[hpsdr] predistortion

[John Marvin]

Does this mean that you can run an LDMOS based amp without any form of 
low pass filters after the final stage and still remain within FCC 
regulations?

John
AC0ZG

On 5/8/2013 1:15 AM, Helmut, DC6NY wrote:
> ***** High Performance Software Defined Radio Discussion List *****
>
> Hi Frank,
>
> Warren developed a fantastic highlight for the HPSDR stuff, which is more
> worth than different other features.  Indeed LDMOS devices are easier to
> tame with predistortion than BJT or TMOS due to less ‘memory’ behavior.
> Typical for my new 250 W amp using the Freescale MRFE6VP6300HR:  28 dB gain@
> 50V Vdd, Iq=1,5A, IM3 < -60 dB on all band between 2 -50MHz. DL9SM, who is
> developing a 500W single-stage LDMOS amp got similar results.
> If people are interested I’ll try to put details of the amp on hamsdr.com.
>
> 73, Helmut, DC6NY
>
> -----Ursprüngliche Nachricht-----
> Von: hpsdr-bounces at lists.openhpsdr.org
> [mailto:hpsdr-bounces at lists.openhpsdr.org] Im Auftrag von Warren C. Pratt
> Gesendet: Mittwoch, 8. Mai 2013 02:04
> An: 'FRANCIS CARCIA'; 'HPSDR List'
> Betreff: Re: [hpsdr] predistortion
>
> ***** High Performance Software Defined Radio Discussion List *****
>
> Hi Frank,
>
> I already have pre-distortion up and running in prototype form--using
> full-duplex to collect the information to calculate the correction.  Samples
> are continually collected during transmissions and correction is
> re-calculated at intervals as desired.  There are still a few rough edges to
> work out; however, testers with 50V LDMOS amplifiers are seeing typical
> reductions of IMD from about -30dB (without pre-distortion) to about -60dB
> (with pre-distortion).  12V FET and bipolar amplifiers are considerably more
> difficult to correct as they typically have a much higher level of thermal
> and supply-related memory effects.  There is a special configuration
> required in firmware to facilitate collection of the samples; however, I've
> implemented all the core algorithms in software--I can do the job much more
> simply and precisely there than in firmware.
>
> This is still prototype--not sure yet about a release plan.
>
> 73,
> Warren  NR0V
>
>
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