title: Realizing Tunable Inverse and Normal Doppler Shifts in Reconfigurable RF Metamaterials.
abstract: The Doppler effect has well-established applications in astronomy, medicine, radar and metrology. Recently, a number of experimental demonstrations of the inverse Doppler effect have begun to appear. However, the inverse Doppler effect has never been observed on an electronically reconfigurable system with an external electromagnetic wave source at radio frequencies (RF) in experiment. Here we demonstrate an experimental observation of the inverse Doppler shift on an electronically reconfigurable RF metamaterial structure, which can exhibit anomalous dispersion, normal dispersion or a stop band, depending on an applied bias voltage. Either inverse or normal Doppler shift is realized by injecting an external RF signal into the electronically reconfigurable metamaterial, on which an electronically controllable moving reflective boundary is formed. The effective velocity of this boundary and the resulting frequency shift can be tuned over a wide range by a digital switching circuit. This work is expected to open up possibilities in applying the inverse Doppler effect in wireless communications, radar and satellite navigation.
authors.affiliation: Tongji University, Shanghai, 200092, China.
authors.forename: Jia
authors.initials: J
authors.lastname: Ran
authors.affiliation: Tongji University, Shanghai, 200092, China.
authors.forename: Yewen
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: 1] University of Electronic Science and Technology of China, Chengdu, 610054, China [2] Queen Mary University of London, E1 4NS, UK.
authors.forename: Xiaodong
authors.initials: X
authors.lastname: Chen
authors.affiliation: Tongji University, Shanghai, 200092, China.
authors.forename: Kai
authors.initials: K
authors.lastname: Fang
authors.affiliation: Tongji University, Shanghai, 200092, China.
authors.forename: Junfei
authors.initials: J
authors.lastname: Zhao
authors.affiliation: Tongji University, Shanghai, 200092, China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Sun
authors.affiliation: Tongji University, Shanghai, 200092, China.
authors.forename: Hong
authors.initials: H
authors.lastname: Chen