zplane
Z-plane zero-pole plot for discrete-time filter System object
Syntax
zplane(filt)
zplane(filt,Name,Value)
[zLoc,pLoc,tLoc]
= zplane(filt)
Description
zplane( plots
the zeros and poles of the filter System
object™, filt)filt,
with the unit circle for reference in the filter visualization tool
(fvtool). Each zero is represented with a 'o' and
each pole with a 'x' on the plot. Multiple zeros
and poles are indicated by the multiplicity number shown to the upper
right of the zero or pole.
When you call the step method on the filter System
object with
a fixed-point input, the filter becomes a quantized fixed-point filter, filtQuant.
When filtQuant is a quantized filter, zplane(filtQuant) plots
the poles and zeros of the quantized and unquantized filters. The
symbols 
and + represent the zeros
and poles of the quantized filter filtQuant. The
plot includes the unit circle for reference.
zplane( returns
the pole zero plot with additional options specified by one or more filt,Name,Value)Name,Value pair
arguments.
[ returns the vector
of locations for zeros, poles, and text objects. zLoc,pLoc,tLoc]
= zplane(filt)zLoc is
the vector of locations of zeros, pLoc is the vector
of locations of poles, and tLoc is the vector of
locations of the axes/unit circle line and text objects which are
present when there are multiple zeros or poles. In case there are
no zeros or poles, zLoc or pLoc is
set to the empty matrix [].
Input Arguments
Name-Value Pair Arguments
Specify optional
comma-separated pairs of Name,Value arguments. Name is
the argument name and Value is the corresponding value.
Name must appear inside quotes. You can specify several name and value
pair arguments in any order as
Name1,Value1,...,NameN,ValueN.
'Arithmetic' — Value types:
'double' | 'single' | 'fixed'
When you specify 'double' or 'single',
the function performs double- or single-precision analysis. When you
specify 'fixed' , the arithmetic changes depending
on the setting of the CoefficientDataType property
and whether the System
object is locked or unlocked.
Details for Fixed-Point Arithmetic
When you do not specify the arithmetic for non-CIC structures, the function uses double-precision arithmetic if the filter System object is in an unlocked state. If the System object is locked, the function performs analysis based on the locked input data type. CIC structures only support fixed-point arithmetic.
Output Arguments
|
Vector of locations of zeros. |
|
Vector of locations of poles. |
|
Vector of locations of axes/unit circle line and text objects. |
Examples
Plot the Poles and Zeros of a Fourth-Order Filter
Create a Fourth-order IIR digital filter with a cutoff frequency of 0.6. Plot the poles and zeros of this filter.
[b,a] = ellip(4,.5,20,.6); zplane(b,a);
Quantize the filter by passing a fixed-point input through the filter algorithm. Plot the quantized and unquantized poles and zeros associated with this filter.
iirFilt = dsp.IIRFilter('Numerator',b,'Denominator',a); in = fi(randn(15,6),1,15,3); out = iirFilt(in); zplane(iirFilt)
