本研究以全平面式的結構與直接饋入的方式來設計天線，使其與基板較易整合，採用厚0.8mm的FR4基板，以相對介電係數(Relative Permittivity)為4.4，Dielectric Loss Tangent為0.02，來進行模擬並和實驗相驗證，設計兩種雙頻天線架構，其涵蓋應用範圍包括PCS/WCDMA1900、PHS、TDS-CDMA、WCDMA/IMT-2000、WLAN(802.11a)和WLAN(802.11-a/b/g/n)。
With the rapid development of wireless communication technology, applications of various wireless communication are wide spread. For those communication systems to be compatible with multiple standards, dual and/or multi-frequency antennas are continuously increasing in demand. The traditional multi-frequency antennas usually require multi-path architecture and/or slit design, which tend likely to occupy a relatively large volume.
In this study, uni-planar structure with a coaxial feed is utilized to design the antennas so that it is easy to integrate with the PCB. The FR4 substrate with thickness 0.8mm is used, while the relative dielectric constant of 4.4 and loss tangent of 0.02 is used for simulation. Experiments are conducted to verify the design of the dual-band antenna structures that cover the frequency bands of PCS/WCDMA1900, PHS, TDS-CDMA, WCDMA/IMT-2000, WLAN (802.11a) and WLAN (802.11-a/b/g/n), etc.
At first , the planar quarter-wavelength monopole antenna serves as an initial structure studied in this thesis. In order to reduce the antenna size, we compare the characteristics of the inverted L antenna and the inverted F antenna, and then examine the π-shape antenna, which can be viewed as resulted from two inverted F antenna with back to back, and to explore the characteristics of π-type antenna to overcome the narrowband shortcoming of the inverted F antenna. In addition to the bandwidth-broadening in the low-frequency band, we further introduce parasitic elements to achieve the a dual-band WLAN antenna design. Finally, try to reduce the size of the new design.
Several antenna prototypes are fabricated, while the measurement results show very good agreement with the simulation. As the bandwidth concerned the low-frequency (WCDMA/IMT-2000) bandwidth is increased from 8.78% to 21.11%, while the high-frequency WLAN bandwidth is increased from 9.27% to 17.15%. For the radiation patterns, experimental results show that the H-plane (XZ-plane) reveals a omni-directional characteristics at various frequencies.