| Summary: | 博士 === 國立臺灣大學 === 電信工程學研究所 === 102 === This dissertation presents a proximity-coupled microstrip EH1 mode array, a dual EH1 mode half-width microstrip antenna, and a differentially excited coupled half-width microstrip leaky EH1 mode antenna.
In the design of the proximity-coupled microstrip EH1 mode array, the radiation characteristics of the EH1 mode microstrip line with a length shorter than one free space wavelength are investigated and designed as an array element. The matched radiating-element load is also proposed to provide the wider bandwidth of input impedance matching and the back lobe suppression. Furthermore, the equivalent transmission line model of array element is reported to predict the radiation efficiency of the array. The measured results of the antenna gain and the radiation efficiency are 19.1 dBi and 87% at 10.525 GHz, and the measured maximum radiation efficiency is 91% at 10.325 GHz.
In the studies of dual EH1 mode half-width microstrip antenna design, the guided-wave structure support dual EH1 mode is proposed. A prototype design of dual EH1 mode antenna is also provided. The proposed guided-wave structure consists of two different half-width microstrip lines. Each half-width microstrip line supports an EH1 mode. The operation frequency of these two leaky modes can be designed independently. The isolation of two leaky modes is better than 20 dB over both leaky modes operation bands in simulated and measured results.
Finally, a differentially excited coupled half-width microstrip leaky EH1 mode antenna is presented. The guided-wave structure of coupled half-width microstrip lines are proposed and investigated, showing two leaky modes in the form of even- and odd-symmetry, respectively. Rigorous studies show that the odd-leaky-mode
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outperforms the even-mode approach in radiation patterns and bandwidth. Following the rigorous investigation of the modal characteristics of the coupled half-width EH1 mode guided structure, a differentially fed, coupled, odd-leaky-mode, half-width, antenna design of size 1λ0 by 3.6λ0 (including the feed) is reported, showing measured maximum antenna gain of 11.6 dBi, 15% fractional bandwidth, gain flatness of 2.4 dB variation, and input return loss greater than 10 dB.
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