| Summary: | 碩士 === 國立宜蘭大學 === 電子工程學系碩士班 === 103 === This thesis aims to design a multiband MIMO monopole antenna for LTE handset applications. The proposed planar monopole antenna printed on the PCB is composed of three quarter-wavelength resonators and a parasitic quarter-wavelength resonator shorted to the PCB ground plane. The three-resonators are fed by a semi-grid coaxial cable and one of them is designed for the GSM band. One of the main resonators is coupled to the shorted parasitic resonator in order to increase the operating lower band to cover the LTE-700 band. The main and the parasitic resonator are bent and limited in the area 10*60 mm to fit the antenna space occupied by a smart handphone. How to shrunk antenna space and achieve impedance matching between the main resonators and the shorted monopole is the design concern in chapter 3. The systematic parameter analysis and optimum matching are performed by a EM simulation tool, HFSS. The practical structure is also constructed and measurement is performed to verify the simulation results. Finally, the measured results confirms the multi-resonator monopole antenna has a multi-band and wide-band features ,making the mobile handset antenna can cover the LTE bands included in the 4G frequency bands (LTE 700、2300 and 2500 MHz). The proposed design is a kind of pure-planar antenna suitable for today's newly launched 4G mobile phone systems.
One of the main device-side requirements of the LTE-Advanced standard needs a Multiple input multiple output (MIMO) smart antenna. However, when the antenna space is shrunken, near-field coupling of the MIMO antenna in the lower LTE band leads to poor low frequency isolation conditions, We studied and raised a number of ways to remove the coupling between the MIMO antennas. In chapter 4, the coupling effects between the proposed monopole antennas are analyzed, especially in the lower LTE band. The MIMO antennas with high isolation and low envelope correlation coefficient are designed to achieve MIMO features. Our approaches make the designed 4G MIMO antenna can be operated in the LTE frequency bands (LTE 700、2300 and 2500 MHz) .The isolation is less than -15dB and the correlation coefficient is less than 0.5. These results reduce mutual interference between the antennas so that it allows users to quickly download or upload large amounts of data, which are the features of the high-speed wireless network.
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