A DLL-Based Frequency Multiplier for MBOA-UWB System
| Autor: | Keng-Jan Hsiao, 蕭耕然 |
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| Rok vydání: | 2005 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 93 The FCC has approved an unlicensed usage of spectrum from 3.2 GHz to 10.5 GHz called “ultra wide band (UWB)”. There are two proposed standards that are MBOA and DS respectively for this application. The MBOA-UWB system utilizes MB-OFDM technique. Our goal is to implement a frequency multiplier for the MBOA-UWB system. The difficulty of generating the carrier frequency arises from the stringent restriction on band-hopping time less than 9.5 ns. Conventional PLL-based frequency synthesizer usually takes hundreds of micro-seconds to settle and isn’t capable for such application. Another existing solution implements a non-switching PLL with single-side-band (SSB) mixing to shift the output frequency from the PLL to desired band. However, the SSB mixing has many inherent drawbacks such as high phase noise, high power, and spurious tones. The LO leakage and the unwanted sideband translate adjacent interferences to the baseband and corrupt the signal at the desired channel. All foregoing non-ideal effects degrade the performance of the UWB transceivers severely. A traditional DLL-Based frequency multiplier can only generate single one output frequency while the input frequency is fixed, whereas the UWB system demands three carrier frequencies. A modified DLL-based frequency multiplier can change the multiplication factor of the reference frequency. By switching the feedback clock from one delay cell to another, the equivalent number of delay cells is changed, and the output frequency will hop to a different band within 9.5 nSec. This frequency multiplier with 528-MHz input reference frequency can achieve less than 9.5-ns settling time by utilizing wide loop bandwidth and fast-settling architecture. The quadrature I and Q signals are generated by a divide-by-2 operation. The UWB frequency multiplier has been fabricated in a 0.18 |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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