To demodulate and analyze an MSK signal
This example uses an MSK signal from the Signals Disk to show you how
to demodulate an MSK signal and view MSK phase transitions.
1. Load “MSK.DAT” from the Signals Disk into the arbitrary source:
Perform steps 1, 2, and 3 in ‘’To prepare a digital demodulation
measurement.’’ For step 2, load the “MSK.DAT” signal from the Signals
Disk instead of ‘’PI4DQPSK.DAT.’’
2. Select appropriate setup parameters:
Press [
Range] and select the optimum range.
Press [
Frequency
], [
center
], 5, [
MHz
]
Press [
span
], 1, [
MHz
].
Press [
Trigger
], [
trigger type
], [
internal source
], [
return
], [
ch1 delay
], 74, [
us
].
If you don’t know how to select the optimum range, see ‘’To prepare a
digital demodulation measurement.’’
3. Demodulate the signal:
Press [
Instrument Mode
], [
Digital Demodulation
] (with option AYH, press
[
Instrument Mode
], [
demod type
], [
Digital Demodulation
], [
Return]).
When you turn on digital demodulation, you may see this message:
Maximum span limited by symbol rate and maximum span/symbol rate ratio.
This message informs you that the frequency span is limited by the
currently selected symbol rate. In other words, the symbol rate used in
the last digital demodulation measurement is too small. The next step
automatically selects the correct symbol rate and restores the frequency
span to 1 MHz, so you can ignore this message. For additional details
about symbol rate and frequency span interactions, see ‘’Parameter
Interactions’’ in the Digital Demodulation Concepts chapter.
4. Configure the digital demodulator for a GSM measurement:
Press
[demodulation setup
], [
demod format
], [
standard setups
], [
GSM
]
Press [
Time
], [
pulse off
], [
sync off]
5. Format traces A and C to view unwrapped phase versus group delay:
Press [
A
]
Press [
Data Format
], [
phase unwrap]
Press [
Display
], [
view/overlay traces
], [
C on
]
Press [
C
], [
Measurement Data
], [
IQ measured time
], [
Data Format
], [
group delay
]
Press [
Shift
], [
A
], [
more format setup
], [
symbols dots
]
Press [
Auto Scale
]
Using Digital Demodulation (Opt. AYA)
8 - 14
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