Skip to main content

Questions tagged [sampling]

In signal processing, sampling is the reduction of a continuous-domain signal to a discrete-domain signal.

Filter by
Sorted by
Tagged with
0 votes
1 answer
16 views

Meaning of the phase of a sample

In a sampled signal RF signal with I,Q parts, if we represent each sample as an amplitude and phase, what does the phase of a sample mean? Does it say something about the RF signal at that point of ...
0 votes
4 answers
138 views

Why do the lengths of the sampled signals $x_1, \: x_2$ have to be $\text{length}(x_1)+\text{length}(x_2)-1$?

We know that convolution in time is equivalent to multiplication in frequency (Fourier). $$x_1(t) \ast x_2(t) \leftrightarrow X_1(\omega)X_2(\omega) \tag1$$ However, for a sampled signal, this ...
1 vote
1 answer
37 views

does extension to reals of an arbitrary signal with a zero tail eventually cross a threshold

Suppose I have a sampled signal $S(x) :=\space [ \space ..., X_{-2}, \space X_{-1}, \space 0, \space 0, \space 0, \space 0, \space ... \space ]$ where $\{X\}_{n}$ is bounded by $\pm1$ when n is a ...
0 votes
0 answers
21 views

Sinc droop in a simple sampling mixer

This question is about the conceptual interpretation of a track-and-hold mixing operation implemented conceptually below, where an output $y(t)$ tracks an input $x(t)$ for half of a period $T_{LO}$ ...
2 votes
1 answer
249 views

Can time aliasing cause peaks?

For the following I use the terms “time domain signal” and “frequency domain signal” as a Fourier Transform pair. The question is for generalized cases of continuous-time signals that once sampled in ...
1 vote
1 answer
146 views

Convolve sinc trains

$$ \begin{align} & \mathrm{sinc}(As + .5)\sum_{n=-\infty}^{\infty} \delta (s - n/A)\ \star \\ & \mathrm{sinc}(Bs + .5)\sum_{n=-\infty}^{\infty} \delta (s - n/B) \end{align} $$ How to compute? ...
1 vote
2 answers
754 views

Nyquist Frequency and Window Length

The Nyquist theorem states that the sampling rate must be twice the highest frequency to be observed. How does the length of the interval play into this relationship? The main resource that I found ...
0 votes
0 answers
32 views

Frequency sampling

How does nyquist sampling theorem works. For example, given a signal with rang 0.5 to 1.5 Hz, why does the fs is 2 Hz?
1 vote
2 answers
2k 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. 1000-10,...
0 votes
3 answers
103 views

DAC - Can we create and use frequencies above Fs/2?

I understand how the ADC and Nyquist works. Anything above Fs/2 can be indistinguishable from frequencies inside Fs/2 so we use an alias filter to remove them before sampling. This can also be an ...
2 votes
1 answer
163 views

What is the Expression for Reconstruction After Derivative Sampling?

I've been trying to use Equation (1) in Linden and Abramson to reconstruct a signal using uniformly spaced samples of the signal and its first and second derivatives. The reconstruction seems to work ...
0 votes
0 answers
43 views

Best Approach To Demodulate AM Signal

I have a way of direct sampling negative polarities and positive polarities using an ADC. I store the values separately. When I use Python to FFT, either polarity samples, the returned results can be ...
3 votes
4 answers
216 views

Why is sampling not “idempotent”?

This answer describes succinctly what sampling a continuous signal means in the frequency domain: $$ \begin{align*} x(t)\sum_{n=-\infty}^{\infty}\delta(t-nT) &\leftrightarrow \frac{1}{T}\sum_{k=-\...
1 vote
1 answer
828 views

Why does the bandwidth of a signal need to be half of the sampling rate? [duplicate]

Suppose I perform a DFT on some function with sampling rate of $\frac{1}{\Delta t}$. According to this page, the bandwidth, which is the maximum frequency that can be analyzed when performed the DFT, ...
0 votes
1 answer
32 views

Resampling n timeseries datasets with different sampling frequencies

I am currently working on an IoT project that uses datasets from different sensors with differing sample rates fs = (1s, 30s,...). I combine this with API data <...
1 vote
1 answer
69 views

Multirate systems - downsampling

As my teacher explained the process in class, I wanted to write a MATLAB code for learning purposes that downsamples a signal with a downsampling factor of L. Here's the code I wrote and the output ...
2 votes
6 answers
2k views

Why does twice the sampling rate (Nyquist Theorem) seem inadequate?

I was told in my electronics course that "to reproduce a wave, we need to sample it at least twice every period." If I take this to be literally true, then a sine wave with only 2-3 samples ...
0 votes
0 answers
30 views

Upsampling realtime data for sensor fusion

I am doing a real-time sensor fusion of gps and imu streams using a Kalman filter. Both streams are obtained independently (with geolocation and accl-gyro values) in real time. I am doing this in ...
1 vote
1 answer
89 views

Signal recovery is based on the development of the Shannon sampling theorem?

One of the earliest extensions of this theorem was stated by Shannon himself in his 1949 paper, which says that if $x(t)$ and its first $(M - 1)$ derivatives are available, then uniformly spaced ...
5 votes
3 answers
932 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 ...
0 votes
3 answers
182 views

How to convert an OFDM symbol to a signal?

How can I convert an OFDM symbol generated from an IFFT block to an OFDM signal for the purpose of transmitting it?
4 votes
1 answer
3k views

How Does the RMS of White Noise Change with Sampling Frequency?

There is an analog system which includes the continuous-time linear equalizer (CTLE). With some .noise analysis the power-spectral density (PSD) of the noise in that system is provided. So let's not ...
0 votes
1 answer
118 views

Sampling a pulse train with a controllable square wave

I have an issue regarding a sampling process of a pulse train in an image sensor based on events. Basically, these are a family of image sensors in which each pixel outputs a train of pulses, and the ...
0 votes
1 answer
23 views

Discrete Frequency representation for central frequency/ discretize up-converted signal in time and frequency

I want to analyze a signal after up-conversion in discrete time and frequency, for example: Let's assume a continuous up-converted signal is: $$e^{j2\pi ft} \cdot e^{j2\pi f_c t} = e^{j 2 \pi (f+fc) t}...
0 votes
1 answer
85 views

realistic sampling - where am I wrong?

I’m given a signal $x(t)$, it's convolved with $h(t)$ and sampled at rate T=1. The result is called $\tilde{x}[n]$. For $$h(t) = \begin{cases} 1 & -0.5<t\le 0.5 \\ 0 & \text{else} \end{...
1 vote
1 answer
51 views

frequency selective channel $\ne$ multi-tap channel?

A frequency selective wireless channel is necessarily a multi-tap channel, in the tap-delay line model, as the delay spread is significantly larger than the symbol duration. And a single-tap channel ...
1 vote
2 answers
110 views

Resolution after Oversampling, Filtering-Decimation

The ADC I am working on has a resolution of 24 bits and a Signal-to-Noise and Distortion (SINAD) of 108.4 dB. Assuming only quantization noise is present, the Signal-to-Noise Ratio (SNR) of the ADC ...
3 votes
1 answer
1k views

Why is sampling frequency/rate typically abbreviated Fs and not Sf in English?

This is not a technical question, it is rather a question about the implicit notation used in MATLAB and multiple digital signal processing books to refer to sampling frequency/sampling rate. Why is ...
0 votes
1 answer
71 views

Decoding an analogue signal for a given sampling and signal frequency that aren't in sync

I am trying to decode an analogue signal, that is intended to be converted to a digital one and decoded as USART communication. In the image shown the blue trace is the analogue signal, and the ...
0 votes
1 answer
107 views

Sampling and Demodulation question

if I have an analog modulated signal with a DSBSC modulation (modulation index 100%) as an input in my receiver and I want to convert it to a sampled signal, do I need to demodulate the signal (with ...
1 vote
2 answers
56 views

Sample rate of digital modems--how do they do digital filtering if sampling below Nyquist rate?

I can't find this answer anywhere. I have a couple satellite modem manuals and they refer to digital filtering functions that they do, but they say almost nothing about their sample rate. I always ...
0 votes
1 answer
80 views

Effect of sampling rate and duration on discrete parameters of sine (spectrum)?

The DFT of $$ \cos(2\pi f t + \phi) $$ peaks at $k=\pm f$ if $t = \frac{1}{N}[0, 1, ..., N - 1]$ (for integer $f$, & within Nyquist). What about other $t$? What if we double the sampling rate or ...
1 vote
0 answers
47 views

Discussion on the relationship between the FFT magnitude spectrum and the corresponding actual amplitude

This might be a bit long, but it's a question that has troubled me for a long time, and I hope to get everyone's help. When studying signals and systems, we usually only pay attention to the relative ...
3 votes
2 answers
4k views

I/Q sampling with just one ADC

Usually I/Q sampling is performed on two signals with a 90° phase shift using separate ADCs. Suppose I have only a single (fast) ADC available to perform I/Q sampling, which approaches do exist? Is ...
0 votes
1 answer
32 views

Frequency decomposition of forecast error variance

I think my question concerns statistical signal processing. I was referred to this site by a user at Cross Validated. I want to do a frequency-domain decomposition of generalized forecast error ...
3 votes
1 answer
95 views

How to understand "independent sample rate" of windows?

A window metric called independent sample rate is given in a book that I recently read. It says that in spectral estimation, the variance of power-level estimates is inversely proportional to the ...
4 votes
1 answer
72 views

What are some good questions for a graduate level signal processing course?

I am currently taking an graduate-level Advanced Signal Processing class and I have a midterm soon. However, the midterm is not only open-book but it is also open-internet and untimed. Now I have no ...
3 votes
1 answer
97 views

Does oversampling lead to colored noise?

Suppose we receive $R(t)=X(t)+W(t)$, where $X(t)$ is band-limited to $[-B/2, B/2]$ and $W(t)$ is white Gaussian noise with autocorrelation $R_W(\tau)=\frac{N_0}2\delta(\tau)$. If we filter $R(t)$ ...
0 votes
1 answer
32 views

Is there a test/statistic for the reliability of my data given my sampling?

I'm in a situation where I'm sampling blood pressure data over time (unequal sampling) to capture potential peaks. On average, the frequency of circadian blood pressure would be 1. But in reality, ...
1 vote
1 answer
52 views

Anomaly in Magnitude Spectrum plot of an ASK Signal

Following is a SciLab code and Plots for Modulation of ASK Signal: My question is : For these particular values of fm and t, I get two weird small spikes on either side of main lobe, which doesn't ...
1 vote
2 answers
120 views

DFT Matrix Oversampled In Frequency?

Edit 2: I am trying to replicate results from this paper Compressed Sensing with Coherent and Redundant Dictionaries. On page 3 the "oversampled DFT" is mentioned as an example of an "...
5 votes
2 answers
4k views

Does audio upsampling create noise/artifacts or degrade the signal?

I've read that upsampling performed in digital music playback can color the sound, produce artifacts, etc. For example, an audio file ripped from a CD might be 44.1Khz/16-bit, and then upconverted to ...
2 votes
2 answers
146 views

insights into making AR Burg extrapolate finite periodic signals

Following a past question, I'd like to extrapolate a periodic signal using AR Burg, but when doing so, it seems that I need to sample "enough" for that to work. For example, if I use the ...
3 votes
2 answers
348 views

Why is sampling a signal equivalent with multiplying with a Dirac comb?

Given a continuous time signal $f(t)$, we can sample it signal by multiplying with a Dirac comb (impulse train) $$\bar{f}(t) = \sum_{n=-\infty}^{\infty} f(nT) \delta(t-nT) \tag{1}$$ where each impulse ...
0 votes
1 answer
61 views

DAC/ADC sample rate selection for modem

So I have a very basic on which I couldn't find much details anywhere. I'll start with an example: I have to transmit 100Mbps of BPSK data. Roll-off factor is 0.25. This data will be processed at ...
1 vote
1 answer
88 views

Steering Vectors and Bluetooth Low Energy for computing Angle of Arrival

I am new to signal processing, but I have background in mathematics. I am trying to use Bluetooth Low Energy (BLE) on three mobile devices, where one device is being tracked and the other two act as ...
2 votes
1 answer
261 views

How to Extrapolate a 1D Chirped Signal?

Following a past question, I'd like to extrapolate a signal like the one below: (red is signal, blue is the the extrapolated ) ...
0 votes
1 answer
61 views

ADC output rate, undersampling and decimation

I have an ADC working with a sample rate of 960 Msps, my signal being located at the 3rd Nyquist region (I am undersampling). Input signal bandwidth is centered at 1200 MHz with a bandwidth of 120 MHz....
1 vote
1 answer
227 views

How does aliasing affect bits in an ADC?

I want to measure a signal whose frequency spectrum is infinite, but I am particularly interested in the frequency range $ 0 - 500 \ \text{Hz}$. I have a 12-bit ADC. The ADC has dynamic range $ 6 \ \...
8 votes
3 answers
16k views

What should be the correct scaling for PSD calculation using $\tt fft$

I would to calculate the PSD of a signal using FFT however the result do not match with periodogram command. What did was as follow : ...

1
2 3 4 5
23