Microwave photon interference scheme with self-interference elimination function for synthetic aperture radar
By using a dual-parallel dual-drive Mach-Zehnder modulator (DP-DDMZM) and adjusting the frequency and duty cycle, flexible interference and self-interference cancellation of synthetic aperture radar (SAR) is achieved, solving the problem of limited interference effect in existing technologies and achieving a highly efficient interference effect.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-14
- Publication Date
- 2026-04-14
AI Technical Summary
Existing microwave photonic jamming schemes cannot achieve flexible and adjustable jamming in the range and orientation domains, and have failed to effectively solve the self-interference problem, resulting in limited jamming effectiveness.
The dual parallel dual-drive Mach-Zehnder modulator DP-DDMZM is used to generate two-dimensional interference signals in the range-azimuth domain by adjusting the frequency and duty cycle of the periodic rectangular pulse signal, and the self-interference signal is eliminated at the minimum point by using the sub-modulator bias voltage.
It achieves the generation of two-dimensional interference signals in the range-azimuth domain and effectively eliminates self-interference signals. It can generate false targets in both the range and azimuth domains and suppress self-interference signals with a bandwidth of 500MHz by more than 20dB.
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Figure CN121856908A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the fields of radar technology and microwave technology, and mainly to the generation of two-dimensional interference signals and the elimination of self-interference signals in the range-azimuth domain using a dual-parallel dual-drive Mach-Zehnder modulator (DP-DDMZM). Background Technology
[0002] Synthetic Aperture Radar (SAR) is widely used in military fields such as battlefield reconnaissance and precision guidance due to its advantages of all-weather, high-resolution imaging, and long range. To counter malicious reconnaissance by enemy SAR systems and protect high-value targets and important strategic areas, jamming techniques targeting SAR have become a key research focus in electronic warfare. Coherent jamming can achieve coherent gain during signal processing, greatly reducing the power requirements of jamming equipment. Intermittent Sample-Repeat Jamming (ISRJ) is a typical coherent jamming method.
[0003] In the traditional electrical domain, coherent interference is mainly addressed through digital radio frequency memory (DRFM). However, limited by electronic bottlenecks, DRFM suffers from small instantaneous bandwidth and a narrow operating frequency range. Microwave photonics, with its advantages of large instantaneous bandwidth, wide operating frequency range, and immunity to electromagnetic interference, can overcome the limitations of electrical domain interference technology and meet the trend of modern radar systems moving towards higher frequencies and wider bandwidths.
[0004] Currently proposed microwave photonics-based jamming schemes include: injecting sawtooth wave signals into a dual-polarization binary phase-shift keying modulator (DP-BPSK) to achieve frequency shifting of radar signals; using a cascaded dual-polarization Mach-Zehnder modulator (Dpol-MZM) and a phase modulator (PM) to achieve intermittent sampling-and-retransmission jamming and cross-cosine phase modulation jamming; and using dual parallel Mach-Zehnder modulators (DP-MZM) to achieve comb-spectrum modulation jamming and intermittent sampling-and-retransmission jamming. However, these methods cannot simultaneously provide flexible and adjustable jamming of SAR in both the range and azimuth domains, and none of them consider the self-interference problem, which is crucial for jammers.
[0005] Real-time jamming systems should operate in full-duplex mode to address the lag issue caused by false targets, but this also introduces self-interference problems. Due to the limited isolation between the jammer's transmitting and receiving antennas, the transmitted jamming signal can be received by the receiving antenna along with the useful signal, affecting the jamming effect and potentially causing system self-oscillation. Furthermore, since the transmitted and received signals operate in the same frequency band, self-interference signals cannot be filtered out by filters. Therefore, the Self-Interference Cancellation (SIC) module becomes a crucial component of the jamming system. Summary of the Invention
[0006] To address the technical problems existing in the background art, this invention proposes a microwave photonic jamming scheme with self-interference cancellation function for synthetic aperture radar. This method uses a dual-parallel dual-drive Mach-Zehnder modulator (DP-DDMZM) to simultaneously generate two-dimensional jamming signals in the range-azimuth domain and cancel self-interference signals. By changing the frequency and duty cycle of two periodic rectangular pulse signals, the position and number of false targets in the range and azimuth domains can be correspondingly altered.
[0007] The technical solution adopted by this invention to solve its technical problem is as follows: The method includes a laser LD, a dual-parallel dual-drive Mach-Zehnder modulator DP-DDMZM, an electrical delay line DL, an electrical attenuator ATT, and a photodetector PD. Its features are: the output port of the laser LD is connected to the input port of the DP-DDMZM; the useful signal and the self-interference signal are input together to one RF port of the sub-modulator DDMZM1; the reference signal, after passing through the electrical delay line DL and the electrical attenuator ATT, is input to the other RF port of the sub-modulator DDMZM1; a periodic rectangular pulse signal with a high level equal to the half-wave voltage value of the sub-modulator DDMZM2 and a low level equal to 0 is input to the lower RF port of the sub-modulator DDMZM2; a periodic rectangular pulse signal with a high level equal to half the half-wave voltage value of the main modulator MZM and a low level equal to 0 is input to the bias voltage port of the main modulator MZM; and the output port of the DP-DDMZM is connected to the photodetector PD.
[0008] The dual parallel dual-drive Mach-Zehnder modulator DP-DDMZM integrates one Mach-Zehnder modulator MZM and two dual-drive Mach-Zehnder modulators DDMZM. The two sub-modulators DDMZM1 and DDMZM2 are embedded in the upper and lower arms of the main modulator MZM. In addition, there is a modulation electrode on one arm of the main modulator MZM, which can apply a bias voltage to introduce an adjustable phase shift to the optical signal on that arm.
[0009] The present invention includes the following steps in operation: (1) An optical carrier with wavelength λ emitted from the laser LD is input into a dual parallel dual-drive Mach-Zehnder modulator DP-DDMZM; (2) The useful signal SOI and the self-interference signal are input together to one RF port of the sub-modulator DDMZM1 of DP-DDMZM. The reference signal is input to the other RF port of the sub-modulator DDMZM1 after passing through the electrical delay line DL and the electrical attenuator ATT. The bias voltage of the sub-modulator DDMZM1 is set to the minimum point to achieve double-sideband modulation of the suppressed carrier. (3) Input a periodic rectangular pulse signal with a high level equal to the half-wave voltage value of the sub-modulator DDMZM2 and a low level equal to 0 into the lower RF port of DDMZM2. The upper RF port of the sub-modulator DDMZM2 is unloaded. The DDMZM2 is biased at the minimum point to realize the periodic change of the amplitude of the optical carrier between the maximum and minimum values, that is, the periodic change of the presence or absence of the optical carrier. (4) Input a periodic rectangular pulse signal with a high level equal to half the half-wave voltage value of the main modulator MZM and a low level equal to 0 into the bias voltage port of MZM to realize the periodic change of the bias point of the main modulator MZM between the maximum point and the orthogonal point, that is, the periodic change of the optical carrier phase. (5) The optical signal output by DP-DDMZM is input into the photodetector PD. After photoelectric conversion, the two-dimensional interference signal in the range-azimuth domain will be generated.
[0010] This invention proposes a microwave photonic jamming scheme with self-interference cancellation function for synthetic aperture radar. The method utilizes a dual-parallel dual-drive Mach-Zehnder modulator (DP-DDMZM) to generate a two-dimensional interference signal in the range-azimuth domain and eliminate the self-interference signal. Self-interference signal elimination is achieved by setting the bias voltage of sub-modulator DDMZM1 to its minimum point. Periodic rectangular pulse signals input to the lower RF port of sub-modulator DDMZM2 are used to periodically change the optical carrier amplitude. Periodic rectangular pulse signals input to the bias voltage port of the main modulator MZM are used to periodically change the optical carrier phase. Finally, after passing through a photodetector (PD), a two-dimensional interference signal in the range-azimuth domain is generated.
[0011] This invention is the first to propose a scheme for generating two-dimensional interference signals in the range-azimuth domain and simultaneously canceling self-interference using a single integrated modulator. Attached Figure Description
[0012] Figure 1 This is a schematic diagram of the optical interference scheme with self-interference cancellation function for synthetic aperture radar according to the present invention. Figure 2 The signal without intermittent sampling. Figure 2 (a) is a waveform diagram. Figure 2 (b) is a time-frequency diagram. Figure 2 (c) is a SAR imaging result diagram; Figure 3 The signal is obtained by intermittently sampling the range domain using a periodic rectangular pulse signal with a frequency of 5MHz and a duty cycle of 50%. Figure 3 (a) is a waveform diagram. Figure 3 (b) is a time-frequency diagram. Figure 3 (c) is a SAR imaging result diagram; Figure 4This is the signal obtained when the range domain is intermittently sampled using a periodic rectangular pulse signal with a frequency of 5MHz and a duty cycle of 30%. Figure 4 (a) is a waveform diagram. Figure 4 (b) is a time-frequency diagram. Figure 4 (c) is a SAR imaging result diagram; Figure 5 The signal is obtained by intermittently sampling the range domain using a periodic rectangular pulse signal with a frequency of 10MHz and a duty cycle of 30%. Figure 5 (a) is a waveform diagram. Figure 5 (b) is a time-frequency diagram. Figure 5 (c) is a SAR imaging result diagram; Figure 6 This is the signal obtained by intermittently sampling the azimuth domain using a periodic rectangular pulse signal with a frequency of 5 kHz and a duty cycle of 50%. Figure 6 (a) is a waveform diagram. Figure 6 (b) is a time-frequency diagram. Figure 6 (c) is a SAR imaging result diagram; Figure 7 The signal is obtained by intermittently sampling the azimuth domain using a periodic rectangular pulse signal with a frequency of 5 kHz and a duty cycle of 30%. Figure 7 (a) is a waveform diagram. Figure 7 (b) is a time-frequency diagram. Figure 7 (c) is a SAR imaging result diagram; Figure 8 This is the signal obtained when the azimuth domain is intermittently sampled from a periodic rectangular pulse signal with a frequency of 10 kHz and a duty cycle of 30%. Figure 8 (a) is a waveform diagram. Figure 8 (b) is a time-frequency diagram. Figure 8 (c) is a SAR imaging result diagram; Figure 9 This refers to the signal obtained when intermittently sampling the range domain with a periodic rectangular pulse signal at a frequency of 5MHz and a duty cycle of 50%, and simultaneously intermittently sampling the azimuth domain with a periodic rectangular pulse signal at a frequency of 5kHz and a duty cycle of 50%. Figure 9 (a) is a waveform diagram. Figure 9 (b) is a time-frequency diagram. Figure 9 (c) is a SAR imaging result diagram; Figure 10 This refers to the signal obtained when the range domain is intermittently sampled using a periodic rectangular pulse signal with a frequency of 5 MHz and a duty cycle of 30%, while the azimuth domain is intermittently sampled using a periodic rectangular pulse signal with a frequency of 10 kHz and a duty cycle of 50%. Figure 10 (a) is a waveform diagram. Figure 10 (b) is a time-frequency diagram. Figure 10 (c) is a SAR imaging result diagram; Figure 11 This refers to the signal obtained when a periodic rectangular pulse signal with a frequency of 10 MHz and a duty cycle of 50% is used to intermittently sample the range domain, and a periodic rectangular pulse signal with a frequency of 5 kHz and a duty cycle of 30% is used to intermittently sample the azimuth domain. Figure 11(a) is a waveform diagram. Figure 11 (b) is a time-frequency diagram. Figure 11 (c) is a SAR imaging result diagram; Figure 12 This refers to the signal obtained when a periodic rectangular pulse signal with a frequency of 10 MHz and a duty cycle of 30% is used to intermittently sample the distance domain, and a periodic rectangular pulse signal with a frequency of 10 kHz and a duty cycle of 30% is used to intermittently sample the azimuth domain. Figure 12 (a) is a waveform diagram. Figure 12 (b) is a time-frequency diagram. Figure 12 (c) is a SAR imaging result diagram; Figure 13 (a) is the spectrum diagram of a self-interference signal with a center frequency of 12.5 GHz and a bandwidth of 500 MHz before and after cancellation. Figure 13 (b) is the spectrum diagram of the self-interference signal before and after cancellation with a center frequency of 5.5 GHz and a bandwidth of 500 MHz; Figure 14 This refers to the signal obtained when intermittently sampling the range domain with a periodic rectangular pulse signal at a frequency of 5MHz and a duty cycle of 50%, and simultaneously intermittently sampling the azimuth domain with a periodic rectangular pulse signal at a frequency of 5kHz and a duty cycle of 50%. Figure 14 (a) is a SAR imaging result before self-interference cancellation. Figure 14 (b) is a diagram of SAR imaging results after self-interference cancellation; Figure 15 This provides detailed parameters of the SAR platform and the linear frequency modulated pulse signal transmitted by the SAR. Specific implementation methods
[0013] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings: These embodiments are implemented based on the technical solution of the present invention, and provide detailed implementation methods and specific operation processes, but the protection scope of the present invention is not limited to the following embodiments.
[0014] like Figure 1As shown, this embodiment includes: a laser LD, a dual-parallel dual-drive Mach-Zehnder modulator DP-DDMZM, an electrical delay line DL, an electrical attenuator ATT, and a photodetector PD. The DP-DDMZM integrates one Mach-Zehnder modulator MZM and two dual-drive Mach-Zehnder modulators DDMZM1 and DDMZM2. The two sub-modulators DDMZM1 and DDMZM2 are embedded in the upper and lower arms of the main modulator MZM. Additionally, one arm of the main modulator MZM has a modulation electrode that can apply a bias voltage, introducing an adjustable phase shift into the optical signal on that arm. The optical carrier output from the laser LD enters the DP-DDMZM. The useful signal SOI and the self-interference signal (SIN) are input to one RF input port of the sub-modulator DDMZM1. The reference signal, after passing through the electrical delay line (DL) and the electrical attenuator (ATT), is input to the other RF input port of the sub-modulator DDMZM1. The DDMZM1 is biased at its minimum point for SIN cancellation. A high-frequency periodic rectangular pulse signal, with a high level equal to the half-wave voltage of the sub-modulator DDMZM2 and a low level equal to 0, is input to the lower RF port of the DDMZM2. The upper RF port of the sub-modulator DDMZM2 is unloaded, and the DDMZM2 is biased at its minimum point, achieving a periodic change in the amplitude of the optical carrier between its maximum and minimum values, i.e., a periodic change in the presence or absence of the optical carrier. A low-frequency periodic rectangular pulse signal, with a high level equal to half the half-wave voltage of the main modulator MZM and a low level equal to 0, is input. The signal is input to the bias voltage port of the MZM, so that the bias point of the main modulator MZM changes periodically between the maximum point and the quadrature point, that is, the optical carrier phase changes periodically. Finally, the optical signal output by the DP-DDMZM is converted into photoelectric signal by the photodetector PD, which can simultaneously realize the elimination of two-dimensional interference and self-interference signals in both the range domain and the azimuth domain.
[0015] In this example, the specific implementation steps of the method are as follows: Step 1: The laser LD generates a continuous light wave with a working wavelength of 1550nm and a power of 16dBm. This continuous light wave is used as an optical carrier input to a dual parallel dual-drive Mach-Zehnder modulator DP-DDMZM. Step Two: Use a linear frequency modulated (LFM) radar signal with an output power of 8 dBm from a vector signal source as the useful signal. It should be noted that this LFM radar signal is obtained in MATLAB based on the working principle of SAR. Detailed parameters of the SAR platform and the LFM pulse signal transmitted by the SAR are as follows: Figure 15 As shown; to reduce the amount of data, the silence time between adjacent pulses was removed, and then the remaining signal parts were connected to form a new linear frequency modulated pulse signal with a period of 10μs, including a 9μs linear frequency modulated pulse and a 1μs silence time; this operation is similar to the processing of echo signals in actual SAR imaging. The useful signal is input to the upper RF port of the sub-modulator DDMZM1, the lower RF port is left unloaded, and the bias voltage of the sub-modulator DDMZM1 is set to the minimum point to achieve double-sideband modulation of the suppressed carrier. Step 3: Use an arbitrary function generator to output a high-frequency periodic rectangular pulse signal with a frequency of 5MHz and a duty cycle of 50%. The high level of this signal is equal to the half-wave voltage value of the sub-modulator DDMZM2, and the low level is equal to 0. This signal is input to the lower RF input port of the sub-modulator DDMZM2, the upper RF port is left unloaded, the bias voltage of the sub-modulator DDMZM2 is set to the minimum point, and the bias voltage of the main modulator MZM is set to the quadrature point. Step 4: The optical signal output by the DP-DDMZM is input into the photodetector PD, and the waveform and spectrum information of the output signal of the photodetector PD are observed and analyzed using an oscilloscope and a spectrum analyzer. Step 5: In order to investigate the influence of the frequency and duty cycle of the periodic rectangular pulse signal on the position and number of false targets in the range domain, the periodic rectangular pulse signal in Step 3 was set to a frequency of 5MHz with a duty cycle of 30% and a frequency of 10MHz with a duty cycle of 30% in turn, and Step 4 was repeated. Step Six: To investigate the interference capability of this example in the azimuth domain, disconnect the signal input to the downstream RF port of the sub-modulator DDMZM2 in Step Three; the arbitrary function generator outputs a low-frequency periodic rectangular pulse signal with a frequency of 5kHz and a duty cycle of 50%. The high level of this signal is equal to half the half-wave voltage value of the main modulator MZM, and the low level is equal to 0. Input it to the bias voltage port of the main modulator MZM, set the bias voltage of the sub-modulator DDMZM2 to the maximum point, and repeat Step Four. Step 7: In order to investigate the influence of the frequency and duty cycle of the periodic rectangular pulse signal on the position and number of false targets in the azimuth domain, the periodic rectangular pulse signal in Step 6 was set to a frequency of 5kHz and a duty cycle of 30% and a frequency of 10kHz and a duty cycle of 30% respectively, and Step 4 was repeated. Step 8: To investigate the ability of this example to simultaneously interfere in the range and azimuth domains, the first output of the arbitrary function generator is the same as in Step 3, and is input to the lower RF input port of the sub-modulator DDMZM2. The bias voltage of the sub-modulator DDMZM2 is set to the minimum point. The second output of the arbitrary function generator is the same as in Step 6, and is input to the bias voltage port of the main modulator MZM. Step 4 is repeated. Step 9: To investigate the tunability of the interference capability of this example in the range and azimuth domains, the two outputs of the arbitrary function generator in Step 8 are set sequentially to a frequency of 5MHz with a duty cycle of 30% and a frequency of 10kHz with a duty cycle of 50%, a frequency of 10MHz with a duty cycle of 50% and a frequency of 5kHz with a duty cycle of 30%, and a frequency of 10MHz with a duty cycle of 30% and a frequency of 10kHz with a duty cycle of 30%, and Step 4 is repeated. Step 10: To investigate the self-interference cancellation capability of this example, disconnect the useful signal input to the upper RF port of sub-modulator DDMZM1 in Step 2, and disconnect the periodic rectangular pulse signal input to sub-modulator DDMZM2 and main modulator MZM; use a linear frequency modulated signal with a center frequency of 12.5GHz, a bandwidth of 500MHz, and a power of 12dBm output from the vector signal source as the self-interference signal, and separate one signal from the self-interference signal generated by the vector signal source as the reference signal; input the self-interference signal to the upper RF port of sub-modulator DDMZM1, and input the reference signal to the lower RF port of sub-modulator DDMZM1 after passing through the electrical delay line DL and the electrical attenuator ATT; set the bias voltage of sub-modulator DDMZM1 to the minimum point, the bias voltage of sub-modulator DDMZM2 to the maximum point, and the bias voltage of main modulator MZM to the quadrature point, and repeat Step 4. Step 11: To investigate the SAR interference capability of this example before and after self-interference cancellation, a linear frequency modulated radar signal with a center frequency of 5.5 GHz, a bandwidth of 500 MHz, and a power of 8 dBm was output from an arbitrary waveform generator as the useful signal. This signal was intermittently sampled by a periodic rectangular pulse signal with a frequency of 5 MHz and a duty cycle of 50% in the range domain and an intermittently sampled by a periodic rectangular pulse signal with a frequency of 5 kHz and a duty cycle of 50% in the azimuth domain. This signal was then used as the self-interference signal, output from a vector signal source with a power set to 12 dBm. One of the self-interference signals generated by the vector signal source was separated as a reference signal, and step 8 was repeated.
[0016] In summary, this invention utilizes DP-DDMZM to simultaneously generate two-dimensional interference signals in the range-azimuth domain and eliminate self-interference signals. By changing the frequency and duty cycle of two periodic rectangular pulse signals, the position and number of false targets in both the range and azimuth domains can be altered accordingly. This scheme can generate 25 false targets in the range-azimuth domain and achieve a self-interference signal suppression of over 20 dB with a bandwidth of 500 MHz and a center frequency of 12.5 GHz or 5.5 GHz.
[0017] In summary, the above-described embodiments are merely one example of the present invention and are not intended to limit the scope of protection of the present invention. It should be noted that those skilled in the art can make several equivalent modifications and substitutions based on the content disclosed in the present invention, and these equivalent modifications and substitutions, as well as adjustments to the frequency range, should also be considered within the scope of protection of the present invention.
Claims
1. A microwave photonic jamming scheme with self-jamming cancellation function for synthetic aperture radar, comprising a laser LD, a double parallel double drive Mach-Zehnder modulator DP-DDMZM, an electrical delay line DL, an electrical attenuator ATT, and a photodetector PD, wherein, The DP-DDMZM integrates a Mach-Zehnder modulator MZM and two dual-drive Mach-Zehnder modulators DDMZM1 and DDMZM2. The key features are as follows: The continuous optical carrier output from the laser LD enters the optical input port of the DP-DDMZM. The useful signal and the self-interference signal are input together to one radio frequency port of the sub-modulator DDMZM1. The reference signal is input to another radio frequency port of the sub-modulator DDMZM1 after passing through the electrical delay line DL and the electrical attenuator ATT. The sub-modulator DDMZM1 is biased at the minimum point for self-interference signal cancellation. A periodic rectangular pulse signal with a high level equal to half-wave voltage value of the sub-modulator DDMZM2 and a low level equal to 0 is input to the lower radio frequency port of the sub-modulator DDMZM2. The sub-modulator DDMZM2 is biased at the minimum point to achieve periodic change of optical carrier amplitude. A periodic rectangular pulse signal with a high level equal to half-wave voltage value of the main modulator MZM and a low level equal to 0 is input to the bias voltage port of the main modulator MZM to achieve periodic change of optical carrier phase. Subsequently, the optical signal output by the DP-DDMZM is converted by photoelectric detector PD to simultaneously achieve flexible and effective two-dimensional interference and self-interference signal cancellation in both the range and azimuth domains.