Improvement on frequency characteristics of integrator-based filters by reducing spread of unity-gain frequencies
✍ Scribed by Kazuyuki Wada; Shigetaka Takagi; Nobuo Fujii
- Publisher
- John Wiley and Sons
- Year
- 2000
- Tongue
- English
- Weight
- 183 KB
- Volume
- 83
- Category
- Article
- ISSN
- 1042-0967
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✦ Synopsis
ln the design of integrator-based filters, there are degrees of freedom in selection of the signal flow graph representing the connection state of the integrator. In this paper, a procedure is proposed for selecting the signal flow graph for a filter with a small deviation from the ideal frequency characteristics. In general, the integrator works ideally near the unit-gain frequency. Hence, in order to realize a filter with excellent characteristics, a guideline is described for selecting the signal flow graph such that the unit-gain frequencies of all integrators used in the filter are close to each other. Since the amount of computation for selection of the signal flow graph becomes enormous even in a filter of low order, an evaluation scale for search is used that can easily estimate the spread of the unit-gain frequencies in individual signal flow graphs. As examples, the signal flow graphs are derived for the fifth-order maximally flat-delay low-pass filter and the third-order amplitude equal-ripple low-pass filter. The validity of the proposed evaluation scale is presented. The effectiveness of the design guideline is confirmed by a computer simulation of the filter made up of MOSFET based on the obtained signal flow graphs.