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Nyquist????

Hi everyone, What is the dirrerence between nyquist frequency, nyquist rate and nyquist bandwidth? I am sure that they dont point to the same concept. I know what is a nyquist frequency. But I am not able to understand the concept of the other two. I came across these terms while learning about pu...

Implications of Nyquist? ?????

_TYPICALLY_ when looking to satisfy "Nyquist criterion" one looks to sample a waveform at > = a particular frequency. I've gut feeling that Nyquist implies more. I suspect it's more about information transfer rate. What question should I be asking. Signed ADMITTED *STUPIDENT* ...

Nyquist Condition question.

Hi all, (1) I know the famous Nyquist Condition, f(t) with bandwidth B is sampled without aliasing if Fs> 2B. Today I read another thing called Nyquist Condition which says: for a continuous time signal x(t), take x(t) convolute with itself and then sample the obtained signal at Fs, ...

Re: Interpolation

On 2 Apr., 12:36, Randy Yates wrote: > dbd writes: > > [...] > > .How can a 'properly designed' decimation filter not anti-alias when > > .there is input signal content above the Nyquist frequency of the > > .downsampled sampling frequency? > > Dale, > > Here's an interes...

nyquist sampling rate

hi all. i have a signal of bandwidth 2 MHz on a carrier of 5 MHz. That means the Nyquist sampling rate is (5+2/2)*2 = 12 MHz. But I have heard that it is not a good idea to sample on or near nyquist rate because of the sinx/x roll of charactersistics of ADC. Please guide should i oversample it ...

Re: Interpolation

On Wed, 2 Apr 2008 04:12:06 -0700 (PDT), Andor wrote: > On 2 Apr., 12:36, Randy Yates wrote: > > dbd writes: > > > [...] > > > .How can a 'properly designed' decimation filter not anti-alias when > > > .there is input signal content above the Nyquist frequency of the > > > ...

Re: numerical precision of FFTs when interpolating

Ok, I've found the problem, thanks to the useful suggestions. It's not the FFT, it's how I am zero padding, or rather stuffing. I've found the following guide on zero-stuffing: http://www.dspguru.org/howto/tech/zeropad.htm It tells me to stuff the zeros after N/2 frequencies, i.e. just before...

Nyquist sampling theorem

Hello, I read in the text book ("Digital signal Processing Principles, Algorithm and APplications" J. G. Proakis % D. G. Manolakis, page 30) that the Nyquist frequency (rate) is a double of the highest frequency of the signal. In the web, I learn that it is the double of the bandwith. Moreover ...

Re: questions raised by reading and thinking with possibly missing background

abariska@student.ethz.ch wrote: > > > Since Fs = Ts = 1, I don't see a difference between sinc(t+1/7) and > > > sinc(n+1/7) ? > > ... > You claim that the infinitely long sequence > > b[n] = sinc(n + 1/7), > > for all n, is linear-phase. That could be true. Do you have an ide...

Nyquist rate for sampling complex-valued data?

I (vaguely) heard that sampling complex-valued data does not abide by the Nyquist rate criteria, i.e., the sampling rate fs can go lower than Nyquist rate and it still can avoid aliasing and reconstruct perfectly... Is that true? Any theory behind it? Thanks a lot ...

Re: Assymmetrical IIR bandpass filters doable?

On Jun 13, 9:11=A0pm, "gelliot" wrote: > > What I was wondering if someone can tell me if it is possible to create a > single IIR filter not greater than 4th order, or close to it, that can do > the same thing? Can an IIR be made with an intentionally assymmetrical now the way that the...

Nyquist constrain and IQ represented signal

Hello, there is a question that bugs me for quite a long time: You can read about Nyquist constrain online, that to reconstruct all frequencies within a signal, it has to be sampled with at least twice the bandwidth _or_ maximum frequency. Maybe this _or_ is already the problem... Let's se...

Nyquist Pulse

Nyquist pulse criteria states that the summation of the spectrum of pulse shapes should be flat. But if we see in time domain there are many pulse shapes that satisfy the nyquist criteria and they dont have a spectrum that's summation is flat. For example, triangular function f = { t + T for -...

Sampling Theorem history

It is generally credited that the Sampling Theorem is due to fistly the Mathematician Whittaker and Shannon and the Russian Kotelnikov. I have no doubt that Whittaker was first but was Shannon aware of Whittakers work? Also where does the Russian engineer fit in? What role did Nyquist play. We t...

is normalizing FFT magn spectrum different for Nyquist-frequency's bin?

Hi Experts, Let's say I compute the FFT magnitude spectrum of a variable X(n) in Matlab, where X(n) has indices n running from 1 to N. The magnitude spectrum is plotted for indices n = 2 (ignoring DC index n=1 for now) to n = N/2 + 1 (e.g. the Nyquist frequency bin). To get the normalizatio...

Information request about sub-Nyquist and irregular sampling

Hi, I am new to signal processing and have very simple question. Where can I find a brief explanation about sub-Nyquist and irregular sampling. I searched the web by almost all possible keywords, but what I found is not so useful. It would be very nice if you give me some book titles. Thanks i...

Re: Interpolation

On Fri, 4 Apr 2008 10:58:49 -0700 (PDT), robert bristow-johnson wrote: (snipped by Lyons) > > possibly you're right. but i think the term is nearly universally > understood as Fs/2 (or z = -1 on the unit circle or pi in normalized > omega, but not "1" as stupid MATLAB scales it) and i...

Re: signal fades in noise

On 28 apr, 06:31, I am not Einstein wrote: > I changed the input cabling and reduced > the sampling rate, it is okay now. Will reducing the sampling rate > improve the signal? No, it will not. You said somewhere that you sample at 3x 'the frequency'. If that 'frequency' is the Nyqui...

Re: Questions about equivalents of audio/video and digital/analog.

On Sat, 25 Aug 2007 06:16:10 -0800, floyd@apaflo.com (Floyd L. Davidson) wrote: > > > > I guessed you would think it was correct. You can't sample at a rate > > equal to twice the frequency you are sampling. The wanted signal has > > collided with its image and you can't disambiguate them. T...

Re: Questions about equivalents of audio/video and digital/analog.

On Mon, 20 Aug 2007 22:14:45 -0800, floyd@apaflo.com (Floyd L. Davidson) wrote: > > source that you claim is authoritative and impeccable. Kindly go and > > read what it has to say on the Nyquist rate and come back and repeat > > that claim without blushing. Actually I'm betting you won't blus...

Re: decay rate of the spectrum?

Luna Moon wrote: > Hi all, > > If I have the signal not in closed form, but in form of some > collected data. > > The sampling(or collection) of such signal data points are very > costly. > > Thus we want to minimize the number of samples(data collection). > > Is there a wa...

Johnson Nyquist Noise

Hello All, I had a recent situation where I needed to write a paper explaining the why's and wherefores of Johnson noise. So if you are interested, the following link will take you to my paper. http://www.claysturner.com/dsp/Johnson-Nyquist%20Noise.pdf Any and all comments welcome. ...

Re: Nyquist theorem and Sampling rate of signals (Newbie)

On Fri, 29 Oct 2010 00:26:21 -0700 (PDT), Deamon wrote: > Please I am a complete newbie in Signal analysis and modelling and I > am quite confused about the use of Nyquist theorem in sampling .Does > this Nyquist criterion affect the rate at which data is transferred > that is the data...

I wonder if there is a spatial Nyquist sampling theory?

Is there a Nyquist sampling theory for spatial dimensions? Suppose point A to point B is about 1 mile, how many sensors I should place to get a fair estimation of the property of the whole range? ...

How to create peak/shelf filters, that are symmetric close to nyquist?

Hi, is it possible to modify biquad peak/shelf filters, so that they have approximately the same shape allover the spectrum. Normally they start to "narrow" the closer they are to nyquist. I have checked it can more or less be compensated by combining multiple filters, but that's pretty much an a...

Re: Questions about equivalents of audio/video and digital/analog.

Floyd L. Davidson wrote: > Jerry Avins wrote: > > Floyd L. Davidson wrote: > > > > ... > > > > > Nyquist rate: > > > The reciprocal of the Nyquist interval, i.e., the > > > minimum theoretical sampling rate that fully > > > describes a given signal, i.e., ena...

Nyquist frequency in FFTs

Hello all, I noticed that all FFT routines transform a time array into a frequency array of the following form: F[0], F[n/2], real:F[1], imag:F[1], real:F[2], imag:F[2], etc.. Now the question is, why does "F[n/2]" (the nyquist freq) appear as the second term, and more importantly, what i...

Cycles/inch frequency, really confused, plz help!!!

Hello all, I am really confused with how people calculate the spatial feq values in FFT: Assume I have a continuous signal f(x), in spatial domain. I need to know at what freq (cycles/inch) the flactuation is the most dominant (highest). Assume that freq is f_d. Firstly I sample it wit...

Nyquist Lth band digital filter... IPlease!! ... I need answers

Hello everybody Before I ask my question I want to tell everybody that I'm new in the area of DSP. Now, here is my question: Can somebody tell me why the "Nyquist Lth band digital filter" is better than the "raised cosine one"?. Or perhaps, somebody can tell me what are the good and bad featur...

Re: A DSP Decimation Riddle

> When is decimating by N not equivalent to decimating by 2*N followed > by interpolating by 2? I think, except for a handful of pathological cases, any time bandwidth > = Fs/4N. For example, try it with a sine wave (NOT a cosine wave) of frequency Fs/4N. Decimate by N and Nyquist is sti...

definition of "Nyquist frequency" (was Re: Rick's 3rd edition is out)

On Nov 17, 6:13=A0am, Rick Lyons wrote: > On Tue, 16 Nov 2010 06:20:44 GMT, Al Clark > wrote: > > > I just noticed that Rick Lyon's 3rd edition of Understanding Digital Sig= nal > > Processing is out, so I guess I will have to get a copy to place next to= the > > 1st & 2nd editi...

Need Phase-Lead filter.

I need a digital filter or sequence of digital filters with the following response: Amplitude flat across all frequencies up to the Nyquist (folding) frequency. Phase starts at 0 degrees at low fregs linearly increases with frequency until it is 180 at the Nyquist (folding) frequency. ...

choosing a sampling rate lesser than nyquist rate(sub nyquist rate)

Hello, I have a signal consisting of 4 harmonics (200k,400k,600k,and 800k Hz) and dc component.The signal is very pure and SNR better than 60 dB. I have to sample it in sub Nyquisit rate(lesser than 1600k). What sampling rate should i choose so that there no alaising. I cannot chose higher samp...

Re: downsampling -> FFT -> upsampling

> Consider your idee fixee: if every second sample of a set of valid > samples is discarded, the result is still a set of valid samples. How > many times in a row would you apply that theorem? Why stop there? I'm not saying it's "the same". If I said that then I expressed myself wrong. What...

Low freq "analog" of Nyquist? ( possibly naive question )

I understand Nyquist specifying a minimum sampling rate to determine the high frequency component of a signal. What happens at at the other end of the spectrum? I.E. Is there a minimum time window required? E.G. If the signal has a significant 1 Hz component and sample window was .1 sec...

Low pass filter at half Nyquist

Hello, I'm currently using an FFT to zereo out all the frequences above half Nyquist for my application. It makes perfect cutoff, but I have to use buffers and the old overlap/add to remove clicks. My question to you good folks - is there a clever 'trick' to cut frequencies off above this s...

Nyquist Sampling

I'd like to ask a couple very basic questions. Being hands-on rather than mathematically-focused I'm trying to visualize sampling in a project I'm planning to start. 1. By sampling say a 3.1 kHz band-limited voice channel at the Nyquist rate am I guaranteed to capture *all* the information...

Re: Designing a programmable filter for a wide range of bandwidths

On Jun 9, 5:09=A0pm, "ProfNimrod" wrote: > > PS As a separate question can someone give me some insight into how > decimation affects the frequency spectrum of the decimated signal? decimation is like sampling it again (at a lower sampling frequency). let's say you decimate by a factor ...

Re: IIR audio filterbank

On Oct 13, 2:08=A0pm, dbd wrote: > On Oct 12, 5:54 pm, Robert Adams wrote: > > > ... > > I can do a "seat-of-the-pants" design that > > works well until I approach Nyquist where it kind of falls apart. I > > have very limited MIPs so I can't do anything very fancy. Any > > p...

What Nyquist Didn't Say

I've seen a lot of posts over the last year or so that indicate a lack of understanding of the implications of the Nyquist theory, and just where the Nyquist rate fits into the design of sampled systems. So I decided to write a short little article to make it all clear. It's a little longe...