A distributed co-frequency interference suppression method and system for regional symbiosis

Abstract

This invention discloses a method and system for suppressing distributed co-channel interference in a region-coexisting environment. The method includes: a desired signal node generating a desired signal and transmitting it through an antenna; distributed interference nodes generating interference signals and transmitting them through antennas; authorized receiving nodes receiving and processing the signals to obtain the down-converted received signal; converting the received distributed interference signal into real and imaginary parts, expanding it with respect to time error and residual frequency offset to obtain the interference signal expression after expansion with time error and residual frequency offset; merging the time-invariant coefficients before the real and imaginary parts of the interference signal into one term to obtain the reconstruction coefficient expression of the distributed interference; estimating the coefficients of the distributed interference suppression system model; reconstructing the interference signal; performing distributed interference suppression; and obtaining the desired signal. This invention achieves the reconstruction and suppression of distributed interference signals under constraints of time error, frequency offset, and IQ imbalance.

Description

Technical Field

[0001] This invention relates to methods for suppressing co-channel interference, and in particular to a distributed method and system for suppressing co-channel interference oriented towards regional symbiosis. Background Technology

[0002] In electromagnetic warfare scenarios, our equipment emits jamming signals to suppress enemy electromagnetic equipment, thereby restricting their right to use the electromagnetic spectrum. Distributed jamming can be implemented using small platforms such as drones, and its high flexibility and survivability are more in line with the needs of modern electronic warfare compared to shared-platform jamming.

[0003] The key to achieving coexistence between our equipment and the distributed interference area lies in the correct implementation of distributed co-channel interference suppression. Our authorized receiver reconstructs the distributed interference signal using pre-stored prior information to suppress interference and eliminate its impact, thus achieving regional coexistence. However, distributed interference devices have motion characteristics, which may introduce the Doppler effect and cause dynamic changes in propagation delay, making accurate time and frequency synchronization difficult. Furthermore, the use of direct conversion transceivers in up-conversion and down-conversion introduces IQ imbalance problems. All of these non-ideal factors may degrade interference suppression performance. Existing co-platform interference suppression methods are insufficient to overcome the problems in distributed interference scenarios; therefore, it is necessary to research interference suppression technologies for distributed multi-node scenarios. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a distributed co-frequency interference suppression method and system for regional symbiosis. It realizes the reconstruction and suppression of distributed interference signals under the constraints of time error, frequency offset and IQ imbalance, and effectively solves the problem of interference suppression performance degradation in distributed interference scenarios.

[0005] The objective of this invention is achieved through the following technical solution: a distributed co-channel interference suppression method for regional symbiosis, comprising the following steps:

[0006] S1. The desired signal node generates the desired signal and transmits it through the antenna;

[0007] S2. Distributed interference nodes generate interference signals and transmit them through antennas;

[0008] S3. The authorized receiving node receives and processes the signal to obtain the down-converted received signal;

[0009] S4. Convert the received distributed interference signal into real and imaginary parts;

[0010] S5. The time error is expanded using a 2P+1 order interpolation filter, thereby converting the time error into time-invariant coefficients, and the expression of the interference signal after time delay error expansion.

[0011] S6. Expand the residual frequency offset using an M-order Taylor series, and convert the residual frequency from exponential form to polynomial form to obtain the expression of the interference signal after expansion of time error and residual frequency offset.

[0012] S7. Combine the time-invariant coefficients before the real and imaginary components of the interference signal into one term to obtain the reconstruction coefficient expression for distributed interference;

[0013] S8. Estimate the coefficients of the distributed interference suppression system model at the authorized receiving node, reconstruct the interference signal for distributed interference suppression, and obtain the desired signal.

[0014] A distributed co-channel interference suppression system for regional symbiosis includes:

[0015] Desired signal node, used to generate the desired signal and transmit it through an antenna;

[0016] Distributed jamming nodes are used to generate jamming signals and transmit them through antennas;

[0017] The authorized receiving node is used to receive and process signals to obtain the down-converted received signal. The received distributed interference signal is converted into real and imaginary parts, and the time error and residual frequency offset are expanded to obtain the interference signal expression after time error and residual frequency offset expansion. The time-invariant coefficients before the real and imaginary parts of the interference signal are combined into one term to obtain the reconstruction coefficient expression of the distributed interference. The coefficients of the distributed interference suppression system model are estimated, and the interference signal is reconstructed for distributed interference suppression to obtain the desired signal.

[0018] The beneficial effects of this invention are: this invention realizes the reconstruction and suppression of distributed interference signals under the constraints of time error, frequency offset and IQ imbalance, and effectively solves the problem of interference suppression performance degradation in distributed interference scenarios. Attached Figure Description

[0019] Figure 1 This is a flowchart of the method of the present invention;

[0020] Figure 2 This is a schematic diagram of a distributed interference suppression system for overcoming region-oriented symbiosis in the embodiment;

[0021] Figure 3 This is a schematic diagram illustrating the relationship between distributed interference suppression performance and error magnitude in the embodiment;

[0022] Figure 4 This is a schematic diagram illustrating the relationship between distributed interference suppression performance and model expansion order in the embodiment; Detailed Implementation

[0023] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings, but the scope of protection of the present invention is not limited to the following description.

[0024] like Figure 1 As shown, a distributed co-channel interference suppression method for regional symbiosis includes the following steps:

[0025] S1: The desired signal node generates the desired signal and transmits it through an antenna. Let the baseband desired signal be s(n), which is then converted to s(t) by a DAC. Since the desired signal node and the interfering node are deployed separately, for ease of analysis, the IQ imbalance of the desired signal node is ignored, and the desired signal after up-conversion is denoted as x. s (t), whose expression is:

[0026]

[0027] Among them, s i (t) and s q f(t) represents the real and imaginary parts of s(t), respectively. s For carrier frequency.

[0028] S2: Distributed interference nodes generate interference signals and transmit them through antennas. A total of L interference nodes are set up, all transmitting the same interference signal. Let the baseband interference be c(n), which is converted to c(t) by a DAC. Considering the IQ imbalance at the distributed interference nodes, i.e., the amplitude and phase of the I-path and Q-path carriers used for up-conversion are not completely suppressed, taking the I-path as the reference, and assuming that phase and amplitude errors exist in the Q-path, the up-converted carrier signal generated by the local oscillator can be denoted as:

[0029] u l (t)=cos(2πf l t)+jα Tl sin(2πf l t+θ Tl (2)

[0030] Among them, f l Let α be the carrier frequency corresponding to the l-th interfering node. Tj With θ Tj Let I and Q represent the amplitude imbalance and phase imbalance at the oscillator of the l-th distributed interference node, respectively. When there is no IQ imbalance, we have α. Tl =1,θ Tl =0°.

[0031] The interference signal x after up-conversion l (t)(l=1,2,...,L) can be written as:

[0032]

[0033] S3. The authorized receiving node receives the signal, converts the received analog signal into a digital signal using an ADC, and synchronizes it with the reference interference sequence c(n) stored at the authorized receiving node. The resulting signal is represented as follows:

[0034]

[0035] Where, ε s With ε l Let τ be the channel fading coefficient corresponding to the desired signal and the l-th interference signal. s With τ l These represent the normalized time delays that still exist after time synchronization of the desired signal and the distributed interference signal, respectively. w′(n) is the AWGN signal, which is independent of the desired signal and the interference signal.

[0036] Considering that IQ imbalance also exists at the authorized receiving node, the received signal is down-converted, and the oscillation frequency of the down-conversion is recorded as f. d The resulting down-conversion carrier signal is:

[0037] v(t) = cos(2πf) d t)-jα R sin(2πf d t+θ R (5)

[0038] The received signal after down-conversion is as follows:

[0039] r(n) = r c (n)+r s (n)+w(n) (6)r c (n) represents the interference signal obtained from the down-conversion process, expressed as:

[0040]

[0041] Where, ΔF l =(f r -f l T is the normalized residual frequency offset, T is the sampling period, and ξ is the sampling period. 1l With ξ 2l The composite channel coefficients corresponding to the original component and the image component of the interference signal are expressed as follows:

[0042]

[0043] in, α R With θ R These represent the amplitude imbalance and phase imbalance of the oscillator at the authorized receiving node, respectively.

[0044] S4. Convert the received distributed interference signal into real and imaginary forms. Observing the expression of the interference signal after down-conversion, it can be seen that the received distributed interference signal r c (t) is composed of the interference sequence c(n) and its conjugate term c * (n) constitutes the structure, since c(n) and c * (n) Since there is correlation, assuming that the imaginary and real parts of the interference signal are independently and identically distributed, the interference signal in the received signal expression is transformed into an expression with real and imaginary parts, i.e.:

[0045]

[0046] Among them, c i (n) represents the real part of the interference sequence, c q (n) represents the imaginary part of the interference sequence.

[0047] S5. The normalized time delay error τ that still exists after time synchronization of the distributed interference signal and the reference interference sequence c(n) using a 2P+1 order interpolation filter. l This is expanded to convert the time error into time-invariant coefficients, i.e.:

[0048]

[0049] The interpolation filter coefficients are:

[0050]

[0051] Therefore, the expression for the interference signal after time delay error expansion is:

[0052]

[0053] S6. Normalize the residual frequency offset ΔF l By expanding using an M-order Taylor series, the residual frequency is transformed from exponential to polynomial form, i.e.:

[0054]

[0055]

[0056] Therefore, after expanding the time error and residual frequency offset, the expression for the interference signal is:

[0057]

[0058] S7. Combine the time-invariant coefficients before the real and imaginary components of the interference signal into a single term to obtain the reconstruction coefficient expression for distributed interference, i.e.:

[0059] In step S7, the reconstruction expression for distributed interference is:

[0060]

[0061] The expression for the time-invariant coefficients is as follows:

[0062]

[0063] S8. Estimate the coefficients of the distributed interference suppression system model at the authorized receiving node. Two sets of multi-tap filters are set at the authorized receiving node, with the inputs being the real and imaginary parts of the processed distributed interference signal, respectively. The output signals of the multi-tap filters are added together to obtain the reconstructed distributed interference signal. The tap coefficients are then calculated.

[0064] Tap coefficients can be represented as a [2(M+1)×(2P+1)]×1 dimensional vector, i.e.:

[0065] z(n) = [a0,...,a m ,...,a M ,b0,...,b m ,...,b M ] T (20)

[0066] a m =[a m,-P ,...,a m,0 ,...,a m,P ] T (twenty one)

[0067] b m =[b m,-P ,...,b m,0 ,...,b m,P ] (twenty two)

[0068] The reconstructed signal is obtained by multiplying the input reference interference signal vector by the coefficient vector. The expression for the reconstructed signal is:

[0069]

[0070] The input reference interference signal vector is:

[0071] Y(n)=[y i0 (n),...,y im (n),...,y iM (n),y q0 (n),...,y qm (n),...,y qM (n)] T (twenty four)

[0072] The vector corresponding to the real component is:

[0073] y im (n)=[n m c i (n+P),...,n m c i (n),...,n m c i (nP)] (25)

[0074] The vector corresponding to the imaginary component is:

[0075] y qm (n)=[jn m c q (n+P),...,jn m c q (n),...,jn m c q (nP)] (26)

[0076] According to the Minimize Mean Square Error (MMSE) criterion, the objective function to be minimized is:

[0077] J(z)=E[|e(n)|]=E[|r(n-z] T (n)Y(n)|] (27)

[0078] The coefficients are solved using the Least Mean Square (LMS) algorithm, and the algorithm flow is shown below.

[0079]

[0080] The authorized receiving node reconstructs the interference signal for distributed interference suppression and obtains the desired signal: the real part c of the reference interference sequence c(n) pre-stored by the authorized receiving node is... i (n) and the imaginary part c q (n) Input multi-tap filter for interference reconstruction:

[0081]

[0082] The reconstructed interference signal is subtracted from the received signal r(n) to recover the desired signal, i.e.:

[0083]

[0084] like Figure 2 As shown, a distributed co-channel interference suppression system for regional symbiosis includes:

[0085] Desired signal node, used to generate the desired signal and transmit it through an antenna;

[0086] Distributed jamming nodes are used to generate jamming signals and transmit them through antennas;

[0087] The authorized receiving node is used to receive and process signals to obtain the down-converted received signal. The received distributed interference signal is converted into real and imaginary parts, and the time error and residual frequency offset are expanded to obtain the interference signal expression after time error and residual frequency offset expansion. The time-invariant coefficients before the real and imaginary parts of the interference signal are combined into one term to obtain the reconstruction coefficient expression of the distributed interference. The coefficients of the distributed interference suppression system model are estimated, and the interference signal is reconstructed for distributed interference suppression to obtain the desired signal.

[0088] The proposed distributed co-channel interference suppression system and method for regional symbiosis are analyzed and evaluated through simulation. Specific parameter settings are shown in the table below.

[0089] Table 1 Simulation parameter settings for distributed co-channel interference suppression systems and methods for regional symbiosis

[0090]

[0091] Figure 3 This paper demonstrates the variation of the interference suppression ratio (JCR) with the interference-to-noise ratio (JNR) when the time-frequency error differs from the IQ imbalance. Three distributed interference nodes were set up, assuming that the IQ imbalance at the three interference nodes is the same as that at the licensed receiving node, and that the corresponding time-frequency error at the licensed receiving node is the same, with the time delay frequency offset error expansion order being P = M = 3. The figure plots the results of using the distributed interference suppression method proposed in this patent and the traditional co-platform interference suppression method when the error value is τ = 0.04 and ΔF = 10. -6 , α=1.005, θ=0.5°, τ=0.1, ΔF=10 -5 , α=1.01, θ=1°, τ=0.2, ΔF=10 -4 Simulation results are shown for α = 1.03 and θ = 3°. The curves demonstrate that when the time-frequency error and IQ imbalance are small, the proposed method can make the JCR close to the received JNR, and the distributed interference suppression performance approaches its theoretical limit. At JNR = 25dB, as the error increases, the proposed method improves the JCR by 4.31dB, 10.44dB, and 15.89dB compared to the common platform method, respectively. Furthermore, the improvement in interference suppression performance becomes more significant with increasing JNR, indicating that the proposed method can effectively reduce the impact of time-frequency error and IQ imbalance in distributed interference scenarios.

[0092] Figure 4 This demonstrates how the interference suppression ratio (JCR) varies with the interference noise ratio (JNR) for different time-frequency error expansion orders. The settings are τ = 0.2 and ΔF = 10. -4α = 1.02, θ = 3°. The curves in the figure represent the simulation results for expansion orders P = M = 1, 2, and 3, as well as the theoretical and simulation results of the common platform method. The curves show that when using the common platform method, the JCR stabilizes at 8.56 dB, indicating poor interference suppression performance, which may cause the licensed receiving node to fail to successfully recover the desired signal. When using the method of this patent, the JCR increases significantly with the increase of the expansion order, showing a significant improvement in distributed interference suppression performance compared to the common platform method. This indicates that the method of this patent can improve distributed interference suppression performance by increasing the expansion order.

[0093] The above description represents preferred embodiments of the present invention. It should be understood that the present invention is not limited to the forms disclosed herein and should not be construed as excluding other embodiments. It can be used in other combinations, modifications, and environments, and can be altered within the scope of the concept described herein through the above teachings or related technical or knowledge. Modifications and variations made by those skilled in the art that do not depart from the spirit and scope of the present invention should be within the protection scope of the appended claims.

Claims

1. A distributed co-channel interference suppression method for regional symbiosis, characterized in that: Includes the following steps: S1. The desired signal node generates the desired signal and transmits it through the antenna; S2. Distributed interference nodes generate interference signals and transmit them through antennas; S3. The authorized receiving node receives and processes the signal to obtain the down-converted received signal; S4. Convert the received distributed interference signal into real and imaginary parts; S5. The time error is expanded using a 2P+1 order interpolation filter, thereby converting the time error into time-invariant coefficients, and the expression of the interference signal after time delay error expansion. S6. Expand the residual frequency offset using an M-order Taylor series, and convert the residual frequency from exponential form to polynomial form to obtain the expression of the interference signal after expansion of time error and residual frequency offset. Step S6 includes: Normalized residual frequency offset ΔF l By expanding using an M-order Taylor series, the residual frequency is transformed from exponential to polynomial form, i.e.: Therefore, after expanding the time error and residual frequency offset, the expression for the interference signal is: Where L represents the total number of interfering nodes, ξ 1l With ξ 2l τ is the composite channel coefficient corresponding to the original component and the image component of the interference signal. l c represents the normalized time delay error that still exists after the received distributed interference signal is time-synchronized with the reference interference sequence. i (n) represents the real part of the interference sequence; S7. Combine the time-invariant coefficients before the real and imaginary components of the interference signal into one term to obtain the reconstruction coefficient expression for distributed interference; In step S7, the reconstruction expression for distributed interference is: The expression for the time-invariant coefficients is as follows: S8. Estimate the coefficients of the distributed interference suppression system model at the authorized receiving node, reconstruct the interference signal for distributed interference suppression, and obtain the desired signal.

2. The distributed co-channel interference suppression method for regional symbiosis according to claim 1, characterized in that: Step S1 includes: S101. Let the desired baseband signal be s(n), which is converted to s(t) by a DAC; since the desired signal node and the interference node are deployed separately, and the IQ imbalance of the desired signal node is not considered, let the desired signal after up-conversion be x. s (t), whose expression is: Among them, s i (t) and s q f(t) represents the real and imaginary parts of s(t), respectively. s For carrier frequency; S102. The desired signal node will upconvert the desired signal x. s (t) Transmitted via antenna.

3. The distributed co-channel interference suppression method for regional symbiosis according to claim 1, characterized in that: Step S2 includes: S201. Suppose there are L interference nodes that emit the same interference signal: Let the baseband interference be c(n), which is converted to c(t) by the DAC. Considering the IQ imbalance at the distributed interference nodes, i.e., the amplitude and phase of the I and Q carriers used in the upconversion are not completely suppressed, taking the I channel as the reference, and assuming that the phase and amplitude errors exist in the Q channel, the upconverted carrier signal generated by the local oscillator of the l-th interference node is denoted as: you l (t)=cos(2πf l t)+ja Tl sin(2πf l t+θ Tl ) (8) Among them, f l Let α be the carrier frequency corresponding to the l-th interfering node. Tl With θ Tl Let I and Q represent the amplitude imbalance and phase imbalance at the oscillator of the l-th distributed interference node, respectively. When there is no IQ imbalance, we have α. Tl =1,θ Tl =0°; The interference signal after frequency conversion at the l-th interference node is denoted as x. l (t), l=1,2,...,L: S202. Each interference node transmits the up-converted interference signal through an antenna.

4. The distributed co-channel interference suppression method for regional symbiosis as described in claim 3, characterized in that: Step S3 includes: S301. The authorized receiving node receives the signal, converts the received analog signal into a digital signal using an ADC, and synchronizes it with the reference interference sequence c(n) stored at the authorized receiving node. The resulting signal is represented as follows: Where, ε s With ε l Let τ be the channel fading coefficient corresponding to the desired signal and the l-th interference signal. l The normalized time delay error that still exists after the received distributed interference signal is synchronized with the reference interference sequence c(n) is represented by w′(n), which is an AWGN signal that is independent of the desired signal and the interference signal. S302. Considering that IQ imbalance also exists at the authorized receiving node, the received signal is down-converted, and the oscillation frequency of the down-conversion is recorded as f. d The resulting down-conversion carrier signal is: v(t)=cos(2πf d t)-ja R sin(2πf d t+θ R ) (11) The received signal after down-conversion is as follows: r c (n) represents the interference signal obtained from the down-conversion process, expressed as: Where, ΔF l =(f r -f l T is the normalized residual frequency offset, T is the sampling period, and ξ is the sampling period. 1l With ξ 2l The composite channel coefficients corresponding to the original component and the image component of the interference signal are expressed as follows: in, α R With θ R These represent the amplitude imbalance and phase imbalance of the oscillator at the authorized receiving node, respectively.

5. The distributed co-channel interference suppression method for regional symbiosis according to claim 1, characterized in that: Step S4 includes: Received distributed interference signal r c (t) is composed of the interference sequence c(n) and its conjugate term c * (n) constitutes the structure, since c(n) and c * (n) Since there is correlation, assuming that the imaginary and real parts of the interference signal are independently and identically distributed, the interference signal in the received signal expression is transformed into an expression with real and imaginary parts, i.e.: Among them, c i (n) represents the real part of the interference sequence, c q (n) represents the imaginary part of the interference sequence.

6. The distributed co-channel interference suppression method for regional symbiosis according to claim 1, characterized in that: Step S5 includes: The normalized time delay error τ that still exists after synchronizing the distributed interference signal with the reference interference sequence c(n) using a 2P+1 order interpolation filter. l This is expanded to convert the time error into time-invariant coefficients, i.e.: The interpolation filter coefficients are: Therefore, the expression for the interference signal after time delay error expansion is:

7. A distributed co-channel interference suppression method for regional symbiosis according to claim 1, characterized in that: Step S8 includes: S801. Two sets of multi-tap filters are set at the authorized receiving node. The inputs are the real and imaginary parts of the processed distributed interference signal, respectively. The output signals of the multi-tap filters are added together to obtain the reconstructed distributed interference signal. The tap coefficients are calculated below: The tap coefficients are represented as a [2(M+1)×(2P+1)]×1 dimensional vector, i.e.: z(n)=[a0,...,a m ,...,a M ,b0,...,b m ,...,b M ] T (20) a m =[a m,-P ,...,a m,0 ,...,a m,P ] (21) b m =[b m,-P ,...,b m,0 ,...,b m,P ] (22) The reconstructed signal is obtained by multiplying the input reference interference signal vector by the coefficient vector. The expression for the reconstructed signal is: The input reference interference signal vector is: Y(n)=[y i0 (n),...,and im (n),...,and iM (n), and q0 (n),...,and qm (n),...,and qM (n)] T (24) The vector corresponding to the real component is: The vector corresponding to the imaginary component is: According to the criterion of minimizing mean square error, the objective function to be minimized is: J(z)=E[|e(n)|]=E[|r(n)-z T (n)Y(n)|] (27) The coefficients are solved using the least mean square algorithm to obtain the estimated value of the coefficient vector z(n); S802. The authorized receiving node reconstructs the interference signal and performs distributed interference suppression to obtain the desired signal: the real part c of the reference interference sequence c(n) pre-stored by the authorized receiving node is... i (n) and the imaginary part c q (n) Input multi-tap filter for interference reconstruction: The reconstructed interference signal is subtracted from the received signal r(n) to recover the desired signal, i.e.:

8. A distributed co-channel interference suppression system for regional symbiosis, employing the method described in any one of claims 1 to 7, characterized in that: include: Desired signal node, used to generate the desired signal and transmit it through an antenna; Distributed jamming nodes are used to generate jamming signals and transmit them through antennas; Authorized receiving nodes are used to receive and process signals to obtain the down-converted received signal; The received distributed interference signal is converted into real and imaginary parts. The time error and residual frequency offset are expanded to obtain the interference signal expression after expansion. The time-varying coefficients before the real and imaginary parts of the interference signal are combined into one term to obtain the reconstruction coefficient expression of the distributed interference. The coefficients of the distributed interference suppression system model are estimated, and the interference signal is reconstructed for distributed interference suppression to obtain the desired signal.

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