Wiley signals and systems e book TLFe BO 349

F'igiiri-. 1311: Enact frequrncy rrsponsr to (1 3.28) and the estimate from t,ho polc-zero
d iagr a m

Substituting z = 1 into (13.28) gives A- = -1. The estimates are show11 in
Figwe 13.11 with the exact
t for comparison, Zeros lying tiirertly or1 the unit
cirrle forcc7 the magnitude o
Fourier tiensforrn at this f r ~ q w r i c yto zero, and
[ d e s lying w a r to tlw niiit circle incrraso the
uiiit, circle that a pcrle 01 x r o lies, the greater PB
it, has on thc h"mr.ier transform.
Poles 01 zeros at the origin of the z-plane hav
influence oil h ma,gni( ude of
the Four ic.1 trarisforin, hiit they do inakc ~1 h e a r roni rihut ion towards tlrc phase.