Flatness

Flatness is an effect on the acquired waveform that is frequency dependent. As the frequency rises, the amplitude slowly falls toward the 3 dB cutoff point of the bandwidth. When signals are composed entirely of frequencies below this cutoff point, the measured signal can appear slightly different than the input signal. The higher frequency components of the signal are attenuated more than the lower frequency components, changing the overall signal. Flatness describes how well the analog front end passes signals of different frequencies. A maximally flat front end passes all frequencies with the same amount of attenuation, so the measured signal looks like the input signal. However, in the real world, as the frequency rises, the measured input signal slowly falls toward the –3 dB point.