| Nowadays, a more important way of the wireless communication system is miniaturization, ultra wide band and functional diversification. Therefore, antenna as a wireless transmission system essential basic parts, on the one hand were asked to bandwidth expansion, on the other hand, need makes it easy to carry and install, the traditional antenna design is generally by increasing the number of antennas to achieve the requirements of a plurality of frequency bands, antenna density continues to increase, which also leads to the serious electromagnetic interference coupling. Therefore, the form and the function of the traditional antenna has not kept up with system miniaturization, electromagnetic compatibility and other characteristics of the demand. In order to overcome this problem, the concept of reconfigurable antenna is introduced, application and development. The reconfigurable antenna is loaded through one or more pieces of antenna controller can be reconfigurable some performance in a certain range. Therefore, in the process of realization of reconfigurable antennas, the need for additional devices to control the current, such as MEMS (Micro-Electro-Mechanical System, micro mechanical system) switch, diode switch etc..RF MEMS switch as a switching device, rapid development in recent years, it and traditional FET (field effect transistor) switch and pin diode switch compared to its main advantages are:insertion loss is low, the isolation degree good, high linearity, low power consumption, microwave characteristics, small size and easy to integrated. In the civil field, it is an important control component of the reconfigurable antenna, which has a wide range of applications in the mobile phone and other mobile communication fields.Planar inverted F antenna (PIFA) is a kind of mobile phone with built-in antenna, because it has the advantages of small size, compact structure, low processing cost, simple production, low absorption rate, and it is widely used in the current mobile phone design. Tri band through a slotted PIFA antenna to realize multi band method has a lot of, is through the use of multi branch structure so that it can work in different frequency bands to achieve multi frequency, but the structure is complex, and a more effective way is through the main radiation face or on the floor, change the current distribution and the field distribution in order to achieve multi frequency effect; the existing literature is on the top floor patch slotted, PIFA antenna resonant characteristics, but its bandwidth is narrow, can not meet the actual communication bands, can satisfy the actual communication band, but in low frequency band, the antenna’s return loss is higher. Another method is the short pin can switch control in multiple locations loaded PIFA antenna, connected through one or more RF switch to produce a variety of possible combinations, but the antenna is higher in energy consumption.A novel based on RF MEMS switch three bands can be reconfigurable antenna, the antenna is used is in the formation of slotting method, compared to the other antenna using the top slot patch, slotted formation is relatively new and can increase the antenna bandwidth is presented in this paper. And antenna coaxial feed, its reconfigurability achieve by ohmic contact RF MEMS switch is connected or not connected to the part of the antenna structure, changing the physical length of the resonance loop antenna formation, to achieve the change of the resonance frequency. This antenna has three working modes, corresponding to 203,498 and 910MHz of the band, the relative bandwidth is respectively 18%,10% and 8%, can satisfy the actual demand of the communication frequency and gain. |
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