43 votes
Accepted

Why sample at a certain frequency just to immediately downsample it?

if they wanted the sampling frequency to be 10Hz, why did they not just sample at 10Hz initially? In order to avoid aliasing, the signal has to be lowpass-filtered before sampling. No frequencies ...
  • 63.2k
33 votes

When is it required or permitted to sample below Nyquist rate

First of all, let's get rid of the Nyquist rate misconception. People are usually taught that the minimum sampling frequency needs to be twice the frequency of the highest frequency in the signal. ...
  • 22.9k
29 votes
Accepted

Word or phrase to describe how frequently a value is measured

The name for the frequency the samples are taken is Sampling Rate (not specific to audio only). It is measured in samples-per-second or in Hz (which is ...
  • 9,771
25 votes

How is 10G Ethernet physically possible?

Chasing this answer down took a few different links, but it appears to boil down to this: 1. 4 differential pairs (8 wires total, but only 4 lanes). 2. 800 Mega Symbols a second. 3. Using PAM16, 16 ...
  • 12.5k
24 votes
Accepted

Why does increasing the sampling rate make implementing an anti-aliasing filter easier?

As you decrease the sampling frequency there is less separation between the images in the frequency domain. source Remember that the repetition of the spectrum occurs at the sampling frequency. When ...
  • 5,954
23 votes
Accepted

Can sampling rate be a floating point number?

Forget sampling rate for a few seconds... Think about sampling period for a second, which is the time interval between two consecutive samples. This time can be an integer or any real number (as long ...
  • 2,167
20 votes

Word or phrase to describe how frequently a value is measured

I would call it the sampling period or measurement period. For short periods like 1 ms, specifying the sampling frequency is another option (1 kHz).
  • 5,846
19 votes
Accepted

Lossless compression technique for digital signals in an embedded system

Compression is all about finding the redundancies in the data and removing them. Since you don't seem to be able to tell us much about your actual data sets, this answer will have to be very generic. ...
  • 165k
18 votes
Accepted

Can the Nyquist sampling rate also apply for the human eye the same as in electronics?

The firing of neurons in the eye is completely asynchronous, so for all intents and purposes, the process we call "seeing" must be considered continuous-time, not sampled. Nyquist does not apply. If ...
  • 165k
18 votes
Accepted

What is the "Nyquist" rate for sampling the derivative of a signal?

Taking a derivative (or an integral) is a linear operation — it doesn't create any frequencies that weren't in the original signal (or remove any), it just changes their relative levels. So the ...
  • 165k
15 votes

How is 10G Ethernet physically possible?

10G ethernet (as described by other answers) does not do signal transitions at 10 GHz, it uses multiple level encoding spread across 4 pairs to achieve 10 Gb/s. However, 10+ gigabit serial ...
  • 2,389
14 votes

Can sampling rate be a floating point number?

Yes, the sampling rate can be any number you want. But you obviously would not get partial samples in the end, you just have to round down. In your example the first sample is taken at \$ \frac{1}{15....
  • 8,668
13 votes

Why do digital scopes sample signals at a higher frequency than required by the sampling theorem?

There's a difference between analyzing a signal for information, and displaying it on a scope screen. A scope display is basically a connect the dots, so if you had a 100 MHz sine wave sampled at 200 ...
13 votes

When is it required or permitted to sample below Nyquist rate

So, many people, including professors, are confused about what Nyquist rate is: Nyquist rate is the sample rate that you need to have to sample a signal to avoid damaging it by aliasing What that ...
13 votes

Can sampling rate be a floating point number?

Some things are always an integer. Samples are always integer. You can take 108 or 109 samples. Sample rate can be a floating point number, or more generally a rational, or even a real. You ...
  • 145k
11 votes
Accepted

Anti-Aliasing filter design

If you are interested only in signals in the range DC to 3kHz, then only signals above 7kHz will alias onto those. This means that you need a filter with ... a passband to 3kHz a transition band ...
  • 145k
10 votes
Accepted

Why do digital scopes sample signals at a higher frequency than required by the sampling theorem?

"even a simple UART samples a digital signal at the same speed..." the UART doesn't need to reconstruct the analog square wave signal that carries the digital information, so it doesn't take the ...
10 votes

STM32F20x ADC sampling time/rate

I'll let you work out the details for your particular case, but I'd like to add some more clarity. First off, I've opened up an errata report on RM0410 (the reference manual for my chip) here. I'll be ...
10 votes

Why sample at a certain frequency just to immediately downsample it?

You mentioned the word magnetometers. This expands the scope a little. Magnetometers for those not familiar measure magnetic flux and create a proportional output voltage/ signal according to the ...
10 votes

Sampling rate understanding for ADC requirement

In order to capture all the information you need to sample at at least twice the highest frequency component in the input signal. If you do a PSD plot of the input you'll see that there is ...
9 votes
Accepted

Why doesn't aliasing of broad band noise 'pile up' in the sample band?

You are correct: after sampling, the aliased noise components do pile up in the frequency band below the Nyquist frequency. The question is just what exactly it is that piles up, and what is its ...
  • 3,613
9 votes

16-bit or 24-bit converters?

There is a lot of bad information and audio phoolery available on this topic, but if you're doing one channel of digital audio, 96kHz and 192kHz sample rates are silly. Human hearing extends to 20kHz. ...
  • 13.6k
9 votes
Accepted

Meaning of unevenly spaced data points in LTspice

My guess is that these are the (time) points which the circuit simulator has actually solved. Many analog circuit simulators, unlike simulators for digital circuits (logic), do not use a constant ...
  • 79.1k
9 votes

Why does increasing the sampling rate make implementing an anti-aliasing filter easier?

To reconstruct a signal in the digital realm from the analogue realm you need at least two samples in each cycle of the highest frequency present in the analogue signal. For instance, on CDs, they use ...
  • 395k
9 votes

Lossless compression technique for digital signals in an embedded system

Your data will likely have two components to it: Low speed changes of the actual voltage Random variation due to ADC noise It is likely that the random variation will present most of the entropy in ...
  • 5,038
9 votes
Accepted

Shannon-Nyquist - only for repeating signals?

if you decompose a signal into sinusoids, and then sample at 2x the highest frequency sinusoid, you can perfectly reproduce the original signal. If the signal can be perfectly decomposed into ...
  • 145k
8 votes

Relationship of FFT Size, Sampling Rate and Buffer Size

There is a direct, and actually quite simple, relationship between all the figures. Let's start with the sample size. The numbers of bins (or "buckets") is equal with half of the samples in ...
  • 55.6k
8 votes
Accepted

16-bit or 24-bit converters?

It depends on who you ask. Most humans cannot hear beyond 20 kHz and 16 bits, so 96 or 192 kHz should be plenty. As for hearing a difference between 16 and 24 bit converters it depends on your DSP. ...
  • 1,842
8 votes

Exactly what is the role of the zero-order hold in a hybrid analog/digital sampled-data system?

Set-up We consider a system with an input signal \$x(t)\$, and for clarity we refer to the values of \$x(t)\$ as voltages, where necessary. Our sample period is \$T\$, and the corresponding sample ...
  • 1,117

Only top scored, non community-wiki answers of a minimum length are eligible