Digital Signal Processing Reference
In-Depth Information
Figure 8.1
Illustration of the fact that the phase angle of the signal, downconverted by aliasing,
depends on the phase of the sampling point process
point process. Attention is drawn to the fact that the phase shift of the sampling
point process affects only the overlapping aliases. Variations of this phase do
not affect the contribution of the true signal component to the Fourier coefficient
estimate at all. There are at least two significant consequences of that:
1. The phase of the periodic sampling point process affects the waveforms
reconstructed from the obtained signal sample values.
2. Using variable phase periodic sampling opens up the possibility of avoiding
overlapping of the aliasing frequencies.
How this possibility might be realized is discussed in Chapter 10. Before studying
this essential issue in some detail, variation of the complementary waveforms of
signal components at frequencies belonging to the row of the aliasing frequencies
mf
s
f
x
will briefly be considered. The diagrams shown in Figure 8.2 illustrate
this kind of waveform variation, which take place when they are reconstructed
∓
