Design of Low-Voltage Square-Root Domain Filters andSystematic Synthesis of High-Order Filters
| Autor: | Gwo-Jeng Yu, 余國正 |
|---|---|
| Rok vydání: | 2005 |
| Druh dokumentu: | 學位論文 ; thesis |
| Popis: | 93 Square-root domain (SRD) filters feature a nonlinear mapping on the state variables of a state-space description for a particular transfer function. In order to realize the SRD filters, state equations must be further transformed to nodal equations at the nodes of grounded capacitors. Furthermore, based on the MOSFET square law relationship, the nodal equations are altered to intermediate variables, where the nodal equations demonstrate that the circuits of first-order and second-order current-mode SRD filters basically comprise current mirrors, current-mode square-root circuits, and capacitors. Then, by means of interconnection of sub-circuits to realize the terms of nodal equations, the circuit diagrams of current-mode SRD filters are accomplished. Simultaneously, by adopting the technology of low-voltage level-shift and utilizing TSMC 0.25 �慆 1p5m CMOS technology operated with 1.5 V power supply voltage, an experiment of SRD band-pass filter and several simulated results of SRD filters are proposed. Both of the simulated and measured results agree with each other accordingly, and have shown that the center frequency f0 is not only attainable at megahertz frequencies but also tunable electronically. The proposed circuits, thus, have the advantages of high frequency operation, tuneability, low supply voltage operation, low power consumption, and low noise. Obviously a low voltage continuous-time filter implemented by the conventional digital CMOS technology is proved to be suitable for system-on-a-chip application. A systematic synthesis for high-order SRD based on the quadratic I-V relationship for an MOSFET operated in saturation region is also presented. Emphases are placed on the methodology of filter synthesis, the constructive settings of DC components for input signals, the DC voltages of the state-space variables, and the DC bias current I0. The proposed prototypes of square-root domain filters are able to overcome the possible inequality between the input and output node of DC level, in which improve the reliability of high-order filter implementation. Furthermore, by means of adjusting the range of the DC bias current I0 in the acceptable boundary, the center frequency f0 or 3 dB frequency f3dB of the proposed prototypical circuits of SRD filters is not only attainable at megahertz frequencies but also tunable electronically. Simulations are performed with the model of a 0.25 �慆 CMOS process at 1.5 V supply voltage. The simulated results, which provide that the average errors of frequency response are smaller than 1.0%, demonstrate the validity of the proposed synthetic technique. The synthesized filters have the features of high frequency operation, tuneability, extensibility, and low power consumption. |
| Databáze: | Networked Digital Library of Theses & Dissertations |
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