基于正交偏振双光频梳的大时宽带宽积线性调频信号产生

The fast development of multi-function and ultrahigh-resolution radar systems has an urgent requirement of linear frequency-modulated (LFM) signals with high frequency, broad bandwidth and large time-bandwidth product (TBWP), which can be generated by photonics-based LFM signal generation methods since the photonics technologies could break through the limitations of electronic bottleneck. However, most of the previously reported photonics-based LFM signal generation methods still have problems associated with small TBWP, poor scalability and high requirement of electrical fundamental waveforms. To deal with these problems, a new LFM signal generator based on orthogonally-polarized dual- optical frequency comb (OFC) sequences and opto-electronic phase modulations is proposed and investigated in this project. The main novelties and innovations of this project are as follows. Firstly, thanks to the abundant spectrum sources of photonics, orthogonally-polarized dual-comb sequences can be generated by using a circularly frequency-shifting loop, which would ensure the broad bandwidth and large time duration of the generated LFM signal from the optical sources. Then, a split parabolic signal is generated thanks to the flexibility of the electronic waveform generator, which is applied to a phase modulator (PM) or a polarization modulator (PolM) to introduce a parabolic phase difference to the orthogonally-polarized dual-comb sequences. As a result, an LFM signal with a large TBWP can be generated. Thirdly, with the high parallel-processing capability of the photonic technology, multi-channel LFM signals with their parameters independently adjustable can be generated if an optical splitter and multiple optical filters are employed. The research will be carried out through both theoretical and experimental investigations. The project is expected to generate 2 channels of LFM signals with their TBWPs larger than 20000. The proposed LFM signal generator could powerfully provide theoretical basic and technical supports for the next generation of radars and the relatively research areas.

多功能高精度雷达的高速发展对高频、宽带、大时宽带宽积线性调频信号源提出了迫切需求。基于光子技术的信号产生方法，能突破电子瓶颈的限制，产生高频宽带线性调频信号，但其仍然面临时宽带宽积小、电基带波形要求高、难以多路拓展等挑战。针对上述挑战，本项目提出了基于正交偏振双光频梳的大时宽带宽积线性调频信号产生方案：通过循环移频产生正交偏振双光频梳，利用光域频谱资源丰富的特点，保证了线性调频信号的宽带和大时宽；通过对正交偏振双光频梳进行分段抛物线相位调制，利用电域波形操控灵活的特性，对拍频后信号进行时、频域拼接，实现大时宽带宽积线性调频信号的产生；结合光分路与滤波，利用光域并行处理能力强的特点，得到多路并行、参数独立可控的线性调频信号。本项目将采用理论和实验相结合的方式对所提方案进行分析研究，实现时宽带宽积≥20000的多路线性调频信号产生，为未来多功能高精度雷达的突破和创新提供技术支撑。

多功能高精度雷达的高速发展对高频、宽带、大时宽带宽积线性调频信号源提出了迫切需求。基于光子技术的信号产生方法，能突破电子瓶颈的限制，产生高频宽带线性调频信号，但其仍然面临时宽带宽积难以进一步提升、电基带波形要求高、难以多路拓展等挑战。针对上述挑战，本项目提出并论证了基于循环移频的可重构微波光子雷达波形源，突破了大时宽带宽积提升、可重构参数调控机理等关键难题；实验产生了可重构跳频信号、单啁啾/双啁啾/多啁啾线性调频信号、以及双波段线性调频信号等波形产生，所产生信号的时宽带宽积可达120000及以上；分析了不同波形的模糊函数特性以及功率不平衡对双啁啾线性调频信号模糊函数的影响；实验验证了亚厘米分辨率的微波光子雷达成像；实现了宽带射频自干扰对消及灵敏度提升方案，以及宽带色散补偿方案，使系统信噪比得到有效提升，为未来多功能高精度雷达的突破和创新提供技术支撑。