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.

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gsf_emergency_2 4 days ago | parent | next [-]

Q=Quadrature, I=In-phase

(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

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wucke13 4 days ago | parent | prev | next [-]

https://www.pe0sat.vgnet.nl/sdr/iq-data-explained/

This is an excellent introduction to the concept and also to the why complex numbers are used to represent signal samples.

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msravi 4 days ago | parent [-]

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.

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exe34 4 days ago | parent [-]

Why would you want two carriers?

	▲	Sesse__ 4 days ago \| parent [-]
		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.

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dsp_man 4 days ago | parent | prev | next [-]

Thank you for the suggestion. That's the point. I/Q introduced early gets too complicated. This foundation needs to be built up.

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ykonstant 4 days ago | parent | prev | next [-]

Only people with a low I/Q would misunderstand this notation!

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furgot 4 days ago | parent | prev [-]

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.

https://en.wikipedia.org/wiki/In-phase_and_quadrature_compon...