DFiltNyquist

DFiltNyquist designs Nyquist (M'th band) filters

Description

DFiltNyquist designs linear phase FIR Nyquist filters. Nyquist filters are filters with an impulse response which as regular zero crossings. For an N coefficient filter, the center coefficient is one, and coefficients displaced from the center by a multiple of M are zero.

Nyquist filters are essentially the same as interpolating filters or Mth band filters. In DFiltNyquist the filter is designed based on stopband performance.

Design Strategy:
The design strategy decomposes the filter H(z) as a product of two filters
  H(z) = H0(z) H1(z).
The filter H1(z) controls the stopband. The filter H0(z) inserts the appropriate zero crossings into the response. The design is iterated as described in [1].
This program uses the program DFiltFIR to design H1(z).

Design Example:
Consider a Nyquist filter with 35 coefficients, and zero-crossing interval M=3. The sampling frequency is 16 kHz. The stopband starts at 3000 Hz. The stopband weight varies from 1 to 10.
  B.Freq = [3000 8000];
  B.Weight = [1, 10];
  h = DFiltNyquist(3, 35, B, 16000);

1. R. P. Ramachandran and P. Kabal, “Minimax Design of Factorable Nyquist Filters for Data Transmission”, Signal Processing, vol. 18, no. 3, pp. 327–339, Nov. 1989 (available on-line at http://www.ece.mcgill.ca/~pkabal/papers/).

• MATLAB release: MATLAB 7.8 (R2009a)
• Other Files: DFiltNyquist/DFiltNyquist.m, ; DFiltNyquist/Documentation/DFiltNyquist.pdf, ; DFiltNyquist/private/NYQdesNyquist.m, ; DFiltNyquist/private/NYQprintSpec.m, ; DFiltNyquist/private/NYQsolveZC.m, ; DFiltNyquist/test/PrMatrix.m, ; DFiltNyquist/test/StartDiaryFile.m, ; DFiltNyquist/test/tDFiltNyquist.m, ; DFiltNyquist/test/tDFiltNyquist.ref, ; license.txt