And because the spectrum of the discrete time signal, this similar spectrum will periodically repeat if we prolonged the frequency higher beyond $f_s$ these that the spectrum shown is usually a similar spectrum in each individual frequency band from $nf_s$ to $(n+1)f_s$ for virtually any integer $n$. 知乎，让每一次点击都充满意义 —— 欢迎来到知乎，发现问题背后的世界。 https://boyspgsector15ingurgaon.blogspot.com/