Warren, this wonderful! Thank you!
You have set my brain racing!
Don't learn to code... Learn to think!
> On Oct 18, 2014, at 9:29 PM, Warren C. Pratt <warren@wpratt.com> wrote:
>
> Greetings,
>
> I sometimes monitor this list and I see that the topic of pre-distortion is
> appearing recently in several posts. I wrote the pre-distortion software
> that was released a few months ago as part of the openHPSDR (open High
> Performance Software Defined Radio) program. I'll offer just a few
> observations:
>
> ** It seems to me that it's probably much easier to optimally implement
> pre-distortion in a DDC/DUC (digital up-conversion / digital down-conversion)
> software defined radio than in other radios. There are simply very few
> places that errors can creep into the required processing. The required
> precision and accuracy increase exponentially as the desired reduction in IMD
> increases. So, having few error sources and the benefit of double-precision
> floating point become important.
>
> ** 50V LDMOS amplifiers are probably the "most correctable" solid state amps.
> Tube type amps also correct very well. 13.8V amps are more difficult due to
> "memory effects."
>
> ** No problem to correct an entire amplifier chain, at legal limit. No extra
> hardware or software is required. One just feeds back a sample of the output
> from the last stage to calculate the correction.
>
> ** You cannot successfully correct by pre-distorting the MIC input to a radio
> UNLESS you have VERY wide bandwidth from the MIC through the entire
> transmitter. The IMD frequencies that you want to correct must be within the
> bandpass of the correction path.
>
> At Ham Radio Friedrichshafen this past June, I gave a talk (approx. 30 min.)
> on the openHPSDR solution for pre-distortion. It's posted on the openHPSDR
> web site. If any are interested, here's a link:
>
> "*Warren Pratt,*NR0V, 2014.Digital Predistortion linearizes RF amplifiers
> <http://video.openhpsdr.org/HRF2014/PureSignal1.2.mp4>(MP4)"
>
> This link is posted on the <openHPSDR.org> website on the Publications page.
> The video includes a few examples of amplifiers where this technology has
> been applied.
>
> I hope this helps explain a little more about this technology and sparks more
> interest in finding ways to reduce IMD!
>
> 73,
> Warren NR0V
>
> _______________________________________________
> Amps mailing list
> Amps@contesting.com
> http://lists.contesting.com/mailman/listinfo/amps
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|