將可調元件加入窄頻天線中，可使其操作頻率變為可調，藉此增加天線之有效頻寬。本論文將鐵電可變電容負載於微帶貼片天線上，以期達到操作頻率可調之效果。
在本論文中，我們設計了一操作Ku頻帶的可調微帶貼片天線。我們將八個鐵電可變電容以等間距分別負載於微帶貼片天線的兩個輻射槽孔；設計流程於論文中描述。模擬結果顯示，當鐵電可變電容由0.25 pF調至0.1 pF時，天線之操作頻率會由14.5 GHz變化至18 GHz，可調頻率範圍為21.9%。在可調頻率範圍內，最大天線增益為−2.38 dBi。本天線以微帶線直接饋入訊號。考慮量測時的需求，我們設計了兩種轉接型式－下探針型式與鎖接頭型式；兩種型式之模擬結果相近，僅鎖接頭型式之最大天線增益稍低，為−2.76 dBi。
我們使用本實驗室發展之製程製作所提出之可調微帶貼片天線。量測結果顯示天線之操作頻率有偏移的現象；於0 V偏壓下，由14.5 GHz下降至12.5 GHz。頻率往低頻偏的原因為矽基板貫孔製程時發生過蝕刻，導致寄生電容增加。此外，我們發現天線操作頻率並無法隨偏壓而移動，這我們目前尚未能找出原因。未來將須改善蝕刻製程的穩定度、提升良率，以成功製作出此頻率可調之天線。

Incorporating tuning elements into a narrowband antennas makes its operating frequency become tunable, thus increases its effective bandwidth. In this thesis, a microstrip patch antenna is loaded with ferroelectric varactors to achieve frequency agility.
In this thesis, a Ku-band tunable microstrip patch antenna is designed. The patch antenna is loaded at its two radiating slots with 8 ferroelectric varactors. The varactors are equally spaced. The design procedure is described. Simulation results show that, when the capacitance of the ferroelectric varactors changes from 0.25 pF to 0.1 pF, the operating frequency of the patch antenna would vary from 14.5 GHz to 18 GHz, corresponding to a 21.9% frequency tuning range. Within the frequency tuning range, the maximum antenna gain is −2.38 dBi. The patch antenna employs a direct microstrip feed. For measurement, we design two types of transition – probing and connectorized. Both transition types exhibit similar simulation results, except that the maximum antenna gain of the connectorized type is slightly lower, which is −2.76 dBi.
The proposed tunable microstrip patch antenna is fabricated using a fabrication process developed by our lab. Measurement results show that, under 0-V bias, the operating frequency of the antenna is shifted down to 12.5 GHz from the originally expected 14.5 GHz. The reason for the frequency shift is because the increase of parasitic capacitance due to the over-etching when making the through silicon vias. Besides, it is found that the operating frequency cannot be adjusted by the bias voltage of the varactors. Unfortunately, we have not found the reason that leads to this failure. In the future, to successfully fabricate the proposed tunable antenna, the stability of the etching processes and the yield must be improved.

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