Reconstruction Filter

The filter used in a digital to analog converter that eliminates the stair-stepped waveforms created in the digital sampling process and restores frequency, amplitude, and phase of the original signal. The process of digital sampling creates stair-stepped waveforms that resemble square waves (increasingly so at higher frequencies). These waveforms contain the original signal, but also have high frequency noise and harmonics added to it. The reconstruction filter – which is basically a low pass filter – removes all of the high frequency signal above the Nyquist frequency that was induced because of the sampling process, leaving a “smooth” sinusoidal type waveform resembling the signal that was originally sampled.