M-sequence-assisted digital domain self-interference cancellation system and method

Abstract

The invention discloses an M-sequence-assisted digital domain self-interference cancellation system and method, and belongs to the technical field of self-interference cancellation. According to the method, self-interference channel parameters are estimated by using the M sequence, so that suppression of self-interference cancellation on received radar target signals is avoided; according to the method, iterative operation is carried out on a received input signal and an M sequence to estimate time delay and fading values of a self-interference signal, and a reference signal carries out time synchronization and channel compensation on an estimated self-interference channel parameter value and then carries out self-interference offset to ensure that a target radar signal is not damaged. According to the method, self-interference cancellation can be rapidly completed, and radar target signals cannot be deteriorated; the number of iterations is reduced, and target radar signals are not offset; the self-interference channel can be detected in real time, and the compensation coefficient of the self-interference channel can be adjusted in time, so that the normal work of the system can be ensured.

Description

Technical Field

[0001] The present invention belongs to the technical field of self-interference cancellation, and in particular relates to an M-sequence-assisted digital domain self-interference cancellation system and method. Background Art

[0002] In modern electronic warfare, traditional deception jamming technology relies on a single modulation method and faces the disadvantage of being insufficient to interfere with radar identification and detection. Conventional radar jammers can be roughly divided into two parts: reconnaissance receiving link and interference generation module. The reconnaissance receiving link is mainly used to intercept enemy radar signals and measure and sort parameters to provide guidance information for the subsequent interference generation module. The interference generation module generates and transmits corresponding interference signals according to the intercepted radar pulse samples, preset interference parameters and guidance information provided by the reconnaissance receiving link to achieve interference with enemy radars. However, under the conditions of airborne and missile-borne platforms, due to the limitation of installation space, the distance between the receiving antenna and the transmitting antenna of the radar jammer is often close, resulting in the difficulty of transmitting and receiving isolation to meet the requirements. The transmitted interference signal enters the receiving antenna after spatial coupling to generate self-interference, causing the quality of the received signal to be seriously reduced, and even self-excitation is formed to make the system unable to work normally. Therefore, how to improve the ability to cancel the self-interference of transmission and reception is one of the key issues in the research of radar jammers.

[0003] At present, most radar jamming systems use interrupt sampling and forwarding jamming to store radar signals and generate false target radar signals. It is important to note that this process involves the time division of transmission and reception, which will result in some loss of stored radar signals, as well as a certain period without radar jamming signals. Therefore, in order to enhance the deception of false target radar signals generated by radar jamming, a simultaneous transmission and reception method must be adopted. However, simultaneous transmission and reception will introduce self-interference signals. If the self-interference power is greater than the receiver sensitivity, the self-interference signal is likely to be mistaken for the target radar and parameter measurement is performed. This may introduce incorrect parameters in the subsequent jamming generation and jamming decision-making process, ultimately leading to a decrease in the effectiveness of radar jamming.

[0004] For the traditional self-interference cancellation algorithms used in full-duplex radar jammers, such as (Recursive Least Square) RLS, (Least Mean Squares) LMS, and (Direct Least-Squares) DLS, the algorithms all use the reference signal as prior information to complete the self-interference cancellation in the received mixed signal. However, if the above algorithm is used in a scenario where the target radar signal and the self-interference signal are highly correlated, the received radar target signal will also be cancelled, which is not in line with expectations. If there is only a reference signal, it is easy to cancel both the radar target signal and the self-interference signal. Summary of the invention

[0005] The purpose of the present invention is to overcome the defects of the above-mentioned prior art and provide an M-sequence-assisted digital domain self-interference cancellation system and method, which first performs time estimation on the received mixed signal and the M sequence, then performs time synchronization on the reference signal, and then completes channel value estimation and compensation based on the time-synchronized signal and the M sequence, and then subtracts the reconstructed signal from the received mixed signal to reduce the self-interference power, thereby completing self-interference cancellation.

[0006] The technical problem proposed by the present invention is solved in this way:

[0007] An M-sequence-assisted digital domain self-interference cancellation system comprises a radio frequency receiving channel, an analog down-converter, an ADC, a time estimation and synchronization module, a channel estimation and compensation module, a subtractor, an adder, a DAC, an analog up-converter, a radio frequency transmitting channel and a local oscillator; the local oscillator is used to provide a local oscillator for the analog up-converter and the analog down-converter;

[0008] The RF receiving channel receives a mixed signal containing communication signals and self-interference signals from space. r (t), analog downconverter for mixed signal y r (t) performs down-conversion processing to generate an intermediate frequency receiving analog signal r(t); the ADC performs analog-to-digital conversion on the intermediate frequency receiving analog signal r(t) to obtain an intermediate frequency receiving digital signal r(n), where 1≤n≤N, and N represents the total number of sampling points of the intermediate frequency digital signal r(n);

[0009] The time estimation and synchronization module performs cross-correlation calculation on the M sequence p(n) and the residual signal h(n) to obtain a cross-correlation sequence. The cross-correlation value at the mth sampling point is expressed as The superscript * indicates taking the conjugate. Let the initial signal of the residual signal h(n) be the intermediate frequency received digital signal r(n). Determine the estimated delay parameter τ based on the index position of the maximum cross-correlation peak of the cross-correlation sequence. ref (n) performing time delay to obtain a time-synchronized signal;

[0010] The channel estimation and compensation module takes the maximum cross-correlation peak value and the M sequence as input, obtains the channel estimation value, and performs channel compensation to obtain the reconstructed self-interference signal;

[0011] The subtractor is used to subtract the intermediate frequency digital signal r(n) and the interference signal r s (n) performing subtraction to complete self-interference cancellation and update the residual signal;

[0012] The adder adds the residual signal and the M sequence p(n) to obtain an updated reference signal;

[0013] The DAC performs digital-to-analog conversion on the updated reference signal to generate an intermediate frequency transmission signal; the analog up-converter performs up-conversion on the intermediate frequency transmission signal to generate an RF transmission signal. s (t) is sent into space via a radio frequency transmission channel.

[0014] Furthermore, the maximum cross-correlation peak of the cross-correlation sequence is recorded as The index position of the maximum cross-correlation peak is Let the estimated delay parameter be For the reference signal j ref (n) delays and obtains the time-synchronized signal j t (n) = j ref (n-τ).

[0015] Furthermore, the channel estimation value The reconstructed self-interference signal r s (n) = aj t (n) = aj ref (n-τ).

[0016] The present invention also provides an M-sequence-assisted digital domain self-interference cancellation method, comprising the following steps:

[0017] S1, for the mixed signal y containing the communication signal and the self-interference signal r (t) performing down-conversion processing and analog-to-digital conversion processing to obtain an intermediate frequency received digital signal r(n), 1≤n≤N, and N represents the total number of sampling points of the intermediate frequency digital signal r(n);

[0018] Perform cross-correlation calculation on the M sequence p(n) and the intermediate frequency digital signal r(n) to obtain the cross-correlation sequence The superscript * indicates conjugation; the index position of the maximum cross-correlation peak of the cross-correlation sequence is Let the estimated delay parameter be For the reference signal j ref (n) delays and obtains the time-synchronized signal j t (n) = j ref (n-τ); Calculate the channel estimate Then channel compensation is performed to obtain the reconstructed self-interference signal r s (n) = aj t (n) = aj ref (n-τ); Update the residual signal h(n)=r(n)-r s (n);

[0019] S2. Perform cross-correlation calculation on the M sequence p(n) and the residual signal h(n) to obtain the cross-correlation sequence The index position of the maximum cross-correlation peak of the cross-correlation sequence is Let the estimated delay parameter be

[0020] S3, determine whether the maximum cross-correlation peak value exceeds the set threshold, if so, execute step S4; otherwise, execute step S5;

[0021] S4, for reference signal j ref (n) delays and obtains the time-synchronized signal j t (n) = j ref (n-τ); Calculate the channel estimate Then channel compensation is performed to obtain the reconstructed self-interference signal r s (n) = aj t (n) = aj ref (n-τ); Update the residual signal h(n)=r(n)-r s (n), execute S2;

[0022] S5. Update reference signal j ref (n) = h(n) + p(n);

[0023] S6. Perform digital-to-analog conversion and up-conversion processing on the updated reference signal to generate a radio frequency transmission signal j s (t)Send to space.

[0024] The beneficial effects of the present invention are:

[0025] The M-sequence-assisted self-interference cancellation method of the present invention uses the M-sequence to estimate the self-interference channel parameters, avoiding the suppression of the received radar target signal by the self-interference cancellation. The principle of the self-interference suppression of the method of the present invention involves iterative operation of the received input signal and the M-sequence in the FPGA to estimate the delay and fading value of the self-interference signal, and the reference signal performs time synchronization and channel compensation on the estimated self-interference channel parameter value before performing self-interference cancellation, so as to ensure that the target radar signal will not be damaged. The advantages are: 1) self-interference cancellation can be completed quickly, and the radar target signal will not be deteriorated, 2) this algorithm reduces a lot of iterations compared to the traditional self-interference cancellation algorithm, and will not cancel the target radar signal, 3) the self-interference channel can be detected in real time, and the compensation coefficient of the self-interference channel can be adjusted in time, thereby ensuring that the system can work normally. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 This is a block diagram of an implementation of the M-sequence assisted digital domain self-interference cancellation system of the present invention;

[0027] Figure 2 The figure is a flow chart of the M-sequence-assisted digital domain self-interference cancellation method of the present invention. DETAILED DESCRIPTION

[0028] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0029] This embodiment provides an M-sequence assisted digital domain self-interference cancellation system, and its implementation block diagram is as follows: Figure 1 As shown, it includes a radio frequency receiving channel, an analog down converter, an ADC, a time estimation and synchronization module, a channel estimation and compensation module, a subtractor, an adder, a DAC, an analog up converter, a radio frequency transmitting channel and a local oscillator;

[0030] The RF receiving channel receives a mixed signal containing communication signals and self-interference signals from space. r (t), t represents time, the analog down-converter is used to simulate the mixed signal y r (t) is down-converted to generate an intermediate frequency received analog signal r(t); the ADC performs analog-to-digital conversion on the intermediate frequency received analog signal r(t) to obtain an intermediate frequency received digital signal r(n), 1≤n≤≤N, and N represents the total number of sampling points of the intermediate frequency digital signal r(n).

[0031] The time estimation and synchronization module performs cross-correlation calculation on the M sequence p(n) and the residual signal h(n) to obtain a cross-correlation sequence. The cross-correlation value at the mth sampling point is expressed as The superscript * indicates taking the conjugate, and the initial signal of the residual signal h(n) is set to be the intermediate frequency received digital signal r(n); the maximum cross-correlation peak of the cross-correlation sequence is The index position of the maximum cross-correlation peak is Let the estimated delay parameter be For the reference signal j ref (n) delays and obtains the time-synchronized signal j t (n) = j ref (n-τ).

[0032] The channel estimation and compensation module takes the maximum cross-correlation peak sum and the M sequence as input and obtains the channel estimation value by Then channel compensation is performed to obtain the reconstructed self-interference signal r s (n) = aj t (n) = aj ref (n-τ).

[0033] The subtractor is used to subtract the intermediate frequency digital signal r(n) and the interference signal r s (n) performing subtraction to complete self-interference cancellation and update the residual signal;

[0034] The adder adds the residual signal and the M sequence p(n) to obtain an updated reference signal;

[0035] The DAC performs digital-to-analog conversion on the updated reference signal to generate an intermediate frequency transmission signal; the analog up-converter performs up-conversion on the intermediate frequency transmission signal to generate an RF transmission signal. s (t) is sent into space via a radio frequency transmission channel.

[0036] The local oscillator is used to provide the local oscillation for the analog up and down converters.

[0037] Based on the above system, this embodiment also provides an M-sequence assisted digital domain self-interference cancellation method, the flow chart of which is as follows: Figure 2 As shown, the following steps are included:

[0038] S1, for the mixed signal y containing the communication signal and the self-interference signal r (t) Perform down-conversion processing and analog-to-digital conversion processing to obtain an intermediate frequency received digital signal r(n), 1≤n≤N, and N represents the total number of sampling points of the intermediate frequency digital signal r(n).

[0039] Perform cross-correlation calculation on the M sequence p(n) and the intermediate frequency digital signal r(n) to obtain the cross-correlation sequence The superscript * indicates conjugation; the index position of the maximum cross-correlation peak of the cross-correlation sequence is Let the estimated delay parameter be For the reference signal j ref (n) delays and obtains the time-synchronized signal j t (n) = j ref (n-τ); Calculate the channel estimate Then channel compensation is performed to obtain the reconstructed self-interference signal r s (n) = aj t (n) = aj ref (n-τ); Update the residual signal h(n)=r(n)-r s (n);

[0040] S2. Perform cross-correlation calculation on the M sequence p(n) and the residual signal h(n) to obtain the cross-correlation sequence The index position of the maximum cross-correlation peak of the cross-correlation sequence is Let the estimated delay parameter be

[0041] S3, determine whether the maximum cross-correlation peak value exceeds the set threshold, if so, execute step S4; otherwise, execute step S5;

[0042] S4, for reference signal j ref (n) delays and obtains the time-synchronized signal j t (n) = j ref(n-τ); Calculate the channel estimate Then channel compensation is performed to obtain the reconstructed self-interference signal r s (n) = aj t (n) = qj ref (n-τ); Update the residual signal h(n)=r(n)-r s (n), execute S2;

[0043] S5. Update reference signal j ref (n) = h(n) + p(n);

[0044] S6. Perform digital-to-analog conversion and up-conversion processing on the updated reference signal to generate a radio frequency transmission signal j s (t)Send to space.

[0045] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can still modify the methods described in the above implementation regulations, such as changing the names of the methods, etc. Any modification, equivalent substitution, improvement, etc. made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. An M-sequence-assisted digital domain self-interference cancellation system, characterized in that: It includes a radio frequency receiving channel, an analog down converter, an ADC, a time estimation and synchronization module, a channel estimation and compensation module, a subtractor, an adder, a DAC, an analog up converter, a radio frequency transmitting channel and a local oscillator; the local oscillator is used to provide a local oscillator for the analog up converter and the analog down converter; The RF receiving channel receives a mixed signal containing communication signals and self-interference signals from space. r (t), analog downconverter for mixed signal y r (t) performs down-conversion processing to generate an intermediate frequency receiving analog signal r(t); the ADC performs analog-to-digital conversion on the intermediate frequency receiving analog signal r(t) to obtain an intermediate frequency receiving digital signal r(nn), 1≤n≤N, and N represents the total number of sampling points of the intermediate frequency digital signal r(n); The time estimation and synchronization module performs cross-correlation calculation on the M sequence p(n) and the residual signal h(n) to obtain a cross-correlation sequence. The cross-correlation value at the mth sampling point is expressed as The superscript * indicates taking the conjugate. Let the initial signal of the residual signal h(n) be the intermediate frequency received digital signal r(n). Determine the estimated delay parameter τ based on the index position of the maximum cross-correlation peak of the cross-correlation sequence. ref (n) performing time delay to obtain a time-synchronized signal; The channel estimation and compensation module takes the maximum cross-correlation peak value and the M sequence as input, obtains the channel estimation value, and performs channel compensation to obtain the reconstructed self-interference signal; The subtractor is used to subtract the intermediate frequency digital signal r(n) and the interference signal r s (n) performing subtraction to complete self-interference cancellation and update the residual signal; The adder adds the residual signal and the M sequence p(n) to obtain an updated reference signal; The DAC performs digital-to-analog conversion on the updated reference signal to generate an intermediate frequency transmission signal; The analog up-converter up-converts the intermediate frequency transmission signal to generate the RF transmission signal j s (i) is sent into space via a radio frequency transmission channel.

2. The M-sequence-assisted digital domain self-interference cancellation system according to claim 1, characterized in that: The maximum cross-correlation peak value of the cross-correlation sequence is The index position of the maximum cross-correlation peak is Let the estimated delay parameter be For the reference signal j ref (n) delays and obtains the time-synchronized signal j t (n) = j ref (n-τ).

3. The M-sequence-assisted digital domain self-interference cancellation system according to claim 1, characterized in that: Channel estimation The reconstructed self-interference signal r s (n) = aj t (n) = aj ref (n-τ).

4. An M-sequence-assisted digital domain self-interference cancellation method, characterized in that: The following steps are involved: S1, for the mixed signal y containing the communication signal and the self-interference signal r (t) performing down-conversion processing and analog-to-digital conversion processing to obtain an intermediate frequency received digital signal r(n), 1≤n≤N, and N represents the total number of sampling points of the intermediate frequency digital signal r(n); Perform cross-correlation calculation on the M sequence p(n) and the intermediate frequency digital signal r(n) to obtain the cross-correlation sequence The superscript * indicates conjugation; the index position of the maximum cross-correlation peak of the cross-correlation sequence is Let the estimated delay parameter be For the reference signal j ref (n) delays and obtains the time-synchronized signal j t (n) = j ref (n-τ); Calculate the channel estimate Then channel compensation is performed to obtain the reconstructed self-interference signal r s (n) = aj t (n) = aj ref (n-τ); Update the residual signal h(n)=r(n)-r s (n); S2. Perform cross-correlation calculation on the M sequence p(n) and the residual signal h(n) to obtain the cross-correlation sequence The index position of the maximum cross-correlation peak of the cross-correlation sequence is Let the estimated delay parameter be S3, determine whether the maximum cross-correlation peak value exceeds the set threshold, if so, execute step S4; Otherwise, execute step S5; S4, for reference signal j ref (n) delays and obtains the time-synchronized signal j t (n) = j ref (n-τ); Calculate the channel estimate Then channel compensation is performed to obtain the reconstructed self-interference signal r s (n) = aj t (n) = aj ref (n-τ); Update the residual signal h(n)=r(n)-r s (n), execute S2; S5. Update reference signal j ref (n) = h(n) + p(n); S6. Perform digital-to-analog conversion and up-conversion processing on the updated reference signal to generate a radio frequency transmission signal j s (t)Send to space.

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