| Summary: | 碩士 === 國立中央大學 === 電機工程研究所 === 95 === Baluns designed for digital TV( UHF 470-710MHz ) applications will be presented in this thesis. Conventional Marchand baluns employ coupled lines. These structures occupy large circuit areas, especially for lower frequency applications (ex .DVB-T). In this thesis, we replaced conventional Marchand baluns open-terminal to short, the required coupled-line lengths of this balun structure can be made as short as . This balun is suitable for low impedance-transforming ratio . At open-terminal, with a series capacitor to ground, we can find how to control bandwidth by using the optimal value of the capacitor. The miniature, narrow band, wide impedance-transforming ratio balun is realized by using one series capacitor at unbalanced port, but it is sensitive to output impedance. In terms of the center of impedance and amplifier design, circuit structures insensitive to output impedance are presented. This balun bandwidth is controllable, and the required coupled-line lengths of this balun structure can be made as short as . Finally, the fabrication on single printed circuit broad is presented, and it supplied another choice. Both baluns achieved 0.5 dB amplitude balance and phase balance. All circuits are fabricated on FR4 substrate, and are in good agreement with simulation.
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