Photon-assisted radar composite interference signal generation method capable of being flexibly tuned
The multi-frequency shift keying signal generated by DD-MZM combined with intermittent sampling and comb spectrum modulation solves the problem of existing radar interference systems under high carrier frequency and large bandwidth, and achieves flexible radar interference effects and increase in the number of false targets, which is suitable for electronic warfare systems.
Patent Information
- Application Number
- CN202410002567.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-01-02
- Publication Date
- 2025-07-04
AI Technical Summary
When facing radar signals with high carrier frequency and large bandwidth, existing radar interference systems have problems such as small working range, small instantaneous bandwidth, large data volume, long response time, and high and complex channelization systems. Traditional methods have problems such as noise self-excitation and intermodulation distortion.
A photon-assisted radar composite interference signal generation method based on a dual-drive Mach Zengdel modulator (DD-MZM) is adopted. By using a multi-frequency shift keying signal combined with intermittent sampling interference and comb spectrum modulation interference, the bias voltage control of DD-MZM is used to suppress carrier double-sideband modulation to generate a composite interference signal.
It realizes the radar interference effect with a simple and compact structure, and can flexibly control the interference effect, solving the problems of insufficient power of intermittent sampling interference signal and intermodulation distortion of comb spectrum interference. The number of false targets can reach 40, which is suitable for long-term work.
Smart Images
Figure CN120254774A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the fields of optical communication technology and microwave technology, and mainly to generating radar composite interference signals by utilizing photonics technology. Background Art
[0002] In recent years, radar technology has made rapid progress. This development is extremely unfavorable to the targets to be protected. In order to prevent the effective operation of radar systems, radar jamming technology has received more and more attention. In the traditional electrical domain, a simple and effective way to achieve radar jamming is to use digital radio frequency memory (DRFM) technology to store and copy the characteristics of radar echo signals to generate radar jamming signals. However, the growing demand for high-precision and long-range detection of radar systems has led to an increase in the carrier frequency and bandwidth of radar signals. This development trend has posed a major challenge to DRFM-based electronic warfare systems. On the one hand, the electromagnetic bottleneck brings the characteristics of small working range and small instantaneous bandwidth to the DRFM-based jamming system, making it difficult to counter radar signals with high carrier frequency and large bandwidth. On the other hand, the larger signal bandwidth leads to a significant increase in the amount of data, which increases the difficulty of digital processing and leads to a longer response time for the DRFM-based jamming system. Although the problem of limited instantaneous bandwidth can be solved by channelization, the channelization system is not only costly but also complex.
[0003] Microwave photonics has the advantages of a large operating frequency range, flexible tuning, low loss, and strong resistance to electromagnetic interference, providing a new method for radar jamming signal generation. Establishing a photonic radio frequency memory (PRFM) in an optical loop can expand the operating frequency range and instantaneous bandwidth of the radar jamming system, but can only achieve delayed interference. By combining an acousto-optic frequency shifter with an optical loop, frequency shifting and delayed interference can be achieved simultaneously, but the self-excitation of the same-frequency noise in the optical loop will seriously deteriorate the quality of the generated signal. Introducing an acousto-optic frequency shifter in an optical loop can solve the problem of noise self-excitation, but it will increase the complexity and instability of the system.
[0004] Optical signal processing technology is also an effective way to generate radar jamming signals. Frequency-shift jamming signals can be generated by frequency-shifting radar signals through optical frequency combs. However, this method has serious intermodulation distortion. In addition, the frequency shift of radar signals can be achieved by phase-modulating radar signals through sawtooth signals. The limitation of this method is that the use of sawtooth signals to achieve frequency shift requires precise amplitude control and can only produce one false target. Frequency-shift jamming also changes the pulse compression width, making the false target have obvious identifiable characteristics. Summary of the invention
[0005] To solve the problems existing in the technical background, the present invention proposes a method for generating a flexible tunable photon-assisted radar composite interference signal based on a dual-drive Mach-Zehnder modulator (DD-MZM). This method can generate a radar composite interference signal combining intermittent sampling interference and comb-shaped spectrum modulation interference by using only one electro-optic modulator. This method has the advantages of simple and compact structure and can achieve good interference effects. Using a multi-frequency shift keying signal can not only solve the problem of intermittent sampling interference affecting signal power, but also solve the problem of intermodulation distortion of comb-shaped spectrum interference. By simply adjusting the multi-frequency shift keying signal, the interference effect can be flexibly controlled. The bias voltage of the DD-MZM can be controlled by a commercial bias controller, and the modulator bias voltage is stable, which is suitable for long-term working scenarios.
[0006] The radar signal and the multi-frequency shift keying signal are respectively injected into two RF ports of the DD-MZM. The bias voltage of the DD-MZM is adjusted to work at the minimum point to cancel the upper and lower optical carriers, realizing carrier-suppressed double-sideband modulation. After PD photoelectric conversion, a radar interference signal is generated. When using a periodic rectangular pulse signal, i.e., an intermittent sampling signal, as the interference template signal, an intermittent sampling interference signal will be generated; when using an electrical frequency comb signal as the interference template signal, a comb-shaped spectrum modulation interference signal will be generated; in order to combine the intermittent sampling interference and the comb-shaped spectrum modulation interference, a multi-frequency shift keying signal needs to be used as the interference template signal. After PD photoelectric conversion, an interference effect combining comb-shaped spectrum modulation interference and intermittent sampling interference will appear, and the number of false targets will increase greatly, and the interference effect is better.
[0007] The technical solution adopted by the present invention to solve its technical problems is: the device includes 1 laser source LD, 2 dual-drive Mach-Zehnder modulator DD-MZM, and 3 photodetector PD. The output end of the light source is connected to the input end of the DD-MZM. The generated multi-frequency shift keying signal is injected into one RF port as the interference template signal, and the generated linear frequency modulation signal (LFM) simulating the radar echo is injected into the other RF port. The DD-MZM works at the minimum point to cancel the carrier. Subsequently, the output signal of the DD-MZM is connected to PD photoelectric conversion. The output end of the PD is divided into two paths through a coupler, which are respectively connected to an oscilloscope and a spectrum analyzer.
[0008] The present invention includes the following steps when working: (1) The optical carrier with wavelength λ emitted from the laser LD is input into the dual-drive Mach-Zehnder modulator DD-MZM; (2) The generated periodic rectangular pulse signal, electrical frequency comb signal, and multi-frequency shift keying signal are respectively injected into one RF port of the DD-MZM, and the generated linear frequency modulation signal is injected into the other RF port of the DD-MZM; (3) Adjust the bias voltage of the DD-MZM to change the phase difference introduced by the bias voltage, so as to suppress the optical carrier; (4) Send the signal output by the DD-MZM into the PD. After photoelectric detection, a composite interference signal combined with comb spectrum modulation interference and intermittent sampling interference can be obtained.
[0009] The present invention proposes a method for generating a radar composite interference signal based on a DD-MZM. The DD-MZM is used to realize the suppressed-carrier double-sideband modulation of the radar signal and the interference template signal. After photoelectric detection by the PD, the generation of the radar interference signal is realized. By changing the type of the interference template signal, the generated interference pattern can be changed, and intermittent sampling interference, comb spectrum interference, and radar composite interference can be realized respectively.
[0010] The structure of the present invention is simple and compact. Only one modulator is used to generate the radar composite interference signal. Good interference effects can be achieved. By simply adjusting the frequency points of the multi-frequency shift keying signal, the interference effects can be flexibly controlled. Using the multi-frequency shift keying signal can not only solve the problem of the intermittent sampling interference affecting the signal power, but also solve the problem of the intermodulation distortion of the comb spectrum interference. The bias voltage of the DD-MZM can be controlled by a commercial bias controller, which makes the bias voltage of the modulator stable and suitable for the scenario of long-term operation. The interference effects are evaluated by the results of pulse compression, and the number of false targets can reach 40. The invention is stable, compact and efficient, can meet the requirements of the electronic warfare system, and has potential application value in the future electronic warfare system. Description of the Drawings
[0011] Figure 1 It is the schematic diagram for generating a flexible tunable photon-assisted radar composite interference signal. Figure 2 It is the (a) electrical spectrum, (b) waveform, (c) time-frequency diagram, and (d) cross-correlation result of the intermittent sampling interference signal generated by using a periodic rectangular pulse signal with a duty cycle of 50% and a frequency of 1 MHz as the interference template signal. Figure 3 It is the (a) electrical spectrum, (b) waveform, (c) time-frequency diagram, and (d) cross-correlation result of the intermittent sampling interference signal generated by using a periodic rectangular pulse signal with a duty cycle of 25% and a frequency of 250 kHz as the interference template signal. Figure 4 It is the (a) electrical spectrum, (b) waveform, (c) time-frequency diagram, and (d) cross-correlation result of the comb spectrum modulation interference signal generated by using an electrical comb signal with four frequency points (1 MHz, 3 MHz, 5 MHz, and 7 MHz) as the interference template signal. Figure 5The (a) electrical spectrum, (b) waveform, (c) time-frequency diagram, and (d) cross-correlation result of the composite interference signal generated by using a multi-frequency shift keying signal as the interference template signal. Detailed implementation manners
[0012] The embodiments of the present invention will be described in detail below with reference to the accompanying drawings: These embodiments are implemented on the premise of the technical solution of the present invention, and detailed implementation manners and specific operation procedures are given. However, the protection scope of the present invention is not limited to the following embodiments.
[0013] Figure 1 It is a schematic diagram of a method for generating a flexible tunable photon-assisted radar composite interference signal. The device includes 1 laser source LD, 2 dual-drive Mach-Zehnder modulator DD-MZM, and 3 photodetector PD. The two RF ports of the DD-MZM are respectively injected with the generated multi-frequency shift keying signal and linear frequency modulation signal. By controlling the bias voltage to change the introduced phase difference, the DD-MZM operates at the minimum point to suppress the optical carrier, and then it is sent to the PD for optoelectronic conversion. The signal after beat frequency is divided into two paths by an electrical coupler and sent to a spectrum analyzer and an oscilloscope for analysis respectively.
[0014] In this example, it specifically includes the following steps: Step 1: The light source generates a continuous optical wave with a working wavelength of 1550 nm and a power of 16 dBm, and this continuous optical wave is input into the DD-MZM as a carrier. Step 2: An arbitrary waveform generator outputs a periodic rectangular pulse signal with a frequency of 1 MHz, a duty cycle of 50%, and a power of -8 dBm, and then directly injects it into one of the RF ports of the DD-MZM. An LFM signal with a carrier frequency of 11 GHz, a bandwidth of 1 GHz, a pulse duration of 12 μs, and a power of -8 dBm is injected into the other RF port of the DD-MZM. The bias voltage of the modulator is adjusted to make it operate at the minimum transmission point MITP to suppress the optical carrier. Step 3: The carrier-suppressed double-sideband modulation signal is sent into a high-speed PD for optoelectronic conversion, where the responsivity of the PD is 0.65 A / W, the 3 dB working bandwidth is 33 GHz, and the amplification factor of the electrical amplifier is 20 dB. The spectrum of the signal output by the PD is observed with a spectrum analyzer, and the waveform is recorded with an oscilloscope, and finally pulse compression processing is performed with MATLAB. Step 4: The periodic rectangular pulse signal is changed to 250 kHz and a duty cycle of 25%, and the carrier frequency of the LFM signal is changed to 30 GHz, and steps 2 to 3 are repeated. Step 5: The interference template signal is changed to an electrical comb signal with four frequency points (1 MHz, 3 MHz, 5 MHz, and 7 MHz), and steps 2 to 3 are repeated. Step 6: Change the interference template signal to a multi - frequency shift keying signal combined with an electric comb signal and an intermittent sampling signal, and repeat Steps 2 to 3.
[0015] Figure 2 (a), (b), (c), and (d) are respectively the (a) electro - spectrum diagram, (b) waveform diagram, (c) time - frequency diagram, and (d) cross - correlation result of the intermittent sampling interference signal generated by using a periodic rectangular pulse signal with a duty cycle of 50% and a frequency of 1 MHz as the interference template signal. As Figure 2 (a) shows, the obtained signal has a carrier frequency of 11 GHz and a bandwidth of 1 GHz. The spectral density of the interference signal changes periodically, and the signal - to - noise ratio (SNR) is about 40 dB. Figure 2 (b) shows the waveform of the interference signal. The signal amplitude is about 10 mV, and the duration is 12 μs. The amplitude of the interference signal changes periodically with a 50% duty cycle. At Figure 2 (c) In the shown time - frequency diagram, it can be observed that the interference signal has a bandwidth of 1 GHz, a duration of 12 μs, and a duty cycle of 50%. The repetition period of the bright line is 1 μs, corresponding to a frequency of 1 MHz. The single - frequency signal at 10 GHz in the figure is due to the limited isolation of the local oscillator of the signal source. As shown in (d), the result of cross - correlating the intermittent sampling interference signal with the original radar signal is presented. It is obvious that three main false targets are generated, and around the main false target are two secondary false targets with slightly lower amplitudes; Figure 3 (a), (b), (c), and (d) are respectively the (a) electro - spectrum diagram, (b) waveform diagram, (c) time - frequency diagram, and (d) cross - correlation result of the intermittent sampling interference signal generated by using a periodic rectangular pulse signal with a duty cycle of 25% and a frequency of 250 kHz as the interference template signal. Due to the changes in the carrier frequency and intermittent sampling frequency of the LFM signal, the electro - spectrum, waveform, and time - frequency diagram of the interference signal have corresponding changes. At Figure 3 (c), it can be seen that the repetition period of the bright line becomes 4 μs, corresponding to an intermittent sampling frequency of 250 kHz. When the carrier frequency is changed to 30 GHz, the system can still accurately complete the intermittent sampling interference with a duty cycle of 25%, which proves the tunability of the system. Figure 3 (d) shows the pulse compression result after modifying the experimental parameters. Comparing Figure 2 (d) and Figure 3 (d), it can be observed that the number of generated false targets increases significantly, and the time interval between false targets decreases; Figure 4(a), (b), (c), and (d) are respectively the (a) electro-spectrogram, (b) waveform diagram, (c) time-frequency diagram, and (d) cross-correlation result of the interference signal generated after changing the interference template to an electric comb signal with four frequency points (1 MHz, 3 MHz, 5 MHz, and 7 MHz). It can be clearly observed that its electro-spectrum, waveform, and time-frequency diagram show periodic changes, and Figure 4 in the time-frequency diagram of (c), the periodic fading of the signal instantaneous power can be clearly observed. Figure 4 (d) shows the pulse compression result of the generated interference signal. It can be seen that after pulse compression of the comb spectrum modulation interference, 8 false targets with similar amplitudes will be generated. The number of false targets is jointly determined by the modulation type of the electric comb signal and the number of frequency points. Figure 5 (a), (b), (c), and (d) are respectively the (a) electro-spectrogram, (b) waveform diagram, (c) time-frequency diagram, and (d) cross-correlation result of the composite interference signal generated by using a multi-frequency shift keying signal as the interference template signal. As Figure 5 can be seen from (a), (b), and (c), the obtained signal has a carrier frequency of 30 GHz and a bandwidth of 1 GHz. The repetition period of the bright line is 4 μs, corresponding to an intermittent sampling frequency of 250 kHz. Figure 5 (d) shows the pulse compression result of the generated interference signal. It can be seen that after pulse compression of the composite interference signal, approximately 40 false targets with relatively large amplitudes can be generated. The number of false targets is jointly determined by the intermittent sampling frequency, the modulation type of the electric comb signal, and the number of frequency points, that is, the number of false targets can be adjusted by changing the multi-frequency shift keying signal.
[0016] In the present invention, only one modulator is used to generate various types of radar interference signals, achieving a good interference effect. By simply adjusting the multi-frequency shift keying signal, the interference effect can be flexibly controlled. Using the multi-frequency shift keying signal can not only solve the problem that the intermittent sampling interference affects the signal power, but also solve the problem of cross-modulation distortion of the comb spectrum interference. The bias voltage of the DD-MZM can be controlled by a commercial bias controller. The bias voltage of the modulator is stable and suitable for long-term working scenarios. The interference effect is evaluated by cross-correlation, and the number of false targets can reach 40. This invention is stable, compact, and efficient, can meet the requirements of the electronic warfare system, and has potential application value in future electronic warfare systems.
[0017] In summary, the above-described embodiments are only examples of the present invention and are not intended to limit the scope of protection of the present invention. It should be noted that for those of ordinary skill in the art, several equivalent deformations and substitutions can be made based on the disclosed content of the present invention. The optical wavelength, optical power, carrier frequency of the LFM signal, bandwidth of the broadband signal, power of the multi-frequency shift keying signal, number of frequency points, modulation type, frequency of the intermittent sampling signal, and duty cycle can all be changed. These equivalent deformations, substitutions, and adjustments of the frequency range should also be regarded as within the scope of protection of the present invention.
Claims
1. A method for generating a flexibly tunable photon-assisted radar composite interference signal, including a laser diode LD, a dual-drive Mach-Zehnder modulator DD-MZM, and a photodetector PD, characterized in that: The optical carrier output by the LD enters the DD-MZM. The multi-frequency shift keying signal is input into one of the radio frequency ports of the DD-MZM, and the radar chirp signal is input into the other radio frequency port of the DD-MZM. The bias voltage is adjusted to make the DD-MZM work at the minimum transmission point (MITP) to achieve suppression of the carrier double-sideband modulation. Subsequently, after connecting the PD and performing photoelectric detection, a radar composite interference signal can be generated. By adjusting the number of frequency points, modulation type, and intermittent sampling frequency of the multi-frequency shift keying signal, a flexibly tunable photon-assisted radar composite interference signal can be generated.