Optical and digital domain combined multi-channel self-interference cancellation apparatus and method

Abstract

The application discloses a multi-channel self-interference cancellation device combined with an optical domain and a digital domain, which comprises a signal branch module a, a reference branch module b and a signal post-processing module c. The signal branch module a comprises n signal processing channels with the same structure, a wavelength division multiplexer (3), a dispersion medium (4), a wavelength division demultiplexer (5) and a multi-wavelength light source (8); each signal processing channel comprises a low-noise amplifier (1), a double-parallel Mach-Zehnder modulator (2), an optical power amplifier (6) and an optical-electricity detector (7) which are all the same. The reference branch module b comprises a low-noise amplifier (1), a double-parallel Mach-Zehnder modulator (2), a tunable laser (12), an optical splitter (9) and a multi-channel analog matching detection branch. The signal post-processing module c comprises an electric coupler (13), an analog-digital converter (14) and a digital signal processing (15). The application also discloses a multi-channel self-interference cancellation method combined with an optical domain and a digital domain. The application realizes self-interference cancellation of an array multi-channel in-band full-duplex system and beam forming of multi-channel useful signals with small array element scale and low operation cost.

Description

Technical Field

[0001] This invention relates to the field of microwave photonic signal processing, specifically to a radio frequency self-interference cancellation device and method that combines optical analog domain and electrical digital domain processing, for use in-band full-duplex radio frequency systems under a multi-channel array antenna architecture, to achieve self-interference signal cancellation generated by multi-channel crosstalk. Background Technology

[0002] In recent years, to effectively utilize limited spectrum resources to support high-capacity, high-speed data transmission and achieve integrated development of multifunctional electronic systems, adopting a full-duplex system within the same frequency band has become the most promising solution, namely, in-band full-duplex. Simultaneously, employing a shared antenna system for both transmit and receive, where one antenna performs multiple functions, can improve RF integrated configuration management and the electromagnetic compatibility of airborne antennas, eliminating the adverse effects of an excessive number of antennas. However, in in-band full-duplex systems, especially in multi-channel array antenna systems, the received signal is affected by its own antenna reflection and crosstalk from adjacent antennas. Therefore, self-interference cancellation technology is one of the key technologies for promoting the high spectrum utilization advantage of in-band full-duplex systems.

[0003] Currently, electrical analog domain self-interference cancellation methods are limited by the operating bandwidth and amplitude / phase modulation accuracy of radio frequency devices, making it difficult to achieve sufficiently high interference suppression within a large bandwidth. Furthermore, when facing the demands of multi-channel arrays, the types and number of electronic devices increase, resulting in complex system structures and susceptibility to electromagnetic interference, thus hindering miniaturization, integrated construction, and engineering practicality. Compared to traditional electrical self-interference cancellation, photonic radio frequency self-interference cancellation technology can fully leverage the advantages of optical domain microwave signal processing, such as large bandwidth, high-precision delay, and amplitude modulation. Moreover, this technology can be combined with optical domain signal transmission, distribution, measurement, and processing, demonstrating significant performance advantages and application potential in fields such as communications and radar, making it a hot topic in recent years.

[0004] Most current optical self-interference cancellation schemes address single-path or multi-path self-interference cancellation scenarios at single-channel transceiver front-ends, neglecting multi-channel self-interference cancellation schemes compatible with array antenna architectures. In such multi-channel array architectures, separately canceling self-interference signals between each pair of transceiver units to achieve simultaneous full-duplex transmission and reception at the array element level would make the system extremely complex, increase hardware costs, and significantly increase the computational load of data processing. Therefore, it cannot be well applied in practical array multi-channel in-band full-duplex self-interference cancellation systems. Furthermore, while analog domain self-interference cancellation eliminates the strong self-interference components generated by crosstalk and self-interference channels within the antenna itself, residual self-interference signals and additional nonlinear components introduced after the optical system still affect the demodulation of the desired signal. This is especially true in multi-channel array systems, where deep cancellation of multiple crosstalk coupling signals is difficult to achieve through a simple analog domain approach. After analog-to-digital conversion, further processing using digital algorithms is necessary to suppress residual self-interference signals to as close as possible to the noise floor of the receiving channel, minimizing the impact of self-interference signals on the demodulation of the useful signal. Therefore, the broadband RF self-interference cancellation scheme that combines optical analog domain and electrical digital domain processing can leverage the wide frequency band and large bandwidth advantages of optical analog domain self-interference cancellation, as well as the low structural complexity and deep cancellation advantages of electrical digital domain processing, providing a solution for deep cancellation of self-interference signals in multi-channel systems. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention proposes a multi-channel self-interference cancellation device combining optical and digital domains. This device includes a signal branch module a, a reference branch module b, and a signal post-processing module c; wherein...

[0006] Signal branch module a contains n identical signal processing channels, wavelength division multiplexer 3, dispersive medium 4, wavelength demultiplexer 5, and multi-wavelength light source 8; each signal processing channel contains an identical low-noise amplifier 1, dual parallel-Mach-Zehnder modulator 2, optical power amplifier 6, and photodetector 7; the n identical signal processing channels are connected by a unified wavelength division multiplexer 3, dispersive medium 4, and wavelength demultiplexer 5, and a unified multi-wavelength light source 8 provides the required optical carrier for each signal processing channel;

[0007] Reference branch module b includes a low-noise amplifier 1, a dual parallel-Mach-Zehnder modulator 2, a tunable laser 12, an optical splitter 9, and a multi-path analog matching detection branch; wherein each of the multi-path analog matching detection branches includes an optical delay line 10, an optical attenuator 11, an optical power amplifier 6, and a photodetector 7.

[0008] The signal post-processing module c includes, in sequence, an electrical coupler 13, an analog-to-digital converter 14, and a digital signal processor 15;

[0009] Low-noise amplifier 1, in signal branch module a, receives a damaged microwave signal containing self-interference signal and useful signal, and outputs a low-noise power amplified signal; in reference branch module b, it receives a reference signal and outputs a low-noise power amplified signal; the output terminal of low-noise amplifier 1 is connected to one RF input port of dual parallel-Mach-Zehnder modulator 2.

[0010] The dual parallel-Mach-Zehnder modulator 2 has one RF input port receiving the low-noise power amplified signal output from the low-noise amplifier 1, and the other RF input port is unloaded.

[0011] Wavelength division multiplexer 3 receives optical radio frequency signals from multiple dual parallel-Mach-Zehnder modulators 2 in signal branch module a and outputs polarization-multiplexed optical radio frequency signals.

[0012] The dispersive medium 4 receives the coupled optical radio frequency signal output by the wavelength division multiplexer 3 and outputs multiple coupled optical radio frequency signals with different dispersive phases.

[0013] Wavelength demultiplexer 5 receives multiple coupled optical radio frequency signals from dispersive medium 4 and outputs multi-channel optical radio frequency signals after wavelength demultiplexing.

[0014] Optical power amplifier 6, in signal branch module a, receives the optical radio frequency signal output by wave demultiplexer 5 and outputs the optical radio frequency signal with amplified power; in reference branch module b, it receives the optical radio frequency signal with power regulated transmitted by optical attenuator 11 and outputs the optical radio frequency signal with amplified power.

[0015] The photodetector 7 receives the amplified optical radio frequency signal output from the optical power amplifier 6 and outputs a photoelectric conversion signal.

[0016] The output of the multi-wavelength light source 8 is connected to the optical input port of the dual parallel-Mach-Zehnder modulator 2 with multiple channels in the signal branch module a.

[0017] Optical splitter 9 receives the optical radio frequency signal output from the dual parallel-Mach-Zehnder modulator 2 in the reference branch module b, and outputs multiple beam-splitting signals with equal power.

[0018] Optical delay line 10 receives one beam split signal output from optical splitter 9 and outputs a delayed optical radio frequency signal.

[0019] Optical attenuator 11 receives the delayed-adjusted optical radio frequency signal output from optical delay line 10, processes it, and outputs it to optical power amplifier 6 in reference branch module b.

[0020] The output of the tunable laser 12 is connected to the optical output port of the dual parallel-Mach-Zehnder modulator 2 in the reference branch module b.

[0021] The electric coupler 13 receives the photoelectric conversion signals output by multiple photodetectors 7 in the signal branch module a and the reference branch module b, and outputs the combined photoelectric conversion signal after multi-channel coupling.

[0022] Analog-to-digital converter 14 receives the combined photoelectric conversion signal from electro-coupler 13 and outputs a digital signal;

[0023] Digital signal processing 15 receives the digital signal output from analog-to-digital converter 14, processes it, and outputs it.

[0024] The present invention also provides a method for canceling self-interference in a combined optical and digital domain multi-channel configuration, which is based on the aforementioned combined optical and digital domain multi-channel self-interference cancellation device, and the specific process is as follows:

[0025] Step 1: The multiple optical carriers generated by the multi-wavelength light source 8 in the signal branch module a are injected into the corresponding dual parallel-Mach-Zehnder modulator 2 of each channel, and modulated by the received signal after being received and amplified by the low noise amplifier 1 to generate optical radio frequency signals.

[0026] The optical carrier generated by the multi-wavelength light source 8 is represented as E. c (t)=E c expj(ω c +k m ω r )t, where E c ω c and ω r These represent the amplitude of the optical carrier wave, the zero-dispersion reference center frequency, and the optical carrier frequency tuning step size, respectively; j represents the imaginary unit; and k represents the frequency. m It is an integer, 1≤m≤n, representing the adjustable scale of the optical carrier corresponding to the m-th signal processing channel, n represents the total number of channels, t represents time, and the optical carrier is injected through the optical input port of the corresponding channel's dual parallel-Mach-Zehnder modulator 2;

[0027] The m-th signal processing channel receives a mixed received signal from the outside, containing crosstalk self-interference signals from the multi-channel array and the useful signal. This signal is first amplified by a low-noise amplifier 1 and used as the RF drive signal for the upper path of the dual parallel-Mach-Zehnder modulator 2. The lower path RF input port of the dual parallel-Mach-Zehnder modulator 2 is unloaded. Assume the mixed received signal V after passing through the low-noise amplifier 1... RFm (t) is represented as

[0028]

[0029] Where VSOIm ω SOIm τ SOIm V represents the amplitude, angular frequency, and initial delay of the useful signal in the mixed received signal of the m-th signal processing channel. SIim ω SIim τ sIim Let be the amplitude, angular frequency, and initial delay of the self-interference signal generated by the i-th signal processing channel, respectively, received in the m-th signal processing channel, where 1≤i≤n;

[0030] Adjusting the DC bias voltage of the dual-parallel Mach-Zehnder modulator 2 causes the upper sub-modulator in the dual-parallel Mach-Zehnder modulator 2 to operate at the minimum bias point, generating a carrier-suppressed double-sideband modulated signal that produces both useful and self-interference signals. The lower sub-modulator operates at the maximum bias point, generating the unmodulated optical carrier with the highest power. The main modulator operates at a positive quadrature bias point. Therefore, the output signal E of the dual-parallel Mach-Zehnder modulator 2 in the m-th signal processing channel... sm (t) is represented as

[0031]

[0032] Where β SOIm =πV SOIm / V π β SIim =πV SIim / V π V represents the modulation coefficients of the useful signal and the self-interference signal in the corresponding channel, respectively. π J is the half-wave voltage of the electro-optic modulator. 1 / 0 (β SOIm ) and J 1 / 0 (β SIim ) are the first-order and zero-order Bessel functions of the first kind for the useful signal and self-interference signal in the corresponding channel, respectively;

[0033] Step 2: The tunable laser 12 in the reference branch module b generates an optical carrier. The optical carrier is injected through the optical input port of the corresponding dual parallel-Mach-Zehnder modulator 2 in the reference branch and modulated by the reference signal after being received and amplified by the low-noise amplifier 1 to generate an optical radio frequency signal.

[0034] Let the optical carrier generated by the tunable laser 12 be represented as E. c (t)'=E c 'expj(ω c '+k'ω r ')t, where E c ',ω c ' and ω r' represents the amplitude of the optical carrier, the zero-dispersion reference center frequency, and the optical carrier frequency tuning step size, respectively. k' is an integer, and j represents the imaginary unit. The frequency of the optical carrier can be adjusted by tuning k'. The optical carrier is injected through the optical input port of the dual parallel-Mach-Zehnder modulator 2 of the reference signal branch.

[0035] After receiving the reference signal from the outside, the reference branch module b first undergoes power amplification through the same low-noise amplifier 1 as in the signal branch module a, serving as the RF drive signal for the upper path of the dual parallel-Mach-Zehnder modulator 2 in this reference branch. The RF input port of the lower path of the dual parallel-Mach-Zehnder modulator 2 is unloaded. Assume that the reference signal V after passing through the low-noise amplifier 1... REF (t) is represented as

[0036] V REF (t)=V REF expjω REF (t+τ REF (3)

[0037] Where V REF ω REF τ REF These are the amplitude, angular frequency, and initial delay of the reference signal, respectively. The DC bias voltage of the dual-parallel Mach-Zehnder modulator 2 is adjusted so that the upper sub-modulator in the dual-parallel Mach-Zehnder modulator 2 operates at the minimum bias point, generating a carrier-suppressed double-sideband modulated signal of the reference signal; the lower sub-modulator operates at the maximum bias point, generating the unmodulated optical carrier with the highest power; and the main modulator operates at a negative quadrature bias point. Therefore, the output signal E of the dual-parallel Mach-Zehnder modulator 2 in the reference branch module... r (t) is represented as

[0038]

[0039] Where β REF =πV REF / V π J1(β) is the modulation coefficient of the reference signal. REF () represents the first-order Bessel function of the first kind for the reference signal and the self-interference signal;

[0040] Step 3: The optical radio frequency signal generated in the signal branch module a is output from the dual parallel-Mach-Zehnder modulator 2 of each signal processing channel and enters the wavelength division multiplexer 3 for wavelength division multiplexing. The dispersion medium 4 is injected to introduce dispersion-induced phase, and then enters the wavelength demultiplexer 5 for wavelength demultiplexing to separate the optical radio frequency signals of different wavelengths into different channels.

[0041] The optical radio frequency modulation signals output from the dual parallel-Mach-Zehnder modulators 2 in all signal processing channels enter the wavelength division multiplexer 3 for wavelength division multiplexing. The optical radio frequency signal output from the wavelength division multiplexer 3 is the sum of the optical radio frequency modulation signals modulated on different optical carriers output from all signal processing channels. This coupled signal, after being output from the wavelength division multiplexer 3, enters the dispersion medium 4, where dispersion-induced phase is introduced into the different optical radio frequency modulation signals. The optical radio frequency modulation signal with introduced dispersion-induced phase output from the dispersion medium 4 enters the wavelength demultiplexer 5 for wavelength demultiplexing. When the most commonly used single-mode fiber is used as the dispersion medium 4, the signal output from the wavelength demultiplexer 5 is represented as follows:

[0042]

[0043] Where L and β2 are the length of the dispersive medium 4 and the second-order dispersion coefficient, respectively;

[0044] Step 4: The optical radio frequency signal generated in the reference branch module b is output from the dual parallel-Mach-Zehnder modulator 2 and then enters the optical splitter 9 for beam splitting. After that, the delay and power are adjusted by the optical delay line 10 and the optical attenuator 11.

[0045] The optical-carrying RF modulation signal output from the dual parallel-Mach-Zehnder modulator 2 enters the n-way optical splitter 9 for beam splitting. The multiple identical optical-carrying RF modulation signals output pass through optical delay lines 10 and optical attenuators 11 respectively to achieve delay and power adjustment; let the delay introduced by the m-th optical delay line 10 be τ. m The power attenuation factor introduced by the m-th optical attenuator 11 is α. m Then the delay and power-adjusted signal E output after each analog matching detection branch rm (t) is represented as:

[0046]

[0047] Step 5: The mixed signal modulation sidebands of different channels obtained by the wave demultiplexer 5 in signal branch module a and the reference signal modulation sidebands output by the optical attenuator 11 in different analog matching detection branches of reference branch module b are respectively amplified and converted by the corresponding optical power amplifier 6 and photodetector 7 to obtain the photoelectric converted signal.

[0048] In signal branch module a, the mixed signal modulated sidebands with dispersive phase from multiple channels output by wave demultiplexer 5 are injected into the corresponding optical power amplifier 6 for power amplification. The signal is then output from optical power amplifier 6 and injected into photodetector 7 to achieve photoelectric conversion. The electrical signal output by photodetector 7 is represented as:

[0049]

[0050] Among them, i sm R represents the electrical signal output by photodetector 7 in the m-th signal processing branch, R is the responsivity of photodetector 7, and G is the gain of optical power amplifier 6.

[0051] In reference branch module b, the reference signal output from the optical attenuator 11 in different analog matching detection branches is modulated and injected into the corresponding optical power amplifier 6 for power amplification. Then, it is output from the optical power amplifier 6 and injected into the photodetector 7 to achieve photoelectric conversion. The electrical signal output by the photodetector 7 is expressed as:

[0052]

[0053] Among them, i rm This represents the electrical signal after the optical signal output from the m-th analog matching detection branch is converted by photodetector 7.

[0054] Step 6: The multi-channel photoelectric conversion signals output by the photodetector 7 in the signal branch module a and the reference branch module b are coupled in the signal post-processing module c via the electrical coupler 13. Interference is eliminated by adjusting the optical delay line 10 and the optical attenuator 11 in the reference branch module.

[0055] The photodetectors 7 in signal branch module a and reference branch module b respectively output multi-channel photoelectric conversion signals containing self-interference signals and useful signals, and multi-channel photoelectric conversion signals containing reference signals. These signals are then output to the multi-channel electrical coupler 13 in signal post-processing module c for coupling. As can be seen from equations (7) and (8), due to the setting of the modulator's DC bias point, phase inversion has been inherently achieved. Therefore, the coupled multi-channel signals i s Represented as

[0056]

[0057] Equation (9) shows that by adjusting the optical delay line 10 and optical attenuator 11 in the reference branch module, the power and delay between the maximum main path of the multi-path reference signal and the multi-path self-interference signal components can be matched. After coupling, the self-interference of the multi-path main path can be eliminated. The specific matching condition is expressed as follows:

[0058]

[0059] Assuming that the self-interference component of channel i crosstalks to channel m is the main path self-interference with the highest power among all self-interference received by channel m, then Equation (10) represents that the reference signal of the m-th reference matching detection branch in the reference branch module corresponds to the self-interference component of channel i crosstalks to channel m in the m-th signal processing channel in the signal branch module. When all m reference matching detection branches satisfy the matching condition of Equation (10), 1≤m≤n. After the main path self-interference in the received signal is eliminated by the m reference matching branches, the multi-coupling useful signal and the multi-coupling residual self-interference signal will be obtained.

[0060] As can be seen from equation (9), the obtained multi-coupled useful signal has a linearly adjustable delay, and the adjustable delay is β2Lk. m ω r By rationally configuring the optical carrier frequencies of each channel output by the multi-wavelength light source 8, beamforming of the useful signals in each channel can be achieved.

[0061] Step 7: After coupling and multi-path self-interference elimination via electrical coupler 13, the multi-coupled signal containing residual self-interference and useful signal enters analog-to-digital converter 14 and digital signal processing 15 to achieve digital domain processing.

[0062] After coupling and multi-path self-interference cancellation by the electric coupler 13, the multi-coupling useful signal and the multi-coupling residual self-interference signal are entered into the analog-to-digital converter 14 to realize the analog-to-digital domain conversion. Then, the digital signal after analog-to-digital conversion enters the digital signal processing 15, where the residual self-interference is eliminated by digital algorithm.

[0063] First, disconnect signal branch module a from signal post-processing module c, connecting only reference branch module b and signal post-processing module c. Transmit the reference signal separately to signal post-processing module c, where it is sampled, quantized to the digital domain, and stored in analog-to-digital converter 14 as data. r Next, the reference branch module b is disconnected from the signal post-processing module c, and only the signal branch module a and the signal post-processing module c are connected. As agreed, the transmission of useful signals is stopped, and only the received signal, containing multiple coupled self-interference signals, is transmitted to the signal post-processing module c. In the analog-to-digital converter 14, the signal is sampled by a high-bit ADC, quantized to the digital domain, and stored as data. s Finally, connect the signal branch module a, the reference branch module b, and the signal post-processing module c. Simultaneously send the useful signal, the self-interference signal, and the reference signal. Transmit the received signal after multi-channel self-interference cancellation in the analog domain to the signal post-processing module c. In the analog-to-digital converter 14, the signal is sampled and quantized to the digital domain by a high-bit ADC and stored as data. c ;

[0064] In digital signal processing 15, the received reference signal data is first used. r and self-interference signal data s An adaptive filtering algorithm is implemented using a fast recursive least squares algorithm to minimize the error between the self-interference signal and the reference signal, thereby minimizing the filter parameter values. Subsequently, the received signal data, which includes the useful signal and residual self-interference signal, is utilized. c The useful signal is obtained by subtracting the self-interference reconstruction signal obtained by filtering the reference signal from the received signal. The useful signal is then down-converted, frequency offset and phase offset are recovered, and equalization is performed to recover the useful signal.

[0065] This invention provides a broadband radio frequency self-interference cancellation scheme that combines optical analog domain and electrical digital domain processing in a multi-channel array architecture. The scheme utilizes a matching branch in the multi-channel optical analog domain to eliminate the principal path component of the self-interference signal in each channel. After analog-to-digital conversion, a fast recursive least squares algorithm is used to further eliminate residual self-interference, minimizing the impact of self-interference signals on the useful signal. This invention achieves self-interference cancellation for a multi-channel in-band full-duplex system with a relatively small array element size and low computational cost. It leverages the wide bandwidth and broad frequency band advantages of optical analog domain self-interference cancellation, as well as the low structural complexity and deep cancellation advantages of electrical digital domain processing. Furthermore, by combining the flexible tunability of dispersive media and multi-wavelength light sources and pre-configuring the multi-channel optical carrier wavelengths, beamforming of the useful signal from multiple channels is achieved. Attached Figure Description

[0066] Figure 1 This is a schematic diagram of the structure of the radio frequency multi-channel self-interference cancellation device that combines optical analog domain and electrical digital domain processing according to the present invention. Specific implementation methods

[0067] The present invention will be further described below with reference to the accompanying drawings:

[0068] Figure 1 This is a schematic diagram of the structure of the optical analog domain and electrical digital domain joint processing radio frequency multi-channel self-interference cancellation device of the present invention. The device includes a signal branch module a, a reference branch module b, and a signal post-processing module c.

[0069] Signal branch module a contains n identical signal processing channels, a wavelength division multiplexer 3, a dispersive medium 4, a wavelength demultiplexer 5, and a multi-wavelength light source 8. The n identical signal processing channels are used to receive multi-channel input signals from the multi-channel array antenna and perform optical analog domain processing. Each signal processing channel contains an identical low-noise amplifier 1, a dual parallel-Mach-Zehnder modulator 2, an optical power amplifier 6, and a photodetector 7. The n identical signal processing channels are connected by a unified wavelength division multiplexer 3, a dispersive medium 4, and a wavelength demultiplexer 5, and a unified multi-wavelength light source 8 provides the required optical carrier for each signal processing channel.

[0070] Reference branch module b includes a low-noise amplifier 1, a dual parallel-Mach-Zehnder modulator 2, a tunable laser 12, an optical splitter 9, and a multi-path analog matching detection branch. Each of the multi-path analog matching detection branches includes an optical delay line 10, an optical attenuator 11, an optical power amplifier 6, and a photodetector 7.

[0071] The signal post-processing module c includes an electrical coupler 13, an analog-to-digital converter 14, and a digital signal processor 15.

[0072] Low-noise amplifier 1, in signal branch module a, receives a damaged microwave signal containing self-interference signal and useful signal, amplifies the microwave signal with low noise, and forms a low-noise power amplified signal output; in reference branch module b, it receives a reference signal, amplifies the reference signal with low noise, and forms a low-noise power amplified signal output; the output terminal of low-noise amplifier 1 is connected to one radio frequency input port of dual parallel-Mach-Zehnder modulator 2.

[0073] The dual parallel-Mach-Zehnder modulator 2 has one RF input port that receives the low-noise power amplified signal output from the low-noise amplifier 1, modulates the signal onto the optical carrier to form an optical carrier RF signal and outputs it, while the other RF input port is unloaded.

[0074] Wavelength division multiplexer 3 receives optical radio frequency signals from the multi-channel dual parallel-Mach-Zehnder modulator 2 in signal branch module a, performs wavelength division multiplexing on the optical radio frequency signals, and outputs polarization-multiplexed optical radio frequency signals.

[0075] The dispersive medium 4 receives the coupled optical radio frequency signal output from the wavelength division multiplexer 3, introduces a dispersion-induced phase into each channel of the optical radio frequency signal, and outputs multiple coupled optical radio frequency signals with different dispersion phases for subsequent beamforming.

[0076] Wavelength demultiplexer 5 receives multiple coupled optical radio frequency signals from dispersive medium 4, performs wavelength demultiplexing on them, and outputs multi-channel optical radio frequency signals after wavelength demultiplexing.

[0077] Optical power amplifier 6, in signal branch module a, receives the optical radio frequency signal output by wave demultiplexer 5, amplifies the optical radio frequency signal, and outputs the amplified optical radio frequency signal; in reference branch module b, it receives the power-controlled optical radio frequency signal transmitted by optical attenuator 11, amplifies the power-controlled optical radio frequency signal, and outputs the amplified optical radio frequency signal.

[0078] The photodetector 7 receives the amplified optical radio frequency signal output from the optical power amplifier 6, performs photoelectric conversion on the optical radio frequency signal, and outputs the photoelectric converted signal.

[0079] The multi-wavelength light source 8 has its output terminal connected to the optical input port of the dual parallel-Mach-Zehnder modulator 2 of multiple channels in the signal branch module a, respectively, to provide optical carriers of different wavelengths to the multiple channels.

[0080] Optical splitter 9 receives the optical radio frequency signal output from the dual parallel-Mach-Zehnder modulator 2 in the reference branch module b, performs beam splitting on it, and outputs multiple beam split signals with equal power.

[0081] Optical delay line 10 receives one beam split signal output from optical splitter 9, performs delay adjustment on it, generates a delayed optical radio frequency signal, and outputs it.

[0082] The optical attenuator 11 receives the delayed-adjusted optical radio frequency signal output from the optical delay line 10, adjusts its power, and outputs it to the optical power amplifier 6 in the reference branch module b.

[0083] The output of the tunable laser 12 is connected to the optical output port of the dual parallel-Mach-Zehnder modulator 2 in the reference branch module b, and is used to provide a tunable optical carrier to the reference branch.

[0084] The electrical coupler 13 receives photoelectric conversion signals output from multiple photodetectors 7 in the signal branch module a and the reference branch module b, couples the multiple photoelectric conversion signals, and outputs the combined photoelectric conversion signal after multiple coupling.

[0085] The analog-to-digital converter 14 receives the combined photoelectric conversion signal from the electro-coupler 13, performs analog-to-digital conversion on it, and outputs a digital signal.

[0086] Digital signal processing 15 receives the digital signal output from analog-to-digital converter 14 and performs digital domain signal processing on it.

[0087] use Figure 1 The method for canceling RF multi-channel self-interference by performing joint processing of optical analog domain and electrical digital domain, as shown in the diagram, is as follows:

[0088] Step 1: The multiple optical carriers generated by the multi-wavelength light source 8 in the signal branch module a are injected into the corresponding dual parallel-Mach-Zehnder modulator 2 of each channel, and modulated by the received signal after being received and amplified by the low noise amplifier 1 to generate optical radio frequency signals.

[0089] The optical carrier generated by the multi-wavelength light source 8 is represented as E. c (t)=E c expj(ω c +k m ω r )t, where E c ω c and ω r These represent the amplitude of the optical carrier wave, the zero-dispersion reference center frequency, and the optical carrier frequency tuning step size, respectively; j represents the imaginary unit; and k represents the frequency. m It is an integer (1≤m≤n), representing the adjustable scale of the optical carrier corresponding to the m-th signal processing channel, n represents the total number of channels, and t represents time. The optical carrier is injected through the optical input port of the dual parallel-Mach-Zehnder modulator 2 of the corresponding channel.

[0090] The m-th signal processing channel of this invention receives a mixed received signal from the outside, containing crosstalk self-interference signals from a multi-channel array and a useful signal. This signal is first amplified by a low-noise amplifier 1 and used as the RF drive signal for the upper path of the dual parallel-Mach-Zehnder modulator 2. The lower path of the dual parallel-Mach-Zehnder modulator 2 is unloaded. Assume the mixed received signal V after passing through the low-noise amplifier 1... RFm (t) can be expressed as

[0091]

[0092] Where V SOIm ω SOIm τ SOIm V represents the amplitude, angular frequency, and initial delay of the useful signal in the mixed received signal of the m-th signal processing channel. SIim ω SIim τ SIim Let V be the amplitude, angular frequency, and initial delay (1≤i≤n) of the self-interference signal received from the i-th signal processing channel in the m-th signal processing channel. In particular, V SImm ω SImm τ SImm These represent the amplitude, angular frequency, and initial delay of the reflected self-interference signal received in the m-th signal processing channel from its own channel.

[0093] Adjusting the DC bias voltage of the dual-parallel Mach-Zehnder modulator 2, the upper sub-modulator in the dual-parallel Mach-Zehnder modulator 2 operates at the minimum bias point, generating a carrier-suppressed double-sideband modulated signal that produces both the useful signal and the self-interference signal. The lower sub-modulator operates at the maximum bias point, generating the unmodulated optical carrier with the highest power. The main modulator operates at a positive quadrature bias point. Therefore, the output signal E of the dual-parallel Mach-Zehnder modulator 2 in the m-th signal processing channel... sm (t) can be represented as

[0094]

[0095] Where β SOIm =πV SOIm / V π β SIim =πV SIim / V π V represents the modulation coefficients of the useful signal and the self-interference signal in the corresponding channel, respectively. π J is the half-wave voltage of the electro-optic modulator. 1 / 0 (β SOIm ) and J 1 / 0 (β SIim ) are the first-order and zero-order Bessel functions of the first kind for the useful signal and self-interference signal in the corresponding channel, respectively.

[0096] Step 2: The tunable laser 12 in the reference branch module b generates an optical carrier. The optical carrier is injected through the optical input port of the corresponding dual parallel-Mach-Zehnder modulator 2 in the reference branch and modulated by the reference signal after being received and amplified by the low-noise amplifier 1 to generate an optical radio frequency signal.

[0097] Let the optical carrier generated by the tunable laser 12 be represented as E. c (t)'=E c 'expj(ω c '+k'ω r ')t, where E c ',ω c ' and ω r ' represents the amplitude of the optical carrier, the zero-dispersion reference center frequency, and the optical carrier frequency tuning step size, respectively. k' is an integer, and j represents the imaginary unit. The frequency of the optical carrier can be adjusted by tuning k'. The optical carrier is injected through the optical input port of the dual parallel-Mach-Zehnder modulator 2 of the reference signal branch.

[0098] After the reference branch module b of the present invention receives a reference signal from the outside, the reference signal is first amplified by a low-noise amplifier 1, the same as that in the signal branch module a, and serves as the RF drive signal for the upper path of the dual parallel-Mach-Zehnder modulator 2 in the reference branch. The RF input port of the lower path of the dual parallel-Mach-Zehnder modulator 2 is unloaded. Assume the reference signal V after passing through the low-noise amplifier 1... REF (t) is represented as

[0099] V REF (t)=V REF expjω REF (t+τ REF (13)

[0100] Where V REF ω REF τ REF These represent the amplitude, angular frequency, and initial delay of the reference signal, respectively. The DC bias voltage of the dual-parallel Mach-Zehnder modulator 2 is adjusted so that the upper sub-modulator operates at its minimum bias point, generating a carrier-suppressed double-sideband modulated signal of the reference signal; the lower sub-modulator operates at its maximum bias point, generating the unmodulated optical carrier with the highest power; and the main modulator operates at a negative quadrature bias point. Therefore, the output signal E of the dual-parallel Mach-Zehnder modulator 2 in the reference branch module... r (t) can be represented as

[0101]

[0102] Where β REF =πV REF / V π J1(β) is the modulation coefficient of the reference signal. REF ) is the first-order Bessel function of the first kind for the reference signal and the self-interference signal.

[0103] Step 3: The optical radio frequency signal generated in the signal branch module a is output from the dual parallel-Mach-Zehnder modulator 2 of each signal processing channel and enters the wavelength division multiplexer 3 for wavelength division multiplexing. The dispersion medium 4 is injected to introduce dispersion-induced phase, and then enters the wavelength demultiplexer 5 for wavelength demultiplexing to separate the optical radio frequency signals of different wavelengths into different channels.

[0104] The optical-carrying RF modulation signals output from the dual parallel-Mach-Zehnder modulators 2 in all signal processing channels enter the wavelength division multiplexer 3 for wavelength division multiplexing. The optical-carrying RF signal output from the wavelength division multiplexer 3 is the sum of the optical-carrying RF modulation signals modulated on different optical carriers from all signal processing channels. This coupled signal, after being output from the wavelength division multiplexer 3, enters the dispersion medium 4, where dispersion-induced phase is introduced onto the different optical-carrying RF modulation signals. The optical-carrying RF modulation signals with introduced dispersion-induced phase output from the dispersion medium 4 enter the wavelength demultiplexer 5 for wavelength demultiplexing. When the most commonly used single-mode fiber is used as the dispersion medium 4, the signal output from the wavelength demultiplexer 5 can be expressed as:

[0105]

[0106] Where L and β2 are the length of the dispersive medium 4 and the second-order dispersion coefficient, respectively.

[0107] Step 4: The optical radio frequency signal generated in the reference branch module b is output from the dual parallel-Mach-Zehnder modulator 2 and then enters the optical splitter 9 for beam splitting. After that, the delay and power are adjusted by the optical delay line 10 and the optical attenuator 11.

[0108] The optical-carrying RF modulation signal output from the dual parallel-Mach-Zehnder modulator 2 enters the n-way optical splitter 9 for beam splitting. The multiple identical optical-carrying RF modulation signals output pass through optical delay lines 10 and optical attenuators 11 respectively to achieve delay and power adjustment. Let the delay introduced by the m-th optical delay line 10 be τ. m The power attenuation factor introduced by the m-th optical attenuator 11 is α. m Then the delay and power-adjusted signal E output after each analog matching detection branch rm (t) can be expressed as:

[0109]

[0110] Step 5: The mixed signal modulation sidebands of different channels obtained by the wave demultiplexer 5 in signal branch module a and the reference signal modulation sidebands output by the optical attenuator 11 in different analog matching detection branches of reference branch module b are respectively amplified and converted by the corresponding optical power amplifier 6 and photodetector 7 to obtain the photoelectric converted signal.

[0111] In signal branch module a, the mixed signal modulated sidebands with dispersive phase from multiple channels output by wave demultiplexer 5 are injected into the corresponding optical power amplifier 6 for power amplification. The signal is then output from optical power amplifier 6 and injected into photodetector 7 to achieve photoelectric conversion. The electrical signal output by photodetector 7 is represented as:

[0112]

[0113] Among them, i sm R represents the electrical signal output by photodetector 7 in the m-th signal processing branch, R is the responsivity of photodetector 7, and G is the gain of optical power amplifier 6.

[0114] In reference branch module b, the reference signal output from the optical attenuator 11 in different analog matching detection branches is modulated and injected into the corresponding optical power amplifier 6 for power amplification. Then, it is output from the optical power amplifier 6 and injected into the photodetector 7 to achieve photoelectric conversion. The electrical signal output by the photodetector 7 is expressed as:

[0115]

[0116] Among them, i rm This represents the electrical signal converted from the optical signal output by the m-th analog matching detection branch by the photodetector 7.

[0117] Step 6: The multi-channel photoelectric conversion signals output by the photodetector 7 in the signal branch module a and the reference branch module b are coupled in the signal post-processing module c via the electrical coupler 13. Interference is eliminated by adjusting the optical delay line 10 and the optical attenuator 11 in the reference branch module.

[0118] The photodetectors 7 in signal branch module a and reference branch module b respectively output multi-channel photoelectric conversion signals containing self-interference signals and useful signals, and multi-channel photoelectric conversion signals containing reference signals. These signals are then output to the multi-channel electrical coupler 13 in signal post-processing module c for coupling. As can be seen from equations (7) and (8), due to the setting of the modulator's DC bias point, phase inversion has been inherently achieved. Therefore, the coupled multi-channel signals i s It can be represented as

[0119]

[0120] As can be seen from equation (9), by adjusting the optical delay line 10 and optical attenuator 11 in the reference branch module, the power and delay matching between the maximum main path of the multi-path reference signal and the multi-path self-interference signal components can be achieved. After coupling, the self-interference of the multi-path main path can be eliminated. The specific matching condition can be expressed as follows:

[0121]

[0122] Equation (10) represents the self-interference component of the i-th channel crosstalk to the m-th channel in the signal processing channel of the signal branch module, which corresponds to the reference signal of the m-th reference matching detection branch in the reference branch module (assuming that the self-interference component of the i-th channel crosstalk to the m-th channel is the main path self-interference with the highest power among all self-interference received by the m-th channel). When all m reference matching detection branches (1≤m≤n) satisfy the matching condition of Equation (10), after the main path self-interference in the received signal is eliminated by the m reference matching branches, the multi-coupling useful signal and the multi-coupling residual self-interference signal will be obtained.

[0123] As can be seen from equation (9), the obtained multi-coupled useful signal has a linearly adjustable delay, and the adjustable delay is β2Lk. m ω r By rationally configuring the optical carrier frequencies of each channel output by the multi-wavelength light source 8, beamforming of the useful signals in each channel is achieved.

[0124] Step 7: After coupling and multi-path self-interference elimination via electrical coupler 13, the multi-coupled signal containing residual self-interference and useful signal enters analog-to-digital converter 14 and digital signal processing 15 to achieve digital domain processing.

[0125] After coupling and self-interference cancellation of multiple main paths by the electric coupler 13, the multi-coupling useful signal and the multi-coupling residual self-interference signal are entered into the analog-to-digital converter 14 to realize the analog-to-digital domain conversion. Then, the digital signal after analog-to-digital conversion enters the digital signal processing 15, where the residual self-interference is eliminated by digital algorithm.

[0126] First, disconnect signal branch module a from signal post-processing module c, connecting only reference branch module b and signal post-processing module c. Transmit the reference signal separately to signal post-processing module c, where it is sampled, quantized to the digital domain, and stored in analog-to-digital converter 14 as data. r Next, the reference branch module b is disconnected from the signal post-processing module c, and only the signal branch module a and the signal post-processing module c are connected. As agreed, the transmission of useful signals is stopped, and only the received signal, containing multiple coupled self-interference signals, is transmitted to the signal post-processing module c. In the analog-to-digital converter 14, the signal is sampled by a high-bit ADC, quantized to the digital domain, and stored as data. s Finally, the device is then arranged according to... Figure 1The signal branch module a, reference branch module b, and signal post-processing module c are all connected. The useful signal, self-interference signal, and reference signal are transmitted simultaneously. The received signal after multi-channel self-interference cancellation in the analog domain (including multi-coupling useful signals and multi-coupling residual self-interference signals) is transmitted to signal post-processing module c. In analog-to-digital converter 14, it is sampled by a high-bit ADC, quantized to the digital domain, and stored as data. c .

[0127] In digital signal processing 15, the received reference signal data is first used. r and self-interference signal data s Adaptive filtering is achieved by using the fast recursive least-squares algorithm ([1] DJ Dechene, “Fast transversal recursive least-squares (FT-RLS) algorithm,” in IEEE Trans Signal Proc, Citeseer, 2007, pp. 4. [2] DPSergio, “Fast transversal RLS algorithms” in Adaptive Filtering: Algorithms and Practical Implementation, 3rd ed, 2008, pp. 333-339) to minimize the error between the self-interference signal and the reference signal. Then, the received signal data containing the useful signal and the residual self-interference signal is used. c The received signal is subtracted from the self-interference reconstructed signal obtained by filtering the reference signal to finally obtain the useful signal. The useful signal is then down-converted, frequency offset and phase offset are recovered, and equalization is performed to recover the useful signal.

[0128] This invention proposes a broadband radio frequency self-interference cancellation scheme that combines optical analog domain and electrical digital domain processing in a multi-channel array architecture. The scheme utilizes a matching branch in the multi-channel optical analog domain to eliminate the principal path component of the self-interference signal in each channel. After analog-to-digital conversion, a fast recursive least squares algorithm is used to further eliminate residual self-interference, minimizing the impact of self-interference signals on the useful signal. This invention achieves self-interference cancellation for a multi-channel in-band full-duplex system with a relatively small array element size and low computational cost. It leverages the wide bandwidth and broad frequency band advantages of optical analog domain self-interference cancellation, as well as the low structural complexity and deep cancellation advantages of electrical digital domain processing. Furthermore, by combining the flexible tunability of dispersive media and multi-wavelength light sources and pre-configuring the multi-channel optical carrier wavelengths, beamforming of the useful signal from multiple channels is achieved.

Claims

1. A multi-channel self-interference cancellation device combining optical and digital domains, characterized in that, The device includes a signal branch module a, a reference branch module b, and a signal post-processing module c; in Signal branch module a contains n identical signal processing channels, wavelength division multiplexer (3), dispersive medium (4), wavelength demultiplexer (5), and multi-wavelength light source (8); each signal processing channel contains identical low-noise amplifier (1), dual parallel-Mach-Zehnder modulator (2), optical power amplifier (6), and photodetector (7); the n identical signal processing channels are connected by a unified wavelength division multiplexer (3), dispersive medium (4), and wavelength demultiplexer (5), and a unified multi-wavelength light source (8) provides the required optical carrier for each signal processing channel; Reference branch module b includes a low-noise amplifier (1), a dual parallel-Mach-Zehnder modulator (2), a tunable laser (12), an optical splitter (9), and a multi-path analog matching detection branch; wherein each of the multi-path analog matching detection branches includes an optical delay line (10), an optical attenuator (11), an optical power amplifier (6), and a photodetector (7). The signal post-processing module c includes an electrical coupler (13), an analog-to-digital converter (14), and a digital signal processor (15) in sequence; The low-noise amplifier (1) in the signal branch module a receives a damaged microwave signal containing self-interference signal and useful signal and outputs a low-noise power amplified signal; in the reference branch module b, it receives a reference signal and outputs a low-noise power amplified signal; the output of the low-noise amplifier (1) is connected to one of the radio frequency input ports of the dual parallel-Mach-Zehnder modulator (2). A dual parallel-Mach-Zehnder modulator (2) has one RF input port receiving the low-noise power amplified signal output from the low-noise amplifier (1), and the other RF input port is unloaded. Wavelength division multiplexer (3) receives optical radio frequency signals from the multi-channel dual parallel-Mach-Zehnder modulator (2) in signal branch module a and outputs polarization-multiplexed optical radio frequency signals. Dispersive medium (4) receives coupled optical radio frequency signals output by wavelength division multiplexer (3) and outputs multiple coupled optical radio frequency signals with different dispersive phases. Wavelength demultiplexer (5) receives multi-channel coupled optical radio frequency signals from dispersive medium (4) and outputs multi-channel optical radio frequency signals after wavelength demultiplexing; The optical power amplifier (6) in the signal branch module a receives the optical radio frequency signal output by the wave demultiplexer (5) and outputs the power-amplified optical radio frequency signal; in the reference branch module b, it receives the power-modulated optical radio frequency signal transmitted by the optical attenuator (11) and outputs the power-amplified optical radio frequency signal. The photodetector (7) receives the amplified optical radio frequency signal output by the optical power amplifier (6) and outputs a photoelectric conversion signal. The output of the multi-wavelength light source (8) is connected to the optical input port of the dual parallel-Mach-Zehnder modulator (2) of multiple channels in the signal branch module a; Optical splitter (9) receives the optical radio frequency signal output from the dual parallel-Mach-Zehnder modulator (2) in the reference branch module b and outputs multiple beam split signals with equal power. Optical delay line (10) receives one beam split signal output by optical splitter (9) and outputs delayed optical radio frequency signal; The optical attenuator (11) receives the delayed-adjusted optical radio frequency signal output from the optical delay line (10), processes it, and outputs it to the optical power amplifier (6) in the reference branch module b. A tunable laser (12) is connected to the optical output port of the dual parallel-Mach-Zehnder modulator (2) in the reference branch module b. The electric coupler (13) receives the photoelectric conversion signals output by multiple photodetectors (7) in the signal branch module a and the reference branch module b, and outputs the combined photoelectric conversion signal after multi-path coupling. An analog-to-digital converter (14) receives the combined photoelectric conversion signal from the electrocoupler (13) and outputs a digital signal; Digital signal processing (15) receives the digital signal output from analog-to-digital converter (14), processes it, and outputs it.

2. A method for canceling self-interference in both optical and digital domains using a combined multi-channel system, based on the optical and digital domain combined multi-channel self-interference cancellation device as described in claim 1, characterized in that... The specific process is as follows: Step 1: The multi-wavelength light source (8) in the signal branch module a generates multiple optical carriers, which are injected into the corresponding dual parallel-Mach-Zehnder modulator (2) of each channel. They are modulated by the received signal after being received and amplified by the low noise amplifier (1) to generate optical radio frequency signals. The optical carrier generated by the multi-wavelength light source (8) is represented as E. c (t)=E c expj(ω c +k m ω r )t, where E c ω c and ω r These represent the amplitude of the optical carrier wave, the zero-dispersion reference center frequency, and the optical carrier frequency tuning step size, respectively; j represents the imaginary unit; and k represents the frequency. m It is an integer, 1≤m≤n, representing the adjustable scale of the optical carrier corresponding to the mth signal processing channel, n represents the total number of channels, t represents time, and the optical carrier is injected through the optical input port of the corresponding channel's dual parallel-Mach-Zehnder modulator (2); The m-th signal processing channel receives a mixed received signal from the outside, which includes the multi-channel array crosstalk self-interference signal and the useful signal. First, it is amplified by a low-noise amplifier (1) and used as the RF drive signal on the upper path of the dual parallel-Mach-Zehnder modulator (2). The RF input port on the lower path of the dual parallel-Mach-Zehnder modulator (2) is unloaded. Assume that the mixed received signal V after passing through the low-noise amplifier (1) is V RFm (t) is represented as Where V SOIm ω SOIm τ SOIm V represents the amplitude, angular frequency, and initial delay of the useful signal in the mixed received signal of the m-th signal processing channel. SIim ω SIim τ SIim Let be the amplitude, angular frequency, and initial delay of the self-interference signal generated by the i-th signal processing channel, respectively, received in the m-th signal processing channel, where 1≤i≤n; Adjust the DC bias voltage of the dual parallel-Mach-Zehnder modulator (2) so that the upper sub-modulator in the dual parallel-Mach-Zehnder modulator (2) operates at the minimum bias point, generating a carrier-suppressed double-sideband modulated signal that produces the useful signal and self-interference signal, while the lower sub-modulator operates at the maximum bias point, generating the unmodulated optical carrier with the highest power, and the main modulator operates at the positive quadrature bias point; therefore, the output signal E of the dual parallel-Mach-Zehnder modulator (2) in the m-th signal processing channel is... sm (t) is represented as Where β SOIm =πV SOIm / V π β SIim =πV SIim / V π V represents the modulation coefficients of the useful signal and the self-interference signal in the corresponding channel, respectively. π J is the half-wave voltage of the electro-optic modulator. 1 / 0 (β SOIm ) and J 1 / 0 (β SIim ) are the first-order and zero-order Bessel functions of the first kind for the useful signal and self-interference signal in the corresponding channel, respectively; Step 2: The tunable laser (12) in the reference branch module b generates an optical carrier. The optical carrier is injected through the optical input port of the corresponding dual parallel-Mach-Zehnder modulator (2) in the reference branch and modulated by the reference signal after being received and amplified by the low-noise amplifier (1) to generate an optical radio frequency signal. The optical carrier generated by the tunable laser (12) is denoted as E. c (t)'=E c 'expj(ω c '+k'ω r ')t, where E c ',ω c ' and ω r ' represents the amplitude of the optical carrier, the zero-dispersion reference center frequency, and the optical carrier frequency tuning step size, respectively. k' is an integer, and j represents the imaginary unit. The frequency of the optical carrier can be adjusted by tuning k'. The optical carrier is injected through the optical input port of the dual parallel-Mach-Zehnder modulator (2) of the reference signal branch. After receiving the reference signal from the outside, the reference signal is first amplified by the same low-noise amplifier (1) as in the signal branch module a, and used as the RF drive signal for the upper path of the dual parallel-Mach-Zehnder modulator (2) in the reference branch. The RF input port of the lower path of the dual parallel-Mach-Zehnder modulator (2) is unloaded. Assuming that the reference signal V after passing through the low-noise amplifier (1) is V REF (t) is represented as V REF (t)=V REF expjω REF (t+τ REF ) (3) Where V REF ω REF τ REF The amplitude, angular frequency, and initial delay of the reference signal are respectively; the DC bias voltage of the dual parallel-Mach-Zehnder modulator (2) is adjusted so that the upper sub-modulator of the dual parallel-Mach-Zehnder modulator (2) operates at the minimum bias point, generating a carrier-suppressed double-sideband modulated signal of the reference signal, the lower sub-modulator operates at the maximum bias point, generating the unmodulated optical carrier with the highest power, and the main modulator operates at the negative quadrature bias point; therefore, the output signal E of the dual parallel-Mach-Zehnder modulator (2) in the reference branch module is... r (t) is represented as Where β REF =πV REF / V π J1(β) is the modulation coefficient of the reference signal. REF () represents the first-order Bessel function of the first kind for the reference signal and the self-interference signal; Step 3: The optical radio frequency signal generated in the signal branch module a is output from the dual parallel-Mach-Zehnder modulator (2) of each signal processing channel and enters the wavelength division multiplexer (3) for wavelength division multiplexing. The dispersive medium (4) is injected to introduce the dispersion-induced phase, and then enters the wavelength demultiplexer (5) for wavelength demultiplexing to separate the optical radio frequency signals of different wavelengths into different channels. The optical radio frequency modulation signals output from the dual parallel-Mach-Zehnder modulators (2) in all signal processing channels enter the wavelength division multiplexer (3) for wavelength division multiplexing; the optical radio frequency signal output from the wavelength division multiplexer (3) is the sum of the optical radio frequency modulation signals modulated on different optical carriers output from all signal processing channels; the coupling signal enters the dispersion medium (4) after being output from the wavelength division multiplexer (3), and the dispersion-induced phase is introduced on the different optical radio frequency modulation signals by the dispersion medium (4); the optical radio frequency modulation signals with the introduced dispersion-induced phase output from the dispersion medium (4) enter the wavelength demultiplexer (5) for wavelength demultiplexing. When the most commonly used single-mode fiber is used as the dispersion medium (4), the signal output from the wavelength demultiplexer (5) is expressed as: Where L and β2 are the length of the dispersive medium (4) and the second-order dispersion coefficient, respectively; Step 4: The optical radio frequency signal generated in the reference branch module b is output from the dual parallel-Mach-Zehnder modulator (2) and then enters the optical splitter (9) for beam splitting. After passing through the optical delay line (10) and the optical attenuator (11), the delay and power are adjusted. The optical radio frequency modulation signal output from the dual parallel-Mach-Zehnder modulator (2) enters the n-way optical splitter (9) for beam splitting. The multiple identical optical radio frequency modulation signals output pass through optical delay lines (10) and optical attenuators (11) respectively to achieve delay and power adjustment; let the delay introduced by the m-th optical delay line (10) be τ. m The power attenuation factor introduced by the m-th optical attenuator (11) is α. m Then the delay and power-adjusted signal E output after each analog matching detection branch rm (t) is represented as: Step 5: The mixed signal modulation sidebands of different channels obtained by the wave demultiplexer (5) in signal branch module a and the reference signal modulation sidebands output by the optical attenuator (11) in different analog matching detection branches of reference branch module b are respectively amplified and converted by the corresponding optical power amplifier (6) and photodetector (7) to obtain the photoelectric conversion signal; In signal branch module a, the mixed signal modulated sidebands with dispersive phase from multiple channels output by wave demultiplexer (5) are injected into the corresponding optical power amplifier (6) for power amplification. Then, the signal is output from the optical power amplifier (6) and injected into the photodetector (7) to achieve photoelectric conversion. The electrical signal output by the photodetector (7) is expressed as: Among them, i sm R represents the electrical signal output by the photodetector (7) in the m-th signal processing branch, R is the responsivity of the photodetector (7), and G is the gain of the optical power amplifier (6). In reference branch module b, the reference signal output from the optical attenuator (11) in different analog matching detection branches is modulated and injected into the corresponding optical power amplifier (6) for power amplification. Then, it is output from the optical power amplifier (6) and injected into the photodetector (7) to achieve photoelectric conversion. The electrical signal output by the photodetector (7) is expressed as: Among them, i rm This represents the electrical signal converted from the optical signal output by the m-th analog matching detection branch by the photodetector (7); Step 6: The multi-channel photoelectric conversion signals output by the photodetector (7) in signal branch module a and reference branch module b are coupled in signal post-processing module c via electrical coupler (13), and interference is eliminated by adjusting the optical delay line (10) and optical attenuator (11) in the reference branch module. The photodetectors (7) in signal branch module a and reference branch module b respectively output multi-channel photoelectric conversion signals containing self-interference signals and useful signals, and multi-channel photoelectric conversion signals containing reference signals. These signals are then output to the multi-channel electrical coupler (13) in signal post-processing module c for coupling. As can be seen from equations (7) and (8), due to the setting of the modulator's DC bias point, phase inversion has been inherently achieved. Therefore, the coupled multi-channel signals i s Represented as Equation (9) shows that by adjusting the optical delay line (10) and optical attenuator (11) in the reference branch module, the power and delay between the maximum main path of the multi-path reference signal and the multi-path self-interference signal components can be matched. After coupling, the self-interference of the multi-path main path can be eliminated. The specific matching condition is expressed as follows: Assuming that the self-interference component of channel i crosstalks to channel m is the main path self-interference with the highest power among all self-interference received by channel m, then Equation (10) represents that the reference signal of the m-th reference matching detection branch in the reference branch module corresponds to the self-interference component of channel i crosstalks to channel m in the m-th signal processing channel in the signal branch module. When all m reference matching detection branches satisfy the matching condition of Equation (10), 1≤m≤n. After the main path self-interference in the received signal is eliminated by the m reference matching branches, the multi-coupling useful signal and the multi-coupling residual self-interference signal will be obtained. As can be seen from equation (9), the obtained multi-coupled useful signal has a linearly adjustable delay, and the adjustable delay is β2Lk. m ω r By reasonably configuring the optical carrier frequency of each channel output by the multi-wavelength light source (8), beamforming of the useful signal of each channel is achieved; Step 7: After coupling and multi-path self-interference elimination by the electrical coupler (13) in the signal post-processing module c, the multi-path coupled signal containing residual self-interference and useful signal enters the analog-to-digital converter (14) and digital signal processing (15) to realize digital domain processing; After coupling and multi-path self-interference elimination by the electric coupler (13), the multi-path coupled useful signal and multi-path coupled residual self-interference signal are entered into the analog-to-digital converter (14) to realize the analog-to-digital domain conversion. Then, the digital signal after analog-to-digital conversion enters the digital signal processing (15), where the residual self-interference is eliminated by digital algorithm. First, disconnect signal branch module a from signal post-processing module c, and connect only reference branch module b and signal post-processing module c. Transmit the reference signal separately to signal post-processing module c, where it is sampled, quantized to the digital domain, and stored in the analog-to-digital converter (14) by a high-bit ADC and denoted as data. r Next, disconnect the reference branch module b from the signal post-processing module c, connect only the signal branch module a and the signal post-processing module c, and stop sending useful signals as agreed. Only transmit the received signal containing multi-channel coupled self-interference signals to the signal post-processing module c. In the analog-to-digital converter (14), the signal is sampled by a high-bit ADC, quantized to the digital domain, and stored as data. s Finally, connect the signal branch module a, the reference branch module b, and the signal post-processing module c. Simultaneously send the useful signal, the self-interference signal, and the reference signal. Transmit the received signal after multi-channel self-interference cancellation in the analog domain to the signal post-processing module c. In the analog-to-digital converter (14), the signal is sampled and quantized to the digital domain by a high-bit ADC and stored as data. c ; In digital signal processing (15), the received reference signal data is first used. r and self-interference signal data s An adaptive filtering algorithm is implemented using a fast recursive least squares algorithm to minimize the error between the self-interference signal and the reference signal, thereby minimizing the filter parameter values. Subsequently, the received signal data, which includes the useful signal and residual self-interference signal, is utilized. c The useful signal is obtained by subtracting the self-interference reconstruction signal obtained by filtering the reference signal from the received signal. The useful signal is then down-converted, frequency offset and phase offset are recovered, and equalization is performed to recover the useful signal.

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