[hpsdr] Predistortion and different types of amplifiers?

[Helmut, DC6NY]

Hi Rob,

the currently used algorithm for adaptive pre-distortion can effectively
improve IMD, independent of the type of amplifier (BJT, VMOS, LDMOS or tube)
or number of stages. The complete cascade will be linearized. Basically
there is also no restriction on higher supply voltage or typical behavior
without pre-distortion. Even class B amps can wonderfully linearized, which
reduces size and weight of necessary heat sinks.
The efficiency in the current software version is limited by the so called
‘memory effects’ of the intrinsic amplifier, caused by temperature
migration, charging/discharging processes, specific ferrite characteristics
etc. We find out that the modern LDMOS series up to 1 KW is very
‘cooperative’ regarding to our demands.
A lot of the wide TX noise Leif, SM5BSZ, is mentioning is also caused by
noisy PLL- VCOs and pre-distortion can’t solve this problem. So we are back
by the significant benefit of our DDC/DUP architecture: No analogue mixers
or VCOs are employed. Reciprocal mixing is no issue.

73, Helmut, DC6NY

-----Ursprüngliche Nachricht-----
Von: hpsdr-bounces at lists.openhpsdr.org
[mailto:hpsdr-bounces at lists.openhpsdr.org] Im Auftrag von Rob Frohne
Gesendet: Montag, 10. Februar 2014 22:08
An: HPSDR list
Betreff: [hpsdr] Predistortion and different types of amplifiers?

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