What Does "Linear Phase" Mean?

[@ChrisWhoLikesGrapes]

I’m blown away by the quality of this video. Thank you for your work, you’ve helped me understand a topic i’ve had on my mind for months!

[@iain_explains]

Glad it was helpful! Have you seen that there are lots more videos on the channel too? Check out this web link for a full categorised listing: iaincollings.com

[@shithsu]

Appreciations from Taiwan😊 the most understandable video explaining linear phase

[@iain_explains]

Glad it was helpful!

[@payman_azari]

These videos are heaven-sent resources for engineers. Thanks, Professor Iain!

[@iain_explains]

Glad you like them!

[@malashis]

The way you explain things is truly amazing! I wish I could watch all your videos !!! Thanks for sharing.

[@iain_explains]

Glad you like the video! Hopefully you'll get time to watch some of my other videos too. There's a categorised list at this website: iaincollings.com

[@dmitrikazantsev3692]

This was good, something was new, something was not, but never seen on one page before for sure. Thanks!

[@iain_explains]

Glad you liked it!

[@aryamallick5426]

great concept sir

[@iain_explains]

I'm glad you liked it.

[@jfyt2114]

IIR filters and optical fibres have non linear phase and non linear phase occurs when two signals of different frequencies and diffrent delays are there.

[@iain_explains]

Yes, that's right.

[@sanjayd411]

Excellent explanation 👍👍

[@iain_explains]

Thanks. Glad you liked it.

[@gavishkasenanayake8943]

Wow! Thank you. Straight to the point and very clear explanation.

[@iain_explains]

I'm glad you liked it.

[@edebevictor9221]

Thank you, sir. I understood it at 7:20 .

[@iain_explains]

Great. I'm glad the video was helpful.

[@jhtongamer3151]

FL1: (Fixed minimum phase fast roll-off) FL2: (Linear slow roll-off) FL3: (Apodizing Apodization Filter) FL4: (Minimum phase fast roll-off) FL5: (Minimum phase slow roll-off) FL6: (Linear fast roll-off) FL7: (Brickwall Mixing Filter what would be the best for gaming to hear foot steps ?

[@xxgoku7774]

Hello, ive got a question, and I am sure that you are the best one to ask suppose ive got this transfer function F(s) = 1/(s+1) so the phase function is equal to p(w) = - arctan(w) and the time delay is 1/(1+w^2) and then w = 1rad/sec, p(1) = 135º and T(1) = 1/2 seconds What does it mean? What does T(w) represent?

[@abidurrahman6195]

This is too good. Can you please provide a video on The Goertzel Algorithm for specific DFT points? That would be much appreciated.

[@iain_explains]

Thanks for the suggestion. I've put it on my "to do" list (although I should warn you it's getting to be a long list ...)

[@tranhuuthong07]

Great tutorial, thank you!!!

[@iain_explains]

Glad it was helpful!

[@bran_rx]

I swear my professor assumes we know all this stuff straight off the bat... thanks

[@iain_explains]

I'm glad the video was helpful. Have you seen my webpage, which lists all the videos in categorised order? It might help to fill the gaps that your professor assumes you already know. iaincollings.com

[@Youshisu]

2:58, where have you lost f param? with tau? and how did that pi end up there? 1/(4f) = T/4, and T is 1, so why -pi/2

[@Youshisu]

nvm im dum, did not saw other part and though its coma :D

[@Anonymous____________A721]

Oh my god, u are my god, excellent ❤

[@iain_explains]

I'm so glad to hear that the videos are helpful to you.

[@stephenflatham1122]

what is the condition for the wireless system to be a nonlinear phase system?? and what if the same copies of the frequency is delayed by different amount does in that case the system becomes non linear phase

[@iain_explains]

Wireless channels are generally modelled as being linear (with linear phase). I'm not sure what you mean when you say "the same copies of the frequency". I think you are referring to multi path propagation. In this case, it's still a linear channel. This video might help: "What is Intersymbol Interference ISI?" kzbin.info/www/bejne/f2GbaHmLq7xlr9U

[@subhashishbarik4319]

Nice videos, please keep up the good work. I have one question: On the top right figure why have you already chosen tau to be pi/2 (isn’t it supposed to be generic)? I mean, when you have extended the plot to the left (from where t = tau), you could have crossed the y-axis at a different point then -1.

[@iain_explains]

I chose tau to be 1/4 of the wavelength for the sinusoid at frequency f_1 as an example (this corresponds to pi/2), so I could show the plot clearly and explain the concept of how a time shift of a sinusoidal waveform is equivalent to a phase shift.

[@jfyt2114]

Can you please explain what happen if the phase is non linear?

[@iain_explains]

Then the signal will be distorted. It won't just be a time-delayed version of the input signal.

[@gangsclooney9737]

I am not able to understand why in your case when you consider a time delay, the linearity is positive with respect to change in frequency and in the textbook Oppenheim and Wilsky, Signals and Systems, 2nd edition, Chapter 6, pg 428 the linear phase for time delay in frequency response is

[@iain_explains]

Sorry, I should have made that clearer. It can be confusing. I defined the phase, theta, to equal (2 pi f tau). Which means the formula for a shifted sinusoid is sin(2 pi f t - theta). Other people prefer to write a phase-shifted sinusoid as sin(2 pi f t + theta). The only difference is that their "theta" would be the negative of my "theta" (ie. their "theta" would equal -(2 pi f tau) ).

[@iain_explains]

Here's a video where I included the negative into my definition of "theta", and the phase has a corresponding negative slope: "Is Phase important in the Fourier Transform?" kzbin.info/www/bejne/jaqpgGmvd7Zjeck

[@mnada72]

Thank you for the explanation. For a system, is linear phase good or bad ?

[@iain_explains]

This video should help: "When is Linear Phase Important?" kzbin.info/www/bejne/bHbOl3SBiZqiick

[@mnada72]

@@iain_explains Thank you. It seems that in most cases it's good 👍. Is there a situation where linear phase is bad ?

[@iain_explains]

It's bad if you're trying to design a distorting amplifier, to create odd/interesting sounds. Like a sound-effects foot-pedal of an electric guitar, for example.

[@M0XYM]

This is teaching at its finest - thank you. I have just finished the "Basic Signal Concepts" and am wondering which playlist I should next follow - do you have a recommendation? My motivation for learning DSP is that I am an amateur radio enthusiast and would like to understand more about SDR (software defined radio) and eventually process signals from a SDR with python/matlab/gnuradio - but that's after I understand the basics! So - can you recommend a playlist order please? Thanks again Kevin M0XYM.

[@iain_explains]

Hi Kevin, I'm glad you like the videos. The usual topic order would be: Convolution; Fourier Transform; Delta Functions and Sampling; Sampling Continuous Time Signals; Communication System Fundamentals.

[@alisharafi1225]

Great tutorials. But I would be grateful if u help me with explanation of difference between generalized linear phase and linear phase. However I know their equation are different!

[@iain_explains]

Systems with generalized linear phase have an additional frequency-independent constant added to the phase.

[@MrFab0117]

Very good Thanks ! I should be very interesting by an presentation of hilbert filtering ( constant phase at pi/2 for every frequencies) ; for example to creat I/Q values with a mixer. Thanks in advance 🙏😊

[@iain_explains]

Thanks for the suggestion. I'll have to think a bit about that one. I always like to give intuitive insights in my videos, and the Hilbert transform is certainly one of the less-intuitive transforms. I'll put it on my "to do" list.

[@MrFab0117]

@@iain_explains You’re right, I have no doubt you’ll find the good way to explain us this particular transform. Thanks again 🙏😌

[@ashilpasha6867]

Sir please make video on AGC working on OFDMA.

[@iain_explains]

Thanks for the suggestion, I'll add it to my "to do" list. The topic is covered to an extent (for single user OFDM) in the video "What is PAPR? and its relationship to OFDM" kzbin.info/www/bejne/fGWvco2KmdKSmJo

[@hyggeligt007]

Hi Iain, thanks for the intuitive explanation. What could be the benefit of having linear phase? Is it simply to avoid communication delays (if any), in real time applications. Are there times where having a linear phase brings no tangible benefits to the table?

[@iain_explains]

An example of when it's important to have a linear phase response is in Bandpass Filtering. The aim is to pass the signals in the frequency band of interest (unchanged - apart from an unavoidable time delay), while also completely suppressing any signals that are not in that frequency band. In this case you want to have a flat amplitude spectrum and linear phase response across the frequency band of interest, and have a zero-amplitude response across the rest of the frequency spectrum. Thanks for raising this question. I think I might add this topic to my "to do" list for a future video.

[@hyggeligt007]

@@iain_explains Noted, I'll read up a bit more on the theory as well. As an example, phone lines can have a pass band between 200 Hz to 8 kHz (focused on speech and syllable information). If the filter is designed to have non-linear phase, the speech frequencies lying between that could probably cause unintended interference at the receiver's position, making the caller sound different. Mainly because linear phase implies a constant delay between input and output, whereas the delay would not be constant for non-linear phase (?) Perhaps a better example could be in diagnosis of patient data with some monitoring tool (like cardiogram or ECG), where the interference could lead to erroneous interpretation by the doctor.

[@iain_explains]

Yes that's right.

[@ihya1129]

Sir, can you explain about Sine PWM : Triangle wave compare with sine wave, and Related Bessel Function for Harmonic

[@iain_explains]

Thanks for the suggestion. I've added it to my "to do" list.

[@abhishekpratap7744]

Nice thank you

[@iain_explains]

You're welcome

[@ayushthakur3280]

Love from India 🇮🇳

[@iain_explains]

Thanks. I'm glad you like my video. Right now I'm watching the fourth day of the 4th cricket Test between Australia and India. It's very close!