[hpsdr] Hardware pre distortion?

[Helmut]

Hi Chris,

Obviously you are not completely satisfied with Red Pitaya, the modified
PowerSDR and PS. That’s no big surprise, but it’s a much better approach for
linearization than that (strange) ‘hardware solution’.
The efficiency of predistortion depends on the measurement precision of the
actual TX signal and the reference TX signal or in other words the
measurement dynamic range. Otherwise you can‘t precisely take correction.
‘Dynamic losses’ due to the necessary up/down conversion reduce the
efficiency of predistortion dramatically. High losses in the Red Pitaya
DDC/DUC paths limit the great performance of Warren’s PS algorithm. As the
losses are 4 times more than in Hermes, I guess the improvement of IMDR
results only on a limited correction in the upper part of the amp transfer
characteristic. This also explains your observation of critical feedback
levels.  An improvement/correction at low levels seems very difficult, so
you should at least operate your amp with a high quiescent current.
 
73, Helmut, DC6NY

-----Ursprüngliche Nachricht-----
Von: Hpsdr [mailto:hpsdr-bounces at lists.openhpsdr.org] Im Auftrag von Chris
Wilson
Gesendet: Dienstag, 28. Juni 2016 15:49
An: 'OpenHPSDR'
Betreff: [hpsdr] Hardware pre distortion?

***** High Performance Software Defined Radio Discussion List *****

28 June 2016


I hope this is a suitable question for this group? I am messing with a
Red  Pitaya  experimental  board  and  a  special version of OpenHPSDR
software  that  allows  pre distortion using "PureSignal" and it works
very  well  once  the  feedback levels are set correctly. But i am now
wondering  what the state of play is with hardware pre distortion that
is software independent? Anyone got any info on this please? Thanks.



-- 


Best regards,
 Chris                            mailto:chris at chriswilson.tv

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