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DVB-T expanded/compressed signal AD8318 rms level detection

Question asked by asoler77 on Sep 26, 2012
Latest reply on Oct 4, 2012 by enash

Dear Sirs,

 

We are experiencing errors on detection of UHF DVB-T signal by means of AD8318. Below you will find two CCDF measurements of two signals with the same rms value (measured with oscilloscope and wattmeter). The output of AD8318 is mistaking -0.75dB with slow video bandwidth (CPLF=1nF) and also with fast video bandwidth (CLPF=8p2 and post averaging). The error is reproduced on the whole dynamic range of the logarithmic detector.

 

Any help will be appreciated.

 

Albert

 

Expanded dvb-t signal:

expanded_dvb-t_signal.png

 

Linear dvb-t signal:

linear_dvb-t_signal.png

 

Circuit diagram of AD8318:

 

detlog.png

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