Tunable transmittivity and effective permittivity of a smart surface loaded by varactor diodes

Smart surface was developed from a thin flexible substrate of a periodic strip array loaded by varactor diodes. The tunable electromagnetic properties, such as transmittivity and effective permittivity, were investigated through free space measurement as well as numerical calculation. It was found that the proposed surfaces show significant tunable characteristics under bias voltage. Transmittivity could be adjusted continuously from -2 to -20-dB at 4-GHz. The phase angle of transmittivity could also be tuned between -40- and -75- by changing bias voltage. Good agreement was found between the measurement and the simulation results. The potential applications of such tunable properties include smart radome or modulation screens of controllable transmission or phase delay.