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ellipord

Elliptic filter order and cutoff

Description

Compute discrete elliptic filter order and cutoff for the desired response characteristics.

Usage

ellipord(Wp, Ws, Rp, Rs)

Arguments

Wp, Ws

pass-band and stop-band edges. For a low-pass or high-pass filter, Wp and Ws are scalars. For a band-pass or band-rejection filter, both are vectors of length 2. For a low-pass filter, Wp < Ws. For a high-pass filter, Ws > Wp. For a band-pass (Ws[1] < Wp[1] < Wp[2] < Ws[2]) or band-reject (Wp[1] < Ws[1] < Ws[2] < Wp[2]) filter design, Wp gives the edges of the pass band, and Ws gives the edges of the stop band. Frequencies are normalized to [0,1], corresponding to the range [0, Fs/2].

Rp

allowable decibels of ripple in the pass band.

Rs

minimum attenuation in the stop band in dB.

Value

An object of class FilterOfOrder with the following list elements:

n

filter order

Wc

cutoff frequency

type

filter type, one of "low", "high", "stop", or "pass"

Rp

dB of pass band ripple

Rs

dB of stop band ripple

This object can be passed directly to ellip to compute discrete filter coefficients.

Author(s)

Original Octave version by Paulo Neis p_neis@yahoo.com.br. Modified by Doug Stewart. Conversion to R by Tom Short.

References

Lamar, Marcus Vinicius, Notas de aula da disciplina TE 456 - Circuitos Analogicos II, UFPR, 2001/2002.

Octave Forge http://octave.sf.net

See Also

Examples

Fs <- 10000
elord <- ellipord(1000/(Fs/2), 1200/(Fs/2), 0.5, 29)
plot(c(0, 1000, 1000, 0, 0), c(0, 0, -0.5, -0.5, 0),
     type = "l", xlab = "Frequency (Hz)", ylab = "Attenuation (dB)")
el1 <- ellip(elord)
plot(c(0, 1000, 1000, 0, 0), c(0, 0, -0.5, -0.5, 0),
     type = "l", xlab = "Frequency (Hz)", ylab = "Attenuation (dB)",
     col = "red", ylim = c(-35,0), xlim = c(0,2000))
lines(c(5000, 1200, 1200, 5000, 5000), c(-1000, -1000, -29, -29, -1000),
      col = "red")
hf <- freqz(el1, Fs = Fs)
lines(hf$f, 20*log10(abs(hf$h)))
signal

Signal Processing

v0.7-6
GPL-2
Authors
Uwe Ligges [aut, cre] (new maintainer), Tom Short [aut] (port to R), Paul Kienzle [aut] (majority of the original sources), Sarah Schnackenberg [ctb] (various test cases and bug fixes), David Billinghurst [ctb], Hans-Werner Borchers [ctb], Andre Carezia [ctb], Pascal Dupuis [ctb], John W. Eaton [ctb], E. Farhi [ctb], Kai Habel [ctb], Kurt Hornik [ctb], Sebastian Krey [ctb], Bill Lash [ctb], Friedrich Leisch [ctb], Olaf Mersmann [ctb], Paulo Neis [ctb], Jaakko Ruohio [ctb], Julius O. Smith III [ctb], Doug Stewart [ctb], Andreas Weingessel [ctb]
Initial release
2015-07-29

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