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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. [ABSTRACT FROM AUTHOR]

Abstract: The magnetic plasmon polaritons (MPPs) and their slow wave effect are experimentally studied in the two-dimensional (2D) ENG/MNG (ε-negative materials/μ-negative materials) metamaterials based on microstrip lines’ structure. Electric field mainly locates at the ENG/MNG interface and decays in the ENG materials and MNG ones, as reveals evident MPPs characteristics. MPP waves propagate slowly along the ENG/MNG metamaterials with opposite group and phase velocities, as is studied through the time-domain analysis. Theoretical analysis agrees well with CST simulation and microwave measurement. [Copyright &y& Elsevier]

Abstract: Based on theoretical analysis, this paper studied experimentally the tunable low-pass, band-stop and band-pass filter effects of the MNG-DPS-MNG (μ-negative materials/double positive materials/μ-negative materials) magnetic plasmon polaritons waveguide. The research results show that the MNG-DPS-MNG waveguide without defect possesses the tunable low-pass filter characteristic. The waveguide with defect in the MNG region possesses the band-stop filter characteristic where the defect is equivalent to a sub wavelength cavity. And the waveguide with cavity in the DPS region possesses the band-pass filter characteristic. So the filter characteristics of the magnetic plasmon polaritons waveguide can be tuned by drawing into the resonators and changing the position and parameters of resonators. The experimental results are in good agreement with the simulation results. These properties will have potential application value in the tunable single channel or multi-channel filters. [Copyright &y& Elsevier]

Abstract: The electromagnetic properties of an MNG–DPS–MNG surface plasmon-like channel with side defect based on transmission line structure are experimentally studied. The results of simulation and experiment show that the channel with a single side defect is not transparent to electromagnetic (EM) waves because of the resonators effect. While a transmission peak appears in the channel with double side defects because of the destructive interference between the two resonance modes of the two resonators. It indicates that an evident electromagnetically induced transparency (EIT) phenomenon appears in microwave frequencies. In addition, the slow wave peculiarity of the EIT-like phenomenon in the surface plasmon-like channel is studied through the computer simulation technology (CST) simulation and time-domain measurement. [Copyright &y& Elsevier]