Difference between revisions of "Dvb constellation"

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File:Iq_dvbc_qam128_38db.png|QAM128 constellation (DVB-C)
 
File:Iq_dvbc_qam128_38db.png|QAM128 constellation (DVB-C)
 
File:Iq_dvbc_qam256_36db.png|QAM256 constellation (DVB-C)
 
File:Iq_dvbc_qam256_36db.png|QAM256 constellation (DVB-C)
 +
</gallery>
 +
 +
<gallery>
 +
File:iq_dvbs2_32apsk.png|32APSK constellation (DVB-S2)
 +
File:iq_dvbs2_16apsk.png|16APSK constellation (DVB-S2)
 +
File:iq_dvbs2_8psk.png|8PSK constellation (DVB-S2)
 +
File:iq_dvbs2_qpsk.png|QPSK constellation (DVB-S2)
 
</gallery>
 
</gallery>

Revision as of 17:53, 11 May 2013

Receiving I&Q data from DVB demodulator

dvb_const -f /dev/dvb/adapter0/frontend1 -o iq_dvbc_qam256.txt -p 100000

received data (100000 points) will be saved into iq_dvbc_qam256.txt file. File format is simple text csv. Example of received data:

-175,-45
-46,110
-241,-178
176,11
-50,173
16,44

Values are signed. First I part, second Q part.

Visualization of received data

dvb_const_plot utility build PNG image with constellation:

dvb_const_plot -i iq_dvbc_qam256.txt -o iq_dvbc_qam256.png -c "SNR=38dB QAM256" 

resulting image will be saved into iq_dvbc_qam256.png. Here is example of images received with NetUP Dual DVB-T/C-CI RF and NetUP Dual DVB S2 CI cards.