Example 9.20 (a).  Find the general solution to  [Graphics:Images/ZTransformDEMod_gr_452.gif].

[Graphics:../Images/ZTransformDEMod_gr_517.gif]

Solution 9.20 (a).

    The homogeneous difference equation has the form  (9-8) with [Graphics:../Images/ZTransformDEMod_gr_458.gif] and  [Graphics:../Images/ZTransformDEMod_gr_459.gif] so that the solution are complex and have the form  

        [Graphics:../Images/ZTransformDEMod_gr_460.gif],  

where  [Graphics:../Images/ZTransformDEMod_gr_461.gif]  and  [Graphics:../Images/ZTransformDEMod_gr_462.gif].  Hence, the general homogeneous solution is  

        [Graphics:../Images/ZTransformDEMod_gr_463.gif].

Remark.  The homogeneous solution is transient and and will decay to [Graphics:../Images/ZTransformDEMod_gr_464.gif] as [Graphics:../Images/ZTransformDEMod_gr_465.gif], i.e.  [Graphics:../Images/ZTransformDEMod_gr_466.gif].  An illustration using [Graphics:../Images/ZTransformDEMod_gr_467.gif] is shown in figure 2 below.

Typo.  Please note that there is a typo in the book which mistakenly stated that the homogeneous solution involves [Graphics:../Images/ZTransformDEMod_gr_468.gif].  We apologize for this inconvenience.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

(c) 2006 John H. Mathews, Russell W. Howell