Research On Antenna Technology Of Multimode Mobile Terminal

As the evolution of the mobile communication technology, the coexistenceof2G/3G/LTE formats will become an inevitable trend. To meet the userroaming and the needs of the business, mobile terminal product needs tosupport multimode, multimode and multiband antenna. As the mobile terminalis limited in size, it must make the antenna be miniaturization, and enhancethe antenna integration. The antenna isolation has a major influence on thediversity gain of the whole MIMO communication system, when the isolationis bad, the diversity gain of system will be greatly reduced. So the highisolation,high integration,multimode and multiband antenna will become themain research direction of the future mobile terminal antenna. This papermainly studies the high isolation degree antenna and the high isolationmultiband.In the study of enhance the isolation degree of antenna, this paper putsforward the new type of plane fall F antenna structure, it makes that energycan't flow into the GND directly through the feed source or short wall byadopting non-contact capacitive feed and capacitive load, then it can reducecoupling of the multiple antenna. The antenna isolation is larger than25dB inthe operating frequency range, the envelope correlation coefficient is less than0.012, and it meets the requirement that the envelope correlation coefficientis less than the of0.5in the MIMO communication system. At the same timethe structure is a balanced structure, GND is no more a part of a antennasystem to participate in electromagnetic radiation compared with thenon-equilibrium structure of antenna, so the size of GND and other externalfactors have less impact on the antenna performance.On the basis of studying the planar inverted F antenna short circuit walllocation and width of the antenna resonant frequency fully, this paperproposing that it can realize frequency reconstruction by changing theposition of the short wall, the antenna structure is: to load multiple off state-controlled short-circuit wall on the single layer, and the side of therectangular microstrip antenna(it can realize on-off state by attaching switching devices controlled in the short-circuit walls), through the control ofshort-circuit wall switch device off state, to make one short-circuit wall beconnected and others be switched off at the same time, then the current on theradiation patch can flow into the GND. Current can flow into the GND byusing different methods by choosing different short-circuit wall to beconnected, so the antenna operating frequency will change with the change ofthe current path, and the antenna can work in a wide frequency range. Thenproduce the estimation formula of frequency and design methods of the shortwall reconfigurable antenna.