Research on the Method of Improving Terahertz Frequency Resolution Based on Empirical Mode Decomposition
LU Min1, LI Xiao-xia1,2*, SHANG Li-ping2, DENG Hu1,2
1. School of Information Engineering, Southwest University of Science and Technology, Mianyang 621010, China 2. Robot Technology Used for Special Environment Key Laboratory of Sichuan Province, Mianyang 621010, China
Abstract:Terahertz frequency resolution is an important factor affecting substance identification, but the presence of the device reflection within the terahertz time domain spectroscopy systems, causes the presence of a plurality of reflection peaks in the reference and measurement signals with low frequency resolution, because of the length truncation of time domain signal. In order to remove the influence of the reflection peak, this paper proposes a method based on empirical mode decomposition to remove the time domain reflection peak, to improve the terahertz frequency resolution. The time domain reflection peaks are positioned by correlation with the real terahertz peak, calculating the reflection peak upper and lower envelope and an average, obtaining intrinsic mode functions, and alternating reflection peaks with intrinsic mode functions, the effective length of the time domain signal is increased to improve the terahertz frequency resolution. Water vapor in the air terahertz transmission spectroscopy results show that this method can self adaptively remove a plurality of reflection peaks and has good repairing effect on the terahertz time-domain signal; the frequency resolution is increased by 12 times; and the useful information of absorption spectrum is not lost; the absorption peak position and the number is consistent with real spectrum; the terahertz spectrum ability to identify is well preserved.
卢 敏1,李小霞1,2*,尚丽平2,邓 琥1,2 . 基于经验模态分解提高太赫兹频率分辨率的方法 [J]. 光谱学与光谱分析, 2016, 36(09): 2732-2735.
LU Min1, LI Xiao-xia1,2*, SHANG Li-ping2, DENG Hu1,2 . Research on the Method of Improving Terahertz Frequency Resolution Based on Empirical Mode Decomposition . SPECTROSCOPY AND SPECTRAL ANALYSIS, 2016, 36(09): 2732-2735.
[1] Siegel P H. IEEE Transactions on Microwave Theory and Techniques, 2002, 50(3): 910. [2] Massaouti M, Daskalaki C, Gorodetsky A, et al. Applied Spectroscopy, 2013, 67(11): 1264. [3] HE Ting, SHEN Jing-ling(和 梃,沈京玲). Spectroscopy and Spectral Analysis(光谱学与光谱分析),2013,33(9):2348. [4] Huhn, A K, Saenz E, De Maagt P, et al. IEEE Transactions on Terahertz Science and Technology, 2013, 3(5): 649. [5] Conti Nibali, Valeria, Havenith Martina. Journal of the American Chemical Society, 2014, 136(37): 12800. [6] Brahm A, Tymoshchuk M, Wichmann F, et al. Journal of Infrared Millimeter and Terahertz Waves, 2014, 35(11): 974. [7] LI Li-long,XIANG Yang, WU Lei, et al(李利龙,向 洋,吴 磊,等). High Power Laser and Particle Beams(强激光与粒子束), 2013, 25(6): 1566. [8] CHENG Pei-qing(程佩青). Digital Signal Processing Tutorial(数字信号处理教程). Beijing: Tsinghua University Press(北京:清华大学出版社),2007. 100. [9] ZHANG Xian-da(张贤达). Modern Signal Processing(现代信号处理). Beijing: Tsinghua University Press(北京:清华大学出版社),2002. 121. [10] Wu Z, Huang N E. Advances in Adaptive Data Analysis, 2009, 1(1): 1. [11] ZHANG Yu-yan, ZHOU Hang, YAN Mei-su(张玉燕,周 航,闫美素). Acta Physica Sinica(物理学报),2015,64(5):054203. [12] LIU Tong, XU Zheng-wu, WU Yuan-jie, et al(刘 通,徐政五,吴元杰,等). Journal of Signal Processing, 2013, 29(12): 1650. [13] Jiang L, Li C, Huang L. Advance Journal of Food Science and Technology, 2014, 6(5): 578.