Costas Loop Demodulator

[@AllElectronicsChannel]

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[@BalticLab]

Gregory, not only are your videos awesome, I absolutely love the positive and enthusiastic energy you bring into these topics. It's obvious you enjoy what you're doing. Great job!

[@AllElectronicsChannel]

Thank you, Baltic!

[@maximus6884]

yes, such a hidden gem.

[@yakovdavidovich7943]

Wow, what a beautiful video; and what an illuminating approach! I've been trying to slog my way through DSP implementation of a bunch of digital signal demodulators. It frustrates me how infrequently these things are treated on the level of practical intuition, rather than the math. Thanks... I just joined your patreon -- yours is the single most educational KZbin channel for me right now!

[@AllElectronicsChannel]

Thank you and welcome!!

[@camodudeA51]

Thank you so much for your explanation of the Costas loop...it has now been Demystified by you (you are the best teacher ever). Hard to believe how QAM-1024 can even work, I now wonder how that is aligned.

[@AllElectronicsChannel]

Thank you! For higher constellation order, other methods are used, like Direct decision!

[@denizhankaraca8862]

Thanks for this intuitive explanation, it's exactly what I needed.

[@AllElectronicsChannel]

Great to hear!

[@l_szabi]

Very informative video, with a lot of intuition! I think for the BPSK, a better error function would be sgn(I)*Q, instead of I*Q. This would eliminate the white zone around the Q axis (when I=0), and would give a sharper edge, like on the other diagrams. This would help the PLL to lock on faster.

[@AllElectronicsChannel]

Yep! You are right. Sign(i) *Q is commonly used, and uses less logic on FPGA/ASICs

[@declanmoore]

Wow, thanks so much for making this make sense for a complete newbie 😅 great video .

[@AllElectronicsChannel]

Welcome to the channel!

[@moritzjakob5541]

Great explanation!

[@AllElectronicsChannel]

Glad you think so!

[@elware176]

perfect video, thank you for nice explanation :)

[@AllElectronicsChannel]

Thank you! Welcome to the channel

[@MrCuddlyable]

How to design the filters for a) demodulating weak noisy signals and/or b) a wide frequency pull-in range ?

[@asinegaasinega]

You really expect the guy even understands on how to design the most important component of the whole architecture? I suggest you start looking at books (that's what I have resorted to at least)

[@MrCuddlyable]

@@asinegaasinega Thank you for your suggestion which is a good one for anybody.

[@AllElectronicsChannel]

❤❤❤ thank you guys!

[@johnaweiss]

10:08 Awesome! Is that your invention? Or is standard method? 13:22 How many carrier cycles (bottom trace) per symbol (top trace)?

[@AllElectronicsChannel]

Not my invention.. Not sure about the "standard method", just something I implemented and worked! I don't remember the numbers.

[@gammaleader96]

It is always nice to have another way of looking at something. Especially since the mathematical way is often the most precise but also the least intuitive one to take. I like your way of dividing a closed loop system into subparts and look at their inputs and outputs first. I find that it often helps a lot to break the feedback and take a look at it in a linear way instead of a closed loop with feedback. Are you actually building a new receiver (maybe V2 of your BPSK receiver) or is it just a coincidence, that you cover a lot of receiver topics lately?

[@AllElectronicsChannel]

Thanks man!! I'm not, I'm chilling a bit from the 10g source hahahaha

[@nova0302]

Thanks bro! Can you elaborate on how you choose Kp, Pi?

[@AllElectronicsChannel]

I tuned it by hand for this demo!

[@Kronkulus9282]

If the error goes to zero and the loop lands on the I=1,Q=0 point in the constellation (in the BPSK scenario for example), I can see that working. However what if it lands on the I=-1, Q=0 point in the constellation? Wont that mean your demodulated data is inverted because your loop locked on to the inverted component and not the in phase component?

[@AllElectronicsChannel]

The data will be inverted. This is why sync codes are needed or differential encoding. It is impossible to prevent this phase inversion ambiguity in BPSK

[@codyemerson9974]

What is the benefit of doing the quadrature demodulator at IF instead of digital baseband? I don't think you need the low pass filter in a digital system

[@AllElectronicsChannel]

There are tradeoffs.. not benefits.. zero-if dowconversion imply balanced IQ paths, AGC before ADs.. so there is no best topology

[@fuelcellmotorbike]

Thanks for another very interesting video! As I understand it your BPSK error function also goes to zero when I is 0 and Q is not zero, so you could get a lock 90 degrees out of phase, right? How would you handle that?

[@AllElectronicsChannel]

No! The error gradient points to the I axis!

[@fuelcellmotorbike]

But if the error function is purely I * Q, to minimize it you could also have Q go to zero no? The gradient seems to reflect this, as it is also white along the Q axis. Or am I missing something. :)

[@AllElectronicsChannel]

It is white but it is an unstable region, any displacement/noise will generate errors that points to I. The colors (error direction) would need to be reversed to Q be stable.

[@fuelcellmotorbike]

@@AllElectronicsChannel Ah I see, so the error signal has a magnitude and a direction?

[@AllElectronicsChannel]

Yes, the sign of the error. Negative or positive, these are the colors on the diagram!

[@like_cabezon3810]

Very useful video no much content about that circuit.

[@SandeepKumar-jj7zi]

Nice, is it possible to recover carrier from analog PM modulated suppressed carrier signals ?

[@AllElectronicsChannel]

I'm not sure! Maybe with a loop constant slower than the modulation?

[@huawatuam4965]

The color-transition in your first constellation diagram (BPSK) ist showing a white region along the Q-axis which ist wrong. Should be showing fully saturated color.

[@AllElectronicsChannel]

It's not wrong. it is the error function for I * Q

[@huawatuam4965]

@@AllElectronicsChannel but in that region the error is a maximum instead of a minimum as indicated wrongly by the desaturated white coloring

[@AllElectronicsChannel]

@@huawatuam4965 The error is not maximum there. The color is generated by I * Q. On the Q axis the I is zero. 0 * Q = 0.

[@sambhupra]

I do I get the simulation files?

[@CheickSylla-i9p]

please j need this matlab code

[@like_cabezon3810]

How is this usually implemented in a demodulator as an analog circuit or with dsp?

[@AllElectronicsChannel]

Today's as DSP!

[@LarsBerntzon]

What is a NCO?

[@AllElectronicsChannel]

Numeric controlled oscillator

[@LarsBerntzon]

Ah, of course. Thanks. Great videos btw

[@asinegaasinega]

you spent all that time jabbering about nonsense when the most important and the most significant part of the costas loop you barely touched on how to design it: the loop filter or the loop controller. Next time, spend more time on the most important aspects of a subject rather than trying to impress people

[@AllElectronicsChannel]

Thank you for loving the content and loving the channel! ❤❤❤