Difference between revisions of "Dvb constellation"

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File:Iq_dvbc_qam16_38db.png|QAM16 constellation
File:Iq_dvbc_qam16_38db.png|QAM16 constellation (DVB-C)
File:Iq_dvbc_qam64_38db.png|QAM64 constellation
File:Iq_dvbc_qam64_38db.png|QAM64 constellation (DVB-C)
File:Iq_dvbc_qam128_38db.png|QAM128 constellation
File:Iq_dvbc_qam128_38db.png|QAM128 constellation (DVB-C)
File:Iq_dvbc_qam256_36db.png|QAM256 constellation
File:Iq_dvbc_qam256_36db.png|QAM256 constellation (DVB-C)

Revision as of 17:19, 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:


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.