विविक्त-समय इकाई चरण संकेत (discrete-time unit step signal) u(n) का z-रूपांतरण (z-transform) क्या है?

The Fourier transform of a unit impulse function δ(t) is:

The region of convergence (ROC) of the Z-transform of the signal x(n) = 2n u(n) is:

Autocorrelation of a signal measures the similarity of the signal with ____________.