[hpsdr] Pre-Distortion

[Helmut, DC6NY]

Hi Dan,

Many thanks for your really interesting input, absolutely not silly. A lot
of additional features seem conceivable, but this simple sampler should just
be an inexpensive hardware component for folks to get the pre-distortion
technology started. I’m pretty sure that the existing hardware and
especially the SWR bridges on the different amplifier/LPF boards like Alex
or Anan will be modified soon to allow internal as well external use for
pre-distortion feed-back.
I think it’s very important to sensibilize folks for this smart ‘Pure signal
philosophy’, only available in an economic way with our state-of-the-art SDR
architecture. Since decades suppliers compete with funny 1 or 2 dB more of
RX IP3 of the radios and neglect the spectrum quality of the TX signal
completely. Pre-distortion will hopefully be a milestone in ham radio
applications.
Concerning to Vdd tracking: We are experimenting since some time with class
E amps and EER techniques. The necessary PWR signal representing the
SSB-envelope is already generated in the FPGA thanks Alfred, HB9EPU, and a
PWM power amp together with the LP is also built. This will be the next
challenge to get pre-distortion and EER efficiency married.

In every case things stay exciting.

73, Helmut, DC6NY

-----Ursprüngliche Nachricht-----
Von: hpsdr-bounces at lists.openhpsdr.org
[mailto:hpsdr-bounces at lists.openhpsdr.org] Im Auftrag von Dan Mills
Gesendet: Sonntag, 8. Dezember 2013 15:40
An: hpsdr at lists.openhpsdr.org
Betreff: Re: [hpsdr] Pre-Distortion

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

Silly question, but would it be worthwhile to modify the sampler to give
both current and voltage sample outputs?
That way folks with a dual adc rx can use it to measure the impedance seen
at the point the sampler is inserted and things like gamma, RL and SWR can
be trivially calculated.

It would even allow for some tricks like say making the PA drain voltage
track the value of |Z| so that the amplifier always operates at a drain
voltage corresponding to full power into the actual load impedance
presented. Making the drain voltage track the modulation envelope is harder
but also offers worthwhile efficiency improvements.


Just a thought.

73 M0HCN.
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