Am 25.08.19 um 10:52 schrieb Hal Murray:
[email protected] said:
As you have always two channels, I would recommend to use two mixers fed with
an LO that is 90°C out of phase to get I and Q components.
How does that compare with running a single channel twice as fast?
At low enough frequencies, the two ways are identical in performance
and linked by the Hilbert transform.
At high enough frequencies, ADC performance starts to suffer. One gets
a smaller "effective number of bits" ENOB as sample rate and/or input
frequency rise.
In that region one may gain an advantage by halving the sample rate
at the cost of doubling the hardware and needing a Hilbert transformer,
also known as a wideband 90° phase shifter. The phase shift
might come cheap, depending on the upstream processing.
One could also time-interleave 2 ADCs or even more. Some ADC chips
do that internally, and some scopes, too.
regards, Gerhard.
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