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TABLE 7–2
COMPARISON OF ANALOG SIGNALING TECHNIQUES a
Type
Linearity
Transmission
Bandwidth
Required b
(S>N) out
(S>N) baseband
Comments
Baseband L B 1 (7–84) No modulation
ƒ ƒ
AM L c 2B
m 2
1 + m 2 (7–90) Valid for all (S/N) in with
coherent detection; valid
above the threshold for envelope
detection and m(t) … 1
DSB-SC L 2B 1 (7–98) Coherent detection required
SSB L B 1 (7–105) Coherent detection required;
performance identical to
baseband system
PM NL 2(b p + 1)B
b 2 p a m 2 (7–120) Coherent detection required; valid
b
V
for (SN) in above the threshold
p
FM NL 2(b f + 1)B
FM with deemphasis NL 2(b f + 1)B
3b 2 f a m 2 (7–130) Valid for (SN) in above the threshold
b
V p
b 2 f a B 2
b a m 2 (7–140) Valid for (SN) in above the threshold
b
f 1 V p
PCM NL d M 2 (SN) baseband
(7–82) Valid for (SN) in above the
threshold (i.e., P e S 0)
a B, absolute bandwidth of the modulating signal; f 1 , 3-dB bandwidth of the deemphasis signal; L, linear; m = m(t) is the modulating signal; M = 2 n , number of
quantizing steps where n is the number of bits in the PCM word; NL, nolinear; V p , peak value of m(t); b p , PM index; b f , FM index.
b Typical bandwidth specifications by ITU are larger than these minima [Jordan, 1985].
c In the strict sense, AM signaling is not linear because of the carrier term. (See Table 4–1.)
d The bandwidth depends on the type of digital system used (e.g., OOK and FSK).
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