本論文提出一款應用在無線射頻辨識系統(Radio Frequency Identification, RFID)讀取器的圓極化微帶天線。由於RFID的應用情境為較複雜的電磁傳播環境，且讀取器的設置場所及標籤擺放的位置方向並非固定，故使用圓極化天線以排除標籤天線極化方向的影響，可增加標籤的讀取率。本設計結合應用在RFID讀取器的相控陣列天線系統，以合成不同方向的圓極化波束來對環境進行掃描與標籤讀取。
第二部分為改善先前研究中所提出的天線匹配量測系統在反射係數大小低於-10 dB時的準確度問題。我們提出一個以180度相移器搭配訊號處理的方法，來校正量測系統中的誤差項，使系統量測的結果與實際利用向量網路分析儀量測的結果更加吻合，並討論可能造成誤差的原因。
第三部分為提出一個可量測傳輸係數的系統。此量測系統可分為兩個部分，一部分為微波元件模組，包含射頻訊號源、方向耦合器、180度分合波器及兩個射頻能量偵測器，另一部分為訊號處理演算法。本研究所提出的量測系統可估計出待測物的傳輸係數大小及相位，且不需要使用到向量網路分析儀。

In this thesis, a circularly polarized antenna, which is applicable to radio frequency identification (RFID), is proposed. The environment of the RFID application is complicated. In general, readers and tags are not set in fixed locations. Thus a circularly polarized reader antenna can be used to avoid tag orientation issues, and hence increase the RFID read rate. The design is integrated with a phased array system to provide a scanning beam that cover a broader area.
In the second part, we attempted to improve the accuracy of the antenna matching measurement system proposed in prior research. A 180 degree phase shifter is added to the measurement setup and a signal processing procedure is devised to optimize the measurement system performance. The improved measurement results match well to the reflection coefficient spectra measured from a conventional network analyzer. Possible causes for measurement errors are discussed.
In the third part, we developed a measurement method to acquire the transmission coefficient of microwave devices. This method combines a simple microwave circuitry and a signal processing algorithm. The test set contains an RF source, a directional coupler, a 180 degree hybrid coupler and two RF power detectors. Both magnitudes and phases of transmission coefficients can be found without the use of a network analyzer.

[1]M.Okoniewski, J. Anderson, S. S. Stuchly, “A technique to compute reflection Coefficient in FDTD method,” IEEE Antennas and Propagation Society International Symposium, 1994. AP-S. Digest, vol. 3, pp.1446-1449, 1994.
[2] Y. Y. Peng, X. Y. Wang, K. J. Lu, X. F. Qu, W. Q. Sui, “Determination of the transmission coefficients for quantum structures using FDTD method,” IEEE Nanoelectronics Conference (INEC), 2010, pp.173-174, 2010.
[3] 徐紹恩, 平面式波束掃描天線與天線阻抗量測裝置開發, 國立台灣科技大學電機工程研究所, 碩士論文, 民國99年
[4] J. D. Kraus, R. J. Marhefka, Antennas for All Applications, 3rd ed., McGraw-Hill, 2002.
[5] P. J. Kahrilas, “Desugn of electronic scanning radar systems (ESRS),” in Proceeding of the IEEE, vol. 56, no.11, pp. 1763-1771, Nov. 1968.
[6] D. M. Pozar, “Microstrip antenna aperture coupled to a microstrip line,” Electron. Lett., vol. 21, pp. 49-50, Jan. 1985.
[7] D. M. Pozar, A Review of Aperture Coupled Microstrip Antennas: History, Operation, Development, and Applications. May 1996.
[8] T. Condello, C. Pexixeiro, “Dual band dual polarization slotted microstrip patch antenna element,” IEEE Antennas and Propagation Society International Symposium, vol. 4, pp. 70-73, 2001.
[9] C. H. Tsao, Y. M. Hwang, F. Kilburg, F. Dietrich “Aperture-coupled patch antennas with wide-bandwidth and dual-polarization capabilities,” IEEE Antennas and Propagation Society International Symposium, vol. 3, pp. 936-939, 1988.
[10] 鐘偉祥, 波束掃描陣列天線, 國立台灣科技大學電機工程研究所, 碩士論文, 民國100年
[11] D. M. Hoekstra, A. E. Rosenzweig, “Extending the dynamic range of scalar network analyzer measurements,” in Proceedings of 8th IEEE Instrumentation and Measurement Technology Conference, pp. 35-39, 1991.
[12] B. Neumeyer, “A low-cost phase-measurement extension for scalar network-analyzers,” in Proceedings of 16th European Microwave Conference, pp. 779-783, 1986.
[13] K. Will, A. Omar, “Phase measurement of RF devices using phase-shifting interferometry,” IEEE Trans. Microw. Theory Tech., vol. 56, no. 11, pp. 2642-2647, 2008.
[14] M. M. Alam, C. E. Smith, “A scalar network analyzer based on detector-log amplifier RFIC chips,” in Proceedings of IEEE SoutheastCon 2001, pp. 8-10, 2001.
[15] B. Knudsen, G. F. Engen, B. Guldbrandsen, “Accuracy assessment of the scalar network analyzer using sliding termination techniques,” IEEE Trans. Instrum. Meas., vol. 38, no. 2, pp. 480-483, 1989.
[16]D. M. Pozar, Microwave Engineering, 3rdEd. New York, John Wiley & Sons, 2005.
[17]Mini-Circuits, Phase Shifter:JSPHS-2484+,
http://www.minicircuits.com/pdfs/JSPHS-2484+.pdf, Device Datasheet.
[18]Mini-Circuits, Directional Coupler:D17I,
http://www.minicircuits.com/pdfs/D17I.pdf, Device Datasheet.
[19] Michael Steer, Microwave and RF Design, SciTech Publishing, 2010
[20] Mini-Circuits, RF Power Detector:ZX47-60LN-S+,
http://www.minicircuits.com/pdfs/ZX47-60+.pdf, Device Datasheet.