On Mon, 16 Feb 2004 00:18:49 GMT, "W3JDR" wrote:
I think it boils down to something very practical:
If you want good spectral purity, then you need to bandpass filter the
output of the multiplier. It becomes a matter of how close and how large the
undesired spectral components are compared to the desired spectral
components. After that, you can consult your filter design charts to
determine how complex a filter will be required and whether it's physically
realizable.
As an example, a x4 multiplier stage will have a desired output at Fin x 4,
and close-in undesired products at Fin x 3 and Fin x 5. This means the
output bandpass filter has to be able to attenuate signals at +/-25% of the
center frequency sufficiently to meet the desired spectral purity. In
practice with simple single-ended multiplier designs, a x4 multiplier is
approaching the threshold of realizability for high purity applications
(40-60 dB purity). It is possible to make push-pull and push-push
multipliers that have better output purity, but these techniques are seldom
used.
Joe
W3JDR
[snip]
I would think a "W3JDR" would know that even harmonics are *much*
harder to obtain in nonlinear multipliers.
...Jim Thompson
--
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