Enhanced Roland system data demodulation method based on notch processing

Abstract

The invention particularly relates to an enhanced Rowland system data demodulation method based on notch processing, which utilizes the characteristics of a notch filter, combines the frequency domain characteristics of enhanced Rowland signals to design filter parameters, applies the filter parameters to the notch processing of enhanced Rowland acquisition signals, and combines correlation coefficients in a pulse matching method for judgment. Therefore, information demodulation is completed. The calculation result shows that the method can effectively improve the accuracy of information demodulation of the enhanced Roland system.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of land-based positioning and timing technology, and particularly relates to an enhanced Loran system data demodulation method based on notch processing. BACKGROUND

[0002] In the related art, the center frequency of the enhanced Loran system pulse signal carrier is 100 kHz, and the energy is concentrated in the range of 90 kHz to 110 kHz. The enhanced Loran system (eLoran) uses a pulse group signal as a carrier to establish a data communication system, and realizes remote transmission of time code information of a standard time source and other data. The information modulation mode is a balanced modulation (Pulse Position Modulation, PPM) of a three-state pulse shift word on the basis of a two-phase two-period complementary code, that is, information is modulated onto the 3rd-8th pulse of the group repetition period by a time control method, and the modulation amount of the time control is ±1 μs. This modulation mode produces three signal patterns: (1) if the transmission phase has no displacement, it represents information "0" modulation, (2) if the transmission phase leads by 1 μs, it represents information "-" modulation, and (3) if the transmission phase lags by 1 μs, it represents information "+" modulation. At the same time, the modulation mode on the 3rd-8th pulse in each pulse group corresponds to a balance pattern, and these balance patterns are predefined and can be referred to in the relevant design documents. The enhanced Loran system pulse group phase encoding and modulation mode are shown in Figure 1

[0003] The receiving device of the enhanced Loran system needs to complete the work by demodulating the received information. The information demodulation process is to correctly determine the phase modulation information applied to each pulse of the enhanced Loran system pulse group signal, which is "0", "-" or "+". Due to the influence of noise, sky wave, and narrowband interference in the process of signal transmission and reception, the information demodulation method becomes a key link in data link processing. The correctness of information demodulation will directly affect the accuracy of data decoding and text information recovery in the later stage. In the traditional information demodulation process, different methods are usually used to process noise, sky wave, and narrowband interference separately. For example, for noise and out-of-band continuous wave interference, a bandpass filter can be used for processing, but when the signal-to-noise ratio is low, the bandpass filter will cause distortion of the time domain signal, affecting demodulation. For in-band continuous wave narrowband interference, a bandpass filter cannot be used. If the amplitude of the in-band narrowband interference is large, the frequency of the interference signal can be detected in the frequency domain, and the interference signal can be filtered. However, in the case of low signal-to-noise ratio, the interference signal and noise cannot be distinguished, so the in-band narrowband interference will affect the demodulation.

[0004] ​It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of the present invention, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0005] This invention provides an enhanced Loland system data demodulation method based on notch filtering, a computer program product, and an electronic device. It can overcome the shortcomings of traditional enhanced Loland system information demodulation methods in terms of low demodulation accuracy, especially when there is in-band narrowband interference, and thus effectively overcome the defects existing in the prior art to a certain extent.

[0006] Other features and advantages of the invention will become apparent from the following detailed description, or may be learned in part by practice of the invention.

[0007] According to a first aspect of the present invention, an enhanced Loran system data demodulation method based on notch filtering is provided, the method comprising: Obtain the pulse sequence to be processed, and perform FFT transformation on the pulse sequence to obtain the corresponding frequency domain pulse signal; The system identifies whether there is narrowband interference within the frequency band of the frequency domain pulse signal, and calls the corresponding notch filtering strategy to perform notch filtering based on the identification result, thereby obtaining the corresponding time domain pulse signal. The standard Loran signal is notched to obtain a filtered signal; the filtered signal is then modulated with lead modulation and lag modulation to obtain the lead modulation signal and lag modulation signal, respectively. The time-domain pulse signal is multiplied by the filtered signal, the lead modulation signal, and the lag modulation signal to obtain the corresponding first, second, and third cumulative values; and the corresponding data modulation method is determined based on the maximum cumulative value.

[0008] In some exemplary embodiments, the presence of narrowband interference within the frequency band of the frequency domain signal is identified, and a corresponding notch filtering strategy is invoked based on the identification result, including: When narrowband interference is detected, the target notch filter is invoked to perform a first notch filter on the frequency points of the frequency domain signal where narrowband interference exists; and then, the signal after the first notch filter is subjected to a notch filter based on 100kHz to obtain a time-domain pulse signal; or When it is determined that there is no narrowband interference, the frequency domain signal is subjected to notch filtering based on 100kHz to obtain the time domain pulse signal.

[0009] In some exemplary embodiments, invoking the target notch filter to perform a first notch filter processing on the frequency points where narrowband interference exists in the frequency domain signal includes:

[0010] in, Indicates the angular frequency at which notch filtering is required; , This represents a parameter related to the quality factor of a notch filter.

[0011] In some exemplary embodiments, obtaining the pulse sequence to be processed includes: The pulse signal is received based on a constant target sampling rate, and a pulse sequence to be processed is constructed based on the received pulse signal.

[0012] In some exemplary embodiments, the method further includes: A standard Roland signal is generated based on the target sampling rate.

[0013] According to a second aspect of the present invention, a computer program product is provided, on which a computer program is stored, wherein when the computer program is executed by a processor, the enhanced Loran system data demodulation method based on notch filtering as described in the first aspect is implemented.

[0014] According to a third aspect of the present invention, an electronic device is provided, comprising: Processor; and Memory for storing the executable instructions of the processor; The processor is configured to implement the enhanced Roland system data demodulation method based on notch filtering described in the first aspect above by executing the executable instructions.

[0015] According to a fourth aspect of the present invention, a storage medium is provided having a computer program stored thereon, which, when executed by a processor, implements the enhanced Roland system data demodulation method based on notch filtering described in the first aspect.

[0016] According to a fifth aspect of the present invention, an enhanced Loran system data demodulation method based on notch filtering is provided, the method comprising: The system acquires the pulse signal to be processed, performs notch filtering on the pulse signal to obtain a filtered signal, identifies whether there is continuous wave interference in the filtered signal, and calls the corresponding notch filtering strategy to perform notch filtering based on the identification result, thereby obtaining the corresponding single pulse signal; and The pulse signal to be processed is linearly analyzed to obtain a reference signal; the reference signal is then subjected to notch filtering and FFT transformation to obtain the corresponding frequency domain pulse signal. The system identifies whether there is continuous wave interference within the frequency band in the frequency domain pulse signal, and calls the corresponding notch filtering strategy to perform notch filtering based on the identification result, thereby obtaining the corresponding time domain pulse signal. The time-domain pulse signal is modulated according to a preset modulation rule to obtain the corresponding lead modulation signal, lag modulation signal and excitation reference signal; The single pulse signal is multiplied by the lead modulation signal, the lag modulation signal and the excitation reference signal to obtain the corresponding first cumulative value, second cumulative value and third cumulative value; and the corresponding data modulation mode is determined according to the maximum cumulative value.

[0017] In some exemplary embodiments, the time-domain pulse signal is modulated according to a preset modulation rule to obtain the corresponding lead modulation signal, lag modulation signal, and excitation reference signal, including: The time-domain pulse signal is subjected to lead modulation and lag modulation respectively to obtain the lead modulation signal, the lag modulation signal and the excitation reference signal.

[0018] In some exemplary embodiments, notch processing is performed by invoking the corresponding notch processing strategy based on the identification result, including: When continuous wave interference is confirmed, the target notch filter is invoked to filter the frequency domain signal; or If it is determined that there is no continuous wave interference, no action is taken.

[0019] According to a sixth aspect of the present invention, a computer program product is provided, on which a computer program is stored, wherein when the computer program is executed by a processor, the enhanced Loran system data demodulation method based on notch filtering described in the fifth aspect above is implemented.

[0020] According to a seventh aspect of the present invention, an electronic device is provided, comprising: Processor; and Memory for storing the executable instructions of the processor; The processor is configured to implement the enhanced Roland system data demodulation method based on notch filtering described in the fifth aspect above by executing the executable instructions.

[0021] According to an eighth aspect of the present invention, a storage medium is provided having a computer program stored thereon, which, when executed by a processor, implements the enhanced Roland system data demodulation method based on notch filtering described in the fifth aspect above.

[0022] According to a ninth aspect of the present invention, an enhanced Loran system data demodulation method based on notch filtering is provided, the method comprising: The system acquires the pulse signal to be processed, performs notch filtering on the pulse signal to obtain a filtered signal, identifies whether there is continuous wave interference in the filtered signal, and calls the corresponding notch filtering strategy to perform notch filtering based on the identification result, and constructs a pulse signal group; and The pulse signal to be processed is linearly analyzed to obtain a reference signal; the reference signal is then subjected to notch filtering and FFT transformation to obtain the corresponding frequency domain pulse signal. The system identifies whether there is continuous wave interference in the frequency domain pulse signal, and calls the corresponding notch filtering strategy to perform notch filtering based on the identification result, thereby obtaining the corresponding time domain pulse signal. The time-domain pulse signal is modulated according to a preset modulation rule to obtain the corresponding lead modulation signal, lag modulation signal and excitation reference signal, and a mode library is constructed. Each pulse signal in the pulse signal group is multiplied by each signal in the pattern library to obtain the corresponding cumulative value; and the corresponding data modulation method is determined based on the maximum cumulative value.

[0023] According to a tenth aspect of the present invention, a computer program product is provided, on which a computer program is stored, wherein when the computer program is executed by a processor, the enhanced Loran system data demodulation method based on notch filtering as described in the ninth aspect is implemented.

[0024] According to an eleventh aspect of the present invention, an electronic device is provided, comprising: Processor; and Memory for storing the executable instructions of the processor; The processor is configured to implement the enhanced Roland system data demodulation method based on notch filtering described in the ninth aspect above by executing the executable instructions.

[0025] According to a twelfth aspect of the present invention, a storage medium is provided having a computer program stored thereon, which, when executed by a processor, implements the enhanced Roland system data demodulation method based on notch filtering described in the ninth aspect above.

[0026] The enhanced Loran system data demodulation method based on notch filtering provided in the embodiments of the present invention utilizes the characteristics of notch filters, designs filter parameters based on the frequency domain characteristics of enhanced Loran signals, and applies them to the notch filtering of enhanced Loran acquired signals. The correlation coefficient from the pulse matching method is then used for judgment, thereby completing the demodulation of information. By applying notch filtering to the demodulation of enhanced Loran signals, correct demodulation can be achieved even with low signal-to-noise ratios and narrowband interference, leading to correct decoding. This significantly improves the accuracy of demodulation and decoding, and expands the application range of the receiver.

[0027] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit the invention. Attached Figure Description

[0028] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0029] Figure 1 The diagram illustrates an exemplary embodiment of the present invention: an enhanced Loran system data demodulation method based on notch filtering. Figure 2 The diagram illustrates a schematic representation of the data demodulation process of an enhanced Loran system based on notch filtering, according to an exemplary embodiment of the present invention. Figure 3 The diagram schematically illustrates the frequency response characteristics of a notch filter and the frequency domain characteristics of an enhanced Rowland signal pulse, according to an exemplary embodiment of the present invention. Figure 4 This schematic diagram illustrates the spectrum of an enhanced Loland received signal with noise and in-band narrowband interference, according to an exemplary embodiment of the present invention. Figure 5 This diagram schematically illustrates a signal after noise and narrowband interference notch filtering, according to an exemplary embodiment of the present invention. Figure 6 This diagram illustrates, in accordance with an exemplary embodiment of the present invention, the relationship between the single-pulse demodulation accuracy and the signal-to-noise ratio (including narrowband interference). Figure 7 This schematic diagram illustrates another enhanced Loran system data demodulation method based on notch filtering, an exemplary embodiment of the present invention. Figure 8 This schematic diagram illustrates the processing flow of another enhanced Loran system data demodulation method based on notch filtering, as exemplified by an exemplary embodiment of the present invention. Figure 9 The diagram illustrates another exemplary embodiment of the present invention: an enhanced Loran system data demodulation method based on notch filtering. Figure 10 The diagram illustrates a processing flow of an enhanced Loran system data demodulation method based on notch filtering, as exemplified by an exemplary embodiment of the present invention. Figure 11 The diagram illustrates the composition of an electronic device according to an exemplary embodiment of the present invention. Detailed Implementation

[0030] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, they are provided so that the invention will be more comprehensive and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0031] Furthermore, the accompanying drawings are merely illustrative of the invention and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore repeated descriptions of them will be omitted. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities. These functional entities can be implemented in software, in one or more hardware modules or integrated circuits, or in different network and / or processor devices and / or microcontroller devices.

[0032] In related technologies, single-pulse matching is a good demodulation method for enhanced Loran systems, achieving a demodulation accuracy greater than 50% even at low signal-to-noise ratios, such as -20dB. However, single-pulse matching cannot suppress narrowband interference in the signal, limiting the receiver's demodulation performance. Therefore, these traditional demodulation methods are insufficient to meet the requirements of modern receivers, necessitating alternative methods to improve the effectiveness of demodulation in PPM modulation.

[0033] To address the shortcomings and deficiencies of existing technologies, this example embodiment provides an enhanced Loran system data demodulation method based on notch filtering, referencing... Figure 1 As shown, it can specifically include: Step S11: Obtain the pulse sequence to be processed, and perform FFT transformation on the pulse sequence to obtain the corresponding frequency domain pulse signal; Step S12: Identify whether there is narrowband interference in the frequency domain pulse signal, and call the corresponding notch processing strategy to perform notch processing based on the identification result to obtain the corresponding time domain pulse signal. Step S13: Perform notch filtering on the standard Loran signal to obtain the filtered signal; perform lead modulation and lag modulation on the filtered signal to obtain the lead modulation signal and the lag modulation signal, respectively. Step S14: Perform inner product operations on the time-domain pulse signal with the filtered signal, the lead modulation signal, and the lag modulation signal respectively to obtain the corresponding first cumulative value, second cumulative value, and third cumulative value; and determine the corresponding data modulation method based on the maximum cumulative value.

[0034] The method in this embodiment, by applying notch filtering to the demodulation of enhanced Loland signals, can achieve correct demodulation of information under conditions of low signal-to-noise ratio and in-band narrowband interference, thereby achieving correct decoding of information. This greatly improves the accuracy of information demodulation and decoding and expands the application range of the receiver.

[0035] The following will describe in more detail each step of the airborne high-resolution video transmission method in this exemplary embodiment, with reference to the accompanying drawings and embodiments.

[0036] In step S11, the pulse sequence to be processed is obtained, and the pulse sequence is subjected to FFT transformation to obtain the corresponding frequency domain pulse signal.

[0037] Specifically, refer to Figure 2 As shown, an enhanced Loran receiver can be used to receive pulse signals at a constant sampling rate and construct a pulse sequence as the pulse sequence to be processed. However, due to the influence of the actual propagation environment, the received signal may contain random noise, continuous wave interference (CWI), or skywave interference.

[0038] The frequency domain information, i.e. the corresponding frequency domain pulse signal, can be obtained by performing FFT (Fourier Transform) on each pulse signal in the pulse sequence.

[0039] In step S12, the presence of narrowband interference within the frequency band of the frequency domain pulse signal is identified, and the corresponding notch processing strategy is called to perform notch processing based on the identification result to obtain the corresponding time domain pulse signal.

[0040] For example, the system identifies whether narrowband interference exists within the frequency band of the frequency domain signal, and calls the corresponding notch filtering strategy based on the identification result, including: When narrowband interference is detected, the target notch filter is invoked to perform a first notch filter on the frequency points of the frequency domain signal where narrowband interference exists; and then, the signal after the first notch filter is subjected to a notch filter based on 100kHz to obtain a time-domain pulse signal; or When it is determined that there is no narrowband interference, the frequency domain signal is subjected to notch filtering based on 100kHz to obtain the time domain pulse signal.

[0041] Specifically, for frequency domain pulse signals, the presence of narrowband interference within the frequency band can be determined based on the larger value of the frequency domain amplitude.

[0042] Specifically, when narrowband interference is detected, a pre-built notch filter can be used to perform notch filtering at that frequency. The Z-domain transfer function of the notch filter includes:

[0043] in, Indicates the angular frequency at which notch filtering is required; , This represents a parameter related to the quality factor of the notch filter. Among them, This parameter relates to the quality factor of the notch filter. The filter parameters can be set based on the frequency response characteristics of the notch filter and the frequency domain characteristics of the enhanced Loran signal. Since the signal energy of the enhanced Loran is concentrated in the 90-110kHz range, with a bandwidth of 20kHz and a carrier frequency of 100kHz, the Q value is set to 5.

[0044] Afterwards, the signal after the first notch filtering can be further notched at 100kHz.

[0045] Alternatively, if it is determined that there is no narrowband interference, a 100kHz notch filter can be directly applied to obtain a pulse sequence signal in the time domain.

[0046] In step S13, the standard Rowland signal is subjected to notch filtering to obtain a filtered signal; the filtered signal is then subjected to lead modulation and lag modulation to obtain a lead modulation signal and a lag modulation signal, respectively.

[0047] For example, while acquiring the pulse signal to be processed, a standard Rowland signal sequence can be generated at the same sampling rate. The standard Rowland signal is then subjected to a 100kHz notch filter to obtain the sequence corresponding to the unmodulated "0". This sequence is then modulated with lead and lag at 1-microsecond modulation intervals, corresponding to "-" and "+" modulation respectively, to obtain the lead-modulated signal and the lag-modulated signal. The unmodulated filtered signal, the lead-modulated signal, and the lag-modulated signal are used as three standard pulse sequences.

[0048] In step S14, the time-domain pulse signal is multiplied by the filtered signal, the lead modulation signal, and the lag modulation signal to obtain the corresponding first cumulative value, second cumulative value, and third cumulative value; and the corresponding data modulation method is determined based on the maximum cumulative value.

[0049] Specifically, refer to Figure 2 As shown, the time-domain pulse sequence signal to be demodulated obtained in step S12 can be multiplied and added to the three standard pulse sequences obtained in step S13 to obtain three cumulative values. The modulation method corresponding to the maximum value among these three cumulative values ​​is then determined.

[0050] In this exemplary embodiment, a modulation pulse of "0" is used as an example to process the pulse signal. Without loss of generality, random noise is added to the signal; in this example, the signal-to-noise ratio is -5dB. A 95kHz narrowband interference signal is also added to replace the received signal of the enhanced Loland system. The specific steps of the data demodulation method for the enhanced Loland system based on notch filtering are as follows: (1) The filter parameters are set according to the frequency response characteristics of the notch filter and the frequency domain characteristics of the enhanced Loran signal. In this algorithm, the Q value is 5.

[0051] (2) Receive a signal at a constant sampling rate, acquire a pulse sequence, set the sampling rate to 2MHz, the data volume of a single pulse to 2000 points, the modulation mode to "0", add random noise with a signal-to-noise ratio of -20dB, and add a 95kHz narrowband interference signal. There are two cases: a) the amplitude of the narrowband interference is 0.5 times the amplitude of the Loran signal, equivalent to SIR=6dB; b) the amplitude of the narrowband interference is twice the amplitude of the Loran signal, equivalent to SIR=-6dB, representing the degree of interference of the continuous wave on the Loran signal. Perform an FFT transformation to obtain the frequency domain amplitude value. In case a), the narrowband interference is submerged in noise; in case b), there is a clear corresponding frequency point. See [reference needed]. Figure 4 As shown.

[0052] (3) Narrowband interference judgment: If narrowband interference exists, the notch filter set in (1) is used to perform notch processing at that frequency point, and then further notch processing at 100kHz is performed. If it is determined that there is no narrowband interference, notch processing at 100kHz is performed directly to obtain the pulse signal in the time domain. In the embodiment, the narrowband interference in case a) is determined to be without interference, and notch processing at 100kHz is performed directly; in case b), it is determined that there is narrowband interference, the frequency of the narrowband interference is 95.5kHz, notch processing at that frequency point is performed first, and then notch processing at 100kHz is performed further to obtain the notched signal sequence, denoted as SS, as follows. Figure 5 As shown.

[0053] (4) Generation of three standard pulse sequences: standard Loran signals are generated according to the same sampling rate. The signals are notched to obtain signal sequence S. The modulation interval is 1 microsecond. When the sampling rate is 2MHz, the number of data modulations is 2. The "-" modulation sequence is set to S-=[S(3:2000), S(1:2)], and the "+" modulation sequence is set to S+=[S(1999:2000), S(1:1998)].

[0054] (5) The SS sequence is multiplied by the three sequences S, S-, and S+ respectively, and then added to obtain three cumulative values. The cumulative calculation results in case a) are [80.78, 66.39, 70.63], and the cumulative calculation results in case b) are [20.71, 16.13, 18.52]. The maximum value is in the first position, which corresponds to "0" modulation. Note that a random seed is set when adding random noise; otherwise, the random noise will change, and the calculation results will also show data differences.

[0055] As can be seen from the above embodiments, the enhanced Loran signal data demodulation method based on notch filtering can achieve data demodulation under conditions containing noise and in-band interference, and effectively suppress the influence of in-band interference. Simulation results of the accuracy of pulse demodulation as the signal-to-noise ratio changes show that this method is significantly better than the pulse correlation matching method, with a demodulation accuracy of better than 80% at a signal-to-noise ratio of -10dB.

[0056] In another embodiment, reference Figure 7 This paper provides an enhanced Loran system data demodulation method based on notch filtering, characterized in that the method includes: Step S21: Obtain the pulse signal to be processed; perform notch filtering on the pulse signal to obtain a filtered signal; identify whether there is continuous wave interference in the filtered signal; and call the corresponding notch filtering strategy according to the identification result to perform notch filtering and obtain the corresponding single pulse signal; and Step S22: Perform linear judgment and analysis on the pulse signal to be processed to obtain a reference signal; perform notch filtering and FFT transformation on the reference signal in sequence to obtain the corresponding frequency domain pulse signal; Step S23: Identify whether there is continuous wave interference in the frequency band of the frequency domain pulse signal, and call the corresponding notch processing strategy to perform notch processing based on the identification result to obtain the corresponding time domain pulse signal. Step S24: Modulate the time-domain pulse signal according to a preset modulation rule to obtain the corresponding lead modulation signal, lag modulation signal and excitation reference signal; Step S25: Perform inner product operations on the single pulse signal with the lead modulation signal, the lag modulation signal and the excitation reference signal respectively to obtain the corresponding first cumulative value, second cumulative value and third cumulative value; and determine the corresponding data modulation mode based on the maximum cumulative value.

[0057] For example, the time-domain pulse signal is modulated according to a preset modulation rule to obtain the corresponding lead modulation signal, lag modulation signal, and excitation reference signal, including: The time-domain pulse signal is subjected to lead modulation and lag modulation respectively to obtain the lead modulation signal, the lag modulation signal and the excitation reference signal.

[0058] For example, based on the recognition result, the corresponding notch filtering strategy is invoked to perform notch filtering, including: If continuous wave interference is detected, the target notch filter is invoked to filter the frequency domain signal; otherwise, no processing is performed if continuous wave interference is detected.

[0059] Specifically, refer to Figure 8 As shown, a matched correlation demodulation method with notch filtering is provided. Considering the presence of continuous wave interference (CWI) in the received signal, both the reference pulse signal and the currently received pulse signal to be demodulated need to undergo notch filtering. The reference pulse is a noise-free standard signal. Specifically, taking into account the modulation characteristics of the enhanced Loran system (eLoran) signal, the first two pulses in the pulse group do not employ pulse position modulation (PPM) technology. These two pulses can be processed by linear discriminant analysis (LDA) to achieve noise suppression.

[0060] Next, the presence of continuous wave interference (CWI) in the filtered signal obtained after notch filtering can be determined. If CWI is detected, notch filtering is performed again to filter the interfering signal. In-band CWI can be identified through frequency domain analysis. For example, if the power of the interfering signal is much smaller than the power of the eLoran system signal, its amplitude characteristics in the frequency domain are not obvious. In this case, the frequency corresponding to the maximum amplitude value will be concentrated around 100 kHz, indicating that there is no CWI in the signal. Conversely, the amplitude of the interfering signal in the frequency domain will be relatively high, and the corresponding frequency will deviate significantly from 100 kHz. Specifically, the frequency domain amplitude after the signal undergoes Fast Fourier Transform (FFT) is normalized. If the amplitude difference between the interfering signal and the eLoran system signal is greater than 0.15, the signal is determined to contain CWI.

[0061] When continuous wave interference is detected, and the target notch filter is invoked to perform notch filtering on the frequency domain signal, the notch filter can be the target filter described in the above embodiments.

[0062] By designing a two-step notch filter, the suppression of random noise and in-band continuous wave interference is achieved, thereby improving demodulation performance.

[0063] In another embodiment, reference Figure 9 This paper provides an enhanced Loran system data demodulation method based on notch filtering, characterized in that the method includes: Step S31: Obtain the pulse signal to be processed; perform notch filtering on the pulse signal to obtain a filtered signal; identify whether there is continuous wave interference in the filtered signal; and call the corresponding notch filtering strategy to perform notch filtering based on the identification result, and construct a pulse signal group; and Step S32: Perform linear judgment and analysis on the pulse signal to be processed to obtain a reference signal; sequentially perform notch filtering and FFT transformation on the reference signal to obtain the corresponding frequency domain pulse signal; Step S33: Identify whether there is continuous wave interference in the frequency domain pulse signal, and call the corresponding notch processing strategy to perform notch processing based on the identification result to obtain the corresponding time domain pulse signal. Step S34: Modulate the time-domain pulse signal according to a preset modulation rule to obtain the corresponding lead modulation signal, lag modulation signal and excitation reference signal, and construct a mode library; Step S35: Perform inner product operation between each pulse signal in the pulse signal group and each signal in the mode library to obtain the corresponding cumulative value; and determine the corresponding data modulation mode based on the maximum cumulative value.

[0064] Specifically, a mode matching correction method integrating notch filtering is provided, referencing... Figure 10 As shown, for the currently received pulse signal, after performing a first 100kHz notch filtering and a second notch filtering when continuous wave interference is detected, a pulse group can be constructed as the signal to be demodulated. Simultaneously, for the reference signal, after the first 100kHz notch filtering, FFT transformation, and the second notch filtering when continuous wave interference is detected, a pattern library can be constructed based on three single pulses. The pattern library includes: a lead modulation signal, a lag modulation signal, and an excitation reference signal (the unprocessed time-domain pulse signal) obtained after modulating the time-domain pulse signal. Therefore, each pulse signal in the pulse group can be multiplied by each signal in the pattern library to obtain the corresponding accumulated value; and the corresponding data modulation method can be determined based on the maximum accumulated value.

[0065] The advantage of this method lies in its ability to avoid the unbalanced modulation phenomenon generated during single-pulse demodulation, thereby improving demodulation performance. Simultaneously, by applying notch filtering to both the received signal to be demodulated and the reference signal, noise is effectively suppressed and the signal-to-noise ratio is improved.

[0066] It should be noted that the above figures are merely illustrative of the processes included in the method according to exemplary embodiments of the present invention, and are not intended to be limiting. It is readily understood that the processes shown in the above figures do not indicate or limit the temporal order of these processes. Furthermore, it is readily understood that these processes may, for example, be executed synchronously or asynchronously in multiple modules.

[0067] It should be noted that although several modules or units of the device for performing actions have been mentioned in the detailed description above, this division is not mandatory. In fact, according to embodiments of the present invention, the features and functions of two or more modules or units described above can be embodied in one module or unit. Conversely, the features and functions of one module or unit described above can be further divided and embodied by multiple modules or units.

[0068] Figure 11 A schematic diagram of an electronic device suitable for implementing embodiments of the present invention is shown.

[0069] It should be noted that, Figure 11 The electronic device 1000 shown is merely an example and should not be construed as limiting the functionality and scope of use of the embodiments of the present invention.

[0070] like Figure 11 As shown, the electronic device 1000 includes a Central Processing Unit (CPU) 1001, which can perform various appropriate actions and processes based on programs stored in Read-Only Memory (ROM) 1002 or programs loaded from storage section 1008 into Random Access Memory (RAM) 1003. The RAM 1003 also stores various programs and data required for system operation. The CPU 1001, ROM 1002, and RAM 1003 are interconnected via a bus 1004. An Input / Output (I / O) interface 1005 is also connected to the bus 1004. Furthermore, the electronic device 1000 also includes an FPGA device and a System-on-a-Chip (SoC) device.

[0071] The following components are connected to I / O interface 1005: an input section 1006 including a keyboard, mouse, etc.; an output section 1007 including a cathode ray tube (CRT), liquid crystal display (LCD), etc., and speakers, etc.; a storage section 1008 including a hard disk, etc.; and a communication section 1009 including a network interface card such as a LAN (Local Area Network) card, modem, etc. The communication section 1009 performs communication processing via a network such as the Internet. A drive 1010 is also connected to I / O interface 1005 as needed. Removable media 1011, such as a disk, optical disk, magneto-optical disk, semiconductor memory, etc., are installed on drive 1010 as needed so that computer programs read from them can be installed into storage section 1008 as needed.

[0072] In particular, according to embodiments of the present invention, the processes described below with reference to the flowcharts can be implemented as computer software programs. For example, embodiments of the present invention include a computer program product comprising a computer program carried on a storage medium, the computer program containing program code for performing the methods shown in the flowcharts. In such embodiments, the computer program can be downloaded and installed from a network via communication section 1009, and / or installed from removable medium 1011. When the computer program is executed by central processing unit (CPU) 1001, it performs various functions defined in the system of this application.

[0073] Specifically, the aforementioned electronic devices can be airborne intelligent electronic devices, such as airborne video processing equipment.

[0074] It should be noted that the storage medium shown in the embodiments of the present invention can be a computer-readable signal medium or a computer-readable storage medium, or any combination thereof. A computer-readable storage medium can be, for example,—but not limited to—an electrical, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any combination thereof. More specific examples of a computer-readable storage medium may include, but are not limited to: an electrical connection having one or more wires, a portable computer disk, a hard disk, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM), flash memory, optical fiber, portable compact disc read-only memory (CD-ROM), optical storage device, magnetic storage device, or any suitable combination thereof. In the present invention, a computer-readable storage medium can be any tangible medium containing or storing a program that can be used by or in conjunction with an instruction execution system, apparatus, or device. In the present invention, a computer-readable signal medium can include a data signal propagated in baseband or as part of a carrier wave, wherein computer-readable program code is carried. Such transmitted data signals can take various forms, including but not limited to electromagnetic signals, optical signals, or any suitable combination thereof. The computer-readable signal medium can also be any storage medium other than a computer-readable storage medium, which can send, propagate, or transmit a program for use by or in connection with an instruction execution system, apparatus, or device. The program code contained on the storage medium can be transmitted using any suitable medium, including but not limited to wireless, wired, etc., or any suitable combination thereof.

[0075] The flowcharts and block diagrams in the accompanying drawings illustrate the architecture, functionality, and operation of possible implementations of systems, methods, and computer program products according to various embodiments of the present invention. In this regard, each block in a flowchart or block diagram may represent a module, segment, or portion of code containing one or more executable instructions for implementing a specified logical function. It should also be noted that in some alternative implementations, the functions indicated in the blocks may occur in a different order than those indicated in the drawings. For example, two consecutively indicated blocks may actually be executed substantially in parallel, and they may sometimes be executed in reverse order, depending on the functions involved. It should also be noted that each block in a block diagram or flowchart, and combinations of blocks in a block diagram or flowchart, may be implemented using a dedicated hardware-based system that performs the specified function or operation, or using a combination of dedicated hardware and computer instructions.

[0076] The units described in the embodiments of the present invention can be implemented in software or hardware, and the described units can also be located in a processor. The names of these units do not necessarily limit the specific unit itself.

[0077] It should be noted that, as another aspect, this application also provides a storage medium, which may be included in an electronic device or may exist independently without being assembled into the electronic device. The aforementioned storage medium carries one or more programs, which, when executed by an electronic device, cause the electronic device to perform the methods described in the following embodiments. For example, the electronic device may perform... Figure 1 The steps of the method shown.

[0078] In one embodiment, this application provides a computer program product including a computer program that, when executed by a processor, implements the steps in the above-described method embodiments.

[0079] Furthermore, the above figures are merely illustrative of the processes included in the method according to exemplary embodiments of the present invention, and are not intended to be limiting. It is readily understood that the processes shown in the above figures do not indicate or limit the temporal order of these processes. Additionally, it is readily understood that these processes may be executed synchronously or asynchronously, for example, in multiple modules.

[0080] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention herein. This application is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The specification and embodiments are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the claims.

[0081] It should be understood that the present invention is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A data demodulation method for an enhanced Loran system based on notch filtering, characterized in that, The method includes: Obtain the pulse sequence to be processed, and perform FFT transformation on the pulse sequence to obtain the corresponding frequency domain pulse signal; The system identifies whether there is narrowband interference within the frequency band of the frequency domain pulse signal, and calls the corresponding notch filtering strategy to perform notch filtering based on the identification result, thereby obtaining the corresponding time domain pulse signal. The standard Loran signal is notched to obtain a filtered signal; the filtered signal is then modulated with lead modulation and lag modulation to obtain the lead modulation signal and lag modulation signal, respectively. The time-domain pulse signal is multiplied by the filtered signal, the lead modulation signal, and the lag modulation signal to obtain the corresponding first, second, and third cumulative values; and the corresponding data modulation method is determined based on the maximum cumulative value.

2. The method according to claim 1, characterized in that, The system identifies whether narrowband interference exists within the frequency domain signal and applies the corresponding notch filtering strategy based on the identification result, including: When narrowband interference is detected, the target notch filter is invoked to perform a first notch filter on the frequency points of the frequency domain signal where narrowband interference exists; and then, the signal after the first notch filter is subjected to a notch filter based on 100kHz to obtain a time-domain pulse signal; or When it is determined that there is no narrowband interference, the frequency domain signal is subjected to notch filtering based on 100kHz to obtain the time domain pulse signal.

3. The method according to claim 2, characterized in that, The target notch filter is invoked to perform the first notch filtering on the frequency points where narrowband interference exists in the frequency domain signal, including: in, Indicates the angular frequency at which notch filtering is required; , This represents a parameter related to the quality factor of a notch filter.

4. The method according to claim 1, characterized in that, Obtain the pulse sequence to be processed, including: The pulse signal is received based on a constant target sampling rate, and a pulse sequence to be processed is constructed based on the received pulse signal.

5. The method according to claim 4, characterized in that, The method further includes: A standard Roland signal is generated based on the target sampling rate.

6. A data demodulation method for an enhanced Loran system based on notch filtering, characterized in that, The method includes: The system acquires the pulse signal to be processed, performs notch filtering on the pulse signal to obtain a filtered signal, identifies whether there is continuous wave interference in the filtered signal, and calls the corresponding notch filtering strategy to perform notch filtering based on the identification result, thereby obtaining the corresponding single pulse signal; and The pulse signal to be processed is linearly analyzed to obtain a reference signal; the reference signal is then subjected to notch filtering and FFT transformation to obtain the corresponding frequency domain pulse signal. The system identifies whether there is continuous wave interference within the frequency band in the frequency domain pulse signal, and calls the corresponding notch filtering strategy to perform notch filtering based on the identification result, thereby obtaining the corresponding time domain pulse signal. The time-domain pulse signal is modulated according to a preset modulation rule to obtain the corresponding lead modulation signal, lag modulation signal and excitation reference signal; The single pulse signal is multiplied by the lead modulation signal, the lag modulation signal and the excitation reference signal to obtain the corresponding first cumulative value, second cumulative value and third cumulative value; and the corresponding data modulation mode is determined according to the maximum cumulative value.

7. The method according to claim 6, characterized in that, The time-domain pulse signal is modulated according to a preset modulation rule to obtain the corresponding lead modulation signal, lag modulation signal, and excitation reference signal, including: The time-domain pulse signal is subjected to lead modulation and lag modulation respectively to obtain the lead modulation signal, the lag modulation signal and the excitation reference signal.

8. The method according to claim 6, characterized in that, Based on the recognition results, the corresponding notch filtering strategy is invoked to perform notch filtering, including: When continuous wave interference is confirmed, the target notch filter is invoked to filter the frequency domain signal; or If it is determined that there is no continuous wave interference, no action is taken.

9. A data demodulation method for an enhanced Loran system based on notch filtering, characterized in that, The method includes: The system acquires the pulse signal to be processed, performs notch filtering on the pulse signal to obtain a filtered signal, identifies whether there is continuous wave interference in the filtered signal, and calls the corresponding notch filtering strategy to perform notch filtering based on the identification result, and constructs a pulse signal group; and The pulse signal to be processed is linearly analyzed to obtain a reference signal; the reference signal is then subjected to notch filtering and FFT transformation to obtain the corresponding frequency domain pulse signal. The system identifies whether there is continuous wave interference in the frequency domain pulse signal, and calls the corresponding notch filtering strategy to perform notch filtering based on the identification result, thereby obtaining the corresponding time domain pulse signal. The time-domain pulse signal is modulated according to a preset modulation rule to obtain the corresponding lead modulation signal, lag modulation signal and excitation reference signal, and a mode library is constructed. Each pulse signal in the pulse signal group is multiplied by each signal in the pattern library to obtain the corresponding cumulative value; and the corresponding data modulation method is determined based on the maximum cumulative value.

10. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by the processor, it implements the enhanced Roland system data demodulation method based on notch filtering as described in any one of claims 1 to 9.

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