Frequency response

Given the following transfer function:

$$H(z)=\frac{(1-z^{-1})(1+z^{-1})}{1-1.1314z^{-1}+0.64z^{-2}}$$

You can enter the information in the same way as in the previous subsection.

• Using the freqz function

  >> freqz(num,den)
  

  Figure 7: Frequency response

  
  Notice the frequency scale. Also, the magnitude response is in dB.
• Another way to use freqz

  >> [H,w]=freqz(num,den);
  >> subplot(2,1,1)
  >> plot(w,abs(H))
  >> grid on
  >> xlabel('freq. (rad/sec)')
  >> ylabel('mag. response')
  >> subplot(2,1,2)
  >> plot(w,angle(H))
  >> grid on
  >> xlabel('freq. (rad/sec)')
  >> ylabel('phase response')
  

Figure 8: Frequency response (example 2)