本文主要著重於應用共振頻率方程式來設計一個雙頻平板天線，並藉由外加寄生元件來增加頻寛。設計雙頻平板天線的方法是根據 模態的共振頻率方程式，天線的饋入方式是採用銅軸線直接饋入，而饋入的位置為決定阻抗匹配最主要的因素，適當的調整饋入點位置進而得到所要的兩個共振頻率。其中一個實例是將兩個共振頻率靠近以得到較寛的頻寛。量測結果顯示 的10dB頻寛有104MHz，而且頻率在2.45GHz處 ，另一個實例是調整外加寄生元件的尺寸以得到寛頻且高增益的平板天線。針對雙頻平板天線並具有四個縮短尺寸的寄生元件所量測到的頻寛， 的10dB頻寛有132MHz 和108MHz 分別在頻率為1.8GHz 和2.4GHz 的頻段。相較於單一雙頻平板天線頻寛，在1.8GHz頻段，由35.9MHz 增加到 132MHz；在2.4GHz 頻段，由63MHz增加到108MHz。此方法非僅侷限於本文所提到的頻段，其它頻段亦可適用，前提為板厚遠小於介質中的波長。

In this paper, we apply the technology of resonant frequency equation to design a dual-band patch antenna and broaden the bandwidth by adding parasitic elements. The methodology of designing dual-broadband patch antenna is according to the equation of resonant frequency for the mode. The direct coaxial probe feed is adopted to mainly make the impedance match and then we deliberately adjust the feeding point to obtain two adjacent resonant frequencies. One case is to combine them together to broaden the required broadband. Measurement indicates that the bandwidth between -10dB is about 104MHz and =-28dB at 2.45GHz. The other case is to optimize multiple parasitical elements to reach dual wider bands and higher gain patch antennas. The measured bandwidths for dual-band patch antenna with four shortened parasitic elements, determined from 10 dB return loss, are about 132MHz and 108MHz in the 1.8GHz and 2.4GHz bands, respectively. Compared to single dual-band patch antenna the bandwidth is increased from 35.9MHz to 132MHz and 63MHz to 108MHz in the 1.8GHz and 2.4GHz bands, respectively. Our novel method is not only limited around the mentioned bands. It is also applicable to other bands under the condition that the thickness of substrate is far less than the wavelength in the substrate.

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