| With the constant improvement of varieties of communication technology, the processing technology becomes mature gradually.The development direction of mobile terminals have tended to be more beautiful, thinner, more multi-functional and intelligent,Antenna is the key signal conversion device, which also changed a lot with the development of the terminal. Built-in, miniaturization, multiple frequency, low profile, small volume, light weight is the feature of Micro-strip antenna.And it can be designed into variety of structures to achieve the same function.Based on the analysis of antenna radiation and design theory, this paper shows a tree micro-strip antenna that can work in multiple frequency bands at the same time. By the high frequency electromagnetic simulation software(HFSS) and vector network analyzer, the tree micro-strip antenna is studied from the theoretical and experimental work. The main work is as follows:Firstly, the theory of micro-strip antenna is analyzed and summarized, including the radiation mechanism of micro-strip antenna, feeding method and the calculation of radiation field; This paper also Introduced some methods and skills of antenna design, analysis and simulation in HFSS; what’s more, the antenna miniaturization,multi-frequency technology are emphatically introduced, and the advantages and disadvantages of various technologies are summarized respectively.Secondly, based on the antenna radiation and design theory, multiple frequency tree micro-strip antenna is designed. Changing the antenna structure, increase or decrease the length of antenna patch all can affect the antenna performance parameters. When microwave photonic crystal structure is used in micro-strip antenna,this kind of special structure has a big influence on antenna surface wave, gain and directivity.In this paper, the third chapter proposed a tree multiple band antenna. By changing the length and shape of the antenna, making the patch E1 bent to connect to the patch R2, the impedance bandwidth of the antenna increases, it can work on 2G and 3G communication system except for original 4G and WLAN. The antenna returnloss is diminished at resonant frequency, which also moved to the left about 100 MHz,so the impedance bandwidth of the antenna is covering 2G system DCS1800 portion spectrum. The fourth chapter introduced microwave photonic crystals. On the floor of the antenna, there are periodic round holes, it is analyzed that the influence of EBG structure parameters on the antenna characteristics. When r0 = 1.2 mm, d = 2.2 mm,the antenna performance is the best. At 1.8 GHz, gain increased 1.062dB; at 1.9GHz,gain of the antenna is 1.153 dB, increased by 70.82%; at 2GHz point, the rate of gain increase arrives at 81.58%; the gain growth of antenna is more than 1 dB from 2.4GHz to 2.7 GHz; at higher frequency bands of WLAN, antenna gain also have increased by various degrees. Among them the 2.6GHz is the most influenced, gain increase rate is reaching 105%.Finally, this paper shows the physical antenna which are made and produced by software Altium Designer. And it has been tested in microwave dark room by the vector network analyzer. The antenna measurement characteristic parameters including direction diagram, gain and return loss are compared with simulation results.It shows that they are in good agreement on the over all trend, although,there are some differences in the range of allowable error, and the paper gives the corresponding analysis and interpretation. Eventually, the antenna size reduced a half after optimization, antenna property is promoted. Importantly, it realized miniaturization and multiple band characteristics so that can be completely cover the band of 2G, 3G, 4G and wireless local area network(WLAN) and the global Internet microwave access(WiMAX) communication system. The antenna can be applied in the 4G mobile communication terminal. |
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