利用混合定律量測微波介電特性之研究

Study of Measurements of Microwave Dielectric Properties by the Mixture Rules

洪佐文(Zuo-Wen Hong)

指導教授 ： 沈自

國立虎尾科技大學/電機資訊學院/光電與材料科技研究所/碩士(2009年)

https://doi.org/10.6827/NFU.2009.00042

摘要

本篇論文將探討不同比例之陶瓷粉末分佈在聚乙烯物質中形成的複合材料(composite materials)之微波介電特性。使用之陶瓷材料為NPO-20M和NPO-37M兩種商業陶瓷粉末其介電常數值分別為20和36,而Q×f~50000(1GHz),使用之基質材料為PE粉末,其介電常數為2.32。

複合材料之製作程序為將一定比例之陶瓷粉末參雜於PE粉末中，並加入氧化鋯球與酒精一起置於塑膠罐內在球磨機上混合研磨。之後取出氧化鋯球再將混合物倒入燒杯中放到攪拌器攪拌然後於烘箱中烘乾酒精,烘乾之後再將混合粉末取出倒於設計好的鋼模內,再加熱壓模形成柱狀之介質共振器形狀。根據電磁理論,電磁波由一介質入射至介電係數不同的另一介質的時候,會因介電係數的改變而發生部份反射及部份穿透的情形,當介電常數遠大於最小單位時,電磁波大部分都會被限制在這範圍內形成駐波。以此原理可以形成我們所謂的介質共振器(DR)。微波介電性質之量測方法為利用柱狀共振技術(Post Resonance Technique),此量測技術對介電共振器材料在介電常數之量測上具有相當良好之準確度。

以NPO-20M和NPO-37M所製成之複合材料,其所量測之介電性質將與不同之混合定律的理論值來作一個分析比較,並將利用這些混合定理估計出100%純陶瓷材料的介電常數值。文章中亦將對現存之混合定律做一概略性的分析介紹,而不同混合定律的理論誤差也會再此作一個探討。並找出最適合的混合定律去估算純陶瓷粉末的介電常數。

除了介質共振器量測方法之外,由於微波介電共振器具有適當的介電係數、低溫度係數和低介電損失,使得微波介電共振器被廣泛的應用在微波通訊元件上。因此對於微波介電共振器與傳輸線之間的耦合等效電路的應用方面以及介電質振盪器的模擬亦將會作一個探討。

關鍵字

微波 ； 介電常數 ； 混合定律 ； 複合材料

並列摘要

This thesis will study the microwave dielectric properties of composite material, which is made by dispersed ceramic powders in polyethylene matrix material with various concentrations of composite materials. Two commercial ceramics powders of NPO-20M and NPO-37M with the dielectric constants of 20 and 36,respectively, and Q×f~50000(1GHz) are chosen. The matrix material is the PE powder and dielectric constant is 2.32.

Ceramic powder mixed in a certain proportion of PE powder with the ZrO2 ball and the alcohol is put in a plastic jar by ball milling. After taking out the ZrO2 ball and pouring the mixture into the beaker for mixer agitation, the powder is then dried in the oven to obtain the composite powder. The dried powder was the put in a cylindrical die with designed dimensions and the die was re-heated to form the shape of dielectric resonator.

According to electromagnetic theory, electromagnetic wave from a medium incidence to another dielectric with different dielectric constant because of the dielectric coefficient change, will have the partial reflection and the partial penetration situation. For dielectric constant much larger than unit, the majority of electromagnetic wave will be limited in the dielectric to form the standing wave. The so-called dielectric resonators (DR) in formed for measurements. The measurement method of microwave dielectric properties is the post resonance technique. This measurement technology has very good accuracy on the dielectric constant measurement in dielectric resonator material.

The measured dielectric properties of composite material will be compared with different mixture laws and those mixture laws will be used to estimate dielectric constant values of the 100% pure ceramic materials. The article also summarize for the existing mixture laws, discuss the theoretical error of various mixture laws, and discover suitably mixture rules to estimate the dielectric constant of pure ceramic powder.

In addition to the dielectric resonator measurement method, due to the appropriate dielectric coefficient, low temperature coefficient and low dielectric loss, dielectric resonators are also widely used in microwave communication components. Therefore, the coupling between microwave dielectric resonator and the transmission line equivalent circuit, as well as the application of dielectric oscillator for the simulation will also be studied in the thesis.

並列關鍵字

microwave ； dielectric constant ； mixture rules ； composites

參考文獻

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