[hpsdr] Crest Factor Reduction in conjunction with PureSignal

[Warren C. Pratt]

Hi Steve,

"Anyone", in this case, would most likely be me.  No, I have not 
considered it.  I'm not very familiar with digital modes; however, 
perhaps this would be useful as a low-distortion compression technique 
for some digital modes.

As far as what we currently have with PureSignal, the algorithm has no 
problem with peaks because they are totally constrained by the 
look-ahead ALC.  Then, to increase average power (decrease peak to 
average ratio) we have the Leveler and a compressor which works like an 
RF speech clipper.  All these, including the PureSignal correction, are 
applied at baseband.  The leveler and compressor introduce no material 
distortion in terms of IMD.

73,
Warren  NR0V

On 3/6/2014 2:52 PM, Steven B. Dick wrote:
> ***** High Performance Software Defined Radio Discussion List *****
>
>
>
> Has anyone considered the use of crest factor reduction in conjunction 
> with PureSignal? (or does Pure Signal already incorporate crest factor 
> reduction?)  See:
> http://www.altera.com/end-markets/wireless/advanced-dsp/cfr/wir-cfr.html
> Crest factor reduction is typically used in the cellular 
> communications industry in conjunction with digital predistortion. 
> Crest factor reduction eases the task of the digital predistorter and 
> allows inproved digital predistorter performance. Altera has a Crest 
> Factor Reduction reference design which employs nonlinear saturation 
> around the peaks to reduce the PAR.
> Regards,
> "Digital Steve", L1RF
>
>
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