A frequency hopping band searching method of a frequency hopping signal

Abstract

The application discloses a frequency hopping frequency band searching method of a frequency hopping signal, and the frequency band containing frequency hopping is found through a wideband scanning mode, and the method comprises the following steps: S1, dividing a target frequency range into several frequency bands, and acquiring a time-frequency diagram in the time of staying in each frequency band; S2, analyzing the time-frequency diagram information, and judging whether the frequency band contains a frequency hopping signal; and S3, after the scanning is finished, recording all the frequency bands containing the frequency hopping signal. The application uses the time-frequency diagram to perform rough analysis, and prepares for the next frequency hopping detection and analysis, estimates the frequency hopping parameters through tracking interference first, and then carries out reactive interference according to the parameters, so that the interference success rate is higher, and energy consumption is low.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of frequency hopping communication technology, and particularly relates to a frequency hopping frequency band searching method of frequency hopping signals. BACKGROUND

[0002] Frequency hopping communication is carried out under random carrier frequency and in combination with other spread spectrum methods, has superior anti-interference, low interception and flexible multi-address networking capability, and has been widely applied in military and civilian communication fields such as electronic warfare, radio spectrum monitoring and cognitive radio. Blind estimation of feature parameters of frequency hopping signals in complex environment is the premise and basis for realizing detection, interception and information acquisition of frequency hopping signals.

[0003] At present, the methods for suppressing frequency hopping signals include blocking jamming, sweep jamming, pre-selected frequency jamming and tracking jamming. The blocking jamming directly transmits a wideband signal without considering the frequency hopping frequency set, and interferes with the entire frequency hopping band, but the energy consumption is extremely high. The sweep jamming transmits a narrowband sweep signal without considering the frequency hopping frequency set, and the energy consumption is relatively low, but it is easy to miss a hop or not have enough interference time for each hop, and the interference success rate is not high. The pre-selected frequency jamming detects and reacts according to the user-defined frequency set, and transmits a signal of the corresponding bandwidth to interfere if a signal appears, and does not transmit an interference signal if there is no signal. Compared with sweep jamming, this method is more energy-saving, but for frequency hopping signals, this method is easy to miss a hop. SUMMARY

[0004] The present application aims to solve the problem of suppressing frequency hopping signals, and proposes a frequency hopping frequency band searching method of frequency hopping signals.

[0005] The method discovers the frequency band containing frequency hopping through a wideband scanning method, including the following steps:

[0006] S1: dividing the target frequency range into several frequency bands, and obtaining a time-frequency graph in the time of staying in each frequency band;

[0007] S2: analyzing the time-frequency graph information to determine whether the frequency band contains frequency hopping signals;

[0008] S3: after the scanning is completed, recording all frequency bands containing frequency hopping signals.

[0009] Further, a frequency hopping frequency band searching method of frequency hopping signals, the sampling rate of S1 scanning is 204.8MHz;

[0010] The scanning is T seconds of sampling on the ith frequency band, and there are a total of N samples, and the calculation formula is:

[0011] N=Tf s

[0012] Where N represents the number of samples, and T represents the sampling time.

[0013] Further, a frequency hopping band searching method of a frequency hopping signal, characterized in that the frequency resolution requirement of S1 is 25 kHz, comprising the following sub-steps:

[0014] S11: FPGA performs non-overlapping N-point FFT on every 8192 samples within T seconds fft Plus Hanning window short-time Fourier transform (STFT) operation, the (STFT) operation divides the sampling data into K segments according to N fft points, and performs FFT calculation;

[0015] K times of FFT calculation, the calculation formula is:

[0016]

[0017] Where K represents the number of FFT, N fft = 8192, and N represents the number of samples;

[0018] S12: Calculate the time-frequency graph of T seconds of sampling, the calculation formula is:

[0019] S(t, f), t = 1,..., K, f = 1,..., N fft

[0020] Where S(t, f) represents a matrix, t represents a paragraph, and f represents an N fft point number.

[0021] Further, a frequency hopping band searching method of a frequency hopping signal, characterized in that the frequency band residence time of the frequency hopping signal is set to meet the scanning rate requirement, and the residence time contains at least two hops, otherwise the frequency hopping signal is regarded as a fixed frequency signal.

[0022] Further, a frequency hopping band searching method of a frequency hopping signal, characterized in that S2 comprises the following sub-steps:

[0023] S21: Compare the time-frequency graph with the threshold th, and calculate the binary time-frequency graph as follows:

[0024]

[0025] Where th represents the threshold;

[0026] S22: Determine the suspected signal using the duty cycle, and the calculation formula of the duty cycle is:

[0027]

[0028] Where K represents the number of FFT, and D(f) represents the duty cycle.

[0029] Furthermore, a method for finding the frequency hopping band of a frequency hopping signal, characterized in that, in step S3...

[0030] For any f, if:

[0031] d0 <D(f)<d1

[0032] Where d0 represents the lower limit and d1 represents the upper limit;

[0033] If a frequency hopping signal is present in the frequency band, the search process ends.

[0034] If there is no frequency hopping signal in this frequency band, then proceed to the next 80MHz frequency band and repeat steps S1-S3;

[0035] The lower limit d0 excludes the influence of noise, reducing the calculation of noise impact in broadband scanning.

[0036] The beneficial effects of this invention are as follows: By using a method for finding frequency hopping bands of frequency hopping signals, frequency bands containing frequency hopping are discovered through broadband scanning. A rough analysis is performed using a time-frequency diagram to prepare for the next step of frequency hopping detection and analysis. This method achieves the search for frequency-modulated signals. By tracking interference to estimate frequency hopping parameters first, targeted reactive interference is then performed based on the parameters. The interference success rate is high and the energy consumption is low. Attached Figure Description

[0037] Figure 1 Flowchart of frequency hopping band search method.

[0038] Figure 2 Broadband scanning time-frequency diagram of the i-th frequency band.

[0039] Figure 3 It is a binarized time-frequency diagram of the i-th frequency band of a broadband scan.

[0040] Figure 4 It is a duty cycle diagram of each frequency signal in the i-th frequency band of broadband scanning. Detailed Implementation

[0041] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention will now be described with reference to the accompanying drawings.

[0042] like Figure 1 As shown, a method for finding frequency hopping bands of frequency hopping signals is described. This method uses a wideband scanning approach to discover frequency bands containing frequency hopping signals. The steps are as follows:

[0043] S1: Divide the target frequency range into several frequency bands and obtain a time-frequency diagram during the dwell time of each frequency band;

[0044] S2: Analyze the time-frequency graph information to determine whether the frequency band contains a frequency hopping signal;

[0045] S3: After the scanning, record all the frequency bands containing the frequency hopping signal.

[0046] Further, a frequency hopping frequency band searching method for a frequency hopping signal, the S1:

[0047] f s = 204.8 MHz

[0048] Wherein f s represents the sampling rate used by the wideband scanning;

[0049] Sampling on the i-th frequency band for T seconds, a total of N samples:

[0050] N = T f s

[0051] Wherein N represents the number of samples, T represents the sampling time, and the intermediate frequency bandwidth is 80 MHz.

[0052] Further, a frequency hopping frequency band searching method for a frequency hopping signal, the S1 needs to meet the frequency resolution requirement (25 kHz), for this, the FFPGA performs non-overlapping N fft Add Hanning window short time Fourier transform (STFT) operation, (STFT) operation divides the sampling data into K segments according to N fft The number of points, and performs FFT calculation.

[0053] S11:

[0054] K times of FFT calculation:

[0055]

[0056] Wherein K represents the number of FFTs, N fft = 8192, and N represents the number of samples;

[0057] S12:

[0058] As shown in the accompanying Figure 2 , the time-frequency diagram calculation formula of T seconds sampling is as follows:

[0059] S(t, f), t = 1,..., K, f = 1,..., N fft

[0060] Wherein S(t, f) represents a matrix, t represents a paragraph, and f represents a N fft Point number;

[0061] Because the sampling amount is small, the time-frequency diagram data amount is small, and it is put into the FPGA memory.

[0062] Further, a frequency hopping band searching method of a frequency hopping signal, the frequency band residence time of the frequency hopping signal is set to meet the scanning rate requirement time, the residence time contains at least two hops, otherwise the frequency hopping signal is regarded as a fixed frequency signal.

[0063] As shown in the accompanying Figure 3 The time-frequency diagram is compared with the threshold th, and the binary time-frequency diagram calculation formula is as follows:

[0064]

[0065] Where th represents the threshold;

[0066] As shown in the accompanying Figure 3 The determination of the non-signal is made by the duty cycle, and the duty cycle calculation formula is as follows:

[0067]

[0068] Where k represents the FFT number, and D(f) represents the duty cycle;

[0069] The frequency hopping signal occupies less time on a single frequency.

[0070] Further, a frequency hopping band searching method of a frequency hopping signal, the S3

[0071] For any f, if:

[0072] d0 < D(f) < d1

[0073] Where d0 represents the lower limit, and d1 represents the upper limit.

[0074] If there is a frequency hopping signal in the frequency band, end, otherwise enter the next 80MHz frequency band and repeat the above process;

[0075] The lower limit d0 excludes the influence of noise and reduces the noise influence calculation in wideband scanning.

[0076] The scheme realizes the searching of the frequency modulation signal by a frequency hopping band searching method of a frequency hopping signal, finds the frequency band containing the frequency hopping through the wideband scanning mode, performs rough analysis by using the time-frequency diagram, prepares for the next frequency hopping detection and analysis, estimates the frequency hopping parameters by tracking the interference first, and then performs the reactive interference according to the parameters, so that the interference success rate is higher and the energy consumption is low.

[0077] The above shows and describes the basic principles and main features of the present application and the advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above embodiments, and the above embodiments and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A frequency hopping band search method for a frequency hopping signal, characterized by, The method finds frequency bands containing frequency hopping by wideband scanning, comprising the following steps: S1: divide the target frequency range into several frequency bands, and obtain a time-frequency graph in the time of staying in each frequency band; S2: analyze the time-frequency graph information to determine whether the frequency band contains frequency hopping signals; S3: record all frequency bands containing frequency hopping signals after scanning; The sampling rate of S1 scanning is 204.8 MHz; The scanning is T-second sampling on the ith frequency band, and there are a total of N samples, and the calculation formula is: N = Tf s where N represents the number of samples, T represents the sampling time, f s represents the sampling rate; The frequency resolution requirement of S1 is 25 kHz, comprising the following sub-steps: S11: FPGA performs a short-time Fourier transform (STFT) operation on the samples within T seconds without overlapping and with a Hanning window. The STFT operation divides the sample data according to N fft The number of points is divided into K segments, and FFT calculation is performed; K times of FFT calculation, and the calculation formula is: where K represents the number of FFTs, N fft = 8192, N represents the number of samples; S12: calculate the time-frequency graph of T-second sampling, and the calculation formula is: S(t, f), t = 1,..., K, f = 1,..., N fft where S(t,f) represents a matrix, t represents a certain paragraph, and f represents a certain N fft points; S2 comprises the following sub-steps: S21: compare the time-frequency graph with a threshold th, and the calculation formula of the binary time-frequency graph is as follows: Wherein th represents the threshold; S22: use the duty cycle to determine the suspected signal, and the calculation formula of the duty cycle is: Wherein K represents the number of FFT, and D(f) represents the duty cycle.

2. The method for finding the frequency hopping band of a frequency hopping signal according to claim 1, characterized in that, The frequency band staying time of the frequency hopping signal is set to meet the scanning rate requirement, and the staying time contains at least two hops, otherwise the frequency hopping signal is regarded as a fixed frequency signal.

3. The method for finding the frequency hopping band of a frequency hopping signal according to claim 1, characterized in that, S3 meets the following condition for any f: d0 < D(f) < d1 Wherein d0 represents the lower limit, and d1 represents the upper limit; If there is a frequency hopping signal in the frequency band, the searching process is ended; If there is no frequency hopping signal in the frequency band, steps S1-S3 are repeated in the next 80 MHz frequency band; The lower limit d0 excludes the influence of noise and reduces the calculation of the influence of noise in wideband scanning.

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