ellip {signal}

Elliptic or Cauer filter

Description

Generate an Elliptic or Cauer filter (discrete and continuous).

Usage

## Default S3 method:
ellip(n, Rp, Rs, W, type = c("low", "high", "stop",
"pass"), plane = c("z", "s"), ...)

## S3 method for class 'FilterOfOrder'
ellip(n, Rp = n$Rp, Rs = n$Rs, W = n$Wc, type = n$type, ...)

Arguments

n

filter order or generic filter model

Rp

dB of pass band ripple

Rs

dB of stop band ripple

W

critical frequencies of the filter. W must be a scalar for low-pass and high-pass filters, and W must be a two-element vector c(low, high) specifying the lower and upper bands. For digital filters, W must be between 0 and 1 where 1 is the Nyquist frequency.

type

Filter type, one of "low" for a low-pass filter, "high" for a high-pass filter, "stop" for a stop-band (band-reject) filter, or "pass" for a pass-band filter.

plane

"z" for a digital filter or "s" for an analog filter.

...

additional arguments passed to ellip, overriding those given by n of class FilterOfOrder.

Details

Because ellip is generic, it can be extended to accept other inputs, using "ellipord" to generate filter criteria for example.

Value

An Arma object with list elements:

b

moving average (MA) polynomial coefficients

a

autoregressive (AR) polynomial coefficients

Author(s)

Original Octave version by Paulo Neis [e-mail]. Modified by Doug Stewart. Conversion to R by Tom Short.

References

Oppenheim, Alan V., Discrete Time Signal Processing, Hardcover, 1999.

Parente Ribeiro, E., Notas de aula da disciplina TE498 - Processamento Digital de Sinais, UFPR, 2001/2002.

https://en.wikipedia.org/wiki/Elliptic_filter

Octave Forge https://octave.sourceforge.io/

See Also

Arma, filter, butter, cheby1, and ellipord

Examples

  # compare the frequency responses of 5th-order Butterworth and elliptic filters.
  bf <- butter(5, 0.1)
  ef <- ellip(5, 3, 40, 0.1)
  bfr <- freqz(bf)
  efr <- freqz(ef)
  plot(bfr$f, 20 * log10(abs(bfr$h)), type = "l", ylim = c(-50, 0),
       xlab = "Frequency, radians", ylab = c("dB"))
  lines(efr$f, 20 * log10(abs(efr$h)), col = "red")