2. 2. 4 Frequency representation of periodic signals FOurier series can be used to approximate a signal sin t (sint+asin3t) 0丌 3t+-sin5t) Fig. 2. 13 Approximations of a square wave signal using sums of partial terms of Fourier series❑Fourier series can be used to approximate a signal. 2.2.4 Frequency representation of periodic signals Fig. 2.13 Approximations of a square wave signal using sums of partial terms of Fourier series