本篇論文使用共平面波導的結構製作一個可以涵蓋2至6GHz的I/Q 混頻器。I/Q 混頻器是由三個基本元件所構成，包含一個寬頻耦合器、一個功分器和兩個單平衡式的混頻器。所以本論文先分別討論各元件的設計方法和製作，最後在組合成I/Q混頻器。
整個I/Q混頻器必須縮裝在小於一英寸見方的基板內，因此選用了三氧化二鋁基板(介電常數9.8)上有限地寬共平面波導來製作所有電路。
在這三個基本元件中，寬頻的90度耦合器為最困難的部份。其中耦合強度最強的中間耦合段，採用六線藍基耦合器來達成。能增進三節90度耦合器反射損耗的架構也會在此篇論文中討論。而在單平衡式混頻器製作上，採用了岔路環(rat race ring)當實現其中的180度分合波器。為了縮小面積和增加頻寬，我們使用反相器來取傳統岔路環的二分之波長180度移相器，且因為二極體是放在岔路環的中心，所以可以更縮小電路面積。

In this thesis, an I/Q mixer with operating frequency 2GHz to 6GHz is designed and fabricated. An I/Q mixer comprises three basic components, namely, a wideband coupler, a power divider and a single-balanced mixer. We will first discuss the design procedure of each component and then describe the implementation and integration of them to form a complete I/Q mixer.
The whole I/Q mixer should be integrated into a substrate of a size less than 1 inch by 1 inch. The finite ground plane coplanar waveguide (FCPW) on the Al2O3 (with dielectric constant of 9.8) substrate is chosen to implement all circuit elements.
The wideband three-section quadrature coupler is the most difficult part among three basic devices. In the tightest center coupling section, we propose a 6-line Lange coupler to achieve it. We also propose a method to improve the return loss performance of the quadrature coupler. The rat race ring 180 degree hybrid is used to implement the single-balanced mixer. In order to reduce circuit size and increase the bandwidth, a twist line phase inverter is used to replace the halve-wave 180 degree phase shifter of the conventional rat race ring. Besides, the diodes is placed inside the ring to further reduce the circuit size.

Abstract(Chinese) i
Abstract ii
Acknowledgements iii
Table of contents iv
List of Tables v
List of Figures vi
Chapter 1: Introduction 1
Chapter 2: A wideband 3-dB directional coupler 3
2.1 Theory 4
2.2 Design procedure and realization 10
2.3Three-section coupler – section 12
2.4 Three-section coupler - section 1&3 20
2.5 Three-section coupler – total cascaded circuit 24
2.6 Three-section coupler – measurement 27
Chapter 3: Wilkinson power divider 30
3.1 Theory 31
3.2 Design procedure and realization 32
3.3 Measurement 34
Chapter 4 single-balanced mixer 35
4.1 Theory 36
4.2 Circuit design 40
4.3 Measurement 43
Chapter 5: I/Q mixer 49
5.1 Measurement 50
Chapter 6: Conclusion 56
References 57

[1] E. G. Cristal and L. Young, “Theory and tables of optimum symmetrical TEM-Mode coupled transmission line directional couplers,” IEEE Trans. Microwave Theory Tech., vol. MTT-13, no. 5, pp. 544–558, Sep. 1965

[2] J. S. Izadian, “A new 6–18 GHz, 3dB multi-section hybrid coupler using asymmetric broadside, and edge coupled lines,” in IEEE MTT-S Int. Microwave Symp. Dig., 1989, pp. 243–246.

[3] G. Kemp, J. Hobdell, and J. W. Biggin, “Ultra-wideband quadrature coupler,” Electron. Lett., vol. 19, no. 6, pp. 197–198, 1983.

[4] S. Uysal and H. Aghvami, “Synthesis, design, and construction of ultra-wide-band nonuniform quadrature directional couplers in inhomogeneous media,” IEEE Trans. Microwave Theory Tech., vol. 37, pp. 969–975, June 1989.

[5] “Improved wideband 3dB nonuniform directional coupler,” Electron. Lett., vol. 25, no. 8, pp. 541–542, Apr. 1989.

[6] Duncan K.Y.Lasu, Steve P.March, Lionel E.Davis and Robin Sloam, “Simplified design technique for high performance microstrip multi-section couplers”, IEEE Trans. Microwave Theory Tech., Vol.46, No.12, PP.2507-2513, Dec.1998.

[7] T. Y. Chang, C. L. Liao, and C. H. Chen, “Novel uniplanar tandem couplers,” in Proc. 32nd Eur. Microwave Conf., 2002, pp. 127–130.

[8] R. M. Osmani, ‘Synthesis of Lange couplers,’ IEEE Trans. Microwave Theory and Techn.
Vol. 29, Feb. 1981, pp

[9] Wilkinson, E.J., “An N-way hybrid power divider,” IRE Trans. Microw. Theory Technol., 1960, MTT-8, pp. 116–118

[10] S. B. Cohn, “A class of broadband three-port TEM-mode hybrids, ”. IEEE Tram.Microwave Theory Tech., vol. MTT-16, Feb. 1968, PP. 110-116

[11] Walker, J.L.B. ”Improvements to the Design of the 180牵汹Rat Race Coupler and its Application to the design of Balanced Mixers with High LO to RF Isolation”, IEEE MMT-S Digest, 1997, Vol. II, pp 747-750

[12]S. March, “A wide band stripline hybrid ring,” IEEE Trans. Microwave Theory Tech., vol. MTT-16, p. 361, June 1968.

[13]T. Wang Z. OU and K. Wu, “Experimental study of wideband uniplanar phase inverters for MICs” in IEEE MTT-S Int. Microwave Symp. Dig., 1997, pp777-780

[14]T. Wang and K. Wu, “Size-reduction and band-broadening design technique of uniplanar hybrid ring coupler using phase inverter for M(H)MIC’s,” IEEE Trans. Microw. Theory Tech., vol. 47, pp. 198-206, Feb. 1999