The Research And Application Of Electromagnetic Periodical Structure

Plane electromagnetic periodical structure has been researched,it include:frequency selective surface(FSS),electromagnetic band gap(EBG),and high impedance surface(HIS),etc.Because of its unique magnetic properties,they are widely used in the field of microwave.Based on the basic theory of electromagnetic periodical structure,FSS applied to the radome,microwave absorber screen and novel periodic decoupling structure applied to MIMO antenna are investigated.Major work is summarized as follows:1.A compact stop-band FSS structure is proposed in this paper.The FSS is consist of two square loops with different sizes and four metal patch to link the loops.The physical length and other parameters of the patches is optimized by equivalent circuit method and the commercial software HFSS.The final unit has a compact structure to reject the high floquet mode and surface wave.Meanwhile,the sample FSS is fabricated,and the measurement result is agree with the simulation,which S21 is below-15 dB over the L-band.2.A novel design method to the absorber screen based on the receiving antenna technique is presented.A broadband magneto-electric dipole antenna is selected according to the similarities of working principle between the receiving antenna and absorber.The wideband receiving antenna is improved on the theoretical basis of the wave-absorbing mechanism to the original absorber.And the original absorber is simulated and optimized by the software HFSS to obtain a thin and broadband absorber screen.The measured results show that the finite 6×6 array absorber screen provides a 10 dB RCS reduction over the entire frequency range of 1.54-3.31 GHz,which is equivalent to a relative bandwidth of 73%.Its thickness of substrate is below1/9 wavelength of the center frequency in free space.The novel absorber screen can also be used in dual polarization because of its symmetrical property.3.The design of MIMO antenna realize UWB(3.1-10.6 GHz)based on linear tapered slot antenna element and half-elliptic microstrip feed line.And dual band-notched function is achieved by using two pairs of the symmetrical 0.25? sloton the ground plane of the antenna.In addition,a pair of inverted-L slot is etched on the ground to reduce the mutual coupling over the operating band.Experimental results show that it possesses a low mutual coupling of less than-20 dB.To further improve the isolation,we propose periodical decoupling-structure applied to MIMO antenna on the basis of the design of microwave absorbing-layer unit in this paper.The MIMO antenna with periodic decoupling-structure achieves port isolation of better than-25 dB in the UWB spectrum.