And As the spectrum of the discrete time sign, this exact same spectrum will periodically repeat if we prolonged the frequency larger outside of $f_s$ these types of which the spectrum revealed is additionally the same spectrum in every single frequency band from $nf_s$ to $(n+one)f_s$ for any integer $n$. https://sites.google.com/view/pg-in-sector-15-gurugram/book-modern-pg-for-boys-in-gurgaon