新型被動與主動式整合型天線之設計與應用

Abstract

本論文旨在研究與設計新型被動式與主動式整合型天線。首先將提出的是新設計的整合天線單元，稱為180度天線混合器︰此架構是以平衡式功率分配器為基礎，利用雙埠孔隙偶合微帶天線所具備之輻射電阻，來取代其中所需的平衡電阻。此電阻值可在不影響天線中心頻率的情況下，適當調整天線本身以及耦合孔隙的大小而達成所需大小。然後利用此設計製作出的整合型天線單元，我們將提出其實際上的應用，包括單平衡式混頻器、主動天線及雙輻射模天線陣列將被提出並製作量測其特性。其中單平衡式混頻器是利用混頻二極體直接接於天線混合器之平衡埠，射頻訊號由天線接收進來，而本地振盪訊號則從非平衡埠饋入。主動天線是運用回授的形式，回授路徑由非平衡埠與平衡埠的其中之一所形成，鎖頻訊號則可由另一平衡埠饋入。雙輻射模天線陣列是把180度混合器利用四分之三波長的傳輸線與另一孔隙偶合微帶天線以形成兩個單元的陣列，在如此架構下將分別於非平衡端的兩個埠得到同相及反相的輻射場型。 接著在論文中將介紹振盪器同步原理及耦合振盪器的基本原理。在此原理下，對於單一振盪器注入鎖頻的原理及各個振盪器間之耦合量對訊號相位所造成的影響將有詳細的描述與討論。根據這項基礎，我們將於論文中提出一個新的耦合振盪器理論，在此引進了另外不同機制的注入訊號，文中將探討在這兩個注入訊號同時影響下，偶合震盪器的特性及其對各單元間訊號相位的影響。 最後我們將提出回授式主動天線的設計與應用，這是利用雙槽耦合微帶天線之結構於回授振盪器設計時之回授路徑上，並配合其中放大器及相位調整之傳輸線，就可滿足振盪所需之增益及相位條件，以完成主動天線之設計。在本文中我們將使用兩種不同的傳輸線，一是微帶線，另一是共面波導，來完成設計，並將討論其特性的差異及製作時所需的考量。在應用上，兩組具有不同功能之主動天線陣列將於本論文中提出，一是切換式主動天線陣列，另一是兩個單元無相移器掃描式主動天線陣列。根據上述所提出之新的耦合振盪器理論，我們在這兩個應用的線路中，加入了內部耦合線路，此線路從第一個振盪器取出訊號經由放大器放大後再利用耦合器注入其他的振盪器中。經由切換放大器的狀態，天線陣列在此兩個不同注入訊號的影響下將分別產生同相的輻射場形及反相的輻射場形。此外，當方大器的偏壓是由關閉逐漸調整至全開時，在兩個單元的天線陣列中，其彼此間的饋入訊號相位將逐漸的由同相變成反相或逐漸由反相變成同相，而產生掃描的結果。

In this thesis, the new passive and active integrated antennas were proposed and implemented. First, a novel three-port passive antenna, named antenna hybrid, is designed and demonstrated. This structure is composed of a Wilkinson power divider with the isolation resistor replaced by an aperture-coupled patch antenna. The equivalent series impedance of the antenna can be adjusted to the required one by properly choosing the dimensions of the patch and the coupling aperture. The measurement results showed good agreement with the characteristics to be designed. Next, three applications for this integrated antenna have been proposed and demonstrated, that is, a balanced mixer, an active transmitting antenna, and a dual-radiation-mode antenna array. Secondly, several brand new active antennas and arrays are proposed and investigated. To explain the experimental results, the theory for the synchronization mechanism of oscillators is first studied. The behavior of an oscillator with an injection signal is investigated and the coupled oscillator theory is reviewed for understanding the phase variations between adjacent antennas. With the base of this fundamental theory, a new modified coupled oscillator theory for two-element active array, which discusses the effects when the two injection signals applied in the system simultaneously, will be proposed in this thesis. Next, the active microstrip antennas with feedback configuration were designed and measured. The feedback network was implemented using a two-port microstrip antenna fed and drawn by two capacitive loaded CPW’s or by aperture coupled microstrip lines. Finally, by using the results of the proposed modified coupled oscillator theory, an active microstrip antenna array with dual switching beams and a new phase shifterless beam-scanning technique were developed and demonstrated. The array contained several active antennas and an extra amplifier-embedded coupling (microstrip) line. Two injection-locking signals were used in the design, that is, the free-space mutual coupling between antennas and the injection signal on the coupling line tapped from the first oscillator in the array. By turning on and off the amplifier on the line, these two signals dominated in turn, producing two radiation modes with different main beams. A three-element H-plane array and a two-element E-plane array were designed and measured. As for the demonstration of the new phase shifterless technique, two-element active antenna array was used as an example. By mixing the effects of the signals from the control line and the mutual coupling, the phase difference between antennas is adjusted by gradually changing the amplifier bias on the control line. The measured results show that, when the control-line amplifier is biased from the off state to the fully on state, the radiation patterns for both arrays are varied smoothly from the difference pattern (with radiation phase difference) to the sum pattern (with phase difference). During the scanning process, the oscillators for each array are locked stably, with deviations of the oscillating frequencies lower than 0.35%