| High peak-power antenna applied in time-domain Ultra-wide-band(UWB) radar and reconfigurable terahertz absorber have been discussed in this thesis.Our work in high-peak-power antenna is mainly composed with four parts. First, a Vivaldi antenna has been proposed with a bandwidth from 300 MHz to 1 GHz, which is applied in the time-domain UWB radar system. The dimension of the antenna is 450×290 mm. Such a design characterizes for high time-domain gain, narrow radiation patterns, short tailing duration, good fidelity, and low expense. The antenna has been measured to obtain a good agreement with the simulation. A combination of two antennas, fed by monocycle pulse with half-peak width 1.5 ns and peak voltage 2300 V, has been measured, which efficiency is more than 90 percent. Second, in order to enhance the time-domain gain, a double-ridge horn antenna(DRHA) has been proposed. The antenna has a good performance with time-domain gain 8 d B, radiation patterns ±30 degrees in E-plane and ±45 in H-plane. The outer dimension is 500×500×800 mm with bandwidth from 250 MHz to 1 GHz. However, the design is heavy and more expensive. Third, a ten- layer Luneburg Lens is placed at the aperture of the Vivaldi antenna, which the diameter of outer scale is 800 mm. The time-domain gain is enhanced for 6 d B and the HPBW is narrowed to ±30 degrees. The horn antenna is gain-enhanced mainly in H-plane at the effect of the Luneburg Lens. Finally, an equivalent lens has been proposed by digging periodical holes on an Fr4 dielectric medium, which plenty layers overlapped together to form a 3-D Lens. The equivalent lens has been simulated to have a good performance. Such a design characterizes for cheaper expense and lower weight, while the original Luneburg lens performs better in gain-enhancing. After al, our design work well and meet the requirement.Three sections have been realized in reconfigurable terahertz absorbe r. First of all, three structures of matematerial have been proposed step by step, which are all deposited on silicon wafer. The first absorber fabricates two resonances in 0.54 THz and 1.05 THz in different polarization. The second absorber fabricates three resonances in 0.523 THz, 1.083 THz and 1.06 THz in different polarization, respectively. The third absorber fabricates three resonances in 0.466 THz, 0.96 THz and 1.026 THz in different polarization, respectively. All three structures have been measured to work well. Then, considering the incident terahertz wave is linear polarization, a polarized-dependent terahertz absorber has been designed. By changing the incident polarization angles, the first resonance vanishes and second transfers into higher frequency, which an exponential curve is presented to realize the relationship between the polarizing angle and the modulation. Finally, a light-control absorber has been theoretically proposed. A silicon nitride grating has been placed on the surface of silicon wafer, covering on the surface of the matematerials. When the laser is on, photon-generated carrier is enhanced in light region, leading to high conductivity. The energy is attenuated in the arms, which will hardly generate free carrier in no- light region. Our thought may overcome the light-control problem, when substrate is narrow-gap semiconductor. |
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