本論文研製一寬頻共平面波導饋入之圓形單偶極天線，天線結構主要由共平面波導傳輸線與圓形金屬片所組成，藉由在共平面波導傳輸線接地面上設計一類似散佈式匹配網路性質的漸進式接地金屬面結構，大幅提升天線的阻抗頻寬，並改善天線在無漸進式結構下高頻輻射場型不佳的問題，然而此項設計卻造成天線在低頻之cross-polarization增加。本文提出在漸進式接地金屬面上加入週期槽線結構，有效地改善天線在低頻操作時，高cross-polarization之缺點，並且使天線於高頻操作時，仍保有輻射場型之全指向性。此天線結構模擬與量測結果相當一致，在電壓駐波比 的條件下，操作頻帶可由810MHz至5.87GHz，阻抗頻寬高達151%，此頻帶涵蓋了GSM、DCS、PCS、PHS、3G、WLAN、WIFI及WiMAX等無線通訊頻段，在上述操作頻帶內的輻射場型皆有良好的全指向性。在結構上，此天線為單面結構，易於印刷製作，可應用於上述頻帶之無線通訊系統上。 A ultra-broadband, planar, circular monopole antenna (PCMA) fed by coplanar waveguide (CPW) structures is demonstrated. The CPW configuration permits easy integration with the uniplanar monolithic integrated circuits/monolithic microwave integrated circuits. Two modifications on the CPW ground plane are applied to improve the impedance bandwidth and radiation characteristics of the CPW-fed PCMA. First, the edges around the circular monopole are tapered to drastically increase the impedance bandwidth. Plus, the antenna gain is increased at the lower frequencies of the band. Second, the tapered edges are corrugated with rectangular gratings to significantly improve the radiation patterns, particularly at the frequencies around the higher band edge. The demonstrated CPW-fed PCMA features an over 151% VSWR=2 fractional bandwidth and satisfactory radiation characteristics over the whole band.
