Broadband Periodic Structures And The Application In Microwave Absorber And Antenna

Electromagnetic Periodic Structures have been widely used in the area of microwave and antenna because of its special electromagnetic properties that the traditional materials do not possess. For example, FSS has the characteristics of bandpass and bandstop for the electromagnetic wave, so it is often used as a spatial filter. The absorbing material is widely applied in target stealth and combat,communication systems against electromagnetic interference and so on. The Artificial Magnetic Conductor is adopted in the antenna unit and antenna array to reduce the antenna section. In this paper, the main works are focused on the theory analysis on the FSSs, absorbing materials and AMCs, and also consist of the applications of the three periodic structures. Major work includes:1 、 A rejection frequency selective surface used in L-band is designed. The influence of unit structure on transmission characteristics including unit shape and size, unit spacing, medium loading, incident angle and polarization mode is analyzed systematically. Then the design of the frequency selective surface applied to radome achieves the transmission coefficient less than-15 dB from 1 GHz to 2 GHz.2、A microwave absorbing layer applied in S-band is presented. On the basic of analyzing the implementation condition and design principle of the absorbing material, making use of antenna method dedigns the microwave absorbing layer. A novel absorbing material is proposed, which exhibit a wideband over 1.71 GHz to4.48 GHz, up to a relative bandwidth of 90%, while its profile is just about 1/8 of free space wavelength at the center frequency point.3、An artificial magnetic conductor combined with broadband and low profile antenna is designed. Based on analysis of the polarization diversity technology in the base station, a pair of cross dipoles patch dual-polarized antenna fed by coaxial line with good port isolation is implemented. Using the AMC structure as a reflection plate, in this way a low profile antenna is accomplished, and its overall height falls by half compared to the original dual-polarized base station antenna. The composite antenna can be used over 1.72 GHz to 3.42 GHz, and up to a relative bandwidth of67%, meanwhile its isolation within the work band is less than-35 dB.