Theory Of All-angle Artificial Periodic Structures And Their Applications To Electromagnetic Shielding

With the development of 5G communication technology,the integration and clock frequency of high-speed electronic devices are gradually increased.The increasingly complex electromagnetic environment makes the electronic equipment suffer from electromagnetic interference(EMI).How to effectively utilize the electromagnetic signal propagation and shield the harmful electromagnetic radiation becomes a great challenge in the development and innovation of communication technology.As a research hotspot in electromagnetic field,frequency selective surface(FSS)has unique advantages in controlling electromagnetic waves.As a result,FSS has been widely applied to shield the electromagnetic interference in communication systems.However,the electromagnetic environment is becoming more and more complex,which brings many extreme requirements to electromagnetic shielding.At the same time,there are still many technical and theoretical bottlenecks in FSS research: 1)The working frequency of the traditional FSS structure will shift under the oblique incidence,resulting in the performance deterioration.Particularly,FSS is usually more sensitive to the incident angle for TM mode,while the mechanism for this is still unclear.2)The traditional multi-band FSS structure suffers from serious frequency offset in the highfrequency band.3)The traditional wide-angle stable miniaturized FSS structure is difficult to fabricate in the millimeter-wave band,and the research for the structutes with all the characteristics of wide-angle stable,wide bandwidth and rapid decline of working band edge in the high-frequency band is rare.Aiming at the engineering problems of EMI shielding in communication systems and the theoretical bottleneck of the artificial periodic structure,this paper has carried out the following innovative research work:1)A concept of all-angle-insensitive strong coupled FSS(SC-FSS)is proposed in this paper.The working mechanism of the FSS structure with all-angle stability is revealed.For both TE and TM modes,the transmission zero is always stable at 2GHz even when the incident angle is increased to 84°,which can completely solve the frequency offset problem of transmission zero of traditional band-stop FSS under oblique incidence and provides a new direction for the study of angle stability of FSS structures with more complex functions.2)A novel all-angle-insensitive miniaturized FSS radome is proposed,which is applied to 5G communication(mainly for S-band).The theoretical mechanism that TM wave is more sensitive to incident angle is revealed,and the design guideline of all-angle-stable band-pass FSS structure is summarized.Measured results show that the transmission poles and transmission zeros for both TE and TM modes are stable at 2 GHz and 3.4 GHz respectively in the incident angle range of 0°-84°,which has solved the frequency offset problem of traditional FSS radome under oblique incidence,and filled the theoretical vacancy that TM Mode waves are more sensitive to the incident angle in previous FSS research works.The proposed structure has great application prospects in the wide-angle-stable high performance radome and provides a new idea for the theoretical research of angle stability for TM Mode.3)A novel multi-band FSS radome with all-angle and all-polarization stability is proposed.An accurate equivalent circuit model is constructed,which can simulate the transmission response at any incident angle for TE and TM Modes.The circuit simulation results are in good agreement with full-wave simulation results.Measured results show that two transmission poles and two transmission zeros are stable at 2 GHz & 5.8 GHz and 3.8 GHz & 7.4 GHz,respectively,at any incident angle for TE and TM Modes,which can solve the frequency offset problem of the high-frequency band in previous multi-band FSS structures,and promotes the application of the all-angle-stable high-performance multi-band radome.4)A novel non-miniaturized wide-angle and wide-band FSS radome is proposed in this paper,which is applied to 5G communication(mainly for Ka-band).The unit size of the designed structure is about 0.28 ?,but the passband and stopband are highly stable in the incident angle range of 0°-60°,which breaks the limitation of traditional designs which commonly seek for extreme miniaturization and lays a foundation for the angle stability research of FSS structure working at millimeter band and even higher frequency band.At the same time,the proposed structure combines the characteristics of wide passband,wide stopband and sharp edge,which can be well applied to the antenna system in the extended band of 5G communication,and its comprehensive performance is better than the results reported.