Questions tagged [sampling]
In signal processing, sampling is the reduction of a continuous-domain signal to a discrete-domain signal.
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Sampling interval $T$ as a multiplier in digital processing of a continuous-time signals
[from: Discrete-Time Signal Processing, Oppenheim and Schafer, p.224]
Q: Why do we have $T$ as multiplier in $TY_a(j\Omega)$ in Eq.155?
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Partial column approximation error
Can someone help me understanf how to plot the next partial column in MATLAB:
while N=2001
|M|<700
ak =
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2answers
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Under what conditions is there a one-to-one mapping between continuous-time and discrete-time signals?
As the sampling theorem dictates that the uniform sampling frequency must be at least twice the maximum frequency present in the bandlimited signal (Nyquist rate), a question arises about the ...
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573 views
Are resolution increase and noise reduction from oversampling mutually exclusive?
Oversampling a signal means sampling it with a significantly higher sampling frequency than the Nyquist rate. As far as I know, there are three advantages:
Easier design of anti alias filter
Increase ...
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Spectral Analysis of a Time Series with Missing Data Points
I use a PC to record time series of some physical property. The problem is that, for some reason, I did not record the time series as a whole, rather I record first segment, then second, third, etc. ...
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How to measure correlation between 1 bit samples and theoretical original waveform?
I'm investigating quantization error.
I have an analogue waveform that looks like this and is of theoretically infinite resolution:-
I've sampled it at a 1 bit resolution (as 8 bit oscilloscope ...
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8answers
268 views
How Do I Measure the Time Duration of a Finite Length Discrete Sequence?
Assume I have a five-sample time-domain sequence (none of the five samples are zero valued) and the time period between each pair of samples is one second. Measured in seconds, what is the time ...
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Why Is the Total Time Equal to $ N \cdot {T}_{s} $ and Not $ \left( N - 1 \right) \cdot {T}_{s} $ In the Context of DFT?
In the definitions of the DFT
DFT
$$
X(j)=\sum_{k=0}^{N-1} x(k) \exp \left(-i 2 \pi\left(\frac{j}{N}\right) k\right)
$$
Let us say, if we have $10$ points, $N=10$, each sampled at $0.2$ seconds, why ...
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145 views
Fourier Like Spectral Analysis with Uneven Intervals and Redesigned DFT Matrix
I intended to use a discrete Fourier transform (DFT) on a time series sampled at uneven intervals. What I did was to calculate a DFT matrix where the elements are the values at the uneven locations ...
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1answer
50 views
Modulation upsampling method
I try to implement a qpsk modulator in Octave.
The chain is the state of the art I guess:
$$\text{Symbol mapper} \rightarrow \text{Upsample 4} \rightarrow \text{Root raised cosine filter} $$
My main ...
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1answer
328 views
Phantom harmonics when using cosine windows why do they appear and how to avoid them?
Given an $L$ order cosine window, it is possible to show that the width of the main lobe is given by:
$$\omega_w = \frac{2 \pi L}{(2N+1)}$$
Where $L$ is the order of the window, $N$ is the maximum ...
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1answer
156 views
Continuous wavelet transform subsampling at lower frequencies?
I am not completely confident in my understanding of wavelet theory, but since I am currently in the process of creating a CWT scalogram tool, I have to ask:
Is there a theorem allowing us to ...
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3answers
537 views
Absolute convergence of periodic sinc interpolation
An $N$-periodic complex discrete-time sequence $[x_0, \dots, x_{N-1}]$ can be resampled to an $M$-periodic sequence $[y_0, \dots, y_{M-1}]$ with $M>N$, using sinc interpolation:
$$\begin{align}y_m ...
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1answer
37 views
Sampling the Wave Equation for String Vibration
I am having a difficult time understanding the basic principles when sampling the function describing the vibration of a string. Mainly I am confused on given a sampling rate how many samples to take ...
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Using oversampling to increase resolution of a DC-signal as input
Currently I'm working on a project which uses oversampling to increase the resolution of a 12 bit ADC to a maximum of 16 bits. My goal is to fully understand the theory behind oversampling and why it ...
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1answer
107 views
Recovering a signal after nonuniform sampling
Let $x(t)$ be a bandlimited signal such that $X(j\omega) =0 $ when $|\omega|>M$. Also $p(t) = p_1(t) - p_1(t-\Delta)$ is a nonuniformly spaced periodic pulse train where $$p_1(t) = \sum_{k = -\...
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1answer
396 views
Choosing a Sampling Rate and a Cutoff frequency
I have an assignment:
You wish to generate a pure 1000 Hz tone digitally using a computer. How would you choose a sample rate that assures that you could generate the tone and use the same sample ...
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56 views
Condition for aliasing
Which one of the following is the condition of aliasing?
(a) Tails of the replicas enter into the Nyquist
interval
(b) The tails of the replicas enter into the Nyquist
interval and add to the ...
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3answers
4k views
What is the difference between the sampling frequency of signal and sampling frequency of filter
I believe that there is no connection between the sampling frequency used for converting an analogue filter to digital filter and the one used to sample a signal that the filter will be used on. But I ...
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2answers
65 views
Question about aliasing
As far as I understand, you can have two different continuous-time signals with the same discrete-time frequency spectrum after they are sampled and it may be possible these shifted replicas in the ...
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1answer
101 views
Sub nyquist sampling, required number of samples for time sparse grouped signals
Question: Does it make sense to perform compressed sampling if the non zero samples are grouped in time? If so, what is the minimal length of the vector x that should be acquired to allow full signal ...
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203 views
How to make low pass filter using frequency sampling method?
https://www.allaboutcircuits.com/technical-articles/design-of-fir-filters-using-frequency-sampling-method/
So there is two main equation:
I wish to filter out frequency $\le 10000Hz$, for example. So ...
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1answer
31 views
Multiple choice on sampling and aliasing
I found some multiple choices in a well known book . The problem is that I don't get the answers in some and I want to do so.
Question 1:
The signal x(t) with Fourier transform $X(j\omega) = u(\omega)-...
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1answer
115 views
Signals sampling
I have a simple question, but sadly I'm kind of "noob" in signals theory.
A signal having 4 harmonics at the following frequencies: 1 kHz, 2 kHz, 3.5kHz and 4.2 kHz.
(How can a signal have harmonics "...
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1answer
40 views
Multisampling of an ADC channel in a PWM cycle in TI C2000
I want to sample an ADC channel multiple times in one PWM cycle.
I can trig any ADC channel in anywhere in my PWM timer counter now. But I want to trig and sample same channel in many times within a ...
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1answer
350 views
Low-Pass Filtering of not evenly sampled signal
I have a signal sampled unevenly over 1 million ns.
the signal is sampled over 1GHZ clock and the samples are as the following:
0-100 ns - sample every 1 ns.
100-1000 ns - sample every 10 ns.
1000-...
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1answer
93 views
Representing a positive 0-limiting continuous time domain function, in terms of spectral samples, outside of a window
Bit of an odd question
Assume you have a known function $x(t)$ which is continuous, but approaches but is not equal to, 0, on the interval $[-\infty,\infty]$ . You know also that it approaches 0 ...
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1answer
56 views
Multiband undersampling
In Practical Signal Processing (Marc Owen), an exercise explore the topic of undersampling:
[...] Suppose you know that an audio signal is a sine wave with a frequency that might be in one of two ...
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2answers
91 views
Phase measurement with FFT for DMM Keithley 7510
I am currenly working on a measurement driver for the DMM Keithley 7510. I implemented a harmonics measurement using FFT (from MathNet library).
First I simply sample my input voltage signal and ...
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1answer
145 views
Is this an error in Oppenheim and Schafer's Discrete-Time Signal Processing?
In Discrete-Time Signal Processing by Alan V. Oppenheim and Ronald W. Schafer (3rd Ed.), in Figure 4.47 the input of D/A converter is $\hat{y}[n]$ but later in Figure 4.64 the input of D/A converter ...
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What happens to the phase spectrum when I resample?
[An update is added at the end of the post after receiving first response]
I have an algorithm which is very sensitive to phase shifts. It works with signal sampled at 40MHz (it's a neural network so ...
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1answer
44 views
Perform frequency analysis on grouped pulses
I have a system which consists of individual pulses grouped in trains.
The trains have a frequency of 10 Hz, with a timing precision of sub ns.
The pulses have a frequency of 2.2 MHz with a timing ...
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2answers
87 views
How to select the sampling frequency when the input signal frequency is not known
I am trying to observe the noise produced by UPS present in our lab, under no load (a normal running condition when its power is on). As I don't know its frequency range, I have randomly chosen 4 ...
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1answer
250 views
Determining sampling rate for signal reconstruction
I want to know how to determine the signal sampling rate required to reconstruct electrical signals whose frequency components are unknown, such as, for example, signals of charge/discharge voltage on ...
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2answers
151 views
Multiple different length Windows for high resolution realtime FFT
I am looking at trying to achieve a 'realtime' (as quick as possible to acquire, process and present data) FFT application to analyse audio.
I have setup my app to acquire a set of samples, apply a ...
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Optimal sampling rate for the HMM forward-algorithm
I have a system with a binary-state. The system state is estimated by an HMM forward-algorithm. Also, the system allows a varying sampling rate.
Considering that the system state transition takes a ...
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3answers
632 views
Upsample / Downsample a Signal from 1920.93Hz to 1920Hz [duplicate]
I've just learned that the A/D converter I am using is not sampling at my desired sampling rate. I request 20 seconds of data at 1920Hz and I receive 38400 points of data that were actually sampled ...
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3answers
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Aquila DSP C++ Library - Wave file FFT analog frequency off by factor of 4?
I'm working with the Aquila C++ DSP library. I'm computing the FFT of a wave file (16 bit depth, single channel, 44100 sample rate). I am using a window size of 16384 to calculate the FFT spectrum.
I'...
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1answer
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Difference in information between IQ Sampling vs. Real Sampling at $2F_s$
As per my current understanding we use IQ sampling as way to increase the useful bandwidth to Fs rather than $F_s/2$ when viewing the FFT because the IQ sampling removes the negative frequencies and ...
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2answers
75 views
Cancelling out known signal with sampling offset
I would like to cancel out a known audio signal at my receiver.
Specifically at my transmitter I am playing a song, and at my receiver I am recording it. Both transmit and receive sampling rate is 44....
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1answer
59 views
Sampling pure tone sine waves [closed]
What would happen if I am using the maximum frequency as the sample rate for sampling a pure tone sine wave?
For example, a $10\ \rm kHz$ sampling frequency for a $10\ \rm kHz$ monotone sine wave. ...
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1answer
86 views
How to describe correlated noise after the signal is oversampled?
The Gaussian noise in discrete signal models is usually assumed to be independent and identically distributed variables (i.i.d.). Does this mean that the signal must be sampled with the sampling rate ...
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1answer
180 views
about sampling frequency
I am trying to make a DFT on a signal with frequency f=50 MHz main component plus some noise.
As far as I know if I sample it at F=100MHz I should be able to get a proper plot of the DFT since F=2f ...
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1answer
84 views
Reconstruction of sampled band-pass signal
I am pretty new to signal processing. I am currently trying to reconstruct a sampled band-pass signal created with the filtfilt and ...
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1answer
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How to convert ofdm symbol to signal?
Hello may I know how to convert ofdm symbol generated from ifft block to an OFDM signal for the purpose of transmitting it?
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IQ Sampling and Oversampling Differences? *Confused*
Two different thought process that produce two different alias band calculations .... What concepts are these?
If I have two 1 GHz ADC's and they sample with 90 degree offset (A comment said this is ...
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Difference between sampling rate and baud rate and their relation to channel capacity
The sampling rate says that one Hz can carry at least 2 samples, and the bit rate is obtained by multiplying the sampling rate by the number of bits per sample. Thus, many samples and many bits can ...
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First order hold from zero order hold filter
I'm stuck in this question for more than 4 hours. (h is the sampling period)
I simplified the block diagram but it just seems impossible to get the FOH transfer function from the reduced block ...
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1answer
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Going from output of D/C to input of D/C
$$y_c[n] {\longrightarrow} \boxed{\text{D/C}} {\longrightarrow} y(t)$$
If the following equation describes the IDEAL D/C converter:
$$y_c(t) = \sum \limits_{n=-\infty}^{\infty} y_d[n]~ \text{sinc}\...
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1answer
39 views
IDFT - influence of sample numbers
I'm quite a newbie in dsp domain, and there's something I can't understand clearly.
I'm doing a IFDT of a spectrum regularly spaced with complex values : the spectrum is a complex conjugate symetric ...
