Hi David, just my 2 cts. You will find in each datasheet of ADCs for RF apps the typical parameters SNR, SFDR, ENOB, max. sampling rate and bandwidth. The knowledge of these values, mostly relating to full scale and the Nyquist bandwidth, are sufficient to define a frontend including the necessary preamp, filtering and matching ADC to 50 ohms 'function blocks'. Together with your channel bandwidth you can provide a reliable estimation of MDS and dynamic range of the radio (my favorite direct sampling technique assumed, hi). It's good choice to calculate with a figure of about 50 dB for the ADC.
Walt Kester of AD wrote a couple of nice tutorials, e.g. http://www.analog.com/media/en/training-seminars/tutorials/MT-003.pdf 73, Helmut, DC6NY -----Ursprüngliche Nachricht----- Von: David Rowe [mailto:[email protected]] Gesendet: Dienstag, 27. Oktober 2015 20:47 An: [email protected] Betreff: [Freetel-codec2] gain before ADC Hello Glen/Matt, I'm working on a VHF radio prototype for testing some of my open source DV ideas. Could you pls explain how to work out the gain required in front of my ADC? For example if I have a MDS of -120dBm (0.224uV), and an ADC with a 3Vpp (1.06Vrms) clipping point, and SFDR of say 60dB. Is the gain rqd simply Av=1.06/0.224E-16? That would mean the minimum signal would hit full scale on the ADC. Perhaps we could scale that back by 60dB plus some margin such that the MDS is still a few dB above the floor of the ADC. I'm a bit mixed up by the idea of NF and ADCs. A worked example would help. Anyone else on the list with receiver design skills, pls feel free to comment. If a good reference exists I'm happy to dig that up. Thanks, David ---------------------------------------------------------------------------- -- _______________________________________________ Freetel-codec2 mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/freetel-codec2 ------------------------------------------------------------------------------ _______________________________________________ Freetel-codec2 mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/freetel-codec2
