Tunable Metamaterials And Its Applications In Antenna

In this thesis, we mainly focus on the tunable metamaterials and its tunableelectromagnetic properties. By loading variable capacitance into metamaterials, Tunablesurface and bulk metamaterial can be realized and their tunable EM properties werestudied and validated by the theory and experiments results. Based on the tunablesurface and bulk metamaterials, frequency reconfigurable and radiation reconfigurableantenna were constructed. Besides，graphene which is a novel artificial material and itsapplication in constructing tunable metamaterials in the high frequency were studied.The main work and conclusion are listed as following:(1) Studies on the properties of tunable surface metamaterial and bulk metamaterialby loading variable capacitance. Tunable surface metamaterial and tunable bulkmetamaterial was proposed by loading varactor diode into structure. The capacitanceof the varactor diode can dynamically change the resonance frequency continuously inlarge scale, which resulted tunable electromagnetic properties. Our results indicated thatthe band gap of the surface metamaterial can be tuned continuously in the range of1.8GHz to3.2GHz. And the tunable resonance frequency and electromagneticproperties in large range for the bulk metamaterial is also validated.(2) The applications of tunable metamaterials in reconfigurable antenna. Dealingwith the requirements of reconfigurable antenna, tunable surface metamaterial and bulkmetamaterials were proposed to design frequency reconfigurable and radiation patternreconfigurable antenna, respectively. We have built the theory model for thereconfigurable antenna based on the tunable metamaterials by loading variable antenna.The results indicated that the working frequency of the frequency reconfigurableantenna can be changed continuously in the range of2.36GHz3.34GHz. And mainlobe of the radiation pattern can be tuned within34by properly arranging thedistribution of the capacitance of the varactor diode. It provides a way for us to designreconfigurable antenna. (3) Research on a novel tunable metamaterial in high frequency of microwave.Based on the inability of tunable microwave device in high frequency, we proposed toconstruct tunable metamaterials in high frequency by employing graphene. Themeasured results shown the conductivity of graphene FET and the density of the carriercan be tuned dynamically. More importantly, the tunable metamaterial in high frequencybased on graphene formed, and the simulation results demonstrated that theelectromagnetic properties of graphene tunable metamaterial could be modulateddynamically and continuously in a wide frequency range. It lays a foundation for ourfuture works on graphene tunable metamaterial.