[hpsdr] Closing the loop.....

[Warren C. Pratt]

Hi Dan,

There are a couple of us that are playing with pre-distortion linearization:
myself and Pete, W6XX.  It requires some care in the amplifier hardware
design with regard to memory effects.  It's still experimental; however,
we're getting quite good results on some prototype amplifier hardware that
Pete has built, currently taking IMD from roughly 30dB down to roughly 60dB
down.  The pre-distortion algorithm is implemented in software--I've done
that part.  There's also a matter yet to be resolved with regard to matching
outbound and inbound samples for adaptive calibration.  That should be
solvable with some software and firmware work.  We could also move the
algorithm to firmware; however, we'd clearly need to give up some precision
compared to what we're doing now.

I suppose the Cartesian algorithm would need to be totally in firmware as
the delays from software to hardware and back are somewhat lengthy and are
not fixed.

73,
Warren  NR0V

-----Original Message-----
From: hpsdr-bounces at lists.openhpsdr.org
[mailto:hpsdr-bounces at lists.openhpsdr.org] On Behalf Of Dan Mills
Sent: Sunday, October 21, 2012 2:57 PM
To: OpenHPSDR
Subject: [hpsdr] Closing the loop.....

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

Just wondering if anyone else out there is playing with cartesian feedback
for PA linearisation (And/Or drain supply envelope tracking), with DUC/DDC
radios?



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