分散式回授天線振盪器

Abstract

本論文提出一個新的主動發射天線陣列設計，名為 "分散式回授天線振盪器" 。此陣列由幾個單元串接形成一個封閉迴路。每個單元由一個放大器及一個雙埠天線組成且產生大於 0dB 的注入增益及 360°整數倍的角度延遲。在每個單元迴路中，訊號被放大且輻射出去，從所有天線輻射出去的場可在空間中同相加成。利用雙埠隙孔耦合微帶天線，我們設計並製作了一個兩單元及一個四單元的 10GHz天線振盪器。模擬結果發現有多個振盪模可在天線振盪器中被激發。每一振盪模具有不同的振盪頻率與不同的輻射波束。於實驗中，可藉由調振盪器的偏壓建立每個振盪模。並且，量測到的輻射場型與預期的相當吻合。為了使振盪器只出現一個振盪模，我們設計了一種簡單的帶拒濾波器來抑制不要的的振盪模。研究偏壓條件對單一振盪模的振盪頻率及輻射功率的結果發現，對不同偏壓，兩單元及四單元振盪器振盪頻率的偏移分別在 0.7% 及 0.2% 之內。並且，從兩單元到四單元的功率合成效率為 95%。最後，我們也對這兩個天線振盪器的注入鎖定頻寬作研究，而從中獲得振盪器之品質因素。

In this thesis, a new design of the active transmitting antenna array, named distributed feedback antenna oscillator, is proposed. The active array is formed by serially connecting several unit cells to a close loop. Each unit cell contains an amplifier and a two-port antenna, with an overall insertion gain larger than 0 dB and a phase delay equal to a multiple of . The signal travelling on the loop is amplified and radiated in each unit cell. The radiation fields from all the antennas are then combined in free space. A two-element and a four-element feedback antenna oscillators operating at 10 GHz are demonstrated by using two-port aperture-coupled microstrip antennas. Simulation results show that multiple oscillation modes with different frequencies and different radiation beams may be excited in the antenna oscillator. By experiment, it is found that each oscillation mode can be built by tuning the biases of the oscillator. The measured radiation pattern for each mode agrees very well with the predicted one. For a single mode operation with a broadside pattern, bandstop filters of a simple geometry are designed and embedded in the oscillators to suppress the unwanted oscillation modes. The influence of the bias condition on the oscillating frequency and the radiation power of the single-mode oscillators is investigated. The results show that, the frequency deviation at different biases is under 0.7% for the two-element oscillator and is under 0.2% for the four-element one. Also, the power-combining efficiency from two-element arrays to a four-element one is measured as 95%. Finally, the injection-locking bandwidths of the two oscillators are studied, from which the external Q-factors are obtained.