| With the development of communication technology,mobile communication has also been evolved from the initial simple analog communication to the 4th generation communication which are integrating telephone,video and Internet,the required bandwidth is also increasing.The telephone antenna has also evolved from the original external whip antenna to a conformal built-in FPC antenna,the required frequency band has also been developed from a single band to a multi-band.The appearance of the cell phone is evolved from a plastic case to an all-metal back cover.When the cell phone uses an all-metal back cover,the traditional built-in antenna is no longer suitable,for the metal will shield the signal and cause the phone unable to work properly.In order to solve the problem of signal shielding and realizing large bandwidth,it is urgent to design a new type of mobile phone antenna which is suitable for practical applica tion to adapt to the development of mobile communication technology.Compared with the conventional mobile phone antenna,the slot antenna can realize the true antenna radiation by forming a mirror antenna through cutting the metal.In this paper,the slot antenna is studied in depth and the slot antenna is applied to the mobile phone from an engineering perspective,and the antenna bandwidth problem is solved by constructing a frequency reconfigurable antenna.The specific work content is as follows:First of all,the article outlines the development of mobile phone antennas and points out the difficulties in the design of mobile phone antennas at this stage,then describes the potential solutions of the slot antenna and the development in the domestic and overseas.Subsequently,the specific indicators of slot antenna and mobile phone antenna are discussed in detail,and the frequency bands and specific test methods used by mobile phones at this stage are introduced.Then,this paper presents a detailed simulation process of the slot-type all-metal back cover mobile phone antenna,and discusses the influence of the feeding mode and the different feeding point and ground feeding distribution on the antenna impedance,so as to select a suitable feeding mode fo r engineering application.Due to the hard metal characteristics of the metal back cover,it is inconvenient to engrave the groove on the metal or adjust it.Then,we study how to change the resonant frequency of the antenna by changing the feeding positio n to change the length of the gap,and investigate how the size of the gap of the antenna affects the bandwidth of the antenna.Finally,a multi-frequency slot antenna including GSM850,GSM1800 and GSM1900 bands and a slot GPS antenna are implemented.The test results meet the requirements of mobile phone.In the following,due to the limitation of the slot width,the bandwidth of the slot antenna is relatively narrow,and it is difficult to cover all the required mobile phone bands.This paper focuses on how to expand the bandwidth of the slot antenna,and provides the detail design of a frequency reconfigurable slot antenna.This paper constructs a reconfigurable antenna by introducing a tunable capacitor.The position of the tunable capacitor affects the change of the antenna frequency directly and the frequency coverage.We compared the effects of tuning matching impedance and reconfigurable antenna on antenna efficiency in detail.Finally,by combining the advantages of matching and reconfigurability,a full-band slot-type mobile phone antenna is realized. |
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