Signal Processing Toolbox

Zero-Pole Analysis

The zplane function plots poles and zeros of a linear system. For example, a simple filter with a zero at -1/2 and a complex pole pair at and is

• zer = -0.5; 
  pol = 0.9*exp(j*2*pi*[-0.3 0.3]');
  

To view the zero-pole plot for this filter you can use

• zplane(zer,pol)
  

or, for access to additional tools, use fvtool. First convert the poles and zeros to transfer function form, then call fvtool,

• [b,a] = zp2tf(zer,pol,1);
  fvtool(b,a)
  

and then click the Pole/Zero Plot toolbar button:

For a system in zero-pole form, supply column vector arguments z and p to zplane:

• zplane(z,p)
  

For a system in transfer function form, supply row vectors b and a as arguments to zplane:

• zplane(b,a)
  

In this case zplane finds the roots of b and a using the roots function and plots the resulting zeros and poles.

See Linear System Models for details on zero-pole and transfer function representation of systems.

Delay

Linear System Models