Research On Antenna Technology And Small-Size Filters In Special Communication Applitication Evironments

Special communication, widely different from business communication, highlight following characteristics:(1) higher transmitting power or larger power consumption, is tens or hundreds of that of business communication;(2) faster signal fading, and often last a longer time communication breakdown;(3) one or two of parties moving at a supersonic speed;(4) long distance com-munication, up to several thousand even tens of thousands of kilometres;(5) complicated technology of signal processing and extraction. Then, propagating environment equipped with one of communication characteristics above is so-called special communicaiton application environment. It’s necessary to think over the critical tech of special communication such as selecting signal source of special communication application environments, improving special propa-gation environment to communication signals as much as possible and how to design and optimize miniaturization filters in special communication system. This article make a more thorough research mainly aiming at the antenna tech-nology of special communication application environments and critical tech of small-size filters. On the basis of EM theory and finite element method, the near field gain of special communication antenna and tunable gain of super-Gaussian beam, propagating properties of EM wave from microstrip antenna through special communication application environments, and the design and optimization of small-size filters are analyzed.Above all, the super-Gaussian distribution as a signal source of circular aperture antenna in special communication application environments is pro-posed. Combining with Huygens-Fresnel principle, the properties of radiation and gain in near field for different orders super-Gaussian beam distribution are discussed, and a closed-form solution is obtained, under the conditions of focusing and unfocusing. Moreover, the effects of different proportion of an- tenna radius and super-Gaussian beams on aperture efficiency, near field gains and radiation properties are analyzed, under the focusing cases. Simulation re-sults show the abilities of anti-fading from super-Gaussian beams are superior to those of Gaussian beams, so if switching to different order beams, the gains of antenna can be tune.Secondly, the principle and method on how to tune the resonant frequen-cy of microstrip antenna is proposed in special communication application environment——an anisotropic dielectric slab and a layer plasma. Depend-ing on SO-FDTD method, the impedance, the resonating frequency and the return loss of EM wave in special communication application environments are discussed, simulation results show the effect of dielectric constant of an anisotropic slab on antenna resonant frequency is counter to that of plasma fre-quency. So if selecting proper dielectric constant of an anisotropic slab resting on plasma frequency, the gains of antennas can be tuned in special communi-cation application environments.Lastly, the complement split ring resonator (CSRR) applying in dual mode filters on the circular or square patch are proposed, specific parameters are giv-en. Adjusting proper placement of CSRR structure, it can act as a splitter of modes, and sperate from two different resonant frequent modes. So, CSRR will help to improve bandpass performance, enhance abilities of frequency se-lecting and fine-tuning central frequency. On the other hand, selecting proper width and length lying in two sides of the feeding lines will substantially adjust central frequency of filters, it has a broad application in special communica-tion application environments. In addition, this kind of filter has a small size, compact and can be easily integrated with other elements.