Engineering Tables/Z Transform Properties

	Time domain	Z-domain	ROC
Notation	$x[n]={\mathcal {Z}}^{-1}\{X(z)\}$	$X(z)={\mathcal {Z}}\{x[n]\}$	ROC: $r_{2}<\|z\|<r_{1}\$
Linearity	$a_{1}x_{1}[n]+a_{2}x_{2}[n]\$	$a_{1}X_{1}(z)+a_{2}X_{2}(z)\$	At least the intersection of ROC₁ and ROC₂
Time shifting	$x[n-k]\$	$z^{-k}X(z)\$	ROC, except $z=0\$ if $k>0\,$ and $z=\infty$ if $k<0\$
Scaling in the z-domain	$a^{n}x[n]\$	$X(a^{-1}z)\$	$\|a\|r_{2}<\|z\|<\|a\|r_{1}\$
Time reversal	$x[-n]\$	$X(z^{-1})\$	${\frac {1}{r_{2}}}<\|z\|<{\frac {1}{r_{1}}}\$
Conjugation	$x^{*}[n]\$	$X^{}(z^{})\$	ROC
Real part	$\operatorname {Re} \{x[n]\}\$	${\frac {1}{2}}\left[X(z)+X^{}(z^{})\right]$	ROC
Imaginary part	$\operatorname {Im} \{x[n]\}\$	${\frac {1}{2j}}\left[X(z)-X^{}(z^{})\right]$	ROC
Differentiation	$nx[n]\$	$-z{\frac {\mathrm {d} X(z)}{\mathrm {d} z}}$	ROC
Convolution	$x_{1}[n]*x_{2}[n]\$	$X_{1}(z)X_{2}(z)\$	At least the intersection of ROC₁ and ROC₂
Correlation	$r_{x_{1},x_{2}}(l)=x_{1}[l]*x_{2}[-l]\$	$R_{x_{1},x_{2}}(z)=X_{1}(z)X_{2}(z^{-1})\$	At least the intersection of ROC of X₁(z) and X₂( $z^{-1}$ )
Multiplication	$x_{1}[n]x_{2}[n]\$	${\frac {1}{j2\pi }}\oint _{C}X_{1}(v)X_{2}({\frac {z}{v}})v^{-1}\mathrm {d} v\$	At least $r_{1l}r_{2l}<\|z\|<r_{1u}r_{2u}\$
Parseval's relation	$\sum ^{\infty }x_{1}[n]x_{2}^{*}[n]\$	${\frac {1}{j2\pi }}\oint _{C}X_{1}(v)X_{2}^{}({\frac {1}{v^{}}})v^{-1}\mathrm {d} v\$

x[0]=\lim _{z\rightarrow \infty }X(z)\

, If

x[n]\,

causal

x[\infty ]=\lim _{z\rightarrow 1}(z-1)X(z)\

, Only if poles of

(z-1)X(z)\

are inside unit circle

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