#170

This video presents an introductory tutorial on IQ signals - their definition, and some of the ways that they are used to both create / generate modulated RF signals, and demodulate / analyze RF signals. IQ signals are most often used in the transmit and receive paths of Software Define Radios (SDR). A PDF of the drawings can be found here:
www.qsl.net/w/w2aew//youtube/B...
Here's a recent blog post (not mine) that also explains this quite clearly:
blog.aunyks.com/2020/11/under...

[@navyman4]

After 26 years of Navy Electronics, working at NASA, building spacecraft comm systems, this is the first time I completely understand I & Q signals. No one ever showed me on an Oscope. I finally get it! Thanks.

[@celticTT]

I was also in the Navy and agree with you. There are so many areas that I do wish the Navy would go into more depth.

[@AM-yj5yc]

It's fascinating how these orgs that do such high level stuff manage to get people working functionally with stuff with only a basic working knowledge of the tech and physics involved. I always like to think of it in terms of something I think I first heard in software engineering: the black box model. They show you what need to input to a system, and what outputs you get for given inputs, but don't bother to show you whats actually going on inside the box, just expect you to take for granted that it'll work assuming you do the inputs right and know what to do with what you get out. Unfortunately, for tons of technically minded people... WE WANT TO KNOW WHAT'S IN THE BLOODY BOX. I want to know every square nanometer of everythig that is in the box, how it works, why it works, and what to do if it stops working (which, all too often, it does). Nothig more infuriating than having some system cease functioning, only for some authority figure to say "oh, well its busted, we'll send for a replacement and someone else'll fix it". Even if I cannot conceivably fix it, even if I don't have the parts, or tools, I don't like not knowing why something doesn't work as expected. Curses on the black boxes, show me whats in the bloody box!

[@martinmartinmartin2996]

I am a old time EE that has worked in many different fields of aspects of electronics: precision DC measurements , photo-controls, space exploration rocket components, RF , missile circuits, fiber optics. Did I understand the fine points of each discipline? NO I didn't . Sure I studied to a degree, but producing result$ wa$ the objective. I,Q techniques but the MEANS of producing a 90 deg phase a shift : I assumed it was simple BUT DIDN'T know how it was done !..until now 50 years (about 18,250 days later) .

[@Rees3901Gmail]

Well done on this video 👍🏻

[@JRJunior8624]

Ditto Ditto Ditto Sir, me too!! we used the instruments, the monitor, the scope, IS that Good? Yep, Pass! instructors didn't know the theory, ...and I HAVE to see the picture in order to understand the little.

[@davidgrahamut]

The clearest explanation of IQ signaling on the web

[@himesjon]

I 2nd and 3rd that!

[@JRJunior8624]

I couldn't agree more David, I have been pounding my brain over this, just want to yell YEAH but what IS IT? This is the best I have seen

[@samtedesco3529]

As a retired teacher, I am qualified to give you an "A" for this presentation. Well done!

[@user-pi4fk7gm7l]

I was just started to studying RF, and i watched so many videos but couldnt uderstand the IQ stuff , thanks to you i can move further, thank you so much sir, u really explained it very clearly.thanks again.

[@kn6eze]

Wow. I just finished reading the ARRL handbook on IQ modulation and walked away scratching my head. 20 minutes after playing start on this video cleared up all of my confusion. Very clear explanation and very well demonstrated. The examples are golden!

[@stephan5618]

I‘m a beginner in „hobby RF“… and I understood IQ for the first time. Thank you for this great video!

[@ruiferreira9980]

Here is someone who really knows what he is talking about. So clear, so easy! This always seemed to me like a complicated matter. Not anymore! Thanks a million.

[@tav9755]

This is pure YT-Gold. Well prepared, nicely edited, good mix of theory and demo.

[@michaelmawhinney5218]

I had more "ah-ha!" moments during the 20 mins of this video than I have during my entire 10 years in telco! Thank you so much for your sharing of knowledge. This is a great, "back to basics" instruction for anyone working with any type of RF signal. Thanks again, you got a subscribe from me!

[@21st_charlie34]

You know, i study electronical engineering in the 7th Semester - Specialized in RF-Design. I had 6 Subjects with 4 different profs on system theory and software receiver design. Until i watched your video i did not really understood what this IQ modulation/demodulation is all about. But you just broke down 2 years of studying in just ~20 min. This video is absolute gold. Now i have an understanding of IQ modulation. Thank you sir!

[@w2aew]

Thank you! Maybe you should share my video with your professors!

[@jeppe5942]

I have never heard of a degree in electronical engineering. Maybe you mean electrical? Or electronics?

[@nicksonkosi]

@@jeppe5942 there's always a first time to hear about something

[@AppliedScience]

Really great explanation!

[@hrivera4201]

Almost as good as Applied Science explanations.

[@eloygonzalez840]

nice job, clearest and simples explanation of IQ signals in the whole internet

[@TheTrini1980]

This is the best tutorial on IQ signals I’ve ever seen. You have clearly explained this topic that has always been very hazy in my mind.

[@Afrotechmods]

Thumbed up before watching. I know this is going to be amazing.

[@Afrotechmods]

I was right.

[@user-xj8oh6fo2f]

So did I ))

[@jimmysyar889]

Hey! Another one to the list

[@whawaii]

FINALLY - THANK YOU! After years of working with Digital Video Signals for Satellites (DVB-S), I understood BPSK (flipping the carrier) modulation & vaguely understanding QPSK with the constellation diagram. Then came (DVB-S2) with 8PSK for HD & all I could manage was being able to regurgitate the BS I had been told. NOW, I finally get the nuts & bolts of how QPSK works, is assembled & deciphered, along with having a thorough understanding of QAM signals. From here I can extrapolate that for 8PSK & 16QAM. THANK YOU!

[@mariaa.2240]

I bumped on this channel as I have to take over a RF testbench for infrared detectors during my PhD and this channel is completely what I need! Thanks! 🎉

[@QuintinMassey]

I know this is an old video but thank you for covering the foundational concepts of what I/Q data represents and showing exactly where the rubber meets the road. This information makes the more "sophisticated" topics more attainable. Thank you!

[@houstonosemwengie8683]

This has been the most clear explanation of demonstration of IQ processing I have come across. Amazing content, thank you!

[@fjdarling]

This is the most clearly explained (I & Q signals) I've ever heard since college. Thank You.

[@SuperChad1313]

You just combined so many of my engineer classes I am rather stunned. I wont sleep tonight.....thanks.......

[@zeidar]

Perhaps the best explanation for basic modulation & demodulation I've seen. Respect.

[@Dutta1605]

It is the most satisfying tutorial so far in my life, after working in Radio Resource Management for one of the leading telco for quite a long time for the first time I was able to visualize the IQ concept. Great work and your efforts are visible. You are simply awesome.

[@macuser1232]

They show us the equations for modulations, but never give us this straight forward example of how to do it in practice. Very good video, thank you.

[@alinayossimouse]

I've been exploring RF for a few months now and have watched countless videos on the topic. Your explanation of quadrature signals is easily the most complete yet simple to understand. My understanding of I & Q has just made a big leap

[@naqeebt]

world needs more teachers like u ....thanks you for the video :)

[@pankajsharma-mx8hn]

amazing ....for the first time in my little life i have understood what actually i was reading all my life.... thank you very much for this beautiful demonstration

[@johnbarber1482]

Thank you! Why can't universities explain this stuff as simply and comprehensively as you did? You'd think Universities would want to give their paying students superior quality of service. I'm a Senior, and almost wish I hadn't gone to Electrical and Computer engineering school. I feel as though I wasted my time learning rando math and science stuff without seeing how to actually apply it.

[@oakspines7171]

People need the concept illustration like this to have a solid foundation before they begin learning all the tedious and boring formulas derivation like those taught in schools . Great work for spelling it out to the world.

[@richardvlog]

An American way of passing on information: simple, direct and easy to interpret. Simply the best information you can find here on KZbin.

[@blitzkneisser]

Thanks a lot - I just had the most valuable 20 Minutes of KZbin-time since many years! They way you explain the concept us IQ modulation is perfect in its combination of simplicity and detail. I recently started to work on digital designs for rf applications (mainly BT and WIFI) and this was the first time I fully understood that concept.

[@rishikeshchapekar4481]

5 min into the video and I already know I'm going to learn more here than an entire semester worth of college education. Plus looking at the comments of people with decades of experience saying this video helped them is a really re-assuring. I'm glad I found this while I'm still in college. I'm looking to build a career in this field and this will definitely be a stepping stone in the right direction. Thank you so much!

[@basarozyilmaz]

This is a perfect video which I will share with anyone who asks what IQ modulation is sir. Thank you.

[@2bitmonkey]

Thank you so much, it's like a light bulb lit up for me. Thumbs up for production value and a quality video. 73, de N6HZ

[@w2aew]

Thank you, I'm glad you enjoyed it.

[@Narigopia]

Same here, great video, thank you.

[@robbvk6es]

Thank you Alan. This is a subject on which I was completely ignorant of aside of Grey code and in under 20 minutes I now have a basic understanding and a light bulb moment into understanding of a small telemetry modem I have. The thing I like most about your channel is even within a fraction of all that is electronics related, you manage to create clear and concise educational videos every week. Such a pity the "biggest" electronics related channel has lately degenerated into a lifestyle show. In my opinion content older than say 2 years should not generate income for the "professional" content producers to prevent them from resting on their laurels. Your channel is all about discovery and questions of income never arise. Channels like yours are the reason why I now rarely watch TV.

[@w2aew]

Thank you! Very nice of you to say. I hope I can continue to put together content that people like yourself find interesting, educational and useful.

[@christianmoser2579]

Holy cow, that video just obliterated the last 1.5 years of my electronics education. Thanks a lot mate

[@jimroselli8487]

Alan. Extremely helpful video. Your description and graphics make understanding the subject much easier. Then when you put them on the scope, well that put it over the top. Seeing the signals on the scope tied all the elements together. Very much appreciate your educational videos. N2GMA

[@UTMadMan]

The best explanation I've heard so far. Great work!

[@WestCoastMole]

WELL DONE Alan ! You have once again taken a deep topic and presented it a form that is easily understandable. It conveys to the viewer a working overview of the theory that powers software defined radios. Thanks again

[@alexreeve]

i remember the pain in the a** this was to learn and understand in university.. now you come and just perfectly explain it in a 20 min video :D damn.. :D

[@bryanredd4654]

This is yet another comment about how great your video is! Thank you for taking the time to post this.

[@anantikamehra1694]

Thank you so much for this video. I can finally start to understand all the math that I have been doing blindly! You are a great teacher! Please never stop making amazing videos like this one.

[@WassimAouadi]

I wish I had you as my Electronics teacher.. great explanations and a great quality video

[@stromsgardiii5671]

I know this was posted 7 years ago, but I was really struggling to get this concept down and you helped me crack it (I think). Thanks so much!

[@eviltwiner]

Very clever tech! I love the way you explained these concepts, very clear and easy to understand with practical examples.

[@subinsubhagan7010]

Wonderful video..never seen anyone explain IQ simpler than this…thank you professor !

[@romualdobrogliatto7687]

One of the best explanation ever, even for me that I am not native speakers, I am from Brazil. You have the ability to explain things in a simple way and make everything clear. Congratulations !

[@jimh2698]

Excellent! You have an unusually good combination of skills; that being the knowledge of the subject and the ability to present it clearly.

[@fjs1111]

Excellent video, I stumbled across this accidentally but I've never heard anyone breakdown the I/Q mixing so well. Outstanding!

[@msmith0043]

Excellent job on this. I've read several papers on this and finally absorbed it after about the 3rd one. Your practical approach using a scope to show the modulated signals in the time domain was a great way to tie it all together. Thanks for taking the time to put this together. No doubt that many will benefit from it. Thanks!

[@windytan]

Excellent demystification of the concept.

[@HansVanIngelgom]

W2AEW is always awesome. BTW, I was just watching this: Defcon 21 - All Your RFz Are Belong to Me - Hacking the Wireless World with Software Defined Radio . A long presentation, but some really good info and things I want to try out myself (measuring baudrate using gnuradio etc). If you haven't seen it already, you should! --... ...--

[@JoeDesbonnet]

There was an excellent free Coursera on-line course given by the DSP group at EPFL (Switzerland). I think they run it every year. Well worth doing to get a solid mathematical foundation on the topic. www.coursera.org/course/dsp

[@windytan]

Hans Van Ingelgom Wow, he packed a lot of stuff in one talk.

[@JoonasPerttula]

I think that I didn´t learn this much in my class in whole course than this video... Thanks

[@fredlodden1538]

Excellent explanation. Awesome. Well paced, clear, develops concepts and progresses logically, great scope shots, great diagrams. I learnt quite a bit. Thanks.

[@himesjon]

I took the RF series at university and I learned so much more practical information from you in such a short period. It definitely helps at work and my ham knowledge.

[@w2aew]

Thank you for your nice comments - glad to know that my videos have helped.

[@samykamkar]

Excellent explanation and demos!

[@fil290]

Samy Kamkar lol, just watched one of your old conference in which you talk about signal modulations. Wanted to understand more about it and here I find you xD

[@Aemilindore]

So all the youtube stars watch Alan's IQ videos huh? :-P

[@roladun]

Excellent explanation, I guess there is no point of college any longer for a self learner, just good text-books with KZbin tutors like w2aew are more than enough to gain that precious knowledge.

[@ashokdas2070]

totally agree

[@vishweshkumaraithal2880]

Clear, concise and to the point explanation. Simply superb!!!

[@LancasterWannaBe]

Fantastic video!!!! I really appreciate the work you put into building the physical mixers and demonstrating the modulation with your equipment there. I'm striving to understand how to modulate / demodulate signals, and this video just connected a LOT of dots. Thank you!

[@uNabL3]

One of the best video tutorials on I/Q I've seen so far. Thank you :)

[@w2aew]

Thank you for the nice comment!

[@billmoran3812]

Wow, excellent tutorial. I never really understood phase shift keying, but you made it perfectly clear. I feel like I've progressed from the 20th century to the21st!

[@w2aew]

I'm glad this video helped you!

[@freedomchinaify]

same here

[@TheZaxanoid]

Very good! A perfect mixture of theory and practical demonstration

[@SoulCharter]

Such a great video. Thank you very much. Your patience with explaining the topics is greatly appreciated.

[@EscapedConvict2007]

Best I/Q mod/demod explanation I've came across in university and workplaces, so glad I stumbled upon this video in desperation of trying to understand I/Q. sub'ed.

[@jannikheidemann3805]

Very well explained! I will share this to friends who are also interested.

[@ilyapanfilov8421]

Excellent visualization of this somewhat complex concept. Thank you for the effort.

[@LMerryman]

I always get an excellent education from your videos, hope one day to have a 1/4 of your knowledge.Thank you Alan for all that you give us.

[@WilliamJCroft]

Alan, this is brilliant. A Ham University Professor!

[@mustaphaalkhafaaf5512]

very nice && very informative .. Excellent effort ... Thank you

[@evensondlovu4982]

Brilliant people know how to simplify complex concepts and you just did that, thank you.

[@w2aew]

[@loiphin]

Thank you so much for the clear and concise video. I have just started my SDR journey and I now understand I/Q much better :)

[@emremetin684]

Excellent video. Thank you.

[@gerrysweeney]

Hi ***** another awesome demystification for me, very easy to follow your explanation, definitely something interesting to play with. Thank you for posting. Gerry

[@internetuser3748]

This is one of the best videos on KZbin.

[@gabrielguerreiro3123]

Thank you again. I was looking for an IQ explanation and when I found a video made by you, all my fears were vanished. I knew by the end of this video I would understand IQ signals, and that happened. All the best for you!

[@bryanjohnston9879]

As a CATV engineer I have to say this is one of the best short training videos that I've ever seen accurately describe QPSK/QAM. Thanks for putting this together! Do you have anything you can share concerning OFDM?

[@yz250ftony]

Also working in the CATV/QAM industry, I agree! R & S has some good videos too more recently.

[@khaderpr]

OMG!! you are awesome!!!

[@josegermanparra6064]

My first SDR radio arrived and want to know about this I&Q mod and demod basics to better understand the options in the software. Many thanks again!

[@Compwib]

Best explanation i have seen so far covering theory and practical through Oscilliscope

[@Mr.Laidukas]

w2aew do you take place in university? Your videos are very fluent and easy to understand, academical. You explain things in very clear and understandable way. Thumbs up!!

[@w2aew]

No, I am not a professor. Just a Field Applications Engineer, working for Tektronix.

[@superdau]

From experience I can tell you, even on reputable universities you'd be hard pressed to find a professor that can explain his stuff that well.

[@jebsaekam]

***** I would like to hear you on The Amp hour. I would be interesting.

[@w2aew]

***** I *was* already on The Amp Hour, about 2 years ago. Here's the link: www.theamphour.com/theamphour-117-undulating-utensil-utility/

[@tomfy44]

Nice video. Although I am familiar with the subject, it is a pleasure to watch it. Thanks!

[@pedrogonzalezgil]

This channel should have zillions of subscribers. Thanks for keeping at it. 73s EA5HZO

[@omskariyazmaraikayer913]

excellent practical info. never seen something like this. clear diction , clear video , subject content has been delivered linearly . Great Job sir. Now I have to watch all your videos

[@JamesCutlervk2tim]

One of the better tutorials that I have seen. Very well explained and presented.

[@JanMoren]

I've become curious about SDR lately; you haven't thought about presenting a small SDR DIY project or something like that? One question: for demodulating IQ, how do you know what phase is, well, zero? The phase-varying signal doesn't tell you by itself. For digital signals you could just let the transitions, rather than the levels, represent bits, but for analog signals wouldn't you need to know the "in-phase" time?

[@w2aew]

You generally don't need to know where "zero" is. You're really only interested in the changes. So your arbitrarily normalize at any point, and track variations from there. Amplitude as SQRT of sum of I squared and Q squared, phase as arctan(Q/I), and frequency as d(phase)/dt.

[@yevhenii987]

***** Very usful answer.

[@JohnNitis]

Well done, "professor!" Was that an eevblog bumper sticker I spied? Wow, and afrotech is here too. We need a convention with Alan, Dave, Afro, and Mike. Now how cool would that be?

[@w2aew]

That was one of the EEVBlog PCB rulers on my bench, yes. It would be a lot of fun to get together with those wizards!

[@CH_Pechiar]

Add Gregory Charvat and Michael Ossmann to the reunion, too. The last episode of The Amp Hour (#214) was a mix of a lecture and brainstorm session; really good. Alan, excellent video! As usual. Regards, CH!

[@w2aew]

I really enjoyed the last Amp Hour show too. We'd also have to add Chris, and don't forget Shahriar from The Signal Path Blog.

[@CH_Pechiar]

***** Sure! and Jeri Ellsworth too! Can you image all of you together? haha! BTW, I am waiting for my Softrock Ensemble II receiver kit to arrive, and, ahh, I have just watched your video on the HotWheels radar analysis and my head is about to explode. Too muy IQ today!

[@w2aew]

Charlie Pechiar Agreed! I met Jeri once, by chance, at an airport. We were on the same flight. This was long before Technical Illusions and even before her time at Valve.

[@07kandarp]

Thanks Alan, very nice video again. The words QUADRATURE AMPLITUDE MODULATION just lit up in front of my eyes. This is such a clean explanation.

[@ledgendairy3056]

Your videos on IQ are great, I learned a few tricks and a new way of thinking about a few things that really cleared up a mess in my brain......I really learned more in a few videos than a year in school. Or at least you cleared up what i had had been missing. Thank you. All your videos are amazing. You make KZbin a goldmine of valuable information.

[@darkobul1]

Why no one shows how to demodulate FM signals. I watched 10 videos and no one shows it, they just say its "easy". Well if its easy then they should show it.

[@pepe6666]

Darko Bulatovic exactly. im in the same boat. it isnt clearly explained at all. it almost seems like 98% of the video is about how to modulate them, but only a brief description was given with demodulating them.

[@w2aew]

pepe6666 Given that the instantaneous phase is the arctan(Q/I), and that frequency deviation (dF) is simply the "rate of change of phase", then FM demodulation from IQ is traditionally done by taking the time-domain derivative of the phase. f(t) = d(arctan(Q/I))/dt. More details can be found here: www.embedded.com/design/configurable-systems/4212086/DSP-Tricks--Frequency-demodulation-algorithms-

[@darkobul1]

***** I could have swear that you had another video where you explained it. not 100% sure. I know I found it later somewhere.

[@RayMillTN1]

+w2aew Darko Bulatovic Here is a circuit/blog I found that demodulates BPSK - I hope to give it a try. www.analogzoo.com/2014/12/amplitude-demodulating-bpsk31/ is this a proper method? (edit: trying to ref w2aew)

[@w2aew]

Raymond Tant There are many ways to do this, and this is certain one valid approach - fairly simple because it only relies on simple amplitude detection. This works OK on this waveform because the phase shift is well filtered, providing a well defined and easily detected dip in the amplitude as the phase is shifted. If the baseband signal was not low pass filtered so well, the amplitude dip would be a lot narrower and more difficult to detect this way.

[@sandman0829]

Thank you so much for spending the time to provide this explanation to people. Very much appreciated! Nicely done as well.

[@whoknew3775]

Where was this man my junior year....fabulous vid!

[@imtiazhussain2610]

IQ Signals and IQ modulation explained in best possible way. Excellent video.

[@abhimact79]

This is the best tutorial on basic concept of Phase modulation and explanation about IQ samples. I would love to see similar content describing FFT, IFFT, IDFT concepts as well. Thanks for sharing knowledge.

[@pacman326]

Thanks so much for making these. I have been a little lost in my RF class and this is helping me catch up.

[@ShizzleMyChizzle]

Do you have any idea how well you are explaining this!? I was banging my head over IQ signals for days and you explain it in 20 minutes!!! GET OUT OF HERE! xD

[@greg4529]

Dude, you deserve a Nobel Prize in Teaching

[@viswatess]

Excellent Theoretical and practical explanation. This is one of the best technical video i ever watched.

[@THeMin1000]

THANK YOU!!! Really clear and finally understood wtf we were studying in uni during my bachelor's in RF. It's only now that it clicked that just like AM/FM/ASK and all the other modulation techniques what is the significant part of the carrier that we were changing.

[@earthwormjim]

Wow, I just stumbled on the best KZbin video I have ever seen for explaining a subject. I was looking for an explanation on QAM after watching a video about NTSC color data transmission, and how it is backwards compatible with black white televisions. The color data is hidden in the black and white compatible luminance stream, and extracted with QAM. Your explanation made it completely clear on a higher level, now it makes sense to me. I recalled doing the math in my signal theory class in college, but it never really made sense to me. Further, the basis of software defined radios makes so much more sense too. Thank you very much for this video.

[@musicforlife9247]

Thanks a lot for explaining the I-Q mod in this practical approach, I really appreciate your work.

[@brendan8915]

Such an incredible well put together lesson. I'm just getting into EE and RF and these are the things I wish I asked my grandfather to teach me before he became unwell. He had a great mind for RF. Thank you sir!

[@dandearman2871]

Great Job. It's nice to be able to see your examples on the scope.

[@brucekempf4648]

This was the most instructional understandable tutorial I have seen. Very nice to visually see how this works. So very cool! Thanks you!

[@user-gy3kk1pt2e]

Thank you very much. Your tutorial is easy to understand and very useful. It was wonderful to see actual representation of signals.