MSK (Minimum Shift Keying) CML Microcircuits, MSK (Minimum Shift Keying) Datasheet - Page 28

• 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
I/O, Variables and Constants
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PSEUDO-CODE
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3.3.2.2 FM Discriminator Model
A simple heterodyne discriminator model based on Figure 35 can be built with multipliers, delays and filters. Pseudo-code
is shown for the mixer and the discriminator.
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4800 Bethania Station Road, Winston-Salem, NC 27105-1201 USA
input[ ]
output[ ]
IntIn = 0
step
carrier
deviation
step =
for j=0 to M-1 {
c
d
IntIn = IntIn + input[i-1] + step j ;
output[M i + j] = sin
}
2
2
input[i] input[i -1]
carrier
M
carrier deviation
INPUT
// input sequence
// output sequence
// variable used to store integral of input[] sequence up to current time.
// difference between consecutive input samples normalized to interpolation rate M.
// FM carrier frequency normalized to interpolation rate M
// FM deviation frequency normalized to carrier frequency.
// M times input sample rate
// use linear interpolation between input samples
M
M
// run for each sample, output sample rate is
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local
;
MIXER
osc
X
// carrier frequency constant
// deviation frequency constant
c
Figure 36: Heterodyne Discriminator Block Diagram.
(i M
j)
BPF
Pseudo-Code Listing 8 Mixer
IF
d
// simple integrator
IntIn ;
28
DISCRIMINATOR
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T
X
90
Fax: [phone]
LPF
OUTPUT
Doc. # 20830084.001
APPLICATION