MSK (Minimum Shift Keying) CML Microcircuits, MSK (Minimum Shift Keying) Datasheet - Page 2

• Manufacturer Part Number: MSK (Minimum Shift Keying)
• Description: Minimum Shift Keying and its Application to Wireless Data Transmission
• Manufacturer: CML Microcircuits

MSK and its Application to Wireless Data Transmission
continuous phase modulation (CPM) minimize BW consumption by eliminating phase discontinuities. CPM state changes
are represented by non-abrupt changes in phase and frequency while the amplitude of the carrier envelope remains
constant (i.e. phase modulation or frequency modulation).
1.2 Theory of Continuous Phase Modulation
The simplest form of constant envelope modulation is binary FSK. This type of modulation is composed of two sinusoids
and
system would appear as shown in Figure 1.
between the phase of
example of non-coherent FSK ( f
where bandwidth efficiency is not an issue.
or frequency modulator. The key aspect of the VCO is, for instantaneous frequency deviation proportional to the
modulating signal m(t) , the phase must be proportional to the integral of the modulating signal. In mathematical terms
where,
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Where s
This type of FSK is referred to as “discontinuous phase” or “non-coherent” FSK because there is no coherence
An alternative method, to that depicted in Figure 1, for generating FSK is to use a voltage controlled oscillator (VCO)
e(t) = modulated carrier (FM is a type of angle modulation)
A
(t) =
C
C
C
(t) = instantaneous phase angle due to the modulating signal m(t) .
= initial carrier phase angle
= amplitude of unmodulated carrier
= angular frequency of unmodulated carrier
1
( t ) is selected for a logic zero and s
C
t +
C
+ (t)
1
,
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2
and the modulating signal (BINARY DATA IN). CCITT standard V.21 (300 baud) is an
1
= 1080 Hz and f
cos
cos
Figure 1:Discontinuous phase FSK modulator.
1
2
t
t
e t
( )
Re{
2
s t
s t
( t ) is selected for a logic one. An implementation of the this type of FSK
2
1
2
= 1750 Hz) it has also been applied to other low data rate systems
BINARY DATA IN
( ) cos
( )
A
C
exp[ ( )]}
2
cos
j t
1
2
t
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t
.
Fax: [phone]
OUTPUT
FSK
Doc. # 20830084.001
(1)
(2)
(3)
APPLICATION