| In recent years, due to the development of larger capacity, multi-functions and intelligence communication systems, antenna as an indispensability part of communication systems is becoming broad in band, having multi-frequency and miniaturization. Microstrip antennas have been used in many fields for their inherent advantages, but the narrow bandwidths characteristics is its shortcoming. To keep up with time, it's necessary to study how to overcoming its demerit to get a multi-frequency broadband antenna.This dissertation mainly researches the multi-frequency and wideband microstrip antennas. Three multi-frequency and wideband microstrip antennas are proposed. Many technologies of them are discussed in theory, simulation and experiment.The first multi-frequency and wideband microstrip antennas is got by means of one patch multi-mode. It is feed from a coaxial feed probe with a capacitor patch. Today, microstrip antennas feeding from a coaxial feed probe with a capacitor patch are all thick in size, broad in band and usually single frequency and the shape of their radiation patch are usually rectangle. In this thesis,we reduced the thick of the antenna and got a cross slot on the rectangle radiation patch, a matched triple-frequency broadband microsrip antanna is obtained. The operation frequency bands with S11≤-10dB are 2.34-2.60GHz,3.79-3.88GHz and 4.93-6.16GHz.The second antenna is a dual-frequency and wideband microstrip antenna. It has similar configuration compared with the first one, but the shape of the radiation patch are different. With different slot on the rectangle radiation patch , one mode of the triple-frequency wideband antenna is restrained and a dual-frequency and wideband microstrip antenna is got. The operation frequency bands with S11≤-10dB are 2.38-2.52GH and 5.02-6.07GHz, successfully covered the 2.45 GHz (2400– 2484 MHz),5.2 GHz (5150–5350 MHz) and 5.8 GHz (5725–5825 MHz) band which WLAN needed.The third dual-frequency and wideband microstrip antenna is got by technique of planar multiple-resonator. But the antenna is different in configuration to a conventional coplanar multiresonator microstrip antenna, it is feed by a special way. This kind of configuration antenna has many merits, such as the two sub-antenna almost can design respectively, the antenna is broad in band, the proportion of the dual-frequency is easy to change and the antenna has similar impedance and radiation characteristic in the dual band.It is concluded from the research of this thesis that there are many potential to use microstrip antenna get multi-frequency and broadband antenna. |
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