無線傳感器網絡系統需要具有輸出90相位差的兩個天線作為比較，並且使用非常昂貴的材料用於高頻。 已經提出了在一個天線中配備有兩個輸出90度相位差的5.8GHz微帶天線頻率。 本文提出了一種具有90度相位差輸出的5.5 - 5.8 GHz微帶天線，可用於生產具有圓極化的定向天線。 所呈現的天線包括圓形貼片，反射器，具有通孔的一對饋線和分支線耦合器。 測量結果表明，天線輸出在5.5 GHz時的相位差為86.38º，在5.8 GHz時的相位差為90.98º。 此外，天線的測量增益在5.5 GHz時為3.67 dBi，在5.8 GHz時為5.45 dBi。 在FR4基板上，天線的整體尺寸為70 mm×35 mm，介電常數為4.4。

The wireless sensor network system requires two antennas that have an output 90 phase difference as a comparison and use a very expensive material for high frequency. 5.5 – 5.8 GHz microstrip antenna frequency equipped with two output 90 degree phase difference in one antenna has been proposed. This thesis presents a 5.5 – 5.8 GHz microstrip antenna with 90-degree phase difference outputs, which is useful in producing directional antennas with circular polarization. The presented antenna consists of a circular patch, a reflector, a pair of feedlines with via holes and a branch-line coupler. The measurement results indicate that the antenna outputs have a phase difference of 86.38 º at 5.5 GHz and 90.98 º at 5.8 GHz. Moreover, the measured gain of the antenna is 3.67 dBi at 5.5 GHz and 5.45 dBi at 5.8 GHz. The overall size of the antenna is 70 mm  35 mm on an FR4 substrate with dielectric constant of 4.4.

Table of Contents
論文審定書......................................................................................................................i
Acknowledgements.........................................................................................................ii
Abstract (Chinese)..........................................................................................................iii
Abstract (English)............................................................................................................iv
Table of Contents.............................................................................................................v
List of Figures................................................................................................................viii
List of Tables...................................................................................................................xi
List of Symbols...............................................................................................................xii
Chapter 1.........................................................................................................................1
Introduction......................................................................................................................1
1.1Background.................................................................................................................1
1.2 Motivation...................................................................................................................2
1.3 Thesis Structure.........................................................................................................3
1.4 Objective.....................................................................................................................3
Chapter 2..........................................................................................................................5
Related Theory..................................................................................................................5
2.1 Microstrip Lines.......................................................................................................5
2.2 Effective Dielectric Constant and Characteristic Impedance.......................................6
2.3 Coupled Resonator Circuits.........................................................................................7
2.4. Antenna.......................................................................................................................8
2.5 Antenna Parameters.....................................................................................................9
2.5.1 Impedance Terminal...................................................................................................9
2.5.2 Return Loss/S-Parameter..........................................................................................10
2.5.3 VSWR(Voltage Standing Wave Ratio).......................................................................10
2.5.4 Polarization.................................................................................................................11
2.5.4 Radiation Pattern........................................................................................................13
2.5.5 Antenna Gain..............................................................................................................14
2.6 Microstrip Antenna.........................................................................................................16
2.6.1 Radiating Element Dimension.....................................................................................17
2.6.2 Feedline Dimension.....................................................................................................18
2.7 Directional Couplers........................................................................................................19
2.8 The Quadrature (90◦) Hybrid...........................................................................................20
Chapter 3...............................................................................................................................24
Design and Experiment..........................................................................................................24
3.1 Experimental Setup......................................................................................................24
3.2 Design of Microstrip Antenna on FR-4 Substrate.............................................................25
3.3 Microstrip Antenna Dimension Design..............................................................................26
3.3.1 Radiating Elements........................................................................................................27
3.3.2 Circular Patch.................................................................................................................28
3.3.3 Ground Plane .................................................................................................................28
3.3.4 Via Hole...........................................................................................................................28
3.3.5 Transmission Line............................................................................................................29
3.4 Branch-Line Coupler...........................................................................................................29
3.5 Simulation and Optimization...............................................................................................31
3.5.1 Microstrip Antenna...........................................................................................................31
3.5.2 Branch-Line Coupler........................................................................................................34
3.6 Results and Discussion.......................................................................................................36
3.6.1 Microstrip Antenna...........................................................................................................36
3.6.2 Branch-line Coupler..........................................................................................................41
3.6.3 Connected Microstrip Antenna and Branch-line Coupler..................................................45
Chapter 4....................................................................................................................................52
Conclusion..................................................................................................................................52
REFERENCES...........................................................................................................................53

[1] Balanis, C.A, Antena Theory: Analysis and Design, 3rd Edition. John Wiley and Sons, Inc. 2005, pp. 27, 80, 72, 30,66-68, 20-21.

[2] Balanis, C.A, Antena Theory: Analysis and Design, 4rd Edition. John Wiley and Sons, Inc. 2016, pp. 5

[3] David M. Pozar, Microwave Engineering, 3rd ed., John Wiley and Sons, Inc. 2005, pp. 317.

[4] E.R. Escobar, N.J. Kirsch, G. Kontopidis and B. Turner, “5.5 GHz optically transparent mesh wire microstrip patch antenna”, IEEE Electronics Letters, Vol.51: 1220, 2015.

[5] Yu-Hsuan Lin and Huei Wang, “A Low Phase and Gain Error Passive Phase Shifter in 90 nm CMOS for 60 GHz Phase Array System Application”, IEEE Electronics Letters, 978-1-5090-0698-4/16, 2016.

[6] Yasushi Itoh, Hiroaki Takagi, ”A Dual-Band 90-Degree SiGe HBT Active Phase
Shifter Using Band-Pass and Band-Stopsigns”, IEEE Proceedings of the 47th European Microwave Conference, Nuremberg, Germany, pp. 232, 2016.

[7] Donald K. Weaver, Design Of Rc Wide-Band 90-Degree Phase-Difference Network”, IEEE Proceedings Of The I-R-E. Caliif, pp: 671, 2016.

[8] Chung-Yi Hsu, Cho-Ying Chuang, Fu-Kang Wang, Tzyy-Sheng Horng, and Lih-Tyng Hwang, “Detection of Vital Signs for Multiple Subjects by Using Self-InjectionLocked Radar and Mutually Injection-Locked Beam Scanning Array”, IEEE Proceedings. Kaohsiung 804, Taiwan, Vol : 978-1-5090-6360-4, 2017.

[9] Abdolmehdi Dadgarpour, Ahmed A. Kishk, Tayeb A. Denidni, “Dual band high-gain antenna with beam switching capability”, IET Microwave Antennas Propagation,Vol. 11 Iss. 15, pp. 2155-2161, 2017.

[10] Peng Gao, Shuang He, Xubo Wei, Ziqiang Xu, Ning Wang, and Yi Zheng, “Compact Printed UWB Diversity Slot Antenna With 5.5-GHz Band-Notched Characteristics”, IEEE Antennas And Wireless Propagation Letters, Vol. 13 : 1536-1225, 2014.
[11] A. Abdel-Rahman, A. R. Ali, S. Amari, and A. S. Omar, “Compact bandpass filters using defected ground structure (DGS) coupled resonators,” in IEEE MTT-S Int. Microw. Symp. Dig., 2005, pp. 12–17.
[12] David M. Pozar, Microwave Engineering, 3rd ed., John Wiley and Sons, Inc. 2005, pp.
49-156.
[13]Nakar, Punit S¸ “Design of a Compact Microstrip Patch Antena for use in Nirkabel/Cellular Devices”, Thesis. The Florida State University, pp : 19,40, 2004.
[14] Edgar Hund, “Microwave Communications: Components and Circuits”, ISE Editions, McGraw-Hill Education, pp : 43, 1989.
[15] Liao, S, “circuit and analysis amplifier design, Prentice-Hall International”, Englewood Clifs NJ, pp : 140, 1987
[16] Peter. W. Gorham, “Power Dividers And Directional Couplers”, University of Hawai'i at Manoa handbook, Jeff Kowalski, pp. 6-41.
[17] Marc E. Goldfarb and Robert A. Pucel, “Modeling Via Hole Grounds in Microstrip”, IEEE Microwave and Gided Wave Letters, Vol. 1 No. 6, June 1991
[18] J. Yamasaki, I. Ohta, T. Kawai, and Y. Kokubo, “Design of broadband semi-lumped and lumped-element quadrature hybrids” ,IEEE Microwave Theory and Techniques Society International Microwave Symposium, Long Beach, California, USA, DOI: 10.1109/
MWSYM, 2005.
[19] T. Hirota, A. Minakawa, and M. Muraguchi, “Reduced-Size Branch-Line and Rat-Race Hybrid for Uniplanar MMIC's,” IEEE Trans. Microwave Theory Tech., vol. MTT-38, pp. 270-275, March 1990.
[20] Jun Wu and Lu-Yu Wang, “Analysis and Design of a 3 dB Tunable Lumped-Element Directional Coupler”, Journal Of Electronic Science And Technology, Vol. 8, No. 2, June 2010.