Z transform
Z transform permit the processing of digital signals and discrete systeme.
1. Definition
The Z transform is defined by : 
2. Stability in Z
A discrete system whose transfer function is expressed according to Z is stable if all the poles have a module lower than 1.
3. Propriety
3.1. Linearity
3.2. Delay Theorem
It is noticed that to delay a causal signal of N samples is equivalent to multiply its Z transform by. 
3.3. Product of convolution
3.4. Multiplication by
3.5. Multiplication by
3.5. Multiplication by
4. Z transform of tests signals
Dirac :  .  Step:  . 
5. End value and initial value theorem
Initial value theorem:  End value theorem : 
6. Research of original It's necessary to arrange the initial expression to obtain forms in tables by carrying out operations such as the decomposition in simple elements
