Programmer Guide/Command Reference/EVAL/iir1: Difference between revisions

Revision as of 13:47, 11 April 2011

Initialize and/or apply an IIR filter.

Usage 1

iir1(f1, f2 {, m, rp, rs, inv, type})

f1, f2: the lower and upper cutoff frequency; both values must be specified as relative frequencies (f / sampling-rate); 0 <= f1 < f2 <= 0.5

m: the filter order (default=5)
rp: the desired passband ripple in dB; 0 < rp (default=0.5)
rs: the desired stopband damping level in dB; 0 < rs (default=40)
inv: invert filter response (0=no, 1=yes); if this value is set to 1, the filter frequency response is inverted and f1/f2 are the boundaries of the stopband

type: the type of the filter

{class=keinrahmen"

|type=1 ||... Butterworth filter |type=2 ||... Chebyshev filter |type=3 ||... elliptic filter (this is the default)

Result: The function computes the filter coefficients for the IIR defined by the arguments and returns a matrix c with 2 columns. The first column (c[*,0]) contains the denominator coefficients (poles) and the second (c[*,1]) the nominator coefficients (zeros). The matrix c can be used to apply the filter to a signal (see Usage 3).

Usage 2

iir1(f1, f2, m, rp, rs, inv, type, x)

f1, f2, m, rp, rs, inv, type: see Usage 1
x: a vector containing the source signal

Result: The function computes the filter coefficients for the IIR defined by the arguments and applies it to the signal x. The result has the same type as the input signal x and containes the filtered signal.

Usage 3:

iir1(c, z, x{, s})
c
IIR filter coefficients (see Usage 1)
z
the filter state (delay); must be a matrix with the same dimensions as c


note: The matrix should be initialized with zeros (e.g.: #z := eval init($#c[!nrow],$#c[!ncol],0))
x
the signal sample (scalar) or the signal vector to be filtered

See also

@@ Line 1: / Line 1: @@
-{{DISPLAYTITLE:{{SUBPAGENAME}}}}
+{{DISPLAYTITLE:iir1, iir2}}
-=====iir1=====
+Initialize and/or apply an IIR filter.
+----
+;Usage 1: <code>iir1(<var>f1</var>, <var>f2</var>  {, <var>m</var>, <var>rp</var>, <var>rs</var>, <var>inv</var>, <var>type</var>})</code>
+:;<var>f1, f2</var>: the lower and upper cutoff frequency; both values must be specified as ''relative frequencies'' (f / sampling-rate); 0 <= ''f1'' < ''f2'' <= 0.5
+;<var>m</var>: the filter order (default=5)
+;<var>rp</var>: the desired passband ripple in dB; 0 < ''rp'' (default=0.5)
+;<var>rs</var>: the desired stopband damping level in dB; 0 < ''rs'' (default=40)
+;<var>inv</var>: invert filter response (0=no, 1=yes); if this value is set to 1, the filter frequency response is inverted and f1/f2 are the boundaries of the stopband
+<var>type</var>: the type of the filter
+::{class=keinrahmen"
+|''type''=1 ||... Butterworth filter
+|''type''=2 ||... Chebyshev filter
+|''type''=3 ||... elliptic filter (this is the default)
+;Result: The function computes the filter coefficients for the IIR defined by the arguments and returns a matrix ''c'' with 2 columns. The first column (''c''[*,0]) contains the denominator coefficients (poles) and the second (''c''[*,1]) the nominator coefficients (zeros). The matrix ''c'' can be used to apply the filter to a signal (see '''Usage 3''').
+----
+;Usage 2: <code>iir1(<var>f1</var>, <var>f2</var>, <var>m</var>, <var>rp</var>, <var>rs</var>, <var>inv</var>, <var>type</var>, <var>x</var>)</code>
+:;<var>f1, f2, m, rp, rs, inv, type</var>: see Usage 1
+:;<var>x</var>: a vector containing the source signal
+;Result: The function computes the filter coefficients for the IIR defined by the arguments and applies it to the signal ''x''. The result has the same type as the input signal ''x'' and containes the filtered signal.
+----
+:Usage 3: <code>iir1(<var>c</var>, <var>z</sub>, <var>x</sub>{, <var>s</var>})
+:;<var>c</var>: IIR filter coefficients (see '''Usage 1''')
+:;<var>z</var>: the filter state (delay); must be a matrix with the same dimensions as ''c''
+:note: The matrix should be initialized with zeros (e.g.: <code>#z := eval init($#c[!nrow],$#c[!ncol],0)</code>)
+:;<var>x</var>: the signal sample (scalar) or the signal vector to be filtered
+:;
-An Infinite Impulse Response (IIR) filter.
+;See also:
-=====Usage:=====
-<code>iir1(<var>f1</var>, <var>f2</var>, <var>m</var>, <var>rp</var>, <var>rs</var>, <var>inv</var>, <var>type</var>)</code>
-=====Function:=====
-Computes the filter coefficients for an IIR filter with cutoff frequencies <var>f1</var> and <var>f2</var> and the order <var>m</var>.
-=====Parameters:=====
-;<var>f1</var>
-:The rel. lower cutoff frequency.
-;<var>f2</var>
-:The rel. upper cutoff frequency (<code>0 <=</code> <var>f1</var> <code><</code> <var>f2</var> <code><= 0.5</code>).
-;<var>m</var>
-:The filter order (<var>m</var> <code>>= 2</code>). The default is <code>3</code>.
-;<var>rp</var>
-:The passband riple in dB (<var>rp</var> <code>> 0</code>). The default is <code>0.5</code>.
-;<var>rs</var>
-:The stopband damping in dB (<var>rs</var> <code>> 0</code>). The default is <code>40</code>.
-;<var>inv</var>
-:The invert frequency response (<code>0</code>|<code>1</code>). The default is <code>0</code>.
-;<var>type</var>
-:The type of filter to use. The following values are supported:
-:<code>1</code> A Butterworth filter
-:<code>2</code> A Chebyshev filter
-:<code>3</code> An elliptic filter (This is the default).
-=====Result:=====
-A matrix <code>c</code> with 2 columns:
-(<code>c[*,0] = poles</code>, <code>c[*,1] = zeros</code>)
-=====Usage:=====
-<code>iir1(<var>f1</var>, <var>f2</var>, <var>m</var>, <var>rp</var>, <var>rs</var>, <var>inv</var>, <var>type</var>, <var>x</var>)</code>
-=====Function:=====
-Computes the filter coefficients for an IIR filter with cutoff frequencies <var>f1</var> and <var>f2</var> and the order <var>m</var> and apply it to the signal <var>x</var>.
-=====Parameters:=====
-;<var>x</var>
-:A signal vector.
-For all other parameters see <code>irr1</code> above.
-=====Result:=====
-A filtered signal of the same type as <var>x</var>.

Programmer Guide/Command Reference/EVAL/iir1: Difference between revisions

Revision as of 13:47, 11 April 2011

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