So did that answer your question?
[image: Mailtrack] <https://mailtrack.io?utm_source=gmail&utm_medium=signature&utm_campaign=signaturevirality5&;> Sender notified by Mailtrack <https://mailtrack.io?utm_source=gmail&utm_medium=signature&utm_campaign=signaturevirality5&;> 11/03/20, 08:23:36 AM On Tue, Nov 3, 2020 at 7:50 AM Anon Lister <listera...@gmail.com> wrote: > I always come back to the Lyons explaination: the pictures really help for > the visual learners among us. If you did a workshop I’d definitely include > a link to this in reference material: > > http://www.dspguru.com/files/QuadSignals.pdf > > There’s actually some of us who don’t come from formal electrical > engineering backgrounds who learned this first and find equations and such > more difficult when expressed in the “real“ interpretation of a signal. Heh. > > > > On Nov 2, 2020, at 18:06, Kristoff <krist...@skypro.be> wrote: > > Hi all, > > I was watching the webinar of Heather on GNU Radio today, when it came to > me that one of the most difficult part doing a presentation of GNU Radio is > the data-types, .. and especially these 'complex numbers'. > The problem, or at least for me, is that when you mention 'GNU Radio > complex numbers', you also have to mention iq-signals, which is a topic > that is very difficult to explain in 10 seconds to an audience who has > never seen anything about i/q sampling before. > > > I have been thinking on how to explain the concept of I/Q signalling in > just a few lines, e.g. in the context of -say- a workshop on GR. > > > I have this idea in my head: > > Statement: > The main difference between sampling with reals ('floats') and i/q > sampling with complex numbers, is that the latter does not only provide > the instantaneous value (voltage) of a signal at a certain point of time, > but also includes phase information (i.e. the slope of the signal at that > point). > > > To make this visual: > Take half a sine-wave and plot it out for every 45 degrees. > This gives you 5 points: 0 (0 degrees), sqrt(2)/2 (45 degrees), 1 (90 > degrees), sqrt(2)/2 (135 degrees) and 0 (180 degrees). > > Now look at the 2nd and the 4th point (45 degrees and 135 degrees), if you > sample this using only real/float values, these two points are exactly the > same (sqrt(2)/2). Just based on these values by themselves (i.e. remove all > other points from the graph), there is no way you can tell that at the > first point (45 degrees) the graph was going up, while at the 135-degrees > point the graph was going down. > > So, ... what i/q sampling does, is for every point "x", it not only > provide the value of the graph at that point of time, but also information > of the slope of the graphs at that time. > > > This also explains while i/q sampling is done by not just taking the value > of a signal at point "t", but also at 1/4 period later (which is the > information you need to determine the 'slope' of that graph at point 't') > > > So, ... is this statement correct? > > If it is more-or-less correct and it can help provide a basic mental image > of the concept of i/q sampling, I would be more then happy! :-) > > > > > 73 > kristoff - ON1ARF > > > > > -- S. Aditya Arun Kumar Security Researcher, Comms +919123517465
