DSP A Khoa học máy tính quan điểm P4

The concept of frequency is clearest for simple sinusoids, but we saw in the previous chapter that it can be useful for nonsinusoidal periodic signals as well. The Fourier series is a useful tool for description of arbitrary periodic signals, describing them in terms of a spectrum of sinusoids, the frequencies of which are multiples of a basic frequency. It is not immediately obvious that the concepts of spectrum and frequency can be generalized to nonperiodic signals.