Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

The Fourier Transform and its Applications

see.stanford.edu

Post reply on HN
Print view View original

21–30 of 60 posts

Re: The Fourier Transform and its Applications

#21

Post by jokoon »

I think I remember that the fourier transform is used to send a signal across a analog line, for DSL modems, after it's converted from binary.

Since analog lines may not have the same frequency response when it comes to interference, the modem usually tests the analog lines at various frequencies, and only keeps the intervals who are good enough to transmit.

I wonder if the FFT is used for wifi, since wifi passes through an analog signal.

Although I'm not even sure of what I'm talking about is true or relates to fourier.

Re: The Fourier Transform and its Applications

#22

Post by notalaser »

Zombieball wrote: post #16
farhanhubble wrote: post #8

This is an exceptional course. In my CS undergrad days, some 7 years ago, when I wanted to make sense of Fourier Series and Transform, this course was my savior. The mathematics text book had a dry and unintuitive treatment of the topics and electrical engineering, physics and computer science books mostly relegated the topics to a few pages in an appendix. I found this course and printed out the PDF of the lecture n…

> electrical engineering, physics and computer science books mostly relegated the topics to a few pages in an appendix. Out of curiosity, is this really true? Perhaps I misunderstand you, but I have always been under the impression that Fourier Transform was a fundamental building block covered extensively in all EE curriculum? I took Computer Engineering with some classes shared between Comp. Eng. and EE students. I…

I don't know about physics, but it's definitely not true about electrical engineering. The Fourier transform is one of those things that is absolutely fundamental to any branch of electrical engineering, you run into it when doing anything, from microelectronics to power distribution. And there's typically no way you get an EE diploma without a soul-wrenching course on signals & systems.

As a personal anecdote: I ended up taking three courses: one on signals, one on systems, one on circuits (...and systems!). During those troubled uni years, trying to see if I can still remember the Fourier transform was my "am I too drunk?" benchmark. When I could no longer do it, I went home.

Re: The Fourier Transform and its Applications

#23

Post by [deleted] »

notalaser wrote: post #22
Zombieball wrote: post #16

Earlier quoted context omitted.

> electrical engineering, physics and computer science books mostly relegated the topics to a few pages in an appendix. Out of curiosity, is this really true? Perhaps I misunderstand you, but I have always been under the impression that Fourier Transform was a fundamental building block covered extensively in all EE curriculum? I took Computer Engineering with some classes shared between Comp. Eng. and EE students. I…

I don't know about physics, but it's definitely not true about electrical engineering. The Fourier transform is one of those things that is absolutely fundamental to any branch of electrical engineering, you run into it when doing anything, from microelectronics to power distribution. And there's typically no way you get an EE diploma without a soul-wrenching course on signals & systems. As a personal anecdote: I end…

[deleted]

Re: The Fourier Transform and its Applications

#24

Post by farhanhubble »

Zombieball wrote: post #16
farhanhubble wrote: post #8

This is an exceptional course. In my CS undergrad days, some 7 years ago, when I wanted to make sense of Fourier Series and Transform, this course was my savior. The mathematics text book had a dry and unintuitive treatment of the topics and electrical engineering, physics and computer science books mostly relegated the topics to a few pages in an appendix. I found this course and printed out the PDF of the lecture n…

> electrical engineering, physics and computer science books mostly relegated the topics to a few pages in an appendix. Out of curiosity, is this really true? Perhaps I misunderstand you, but I have always been under the impression that Fourier Transform was a fundamental building block covered extensively in all EE curriculum? I took Computer Engineering with some classes shared between Comp. Eng. and EE students. I…

I don't have an EE degree. At my university in India, we had 2-3 basic courses from EE and Signal and Systems as part of the CS curriculum. Although I don't remember the exact textbooks used, I'm pretty sure both courses covered Fourier analysis but only at a superficial level.

Re: The Fourier Transform and its Applications

#25

Post by dnautics »

yagyu wrote: post #17

There is this hard question that is often glossed over in a first course on Fourier analysis: We learn that the Fourier transform of f(t) is an integral of exp(iwt)f(t) over all t. But when we look at a table of Fourier transform pairs, we find things like the Fourier transform of a constant function (is the Dirac delta). Integral does not converge? WTF? I really think Prof. Osgood hits a sweet spot of not sweeping t…

the other somewhat confusing thing is that algorithms like discrete fourier transform/fft are actually fourier series.

Re: The Fourier Transform and its Applications

#26

Post by ajkjk »

jomamaxx wrote: post #10
jomamaxx wrote: post #9

I 'took' the stanford NLP course online it was great. Doing this one now. Funny - I did Fourier in Comp. Eng. - but it was jammed together with so many other things, I felt overwhelmed by all of it, I did enough to do decently on the exam, but I feel a lot of it was lost on me, and I forgot much of it. Using fourier in most computer applications is very rare! I'm excited to have a project I need to use it for - and w…

The prof noted that it's almost all EE folks, with a few others, but didn't mention Comp Sci. Can anyone comment on why there were seemingly no Comp Sci people in this class? Wouldn't this be 'core' to Comp Sci?

I don't see Fourier Transforms as core to CS at all. The FFT algorithm is an important algorithm, and I've seen it mentioned as one of many subjects in an upper-level algorithms class, but that's it.

Re: The Fourier Transform and its Applications

#27

Post by freyr »

jokoon wrote: post #21

I think I remember that the fourier transform is used to send a signal across a analog line, for DSL modems, after it's converted from binary. Since analog lines may not have the same frequency response when it comes to interference, the modem usually tests the analog lines at various frequencies, and only keeps the intervals who are good enough to transmit. I wonder if the FFT is used for wifi, since wifi passes thr…

Yes, Wi-Fi uses the FFT. In wireless systems, the method is known as OFDM (orthogonal frequency division multiplexing).

Re: The Fourier Transform and its Applications

#28

Post by enriquto »

dnautics wrote: post #25
yagyu wrote: post #17

There is this hard question that is often glossed over in a first course on Fourier analysis: We learn that the Fourier transform of f(t) is an integral of exp(iwt)f(t) over all t. But when we look at a table of Fourier transform pairs, we find things like the Fourier transform of a constant function (is the Dirac delta). Integral does not converge? WTF? I really think Prof. Osgood hits a sweet spot of not sweeping t…

the other somewhat confusing thing is that algorithms like discrete fourier transform/fft are actually fourier series.

The discrete fourier transform is actually finite-dimensional linear algebra.

No infinite series nor convergence problems here.

Re: The Fourier Transform and its Applications

#29

Post by madengr »

Zombieball wrote: post #16
farhanhubble wrote: post #8

This is an exceptional course. In my CS undergrad days, some 7 years ago, when I wanted to make sense of Fourier Series and Transform, this course was my savior. The mathematics text book had a dry and unintuitive treatment of the topics and electrical engineering, physics and computer science books mostly relegated the topics to a few pages in an appendix. I found this course and printed out the PDF of the lecture n…

> electrical engineering, physics and computer science books mostly relegated the topics to a few pages in an appendix. Out of curiosity, is this really true? Perhaps I misunderstand you, but I have always been under the impression that Fourier Transform was a fundamental building block covered extensively in all EE curriculum? I took Computer Engineering with some classes shared between Comp. Eng. and EE students. I…

I'm an EE, and had a course specifically on Laplace and Fourier analysis.

Re: The Fourier Transform and its Applications

#30

Post by SixSigma »

wyldfire wrote: post #3
tptacek wrote: post #2

In case this is useful to anyone else: There's probably an easier way to do it, but if you want to get faster playback (2x is about as fast as I can comprehend this lecturer at), this line seems to do the trick: document.getElementById("myElement").querySelector("video").playbackRate = 2

Not sure if the browser playback supports it but lots of other native programs like VLC do a pitch-compensation/"time-stretching" mode that will make the faster playback easier to live with.

Pressing [ or ] in VLC changes the playback speed in 0.1x increments goes up to at least 10x
Post reply on HN