| Summary: | 碩士 === 國立交通大學 === 電信工程系 === 89 === The thesis aims at developing an innovative dual-band antenna structure with simple fabrication and excellent performances, named “ dual-band notch antenna.” Major port of dual-band applications in antenna design is based on the extensions of patch antenna. The merits of applying patch antennas to dual-band applications include promoting or lowering the frequency ratio for specific utilizations, enhancing impedance bandwidth and miniaturizing dimensions. However, utilizing patch antenna as a basis of dual-band antennas involves complexities in feedline network and fabrication. The goal of designing dual-band antennas in this thesis is is exploring a innovative scheme to design dual-band antennas, instead of utilizing patch antennas as a basis. Simple fabrication, wide-band, miniaturization, flexible frequency ratios and potential to design diversity antennas are all the main advantages and emphases in this thesis.
A sequential approach is adopted to investigate notch antenna. Two kinds of feeding structure are presented in this thesis. The first one is microstrip-slotline transition. The other one proposed to upgrade the fabrications is cpw-slotline counterpart.。 Turning slotline with right angle for miniaturization produces two distinct resonant frequencies. It merely has about 3% in impedance bandwidth of proposed dual-band notch antennas at the first resonant frequency. Two creative wide-band, dual-band antennas are proposed to solve the problem of narrow bandwidth. The first one wide-band geometry utilizes power divider to excite 2-in-1 notch antenna set simultaneously. Combining the two adjacent resonant frequencies to extend bandwidth significantly promote the impedance bandwidth to 43%. The second wide-band one employ the inherent characteristic of slotline and successfully enhance impedance bandwidth to over 30% without applying larger dimension.
Notch antenna has excellent EMI immunity than other types of antennas. Taking two notch antennas closer or even combining them into a single one causes low correlation between them. Therefore, employing notch antennas to design a compact diverity antenna is suitable. Designing notch divesity antnna Applying two pin diodes to switch two different notch antennas are presented in the thesis when designing notch diversity antenna.
Detailed discussions on design rules and principals of dual-band notch antennas are reported in the thesis. Additionally, wide-band geometries are addressed also. Notch antenna has many advantages over patch antenna. Providing thorough comparisons and analyses on some characteristics of notch antenna and inducing some continuous works and possible applications by utilizing notch antennas in the conclusion of thesis.
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