The 3 dB bandwidth of an electronic filter or communication channel is the part of the system's frequency response that lies within 3 dB of the response at its peak, which in the passband filter case is typically at or near its center frequency, and in the lowpass filter is near 0 hertz.
32.
The scaling by " T ", which arises naturally by time-scaling the delta function, has the result that the mean value of " x s " ( " t " ) is equal to the mean value of the samples, so that the lowpass filter needed will have a DC gain of 1.
33.
For instance, the equivalent baseband waveform can be created without explicitly computing \ hat s ( t ), by processing the product sequence, \ left [ s ( nT ) \ cdot e ^ {-j 2 \ pi \ frac { B } { 2 } Tn } \ right ], through a digital lowpass filter whose cutoff frequency is B / 2.
34.
The process of creating a DSD signal is conceptually similar to taking a one-bit delta-sigma analog-to-digital ( A / D ) converter and removing the decimator, which converts the 1-bit bitstream into multi-bit PCM . Instead, the 1-bit signal is recorded directly and, in theory, only requires a lowpass filter to reconstruct the original analog waveform.
35.
In this particular example, the sample mapped to the keyboard via the keymap block does not sound; instead a sawtooth wave will be combined with another sawtooth wave and fed through the " shaper " ( which, in essence, allows one wave to frequency modulate another ), then through a 2-pole lowpass filter with a fixed resonance, and finally through two gain stages to the output.
