CN101977091A - Method and system for monitoring electromagnetic spectrum - Google Patents

Abstract

The invention discloses a method and system for monitoring electromagnetic spectrum. The method includes: acquiring a time-domain signal output by an intermediate frequency receiver; converting the time-domain signal into a frequency-domain signal; Characteristic cross-section: use the signal conversion result and/or the calculated characteristic cross-section of the cyclic spectrum to monitor the electromagnetic spectrum. With the invention, the electromagnetic spectrum monitoring process can be completely realized in the frequency domain, and can be applied to sensor nodes simply and effectively.

Description

Electromagnetic Spectrum Monitoring Method and System

technical field

The invention relates to the technical field of electromagnetic spectrum monitoring, in particular to an electromagnetic spectrum monitoring method and system.

Background technique

With the continuous development and progress of electronic technology, the application field of radio business has expanded rapidly, and various mobile communications, satellite communications, radio and television, radar navigation, telemetry and remote control, radio astronomy and other applications have spread throughout national defense, public safety, commercial and industrial fields. sector, whose volume of business is increasing day by day. The rapid development of radio services has brought new challenges and higher requirements to the management and monitoring of radio spectrum.

Electromagnetic spectrum monitoring refers to the monitoring and general survey of radio signals in space. It mainly includes three main links: signal detection, modulation mode identification and parameter estimation. Identify the modulation mode of the signal, and estimate the carrier frequency, bandwidth, baud rate and other parameters of the signal.

At present, the electromagnetic spectrum monitoring system for electromagnetic sensor network applications mainly relies on a number of small sensor nodes that can be arranged arbitrarily to complete the monitoring of electromagnetic signals in a certain area in a coordinated manner. The monitoring nodes are small in size and limited in energy. Therefore, its processing capacity is also limited, which puts forward higher requirements for the processing method of electromagnetic spectrum monitoring, that is, the processing algorithm must be simple and fast, and the required storage and processing capabilities are relatively small.

In the prior art, the methods adopted for electromagnetic spectrum monitoring mainly fall into two categories: time domain and time-frequency domain hybrid. Among them: the time-domain method needs to store a large number of time-domain signals, which puts great pressure on the storage and processing capabilities of the nodes, and most of the time-domain methods are relatively complicated, which is not suitable for small sensor nodes with limited energy; time-frequency The electromagnetic spectrum monitoring method used in the mixed domain generally uses the frequency domain method for signal detection, and uses the idea of combining the time domain method and the frequency domain method for parameter estimation and modulation identification. On the one hand, this solution needs to store time domain signal samples , on the other hand, the back and forth conversion of time-frequency domain data is required in the processing process, and the implementation scheme is complicated, which is not conducive to the further development and loading of the algorithm, so it is not suitable for implementation on sensor nodes.

Contents of the invention

Embodiments of the present invention provide an electromagnetic spectrum monitoring method and system to completely implement electromagnetic spectrum monitoring and processing in the frequency domain, and be applied to sensor nodes simply and effectively.

For this reason, the embodiment of the present invention provides following technical scheme:

An electromagnetic spectrum monitoring method, comprising:

Obtain the time-domain signal output by the intermediate frequency receiver;

converting the time domain signal to a frequency domain signal;

calculating each characteristic section of the cyclic spectrum of the frequency domain signal;

The electromagnetic spectrum monitoring is performed by using the signal conversion result and/or the calculated characteristic sections of the cyclic spectrum.

Preferably, said converting said time-domain signal into a frequency-domain signal comprises:

The time domain signal is converted into a frequency domain signal using a fast Fourier transform.

Optionally, the electromagnetic spectrum monitoring using the signal conversion result and/or the calculated characteristic sections of the cyclic spectrum includes any one or more of the following:

Use the signal conversion result or each characteristic section of its cyclic spectrum to perform signal detection;

Use the converted frequency domain signal and each characteristic section of its cyclic spectrum to identify the signal modulation mode;

The signal parameters are estimated by using each characteristic section of the signal cycle spectrum.

Optionally, the signal detection using the signal conversion result or each characteristic section of its cyclic spectrum includes:

performing power detection on the signal conversion result; or

The peak position information of the α-section spectrum whose frequency is 0 of the cyclic spectrum is extracted for detection.

Preferably, the identification of the modulation mode of the signal by using the converted frequency domain signal and each characteristic section of its cyclic spectrum includes:

The features of each characteristic section of the signal cycle spectrum are extracted to distinguish signals of different modulation types.

Preferably, the signal parameter estimation using each characteristic section of the signal cycle spectrum includes any one or more of the following:

Extracting the spectral peak position information containing the signal carrier frequency information in the characteristic section of the signal cycle spectrum, and using the spectral peak position information to calculate the carrier frequency of the signal;

The sub-peak position information containing the signal baud rate information in the characteristic section of the signal cycle spectrum is extracted, and the baud rate of the signal is calculated by using the sub-peak position information.

A system for monitoring the full frequency domain of the electromagnetic spectrum, comprising:

a signal acquisition unit, configured to acquire a time-domain signal output by the intermediate frequency receiver;

a signal converting unit, configured to convert the time-domain signal into a frequency-domain signal;

a calculation unit, configured to calculate each characteristic section of the cyclic spectrum of the frequency-domain signal;

The monitoring unit is used to monitor the electromagnetic spectrum by using the signal conversion result and/or the calculated characteristic sections of the cyclic spectrum.

Optionally, the monitoring unit includes any one or more of the following subunits:

The signal detection subunit is used to perform signal detection by using the signal conversion result or each characteristic section of its cyclic spectrum;

The modulation mode identification subunit is used to identify the signal modulation mode by using the converted frequency domain signal and each characteristic section of its cyclic spectrum;

The parameter estimation subunit is used for estimating signal parameters by using each characteristic section of the signal cycle spectrum.

Optionally, the signal detection subunit includes:

The first detection subunit is used to perform power detection on the signal conversion result; or

The second detection subunit is used to extract the peak position information of the α-section spectrum whose frequency is 0 in the cyclic spectrum for detection.

Preferably, the modulation mode identification subunit is specifically configured to extract features of each characteristic section of the signal cycle spectrum to distinguish signals of different modulation types.

Optionally, the parameter estimation subunit includes any one or more of the following subunits:

The carrier frequency estimation subunit is used to extract the spectral peak position information containing the signal carrier frequency information in the characteristic section of the signal cycle spectrum, and use the spectral peak position information to calculate the carrier frequency of the signal;

The baud rate estimation subunit is used to extract the position information of the secondary peak containing the baud rate information of the signal in the characteristic section of the signal cycle spectrum, and use the position information of the secondary peak to calculate the baud rate of the signal.

The electromagnetic spectrum monitoring method and system of the embodiment of the present invention, aiming at the requirements of electromagnetic sensor network applications, uses the signal discrete Fourier transform (DFT) results and cyclic spectrum results to complete signal detection, parameter estimation, and modulation methods based entirely on signal frequency domain information Electromagnetic spectrum monitoring tasks such as identification. It does not need to store a large number of time-domain signal samples, nor does it need to convert time-frequency domain signals back and forth, which greatly simplifies the implementation complexity of electromagnetic spectrum monitoring, and is also easy to implement in hardware. It is well applied to sensor nodes to realize electromagnetic spectrum monitoring for electromagnetic sensor networks.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the accompanying drawings that are required in the embodiments. Obviously, the accompanying drawings in the following description are only described in the present invention For some embodiments of the present invention, those skilled in the art can also obtain other drawings according to these drawings.

Fig. 1 is the flowchart of the electromagnetic spectrum monitoring method of the embodiment of the present invention;

Fig. 2 is a specific application schematic diagram of the electromagnetic spectrum monitoring method of the embodiment of the present invention;

Fig. 3 is a schematic structural diagram of an electromagnetic spectrum monitoring system according to an embodiment of the present invention.

Detailed ways

In order to enable those skilled in the art to better understand the solutions of the embodiments of the present invention, the embodiments of the present invention will be further described in detail below in conjunction with the drawings and implementations.

As shown in Figure 1, it is a flow chart of the electromagnetic spectrum monitoring method of the embodiment of the present invention, including the following steps:

Step 101, acquire a time-domain signal output by an intermediate frequency receiver.

It is assumed that the signal received by the IF receiver has completed steps such as analog-to-digital conversion, down-conversion, down-decimation, and preprocessing, and the signal after these processes is a band-pass digital signal with a lower frequency and a lower sampling rate. in:

Analog-to-digital conversion refers to the conversion of analog signals into digital signals;

Down-conversion processing refers to the process of converting an input signal with a certain frequency into an output signal with a lower frequency, usually without changing the information content and modulation mode of the signal;

Down-decimation refers to the process of resampling a signal at a lower rate;

Preprocessing mainly completes signal separation and rough estimation of bandwidth and carrier frequency.

The above-mentioned processing is also the processing steps that electromagnetic spectrum monitoring usually needs to go through in the prior art, and the specific processing processes will not be described in detail here.

Step 102, converting the time domain signal into a frequency domain signal.

Specifically, assuming that the time-domain signal output by the intermediate frequency receiver is x(n), the DFT result X(k) of the signal x(n) can be calculated using a Fast Fourier Transform algorithm (FFT).

Step 103, calculating each characteristic section of the cyclic spectrum of the frequency domain signal

Generally, the signals whose statistical properties change steadily in periods or multiperiods are collectively referred to as cyclostationary or cyclostationary signals, and cyclic spectrum theory is the main method for studying and analyzing cyclostationary signals.

表示信号x(t)在频率f+α/2和f-α/2处的谱分量的相关密度，其中，f是经典傅氏频谱中的频率，α是循环频率变量。循环谱特征截面是指固定f所对应的α截面，或者是固定α所对应的f截面。Cyclic Spectral Density Function

Represents the correlation density of the spectral components of a signal x(t) at frequencies f+α/2 and f-α/2, where f is the frequency in the classical Fourier spectrum and α is the cyclic frequency variable. The characteristic section of the cyclic spectrum refers to the α section corresponding to a fixed f, or the f section corresponding to a fixed α.

信号循环谱f＝f_c的α截面

等。For example, the α-section of the signal cycle spectrum f=0 can be calculated

The α-section of the signal cycle spectrum f=f _c

wait.

Step 104, using the signal conversion result and/or the calculated characteristic sections of the cyclic spectrum to monitor the electromagnetic spectrum.

The electromagnetic spectrum monitoring that can be carried out mainly includes any one or more of the following:

Use the signal conversion result or each characteristic section of its cyclic spectrum to perform signal detection;

Use the converted frequency domain signal and each characteristic section of its cyclic spectrum to identify the signal modulation mode;

The signal parameters are estimated by using each characteristic section of the signal cycle spectrum.

The various monitoring above will be described in detail below.

(1) Signal detection

In the embodiment of the present invention, signal detection may be implemented in various ways.

For example, the signal detection required for electromagnetic spectrum monitoring can be completed by detecting the power of the signal conversion result.

For another example, since the noise does not have the cyclostationary characteristic, but the signal mostly has the cyclostationary characteristic, so the position of the maximum value of the α section of the noise cyclic spectrum f=0 should be at the position of α=0, but the signal does not, therefore, also The signal detection required for electromagnetic spectrum monitoring can be completed by extracting the detection of the peak position information of each characteristic cross-section of the cyclic spectrum whose cross-section frequency is 0.

(2) Identify the signal modulation method

In the embodiment of the present invention, the identifiable signal types include ASK (Amplitude Shift Keying, amplitude shift keying), FSK (Frequency-shift keying, frequency shift keying), MSK (minimum frequency shift keying), BPSK (Binary Phase Shift Keying, binary phase shift keying), QPSK (Quadrature Phase Shift Keying quadrature phase shift keying), 8PSK (8 Phase Shift Keying, 8 phase shift keying), QAM (Quadrature Amplitude Modulation, quadrature amplitude modulation ) and many other commonly used digital modulation types.

Since different signals exhibit different characteristics on the characteristic section of the cyclic spectrum, the signals of different modulation types can be distinguished by extracting the characteristics of the characteristic section of the cyclic spectrum of the signal. For example, there are two obvious spectral peaks in the α-section of the MSK signal cyclic spectrum at f=0, while the 2ASK signal has only one spectral peak, then the identification of MSK and 2ASK signals can be completed by extracting the information of the number of spectral peaks in this section.

(3) Signal parameter estimation

Since the secondary peak position in the α section of f=f _c of the signal cycle spectrum contains baud rate information, and the α section spectrum peak position of f=0 contains signal carrier frequency information, it can be obtained by extracting the spectral peak position and/or or secondary peak position information for signal parameter estimation. for example:

The spectral peak position information containing the signal carrier frequency information in the characteristic section of the signal cycle spectrum can be extracted, and the carrier frequency of the signal can be calculated by using the spectral peak position information;

Extracting the sub-peak position information containing the signal baud rate information in the characteristic section of the signal cycle spectrum, and using the sub-peak position information to calculate the baud rate of the signal;

Of course, the signal parameters that can be estimated in the embodiment of the present invention are not limited to the above-mentioned carrier frequency and baud rate, and other parameters can also be estimated, such as spreading parameters, etc., which will not be listed here.

It can be seen that the electromagnetic spectrum monitoring method in the embodiment of the present invention is aimed at the requirements of electromagnetic sensor network applications, using the signal discrete Fourier transform (DFT) results and cyclic spectrum results to complete signal detection, parameter estimation, and modulation methods based entirely on signal frequency domain information Electromagnetic spectrum monitoring tasks such as identification. There is no need to store a large number of time-domain signal samples, and there is no need to convert time-frequency domain signals back and forth, which greatly simplifies the implementation complexity of electromagnetic spectrum monitoring. As a fast implementation algorithm of DFT, FFT is also easy to implement in hardware. At the same time, it can ensure a more flexible algorithm loadability, and can be better applied to sensor nodes to realize electromagnetic spectrum monitoring for electromagnetic sensor networks.

The electromagnetic spectrum monitoring method in the embodiment of the present invention is mainly realized by using the DFT result and the cyclic spectrum result of the signal. The use of the cyclic spectrum method can bring the following two benefits: on the one hand, because the cyclic spectrum feature section contains rich information, including signal carrier frequency, baud rate, bandwidth, modulation mode characteristics, etc., it provides information for modulation identification and parameter estimation. Great convenience, for example, the cyclic spectrum characteristic section corresponding to the signal carrier frequency contains the signal baud rate information and spread spectrum parameter information, and the cyclic spectrum characteristic section of f=0 includes the signal carrier frequency, detection signal presence or absence Features and many features for modulation identification; on the other hand, as a more comprehensive signal analysis tool, the cyclic spectrum can use the cyclic spectrum characteristics of the signal to complete most modulation types, such as ASK, FSK, MSK, BPSK, QPSK, 8PSK, QAM Modulation identification and parameter estimation of communication signals.

As shown in FIG. 2 , it is a schematic diagram of a specific application of the electromagnetic spectrum monitoring method of the embodiment of the present invention.

In this example, the following steps are involved:

Step 201, using the Fast Fourier Transform algorithm FFT to calculate the DFT result of the signal x(n);

等；Step 202, using the DFT result of the signal x(n) to calculate the characteristic section of the signal cyclic spectrum, such as

wait;

Step 203, using the DFT result of the signal x(n) or the characteristic section of the signal cyclic spectrum to perform signal detection;

Step 204, using the DFT result of the signal x(n) and the characteristic section of the signal cyclic spectrum to identify the signal modulation mode, the signal types include ASK, FSK, MSK, BPSK, QPSK, 8PSK, QAM and other commonly used digital modulation types;

Step 205, using the characteristic section of the signal cyclic spectrum and the identification result of the signal modulation mode to estimate the signal parameters. The estimated parameters include the signal carrier frequency, bandwidth, baud rate and spreading code parameters.

It should be noted that the example shown in Figure 2 represents only a specific process, and in practical applications, the monitoring of the electromagnetic spectrum can also only carry out one or some of the monitoring, and it is not limited to be processed according to the above process .

Those of ordinary skill in the art can understand that all or part of the steps in the method of the above-mentioned embodiments can be completed by instructing related hardware through a program, and the program can be stored in a computer-readable storage medium, and the storage Media, such as: ROM/RAM, disk, CD, etc.

Correspondingly, the embodiment of the present invention also provides a system for monitoring the full frequency domain of the electromagnetic spectrum, as shown in FIG. 2 , which is a schematic structural diagram of the system.

In this embodiment, the system includes:

A signal acquisition unit 301, configured to acquire a time-domain signal output by the intermediate frequency receiver;

a signal conversion unit 302, configured to convert the time domain signal into a frequency domain signal;

A calculation unit 303, configured to calculate each characteristic section of the cyclic spectrum of the frequency-domain signal;

The monitoring unit 304 is configured to monitor the electromagnetic spectrum by using the signal conversion result and/or the calculated characteristic sections of the cyclic spectrum.

Wherein, the monitoring unit 304 may include any one or more of the following subunits:

The signal detection subunit is used to perform signal detection by using the signal conversion result or each characteristic section of its cyclic spectrum;

The modulation mode identification subunit is used to identify the signal modulation mode by using the converted frequency domain signal and each characteristic section of its cyclic spectrum;

The parameter estimation subunit is used for estimating signal parameters by using each characteristic section of the signal cycle spectrum.

Among them, each subunit can be realized in many ways, such as:

The signal detection subunit includes: a first detection subunit, or a second detection subunit. The first detection subunit is used to detect the power of the signal conversion result; the second detection subunit is used to extract the peak position information of the α-section spectrum with a frequency of 0 in the cyclic spectrum for detection.

The modulation mode identification subunit can distinguish signals of different modulation types by extracting features of each characteristic section of the signal cycle spectrum.

The parameter estimation subunit may include any one or more of the following subunits:

The carrier frequency estimation subunit is used to extract the spectral peak position information containing the signal carrier frequency information in the characteristic section of the signal cycle spectrum, and use the spectral peak position information to calculate the carrier frequency of the signal;

The baud rate estimation subunit is used to extract the position information of the secondary peak containing the baud rate information of the signal in the characteristic section of the signal cycle spectrum, and use the position information of the secondary peak to calculate the baud rate of the signal.

Of course, in the embodiment of the present invention, the parameter estimation subunit is not limited to the above-mentioned structure, and may also include other parameter estimation subunits, which use the signal cyclic spectrum characteristic section to complete the estimation of corresponding signal parameters, such as bandwidth and spreading code parameters wait.

The electromagnetic spectrum monitoring system of the embodiment of the present invention is aimed at the requirements of electromagnetic sensor network applications, using the signal discrete Fourier transform (DFT) results and cyclic spectrum results to complete signal detection, parameter estimation, modulation mode identification, etc. based entirely on signal frequency domain information Electromagnetic Spectrum Monitoring Mission. There is no need to store a large number of time-domain signal samples, and there is no need to convert time-frequency domain signals back and forth, which greatly simplifies the implementation complexity of electromagnetic spectrum monitoring. As a fast implementation algorithm of DFT, FFT is also easy to implement in hardware. At the same time, it can ensure a more flexible algorithm loadability, and can be better applied to sensor nodes to realize electromagnetic spectrum monitoring for electromagnetic sensor networks.

It should be noted that, for the system embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and for relevant parts, please refer to the part of the description of the method embodiment. The system embodiments described above are only illustrative, and the units described as separate components may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they may be located in One place, or it can be distributed to multiple network elements. Part or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment. It can be understood and implemented by those skilled in the art without creative effort.

The embodiments of the present invention have been described in detail above, and the present invention has been described using specific implementation methods herein. The descriptions of the above embodiments are only used to help understand the method and equipment of the present invention; meanwhile, for those of ordinary skill in the art, According to the idea of the present invention, there will be changes in the specific implementation and scope of application. To sum up, the contents of this specification should not be construed as limiting the present invention.

Claims (11)

1. An electromagnetic spectrum monitoring method, characterized in that, comprising: Obtain the time-domain signal output by the intermediate frequency receiver; converting the time domain signal to a frequency domain signal; calculating each characteristic section of the cyclic spectrum of the frequency domain signal; The electromagnetic spectrum monitoring is performed by using the signal conversion result and/or the calculated characteristic sections of the cyclic spectrum. 2. The method according to claim 1, wherein said converting said time-domain signal into a frequency-domain signal comprises: The time domain signal is converted into a frequency domain signal using a fast Fourier transform. 3. The method according to claim 1, wherein the electromagnetic spectrum monitoring includes any one or more of the following using the signal conversion result and/or each characteristic section of the calculated cyclic spectrum: Use the signal conversion result or each characteristic section of its cyclic spectrum to perform signal detection; Use the converted frequency domain signal and each characteristic section of its cyclic spectrum to identify the signal modulation mode; The signal parameters are estimated by using each characteristic section of the signal cycle spectrum. 4. The method according to claim 3, wherein said utilizing signal conversion results or each characteristic section of its cyclic spectrum to perform signal detection comprises: performing power detection on the signal conversion result; or The peak position information of the α-section spectrum whose frequency is 0 of the cyclic spectrum is extracted for detection. 5. method according to claim 3, is characterized in that, the frequency-domain signal of described utilization conversion and each characteristic section identification signal modulation mode of its cyclic spectrum comprises: The features of each characteristic section of the signal cycle spectrum are extracted to distinguish signals of different modulation types. 6. The method according to claim 3, wherein the signal parameter estimation using each characteristic section of the signal cyclic spectrum comprises any one or more of the following: Extracting the spectral peak position information containing the signal carrier frequency information in the characteristic section of the signal cycle spectrum, and using the spectral peak position information to calculate the carrier frequency of the signal; The sub-peak position information containing the signal baud rate information in the characteristic section of the signal cycle spectrum is extracted, and the baud rate of the signal is calculated by using the sub-peak position information. 7. A system for monitoring the full frequency domain of the electromagnetic spectrum, which is characterized in that it includes: a signal acquisition unit, configured to acquire a time-domain signal output by the intermediate frequency receiver; a signal converting unit, configured to convert the time-domain signal into a frequency-domain signal; a calculation unit, configured to calculate each characteristic section of the cyclic spectrum of the frequency-domain signal; The monitoring unit is used to monitor the electromagnetic spectrum by using the signal conversion result and/or the calculated characteristic sections of the cyclic spectrum. 8. The system according to claim 7, wherein the monitoring unit comprises any one or more of the following subunits: The signal detection subunit is used to perform signal detection by using the signal conversion result or each characteristic section of its cyclic spectrum; The modulation mode identification subunit is used to identify the signal modulation mode by using the converted frequency domain signal and each characteristic section of its cyclic spectrum; The parameter estimation subunit is used for estimating signal parameters by using each characteristic section of the signal cycle spectrum. 9. The system according to claim 8, wherein the signal detection subunit comprises: The first detection subunit is used to perform power detection on the signal conversion result; or The second detection subunit is used to extract the peak position information of the α-section spectrum whose frequency is 0 in the cyclic spectrum for detection. 10. The system of claim 8, wherein: The modulation mode identification subunit is specifically used to extract the features of each characteristic section of the signal cycle spectrum to distinguish signals of different modulation types. 11. The system according to claim 8, wherein the parameter estimation subunit comprises any one or more of the following subunits: The carrier frequency estimation subunit is used to extract the spectral peak position information containing the signal carrier frequency information in the signal cycle spectrum characteristic section, and use the spectral peak position information to calculate the carrier frequency of the signal; The baud rate estimation subunit is used to extract the position information of the secondary peak containing the baud rate information of the signal in the characteristic section of the signal cycle spectrum, and use the position information of the secondary peak to calculate the baud rate of the signal.

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