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

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Improve $\rm dB$ level after upsampling audio

I am doing upsampling from $44.1\textrm{ kHz}$ to $48\textrm{ kHz}$ on android device, using $\rm sinc$ interpolation. The output $\rm dB$ level is upto the mark for wave file up to $15\textrm{ ...
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20 views

Gaussian Pyramid - How is Subsampling Rate Related to Sigma?

I found a gaussian pyramid implementation in a MOPS paper (feature detection). They use sampling rate $s=2$ and $\sigma=1$ - i.e. to generate a new level of the pyramid, the current level is smoothed ...
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36 views

Upsampling and zero order hold

Maybe to someone this question may seem quite easy but I have a problem grasping it. Namely, assume that we have two systems A and B with sampling rates $f_A$ and $f_B$ where $f_A>f_B$ and ...
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36 views

Digital Filters deal only with samples, right?

I'm new to digital filters. So I'm trying to get things right and I can't find an explicit answer to my question on the internet. Question: Digital filters only accept samples as input? I mean the ...
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1answer
35 views

MATLAB and sampling rate

I have a question about sammpling rate in MATLAB. I read a .wav file using audioread(). It give me sampled data called ...
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2answers
47 views

Aliasing Square Wave

I'm having a really weird issue with generating waveforms from frequencies C1 to C8. When I generate sine waves, everything sounds good; no problems whatsoever. However, when I generate a square ...
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1answer
32 views

OFDM demodulation, how to set the sampling rate?

I have a signal for which I know the OFDM burst length (from the autocorrelation function of the signal) T_burst and the FFT size 1024 (by measuring the channel ...
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2answers
32 views

Sampling rate vs sampling time of FFT

I am having some trouble understanding the sampling time and frequency used in the computing of the FFT, and I was wondering if someone could make it clear for me : The Sampling time: the time in ...
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1answer
49 views

Envelop detection with low sample rate?

I have a signal up to $3\textrm{ MHz}$. The ADC that sample it has a rate of $1.5\mu s$. So a full $T$ of the signal is $0.3\mu s$, and I can only sample each $1.5\mu s$. It sounds not enough, but I ...
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36 views

Flat top sampling to a step shape signal

Flat Top Sampling During transmission, noise is introduced at top of the transmission pulse which can be easily removed if the pulse is in the form of flat top. Here, the top of the samples are flat ...
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36 views

Should the order of a filter be proportional to the sampling rate?

I have designed a fir filter with my desired frequency response at a specific sampling rate and filter order. If I were to redesign my filter for a new higher sampling rate, should I change the filter ...
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42 views

Output a sine wave from samples-limits?

Using a micro-processor of 48MHz, I am trying to output a sine wave from the DAC (digital to analog ), and I am not sure if my ...
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2answers
42 views

Generating very short signals

So I need to program (using Java) some things that include generated sounds. I am struggling to understand how to make it work because I require a rather short signal while still using a sampling rate ...
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2answers
35 views

Sampling frequency of audio

Based on what we choose sampling frequency when sampling some song? Do we use Nyquist–Shannon sampling theorem, or maximum sampling frequencies are pre-defined, so it will never come to aliasing ...
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47 views

Sampling a sinusoidal signal

Consider the signal $g(t) = \cos(2\pi\lambda t + \phi)$ that is sampled with a frequency $\tau$. Let $g_k$ denote the values of $g$ at the times $t_k =\frac{k}{\tau}$, $k \in \mathbb{N}$. (a) Show ...
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1answer
71 views

Random sampling vs uniform sampling

In this paper of Lustig, he speaks about a something which appears unintuitive: sampling at random may exhibit better performance than sampling uniformly. I tried to understand this starting from page ...
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23 views

Simple sample and reconstruction code - MATLAB

I am trying to go from theory to code. I take x (let say 16KHz is continuous time) then I sample it in 2Khz So I do ...
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1answer
20 views

EEG signal processing with sampling frequency

What is the relation between sampling frequency and the frequency of the signal after sampling? For example sampling frequency is 100 Hz, that is the signal contain maximum frequency of 50 Hz. Then ...
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1answer
29 views

how to sample and modulate a gps gold code

I am trying to simulate the data transmission of a GPS satellite. Telecommunications is not my field so I am struggling a bit with some concepts. I managed to generate the Gold code of the GPS ...
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2answers
54 views

Sampling Rate and SNR

Assume I have a signal that oscillates between 10KHz and 9Khz every 500msec (Change happens linearly, so at t=0, it is 10KHz and it goes to 9.5Kz at t=250msec and 9KHz at t=500msec and frequency start ...
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49 views

How to do the highest resolution FFT?

I wish to do the FFT of streaming audio data coming into a computer. I am just interested in frequencies from 80 Hz up to 1000 Hz but with a frequency resolution of 3 to 4 Hz and no more. Basically ...
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58 views

Why is $e^{i2\pi Nf_snT}=1$?

Why is $e^{i2\pi Nf_snT}=1$ in snippet from book?
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3answers
64 views

Performing DFT of streaming audio problem. Is there a limit?

I am trying to write software that will perform the discrete fourier transform of real time data coming from the microphone into the sound card on a computer. I am using Java with the javax.sound ...
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2answers
63 views

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. ...
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3answers
70 views

What is the underlying concept behind Bandpass sampling?

Can you suggest me some books/webpages on Bandpass sampling? I undestand that if the signal is restricted between $f_L$ and $f_H$, then the minimum bandwidth required is $2(f_H - f_L)$. But say the ...
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44 views

Closed-form expression for Whittaker-Shannon interpolation for non-bandlimited signals

For a bandlimited signal $x(t)$ that is reconstructed after Nyquist-sampling at intervals $T$, $$x(t) = \sum_{k=-\infty}^{\infty} {x[k]\textrm{sinc}\left(\frac{t-kT}{T}\right)}$$ where $x[k]$ = ...
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32 views

How do we actually obtain samples to form discrete time samples? [closed]

I'm in my second week of an online DSP class and I'm still kinda lost on some of the concepts of what we are actually doing. I'm hoping you guys can help clear up my understanding. Please forgive me ...
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29 views

Approximation of Step Response from Data with delay

How can I approximate a Step Response curve from a measured data of a single input and a single output using Matlab while the delay between the input and the output is 30 minutes?
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1answer
75 views

Calculating a signals frequency when given the number of samples

This place has been great in helping me to understand my online image and signals class! I've moved on to another question and wanted to see if I'm correctly grasping the subject. The next question ...
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2answers
44 views

Capturing the sampling rate from a basketball being dribbled

I'm taking an online image and signals class and the structure is absolutely horrible. I'm wondering if you can provide me hints, or tips to solving the below question. I'm not looking for an ...
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17 views

Reduction of Sample Size of a Gaussian Pulse

I need to sample a gaussian wave of pulse width of 1 us which is being modulated by a cosine wave of GHz frequency. The different cases that I am interested in are 1) The initial phase of the cosine ...
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120 views

Zero, First, Second … nth-order Hold

The rectangular function is defined as: $$\mathrm{rect}(t) = \begin{cases} 0 & \mbox{if } |t| > \frac{1}{2} \\ \frac{1}{2} & \mbox{if } |t| = \frac{1}{2} \\ 1 & \mbox{if } |t| < ...
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116 views

Relation between the DTFT and the spectrum of a sampled signal

In the $\rm DTFT$ (Discrete Time Fourier Transform) the spectrum is periodic with period of $2\pi$ . A continuous signal when sampled has a spectrum which is a repeated version of its original ...
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58 views

Sampling and zero crossing

I am sampling a sine wave of 50Hz(stepped down from 230V) at the rate of 500KHz. For identifying disturbances in the wave, i was thinking of comparing a cycle of incoming sine values with reference ...
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45 views

Zero-order-hold for two dimensional signal $x(t_1,t_2)$

From Wikipedia: A zero-order hold reconstructs the following continuous-time waveform from a sample sequence $x[n]$, assuming one sample per time interval $T$: $$x_{\mathrm{ZOH}}(t)\,= ...
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55 views

Number of samples needed to convert a analog->digital, frequency bound, signal with decent quality to the Fourier domain

Similiar question(s) have been asked before, but I didn't fully get the answer I was looking for, so I figured I'd ask again. My excuses if there's something really basic in signal processing I've ...
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2answers
30 views

What are the implications of resampling the derivative of a signal with a higher frequency than the original signal?

Suppose I have a digital signal measured with sampling time, $T_s=1$ sec. If I take it's derivative, it will, naturally have $T_s=1$ sec. But what are the implications if I re-sample this derivative ...
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49 views

How can I duplicate this type of image?

I'm very new to the idea of signal processing, could someone point me in the direction of of a program to toy with images, below is a link to 2 taken a split second apart that showed up on my Amazon ...
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34 views

IDFT of H(z) sampled in N values

If a have a causal IIR filter described by $H(z)$ and I sample it in $N$ equispaced values around the unit circle, I get a DFT of $N$ points. That DFT corresponds to $h[n]$ truncated in $n=N-1$ or to ...
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53 views

Zero-order interpolation problem

Let $x_c(t)=\cos(\omega_0t)$. This signal is sampled with $\omega_s$, which is greater than the Nyquist rate. It is then interpolated with a zero-order interpolator. The signal obtained is ...
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172 views

Sampling Theorem: How to know the value between two samples of a Signal

According to Sampling theorem, in order to reconstruct a signal we need to sample it at the rate => twice the highest frequency component of that signal. (provided signal is band limited). Let's say, ...
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Why is it better to sample white noise in frequency domain here?

We have a channel $c(t)$ that we want to sample. It can be expressed as $ c(t)= g\ast x(t)$ where $x(t)$ is white complex Gaussian noise and $g(t)$ is a function that we know the PSD of, let's call it ...
3
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1answer
79 views

Downsampling and Then Upsampling

Given this system: I need to show the $\mathcal Z$-transform of $y[n]$ as a function of the $\mathcal Z$-transform of $x[n]$. Now I know that for downsampling alone: $$Y(z) = ...
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1answer
25 views

A reference request for zero-order hold (ZOH)

From Wikipedia: A zero-order hold reconstructs the following continuous-time waveform from a sample sequence $x[n]$, assuming one sample per time interval $T$: $$x_{\mathrm{ZOH}}(t)\,= ...
2
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2answers
55 views

Sampling H(z) to get DFT

Suppose that I have a $H(z)$ and I sample it to get a DFT of 15 values. Let's call this DFT $H_{1}[k]$. Then, suppose I antitransform $H(z)$ and grab the first 10 values of the sequence, and then I ...
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3answers
51 views

Does the hold part in sample and hold turns the signal from discrete to continuous?

I am trying to link sample and hold to discrete and continuous time domain. Could someone please confirm: When sampling but not holding for "an extended" period of time, you have discrete samples. ...
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27 views

How to calculate output from non-uniformly sampled transfer function data?

I have non-uniformly sampled transfer function data (magnitude only) in the range of 100kHz and 200MHz. Using this transfer function, I would like to calculate output from specific input. Question : ...
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71 views

Sampling frequency lower than half of sampled signal frequency?

In GNURADIO when RTL-SDR Source block is placed there is a parameter Sample Rate (sps) and ...
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20 views

Sampling a Signal with maximum frequency content of 600Hz

I am looking to sample a signal with a maximum frequency content of 600Hz. From Nyquist, 2x fmax= 1200Hz, therefore would a sampling frequency of 2kHz be suitable?
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95 views

fmcw radar sampling requirements

I have been reading about "all-digital" or "software-defined radars". Lately, I was trying to simulate an FMCW short range radar in Matlab. One thing that struck me during the simulation is that to ...