Abstract
本論文主要利用諧波平衡(Harmonic Balance)的方法製作一模擬程式研究整流天線(Rectenna)的效率,並推導出新的封閉式(Close Form)表示出DC轉換效率的相依關係,利用此一簡單的封閉式輔助設計整流天線的電路,當中,此封閉式與前者諧波平衡的結果比較,兩者的百分比差只在百分之四以內。在此封閉式推導中,先對於在二級體上的電壓信號頻譜假設只存在直流及基本頻率的分量而推導,對於一般高頻率操作下,電壓頻譜的高次諧波項常可以忽略,這是由於其後所接的低通濾波器以及二級體內部本身所含的非線性電容有效地短路了高頻率諧波而使這個假設能夠適用。利用製作好的程式,對於整流天線的系統參數,溫度、負載電阻、輸入阻抗、二極體參數...等,進行分析,溫度幾乎與效率無關,而負載電阻影響並不大,主要在於輸入阻抗的匹配,而輸入阻抗主要與二級體內部接觸電阻大小與非線性電容與本質二級體有關。之後,研究發現DC 轉換效率的可以將主要二級體電路分為輸入與輸出網路,簡單計算輸入功率轉換的效率並輔以本論文推導出的封閉式,可以將原本複雜的DC 轉換效率的計算化成簡單的計算,同時在計算當中了解限制整流天線的最大轉換效率主要來自輸入功率轉換至內部本質二極體(intrinsic diode)由本身二極體的非線性電容所限制的原因,此外,二級體內部的接觸電阻與本質二級體串聯消耗了固定比例的輸入功率而使得整個的直流轉換效率降低。對於設計一個高效率的整流天線,受限於二級體的限制,設計主要的目標在於如何將最大的高頻信號功率傳送到內部真正有整流功能的本質二級體上,也就是說,對於輸入端的電路要加以匹配,而輸出端的匹配的效應研究結果顯示僅是次要的。A program was implemented by harmonic balance algorithm toanalyze the DC conversion efficiency of the rectenna system. Inaddition to the numerical simulation, an accurate close formanalytical expression for the DC conversion efficiency has alsobeen derived. The accuracy of this close form analyticalsolution is further conformed by the excellen agreement withthe prediction from the harmonic balance analysis. The maximumerror falls within 4% and. the error even reduces around 1%range in the high power level region. The effect on the variouscircuit's parameters were studied by the harmonic balanceprogram. The temperature is nearly independent on the DCconversion efficiency. The maximum reachable DC conversionefficiency is limited by the diode's series resistance as wellas the nonlinear capacitance. The series resistance dissipatesa fixed percentage of input power fed into a diode. Thenonlinear capacitance lower the active power on the inherentidea diode which dominate for the generation of the DC power.