| The rapid evolution of wireless communication technique has well promoted the update speed of communication product.The wireless devices with small-volume,light-weight and more functions are becoming more and more attractive.As an important part of the wireless communication systems,the design of antenna is developing towards miniaturization,broad-band and multi-band.It is a challenge for designers to design a compact antenna with multiple functions.Microstrip antennas have the merits of small-volume,light-weight,simple-structure,easy to be fabricated and integrated with microwave integrated circuits.It has become a very popular topic in antenna designs.This dissertation makes a research on the analysis and design of miniaturized microstrip antennas.Based on the development trend of miniaturization,broad-band and multi-band microstrip antenna,three kinds of microstrip antennas are designed,which are used in wireless local area network(WLAN),WLAN/WiMAX USB adapter and ultra wideband system(UWB).In the first design,a novel printed 2.4/5-GHz double-band G-shaped monopole antenna for WLAN applications is presented.The radiating element of the proposed antenna is composed of a circular patch and a pair of G-shaped branches.It has the advantages of compact,simple structure and easy to be fabricated.The results simulated by CST and HFSS both show that the proposed antenna can entirely cover the WLAN standards of the IEEE 802.11a/b/g/n in the 2.4GHz(2400-2484MHz),5.2GHz(5150-5350MHz),5.8GHz(5725-5825MHz)bands and the radiation patterns are nearly omni-directional.In the second design,a novel 2.4/3.5/5.5-GHz triple-band monopole meander-line slot antenna for wireless universal serial bus(USB)applications is presented.The planar antenna is simply comprised of two meander-line monopole slots.Being different from the traditional slot antenna,this antenna is operating at a quarter-wavelength mode,and the actual size occupied by the developed antenna is only 17×15×1 mm3,meeting the requirement of the development trend of miniaturization.The measured and simulated results show that the antenna can entirely cover the 2.4/3.5/5-GHz WLAN/WiMAX frequency bands with good radiation characteristics.Lastly,an asymmetric rectangular ring monopole antenna for UWB applications is presented.The radiating element of the proposed antenna is composed of a notched rectangular ring patch and the impedance matching effect at high frequency can be improved through the toothed edges of the rectangular ring patch.On this basis,by leading into a U-shaped slot,a compact UWB antenna with a band-notched characteristic in 5-GHz can be achieved.The results simulated by CST and HFSS have a great agreement,which show that the proposed antenna can entirely cover the UWB band with omni-directional radiation characteristics. |
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