隨著頻率的增加，電磁波傳遞於空氣時的損耗也逐漸增加，故需要更高增益的天線補償能量傳遞於空氣時的路徑損耗，除了電磁波於空氣中的路徑損耗之外，將天線主波束對準用戶端，使訊號準確的傳送訊號至用戶端，降低天線幅射能量往非必要的方向傳遞，造成能量不必要的消耗與其他方位訊號的干擾。切換波束陣列使用多個單元天線，具有提高增益的功能，再者，切換波束陣列擁有多個輸入端，當輸入端個別饋入時，即可幅射特定方向主波束，故切換波束陣列具有產生多個不同主波束方向的功能，使用相對應的輸入端輸入訊號使其產生的主波束對準用戶端。
本論文設計應用於第五代行動通訊韓國暫定高頻段(28 GHz)與軍方使用頻段(10 GHz)的改良切換波束陣列，使用改良後的耦合器製作與傳統巴特勒輻射方向不相同的切換波束陣列，提供切換波束天線陣列更多的選擇。
使用改良耦合器，可製作波束方向±18 deg的雙波束切換天線陣列與波束方向±9 deg、±49 deg的四波束切換波束陣列。

With increasing frequency, the loss of electromagnetic wave propagated in air also gradually increases. Therefore, higher-gain antenna is required to compensate path loss when energy propagates through the air. Transmitting the signal accurately to the users and reducing the antenna radiation energy to pass in an unnecessary direction can reduce unnecessary consumption of energy and interference with other users. The switching antenna array using many antennas has an advantage in improving gain. Furthermore, it has multiple inputs. When one of the inputs is excited, the main beam in a specific direction can be formed. Therefore, the switching antenna array has different main beam directions corresponding to different input signals.
This thesis proposes a design of modified switch antenna array for the fifth-generation mobile-communication Korea's tentative high-frequency band (28 GHz) and military band (10 GHz), using modified couplers to make switched antenna array with different directions from traditional Butler radiation. Using the modified coupler, a dual-beam switching array of ±18 deg, and a four-beam switching array of ±9 deg and ±49 deg can be fabricated.

[1]C. H. Tseng, C. J. Chen and T. H. Chu, "A Low-Cost 60-GHz Switched-Beam Patch Antenna Array With Butler Matrix Network," in IEEE Antennas and Wireless Propagation Letters, vol. 7, pp. 432-435, 2008.

[2]L. H. Zhong, Y. L. Ban, J. W. Lian, Q. L. Yang, J. Guo and Z. F. Yu, "Miniaturized SIW Multibeam Antenna Array Fed by Dual-Layer 8 × 8 Butler Matrix," in IEEE Antennas and Wireless Propagation Letters, vol. 16, pp. 3018-3021, 2017

[3]H. Ren, B. Arigong, M. Zhou, J. Ding and H. Zhang, "A Novel Design of $4 \times 4$ Butler Matrix With Relatively Flexible Phase Differences," in IEEE Antennas and Wireless Propagation Letters, vol. 15, pp. 1277-1280, 2016.
[4] Constantine A. Balanis, Antenna Theory : Analysis and Design,3rd edition,Wiley-Interscience,2005
[5] Pozar, D. M. (2005). Microwave engineering. Hoboken, NJ: J. Wiley.
[6]李莉娥，PCB製作設計規範手冊，國家晶片中心，新竹市，民國106年
[7] J. W. Lian, Y. L. Ban, C. Xiao and Z. F. Yu, "Compact Substrate-Integrated 4 × 8 Butler Matrix With Sidelobe Suppression for Millimeter-Wave Multibeam Application," in IEEE Antennas and Wireless Propagation Letters, vol. 17, no. 5, pp. 928-932, May 2018.
[8] I. Slomian, A. Rydosz, S. Gruszczynski and K. Wincza, "Three-beam microstrip antenna arrays fed by 3 × 3 Butler matrix," 2017 7th IEEE International Symposium on Microwave, Antenna, Propagation, and EMC Technologies (MAPE), Xi'an, 2017, pp. 9-12.
[9] G. Rosati and J. Munn, "Fast prototyping of an 8×8 butler matrix beamforming network for 5G applications," 2017 International Conference on Electromagnetics in Advanced Applications (ICEAA), Verona, 2017, pp. 1029-1032.
[10]Y. Cao, K. S. Chin, W. Che, W. Yang and E. S. Li, "A Compact 38 GHz Multibeam Antenna Array With Multifolded Butler Matrix for 5G Applications," in IEEE Antennas and Wireless Propagation Letters, vol. 16, pp. 2996-2999, 2017.