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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
by yodon 1y 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.
- furgot 1y agoMost 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_components https://en.wikipedia.org/wiki/In-phase_and_quadrature_compon...
- gsf_emergency_2 1y agoQ=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-and-fourier-transform-part-1/#:~:text=What%20are,Signals%3F 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
- wucke13 1y agohttps://www.pe0sat.vgnet.nl/sdr/iq-data-explained/ 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.
- msravi 1y agoI 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 1y agoWhy would you want two carriers?
- Sesse__ 1y agoTwice 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.
- ykonstant 1y agoOnly people with a low I/Q would misunderstand this notation!
- dsp_man 1y agoThank you for the suggestion. That's the point. I/Q introduced early gets too complicated. This foundation needs to be built up.