Research On Microwave Photonic Radar And Jamming Signal Generation Technology

Radar systems achieve target detection of distance,speed,and orientation by analyzing the time delay,frequency-shift,and phase-shift information carried in the echo radar signals.To enhance the detection and anti-jamming capabilities of radar systems in complex battlefield environments,modern radar systems have been developed towards multi-frequency bands and large bandwidths.Similarly,radar jamming systems,aiming to disrupt the effective operation of radar systems and preventing them from obtaining correct target information,is developing towards wide working frequency bands and large instantaneous bandwidths.These two systems are opposed yet promote each other.However,electronic technology-based radar systems and jamming systems are limited by electronic bottlenecks,facing problems such as narrow working frequency,small instantaneous bandwidth,and severe electromagnetic interference between systems,which can no longer meet the increasingly complex battlefield environment.Thanks to the advantages of large bandwidth,small size,light weight,and anti-electromagnetic interference,microwave photonics technology has potential application value in many areas such as electronic reconnaissance,radar detection,radar jamming,and wireless communication in the future.Photonics-assisted radar signals generation and jamming technology can effectively overcome the limitations of electronic bottlenecks and promote systems development towards multi-frequency bands,large bandwidths,and strong tuning capabilities.In this paper,combining the development needs of future radar systems and jamming systems with the technical advantages of microwave photonics,microwave photonics radar signal generation and jamming technology were studied.The innovative results achieved are as follows:To address the issue of limited electromagnetic interference resistance in current single-band radar systems,a flexible multi-band linearly frequency modulated（LFM）microwave signals generation scheme is proposed.By increasing the number of frequency bands and the flexibility of the frequency bands,the proposed scheme greatly enhances the anti-jamming performance of radar systems.This scheme respectively achieves the double-sideband modulation（CS-DSB）of the LFM signal and phase modulation of the local oscillator（LO）signal in the upper and lower arms of an integrated dual-polarization binary phase-shift keying（DP-BPSK）modulator.The modulated signal is interfered by the polarizer（Po L）to become a linearly polarized optical signal,which is then converted to an electrical signal through the photodetector（PD）.By adjusting the phase difference introduced between the two polarization states using a polarization controller（PC）,flexible multi-band LFM microwave signals can be obtained.The simple and compact structure of this scheme and its characteristics of easy bias control make the system more stable and suitable for future multi-band radar systems,multiple-input multiple-output（MIMO）radar systems,and distributed radar systems.To address the poor range resolution and weak anti-electromagnetic interference capabilities of narrowband radar systems,a photonic approach for the generation of switchable multi-format LFM signals with large time-bandwidth product（TBWP）and immunity to power fading is proposed.Based on phase modulation the split parabolic waveform signal,LFM signals can be generated.The bandwidth of the obtained LFM signals can be greatly improved by increasing the split number of the split parabolic waveform signal.And the anti-jamming performance of the radar systems can be improved accordingly.By adjusting the bias voltage of the modulator,the format of the generated LFM signal can be flexibly switched,such as up-chirp,down-chirp,and dual-chirp LFM signals.Furthermore,the phase-modulated the split parabolic signal can directly generate single-sideband（SSB）LFM signals,making the scheme suitable for distributed deployment scenarios and capable of solving the problem of power fading in long-distance transmission.To address the challenges associated with current radar jamming systems,including narrow operating frequency range,limited instantaneous bandwidth,single jamming type,and a low number of false targets,a photonic approach to generating radar compound jamming signals based on dual-drive Mach-Zehnder Modulator（DD-MZM）is proposed.One RF port of the DD-MZM is driven by the captured radar signal,while the other RF port is driven a signal with periodic changing frequency.By adjusting the bias voltage of the DD-MZM,the optical carrier is suppressed.The modulated signal is then injected into PD for photoelectric conversion,and the radar compound jamming signal can be obtained.Each frequency point of the signal with periodic changing frequency will realize cross cosinusoidal phase-modulated jamming of the radar signal,cross cosinusoidal phase-modulated jamming with the same frequency will constitute interrupted-sampling jamming of the radar signal.Due to the absence of frequency band-restricted devices,this scheme has a wide operating frequency range and large instantaneous bandwidth.Additionally,the scheme can be biased-controlled,significantly enhancing the stability of the system,making it suitable for long-term operation of the jamming system.The cross-correlation of the generated jamming signal with the radar echo signal results in the generation of 40 false targets,effectively disrupting the radar system.To meet the requirements of radar jamming systems in terms of jamming signal authenticity,false target amplitude,and system survivability,a radar compound jamming signal generation scheme based on cascaded dual-polarization Mach-Zehnder modulator（Dpol-MZM）and phase modulator（PM）is proposed.By controlling the modulator to work at minimum transmission point（MITP）,most of the third-order intermodulation distortion（IMD3）is suppressed,improving the third-order spurious-free dynamic range（SFDR₃）of the system.By optimizing carrier-to-sideband ratio（CSR）of the system,the link gain is greatly improved.Finally,interrupted-sampling jamming,cross cosinusoidal phase-modulated jamming,time-delay jamming,and compound jamming contains any combination of them can be achieved.The effectiveness of the generated radar jamming signals is evaluated by performing cross-correlation with the original radar signals,resulting in the generation of 12 false targets.The system is capable of bias voltage control,flexible adjustment of jamming styles,a wide range of operating frequencies,and high link gain,making it potentially valuable for future radar jamming systems.