A method and system for adaptive filtering response in the VHF band

Abstract

The application discloses a VHF frequency band adaptive filtering response method and system, and relates to the field of VHF frequency band signal processing.The application effectively solves the problems of signal interference and multipath effect in VHF frequency band communication through the adaptive filtering response method, and realizes accurate separation of reflected path signals and main path signals through time domain and frequency domain analysis, combination of a delay detection algorithm and an adaptive filtering algorithm.Further, the interference of the reflected path signals is eliminated through a phase cancellation mechanism, and the transmission quality of the signals is significantly improved.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of VHF frequency band signal processing, in particular to a VHF frequency band adaptive filtering response method and system. BACKGROUND

[0002] The VHF frequency band (Very High Frequency) is located in the frequency range of 30MHz to 300MHz, and is an important frequency band in the field of wireless communication. In the VHF frequency band, the signal has relatively good propagation characteristics, especially in terms of line-of-sight propagation and ground reflection propagation, making it an ideal choice for aviation, navigation, television broadcasting and military communication. With the rapid development of wireless communication technology, the application scenarios of the VHF frequency band are continuously expanding, including automatic identification system (AIS), private business (ASM) and VHF data exchange (VDE) and other communication modes. However, the electromagnetic environment of the VHF frequency band is complex, and the mutual interference problem between devices is increasingly prominent, especially in dense urban environments or areas with dense electronic devices. In addition, due to the longer wavelength of the VHF frequency band, the effects of multipath and reflected path signals on communication quality are particularly evident.

[0003] Although the VHF frequency band communication technology has been widely applied in many fields, the existing technology still has deficiencies in dealing with signal interference, multipath effect and reflected path signal. Traditional filter design methods, such as Wiener filter, rely on prior knowledge of signal characteristics, but in practical applications, it is often difficult to obtain such knowledge. In addition, adaptive filtering algorithms with fixed step size have a trade-off between convergence speed, time-varying system tracking speed and convergence accuracy, making it difficult to meet the requirements of fast convergence and high accuracy at the same time. In a complex electromagnetic environment, how to effectively separate the main path signal and the reflected path signal, and improve the transmission quality and reliability of the signal, is an important challenge faced by the VHF frequency band communication technology. SUMMARY

[0004] The present application proposes a VHF frequency band adaptive filtering response method and system, which improves the anti-interference ability of VHF frequency band communication and provides an effective solution for communication in complex electromagnetic environments.

[0005] The VHF frequency band adaptive filtering response method comprises the following steps:

[0006] S1. Receive the mixed signal of the VHF frequency band, the mixed signal comprising a main path signal and a plurality of frequency points of reflected path signals; perform time domain and frequency domain analysis on the received mixed signal, and use Fourier transform to obtain frequency and phase information;

[0007] S2. Detect the time delay and phase difference between the main path signal and the reflected path signal using a delay detection algorithm; use an adaptive filtering algorithm to gradually adjust the filter coefficients to separate the reflected path signal from the main path signal; perform feature analysis on the extracted reflected path signals to extract the amplitude, phase, and delay of each reflected path signal;

[0008] S3. By adjusting the phase cancellation mechanism, the phase of the reflected path signal is canceled with the phase of the main path signal to generate a cancellation signal;

[0009] Wherein, the step S3 specifically includes the following sub-steps:

[0010] S301. According to the extracted phase and delay characteristics of the reflected path signal, the phase of the reflected path signal is adjusted so that the phase difference between the phase of the reflected path signal and the main path signal at each frequency point is π, and the phase cancellation angle is obtained;

[0011] S302. According to the phase cancellation angle, a signal for canceling the reflected path signal is constructed, wherein the amplitude of the generated cancellation signal is the same as the amplitude of the original reflected path signal;

[0012] S303. The generated phase cancellation signal is superimposed on the received signal to eliminate reflection interference.

[0013] Furthermore, the step S2 specifically includes the following sub-steps:

[0014] S201. Identify the delay characteristics of each reflection path based on the phase change of the reflected path signal delay in the frequency domain;

[0015] S202. According to the fixed phase offset of the reflected path signal, the phase difference at different frequencies is identified and the phase offset feature is extracted;

[0016] S203. Based on the delay characteristics and phase offset characteristics, separate the signal of each reflected path through frequency domain filtering technology, and identify the amplitude characteristics of the reflected path by calculating the attenuation of the reflected path signal relative to the main path signal;

[0017] S204. Combining the time delay characteristics, phase shift characteristics, and amplitude attenuation characteristics, a signal feature set of the reflection path signal is formed.

[0018] Furthermore, in step S301, the phase of the reflected path signal is adjusted so that the phase difference between the reflected path signal and the main path signal at each frequency point is π, and the phase cancellation angle is specifically expressed as:

[0019] θ cancel,i =π-θ i ;

[0020] Further expanding, we have:

[0021] θ cancel,i = π - (φ total,i (f i ) + 2πf k τi ) ;

[0022] wherein, the θ cancel,i represents the phase angle of the cancellation signal, the θ i represents the original phase of the reflection path signal at the i-th frequency point, the φ total,i represents the total phase of the reflection path signal at the i-th frequency point, the f i represents the frequency point i, the τ i represents the time delay of the reflection path signal at the i-th frequency point.

[0023] Further, in the step S302, the signal for canceling the reflection path signal is constructed, and the specific process is as follows:

[0024] According to the amplitude of the cancellation signal being the same as the original reflection path signal:

[0025]

[0026] Substituting the phase cancellation angle:

[0027] S cancel,i (f) = A ref,i cos(2πft+π-θ i ) ;

[0028] wherein, the S cancel,i (f) represents the expression of the cancellation signal of the reflection path signal at the i-th frequency point in the frequency domain, the f represents the frequency, the A ref,i represents the amplitude of the reflection path signal at the i-th frequency point, the represents the complex form of the cancellation signal for canceling the reflection path signal at the i-th frequency point, j is the imaginary unit, e is the natural constant, the θ cancal,i represents the phase angle of the cancellation signal, the f i represents the frequency point i, the δ(·) represents the Dirac impulse function, the t represents the instantaneous state of the signal, the θ i represents the original phase of the reflection path signal at the i-th frequency point.

[0029] Further, in the step S303, the generated phase cancellation signal is superimposed with the received signal, and the specific representation is as follows:

[0030] Perform a second Fourier transform on the obtained cancellation signal to convert the frequency domain into the time domain:

[0031] S cancel,i (t) = A ref,i cos(2πft+θ cancel,i )

[0032] During the superposition process, the main path signal is combined with the cancellation signal to eliminate interference. After phase cancellation, the newly generated signal contains only the main path signal:

[0033]

[0034] Among them, the S cancel,i (t) represents the expression of the cancellation signal of the reflected path signal at the i-th frequency point in the time domain, and the A ref,i represents the amplitude of the reflected path signal at the i-th frequency point, the θ cancel,i represents the phase angle of the cancellation signal, f represents the frequency, t represents the instantaneous state of the signal, and Y new (t) represents the expression of the new signal after superposition in the time domain, and the S main (t) represents the expression of the main path signal in the time domain, and the S ref,i (t) represents the expression of the reflection path signal at the i-th frequency point in the time domain, N represents the number of reflection paths, and i represents the index.

[0035] Furthermore, a VHF band adaptive filtering response system is provided, which is implemented based on any one of the above-mentioned VHF band adaptive filtering response methods, and includes:

[0036] A signal preprocessing module is configured to receive a mixed signal in the VHF band, the mixed signal comprising a main path signal and reflected path signals at multiple frequency points; perform time domain and frequency domain analysis on the received mixed signal, and obtain frequency and phase information using Fourier transform;

[0037] The signal separation module is used to detect the time delay and phase difference between the main path signal and the reflected path signal using a delay detection algorithm; use an adaptive filtering algorithm to gradually adjust the filter coefficients to separate the reflected path signal from the main path signal; perform feature analysis on the extracted reflected path signals to extract the amplitude, phase, and delay of each reflected path signal;

[0038] A signal cancellation module is used to cancel the phase of the reflected path signal with the phase of the main path signal by adjusting the phase cancellation mechanism to generate a cancellation signal;

[0039] The signal cancellation module specifically includes:

[0040] The phase cancellation angle calculation unit adjusts the phase of the reflected path signal based on the extracted phase and delay characteristics of the reflected path signal so that the phase difference between the reflected path signal and the main path signal at each frequency point is π, thereby obtaining the phase cancellation angle;

[0041] a cancellation signal generating unit, configured to construct a signal for canceling the reflected path signal according to the phase cancellation angle, wherein the amplitude of the generated cancellation signal is the same as the amplitude of the original reflected path signal;

[0042] The signal superposition unit is used to generate a phase cancellation signal and superimpose it on the received signal to eliminate reflection interference.

[0043] Furthermore, the signal separation module specifically includes:

[0044] The delay feature extraction module is used to identify the delay feature of each reflection path based on the phase change of the reflection path signal delay in the frequency domain;

[0045] A phase offset feature extraction module is used to identify phase differences at different frequencies and extract phase offset features based on the fixed phase offset of the reflected path signal.

[0046] The amplitude feature extraction module is used to separate the signal of each reflection path through frequency domain filtering technology based on the time delay characteristics and phase offset characteristics, and to identify the amplitude characteristics of the reflection path by calculating the attenuation of the amplitude of the reflection path signal relative to the main path signal;

[0047] The feature integration module is used to integrate the time delay feature, phase shift feature and amplitude attenuation feature to form a signal feature set of the reflection path signal.

[0048] Furthermore, in the phase cancellation angle calculation unit, the phase of the reflected path signal is adjusted so that the phase difference between the reflected path signal and the main path signal at each frequency point is π, and the obtained phase cancellation angle is specifically expressed as:

[0049] θ cancel,i =π-θ i ;

[0050] Further expansion yields:

[0051] θ cancel,i =π-(φ total,i (f i )+2πf k τ i );

[0052] Among them, the θ cancel,i The phase angle of the cancellation signal, θ irepresents the original phase of the reflected path signal at the i-th frequency point, the φ total,i represents the total phase of the reflected path signal at the i-th frequency point, the f i represents the frequency point i, the τ i Represents the time delay of the reflected path signal at the i-th frequency point.

[0053] Furthermore, in the cancellation signal generating unit, the specific process of constructing a signal for canceling the reflected path signal is as follows: based on the amplitude of the cancellation signal being the same as the original reflected path signal:

[0054]

[0055] Substituting the phase cancellation angle:

[0056] S cancel,i (f) = A ref,i cos(2πft+π-θ i );

[0057] Among them, the S cancel,i (f) represents the expression of the cancellation signal of the reflected path signal at the i-th frequency point in the frequency domain, where f represents the frequency, and A ref,i represents the amplitude of the reflected path signal at the i-th frequency point, represents the complex cancellation signal used to cancel the reflected path signal at the i-th frequency point, j is an imaginary unit, e is a natural constant, and the θ cancel,i represents the phase angle of the cancellation signal, the f i represents the frequency point i, the δ(·) represents the Dirac impulse function, the t represents the instantaneous state of the signal, and the θ i Represents the original phase of the reflected path signal at the i-th frequency point.

[0058] Furthermore, in the signal superposition unit, the generated phase cancellation signal is superimposed on the received signal as follows: the obtained cancellation signal is subjected to a second Fourier transform to convert the frequency domain into the time domain:

[0059] S cancel,i (t) = A ref,i cos(2πft+θ cancel,i )

[0060] During the superposition process, the main path signal is combined with the cancellation signal to eliminate interference. After phase cancellation, the newly generated signal contains only the main path signal:

[0061]

[0062] Among them, the S cancel,i(t) represents the expression of the cancellation signal of the reflected path signal at the i-th frequency point in the time domain, and the A ref,i represents the amplitude of the reflected path signal at the i-th frequency point, the θ cancel,i represents the phase angle of the cancellation signal, f represents the frequency, t represents the instantaneous state of the signal, and Y new (t) represents the expression of the new signal after superposition in the time domain, and the S main (t) represents the expression of the main path signal in the time domain, and the S ref,i (t) represents the expression of the reflection path signal at the i-th frequency point in the time domain, N represents the number of reflection paths, and i represents the index.

[0063] The beneficial effects of the invention are:

[0064] This invention effectively addresses signal interference and multipath effects in VHF band communications through an adaptive filtering response method. It also achieves precise separation of reflected path signals from the main path signal through time and frequency domain analysis, combined with a delay detection algorithm and an adaptive filtering algorithm. Furthermore, a phase cancellation mechanism eliminates interference from reflected path signals, significantly improving signal transmission quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] Figure 1 A flowchart of a method for adaptive filtering response in the VHF band provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0066] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings, but the protection scope of the present invention is not limited to the following.

[0067] In order to make the objectives, technical solutions, and advantages of the present invention more clearly understood, the present invention is further described in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only intended to explain the present invention and are not intended to limit the present invention. That is, the embodiments described herein are only some embodiments of the present invention, not all embodiments. Generally, the components of the embodiments of the present invention described and illustrated in the drawings herein may be arranged and designed in various different configurations.

[0068] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without making any creative work shall fall within the scope of protection of the present invention. It should be noted that relational terms such as "first" and "second" are merely used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations.

[0069] Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to encompass non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus. In the absence of further limitations, an element defined by the phrase "comprising a ..." does not preclude the presence of additional identical elements in the process, method, article, or apparatus that includes the element.

[0070] The features and performance of the present invention are further described in detail below with reference to the embodiments.

[0071] Among them, since VHF signals are easily affected by reflections from the ground and obstacles, especially in cities or complex terrains, the superposition of reflected path signals and main path signals will lead to multipath interference. An adaptive filtering response method for the VHF band is proposed, such as Figure 1 , including the following steps:

[0072] S1 receives a mixed signal in the VHF band, the mixed signal including a main path signal and a reflected path signal at multiple frequency points; performs time domain and frequency domain analysis on the received mixed signal, and obtains frequency and phase information using Fourier transform;

[0073] S2. Detect the time delay and phase difference between the main path signal and the reflected path signal using a delay detection algorithm; use an adaptive filtering algorithm to gradually adjust the filter coefficients to separate the reflected path signal from the main path signal; perform feature analysis on the extracted reflected path signals to extract the amplitude, phase, and delay of each reflected path signal;

[0074] S3. By adjusting the phase cancellation mechanism, the phase of the reflected path signal is canceled with the phase of the main path signal to generate a cancellation signal;

[0075] Wherein, the step S3 specifically includes the following sub-steps:

[0076] S301. According to the extracted phase and delay characteristics of the reflected path signal, the phase of the reflected path signal is adjusted so that the phase difference between the phase of the reflected path signal and the main path signal at each frequency point is π, and the phase cancellation angle is obtained;

[0077] S302. According to the phase cancellation angle, a signal for canceling the reflected path signal is constructed, wherein the amplitude of the generated cancellation signal is the same as the amplitude of the original reflected path signal;

[0078] S303. The generated phase cancellation signal is superimposed on the received signal to eliminate reflection interference.

[0079] Furthermore, the step S2 specifically includes the following sub-steps:

[0080] S201. Identify the delay characteristics of each reflection path based on the phase change of the reflected path signal delay in the frequency domain;

[0081] Specifically, the time delay is extracted by analyzing the change of the phase of the reflected path signal with frequency. For the i-th reflected path, the phase delay of the signal is expressed as:

[0082] Δφ i (f)=-2πfτ i ;

[0083] Wherein, the Δφ i (f) is the frequency domain representation of the phase change of the reflected path signal at the i-th frequency point, and the τ i represents the time delay of the reflected path signal at the i-th frequency point;

[0084] The frequency phase change is further obtained through phase measurement to solve the time delay:

[0085]

[0086] Further expansion, the phase change corresponding to each frequency point in the frequency range is:

[0087] Δφ i (f i )=-2πf i τ i ;

[0088] Fitting Δφ by linear regression i (f i ) and f i τ i .

[0089] S202. According to the fixed phase offset of the reflected path signal, the phase difference at different frequencies is identified and the phase offset feature is extracted;

[0090] Specifically, the phase offset is caused by the fixed phase difference on the reflection path. For each reflection path, the total phase is expressed as:

[0091] φ total,i (f)=-2πfτ i +θ i ;

[0092] Measure the total phase φ at different frequency points total,i (f) Extract the phase offset by eliminating the delay effect:

[0093] θ i =φ total,i (f i )+2πf i τ i .

[0094] S203. Based on the delay characteristics and phase offset characteristics, separate the signal of each reflected path through frequency domain filtering technology, and identify the amplitude characteristics of the reflected path by calculating the attenuation of the reflected path signal relative to the main path signal;

[0095] Specifically, for the amplitude of the reflected path signal at each frequency point, the relative attenuation to the main path signal amplitude is calculated and extracted:

[0096]

[0097] Among them, a i Indicates amplitude.

[0098] S204. Comprehensive delay characteristics, phase shift characteristics and amplitude attenuation characteristics to form a signal feature set {τ i ,θ i 、a i}.

[0099] Furthermore, in step S301, the phase of the reflected path signal is adjusted so that the phase difference between the reflected path signal and the main path signal at each frequency point is π, and the phase cancellation angle is specifically expressed as:

[0100] θ cancel,i =π-θ i ;

[0101] Further expansion yields:

[0102] θ cancel,i =π-(φ total,i (f i )+2πf i τ i );

[0103] Among them, the θ cancel,i represents the phase angle of the cancellation signal, the θ i represents the original phase of the reflected path signal at the i-th frequency point, the φ total,i represents the total phase of the reflected path signal at the i-th frequency point, the f i represents the frequency point i, the τ i Represents the time delay of the reflected path signal at the i-th frequency point.

[0104] Furthermore, in step S302, the specific process of constructing a signal for canceling the reflected path signal is as follows:

[0105] The amplitude of the cancellation signal is the same as the original reflected path signal:

[0106]

[0107] Substituting the phase cancellation angle:

[0108] S cancel,i (f) = A ref,i cos(2πft+π-θ i );

[0109] Among them, the S cancel,i (f) represents the expression of the cancellation signal of the reflected path signal at the i-th frequency point in the frequency domain, where f represents the frequency, and A ref,i represents the amplitude of the reflected path signal at the i-th frequency point, represents the complex cancellation signal used to cancel the reflected path signal at the i-th frequency point, j is an imaginary unit, e is a natural constant, and the θ cancel,i represents the phase angle of the cancellation signal, the f i represents the frequency point i, the δ(·) represents the Dirac impulse function, the t represents the instantaneous state of the signal, and the θ i Represents the original phase of the reflected path signal at the i-th frequency point.

[0110] Furthermore, in step S303, the generated phase cancellation signal is superimposed on the received signal as follows:

[0111] Perform a second Fourier transform on the obtained cancellation signal to convert the frequency domain into the time domain:

[0112] S cancel,i (t) = A ref,i cos(2πft+θ cancel,i )

[0113] During the superposition process, the main path signal is combined with the cancellation signal to eliminate interference. After phase cancellation, the newly generated signal contains only the main path signal:

[0114]

[0115] Among them, the S cancel,i (t) represents the expression of the cancellation signal of the reflected path signal at the i-th frequency point in the time domain, and the A ref,i represents the amplitude of the reflected path signal at the i-th frequency point, the θ cancel,i represents the phase angle of the cancellation signal, f represents the frequency, t represents the instantaneous state of the signal, and Y new (t) represents the expression of the new signal after superposition in the time domain, and the S main (t) represents the expression of the main path signal in the time domain, and the S ref,i (t) represents the expression of the reflection path signal at the i-th frequency point in the time domain, N represents the number of reflection paths, and i represents the index.

[0116] Furthermore, in the above embodiment, the specific process of performing time domain and frequency domain analysis on the received mixed signal and obtaining frequency and phase information using Fourier transform mentioned in step S1 is as follows:

[0117] Perform Fourier transform on the mixed signal to obtain the frequency domain representation:

[0118]

[0119] Here, (f) is the representation in the frequency domain; further, the Fourier transform here is specifically: Where S(f) is the representation of the signal in the frequency domain, and S(t) is the representation of the signal in the time domain. Substituting the above formula into the main path signal and the reflected path signal of this embodiment, we have:

[0120] Main path signal:

[0121]

[0122] By substitution method, we can further obtain:

[0123]

[0124] Similarly, the Fourier transform of the reflected path signal can be processed similarly to obtain:

[0125]

[0126] Among them, φ main Represents the total phase of the main path signal, φref,i represents the total phase of the i-th reflection path.

[0127] Specifically, in the above embodiment, the mixed signal includes a main path signal and reflected path signals at multiple frequency points. The purpose is to identify and separate the reflected path signals at multiple frequency points through the above implementation scheme, calculate the cancellation signal of the reflected path signal at each frequency point, and perform phase cancellation, thereby achieving interference suppression.

[0128] Furthermore, a VHF band adaptive filtering response system is provided, which is implemented based on any one of the above-mentioned VHF band adaptive filtering response methods, and includes:

[0129] A signal preprocessing module is configured to receive a mixed signal in the VHF band, the mixed signal comprising a main path signal and reflected path signals at multiple frequency points; perform time domain and frequency domain analysis on the received mixed signal, and obtain frequency and phase information using Fourier transform;

[0130] The signal separation module is used to detect the time delay and phase difference between the main path signal and the reflected path signal using a delay detection algorithm; use an adaptive filtering algorithm to gradually adjust the filter coefficients to separate the reflected path signal from the main path signal; perform feature analysis on the extracted reflected path signals to extract the amplitude, phase, and delay of each reflected path signal;

[0131] A signal cancellation module is used to cancel the phase of the reflected path signal with the phase of the main path signal by adjusting the phase cancellation mechanism to generate a cancellation signal;

[0132] The signal cancellation module specifically includes:

[0133] The phase cancellation angle calculation unit adjusts the phase of the reflected path signal based on the extracted phase and delay characteristics of the reflected path signal so that the phase difference between the reflected path signal and the main path signal at each frequency point is π, thereby obtaining the phase cancellation angle;

[0134] a cancellation signal generating unit, configured to construct a signal for canceling the reflected path signal according to the phase cancellation angle, wherein the amplitude of the generated cancellation signal is the same as the amplitude of the original reflected path signal;

[0135] The signal superposition unit is used to generate a phase cancellation signal and superimpose it on the received signal to eliminate reflection interference.

[0136] Furthermore, the signal separation module specifically includes:

[0137] The delay feature extraction module is used to identify the delay feature of each reflection path based on the phase change of the reflection path signal delay in the frequency domain;

[0138] A phase offset feature extraction module is used to identify phase differences at different frequencies and extract phase offset features based on the fixed phase offset of the reflected path signal.

[0139] The amplitude feature extraction module is used to separate the signal of each reflection path through frequency domain filtering technology based on the time delay characteristics and phase offset characteristics, and to identify the amplitude characteristics of the reflection path by calculating the attenuation of the amplitude of the reflection path signal relative to the main path signal;

[0140] The feature integration module is used to integrate the time delay feature, phase shift feature and amplitude attenuation feature to form a signal feature set of the reflection path signal.

[0141] Furthermore, in the phase cancellation angle calculation unit, the phase of the reflected path signal is adjusted so that the phase difference between the reflected path signal and the main path signal at each frequency point is π, and the obtained phase cancellation angle is specifically expressed as:

[0142] θ cancel,i =π-θ i ;

[0143] Further expansion yields:

[0144] θ cancel,i =π-(φ total,i (f i )+2πf k τ i );

[0145] Among them, the θ cancel,i The phase angle of the cancellation signal, θ i represents the original phase of the reflected path signal at the i-th frequency point, the φ total,i represents the total phase of the reflected path signal at the i-th frequency point, the f i represents the frequency point i, the τ i Represents the time delay of the reflected path signal at the i-th frequency point.

[0146] Furthermore, in the cancellation signal generating unit, the specific process of constructing a signal for canceling the reflected path signal is as follows: based on the amplitude of the cancellation signal being the same as the original reflected path signal:

[0147]

[0148] Substituting the phase cancellation angle:

[0149] S cancel,i(f) = A ref,i cos(2πft+π-θ i );

[0150] Among them, the S cancel,i (f) represents the expression of the cancellation signal of the reflected path signal at the i-th frequency point in the frequency domain, where f represents the frequency, and A ref,i represents the amplitude of the reflected path signal at the i-th frequency point, represents the complex cancellation signal used to cancel the reflected path signal at the i-th frequency point, j is an imaginary unit, e is a natural constant, and the θ cancel,i represents the phase angle of the cancellation signal, the f i represents the frequency point i, the δ(·) represents the Dirac impulse function, the t represents the instantaneous state of the signal, and the θ i Represents the original phase of the reflected path signal at the i-th frequency point.

[0151] Furthermore, in the signal superposition unit, the generated phase cancellation signal is superimposed on the received signal as follows: the obtained cancellation signal is subjected to a second Fourier transform to convert the frequency domain into the time domain:

[0152] S cancel,i (t) = A ref,i cos(2πft+θ cancel,i )

[0153] During the superposition process, the main path signal is combined with the cancellation signal to eliminate interference. After phase cancellation, the newly generated signal contains only the main path signal:

[0154]

[0155] Among them, the S cancel,i (t) represents the expression of the cancellation signal of the reflected path signal at the i-th frequency point in the time domain, and the A ref,i represents the amplitude of the reflected path signal at the i-th frequency point, the θ cancel,i represents the phase angle of the cancellation signal, f represents the frequency, t represents the instantaneous state of the signal, and Y new (t) represents the expression of the new signal after superposition in the time domain, and the S main (t) represents the expression of the main path signal in the time domain, and the S ref,i (t) represents the expression of the reflection path signal at the i-th frequency point in the time domain, N represents the number of reflection paths, and i represents the index.

[0156] Furthermore, as a preferred implementation of the above embodiment, the specific process principle of the above system is proposed:

[0157] 1. Receive signal acquisition

[0158] First, the filter needs to receive a mixed signal from the antenna, including the ground reflection path signal and the main path signal, and collect the time and frequency domain characteristics of the signal, mainly including the signal amplitude, phase, and delay information.

[0159] 2. Separate the main path signal and the reflected path signal

[0160] The received signal is analyzed in the time and frequency domains, using a Fourier transform (FFT) to obtain frequency and phase information. The multipath delay characteristics of the signal are detected. The main path signal generally reaches the receiver in the shortest possible time, while the reflected path signal has a slight time delay, which is detected using a delay detection algorithm. Phase changes are used to detect signal differences between different paths. An adaptive filtering algorithm (LMS adaptive filter) is used to gradually adjust the filter coefficients to separate the reflected path signal from the main path signal.

[0161] 3. Reflection path signal feature extraction

[0162] Perform feature analysis on the separated reflection path signals to extract the amplitude, phase, and delay of the reflection path signals at each frequency point. Calculate the interference strength of the reflection path signals based on the signal strength (amplitude) and phase of different reflection paths.

[0163] 4. Phase cancellation mechanism design

[0164] A phase cancellation algorithm adjusts the received signal so that the phase of the reflected path signal cancels the phase of the main path signal, reducing interference from the reflected path signal. Dynamic adjustment of the phase canceller parameters ensures real-time cancellation of reflected path signal interference that varies with the environment.

[0165] 5.Signal output

[0166] The signal after phase cancellation will eliminate the reflection interference and obtain a clear main path signal.

[0167] The final output signal is a pure signal after interference suppression, which is transmitted to the downstream processor or communication module.

[0168] The foregoing description is merely a preferred embodiment of the present invention. It should be understood that the present invention is not limited to the form disclosed herein and should not be construed as excluding other embodiments. Rather, the present invention can be used in various other combinations, modifications, and environments and can be modified within the scope of the concept described herein through the above teachings or techniques or knowledge in the relevant field. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention are intended to be protected by the appended claims.

Claims

1. A VHF band adaptive filtering response method, characterized in that: The following steps are involved: S1 receives a mixed signal in the VHF band, the mixed signal including a main path signal and a reflected path signal at multiple frequency points; performs time domain and frequency domain analysis on the received mixed signal, and obtains frequency and phase information using Fourier transform; S2. Detect the time delay and phase difference between the main path signal and the reflected path signal using a delay detection algorithm; use an adaptive filtering algorithm to gradually adjust the filter coefficients to separate the reflected path signal from the main path signal; perform feature analysis on the extracted reflected path signals to extract the amplitude, phase, and delay of each reflected path signal; S3. By adjusting the phase cancellation mechanism, the phase of the reflected path signal is canceled with the phase of the main path signal to generate a cancellation signal; Wherein, the step S3 specifically includes the following sub-steps: S301. According to the extracted phase and delay characteristics of the reflected path signal, the phase of the reflected path signal is adjusted so that the phase difference between the phase of the reflected path signal and the main path signal at each frequency point is π, and the phase cancellation angle is obtained; S302. According to the phase cancellation angle, a signal for canceling the reflected path signal is constructed, wherein the amplitude of the generated cancellation signal is the same as the amplitude of the original reflected path signal; S303. The generated phase cancellation signal is superimposed on the received signal to eliminate reflection interference.

2. The adaptive filtering response method for VHF frequency band according to claim 1, wherein: The step S2 specifically includes the following sub-steps: S201. Identify the delay characteristics of each reflection path based on the phase change of the reflected path signal delay in the frequency domain; S202. According to the fixed phase offset of the reflected path signal, the phase difference at different frequencies is identified and the phase offset feature is extracted; S203. Based on the delay characteristics and phase offset characteristics, separate the signal of each reflected path through frequency domain filtering technology, and identify the amplitude characteristics of the reflected path by calculating the attenuation of the reflected path signal relative to the main path signal; S204. Combining the time delay characteristics, phase shift characteristics, and amplitude attenuation characteristics, a signal feature set of the reflection path signal is formed.

3. The adaptive filtering response method for VHF band according to claim 1, wherein: In step S301, the phase of the reflected path signal is adjusted so that the phase difference between the reflected path signal and the main path signal at each frequency point is π, and the phase cancellation angle is specifically expressed as: i cancel,i =π-θ i ; further Expand to get: i cancel,i =π-(φ total,i (f i )+2πf k t i ); Among them, the θ cancel,i The phase angle of the cancellation signal, θ i represents the original phase of the reflected path signal at the i-th frequency point, the φ total，i represents the total phase of the reflected path signal at the i-th frequency point, the f i represents the frequency point i, the τ i Represents the time delay of the reflected path signal at the i-th frequency point.

4. The adaptive filtering response method for VHF band according to claim 1, wherein: In step S302, the specific process of constructing a signal for canceling the reflected path signal is as follows: The amplitude of the cancellation signal is the same as the original reflected path signal: Substituting the phase cancellation angle: S cancel，i (f)=A ref，i cos(2πft+π-θ i ); Among them, the S cancel，i (f) represents the expression of the cancellation signal of the reflected path signal at the i-th frequency point in the frequency domain, where f represents the frequency, and A ref，i represents the amplitude of the reflected path signal at the i-th frequency point, represents the complex cancellation signal used to cancel the reflected path signal at the i-th frequency point, j is an imaginary unit, e is a natural constant, and the θ cancel，i represents the phase angle of the cancellation signal, the f i represents the frequency point i, the δ(·) represents the Dirac impulse function, the t represents the instantaneous state of the signal, and the θ i Represents the original phase of the reflected path signal at the i-th frequency point.

5. The adaptive filtering response method for VHF band according to claim 1, wherein: In step S303, the generated phase cancellation signal is superimposed on the received signal as follows: Perform a second Fourier transform on the obtained cancellation signal to convert the frequency domain into the time domain: S cancel，i (t)=A ref,i cos(2πft+θ cancel，i ) During the superposition process, the main path signal is combined with the cancellation signal to eliminate interference. After phase cancellation, the newly generated signal contains only the main path signal: Among them, the S cancel，i (t) represents the expression of the cancellation signal of the reflected path signal at the i-th frequency point in the time domain, and the A ref,i represents the amplitude of the reflected path signal at the i-th frequency point, the θ cancel，i represents the phase angle of the cancellation signal, f represents the frequency, t represents the instantaneous state of the signal, and Y new (t) represents the expression of the new signal after superposition in the time domain, and the S main (t) represents the expression of the main path signal in the time domain, and the S ref，i (t) represents the expression of the reflection path signal at the i-th frequency point in the time domain, N represents the number of reflection paths, and i represents the index.

6. A VHF band adaptive filtering response system, the system being implemented based on a VHF band adaptive filtering response method according to any one of claims 1 to 5, characterized in that: include: A signal preprocessing module is used to receive a mixed signal in the VHF band, wherein the mixed signal includes a main path signal and reflected path signals at multiple frequency points; Perform time domain and frequency domain analysis on the received mixed signal and obtain frequency and phase information using Fourier transform; The signal separation module is used to detect the time delay and phase difference between the main path signal and the reflected path signal using a delay detection algorithm; use an adaptive filtering algorithm to gradually adjust the filter coefficients to separate the reflected path signal from the main path signal; perform feature analysis on the extracted reflected path signals to extract the amplitude, phase, and delay of each reflected path signal; A signal cancellation module is used to cancel the phase of the reflected path signal with the phase of the main path signal by adjusting the phase cancellation mechanism to generate a cancellation signal; The signal cancellation module specifically includes: The phase cancellation angle calculation unit adjusts the phase of the reflected path signal based on the extracted phase and delay characteristics of the reflected path signal so that the phase difference between the reflected path signal and the main path signal at each frequency point is π, thereby obtaining the phase cancellation angle; a cancellation signal generating unit, configured to construct a signal for canceling the reflected path signal according to the phase cancellation angle, wherein the amplitude of the generated cancellation signal is the same as the amplitude of the original reflected path signal; The signal superposition unit is used to generate a phase cancellation signal and superimpose it on the received signal to eliminate reflection interference.

7. The adaptive filtering response system for VHF band according to claim 6, characterized in that: The signal separation module specifically includes: The delay feature extraction module is used to identify the delay feature of each reflection path based on the phase change of the reflection path signal delay in the frequency domain; A phase offset feature extraction module is used to identify phase differences at different frequencies and extract phase offset features based on the fixed phase offset of the reflected path signal. The amplitude feature extraction module is used to separate the signal of each reflection path through frequency domain filtering technology based on the time delay characteristics and phase offset characteristics, and to identify the amplitude characteristics of the reflection path by calculating the attenuation of the amplitude of the reflection path signal relative to the main path signal; The feature integration module is used to integrate the time delay feature, phase shift feature and amplitude attenuation feature to form a signal feature set of the reflection path signal.

8. The adaptive filtering response system for VHF band according to claim 6, characterized in that: In the phase cancellation angle calculation unit, the phase of the reflected path signal is adjusted so that the phase difference between the reflected path signal and the main path signal at each frequency point is π. The obtained phase cancellation angle is specifically expressed as: i cancel，i =π-θ i ; further Expand to get: i cancel，i =π-(φ total，i (f i )+2πf k t i ); Among them, the θ cancel，i The phase angle of the cancellation signal, θ i represents the original phase of the reflected path signal at the i-th frequency point, the φ total，i represents the total phase of the reflected path signal at the i-th frequency point, the f i represents the frequency point i, the τ i Represents the time delay of the reflected path signal at the i-th frequency point.

9. The adaptive filtering response system for VHF band according to claim 6, characterized in that: In the cancellation signal generating unit, the specific process of constructing a signal for canceling the reflected path signal is as follows: The amplitude of the cancellation signal is the same as the original reflected path signal: Substituting the phase cancellation angle: S cancel，i (f)=A ref，i cos(2πft+π-θ i ); Among them, the S cancel，i (f) represents the expression of the cancellation signal of the reflected path signal at the i-th frequency point in the frequency domain, where f represents the frequency, and A ref，i represents the amplitude of the reflected path signal at the i-th frequency point, represents the complex cancellation signal used to cancel the reflected path signal at the i-th frequency point, j is an imaginary unit, e is a natural constant, and the θ cancel，i represents the phase angle of the cancellation signal, the f i represents the frequency point i, the δ(·) represents the Dirac impulse function, the t represents the instantaneous state of the signal, and the θ i Represents the original phase of the reflected path signal at the i-th frequency point.

10. The VHF band adaptive filtering response system according to claim 6, characterized in that: In the signal superposition unit, the generated phase cancellation signal is superimposed on the received signal as follows: Perform a second Fourier transform on the obtained cancellation signal to convert the frequency domain into the time domain: S cancel，i (t)=A ref,i cos(2πft+θ cancel，i ) During the superposition process, the main path signal is combined with the cancellation signal to eliminate interference. After phase cancellation, the newly generated signal contains only the main path signal: Among them, the S cancel，i (t) represents the expression of the cancellation signal of the reflected path signal at the i-th frequency point in the time domain, and the A ref,i represents the amplitude of the reflected path signal at the i-th frequency point, the θ cancel，i represents the phase angle of the cancellation signal, f represents the frequency, t represents the instantaneous state of the signal, and Y new (t) represents the expression of the new signal after superposition in the time domain, and the S main (t) represents the expression of the main path signal in the time domain, and the S ref,i (t) represents the expression of the reflection path signal at the i-th frequency point in the time domain, N represents the number of reflection paths, and i represents the index.

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