Design of Ultra-wideband monopole antenna with WLAN band-notched and GPS circular polarization characteristics

• Main Authors: Che-Min Shao, 邵哲民
• Other Authors: Han-Nien Lin
• Format: Others
• Language: zh-TW
• Published: 2008
• Online Access: http://ndltd.ncl.edu.tw/handle/68290811033668786532

碩士 === 逢甲大學 === 通訊工程所 === 96 === In this thesis we proposed the use of a printed disk monopole antenna with coplanar waveguide (CPW) feeder for ultra-wideband (UWB) and global positioning system (GPS). The frequency band assigned for UWB system by FCC is between 3.1 to 10.6 GHz and this will cause interference to the existing wireless communication systems. For instance, the wireless local area network (WLAN) for IEEE 802.11a operating in 5.15–5.35 GHz and 5.725–5.825 GHz bands. Therefore a UWB antenna with a band-notch is required to overcome the interference. The antenna is constructed with the conventional radiating disk element that should benefit from the ease of manufacturing process and at the same time be cost effective. In addition, an annular stub is implemented to achieve circular polarization (CP) for GPS application at 1.575 GHz. The characteristics of axial ratio (AR) can be optimized by tuning the stub length and the stub-radiating element distance. As this design AR < 3 can be achieved for the frequency range from 1.55 to 1.58 GHz. By modifying the edges of the ground, the antenna is observed to provide an enhanced impedance bandwidth. The band-stop characteristic is realized by cutting an inverted U shaped slot on the radiating disk. The frequency of stop-band can be adjusted by changing the length and width of the inserted slot. The impedance bandwidth of the proposed antenna can range from 1.4 GHz to 11 GHz while the band rejection characteristic falls in the frequency band of 4.8 GHz to 5.98 GHz. Since the antenna presents a notched band from 4.8 to 5.98 GHz, it can prevent the RF interference from the wireless local area network (WLAN) as specified by IEEE 802.11a. This proposed antenna shows a monopole-like radiation pattern and good agreement has been obtained between the simulation and experiment results. Finally, a periodic structure is proposed. The characteristics of different periodic amount texture is studied. The back of antenna put the period of the surface texture is applied. The texture is put the back of monopole antenna with circular polarization, when the dimension of structure is large and the amount of the structure is less, the resonance of frequency is influenced, because the structure is the parasitic radiator. Contrary, when the dimension of structure is small and the amount of the structure is more, the resonance of frequency is higher, the of antennas are uninfluenced. This structure with the characteristics of high impedance surface, size reduction.