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Re: explaining i/q

From: David Hagood
Subject: Re: explaining i/q
Date: Tue, 3 Nov 2020 18:18:39 -0600
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I am sorrowful that you have decided you are going to stick with an explanation that is fundamentally incorrect. I know how direct conversion systems work - I design the software for them for a living. What you are basing your mental model on is an optimization for the case where the system is both sub-sampling the signal and going digital in the same operation. However, in many extremely high sample rate systems, the signal is brought down to baseband by mixing it with analog quadrature signals - that's the place where I and Q come from - and I assure you the only "delay by 90 degrees" is in the creation of the quadrature LO signals, not in the sampling of the actual data. But I've been around the Sun enough times to know that since you have decided upon this course and don't seem to want to change, there's no point in continuing to try to help.

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