利用壓電超晶格極子之機械波與電磁波共生特性開發FM天線

Using the Symbiotic Property between Mechanical and Electromagnetic Wave in Piezoelectric Superlattice Polaritons to Develop FM Antenna

許展榮(Chan-Jung Hsu)

指導教授 ： 周元昉 ； 劉建豪

國立臺灣大學/工學院/機械工程學研究所/碩士(2017年)

https://doi.org/10.6342/NTU201704369

摘要

現今天線微型化之方式有非常多種，但基本上仍無法跳脫金屬天線尺寸上之限制。本研究以不同於往的天線材料來實現天線微型化目標。

週期性結構之特殊性質，使波在其中傳遞有通帶與禁帶。經由壓電之特性配合壓電係數週期性變化，形成的壓電超晶格中，馬克士威爾方程式與牛頓第二運動定律交互作用，此時電磁波與機械波於壓電材料中強烈耦合成共生狀態，此共生狀態之量子稱為極子，其電磁波特性可被空間中的電磁信號激發，而相對很短的機械波長使天線微小化成為可能。

因週期極化壓電晶體的極子具有接收與輻射電磁波之性質，所以首先使用電荷積分法製做針對107.7MHz之週期極化鈮酸鋰超晶格，在其上佈置特定方向之電極成為微型天線。量測此微型天線接收電磁能之能力與電極間距與電極面積之間關係。再與現有金屬天線進行比較，發現兩者接收效果不相上下，但週期極化鈮酸鋰晶體尺寸為金屬線長度的三十分之一以下，其天線微型化效果十分顯著。

並將PPLN應用於廣播收音上可發現，在使用相同古典音樂播放時，PPLN作為接收端天線時其SNR值為無使用時高出3.078dB，成功驗證PPLN具有接收電磁能之能力並且於實際應用上是相當可行的。

最終進行金屬天線與PPLN接收真實電台時之比較。傳統天線接收廣播時其SNR值為6.908dB，則為6.887dB。兩者SNR值相差甚少，證明PPLN是不只成功將天線微小化外亦極具商用化之潛力。

關鍵字

壓電超晶格 ； 極子 ； 天線微型化 ； 調頻廣播天線

並列摘要

Nowadays there are many ways to miniaturize the antenna, but basically still can not escape the metal antenna size restrictions. In this research, we use different antenna material which had never be tried before to achieve to miniaturize the antenna.

Through the characteristics of the piezoelectric with the periodic changes in structure causes the mutual effect between the electromagnetic governing equation and Newton's second law of motion to interact with each other to make it strongly couple electromagnetic waves and mechanical waves in the piezoelectric material to become symbiotic state. In this state the electromagnetic property of polariton can be excited by electromagnetic signal in the air and relative small wavelength of mechanical wave make antenna miniaturization possible.

Since the poles of the periodically poled piezoelectric crystal have the properties of receiving and radiating electromagnetic waves, using charge integral method to fabricate the periodically poled lithium niobate superlattice for 107.7 MHz, and electrodes arranged in a specific direction thereon are formed as micro antennas , the measurement of this antenna to receive electromagnetic waves and the ability to compare with the metal antenna, the results found that the two received the same results, but the size of lithium niobate crystal is less than one third of the length of the wire. Antenna miniaturization of the effect is very significant, its future development worthy of in-depth discussion.

Applying PPLN to the radio can be found when we use of the same classical music, SNR value of PPLN as a receiver is 3.078dB higher than when not using PPLN. It has the ability to receive electromagnetic energy and in practical applications is quite feasible.

The final comparison receive the real radio station singal between the metal antenna and PPLN. When receiving the broadcast singal, SNR value of the metal antenna is 6.908 dB and is 6.887 dB. The small difference between the two values proves that PPLN is not only the successful miniaturization of the antenna but also the potential of commercialization.

並列關鍵字

piezoelectric superlattice ； polartion ； antenna miniaturization ； FM antenna

參考文獻

[39] 鄒嘉威, “週期極化鈮酸鋰之電磁波輻射與接收研究”, 碩士論文, 國立臺灣大學機械工程學研究所, 2013

[41] L. Brillouin, “Wave Propagation in Periodic Structures”, 2nd ed., International Business Machines, New Yok, 1953.

[43] 崔育銘, “壓電超晶格極子之電磁輻射與接收特性研究”, 碩士論文, 國立臺灣大學機械工程學研究所, 2015

[1] H. a. Wheeler, “Fundamental Limitations of Small Antennas,” Proc. IRE, vol. 35, no. 12, pp. 1479–1484, 1947.

[2] L. J. Chu, “Physical limitations of omni-directional antennas,” J. Appl. Phys., vol. 19, no. 12, pp. 1163–1175, 1948.