Adaptive filtering response method and system of VHF (very high frequency) band

Abstract

The invention discloses an adaptive filtering response method and system of a VHF frequency band, relates to the field of VHF frequency band signal processing, effectively solves the problems of signal interference and multipath effect in VHF frequency band communication through the adaptive filtering response method, and combines a delay detection algorithm and an adaptive filtering algorithm through time domain and frequency domain analysis, so as to realize the adaptive filtering response of the VHF frequency band. Accurate separation of the reflection path signal and the main path signal is realized. Furthermore, interference of reflection path signals is eliminated through a phase offset mechanism, and the transmission quality of the signals is remarkably improved.

Description

Technical Field

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

[0002] The VHF 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 communications. In the VHF band, the signal has relatively good propagation characteristics, especially in line-of-sight propagation and ground reflection propagation, making it an ideal choice for aviation, navigation, television broadcasting, and military communications. With the rapid development of wireless communication technology, the application scenarios of the VHF band have continued to expand, including various communication methods such as automatic identification system (AIS), dedicated service (ASM), and VHF data exchange (VDE). However, the electromagnetic environment of the VHF band is complex, and the problem of mutual interference between devices has become increasingly prominent, especially in dense urban environments or areas with dense electronic equipment. In addition, due to the long signal wavelength of the VHF band, the impact of multipath effects and reflected path signals on communication quality is particularly obvious.

[0003] Although VHF band communication technology has been widely used in many fields, existing technologies still have shortcomings in dealing with signal interference, multipath effects and reflected path signals. Traditional filter design methods, such as Wiener filters, rely on prior knowledge of signal characteristics, which is often difficult to obtain in practical applications. In addition, there is a trade-off between convergence speed, time-varying system tracking speed and convergence accuracy in fixed-step adaptive filtering algorithms, and it is 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 facing VHF band communication technology. Summary of the invention

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

[0005] Among them, a VHF band adaptive filtering response method includes the following steps:

[0006] S1. Receive a mixed signal in the VHF band, the mixed signal including a main path signal and a reflected path signal at multiple frequency points; 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 by a delay detection algorithm; separate the reflected path signal from the main path signal by gradually adjusting the filter coefficient using an adaptive filtering algorithm; perform feature analysis on the extracted reflected path signal 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 cancelled 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, adjust the phase 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, and obtain the phase cancellation angle;

[0011] S302. According to the phase cancellation angle, construct a signal for canceling the reflected path signal, 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 according to the phase change of the reflection 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. Separate the signal of each reflected path by frequency domain filtering technology according to the delay characteristics and phase shift characteristics, and identify the amplitude characteristics of the reflected path by calculating the attenuation of the amplitude of the reflected path signal relative to the main path signal;

[0017] S204. Integrate the time delay characteristics, phase shift characteristics and amplitude attenuation characteristics to form a signal feature set of the reflection path signal.

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

[0019] θ cancel,i =π-θ i ;

[0020] Further expansion yields:

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

[0022] 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.

[0023] Furthermore, in step S302, the specific process of constructing a signal for canceling the reflected path signal is as follows:

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

[0025]

[0026] Substituting in the phase cancellation angle:

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

[0028] 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 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, and the θ i Represents the original phase of the reflected path signal at the i-th frequency point.

[0029] Furthermore, in step S303, the generated phase cancellation signal is superimposed on the received signal 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] In 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 VHF band adaptive filtering response methods, and includes:

[0036] A signal preprocessing module is used to receive a mixed signal in the VHF frequency 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 use Fourier transform to obtain frequency and phase information;

[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 by using a delay detection algorithm; to separate the reflected path signal from the main path signal by gradually adjusting the filter coefficient using an adaptive filtering algorithm; to perform feature analysis on the extracted reflected path signal to extract the amplitude, phase and delay of each reflected path signal;

[0038] A signal cancellation module, 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] Wherein, the signal cancellation module specifically includes:

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

[0041] A cancellation signal generating unit, used for constructing 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 with the received signal to eliminate reflection interference.

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

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

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

[0046] An amplitude feature extraction module is used to separate the signal of each reflection path through frequency domain filtering technology according to the time delay feature and the phase offset feature, and to identify the amplitude feature 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 at each frequency point and the main path signal is π, and the 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 represents the phase angle of the cancellation signal, the 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: according to the amplitude of the cancellation signal being the same as the original reflected path signal:

[0054]

[0055] Substituting in 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] In 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] The present invention effectively solves the signal interference and multipath effect problems in VHF band communication through an adaptive filtering response method, and realizes accurate separation of reflected path signals from main path signals through time domain and frequency domain analysis, combined with a delay detection algorithm and an adaptive filtering algorithm. Furthermore, through a phase cancellation mechanism, interference of reflected path signals is eliminated, significantly improving the transmission quality of signals. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0067] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described in detail in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention, that is, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can 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. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative work are within the scope of protection of the present invention. It should be noted that relational terms such as the terms "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations.

[0069] Moreover, the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a list of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or apparatus. In the absence of more restrictions, an element defined by the phrase "comprises a ..." does not exclude 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 in conjunction with 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. Receive a mixed signal in the VHF band, the mixed signal including a main path signal and a reflected path signal at multiple frequency points; perform time domain and frequency domain analysis on the received mixed signal, and use Fourier transform to obtain frequency and phase information;

[0073] S2. Detect the time delay and phase difference between the main path signal and the reflected path signal by a delay detection algorithm; separate the reflected path signal from the main path signal by gradually adjusting the filter coefficient using an adaptive filtering algorithm; perform feature analysis on the extracted reflected path signal 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 cancelled 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, adjust the phase 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, and obtain the phase cancellation angle;

[0077] S302. According to the phase cancellation angle, construct a signal for canceling the reflected path signal, 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 according to the phase change of the reflection path signal delay in the frequency domain;

[0081] Specifically, the 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] Among them, the Δφ i (f) is represented as the phase change of the reflected path signal at the i-th frequency point in the frequency domain, 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 , and solve for 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 the total phase of each reflection path, it 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. Separate the signal of each reflected path by frequency domain filtering technology according to the delay characteristics and phase shift characteristics, and identify the amplitude characteristics of the reflected path by calculating the attenuation of the amplitude 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. Combining the delay characteristics, phase shift characteristics and amplitude attenuation characteristics, 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 at each frequency point and the main path signal 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] According to the cancellation signal amplitude is the same as the original reflection path signal:

[0106]

[0107] Substituting in 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] In 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] Further, in the above embodiment, the specific process of performing time domain and frequency domain analysis on the received mixed signal mentioned in step S1 and using Fourier transform to obtain frequency and phase information is as follows:

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

[0118]

[0119] Here, (f) is the representation in the frequency domain; further, the Fourier transform here is specifically: Wherein, 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 VHF band adaptive filtering response methods, and includes:

[0129] A signal preprocessing module is used to receive a mixed signal in the VHF frequency 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 use Fourier transform to obtain frequency and phase information;

[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 by using a delay detection algorithm; to separate the reflected path signal from the main path signal by gradually adjusting the filter coefficient using an adaptive filtering algorithm; to perform feature analysis on the extracted reflected path signal to extract the amplitude, phase and delay of each reflected path signal;

[0131] A signal cancellation module, 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] Wherein, the signal cancellation module specifically includes:

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

[0134] A cancellation signal generating unit, used for constructing 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 with the received signal to eliminate reflection interference.

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

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

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

[0139] An amplitude feature extraction module is used to separate the signal of each reflection path through frequency domain filtering technology according to the time delay feature and the phase offset feature, and to identify the amplitude feature 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 at each frequency point and the main path signal is π, and the 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 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.

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

[0147]

[0148] Substituting in 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] In 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 that includes the ground reflection path signal and the main path signal, and collect the time domain and frequency domain characteristics of the signal, mainly including the amplitude, phase and delay information of the signal.

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

[0160] Perform time domain and frequency domain analysis on the received signal, and use Fourier transform (FFT) to obtain frequency and phase information. Detect the multipath delay characteristics of the signal. The main path signal generally reaches the receiving end in the shortest time, while the reflected path signal has a slight time delay, which is extracted by the delay detection algorithm. Use phase changes to detect signal differences between different paths. Use an adaptive filtering algorithm (LMS adaptive filter) to separate the reflected path signal from the main path signal by gradually adjusting the filter coefficients.

[0161] 3. Reflection path signal feature extraction

[0162] The separated reflection path signals are analyzed for characteristics, and the amplitude, phase and delay of the reflection path signals at each frequency point are extracted. The interference intensity of the reflection path signals is calculated based on the signal strength (amplitude) and phase of different reflection paths.

[0163] 4. Phase cancellation mechanism design

[0164] The received signal is adjusted through the phase cancellation algorithm so that the phase of the reflected path signal and the main path signal phase cancel each other, reducing the interference of the reflected path signal. The parameters of the phase canceller are dynamically adjusted to ensure real-time elimination of the reflected path signal interference that changes with the environment.

[0165] 5. Signal output

[0166] The signal after phase cancellation will eliminate 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 above is only 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 regarded as excluding other embodiments, but 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 the technology or knowledge of the relevant field. The changes and modifications made by those skilled in the art shall not deviate from the spirit and scope of the present invention, and shall be within the scope of protection of the claims attached to the present invention.

Claims

1. A VHF band adaptive filtering response method, characterized in that: The following steps are involved: S1. Receive a mixed signal in the VHF band, the mixed signal including a main path signal and a reflected path signal at multiple frequency points; perform time domain and frequency domain analysis on the received mixed signal, and use Fourier transform to obtain frequency and phase information; S2. Detect the time delay and phase difference between the main path signal and the reflected path signal by a delay detection algorithm; separate the reflected path signal from the main path signal by gradually adjusting the filter coefficient using an adaptive filtering algorithm; perform feature analysis on the extracted reflected path signal 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 cancelled 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, adjust the phase 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, and obtain the phase cancellation angle; S302. According to the phase cancellation angle, construct a signal for canceling the reflected path signal, 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 as claimed in claim 1, characterized in that: The step S2 specifically includes the following sub-steps: S201. Identify the delay characteristics of each reflection path according to the phase change of the reflection 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. Separate the signal of each reflected path by frequency domain filtering technology according to the delay characteristics and phase shift characteristics, and identify the amplitude characteristics of the reflected path by calculating the attenuation of the amplitude 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 frequency band as claimed in claim 1, characterized in that: In step S301, the phase of the reflected path signal is adjusted so that the phase difference between the reflected path signal at each frequency point and the main path signal 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 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.

4. The adaptive filtering response method for VHF frequency band as claimed in claim 1, characterized in that: In step S302, the specific process of constructing a signal for canceling the reflected path signal is as follows: According to the cancellation signal amplitude is the same as the original reflection path signal: Substituting in 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 frequency band as claimed in claim 1, characterized in that: 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 ) In 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 is 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, used for receiving a mixed signal in the VHF frequency 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 use Fourier transform to obtain frequency and phase information; The signal separation module is used to detect the time delay and phase difference between the main path signal and the reflected path signal by using a delay detection algorithm; to separate the reflected path signal from the main path signal by gradually adjusting the filter coefficient using an adaptive filtering algorithm; to perform feature analysis on the extracted reflected path signal to extract the amplitude, phase and delay of each reflected path signal; A signal cancellation module, 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; Wherein, the signal cancellation module specifically includes: The phase cancellation angle calculation unit adjusts the phase of the reflected path signal according to the extracted phase and delay characteristics of the reflected path signal, so that the phase difference between the reflected path signal at each frequency point and the main path signal is π, and obtains the phase cancellation angle; A cancellation signal generating unit, used for constructing 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 with the received signal to eliminate reflection interference.

7. A VHF band adaptive filtering response system as claimed in claim 6, characterized in that: The signal separation module specifically includes: A delay feature extraction module is used to identify the delay feature of each reflection path according to the phase change of the reflection path signal delay in the frequency domain; A phase shift feature extraction module is used to identify phase differences at different frequencies and extract phase shift features according to the fixed phase shift of the reflected path signal. An amplitude feature extraction module is used to separate the signal of each reflection path through frequency domain filtering technology according to the time delay feature and the phase offset feature, and to identify the amplitude feature 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. A VHF band adaptive filtering response system as claimed in 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 at each frequency point and the main path signal 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 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.

9. The adaptive filtering response system for VHF band as claimed in 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: According to the cancellation signal amplitude is the same as the original reflection path signal: Substituting in 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 filter 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 ) In 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.

Images