Difference between revisions of "Dvb constellation"

From LinuxTVWiki
Jump to: navigation, search
(Build DVB constellation in Linux)
 
m (add some links)
 
(6 intermediate revisions by one user not shown)
Line 1: Line 1:
 +
Patches for Linux kernel (v4l code) and for v4l-utils should be applied to obtain I&Q constellation described in this article.
 +
 +
Patch for Linux kernel:
 +
http://stand.netup.tv/downloads/iq_constellation.patch
 +
 +
Patch for v4l-utils:
 +
http://stand.netup.tv/downloads/iq_constellation_v4l-utils.patch
 +
 
== Receiving I&Q data from DVB demodulator ==
 
== Receiving I&Q data from DVB demodulator ==
  
Line 27: Line 35:
  
 
resulting image will be saved into iq_dvbc_qam256.png. Here is example of images received with [[NetUP_Dual_DVB_T_C_CI_RF|NetUP Dual DVB-T/C-CI RF]] and [[NetUP_Dual_DVB_S2_CI|NetUP Dual DVB S2 CI]] cards.
 
resulting image will be saved into iq_dvbc_qam256.png. Here is example of images received with [[NetUP_Dual_DVB_T_C_CI_RF|NetUP Dual DVB-T/C-CI RF]] and [[NetUP_Dual_DVB_S2_CI|NetUP Dual DVB S2 CI]] cards.
 +
 +
<gallery>
 +
File:Iq_dvbc_qam16_38db.png|QAM16 constellation (DVB-C)
 +
File:Iq_dvbc_qam64_38db.png|QAM64 constellation (DVB-C)
 +
File:Iq_dvbc_qam128_38db.png|QAM128 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>
 +
 +
== Also See ==
 +
* [[Quadrature Amplitude Modulation]]
 +
* [[Quadrature Phase Shift Keying]]
 +
 +
== External links ==
 +
 +
[http://en.wikipedia.org/wiki/Constellation_diagram] Constellation diagram
 +
 +
[http://www.cisco.com/en/US/prod/collateral/video/ps8806/ps5684/ps2209/prod_white_paper0900aecd805738f5.html] Digital Transmission: Carrier-to-Noise, Signal-to-Noise & Modulation Error Ratio

Latest revision as of 22:08, 12 May 2013

Patches for Linux kernel (v4l code) and for v4l-utils should be applied to obtain I&Q constellation described in this article.

Patch for Linux kernel: http://stand.netup.tv/downloads/iq_constellation.patch

Patch for v4l-utils: http://stand.netup.tv/downloads/iq_constellation_v4l-utils.patch

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.

Also See

External links

[1] Constellation diagram

[2] Digital Transmission: Carrier-to-Noise, Signal-to-Noise & Modulation Error Ratio