雙天線互偶對於輻射場及隔離度之影響分析

Abstract

隨著網路運用的多元複雜與頻寬需求的擴大，網路用戶對於無線傳輸的傳輸量需求也越來越高。 為處理與日俱增的網路需求，MIMO( multiple in multiple out )這樣的無線通訊系統也因應而生。由於MIMO系統的資料傳輸需要多個天線，同時作為傳送與接收訊號的媒介；然而天線之間也會因為彼此間相對位置而相互影響，尤其是天線之間所形成的輻射場型與彼此之間的隔離度，都會對天線的傳輸率造成影響。因而如何在產品設計之初就能很快速的預估相關的參數值，就變成當前重要的課題。 基於上述的需求考量，本論文於是針對於外接式choke sleeve天線，藉由感應電動勢法( the method of induced emf )建立互感的解析模型來進行迅速的估算；並利用HFSS來建立實體結構的模擬比對，以及實際量測的結果來交叉分析，以建立設計參數值的預估，期盼能提供無線工程師在日後作設計的最佳參考依據。 根據實驗的結果，利用感應電動勢法可以準確的估算兩天線之間的隔離度的值，但使用HFSS模擬分析的結果比較沒有參考性。就輻射場型的分佈分析而言，因為環境的影響使得量測值與模擬值因peak gain的角度而有所不同，但輻射場型分佈的趨勢是一樣。

Considering the increase of the network applications, varieties, and complexities, the more internet bandwidth and the capacity of wireless communication are getting more and more required by the internet users. To fulfill the above demands, MIMO (Multiple in Multiple out), the wireless communication technology, has been developed as one of the most important solutions. Since MIMO system requires multiple antennas to transmit and to receive wireless signals simultaneously, and the relative position of antennas resulting in different radiation patterns and the isolation will impact the transmission rate of the system, the ability to efficiently estimate the related wireless parameters at the beginning of the product design stage becomes a very important subject. This thesis focused on the external choke sleeve antenna. The induced emf method is employed to construct analytical model of mutual inductance to quickly come up with the estimation; it’s validity is verified by comparison with both the numerical data obtained by HFSS simulation and the experimental data. This analytical model is expected to provide a better data for RF engineers beforehand when doing the related design in the future. According to result the Induced EMF approach is able to precisely estimate the value of the isolation between 2 antennas. However, the result of the HFSS simulation is relatively weak for reference. In terms of the distribution analysis regarding the radio pattern, due to the environmental factors, the values obtained from the measurement and the simulation varied from the different angles of peak gain. However, the distribution trends of the radio patterns are consistent.