本論文提出兩款應用於UHF射頻辨識系統讀取器近場天線，此兩款近場天線分別可產生較強的垂直與水平方向之近場磁場，可有效提升物件標籤之辨識距離，相當適用於近場辨識與定位系統。本研究即使用所設計之近場天線，研發出購物台讀取器天線與智慧型書架定位系統，其中購物台讀取器天線可於特定範圍內讀取任意方向之物件標籤，相當適合應用於賣場之結帳系統，以節省人力資源並提高結帳效率。至於智慧型書架則具有辨別書籍位置之能力，可讓使用者進行即時查詢之動作，以軟體介面即時顯示書籍所在位置與相關書籍資訊，有效提升書籍管理之效率與降低藏書遺失率。
另外，本論文以向量相加法整合出一2.4GHzISM頻段之相位偏移器，其所需之被動電路係沿用前人研發之人工傳輸線進行微型化之設計，其中包含：180度方向耦合器、90度方向耦合器與威爾金森功率分配器，均可有效降低電路面積並具有良好之元件特性。此外，本論文亦提出一款可變增益之放大器，係採用兩級串聯式之電路架構，以實現可變增益之特性，並且僅需改變其偏壓狀態即可有效控制放大器之輸出增益。
本論文應用上述主被動射頻元件合成一主動式相位偏移器，經實驗結果證明其具有良好的相位控制性能，僅需控制放大器偏壓狀態即可產生不同的系統輸出相位延遲，且在各相位狀態皆有趨近於相同的增益輸出。最後，本論文使用此相位偏移器合成一主動式波束合成網路，並成功設計出一款相位陣列天線，實際驗證其具有電子式波束掃描之能力，具有效增強通訊方向之增益且降低其他方向之干擾之效能，可應用於RFID定位及增進讀取涵蓋範圍等方面。

This thesis proposes two near field reader antennas for applications in the UHF radio frequency identification (RFID) system. Strong vertical and horizontal magnetic fields in near zones are respectively induced by those two reader antennas, so that the readable distance of the near-field tags attached on objects can be enhanced significantly. Thus, the reader antennas are capable of near-field identification and positioning applications, such as the Point of Sale (POS) and intelligent bookshelf systems. For the POS system, the tags at any directions within certain range can be recognized by using the near-field reader antenna so that the manpower may be saved with better payment efficiency. As for the intelligent bookshelf system, it shows that a good identification ability with data searching and positioning of books can be immediately obtained through a middleware, so that the management efficiency and allocation of books may both be improved.
On the other hand, a 3-bit phase shifter based on a vector sum method is presented to operate in the 2.4GHz ISM band, where some passive components including 180°directional coupler, 90°directional coupler and Wilkinson power divider are designed by using the artificial transmission line (ATL) to achieve both circuit miniaturization and good characteristics. A variable gain amplifier with a two-stage cascade structure is also designed to perform the gain variation, where the voltage of bias circuit is varied to meet the requirements of the output gain.
An active phase shifter is obtained by combining the above passive and active RF components. Good performance in phase control is demonstrated with experimental results, which uses the voltage control of bias circuit to produce the different phase delays with nearly identical output gain. Further, the active phase shifter is applied to construct an active beam-forming network to design the phased array in this thesis. Therefore, the capability with electronic beam scanning of phased array is obtained and verified with measurements. Thus, the transmitting gain of the desired direction can be increased and the unwanted interferences from other directions may be suppressed. The active beam-forming network can be applied for positioning objects and improving coverage in the RFID system.

[1] Daniel M. Dobkin, The RF in RFID: passive UHF RFID in practice, Newnes Inc., 2008.

[2] Martin Cooper and Marc Garc Goldburg, “Intelligent Antennas: Spatial Division Multiple Access,” in 1996 Annual Review of Communications, pages 999-997.

[3] Salvatore Bellofiore, Constantine A. Balanis, Jeffrey Foutz, and Andreas S. Spanias, “Smart-Antenna Systems for Mobile Communication Networks Part 1: Overview and Antenna Design,” IEEE Antenna’s and Propagation Magazine, vol. 44, no. 3, June 2002.

[4] Klaus Finkenzeller, RFID Handbook, John Wiley & Sons, Inc., 2nd ed., 2003.

[5] Udo Karthaus and Martin Fischer, “Fully Integrated Passive UHF RFID Transponder IC With 16.7-μW Minimum RF Input Power,” IEEE Journal of solid-state circuit, Vol. 38, No. 10, October 2003.

[6] J. Curty, M. Declercq, C. Dehollain, and N. Joehl, “Design and Optimization of Passive UHF Systems,” Springer, 2006.

[7] Roger Stewart, “UHF Passive-Tag IC Design,” IEEE MTT-S, Session TSC-110, June 2006.

[8] G. De Vita and G. Iannaccone, “Design criteria for the RF section of UHF and microwave passive RFID transponders,” IEEE Transactions on Microwave Theory and Techniques, Vol. 53, Issue 9, pp. 2978-2990, September 2005.

[9] Constanntine A. Balanis, Antenna Theory: Analysis and Design, John Wiley & Sons Inc., 3nd ed., 2005.

[10] Daniel M. Dobkin, Steven M. Weigand and Nathan Iyer, “Segmented Magnetic Antennas for Near-Field UHF RFID,” Microwave Journal, Vol. 50, No. 6, June 2007.

[11] Warren L. Stutzman and Gary A. Thiele, Antenna Theory and Design, John Wiley & Sons, Inc., 2nd ed., 1997.

[12] Constantine A. Balanis, Advanced Engineering Electromagnetics, John Wiley & Sons, Inc., 1989.

[13] Kai Chang, RF and Microwave Wireless Systems, John Wiley & Sons, Inc., 2000.

[14] Behzad Razavi, RF Microelectronics, Prentice Hall, Inc., 1998.

[15] Svetoslav Gueorguiev, Saska Lindfors, and Torben Larsen, “A 5.2GHz CMOS I/Q Modulator With Integrated Phase Shifter for Beamforminng,” in IEEE Journal of Solid-State Circuits, vol. 42, no. 9, September 2007.

[16] C.-W. Wang, T.-G. Ma and C.-F. Yang, “A New Planar Artificial Transmission Line and its Applications to Miniaturized Butler Matrix for Frequency Identification Systems,” in IEEE Microwave Theory and Techniques, vol. 55, no. 12, December 2007.

[17] Frank Ellinger, Heinz Jackel, and Werner Bachtold, “Varactor-Loaded Transmission-Line Phase Shifter at C-Band Using Lumped Elements,” in IEEE Microwave Theory and Techniques, vol. 51, no. 4, April 2003.

[18] Shi Cheng, Erik Ojefors, Paul Hallbjorner, and Anders Rydberg, “Compact Reflective Microstrip Phase Shifter for Traveling Wave Antenna Applications,” in Microwave and Wireless Components Letters, vol. 16, no. 7, July 2006.

[19] Chien-San Lin, Sheng-Fuh Chang, and Wen-Chun Hsiao, “A Full-360° Reflection-Type Phase Shifter With Constant Insertion Loss,” in Microwave and Wireless Components Letters, vol. 18, no. 2, February 2008.

[20] S. J. Kim and N. H. Myung, “A New Active Phase Shifter Using a Vector Sum Method,” in IEEE Microwave and Guided Wave Letters, vol. 10, no. 6, June 2000.

[21] J. K. Ryoo and S. H. Oh, “Broadband 4-bit Digital Phase Shifter Based on Vector Combining Method,” SBMO/IEEE MTT-s IMOC, vol. 1, pp. 17-19, September 2003.

[22] Po-Yu Chen, Tian-Wei Huang, Huei Wang, Yu-Chi Wang, Chung-Hsu Chen, and Pane-Chane Chao, ”K-Band HBT and HEMT Monolithic Active Phase Shifter Using Vector Sum Method,” in IEEE Microwave Theory and Techniques, vol. 52, no. 5, May 2004.

[23] Stelios A. Mitilineos, George K. Mitropoulos, and Christos N. Capsalis, ”A New Active RF Phase Shifter Using Variable Gain, Drain Voltage Controlled PHEMTs: A 2.4-GHz ISM Impementation,” in Microwave and Wireless Components Letters, vol. 15, no. 7, July 2005.

[24] Pei-Si Wu, Hong-Yeh Chang, Ming-Da Tsai, Tian-Wei Huang, and Huei Wang, ”New Miniature 15-20-GHz Continuous-Phase/Amplitude Control MMICs Using 0.18-μm CMOS Technology,” in IEEE Transactions on Microwave Theory and Techniques, vol. 54, no. 1, January 2006.

[25] David M. Pozar, Microwave Engineering, John Wiley & Sons Inc., 3nd ed., 2005.

[26] A.-S. Liu, H.-S. Wu, C.-K.C. Tzuang, and R.-B. Wu, “Ka-band 32-GHz Planar Integrated Switched-Beam Smart Antenna,” in IEEE MTT-S Int. Microwave Sym. Dig., Long Bench CA, pp. 565-568, 12-17 June 2005.

[27] I. Toyoda, T. Hirota, T. Hiraoka, and T. Tokumitsu, “Multilayer MMIC Branch-Line Coupler and Broad-Side Coupler,” in Microwave and Millimeter-Wave Monolithic Circuits Symposium Digest, Albuquerque NM, 1-3 June 1992, pp. 79–82.

[28] Y.-C. Chiang and C.-Y. Chen, “Design of A Wide-Band Lumped-Element 3-dB Quadrature Coupler,” IEEE Transactions on Microwave Theory Tech., vol. 49, no. 3, pp. 476–479, Mar.2001.

[29] F.-R. Yang, K.-P. Ma, Y. Qian and T. I. Itoh, “A Uniplanar Compact Photonic-Bandgap (UC-PBG) Structure and its Applications for Microwave Circuits,” IEEE trans. Microwave Theory Tech., vol. 47, no. 8, pp. 1509-1514, Aug. 1999.

[30] Y. J. Sung, C. S. Ahn and Y.-S. Kim, “Size Reduction and Harmonic Suppression of Rat-Race Hybrid Coupler Using Defected Ground Structure,” IEEE Microwave Wireless Comp. Lett., vol. 14, no. 1, pp. 7–9, Jan. 2004.

[31] K. W. Eccleston and S. H. M. Ong, “Compact Planar Microstrip Line Branch-Line and Rat-Race Couplers,” IEEE trans. Microwave Theory Tech., vol. 51, no. 10, pp. 2119-2125, Oct. 2003.

[32] K.-O. Sun, S.-J. Ho, C.-C.Yen and D. van der Weide, “A Compact Branch-Line Coupler Using Discontinuous Microstrip Lines,” IEEE Microwave Wireless Comp. Lett., vol. 15, no. 8, pp. 519-520, Aug. 2005.

[33] C.-W. Wang, T.-G. Ma and C.-F. Yang, “Miniaturized Branch-Line Coupler with Harmonic Suppression for RFID Applications Using Artificial Transmission Lines,” in IEEE MTT-S Int. Microwave Sym. Dig., Honolulu, pp. 29-32, 3-8 June 2007.

[34] K.-H. Li, C.-W. Wang, and C.-F. Yang, ”A Miniaturized Diplexer Using Planar Artificial Transmission Lines for GSM/DCS Applications,” in IEEE Asia Pacific Microwave Conference.

[35] C.-W. Wang, K.-H. Li, and T.-G. Ma, ”A Miniaturized Wilkinson Power Dividerwith Harmonic Suppression Characteristics Using Planar Artificial Transmission Lines,” in IEEE Asia Pacific Microwave Conference.

[36] W. R. Eisenstadt and Y. Eo, “S-Parameter-Based IC Interconnect Transmission Line Characterization,” in IEEE Trans. on Components, Packaging, and Manufacturing Technology, vol. 15, pp. 483-490, August 1992.