Design method of FIR filters with the variable piecewise stopband
T. Shinbo, Yasunori Sugita, Naoyuki Aikawa, Takashi Kimura, Yukio Wakasa, Toru Morichi · Electronics and Communications in Japan (Part III Fundamental Electronic Science) · 2005
Abstract In the field of digital signal processing, there are cases in which the frequency characteristics must be changed instantaneously in response to the processing objective. A filter whose characteristic can be varied instantaneously is called a variable filter. Many reports are available on the design of FIR digital filters with a variable passband. However, it appears that there are no publications on the design of an FIR digital filter in which the portion of the stopband with high attenuation can be varied. In this paper, a design method is proposed for an FIR digital filter using spectral parameters that make the portion of the stopband with high attenuation variable. For the design, the successive projection method with a simple algorithm is applied. A filter with an almost equal‐ripple profile for the entire amplitude characteristic is designed by varying the spectral parameters. As a result, it is possible to obtain amplitude characteristics close to those of the filter solved by the Remez algorithm for specifications that change instantaneously from time to time. Finally, a design example is presented to confirm the effectiveness of the present approach. © 2005 Wiley Periodicals, Inc. Electron Comm Jpn Pt 3, 89(4): 34–41, 2006; Published online in Wiley InterScience ( www.interscience.wiley.com ). DOI 10.1002/ecjc.20176