具高頻帶邊緣選擇之小型濾波天線

Abstract

本論文旨在研究具有高頻帶邊緣選擇之新型縮小化濾波天線，包含超寬頻天線以及高整合度模組兩方面的應用。研究所提出的天線設計，均具備結構簡單、製作與積體化容易、成本低廉，以及展現良好的濾波器響應。 首先,提出兩種小型的耦合共振器。所設計之新型耦合線共振器，其在濾波天線中可產生一對可調整頻率的傳輸零點。此外，耦合開路/短路殘斷共振器在具有頻帶截止功能之超寬頻天線設計中，呈獻一個傳輸零點於中心頻率以及一對可調整頻率的傳輸極點於帶通頻段。所設計的兩種共振器皆可達到高裙帶選擇於頻帶轉換區域。 再者，亦提出多種新型印刷式濾波天線之合成與設計。首先將建立倒L型與倒F型天線之等效電路模型，其主要為串聯RLC共振型電路，並利用與全波模擬結果比較，進行天線之等效電路成分萃取。此兩種天線在本研究除了當做主要輻射體，亦是帶通濾波器中最後一階共振器。為了達到有效整合與簡單設計之要求，提出共同設計之方法來整合濾波器與天線。首先以印刷式倒L型天線與平行耦合微帶線為例，設計與合成一帶通濾波天線。接著提出具有高頻帶邊緣選擇之印刷式濾波天線，其使用與傳統天線相同電路基板面積。所提出的架構不僅是一個輻射體，亦是一個二階帶通濾波器，其中濾波器的一階由天線提供，而另一階由耦合線共振器提供。透過耦合線共振器之設計，在截止頻帶可產生兩個可調的傳輸零點，可達到高頻帶邊緣選擇。而為了縮小電路面積與寄生的輻射效應，提出縮小化耦合線共振器，其利用微帶線、共平面波導之結構與側面耦合之方法來實現，並嵌入於□型與倒F型天線面積中。根據濾波器的規格，詳細提出濾波天線的設計步驟。以操作頻率為2.45GHz且具0.1 dB 等漣波響應之柴比雪夫濾波器為例子來設計濾波天線。與單一天線做比較，所提出之濾波天線除了具有與單一天線近似的天線增益外，亦呈獻較佳的天線增益頻帶邊緣選擇及平緩天線增益響應於帶通頻段。所量測之結果與設計的做比較，包括折反損耗、全輻射功率、及天線增益對頻率之響應，具有良好的一致性。 最後，提出高截止頻帶邊緣選擇之具頻帶截止功能的超寬頻天線設計。所提出的天線包含一個輻射貼片與嵌入式二階帶拒濾波器.使用與典型UWB天線相同的電路基板面積，將非均勻式短路殘斷與耦合開路/短路殘斷共振器所組成之帶拒濾波器設計於傳統天線中。以操作頻率為5.5GHz且具最大平坦響應之帶拒濾波器為規格，對於所設計之天線提出詳細的設計步驟。與傳統的天線比較，所提出的UWB天線在頻段5.15GHz與5.95GHz之間具有良好的截止頻帶抑制，其中在截止頻帶中的規一化全輻射功率為-12dB。所提出之架構可達到高頻帶邊緣選擇與平坦的折返損耗於截止頻帶中。所量測之結果與設計的做比較，包括折返損耗、全輻射功率、天線增益，具有良好的一致性。

This dissertation is focused on the design of the novel compact filtering antennas with high band-edge selectivity. These antenna designs have the merits of simple in geometry, easy for manufacture and integration, low-cost, and exhibits good filter frequency responses. First, two kinds of compact coupled resonators are proposed. The new coupled line resonator in the filtering antenna can provide one pair of transmission zeros with tunable frequencies. Also, the coupled open-/short-circuited stub resonator in the band-notched UWB monopole antenna can exhibit a transmission zero at the center frequency and a pair of transmission poles with tunable frequencies at the two sides. Both of these two resonators can achieve high skirt selectivity in the band transition region. Secondly, the synthesis and design of the new printed filtering antennas are presented. The equivalent circuit models for the inverted-L and -F antennas, which are mainly a series RLC circuit, are first established. The values of the corresponding circuit components are then extracted by comparing with the full-wave simulation results. These two antennas here perform not only a radiator but also the last resonator of the bandpass filter. For the requirements of efficient integration and simple fabrication, the co-design approach for the integration of filter and antenna is introduced. The printed inverted-L antenna and the parallel coupled microstrip line sections are first used for example to illustrate the synthesis of a bandpass filtering antenna. Moreover, the compact printed filtering antennas with high band-edge gain selectivity are presented simultaneously. Occupying about the same substrate area as a conventional antenna, the proposed structure not only serves as a radiator but also a second-order bandpass filter, with one filter pole provided by a antenna and the other by a the proposed coupled line resonator. High band-edge selectivity is achieved due to two additional stop-band transmission zeros provided by the coupled line resonator. To minimize the required area and reduce the spurious radiation, a coupled line structure composed of a microstrip line and a coplanar waveguide by broadside coupling is adopted and intruded into the □-shaped and inverted- F antenna areas. The design procedures are given, which clearly indicates the steps from the filter specifications to the implementation. The measured results, including the return loss, total radiated power, and radiation gain versus frequency, agree well with the designed ones. As compared to the conventional antennas, the proposed filtering antennas not only possesses a similar antenna gain but also provides better band-edge gain selectivity and flat passband gain response. The measured results, including the S-parameters, total radiated power, and antenna gains versus frequency, have good agreement with the designed ones. Finally, a novel design of band-notched ultra-wide-band (UWB) monopole antenna with high notch-band-edge selectivity is proposed. The proposed antenna consists of a radiation patch and an embedded second-order bandstop filter. Using the same substrate area as a fundamental UWB antenna, a bandstop filter composed of a non-uniform short-circuited stub and coupled open-/short-circuited stub resonators, is designed into the fundamental antenna. A detail design procedure for the proposed antenna with a second-order Maxially-flat bandstop filter at 5.5 GHz is presented. As compared to the fundamental antenna, the proposed UWB antenna provides good notch-band suppression from 5.15 GHz to 5.95 GHz in which the normalized total radiated powers in the notch-band are lower than -12 dB. Also, the proposed structure provides high band-edge selectivity and flat return loss in the notch-band. The measured results agree with the designed ones.