| Summary: | 碩士 === 國立臺灣大學 === 電子工程學研究所 === 94 === The fast-growing market in personal wireless communications has motivated the development of fully integrated transceivers using a cost-efficient CMOS process. Frequency synthesizers are widely used to provide a stable, clean and programmable carrier frequency in modern communication systems. In order to satisfy the increasing demands and to avoid the over-crowded radio transmission, new wireless standards have been proposed at higher frequency bands. With the limitations on the cut-off frequency of the transistors, it is still a great design challenge to implement CMOS synthesizers operating at frequencies beyond 10 GHz.
In chapter 3 presents a fully integrated frequency synthesizer implemented in a 0.18-um foundry CMOS process. By employing a modified differential Colpitts VCO to improve the tuning range and the phase noise, the integer-N frequency synthesizer demonstrates an output frequency from 14.8 to 16.9 GHz, allowing wideband operations at Ku-band. Operated at an output frequency of 15 GHz, the proposed synthesizer exhibits a reference sideband power of -50 dBc and a phase noise of -104.5 dBc/Hz at 1-MHz offset. The fabricated circuit consumes a dc power of 70 mW from a 2-V supply voltage.
A triple-modulus phase-switching prescaler for high-speed operations is presented in chapter 4. By reversing the switching order between the eight 45°-spaced signals generated by the 8:1 frequency divider, the maximum operating frequency of the prescaler is effectively enhanced. With the triple-modulus switching scheme, a wide frequency covering range is achieved. The proposed prescaler is implemented in a 0.18-um CMOS process, demonstrating a maximum operating frequency of 16 GHz without additional peaking inductors for a compact chip size. Based on the high-speed prescaler, a fully integrated integer-N frequency synthesizer is realized. The synthesizer operates at an output frequency from 13.9 to 15.6 GHz, making it very attractive for wideband applications in Ku-band. At an output frequency of 14.4 GHz, the measured sideband power and phase noise at 1-MHz offset are -60 dBc and -103.8-dBc/Hz, respectively. The fabricated circuit occupies a chip area of 1 mm2 and consumes a dc power of 70 mW from a 1.8-V supply voltage.
A 12-18GHz frequency synthesizer with automatic frequency calibration is presented in chapter 5. By employing both of the switched-capacitor and switched-inductor methods, we can implement a wide-tuning range VCO. At the Ku-band, the proposed VCO achieve wideband operation which is about 36% of the tuning range.
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