Digital Signal Processing Reference
In-Depth Information
PM/FM Demodulation Scheme 2
HIL55F1.0/LPF0.2- 0.5
1.2
1.E+01
F
out
= 0.2
1
1.E+00
F
out
= 0.4
F
out
= 0.2
0.8
1.E-01
0.6
1.E-02
F
out
= 0.3
0.4
1.E-03
F
out
= 0.4
0.2
1.E-04
0
1.E-05
-0.2
1.E-06
0
20
40
60
80
100
0
0.2
0.4
0.6
0.8
1
Time / (Sampling Period)
Normalized Carrier Frequency,
F
1.E+00
0.25
F
out
= 0.35
F
out
= 0.5
1.E-01
0.2
0.4
1.E-02
0.15
1.E-03
0.3
0.1
1.E-04
0.05
1.E-05
F =0.35, 0.45, 0.55, 0.65
0
1.E-06
0.0001
0.001
0.01
0.1
1
0.1
1
10
100
1000
Modulation Frequency
Modulation Amplitude (degrees)
Notes:
(1)
Phase step response determined at carrier frequency F of 0.5.
(2)
All frequencies and bandwidths normalized with respect to the Nyquist frequency.
ac phase error carried out for modulation amplitude of 30
o
for carrier frequency, F.
(3)
Maximum dc phase error found when the phase input is dc and varies from 0
o
to 90
o
for each carrier
frequency shown.
(4)
(5)
All filter lengths are 55 using
HIL55F1.0
, and a delay of L/2 (= 27) for path through LPF1 in Scheme 2
along with output
LPF55F0.2 - 0.5
.
2
2
, where noise amplification factor
(6)
Output noise power
σ
ϕ
≈
ησ
ε
η
= 0.8 (F
out
= 0.2),
η
= 1.2 (F
out
= 0.3),
2
10 deg
2
(0.175 rad
2
).
and
η
= 1.6 (F
out
= 0.4), provided input noise power,
σ
ε
≤
(7)
Empirical relation between bandwidth
B
dem
and modulation amplitude
ϕ
o
for carrier frequency
F
= 0.5, and for F
out
= 0.5.
−
0
019
ln
ϕ
−
0
.
266
B
≈
0
236
ϕ
o
o
dem
