Frequency Domain Representation

From the above discussion, we can say that a periodic signal whose Fourier Series Expansion exists, can be represented uniquely in terms of it's Fourier co-efficients. These co-efficients correspond to a particular multiples of the fundamental frequency of the signal. Thus, the signal may be equivalently represented as a discrete signal on the frequency axis:

This is called the Frequency domain representation of the signal.

We next discuss the conditions under which the Fourier Expansion is valid.