Costas Loop Demodulator

День тому

An explanation about the working principles of the Costas Loop demodulator, used for carrier recovery and carrier synchronization.
First invented by John. P. Costas, the Costas Loop is a clever design that enables demodulation of double-sideband carrier-suppressed signals.
The Costas Loop is a natural demodulator for BPSK digital signals and, in this video, Gregory explains how it works and how is can be used to demodulate higher order constellations, like QPSK and 8PSK.
Support the channel, become a Patron!
/ allelectronics
A related video about Clock Recovery PLL:
• Clock Recovery and Syn...
Subscribe for new videos.

КОМЕНТАРІ: 53

@AllElectronicsChannel 2 роки тому

Subscribe and become a Patron! www.patreon.com/allelectronics

@BalticLab 2 роки тому

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 2 роки тому

Thank you, Baltic!

@maximus6884 Рік тому

yes, such a hidden gem.

@yakovdavidovich7943 2 роки тому

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 UKposts channel for me right now!

@AllElectronicsChannel 2 роки тому

Thank you and welcome!!

@camodude9224 Рік тому

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 Рік тому

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

@l_szabi 2 роки тому

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 2 роки тому

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

@denizhankaraca8862 10 місяців тому

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

@AllElectronicsChannel 10 місяців тому

Great to hear!

@moritzjakob5541 2 місяці тому

Great explanation!

@AllElectronicsChannel 2 місяці тому

Glad you think so!

@declanmoore Рік тому

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

@AllElectronicsChannel Рік тому

Welcome to the channel!

@elware176 Рік тому

perfect video, thank you for nice explanation :)

@AllElectronicsChannel Рік тому

Thank you! Welcome to the channel

@gammaleader96 2 роки тому

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 2 роки тому

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

@Kronkulus9282 9 місяців тому

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 9 місяців тому

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

@nova0302 11 місяців тому

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

@AllElectronicsChannel 11 місяців тому

I tuned it by hand for this demo!

@like_cabezon3810 2 роки тому

Very useful video no much content about that circuit.

@sambhupra 9 місяців тому

I do I get the simulation files?

@fuelcellmotorbike 2 роки тому

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 2 роки тому

No! The error gradient points to the I axis!

@fuelcellmotorbike 2 роки тому

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 2 роки тому

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 2 роки тому

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

@AllElectronicsChannel 2 роки тому

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

@SandeepKumar-jj7zi 2 роки тому

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

@AllElectronicsChannel 2 роки тому

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

@MrCuddlyable Рік тому

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

@asinegaasinega 9 місяців тому

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 9 місяців тому

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

@AllElectronicsChannel 9 місяців тому

❤❤❤ thank you guys!

@codyemerson9974 Рік тому

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 Рік тому

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

@like_cabezon3810 2 роки тому

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

@AllElectronicsChannel 2 роки тому

Today's as DSP!

@huawatuam4965 2 роки тому

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 2 роки тому

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

@huawatuam4965 2 роки тому

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

@AllElectronicsChannel 2 роки тому

@@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.

@user-nh7lr2tn8o Рік тому

please j need this matlab code

@LarsBerntzon Рік тому

What is a NCO?

@AllElectronicsChannel Рік тому

Numeric controlled oscillator

@LarsBerntzon Рік тому

Ah, of course. Thanks. Great videos btw

@asinegaasinega 9 місяців тому

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 9 місяців тому

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