| PHYSICS OF GASES, PLASMAS, AND ELECTRIC DISCHARGES |
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Comparison of Three Methods in Extracting Coherent Modes from a Doppler Backscatter System |
| ZHANG Xiao-Hui, LIU A-Di**, ZHOU CHU, HU Jian-Qiang, WANG Ming-Yuan, YU Chang-Xuan, LIU Wan-Dong, LI Hong, LAN Tao, XIE Jin-Lin |
Department of Modern Physics, University of Science and Technology of China, Hefei 230026
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| Cite this article: |
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ZHANG Xiao-Hui, LIU A-Di, ZHOU CHU et al 2015 Chin. Phys. Lett. 32 125201 |
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Abstract We compare three different methods to extract coherent modes from Doppler backscattering (DBS), which are center of gravity (COG) of the complex amplitude spectrum, spectrum of DBS phase derivative (phase derivative method), and phase spectrum, respectively. These three methods are all feasible to extract coherent modes, for example, geodesic acoustic mode oscillation. However, there are still differences between dealing with high frequency modes (several hundred kHz) and low frequency modes (several kHz) hiding in DBS signal. There is a significant amount of power at low frequencies in the phase spectrum, which can be removed by using the phase derivative method and COG. High frequency modes are clearer by using the COG and the phase derivative method than the phase spectrum. The spectrum of DBS amplitude does not show the coherent modes detected by using COG, phase derivative method and phase spectrum. When two Doppler shifted peaks exist, coherent modes and their harmonics appear in the spectrum of DBS amplitude, which are introduced by the DBS phase.
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Received: 26 May 2015
Published: 05 January 2016
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