光子辅助压缩采样的动态范围提升机制研究

The compressive sensing is a novel signal acquisition technique, which can reconstructing the sparse signals with very few measurements and release the demands on the analog-to-digital conversion (ADC) and digital signal processing (DSP), especially when the signals cover a very large bandwidth. The compressive sensing has been considered as a promising methodology in radio frequency (RF) or microwave applications. The photonics-assisted compressive sampling can result in the bandwidth as large as tens of GHz, which is competent for the enabling technology in the future multifunctional integration radio frequency systems. The recent researches on the photonics-assisted compressive sensing reveal its capacities in military and civilian, such as broadband multi-system cooperative communication and comprehensive situational awareness. However, the performance is now limited by the dynamic range of the photonics-assisted compressive sampling, which has however not been drawn attention. According to our primary research on the photonics-assisted compressive sensing and the optical ADC, as well as our long-term exploration on the radio-over-fiber technology, we believe the following three questions are the key for a high-quality compressive sampling in circumstances which covers an ultra-wide band and consists of multiple carriers: 1) the high peak to average power ratio and multiple nonlinearities induced by ultra-broadband and multi-carrier input; 2) the noise multiplication and nonlinear distortion crossover induced by the spectrum folding; and 3) the optics-to-electronics aperture mismatch induced by the huge bandwidth mismatch. Aiming to a high dynamic range photonics-assisted compressive sampling, our project will focus on the above three key problems and achieve innovative breakthrough in aspect of ultra-broadband noise suppression, digital linearization, and pulse-shape matching.

压缩感知和接收可以大幅度降低模数转换和数字处理的压力，在以超宽带覆盖、多载波共存为特征的微波和射频技术中广受重视。光子辅助压缩采样可将带宽扩大到几十GHz以上，在宽带多制式协同通信、战场综合态势感知和调度等军民领域具有广泛的应用前景，有望成为未来多功能一体化射频综合系统中的核心技术。当前光子压缩感知和接收的性能受限于采样过程的动态范围，其机理和提升机制尚未探索清楚。基于项目组在压缩感知、光模数转换方面的初步研究，以及在光载射频领域的长期积累，归纳以下三点是光子辅助压缩采样动态范围提升面临的关键科学问题：（1）超宽带、多载波引发的高峰均功率比和多源非线性杂波；（2）频谱折叠带来的噪声倍增和非线性杂波移位；（3）"宽入窄出"的工作模式导致的光-电孔径失配。项目将针对上述问题展开深入研究，在超宽带噪声抑制、数字线性化、脉型匹配等关键技术上取得创新性突破，提高光子压缩采样的动态范围。

压缩感知和接收可以大幅度降低模数转换和数字处理的压力，在以超宽带覆盖、多载波共存为特征的微波和射频技术中广受重视。光子辅助压缩采样可将带宽扩大到几十GHz 以上，在宽带多制式协同通信、战场综合态势感知和调度等军民领域具有广泛的应用前景，有望成为未来多功能一体化射频综合系统中的核心技术。基于项目组在压缩感知、光模数转换方面的初步研究，以及在光载射频领域的长期积累，本项目深入研究并解决了光子辅助压缩采样动态范围提升面临的关键科学问题：（1）超宽带、多载波引发的高峰均功率比和多源非线性杂波；（2）频谱折叠带来的噪声倍增和非线性杂波移位；（3）“宽入窄出”的工作模式导致的光—电孔径失配。在超宽带噪声抑制、数字线性化、脉型匹配等关键技术上取得了创新性突破，提高了光子压缩采样的动态范围。. 为此，项目研究了一种新型的“射频直采”技术，利用“射频直接带通采样”替代传统的基带采样，即直接获取目标高频宽带的信息、并将其数字化；在实现手段上，采用光子技术实现上述一体化的高频宽带采样，充分发挥光子的宽带、低时间抖动等优势。具体的，项目重点开展了高重复频率（~GHz）飞秒光纤激光器、带通采样光链路动态范围的提升与匹配、兼容带通采样的带外杂散抑制等技术研究；突破或完成高重频低抖动被动锁模光纤激光器技术、脉冲注入光电转换过程中的幅相调制转换抑制技术、多来源非线性杂散抑制和动态范围匹配技术、超宽工作频段内可调谐滤波技术等；形成了融合带通滤波和大动态范围的光子欠采样创新，研制了带通滤波光子欠采样原理样件，达到了高频（4 GHz~40 GHz）宽带（≥1 GHz）微波信号的直接采样和数字化，动态范围117 dB（1 Hz带宽）、有效采样位数≥6位等技术指标。. 项目执行期间，发表高水平SCI期刊论文15篇，做国际会议口头报告5篇（已发表4篇，会议论文未标注基金项目资助号），申请国家发明专利4项（其中已授权国家发明专利2项）。培养博士生4名、硕士生4名。