| As an important transmitting terminal of modern communication systems,the performance of a typical antenna is becoming more and more demanding for general civilian and military applications,and there is an immediate need to introduce new means to expand the gain,bandwidth,and axis ratio of an antenna in a limited space.The metasurface is a subwavelength oscillator as a periodic arrangement of metamaterials in the plane.The combination of metasurface and antenna brings the development of antenna into a new dimension,and the integration of two-dimensional metasurface and antenna is good.The use of various properties of the metasurface to achieve high performance antenna design has become a hot research direction in the industry.In addition,the strong electromagnetic response of the metasurface to incident waves has been introduced into the field of terahertz sensors,where the local strong electric field confinement causes the narrow-band resonant peak to be red-shifted by the change of refractive index of the object to be measured,and the sensing characteristics of the micron-level metasurface are thus generated,and the research on terahertz metasurface sensors has started in the last decade.This thesis expands the research and application of the metasurface in the field of microwave antennas and terahertz thin film sensing.The specific design process,implementation steps and results are as follows:1.A broadband high-gain miniaturized metasurface antenna based on eigenmode analysis is designed.The main modes are purified using eigenmode orientation,and this is used to design the super-surface configuration to reach high gain and achieve miniaturization.A matching bandwidth of 49.7% is achieved by using multi-stage impedance matching microstrip and sector terminal structure.Compared with the similar super-surface antennas in the listed references,the performance index of this design is outstanding,and the relative bandwidth increase reaches 91%.2.A novel terahertz dual-band metasurface biosensor is proposed.It has two effective and highly sensitive modes of operation.The structure includes an upper metallic metamaterial pattern layer,an insulating dielectric layer,and a metallic reflective layer;where the upper metallic layer is a periodic arrangement of subwavelength metasurface cells.The metasurface cell pattern composition contains two semicircular rings,and three pairs of six oscillator branches symmetrically arranged at the slit in a symmetrical structure.An equivalent LC resonant circuit with a multi-capacitor structure is constructed.When the terahertz wave is incident into the sensor coated with a vapor-drying solute film layer,it returns to the receiving point by total reflection.By calculating the absorption,this design has a significant improvement in Q value,refractive index sensitivity and Fom value compared to the conventional terahertz metaurface sensor,and has thickness sensing capability.A maximum sensitivity of 0.8THz/RIU and a Q value of 86.3 were achieved The resonant peak frequency shift of the sensor is uniform and the dual-mode operation increases the stability with excellent thin-film sensing potential.3.The design proposes a tri-polarized reconfigurable metasurface antenna with low RCS characteristics.First,a multi-mode reusable 270-degree open loop coupling feed is used,which is fed at each of the three ports to work independently to reach different antenna polarization modes.The three modes are generated by controlling the on/off of PIN diodes at the feeder layer.When ports one and two are fed separately,two circularly polarized radiation patterns with opposite spins are generated,and when port three is fed separately,the antenna radiates a 45° line polarization wave.Above the feed network,the super-surface unit adopts a rotational-phase 4*4 low-RCS triple-slotted structure,which fuses the scattering layer of the conventional low-RCS structure with the super-surface radiation layer of the antenna,reducing the number of substrate layers while ensuring the radiation performance of the antenna.This design simplifies the complex feed network of common polarizable reconfigurable antennas.The resulting RCS reduction of 12% relative bandwidth was achieved.The multiple polarization reconfigurable and low RCS characteristics make the invention promising for important applications in airborne radar stealth antennas,military,etc. |
