Radio WC6W wrote:
> Back to HF, the DSP provides limiting to create the
> phase signal which is sent through the exciter at a
> constant (30 watt) level. This will avoid the AM to
> PM problem.
>
> This is basically the Kahn EER scheme, from 1952,
> kluged to run with a typical transceiver in the signal
> chain. If it worked back then, it should still work
> now!
Sorry, I should have said the AM/PM I was thinking of was in the
varactor effect in the semiconductor junctions when the output
stage drain/collector voltage was modulated. I suspect that it
would generate some distortion components.
Some of the original polar/cartesian loop designs were done on hf
transmitters, round the tx system after the (conventional) ssb
generator, so there weren't any narrow filters to introduce
delays. It's something like 25 years since I did a prototype
system for a mil manpack. It didn't use EER, but could have. In
the end, the efficiency savings were outweighed by extra cost,
complexity and functional problems. I imagine it would be
different today.
Regarding class E PAs - some of the efficiency gain is lost of
they are designed with enough margin to withstand mismatch, even
just for long enough for protection circuits to operate.
Steve
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