| Summary: | 碩士 === 長庚大學 === 電機工程研究所 === 87 === Due to the abilities of both power combination and power division, microwave couplers play very important role in high frequency communication systems. In this thesis, equivalent formulas of calculating the values of lumped-element components to form equivalent networks of /4 and 3/4 transmission lines are adopted. The considerations of high frequency parasitic effects make the SMT （Surface Mount Technology）devices used in circuit fabrications. Also the methods of even & odd mode analysis and particularly equivalent solutions simplify the processes to calculate the solutions of lumped-element Lange coupler.
According to the results we developed, a 2.4GHz lumped-element branch-line coupler on printed circuit board using SMT capacitors is designed and fabricated. On Al2O3 substrate, a 2.4 GHz lumped-element branch-line coupler and a 2.4 GHz lumped-element Lange coupler are designed and the circuits are fabricated by the MMIC（Monolithic Microwave Integrated Circuits）processes offered by National Central University. A 1800 hybrid is designed and fabricated on the silicon substrate of TSMC 0.6 um 1p3m technology. To solve the low Q problem in MMIC process, we developed the active inductor, and also an active Lange coupler was designed with the active inductor previously mentioned. All the measured results reveal that the equivalent formulas driven before are correct, and the concept of active inductor is reliable. And since lumped-element couplers have the property of symmetry, the stability problems of devices and process are very important.
Finally we design a single balanced diode mixer based on the lumped-element branch line coupler on printed circuit board. The measured results show that the mixer has a —13dB conversion loss, and such result is much worse than a normal one. The discovered problems will give us a positive approach in the future.
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