A narrowband signal extraction method, electronic device and storage medium

Abstract

The present invention discloses a narrowband signal extraction method, an electronic device and a storage medium. The above method includes: selecting a first signal sequence of a fixed length in a time domain narrowband signal, downsampling the first signal sequence and filling it with zeros to form a second signal sequence, performing Fourier time-frequency transform on the second signal sequence to obtain a third signal sequence; frequency domain intercepting the third signal sequence to obtain a fourth signal sequence; selecting a window function, performing Fourier transform on the window function, and multiplying the frequency domain window function with the fourth signal sequence to form a fifth signal sequence; performing Fourier time-frequency inverse transform on the fifth signal sequence to form a sixth signal sequence in the time domain; splicing the sixth signal sequence to achieve the extraction of the target narrowband signal. The narrowband signal extraction method provided by the present invention has strong anti-aliasing performance, can provide high-quality basic data for back-end monitoring applications, and improve the monitoring and interception capabilities of weak signals.

Description

Technical Field

[0001] The present application belongs to the field of communication technology, and in particular, relates to a narrowband signal extraction method, an electronic device and a storage medium. Background Art

[0002] With the proposal of high probability interception and full-factor acquisition for communication monitoring, the front-end adopts full-band RF direct acquisition and the back-end server performs digital signal processing, which has become the mainstream design for monitoring. Especially in the field of narrowband monitoring, due to the high sampling rate of the front-end, the output signal of the receiving channel must be extracted and processed before the back-end recognizes and demodulates the signal.

[0003] Due to the crowded narrowband channels and large dynamic range, weak signals are easily submerged in strong signals. Figure 1 It is a traditional time-domain DDC signal extraction method. This method has high requirements for sharp cutoff characteristics and large filter order for out-of-band suppression of anti-aliasing filters. If multi-stage cascade extraction is used, the engineering implementation complexity is high, and multiple extractions are difficult to guarantee anti-aliasing performance. Therefore, a high-performance narrowband signal extraction method is urgently needed to provide high-quality basic data for back-end monitoring applications and improve the monitoring and interception capabilities of weak signals. Summary of the invention

[0004] Therefore, in view of the above defects in the prior art, the present application provides a narrowband signal extraction method, an electronic device and a storage medium, which aims to at least solve the problems existing in the prior art.

[0005] To achieve the above object, according to a first aspect of the present application, a narrowband signal extraction method is provided, the method comprising:

[0006] A first signal sequence of a fixed length is selected from a time-domain narrowband signal, the first signal sequence is downsampled and then padded with zeros to form a second signal sequence, the second signal sequence is subjected to Fourier time-frequency transform to obtain a third signal sequence; the third signal sequence is subjected to frequency domain truncation to obtain a fourth signal sequence; a window function is selected, the window function is subjected to Fourier transform, and the window function in the frequency domain is multiplied by the fourth signal sequence to form a fifth signal sequence; the fifth signal sequence is subjected to inverse Fourier time-frequency transform to form a sixth signal sequence in the time domain.

[0007] Preferably, the method for selecting a first signal sequence of fixed length in a time-domain narrowband signal comprises: selecting the length of the first signal sequence according to a sampling rate of the time-domain narrowband signal.

[0008] Preferably, the length of the first signal sequence is the sampling rate of the time-domain narrowband signal.

[0009] Preferably, the method for frequency domain truncation of the third signal sequence includes: acquiring the frequency domain resolution of the third signal sequence according to the sampling rate of the time domain narrowband signal; calculating the number of sequence points of the fourth signal sequence according to the frequency domain resolution and the target sampling rate of the target narrowband signal to be extracted; selecting a sequence point in the third signal sequence as the starting sequence point of the fourth signal sequence according to the frequency domain resolution, the sampling rate of the time domain narrowband signal and the target frequency of the target narrowband signal to be extracted; and in the third signal sequence, starting from the starting sequence point, selecting the number of sequence points in sequence to form the fourth signal sequence.

[0010] Preferably, the splicing method is an overlap-add method or an overlap-save method.

[0011] Preferably, the window function is a flat-top window.

[0012] According to a second aspect of the present application, there is also provided an electronic device, comprising a memory and a processor, wherein the memory stores a computer program, and the processor is configured to run the computer program to execute the narrowband signal extraction method described above.

[0013] According to a third aspect of the present application, a storage medium is further provided, wherein a computer program is stored in the storage medium, wherein the computer program is configured to execute the above-mentioned narrowband signal extraction method when running.

[0014] In the method provided by the embodiment of the present invention, a signal sequence of a certain length is selected in the time domain, and a zero-padding operation is performed on the signal sequence after downsampling. After the zero-padding is completed, the time domain signal sequence is converted into a frequency domain signal sequence through time-frequency transformation. According to the sampling rate of the time domain signal sequence and the target narrowband signal frequency to be extracted, other frequency signal sequences other than the target narrowband signal are removed. The target narrowband signal sequence is filtered by frequency domain windowing. The filtered frequency domain signal sequence is inversely transformed in time-frequency to a time domain signal sequence for signal restoration, thereby extracting the target narrowband signal. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 It is a schematic diagram of a narrowband signal extraction method provided by the prior art;

[0016] Figure 2 It is a schematic diagram of a narrowband signal extraction method provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0017] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0018] As described in the background technology, when using traditional time-domain digital down-conversion for narrowband signal extraction, the out-of-band suppression and sharp cutoff characteristics of the anti-aliasing filter are required to be high, and the filter order is huge. If multi-stage cascade extraction is used, the engineering implementation complexity is high, and multiple extractions are difficult to guarantee anti-aliasing performance. Therefore, there is an urgent need for a high-performance target narrowband signal extraction method that can provide high-quality basic data for back-end monitoring applications and improve the monitoring and interception capabilities of weak signals.

[0019] In the method provided by the embodiment of the present invention, a signal sequence of a certain length is selected in the time domain, and a zero-padding operation is performed on the signal sequence after downsampling. After the zero-padding is completed, the time domain signal sequence is converted into a frequency domain signal sequence through time-frequency transformation. According to the sampling rate of the time domain signal sequence and the target narrowband signal frequency to be extracted, other frequency signal sequences other than the target narrowband signal are removed. The target narrowband signal sequence is filtered by frequency domain windowing. The filtered frequency domain signal sequence is inversely transformed in time-frequency to a time domain signal sequence for signal restoration, thereby extracting the target narrowband signal.

[0020] Figure 2 It is a schematic diagram of a narrowband signal extraction method provided by an embodiment of the present invention.

[0021] Step 1: Select a first signal sequence of fixed length in the time domain narrowband signal, downsample the first signal sequence and fill it with zeros to form a second signal sequence, perform Fourier time-frequency transform on the second signal sequence, and obtain a third signal sequence.

[0022] Specifically, after the external RF analog signal passes through the receiving channel, the output signal of the receiving channel is AD converted, and the AD conversion sampling rate is Fs1 to obtain a processable digital time domain narrowband signal, and a time domain first signal sequence with a length of N is selected. Optionally, N is the sampling rate Fs1 of the time domain narrowband signal. The first signal sequence is downsampled and then zero-filled. Specifically, the signal sequence of sampling point L is padded with zeros to a length of N points. The signal sequence after zero filling is the second signal sequence. The second signal sequence is subjected to Fourier time-frequency transform to obtain a third signal sequence X1, X2...XN.

[0023] Step 2: Perform frequency domain interception on the third signal sequence to obtain a fourth signal sequence.

[0024] In an optional embodiment, the frequency domain resolution R of the third signal sequence is obtained based on the received time domain narrowband signal sampling rate, i.e., Fs1; the number of sequence points M of the fourth signal sequence is calculated based on the frequency domain resolution R and the target sampling rate Fs2 of the target narrowband signal to be extracted; and a sequence point in the third signal sequence is selected as the starting sequence point of the fourth signal sequence based on the frequency domain resolution R, the time domain narrowband signal sampling rate Fs1, and the target frequency Fc of the target narrowband signal to be extracted.

[0025] Specifically, R = Fs1 / N, M = round(Fs / R) (round means rounding to the nearest integer)

[0026] The XI in the third signal sequence is used as the starting sequence point of the fourth signal sequence, wherein,

[0027] I=round(Fc / R)-round(Fs2 / 2 / R),

[0028] In the third signal sequence, starting from the XI sequence point, M-1 sequence points are selected in sequence, and the sequence composed of the above M sequence points is the fourth signal sequence.

[0029] Different from the time domain processing method, this step directly intercepts the target narrowband signal spectrum sequence and removes the non-target signal spectrum sequence, so the spectrum resolution remains unchanged and has strong flexibility.

[0030] Step 3: Select a window function, perform Fourier transform on the window function, and multiply the transformed frequency domain window function with the fourth signal sequence to form a fifth signal sequence. Preferably, the window function is a flat-top window. Specifically, according to the bandwidth and out-of-band suppression requirements of the target narrowband signal to be extracted, a low-pass filter that meets the performance is designed, and the filter coefficient is transformed in the frequency domain as a window function for frequency domain windowing. According to the principle that time domain convolution and frequency domain multiplication are mutually equivalent, the fourth signal sequence is correspondingly multiplied with the frequency domain window function, and the frequency domain windowing process is completed to achieve filtering.

[0031] Step 4: Perform inverse Fourier time-frequency transform on the fifth signal sequence to form a sixth signal sequence in the time domain.

[0032] Step 5: splice the sixth signal sequence to extract the target narrowband signal. Since the segmented time domain sequence is padded with zeros in step 1, the sixth signal sequence must have overlapping points. Optionally, the sixth signal sequence is spliced ​​using an overlap-add method or an overlap-retain method. Optionally, the entire overlapping part is added using an overlap-add method to form the target signal sequence to be extracted together with the non-overlapping part.

[0033] The present invention also provides an electronic device, including a memory and a processor, wherein a computer program is stored in the memory. Optionally, the electronic device is located on the data processing center side, and the processor is configured to run a computer program to execute methods including but not limited to the above steps 2 and 3. Optionally, the electronic device is from the device side, and is optionally used to implement the above method including but not limited to step 1. The processor can be implemented in any appropriate manner. For example, the processor can take the form of a computer-readable medium, logic gates, switches, application-specific integrated circuits (ASICs), programmable logic controllers, and embedded microcontrollers, etc., such as a microprocessor or processor and a computer-readable program code (such as software or firmware) that can be executed by the (micro) processor. This specification is not limited.

[0034] The present invention also provides a storage medium based on the above method, wherein a computer program is stored in the storage medium, wherein the computer program is configured to execute the above method including but not limited to step 1, step 2 and step 3 when it is run. The above storage medium includes but is not limited to a random access memory (RAM), a read-only memory (ROM), a cache, a hard disk (HDD) or a memory card. The memory can be used to store computer program instructions.

[0035] The present invention discloses a narrowband signal extraction method, an electronic device and a storage medium. The above method includes: selecting a first signal sequence of a fixed length in a time domain narrowband signal, downsampling the first signal sequence and filling it with zeros to form a second signal sequence, performing Fourier time-frequency transform on the second signal sequence to obtain a third signal sequence; frequency domain intercepting the third signal sequence to obtain a fourth signal sequence; selecting a window function, performing Fourier transform on the window function, and multiplying the frequency domain window function with the fourth signal sequence to form a fifth signal sequence; performing Fourier time-frequency inverse transform on the fifth signal sequence to form a sixth signal sequence in the time domain; splicing the sixth signal sequence to achieve the extraction of the target narrowband signal. The narrowband signal extraction method provided by the present invention has strong anti-aliasing performance, can provide high-quality basic data for back-end monitoring applications, and improve the monitoring and interception capabilities of weak signals.

[0036] The contents described in this specification are merely examples of the present invention. Those skilled in the art to which the present invention belongs may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the contents of the present specification or exceed the scope defined by the claims, they shall fall within the protection scope of the present invention.

Claims

1. A narrowband signal extraction method, characterized in that: include: Selecting a first signal sequence of fixed length from the time domain narrowband signal, downsampling the first signal sequence and then padding the first signal sequence with zeros to form a second signal sequence, performing Fourier time-frequency transform on the second signal sequence to obtain a third signal sequence; Performing frequency domain interception on the third signal sequence to obtain a fourth signal sequence; comprising: obtaining a frequency domain resolution of the third signal sequence according to the sampling rate of the time domain narrowband signal; calculating the number of sequence points of the fourth signal sequence according to the frequency domain resolution and the target sampling rate of the target narrowband signal to be extracted; selecting a sequence point in the third signal sequence as a starting sequence point of the fourth signal sequence according to the frequency domain resolution, the sampling rate of the time domain narrowband signal and the target frequency of the target narrowband signal to be extracted; and selecting, in the third signal sequence, the number of sequence points, starting from the starting sequence point, in sequence to form the fourth signal sequence; Selecting a window function, performing Fourier time-frequency transform on the window function, and multiplying the transformed frequency domain window function by the fourth signal sequence to form a fifth signal sequence; Performing an inverse Fourier time-frequency transform on the fifth signal sequence to form a sixth signal sequence in the time domain; The sixth signal sequence is spliced ​​to achieve the extraction of the target narrowband signal.

2. The narrowband signal extraction method according to claim 1, characterized in that: The method for selecting a first signal sequence of fixed length in a time domain narrowband signal includes: selecting the length of the first signal sequence according to a sampling rate of the time domain narrowband signal.

3. The narrowband signal extraction method according to claim 2, characterized in that: The length of the first signal sequence is the sampling rate of the time-domain narrowband signal.

4. The narrowband signal extraction method according to claim 1, characterized in that: The splicing method is an overlap-addition method or an overlap-reserve method.

5. The narrowband signal extraction method according to claim 1, characterized in that: The window function is a flat-top window.

6. An electronic device, characterized in that: The method comprises a memory and a processor, wherein the memory stores a computer program, and the processor is configured to run the computer program to execute the narrowband signal extraction method according to any one of claims 1 to 5.

7. A computer-readable storage medium, characterized in that: The storage medium stores a computer program, wherein the computer program is configured to execute the narrowband signal extraction method according to any one of claims 1 to 5 when running.

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