Timeline for Nyquist Frequency
Current License: CC BY-SA 3.0
15 events
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| May 23, 2013 at 15:53 | comment | added | Kristian | Just wanted to thank you both for the interesting discussion (I am user12277 btw :)). It's educational for me to see that there are various definitions out there regarding this, so that I can keep this is mind when I run into this in the future. | |
| May 23, 2013 at 15:10 | comment | added | Jim Clay | I have a copy of Oppenheim-Schafer DSP and so I looked it up. You are correct that they define the Nyquist frequency based on the signal-of-interest, and not the sample rate. I believe that they are wrong to do so, and that it is contrary to the general usage of the term. | |
| May 23, 2013 at 15:05 | comment | added | Jim Clay | As long as we define "signal" to be "whatever is in the samples" (i.e. not just the frequency band that you care about), then I believe they are consistent. I agree with the definition given at the Wikipedia page for Nyquist frequency: "The Nyquist frequency, named after the Swedish-American engineer Harry Nyquist, is ½ of the sampling rate of a discrete signal processing system." | |
| May 23, 2013 at 14:48 | comment | added | Mostafa | @JimClay Now I understood what you are saying! But , in my textbook ( Oppenheim-Schafer DSP, 3rd ed., 2010) it is mentioned that Nyquist frequency= half of the Nyquist rate=maximum freq of the signal.Which is correct? | |
| May 23, 2013 at 14:44 | history | edited | Mostafa | CC BY-SA 3.0 |
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| May 23, 2013 at 14:18 | history | edited | Mostafa | CC BY-SA 3.0 |
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| May 23, 2013 at 13:43 | comment | added | Mostafa | @JimClay Thanks for reminding me! Corrected the first line (I should use the term rate there). I think I'd better to explain more about the difference of these two terms in the answer. | |
| May 23, 2013 at 13:41 | history | edited | Mostafa | CC BY-SA 3.0 |
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| May 23, 2013 at 12:42 | comment | added | Jim Clay | -1. You understand the concepts correctly, but you are using the term "Nyquist frequency" incorrectly. The Nyquist frequency is set by the sample rate. The signal bandwidth determines the sample rate that you need to reconstruct the signal, as you say, but it does not set the Nyquist frequency. That is done by the sample rate. | |
| May 23, 2013 at 7:47 | history | migrated | from physics.stackexchange.com (revisions) | ||
| May 22, 2013 at 18:18 | vote | accept | CommunityBot | ||
| May 22, 2013 at 18:18 | comment | added | user12277 | Great! Thanks a lot. So the book is somewhat confusing then. It's not me there's something wrong with :). Appreciate it a lot! | |
| May 22, 2013 at 18:17 | comment | added | Mostafa | You are right,as I have written in the last paragraph, it is Nyquist rate (=2*Nyquist frequency).corrected! | |
| May 22, 2013 at 18:09 | comment | added | user12277 | Thanks a lot. I must admit I am still a little confused. You write: "if you want to be able to reconstruct the original from its samples, you have to sample with a frequency more than Nyquist frequency". But shouldn't it be "Twice the Nyquist frequency"? Say a signal has a maximum frequency of 3 Hz. If I sample with a frequency of 4 Hz, then the Nyquist frequency is 2 Hz. So my sample frequency is higher than the Nyquist frequency, but I still would not be able to properly reconstruct the 3 Hz frequency. Isn't that right? I'm very sorry for the confusion. This is new to me :) | |
| May 22, 2013 at 17:47 | history | answered | Mostafa | CC BY-SA 3.0 |