| With the rapid development of military technology,various countries have increasingly increased the functional requirements of radar antennas.The application of the radome is no longer just to provide a normal working environment for the radar antenna,but also to meet many additional functions such as reducing the adverse impact on the antenna and stealth.In this context,it is of great significance to study how to strengthen the electromagnetic wave transmission effect to achieve high gain of the antenna,and to design a suitable structure to reduce the radar cross section.Therefore,in order to achieve enhanced wave transmission to increase antenna gain,and reduce radar cross section to meet stealth conditions,researchers are constantly discovering new materials,structures,and designs.With many choices of artificial electromagnetic materials,periodic electromagnetic structures stand out with their superior electromagnetic properties.Periodic electromagnetic structure is a periodic array structure composed of similar electromagnetic scatterers,such as Phased array antennas,frequency selective surfaces,and photonic crystals have many excellent characteristics.The application research of toroidal electromagnetic metamaterials is currently receiving much attention,because the symmetrical structure has good polarization independence in electromagnetic experiments and has a positive effect on the microwave response characteristics of electromagnetic materials.Therefore,in order to explore the debit significance of the electromagnetic properties of the plasma toroidal structure for the above application problems,this paper proposes a periodic structure model of the toroidal plasma and carries out the following research work:1.Propose a centrally symmetrical plasma toroidal periodic structure.Combining theory and experimental methods,through full-wave calculations,it is found that it can form a transmittance enhancement effect greater than 10 d B in the frequency band above 1GHz.In addition,it was found that in the artificial structure,the plasma has the characteristic of suppressing the band-stop filtering of the insulating shell array.Designed and prepared a centrally symmetrical circular plasma periodic structure sample,which verified the physical phenomena found in the above theoretical calculations in experiments: In the microwave transmission experiment,the existence of plasma makes the periodic structure in the8.2-10 GHZ frequency band It has the effect of transmission enhancement,and the gain is 8-10 d B in the 1-2GHz frequency range around 9.2GHz.A field distribution measurement system built in a darkroom was used to conduct preliminary measurements on the forward-scattered electric field characteristics of the experimental sample on-off state,and it was found that the ring-shaped array structure can focus electromagnetic waves on the propagation path to the center of symmetry.2.It is found that the centrally symmetrical circular plasma periodic structure can focus the spatial distribution of electromagnetic waves and at the same time have a broadband attenuation effect on electromagnetic waves.The actual measurement results of the artificial structure sample containing the glass shell in a compact microwave anechoic chamber show that the sample has an RCS reduction effect of more than 20 d Bsm in the X-band.In the frequency range of 8.35-9.4GHz,the sample produced a 20-25 d Bsm RCS reduction on the metal circular plate at a positive angle.A comparative experiment was carried out on samples in the plasma switch state.The data showed that in the 9.8-12 GHz frequency band,when irradiated at a positive angle,the presence of plasma further reduces the RCS of the circular plate,and the amplitude is above 10 d Bsm.The RCS two-dimensional imaging data show that the scattering center distribution of the above-mentioned ring-shaped sample to the flat target can produce distortion. |
PDF Full Text Request