基于DSP和CPLD的光纤光栅解调系统的设计与实现

利用可调光纤F-P滤波器作为解调元件建立了光纤光栅温度解调系统,采用数字信号处理器外部中断实现反射谱峰值的准确定位。光纤光栅温度解调实验结果表明,解调系统的测量精度得到了提高。     

光纤光栅传感系统信号解调新技术研究

信号解调是光纤光栅传感系统实用化所面临的最大难题,其核心问题在于设计高分辨率、低成本的波长检测方案。总结了光纤光栅传感信号解调的一般原理和技术难点,对常用解调方法进行了分类和归纳。目前报道的主要解调方法是滤波法、干涉法和可调光源扫描法。针对不同的解调方法,重点介绍了它们的工作原理及性能特点,评价了其优缺点,并分别给出了它们的实验原理图。对目前最有应用前景的可调谐F-P滤波法进行了详细的介绍和分析,并加入了对原有方案的改进,用气体吸收池代替原来的参考光栅。     

光纤光栅传感信号解调关键硬件电路的实验研究

基于可调谐光纤Fabry-Perot(TF F-P)滤波扫描传感光纤布拉格光栅(FBG)的反射峰的原理,针对多次实验结果,设计了构成光纤光栅信号解调稳定性所需的关键电路系统.实验结果表明,硬件优化后的解调系统与光谱仪和万用表测量的数据相比较达到了预期的目标.经过标定后的系统分辨率可达1 pm,动态测量范围可达50 nm.     

光纤陀螺方波调制误差的分析与抑制

基于光纤陀螺的调制-解调原理,讨论了调制方波的频率、相位、占空比和光纤环特征频率对方波调制误差的影响,推导出方波调制误差的数学模型.测量光纤环特征频率、调制方波频率、相位及其温度系数,分析了温度变化对方波调制误差的影响.提出了数字时域梳状滤波的解调方法,推导出消除方波调制误差的条件表达式.实验结果显示,数字时域梳状滤波可以使方波调制误差引起的偏置漂移减小到0.3°/h以下.     

On-field test campaign performance of VDE-SAT Link ID 20 over Norsat-2 LEO satellite

The latest technical recommendation by the International Telecommunication Union (ITU) for a data exchange system in the VHF maritime mobile band defines a random access channel (RAC) for communications on the uplink channel between vessels and satellites. The physical layer frame for random uplink channel is designed to allow for a more efficient use of the power amplifiers and includes features to assist the satellite receivers to resolve overlapping reception of multiple messages. This paper presents the performance results of an over-the-air test campaign carried out exploiting the NorSat-2 Low Earth orbit (LEO) satellite. After a review of the VDE-SAT RAC and Link ID 20 burst, a possible demodulator implementation is shown. Then, the VDE-SAT transmitter platform, located in Pisa, Italy, emulating a population of vessels transmitting to the NorSat-2 LEO satellite is introduced, and the test cases are described. Afterward, the analysis of the recorded signals is provided. The post-analysis first focuses on the demodulation performance in terms of probability of successful demodulation of the interfering bursts. Further investigation has also been carried out to better understand the interference environment in this frequency band for satellite signal reception. Tests indicate promising results of successfully detecting and demodulating up to 22 overlapping RAC messages, confirming the robustness of the protocol. Finally, capitalizing on the above analysis, conclusions suggest possible improvements.     

一种改进的非线性外推图像增强算法及在高分辨率图像重建中的应用

对非线性外推图像增强算法进行分析，充分考虑图像高频分量的局部特征，提出一种新的非线性滤波剪切策略包络阈值剪切算法，改进后的算法使整幅图像的增强趋于均匀化，增强效果显著改善，结合该算法重建得到的高分辨率图像，明显优于只用插值算法得到的结果。     

Bioinspired Machine-Learning-Assisted Early-Fire Perception System Based on VO2 Optical Switch

The continuation of human civilization has always been accompanied by symbiosis and confrontation with fire. Particularly, humans can comprehensively recognize fire situations based on various sensory receptors in organs (eyes, skin, nose, etc.), further forming a sound fire perception system by in-the-brain recording, modeling, and understanding fire behaviors, leading to the most accurate fire treatments. If a sensing perception system can mimic human perceptual behavior and carry out real-time fire recognition, such an active defense system can achieve real fire safety. Here, inspired by the brain-centered perception system, an early-fire perception system enabled by a VO₂-based temperature-flame-modulated optical switch, and a machine-learning-assistant demodulation algorithm is reported. This approach creates real-time monitoring composed of early fire warning (1 s for candle flame and 4 s for 130 °C heat flow), fire cause recognition (95.7% accuracy in identification), and evacuation advice provision, advancing the technologies in the perception system that enable future sensors the comprehensive perception capability for fire state.     

5G系统中基于解调参考信号的信道估计方法

5G系统使用解调参考信号(Demodulation Reference Signal,DMRS)用于下行信道估计,工程中通常采用插值法得到数据位置信道响应,考虑实际信道中噪声的影响,频域采用线性最小均方误差(Linear Minimum Mean Squared Error,LMMSE)插值算法.针对LMMSE需要获取...     

基于分布反馈激光器的局部放电监测系统研究

电力设备的局部放电监测是发现设备的绝缘缺陷、维护电网安全运行的重要手段。文章基于分布反馈(DFB)激光器线宽窄、噪声低、相干长度长等优点，设计了一种用于局部放电监测的振动传感系统。系统采用粘接在悬臂梁上的DFB激光器作为传感头，利用光纤迈克尔逊干涉仪将DFB激光器波长变化转换为干涉仪的输出光强变化，采用相位生成载波(PGC)算法进行局部放电信号解调。设计并仿真分析了悬臂梁的振动响应特性，得到其一阶谐振频率为876 Hz。研究了迈克尔逊干涉仪臂长差与系统灵敏度的关系。实验选取脉冲点火器作为局部放电源进行放电检测，验证了系统用于局部放电检测的可行性。结果表明，该系统能够检测到800～900 Hz放电信号，灵敏度可达-74.67 dB re rad/Pa。