Advantages and disadvantages of waveform filtering by DSP in oscilloscopes
By Johnny Hancock
All of today's high-speed real-time sampling oscilloscopes apply various forms of digital signal processing (DSP) to the digitized waveforms. Some engineers are concerned that software filtering of digitized data could alter the true nature of the captured signal. However, the captured waveform is nothing more than a representation of the actual input signal and the digitized data, as captured by the oscilloscope, which itself presents certain alterations and distortions caused by the first stage of filtering. -do of the oscilloscope hardware. Ideally, oscilloscopes should have infinite sampling rate, perfectly flat frequency response, linear phase response, zero noise, and unlimited bandwidth. But, in practice, they have hardware limitations that cause errors. Precisely, DSP filtering can correct those errors induced by the hardware and, in this way, improve the accuracy of the measurements and the quality of the representations on the screen. 
