To demodulate the multi-path signal
This task shows you how to demodulate the multi-path signal that you
loaded in the previous task.
1. Load the multi-path signal as instructed in the previous task.
2. Set demodulation parameters for this signal:
Press [
Instrument Mode
], [
demodulation setup
].
Press [
symbol rate
], 5 MHz.
Press [
alpha/BT], 0.15 [enter].
Press [
meas filter], [root raised cosine], [return].
Press [
ref filter], [raised cosine], [return].
Press [
result length], 500 [sym].
Press [
demod format], [QAM 16], [return].
Press [
Time], [points/symbol], 1,[enter].
3. Configure different displays for the demodulated data:
Press [
Display
], [4 grids
quad
].
Press
[A],[Measurement Data], [more choices], [channel frequency resp].
Press [
B], [P10equalizer impulse resp], [Data Format], [magnitude log(dB)].
P ress [C], [
Mea sure ment Data
], [symbol table/error summary]
Press
[D],[
Measurement Data
], [IQ measured time], [Data Format],
[
polar (IQ) constellation], [more format setup], [symbol dots].
4. Start the measurement:
Press [
Meas Restart
].
Traces A and B display the frequency response and the impulse response
of the equalization filter. You can view these displays even when you are
not using the equalization filter. In this example equalization is turned off,
therefore the equalization filter does not change and these displays remain
constant.
Traces C and D display the symbol table and constellation diagram for the
multi-path signal. The signal contains a significant amount of distortion
which makes it difficult to demodulate. The next task uses equalization to
compensate for distortion in the signal which significantly improves these
displays.
By default, the equalization filter is defined to have a unit impulse response
which yields a flat frequency response.
Using Adaptive Equalization (Options AYA and AYH)
12-4
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