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The Real Reason Behind Using I/Q Signals
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- Опубліковано 7 сер 2024
- #wireless #lockdownmath
Mystery behind I/Q signals is resolved in an easily understandable way.
Read the associated article by clicking below.
wirelesspi.com/i-q-signals-10...
Check my website for all the articles on DSP and wireless communications. wirelesspi.com
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Yes, this has been a mystery to me but your explanation is very helpful. Thanks!
Glad that it helped.
First time I really understood it! Great video.
This is a wonderful explanation. Excellent job sir
Beautiful explanation....pl make another video explaining through block diagram from IQ signal upto signal detection, final output
Fabulous teaching. Thank you :)KD
Nice explanation! Thanks!
An exceptional explanation!
Genius guy! well done!
I learned something new. Thx
wonderful!!!!
ty sir, much appreciated!
thank you very much the video that i am looking for
Nice explanation
very clear thank you
Brilliant at 6:55
Amazing video..!
Glad that you liked it
Awesome 👏
Thanks
Classic explanation. Still some doubts…
Gone through your lengthy post on iq modulation. Before introduction of iq modulation 8 psi modd demoed was explained and drawback of psi demodulation was explained in 8 psk.
If this is really the issue with psk how did it survived? I mean there is no one to one mapping of the constellation points at the receiver ….
It was not a drawback of PSK. I wanted to lay ground for why we need phases on a continuum. In regards to how to demodulate PSK and other linear digital modulation schemes, you can see my book on wireless communications wirelesspi.com/book.
1:57 What do you mean, "frequency is a function of phase " ?
Frequency is the rate of change of phase!
The #1 reason to use I/Q signals is that they let you to distinguish positive from negative frequencies. *Everything* else flows from that! Signals containing only a real component consist of equal amounts of positive and negative frequencies, so when you mix them you get both sum and difference frequencies. But mixing a complex signal with a complex oscillator simply adds the two frequencies; there is no difference frequency component! So despite the unfortunate term "complex", this actually vastly simplifies the processing and filtering of signals. Especially at low frequencies where it's easiest to process them digitally at low sample rates. Using real signals at low frequencies commonly causes "folding" around DC (O Hz), which is a real pain.
What you're saying is true from a communications perspective. I have mentioned this difference between positive and negative components in the related article wirelesspi.com/i-q-signals-101-neither-complex-nor-complicated/.
Having said that, DSP is a toolbox and wireless communications is one of its applications. I/Q signals are helpful in many other areas too beyond downconversion of modulated signals.
@@wirelesspi9183 I am usually explaining this to a ham radio audience. So I start by saying that we hams usually think of signals as oscillations, eg, wiggling electrons in antennas. And they are. But it's more complete to think of them as *rotations* with sinusoidal oscillations just being what you see when you look at a rotation edge-on. You can tell how fast an oscillation is going but to see *which way* it's going you need to see the rotation. And to do that, you can look at it from two edges: the front and the side, 90 degrees away. I've even held up and spun a bicycle wheel to show the point. Do you see where I'm going? I usually see a lot of light bulbs come on in my audience at this point.
@@philkarn1761 Yes I understand what you're saying. I use a slinky (helical spring) to demonstrate the complex sinusoids. In my opinion, it's better to see the amplitude as a general case (instead of the direction of rotation). For example, cosine in both cases has a positive sign but your clockwise rotation has a negative sine wave while an anticlockwise rotation has a positive sine wave. Yes, we do call this a positive or negative rotation but if we see this a multiplication of a zero phase sine wave with -1, then from here, you can generalize the idea of I/Q signals for any phase.
@@wirelesspi9183 One of the neat things about physics and math is that there are often several equally valid ways to achieve the same result!
The tutorial is simple to understand nice efforts. I have one basic doubt in IQ data . How the dynamic frequency signals represented with IQ data and IQ is basically zero IF signal if I am not wrong. If a certain signal is having negative doppler frequency then how the IQ data still hold the negative frequency information. Thank you
In this case, the original complex signal is multiplied with a complex sinusoid rotating in a clockwise direction (due to negative Doppler frequency). To estimate that frequency, you will have to remove the original signal through a complex conjugate product.
@@wirelesspi9183 Thank you very much. Can you please suggest any good article regarding this topic.
@@sathishnayak52 You can find lots of scattered information here and there. For information in one place, see Mengali's book on synchronization if you are really good at maths. For an easier explanation, see Chapter 6 of my Wireless Comms book.
@@wirelesspi9183 Thank you very much
Where you repeated your sentence for I/Q explanation: By zero-phase sinusoids, do you mean "non-phase shifted sinuside"??
That's correct.
“Amplitude 1 by 5” and so on. What does that mean ??? These amplitudes are all less than 1.0 …
Amplitude 1 for 1 kHz sinusoid, 1/3 for 3 kHz sinusoid, 1/5 for 5 kHz sinusoid and so on. That's how a square wave is formed and these are called Fourier Series coefficients. Hope that helps.