Digital Signal Processing Reference
In-Depth Information
0,00275
0,00250
0,00225
0,00200
0,00175
0,00150
0,00125
0,00100
0,00075
0,00050
0,00025
0,00000
200
150
100
50
0
-50
-100
-150
-200
Amplitude Spectrum
4, 0
Impulse response
3, 5
3, 0
2, 5
Phase Spectrum
2, 0
1, 5
1, 0
0, 5
0, 0
750
1000
1250
1500
1750
2000
2250
2500
0. 0
5. 0
10. 0
15. 0
20. 0
25. 0
30. 0
35. 0
Hz
ms
0, 0015
Locus curve
0, 00015
Locus curve
0, 0010
0, 00010
0, 00005
0, 0005
Z
oom
0, 00000
0, 0000
-0, 00005
-0, 00010
-0,0005
GAUSSian plane
-0, 00015
-0,0010
-0, 00020
- 0, 00015
X/Y-Grafik 1
- 0, 00010
-0,00005
0, 00000
0, 00005
0, 00010
0, 00015
V
-0,0015
-0,0015
X/Y-Grafik 1
-0,0010
-0,0005
0, 0000
0, 0005
0, 0010
0, 0015
V
Illustration 220:
Forms of representation of the transfer function of digital filters
Top left you will first see the
-pulse and the impulse response of the bandpass filter at the filter imput, top
right the amplitude and phase response of the transfer function. These two representations contain the
same information as the representation of the transfer function as a locus (below), provided the frequency
of each measurement point is known.
δ
Within the filter pass band the full angle 360
0
or 2
is traversed about 24 times. This can be seen from the
the phase curve to the top right, where a corresponding number of "hops" from 180
0
to -180
0
, or
π
π
can be be identified (both angles are identical!). Thus, the locus traverses this full angle 32 times. Due to
the ripple of the filter curve the curve is not exactly circular, but fluctuates slightly. The width of this "tube"
points to the ripple of the filter graph.
π
to
-
The locus always represents the positive and negative frequency band, which reflects (horizonzale) symme-
try of the axes? More detailed information about this illustration can be found in the text.
