calculating a detection threshold according to the average power of each sub-band, comparing the detection threshold with a set threshold L, and judging whether the detection threshold carries signals or not, thereby finishing signal searching; wherein, the judging process is as follows: the system adopts three related decision thresholds to realize the search of a signal: search threshold l, amplitude threshold a and bandwidth threshold b; firstly, determining an area with signal energy exceeding a search threshold l as a suspicious signal, and then roughly estimating relevant parameters of the suspicious signal: the relative amplitude, the estimated bandwidth and the center frequency are compared with a preset amplitude threshold a and a preset bandwidth threshold b respectively, if the two thresholds exceed the corresponding threshold, the search signal can be judged, and otherwise, the search signal is judged as noise.
The method for calculating the detection threshold comprises the following steps:
firstly, 2N+1 sub-bands are selected by taking the sub-band k to be determined as the center, the average power of the sub-bands is subjected to sequencing operation, then the signals with larger power are removed, the average power of the noise is obtained by averaging the rest data, and the average power of the noise is added with an experience constant to be used as a detection threshold, namely:
wherein xi epsilon (0, 1) is the scale factor,representing a rounding down, a +.>Representation pair->The ascending order is performed, C represents an empirical constant, and N is a constant.
The minimum carrier-to-noise ratio and the minimum bandwidth of the search signal are respectively limited by the amplitude threshold and the bandwidth threshold, the current electromagnetic background can be set according to some priori knowledge, and if the current electromagnetic background is properly set, the false alarm probability can be reduced, and the reliability of the signal search result can be improved.
And comparing the performances of the two detection algorithms in an actual satellite signal environment. The experiment adopts C-band satellite signals intercepted by a third party receiver from a satellite in a certain area, and a part of signals with the center frequency of 4082MHz are intercepted. Fig. 2 shows a spectrum diagram of an intercepted signal, and it can be seen that the direction signal is obviously different from a satellite signal spectrum diagram under a normal channel environment, and a single threshold search signal cannot be simply adopted.
Fig. 3 shows the detection result obtained using a wavelet double noise suppressed signal detection algorithm. The method used by the scheme can be obtained through the effect graph, and has a good detection effect.
The above embodiment is only one of the preferred embodiments of the present invention, and should not be used to limit the scope of the present invention, but all the insubstantial modifications or color changes made in the main design concept and spirit of the present invention are still consistent with the present invention, and all the technical problems to be solved are included in the scope of the present invention.
Claims (4)
1. A carrier automatic search system, comprising:
the hardware control module receives a control instruction of system software to realize control of system hardware;
a receiver that receives a sampling signal;
the intermediate frequency preprocessing module is used for performing intermediate frequency preprocessing on the sampling signals;
the digital acquisition system is used for carrying out digital acquisition to obtain an intermediate frequency sampling signal;
the signal searching module sends a signal searching instruction to the hardware control module, and processes and detects the intermediate frequency sampling signal;
the input/output control module is used for controlling the input/output data transmission of the signal search module;
and the rear-end processing database is used for analyzing and mining the detection result and the rear-end database, finishing signal screening, finding out a signal change rule, counting the signal occupancy rate and realizing electromagnetic situation analysis of an observed object.
2. The carrier automatic search system according to claim 1, further comprising a network data sharing module for sharing the detection result of the signal search module and the analysis result of the back-end processing database.
3. The carrier automatic searching method is characterized in that the searching system as claimed in claim 2 is adopted, comprising the following steps:
s1, performing power spectrum estimation on a search channel by adopting a multi-window spectrum estimation method; according to the actual receiver bandwidth, a sliding window method with a stepping center frequency is adopted to realize signal spectrum estimation, and then a complete spectrum is obtained through a channel frequency band splicing technology;
s2, carrying out continuous wavelet transformation on the power spectrum of the obtained signal;
s3, preliminarily determining singular points according to extreme points of the large-scale wavelet transformation coefficients: assuming Pi (n) is a wavelet transform coefficient of scale i, there are:
wherein Pi' (n) is a modular extreme point array of Pi (n), and M is a comparison range of the determined extreme points selected according to actual conditions;
s4, removing the pseudo singular point through windowing and summation: selecting a proper window function, respectively solving part of Pi (n) by taking a large-scale wavelet transformation extreme point Pi ' (n) as a center to obtain Pi ' ' (n), wherein if the Pi ' ' (n) is larger than a preset threshold, n is a singular point position, otherwise, is a pseudo singular point; namely:
wherein N is a constant;
s5, dividing the broadband spectrum into a plurality of sub-band spectrums according to the singular point positions obtained in the step S4, and calculating the average power of each sub-band spectrum;
s6, calculating a detection threshold according to the average power of each sub-band, comparing the detection threshold with a set threshold L, and judging whether the detection threshold carries signals or not, thereby finishing signal searching; wherein, the judging process is as follows: the system adopts three related decision thresholds to realize the search of a signal: search threshold l, amplitude threshold a and bandwidth threshold b; firstly, determining an area with signal energy exceeding a search threshold l as a suspicious signal, and then estimating relevant parameters of the suspicious signal: the relative amplitude, the estimated bandwidth and the center frequency are compared with a preset amplitude threshold a and a preset bandwidth threshold b respectively, if the two thresholds exceed the corresponding threshold, the search signal can be judged, and otherwise, the search signal is judged as noise.
4. The automatic carrier searching method according to claim 3, wherein in the step S6, the detection threshold calculating method is as follows:
firstly, 2N+1 sub-bands are selected by taking the sub-band k to be determined as the center, the average power of the sub-bands is subjected to sequencing operation, then the signals with larger power are removed, the average power of the noise is obtained by averaging the rest data, and the average power of the noise is added with an experience constant to be used as a detection threshold, namely:
wherein the method comprises the steps ofIs a scale factor->Representing a rounding down, a +.>Representation pair->Performing ascending arrangement, wherein C represents an experience constant, and N is a constant; />Representing the i-th sub-band average power.
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