CN111585610A - Digital filtering method and device for coherent fast frequency hopping signal - Google Patents
Digital filtering method and device for coherent fast frequency hopping signal Download PDFInfo
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B1/00—Details of transmission systems, not covered by a single one of groups H04B3/00 - H04B13/00; Details of transmission systems not characterised by the medium used for transmission
- H04B1/69—Spread spectrum techniques
- H04B1/713—Spread spectrum techniques using frequency hopping
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Abstract
The embodiment of the invention provides a digital filtering method and a digital filtering device for coherent fast frequency hopping signals, wherein the method comprises the following steps: receiving a coherent fast frequency hopping signal, and performing down-conversion processing on the coherent fast frequency hopping signal to obtain a first signal; sequentially carrying out first filtering and first time domain extraction on the first signal to obtain a second signal; obtaining an interference deletion threshold to zero the interfered frequency point signals according to the average signal amplitude of each frequency hopping frequency point of the second signal, and deleting periodic time domain pulses at the frequency point switching position to obtain a third signal; and performing second filtering on the third signal to obtain a fourth signal, and performing matched filtering in a square wave form on the fourth signal to obtain a fifth signal. Compared with the interference identification and digital filtering method which is moved to the frequency domain through FFT, the embodiment of the invention can realize the interference suppression function without converting the signal in the time-frequency domain.
Description
Technical Field
The present invention relates to the field of communications technologies, and in particular, to a digital filtering method and apparatus for coherent fast frequency hopping signals.
Background
Under the development trend of digital battlefields, the confidentiality performance and the anti-interference performance of information transmission become important indexes for measuring the reliability of a military communication system, and the fast frequency hopping communication with the anti-multipath and anti-tracking interference capabilities is widely applied. For a particular fast frequency hopping system, the wider the bandwidth occupied by the hopping pattern, the greater the interference rejection. For example, the JTIDS information distribution system of the air force in the united states adopts a high-speed frequency hopping technology, and 51 frequency points are distributed in a 144MHz bandwidth, so that the JTIDS information distribution system has anti-interference and confidentiality characteristics.
In digital signal processing, the large bandwidth of the hopping signal means that higher sampling frequencies, usually need to be decimated by a filter, but also the interference components will be adulterated, so that strong interference components need to be identified and deleted during fast hopping signal processing. In the traditional FFT frequency domain identification method, FFT conversion is carried out on a time domain signal to obtain a signal spectrum, interference components are found in the frequency domain to be suppressed, IFFT conversion is carried out to obtain a time domain signal after interference is removed, and a large amount of resources are consumed in the process.
Disclosure of Invention
Embodiments of the present invention provide a method and apparatus for digital filtering of coherent fast frequency hopping signals that overcomes, or at least partially solves, the above-mentioned problems.
In a first aspect, an embodiment of the present invention provides a method for digitally filtering a coherent fast frequency hopping signal, including:
receiving a coherent fast frequency hopping signal, and performing down-conversion processing on the coherent fast frequency hopping signal to obtain a first signal, wherein the sampling rate of the coherent fast frequency hopping signal is 64 times of the chip rate of the coherent fast frequency hopping signal;
sequentially carrying out first filtering and first time domain extraction on the first signal to obtain a second signal, wherein the passband of the first filtering is 2 times of the chip rate of the coherent fast frequency hopping signal, the cut-off frequency is 4 times of the chip rate, and the oversampling multiple after the first time domain extraction is 8 times of the chip rate of the coherent fast frequency hopping signal;
obtaining an interference deletion threshold according to the average signal amplitude of each frequency hopping frequency point of the second signal so as to zero the frequency point signal subjected to interference, and deleting the periodic time domain pulse at the frequency point switching position so as to obtain a third signal;
carrying out second filtering on the third signal to obtain a fourth signal, wherein the passband of the second filtering is 2 times of the chip rate of the coherent fast frequency hopping signal, the cut-off frequency of the stop band is k times of the chip rate, and k is more than 2 and less than 3;
and performing matched filtering in the form of square waves on the fourth signal to obtain a fifth signal.
Further, the digital filtering method for coherent fast frequency hopping signals further includes: carrying out third filtering on the fifth signal, and then carrying out second time domain extraction to obtain chip information;
wherein the passband of the third filtering is 1 times the chip rate of the coherent fast frequency hopping signal.
Further, the performing down-conversion processing on the coherent fast frequency hopping signal specifically includes:
generating a fast frequency hopping carrier signal according to the frequency hopping pattern of the coherent fast frequency hopping signal, and multiplying the fast frequency hopping carrier signal by the received coherent fast frequency hopping signal to obtain a first signal;
and the frequency of the frequency point of the fast frequency hopping carrier signal is opposite to the frequency of the frequency point of the coherent fast frequency hopping signal.
Further, the magnitude of out-of-band rejection of the first filtering is related to the median of the target interference-to-signal ratio.
Further, the obtaining of an interference deletion threshold to set zero to the frequency point signal subjected to interference according to the average signal amplitude of each frequency hopping frequency point of the second signal specifically includes:
obtaining an average signal amplitude of each frequency hopping frequency point of the second signal, and multiplying a minimum average signal value by a preset threshold coefficient to obtain the interference deletion threshold;
and for any frequency hopping time slot, if the signal amplitude of the frequency hopping time slot is greater than the interference deletion threshold, taking the frequency point in the frequency hopping time slot as the frequency point subjected to interference, and setting the signal of the frequency point subjected to interference to zero.
Further, the out-of-band rejection of the second filtering is greater than a target interference-to-signal ratio.
In a second aspect, an embodiment of the present invention provides an apparatus for digitally filtering a coherent fast frequency hopping signal, including:
the local oscillator module is used for receiving a coherent fast frequency hopping signal, performing down-conversion processing on the coherent fast frequency hopping signal, and obtaining a first signal, wherein the sampling rate of the coherent fast frequency hopping signal is 64 times the chip rate of the coherent fast frequency hopping signal;
the first decimation filter is used for sequentially carrying out first filtering and first time domain decimation on the first signal to obtain a second signal, wherein the passband of the first filtering is 2 times of the chip rate of the coherent fast frequency hopping signal, the cut-off frequency is 4 times of the chip rate, and the oversampling multiple after the first time domain decimation is 8 times of the chip rate of the coherent fast frequency hopping signal;
the interference deleting module is used for obtaining an interference deleting threshold according to the average signal amplitude of each frequency hopping frequency point of the second signal so as to set the frequency point signal subjected to interference to zero, and deleting the periodic time domain pulse at the frequency point switching position so as to obtain a third signal;
the high-order anti-aliasing filter is used for carrying out secondary filtering on the third signal to obtain a fourth signal, the passband of the secondary filtering is 2 times of the chip rate of the coherent fast frequency hopping signal, the stop band cut-off frequency is k times of the chip rate, and k is more than 2 and less than 3;
and the matched filter is used for performing matched filtering in a square wave form on the fourth signal to obtain a fifth signal.
In a third aspect, an embodiment of the present invention provides an electronic device, which includes a memory, a processor, and a computer program stored in the memory and executable on the processor, and the processor implements the steps of the method provided in the first aspect when executing the program.
In a fourth aspect, an embodiment of the present invention provides a non-transitory computer readable storage medium, on which a computer program is stored, which when executed by a processor, implements the steps of the method as provided in the first aspect.
According to the digital filtering method and device for the coherent fast frequency hopping signal, provided by the embodiment of the invention, the effective signal is down-converted to the baseband according to the characteristic of the instantaneous narrow band of the coherent fast frequency hopping signal, the interference of the baseband signal is identified and deleted through the interference deletion threshold, for the interference at a non-frequency point, the interference and the suppression of aliasing components of the interference are realized through two times of filtering, and the rate is further extracted to 2 times of the code rate so as to be convenient for coherent reception. Compared with the interference identification and digital filtering method which is moved to the frequency domain through FFT, the embodiment of the invention can realize the interference suppression function without carrying out time-frequency domain conversion on the signal.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and those skilled in the art can also obtain other drawings according to the drawings without creative efforts.
FIG. 1 is a flow chart of a digital filtering method for coherent fast frequency hopping signals according to an embodiment of the present invention;
FIG. 2 is a graph of a spectrum of a received coherent fast frequency hopping signal according to an embodiment of the present invention;
FIG. 3 is a spectrum diagram of a first signal according to an embodiment of the present invention;
FIG. 4 is a spectrum diagram of a second signal according to an embodiment of the present invention;
FIG. 5 is a spectrum diagram of a third signal according to an embodiment of the present invention;
FIG. 6 is a spectrum diagram of a fourth signal according to an embodiment of the present invention;
fig. 7 is a schematic structural diagram of a digital filtering apparatus for coherent fast frequency hopping signals according to an embodiment of the present invention;
fig. 8 is a schematic physical structure diagram of an electronic device according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be 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 some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Fig. 1 is a schematic flow chart of a digital filtering method for coherent fast frequency hopping signals according to an embodiment of the present invention, as shown in fig. 1, including:
s101, receiving a coherent fast frequency hopping signal, and performing down-conversion processing on the coherent fast frequency hopping signal to obtain a first signal, wherein the sampling rate of the coherent fast frequency hopping signal is 64 times of the chip rate of the coherent fast frequency hopping signal;
it should be noted that, in the embodiments of the present invention, the coherent fast frequency hopping signal is down-converted by the fast frequency hopping carrier signal, so that the effective signal of each hop of the coherent fast frequency hopping signal can be down-converted to the baseband, and the interference component is shifted by the frequency spectrum and distributed in the entire sampling frequency band. In addition, because the bandwidth of the frequency hopping pattern of the coherent fast frequency hopping signal of the embodiment of the present invention is 64 times the chip rate, the sampling rate after down-conversion to the baseband should not be less than the bandwidth of the frequency hopping pattern according to the nyquist sampling law, and the sampling rate of the coherent fast frequency hopping signal is finally determined to be 64 times the chip rate of the coherent fast frequency hopping signal by comprehensive consideration.
FIG. 2 is a frequency spectrum diagram of a received coherent fast frequency hopping signal according to an embodiment of the present invention, and as shown in FIG. 2, a frequency hopping pattern of the coherent fast frequency hopping signal includes 8 frequency points, which correspond to f in the frequency spectrum of the received fast frequency hopping signal respectively1,f2,f3,f4,f5,f6,f7,f8Frequency point of fast frequency hopping signal is represented by f1～f8And circularly switching, wherein the duration of each frequency point is equal, and the frequency point is a frequency hopping time slot. The sampling rate of the received fast frequency hopping signal is 163.84MHz, the chip rate is 2.56MHz, the modulation mode is BPSK, square wave forming is adopted, and the signal bandwidth corresponding to each frequency point in the frequency spectrum is 5.12 MHz. To fully illustrate the interference identification and suppression function of the present invention, in fig. 2, narrow-band interference signals (hereinafter referred to as interference) with interference-to-signal ratios (i.e. the ratio of the interference signal strength to the target echo signal strength) of 70dB at two points respectively located at the frequency point and the non-frequency point are selected as examples, and respectively correspond to the center frequency f indicated by the solid line in the frequency spectrumaAnd the center frequency represented by a dotted line is fbInterference at non-frequency points. Wherein f isa＝f7The bandwidths of the two interferences are equal and slightly larger than the signal bandwidth at a single frequency point, and the two interferences exist in the frequency hopping time slots of all the frequency points.
In fig. 2, the signals at 8 frequency points of the coherent fast frequency hopping signal according to the embodiment of the present invention only appear in the frequency hopping time slot corresponding to each frequency point, and have an instantaneous narrowband characteristic, so that by setting the signal in a certain frequency hopping time slot to zero in the time domain, the frequency component at the frequency point can be deleted in the frequency domain.
Fig. 3 is a frequency spectrum diagram of a first signal according to an embodiment of the present invention, and it can be understood that the frequency spectrum diagram shown in fig. 3 is obtained by mixing the frequency spectrum diagram of the coherent fast frequency hopping signal shown in fig. 2 with a fast frequency hopping carrier signal, and as shown in fig. 3, the coherent fast frequency hopping signals located at 8 frequency points are all shifted to zero frequency, which corresponds to a center frequency of zero and a bandwidth of 5 in the frequency spectrum.The baseband signal component with lower amplitude of 12MHz is equivalent to the debounce of coherent fast frequency hopping signals; and is located at frequency point f7Interference at the fast hopping carrier frequency point of-f7The frequency hopping time slot is shifted to zero frequency, corresponding to the baseband interference component with the center frequency of zero and the bandwidth slightly larger than the bandwidth of the baseband signal in the frequency spectrum of the first signal, and the frequency point of the fast frequency hopping carrier signal is not-f7The mobile terminal is moved to other frequency points of which the central frequency point is not zero in the frequency hopping time slot, and corresponds to 7 out-of-band interference components which are represented by a solid line, wherein the central frequency point in the first signal is not zero and the bandwidth of the first signal is equal to that of the baseband interference components; at non-frequency point fbThe interference signal is shifted to other frequency points with the central frequency point not being zero, and 8 out-of-band interference components represented by a dotted line with the central frequency point not being zero and the bandwidth equal to the baseband interference component in the first signal are corresponded.
On the basis of the above embodiments, the duration of each frequency point of the fast frequency hopping carrier signal in the embodiments of the present invention is the same, and is also equal to one frequency hopping time slot of the coherent fast frequency hopping signal, and if the delay and the code phase between the coherent fast frequency hopping signal and the fast frequency hopping carrier signal are both aligned, and the received fast frequency hopping signal has no frequency offset, coherent reception can still be performed after the frequency hopping is released.
S102, sequentially carrying out first filtering and first time domain extraction on the first signal to obtain a second signal, wherein the passband of the first filtering is 2 times of the chip rate of the coherent fast frequency hopping signal, the cut-off frequency is 4 times of the chip rate, and the oversampling multiple after the first time domain extraction is 8 times of the chip rate of the coherent fast frequency hopping signal.
FIG. 4 is a spectrogram of a second signal according to an embodiment of the present invention, it can be understood that the spectrogram shown in FIG. 4 is obtained by performing a first decimation filtering on the spectrogram of the first signal shown in FIG. 3, an impulse response of the filter corresponds to an impulse response of the first decimation filter shown in FIG. 3, a passband ranging from-2.56 MHz to 2.56MHz, a stopband ranging from-infinity to-10.24 MHz and 10.24MHz to + ∞, and an out-of-band interference in the stopband range is suppressed by 40dB with respect to baseband components; the oversampling multiple of the first signal is 64 times, and after 1/8 time domain extraction, the sampling rate of the system is reduced to 20.48MHz, and the oversampling multiple is reduced to 8 times. In the extraction process, the frequency spectrums of the baseband signal component, the baseband interference component and the out-of-band interference component which is not completely suppressed within the frequency range of-10.24 MHz to 10.24MHz are reserved, which respectively correspond to the baseband signal component, the baseband interference component and the interference component which is not completely suppressed in the second signal frequency spectrum in fig. 4; in the decimation process, suppressed out-of-band interference components in the frequency range outside-10.24 MHz to 10.24MHz will alias into the 20.48MHz band due to the extension of the frequency domain period corresponding to the time domain decimation, corresponding to the aliased interference components in the second signal spectrum.
Since the out-of-band interference component has been initially suppressed in the process of obtaining the second signal, the aliased interference component in the spectrum of the second signal is 40dB lower in power than the baseband interference component.
S103, according to the average signal amplitude of each frequency hopping frequency point of the second signal, obtaining an interference deletion threshold to zero the frequency point signal subjected to interference, and deleting the periodic time domain pulse at the frequency point switching position to obtain a third signal.
It should be noted that, in the embodiments of the present invention, an interference cancellation threshold is obtained by using an instantaneous narrowband characteristic of a coherent fast frequency hopping signal, and if a signal amplitude of a certain frequency hopping time slot is greater than a strong interference decision threshold, a signal in the frequency hopping time slot is set to zero, which is equivalent to deleting an interfered frequency point in a frequency domain. In addition, under the action of strong interference, the second signal has discontinuous points in the time domain, and periodic time domain pulses are generated due to the gibbs effect after the step S102. Therefore, in addition to deleting the interfered frequency point signal, the pulse is also needed to be deleted at the start position of each frequency hopping frequency point, so as to obtain a third signal.
Fig. 5 is a frequency spectrum diagram of a third signal according to an embodiment of the present invention, and it can be understood that the frequency spectrum diagram shown in fig. 5 is obtained on the basis of the frequency spectrum diagram of the second signal shown in fig. 4, and as shown in fig. 5, the generation process of the third signal is to identify and suppress interference of the second signal on a baseband, since a baseband interference component is not primarily suppressed, the interference is much larger than other interference components, andexists only in the frequency hopping time slot corresponding to the interfered frequency point, such as frequency point f in fig. 27And the signal amplitude in the time slot is obviously higher than the frequency hopping time slots corresponding to other frequency points. By recording respective signal amplitude average value in 8 frequency point frequency hopping time slots corresponding to one frequency hopping pattern
Calculating the minimum of these averages
Multiplying with the threshold coefficient as an interference threshold, corresponding to the interference threshold shown in fig. 4, the baseband interference component can be identified and the signal is set to zero in the corresponding frequency hopping timeslot, resulting in the frequency spectrum of the third signal shown in fig. 5, from which it can be found that the baseband interference component is completely suppressed.
And S104, carrying out second filtering on the third signal to obtain a fourth signal, wherein the passband of the second filtering is 2 times of the chip rate of the coherent fast frequency hopping signal, the cut-off frequency of the stop band is k times of the chip rate, and k is more than 2 and less than 3.
Fig. 6 is a frequency spectrum diagram of a fourth signal according to an embodiment of the present invention, and it can be understood that the frequency spectrum diagram shown in fig. 6 is obtained on the basis of the frequency spectrum diagram of the third signal shown in fig. 5, and low-pass filtering is performed on the third signal, where the pass band range is-2.56 MHz to 2.56MHz, and the stop band range is out of-band rejection is 80dB outside-3 MHz to filter out incompletely suppressed interference and aliasing interference components as much as possible, so as to retain baseband signal components, and the impulse response of the second filter is shown by a dashed line in the frequency spectrum shown in fig. 5. Through the processing of step S104, aliasing interference components outside the baseband signal and incompletely suppressed interference in the-10.24 MHz to 10.24MHz frequency band are filtered out by the filter, and the spectrogram shown in fig. 6 is obtained.
And S105, performing square wave matched filtering on the fourth signal to obtain a fifth signal.
It should be noted that, through the processing in steps S101-S104, the present invention has implemented the filtering of the interference at the frequency point and the non-frequency point, and then the matched filtering in the form of square wave is performed in step S105, so as to restore the baseband component and eliminate the inter-symbol interference.
According to the digital filtering method of the coherent fast frequency hopping signal, the effective signal is down-converted to the baseband according to the characteristic of the instantaneous narrow band of the coherent fast frequency hopping signal, the interference of the baseband signal is identified and deleted through the interference deletion threshold, for the interference at a non-frequency point, the interference and the suppression of aliasing components of the interference are realized through two times of filtering after the interference is down-converted to the outside of the baseband, and the interference is further extracted to 2 times of the code rate so as to be convenient for coherent reception. Compared with the interference identification and digital filtering method which is moved to the frequency domain through FFT, the embodiment of the invention can realize the interference suppression function without carrying out time-frequency domain conversion on the signal.
On the basis of the foregoing embodiments, as an optional embodiment, the digital filtering method for coherent fast frequency hopping signals according to the embodiments of the present invention further includes:
carrying out third filtering on the fifth signal, and then carrying out second time domain extraction to obtain chip information; the passband of the third filtering is 1 times the chip rate of the coherent fast frequency hopping signal.
It should be noted that, by filtering and time-domain extracting the fifth signal, the final sampling rate is 1 time of the chip rate of the coherent fast frequency hopping signal, so as to implement coherent reception of the fast frequency hopping signal.
It should be noted that all signals described in the embodiments of the present invention are digital discrete signals and are complex signals.
On the basis of the foregoing embodiments, as an optional embodiment, the performing down-conversion processing on the coherent fast frequency hopping signal specifically includes:
generating a fast frequency hopping carrier signal according to the frequency hopping pattern of the coherent fast frequency hopping signal, and multiplying the fast frequency hopping carrier signal by the received coherent fast frequency hopping signal to obtain a first signal; and the frequency of the frequency point of the fast frequency hopping carrier signal is opposite to the frequency of the frequency point of the coherent fast frequency hopping signal.
It should be noted that the frequency hopping pattern for generating the fast frequency hopping carrier signal according to the embodiment of the present invention is the frequency hopping pattern of the coherent fast frequency hopping signal. By setting the fast frequency hopping carrier signals and the coherent fast frequency hopping signals with opposite frequencies, the coherent fast frequency hopping signals at the frequency points and the interference at the frequency points can be shifted to zero frequency through down-conversion processing, but the interference signals not at the frequency points are shifted to other frequency points with the central frequency point not being zero, namely, effective signals of each hop of the coherent fast frequency hopping signals are down-converted to a baseband, and interference components are subjected to frequency spectrum shifting after being mixed and are distributed in the whole sampling frequency band.
On the basis of the above embodiments, as an alternative embodiment, the cut-off frequency of the stop band of the first filtering is 4 times the chip rate, and the magnitude of the out-of-band rejection is related to the median of the target interference-to-signal ratio.
It should be noted that the magnitude of the out-of-band rejection is related to the median of the target interference-to-signal ratio, i.e. the magnitude of the out-of-band rejection is around the median of the target interference-to-signal ratio, e.g. 70dB, then the out-of-band rejection may be 40dB, so that the aliased interference components in the spectrum of the second signal are 40dB lower in power than the baseband interference components.
On the basis of the foregoing embodiments, as an optional embodiment, the obtaining an interference cancellation threshold to set zero to the interfered frequency point signal according to the average signal amplitude of each frequency hopping frequency point of the second signal specifically includes:
obtaining an average signal amplitude of each frequency hopping frequency point of the second signal, and multiplying the minimum average signal amplitude by a preset threshold coefficient to obtain the interference deletion threshold;
and for any frequency hopping time slot, if the signal amplitude of the frequency hopping time slot is greater than the interference deletion threshold, taking the frequency point in the frequency hopping time slot as the frequency point subjected to interference, and setting the signal of the frequency point subjected to interference to zero.
On the basis of the above embodiments, as an alternative embodiment, the threshold coefficient is 1.5.
On the basis of the above embodiments, as an optional embodiment, the out-of-band rejection of the second filtering is greater than the target interference-to-signal ratio, so as to retain baseband signal components and filter out incompletely rejected interference and aliasing interference components as much as possible.
Fig. 7 is a schematic structural diagram of a digital filtering apparatus for coherent fast frequency hopping signals according to an embodiment of the present invention, and as shown in fig. 7, the digital filtering apparatus for coherent fast frequency hopping signals includes: a local oscillation de-hopping module 201, a first decimation filter 202, an interference cancellation module 203, a high-order anti-aliasing filter 204 and a matched filter 205, wherein:
a debounce local oscillator module 201, configured to receive a coherent fast frequency hopping signal, perform down-conversion processing on the coherent fast frequency hopping signal, and obtain a first signal, where a sampling rate of the coherent fast frequency hopping signal is 64 times a chip rate of the coherent fast frequency hopping signal;
a first decimation filter 202, configured to perform first filtering and first time-domain decimation on the first signal in sequence to obtain a second signal, where a passband of the first filtering is 2 times of a chip rate of the coherent fast frequency hopping signal, a cutoff frequency is 4 times of the chip rate, and an oversampling multiple after the first time-domain decimation is 8 times of the chip rate of the coherent fast frequency hopping signal;
the interference deleting module 203 is configured to obtain an interference deleting threshold to set zero to the interfered frequency point signal according to the average signal amplitude of each frequency hopping frequency point of the second signal, and delete the periodic time domain pulse located at the frequency point switching position to obtain a third signal;
the high-order anti-aliasing filter 204 is configured to perform second filtering on the third signal to obtain a fourth signal, where a passband of the second filtering is 2 times of a chip rate of the coherent fast frequency hopping signal, a stop band has a cutoff frequency of k times of the chip rate, and k is greater than 2 and less than 3;
a matched filter 205, configured to perform matched filtering on the fourth signal in the form of a square wave to obtain a fifth signal.
The digital filtering apparatus for coherent fast frequency hopping signals according to the embodiments of the present invention specifically executes the flow of the interference identification method for each coherent fast frequency hopping signal, and please refer to the content of the interference identification method for each coherent fast frequency hopping signal in detail, which is not described herein again. The digital filtering device for coherent fast frequency hopping signals provided by the embodiment of the invention carries out down-conversion on effective signals to a baseband according to the characteristics of instantaneous narrow bands of the coherent fast frequency hopping signals, carries out interference identification and deletion on the baseband signals through an interference deletion threshold, carries out down-conversion on the interference at a non-frequency point to the outside of the baseband, realizes the inhibition of the interference and aliasing components thereof through twice filtering, and further extracts the interference to 2 times of a code rate so as to be convenient for coherent reception. Compared with the interference identification and digital filtering method which is moved to the frequency domain through FFT, the embodiment of the invention can realize the interference suppression function without carrying out time-frequency domain conversion on the signal.
On the basis of the foregoing embodiments, as an optional embodiment, the digital filtering apparatus for coherent fast frequency hopping signals according to the embodiments of the present invention further includes:
the second decimation filter is used for carrying out third filtering on the fifth signal and then carrying out second time domain decimation to obtain chip information; the passband of the third filtering is 1 times the chip rate of the coherent fast frequency hopping signal.
Fig. 8 is a schematic entity structure diagram of an electronic device according to an embodiment of the present invention, and as shown in fig. 8, the electronic device may include: a processor (processor)310, a communication Interface (communication Interface)320, a memory (memory)330 and a communication bus 340, wherein the processor 310, the communication Interface 320 and the memory 330 communicate with each other via the communication bus 340. The processor 310 may invoke a computer program stored on the memory 330 and executable on the processor 310 to perform the digital filtering method of the coherent fast frequency hopping signal provided by the above embodiments, for example, including: receiving a coherent fast frequency hopping signal, and performing down-conversion processing on the coherent fast frequency hopping signal to obtain a first signal, wherein the sampling rate of the coherent fast frequency hopping signal is 64 times of the chip rate of the coherent fast frequency hopping signal; sequentially carrying out first filtering and first time domain extraction on the first signal to obtain a second signal, wherein the passband of the first filtering is 2 times of the chip rate of the coherent fast frequency hopping signal, the cut-off frequency is 4 times of the chip rate, and the oversampling multiple after the first time domain extraction is 8 times of the chip rate of the coherent fast frequency hopping signal; obtaining an interference deletion threshold to zero the interfered frequency point signals according to the average signal amplitude of each frequency hopping frequency point of the second signal, and deleting periodic time domain pulses at the frequency point switching position to obtain a third signal; carrying out second filtering on the third signal to obtain a fourth signal, wherein the passband of the second filtering is 2 times of the chip rate of the coherent fast frequency hopping signal, the cut-off frequency of the stop band is k times of the chip rate, and k is more than 2 and less than 3; and performing matched filtering in the form of square waves on the fourth signal to obtain a fifth signal.
In addition, the logic instructions in the memory 330 may be implemented in the form of software functional units and stored in a computer readable storage medium when the software functional units are sold or used as independent products. Based on such understanding, the technical solutions of the embodiments of the present invention may be essentially implemented or make a contribution to the prior art, or may be implemented in the form of a software product stored in a storage medium and including instructions for causing a computer device (which may be a personal computer, a server, or a network device) to execute all or part of the steps of the methods described in the embodiments of the present invention. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a Random Access Memory (RAM), a magnetic disk or an optical disk, and other various media capable of storing program codes.
Embodiments of the present invention further provide a non-transitory computer-readable storage medium, on which a computer program is stored, where the computer program is implemented to perform the digital filtering method for coherent fast frequency hopping signals provided in the foregoing embodiments when executed by a processor, for example, the method includes: receiving a coherent fast frequency hopping signal, and performing down-conversion processing on the coherent fast frequency hopping signal to obtain a first signal, wherein the sampling rate of the coherent fast frequency hopping signal is 64 times of the chip rate of the coherent fast frequency hopping signal; sequentially carrying out first filtering and first time domain extraction on the first signal to obtain a second signal, wherein the passband of the first filtering is 2 times of the chip rate of the coherent fast frequency hopping signal, the cut-off frequency is 4 times of the chip rate, and the oversampling multiple after the first time domain extraction is 8 times of the chip rate of the coherent fast frequency hopping signal; obtaining an interference deletion threshold to zero the interfered frequency point signals according to the average signal amplitude of each frequency hopping frequency point of the second signal, and deleting periodic time domain pulses at the frequency point switching position to obtain a third signal; carrying out second filtering on the third signal to obtain a fourth signal, wherein the passband of the second filtering is 2 times of the chip rate of the coherent fast frequency hopping signal, the cut-off frequency of the stop band is k times of the chip rate, and k is more than 2 and less than 3; and performing matched filtering in the form of square waves on the fourth signal to obtain a fifth signal.
The above-described embodiments of the apparatus are merely illustrative, and the units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the solution of the present embodiment. One of ordinary skill in the art can understand and implement it without inventive effort.
Through the above description of the embodiments, those skilled in the art will clearly understand that each embodiment can be implemented by software plus a necessary general hardware platform, and certainly can also be implemented by hardware. With this understanding in mind, the above-described technical solutions may be embodied in the form of a software product, which can be stored in a computer-readable storage medium such as ROM/RAM, magnetic disk, optical disk, etc., and includes instructions for causing a computer device (which may be a personal computer, a server, or a network device, etc.) to execute the methods described in the embodiments or some parts of the embodiments.
Finally, it should be noted that: the above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.
Claims (10)
1. A method for digitally filtering a coherent fast frequency hopping signal, comprising:
receiving a coherent fast frequency hopping signal, and performing down-conversion processing on the coherent fast frequency hopping signal to obtain a first signal, wherein the sampling rate of the coherent fast frequency hopping signal is 64 times of the chip rate of the coherent fast frequency hopping signal;
sequentially carrying out first filtering and first time domain extraction on the first signal to obtain a second signal, wherein the passband of the first filtering is 2 times of the chip rate of the coherent fast frequency hopping signal, the cut-off frequency is 4 times of the chip rate, and the oversampling multiple after the first time domain extraction is 8 times of the chip rate of the coherent fast frequency hopping signal;
obtaining an interference deletion threshold to zero the interfered frequency point signals according to the average signal amplitude of each frequency hopping frequency point of the second signal, and deleting periodic time domain pulses at the frequency point switching position to obtain a third signal;
carrying out second filtering on the third signal to obtain a fourth signal, wherein the passband of the second filtering is 2 times of the chip rate of the coherent fast frequency hopping signal, the cut-off frequency of the stop band is k times of the chip rate, and k is more than 2 and less than 3;
and performing matched filtering in the form of square waves on the fourth signal to obtain a fifth signal.
2. The method of digitally filtering a coherent fast frequency hopping signal according to claim 1, further comprising: carrying out third filtering on the fifth signal, and then carrying out second time domain extraction to obtain chip information;
wherein the passband of the third filtering is 1 times the chip rate of the coherent fast frequency hopping signal.
3. The digital filtering method for coherent fast frequency hopping signals according to claim 1, wherein the down-conversion processing is performed on the coherent fast frequency hopping signals, specifically:
generating a fast frequency hopping carrier signal according to the frequency hopping pattern of the coherent fast frequency hopping signal, and multiplying the fast frequency hopping carrier signal by the received coherent fast frequency hopping signal to obtain a first signal;
and the frequency of the frequency point of the fast frequency hopping carrier signal is opposite to the frequency of the frequency point of the coherent fast frequency hopping signal.
4. The method of claim 1, wherein the magnitude of the out-of-band rejection of the first filtering is related to a median of a target interference-to-signal ratio.
5. The digital filtering method for coherent fast frequency hopping signals according to claim 1, wherein the obtaining of the interference cancellation threshold to zero the frequency point signal subjected to interference according to the average signal amplitude of each frequency hopping frequency point of the second signal specifically comprises:
obtaining an average signal amplitude of each frequency hopping frequency point of the second signal, and multiplying a minimum average signal value by a preset threshold coefficient to obtain the interference deletion threshold;
and for any frequency hopping time slot, if the signal amplitude of the frequency hopping time slot is greater than the interference deletion threshold, taking the frequency point in the frequency hopping time slot as the frequency point subjected to interference, and setting the signal of the frequency point subjected to interference to zero.
6. The method of digital filtering of coherent fast frequency hopping signals according to claim 1, wherein the out-of-band rejection of the second filtering is greater than a target interference-to-signal ratio.
7. The method of digital filtering of coherent fast frequency hopping signals according to claim 5, wherein said threshold coefficient is 1.5.
8. An apparatus for digital filtering of coherent fast frequency hopping signals, comprising:
the local oscillator module is used for receiving a coherent fast frequency hopping signal, performing down-conversion processing on the coherent fast frequency hopping signal, and obtaining a first signal, wherein the sampling rate of the coherent fast frequency hopping signal is 64 times the chip rate of the coherent fast frequency hopping signal;
the first decimation filter is used for sequentially carrying out first filtering and first time domain decimation on the first signal to obtain a second signal, wherein the passband of the first filtering is 2 times of the chip rate of the coherent fast frequency hopping signal, the cut-off frequency is 4 times of the chip rate, and the oversampling multiple after the first time domain decimation is 8 times of the chip rate of the coherent fast frequency hopping signal;
the interference deleting module is used for obtaining an interference deleting threshold according to the average signal amplitude of each frequency hopping frequency point of the second signal so as to set the frequency point signal subjected to interference to zero, and deleting the periodic time domain pulse at the frequency point switching position so as to obtain a third signal;
the high-order anti-aliasing filter is used for carrying out secondary filtering on the third signal to obtain a fourth signal, the passband of the secondary filtering is 2 times of the chip rate of the coherent fast frequency hopping signal, the stop band cut-off frequency is k times of the chip rate, and k is more than 2 and less than 3;
and the matched filter is used for performing matched filtering in a square wave form on the fourth signal to obtain a fifth signal.
9. An electronic device comprising a memory, a processor and a computer program stored on the memory and executable on the processor, characterized in that the processor when executing the program performs the steps of digital filtering of coherent fast frequency hopping signals according to any one of claims 1 to 7.
10. A non-transitory computer readable storage medium storing computer instructions for causing a computer to perform digital filtering of a coherent fast frequency hopping signal according to any one of claims 1 to 7.
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