The liberal use of AI generated images really cheapens the entire article. Please don't do it. At that point I suspect most of the text is also AI generated.
yodon · 5h ago
Pro tip: If you're writing an article on the significance of something called I/Q, it's cool to somewhere in the first couple pages say something about what I/Q is.
This is an excellent introduction to the concept and also to the why complex numbers are used to represent signal samples.
msravi · 3h ago
I prefer a more "physical" explanation - you have two carriers: sin(wt) and cos(wt), and you're modulating bits I and Q onto the two carriers and adding them up before transmitting. Now, mathematically, that's the same as representing the two bits as I+jQ and multiplying it with cos(wt)+jsin(wt). Demodulation is simply multiplying that output with the complex conjugate cos(wt)-jsin(wt), which in physical terms translates to mixing with a local oscillator output and low pass filtering.
exe34 · 1h ago
Why would you want two carriers?
Sesse__ · 1h ago
Twice as much information.
My go-to for I/Q is: Having two allows you to represent negative frequencies. With a normal, real signal, this is of course impossible (negative frequencies will automatically mirror the positive ones), but if you have a signal centered around e.g. 1 MHz, there's room for above-1MHz and below-1MHz to be meaningfully different. And _that_ allows you to get a complex signal (I/Q), once you pull the center down to 0 Hz for convenience of calculation.
gsf_emergency_2 · 4h ago
Q=Quadrature, I=In-phase
(As you point out not in the first couple pages, but waaay down)
Not trying to be charitable like furgot ... The wikipedia page is the first time I've seen authors go pro on the topic
ykonstant · 1h ago
Only people with a low I/Q would misunderstand this notation!
furgot · 4h ago
Most technical writing is going to assume some familiarity with the discipline. If a reader encounters unfamiliar vocabulary in a technical article, they'd be well advised to look it up.
Yikes - why even mention the E and B fields? They aren't relevant to the rest of the article.
A few hours playing with Sine and Cosine generators in GNU radio can take you from book knowledge of I/Q complex signals into fully grokking it. You don't even need a radio, just your existing audio I/O.
MrBuddyCasino · 4h ago
This reads like someone proficient in signal processing is explaining the core concepts to another person who is already proficient in signal processing.
No comments yet
esafak · 7h ago
Yet another thing from school I've never used in the software world.
By the way, QAM is (still) used in 4G and 5G.
cycomanic · 1h ago
Some variation of QAM will always be used in communication. As soon as you deal in with EM-waves, be it physics, engineering or even biomedical stuff you will have to deal with complex numbers, which by extension is dealing with I/Q signals. You probably don't need this for programming a server or a website, but it's indispensable for signal processing.
pythonguython · 6h ago
Come be a DSP engineer. I take FFTs of IQ data almost every single day
userbinator · 4h ago
Work on low-level software for communications, especially RF, and you will see plenty of this stuff.
cycomanic · 1h ago
Not just RF, also optical communications. Really, the only domain left where PAM transmission is used is baseband communication for electronics, and datacom for optics.
This is an excellent introduction to the concept and also to the why complex numbers are used to represent signal samples.
My go-to for I/Q is: Having two allows you to represent negative frequencies. With a normal, real signal, this is of course impossible (negative frequencies will automatically mirror the positive ones), but if you have a signal centered around e.g. 1 MHz, there's room for above-1MHz and below-1MHz to be meaningfully different. And _that_ allows you to get a complex signal (I/Q), once you pull the center down to 0 Hz for convenience of calculation.
(As you point out not in the first couple pages, but waaay down)
he "explains" those
https://wirelesspi.com/two-birds-with-one-tone-i-q-signals-a...
Not trying to be charitable like furgot ... The wikipedia page is the first time I've seen authors go pro on the topic
https://en.wikipedia.org/wiki/In-phase_and_quadrature_compon...
A few hours playing with Sine and Cosine generators in GNU radio can take you from book knowledge of I/Q complex signals into fully grokking it. You don't even need a radio, just your existing audio I/O.
No comments yet
By the way, QAM is (still) used in 4G and 5G.