Re: explaining i/q

ps://wirelesspi.com/i-q-signals-101-neither-complex-nor-complicated > > Cheers, > Qasim > > From: Kristoff > To: discuss-gnuradio@gnu.org > Subject: Re: explaining i/q > > Hi all, > > > I was watching the webinar of Heather on GNU Radio today, when it came to >

Re: explaining i/q

length, my main purpose was to produce some beautiful figures that can help one grasp why both I and Q samples are required. https://wirelesspi.com/i-q-signals-101-neither-complex-nor-complicated Cheers, Qasim From: Kristoff To: discuss-gnuradio@gnu.org Subject: Re: explaining i/q Hi all, I wa

Re: explaining i/q

On Wed, Nov 04, 2020 at 07:13:09PM -0600, David Hagood wrote: > > On 11/4/20 6:26 PM, david vanhorn wrote: > > "Twice the bandwidth" but that doesn't account for the 0 Hz "hole" where > > the incoming signal is exactly at the sampling rate. > > Or am I missing something? With complex samples at r

Re: explaining i/q

On 11/4/20 6:26 PM, david vanhorn wrote: "Twice the bandwidth" but that doesn't account for the 0 Hz "hole" where the incoming signal is exactly at the sampling rate. Or am I missing something? What "hole" are you referring to? There is the "zero bang", which occurs because most systems aren'

Re: explaining i/q

"Twice the bandwidth" but that doesn't account for the 0 Hz "hole" where the incoming signal is exactly at the sampling rate. Or am I missing something? On Wed, Nov 4, 2020 at 3:28 PM Fons Adriaensen wrote: > On Wed, Nov 04, 2020 at 05:14:00PM +0100, Kristoff wrote: > > > For us, "even if we wou

Re: explaining i/q

On Wed, Nov 04, 2020 at 05:14:00PM +0100, Kristoff wrote: > For us, "even if we would be able to look at a rotating object up-front and > from a 90 degrees angle at the same time, if the object would be frozen in > time we would still not be able to determine if the doll rotates left of > right".

Re: explaining i/q

You can lead a horse to water... Then there's hams like this: https://g3rbj.co.uk/ On Wed, Nov 4, 2020 at 12:04 PM Kristoff wrote: > Don, > > > A small (slightly) remark about this video, and about hams. > > When I gave my first video-presentation for the Belgian SDR Meetup (in > September), I

Re: explaining i/q

Don, A small (slightly) remark about this video, and about hams. When I gave my first video-presentation for the Belgian SDR Meetup (in September), I have a presentation on GR (an example of an RTTY decoder). But, to keep the presentation on topic, I first posted a "list of interesting things

Re: explaining i/q

Now, unless I am completely wrong, the model you use captures both the I and the Q samples at the same time. This means that there is no element of 'time'. In electronics, this works fine, due to the nature of mixing and a difference of phase of the two Local-Oscillators. But that's not how pe

Re: explaining i/q

David, all, Well, I had also been thinking about this. I do like the idea of the spinning doll. It provides a model for positive and negative frequencies: if it spins one way, the frequency is positive, if it spins in the other direction, it is a negative frequency. And, it does also give a

Re: explaining i/q

Here’s a YouTube video that’s got a bit of pencil math (so it doesn’t drone on) and oscilloscopes (for the ham guys), so it’s got a bit for everyone . https://m.youtube.com/watch?list=PLvOgjCaG0WzDAF1Um894vv95mrcyortOB&v=h_7d-m1ehoY > On Nov 4, 2020, at 7:52 AM, Kristoff wrote: > > Jef, > >

Re: explaining i/q

Oops small correction, prior to decimate by 2 in the conversion, you have to low pass filter by fs/4. (Or use a decimating filter) Whoops. - Anon > On Nov 4, 2020, at 08:47, Anon Lister wrote: > > Now decimate by two since you have two empty halves of visible bandwidth at > the edges.

Re: explaining i/q

> On Nov 4, 2020, at 07:13, Fons Adriaensen wrote: > > Whenever I have to explain some DSP principles, I start with > the complex valued version, and then showing the real-valued > one as a special case. This is absolutely correct here. If they are learning gnuradio, they obviously want to d

Re: explaining i/q

Hi I do agree with Jeff Long. You will have to distinguish Sampling and IQ: Complex signal are not related to sampling, even if sampled signals in GR are generally complex Complex signal come from the baseband equivalent

Re: explaining i/q

Jef, Concerning the term "slope". Well, I also have my doubts about it. I think that for a lot of people, this would create the assumption that the signal then goes from the 'i' value to the 'q' value in a straight line, which is -as we know- not the case. Sometimes it helps to -at first- g

Re: explaining i/q

On Wed, Nov 04, 2020 at 12:38:27AM +0100, Kristoff wrote: > So, what is iq-sampling? > IQ-sampling is like sampling a normal ("real") signal -i.e. what most people > are familiar with-, ... except that you sample the data twice for each > period: once at timer "t" and a second time 1/4 sampling p

Re: explaining i/q

Like I said previously: Think of the spinning dancer illusion. It works because you only see from one vantage point. If you saw a real doll spinning, and assuming you have two eyes and normal binocular vision, you will have parallax, and that will allow you to determine in reality which way th

Re: explaining i/q

It's more important to give people some mental picture than to make sure it's completely correct. But, I would not use the "slope" terminology. The important things are, as you've said, (1) with the complex type, you can have a signal at baseband that is not symmetric, and (2) the price for this is

Re: explaining i/q

David, On 4/11/2020 01:18, David Hagood wrote: 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

Re: explaining i/q

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

Re: explaining i/q

Jef, Fabian, Aditya, Anon, David, I'll just reply to this one message so not to spam the list to much but please consider this a "thank you" to all for replying. As said, this is for a limited and very specific goal: I will probably be giving a workshop on GRC in a couple of weeks and I want

Re: explaining i/q

This is a great thing to try to figure out. If we can come up with an answer that gives someone a feel for why I/Q is used in SDR in 10 minutes, and does not include phasors, exponentials to a complex power, a derivation of any equation, the concept of orthogonality, etc. ... it will win a Nobel pr

Re: explaining i/q

Hi Kristoff, As some people already pointed out here, it is always good to give multiple views for the concept of complex numbers, as different minds work differently and some explanation may push the right buttons for someone, but not for someone else. Especially for such a complex (pun intended)

Re: explaining i/q

Hello, You can have a look hereThe Concept of Frequency | Wireless Pi | | | The Concept of Frequency | Wireless Pi | Qasim Chaudhari CEO of Wireless Pi is great ! You will find plenty of information on his website. Gil. Le mardi 3 novembre 2020 à 00:06:02 UTC+1, Kristoff a écrit :

Re: explaining i/q

So did that answer your question? [image: Mailtrack] Sender notified by Mailtrack 11/03/20, 08:23:36 AM O

Re: explaining i/q

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 electri

Re: explaining i/q

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