# Questions tagged [sampling]

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

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165 views

### Stochastic process inference from partial observations

Consider a set $U$. My signal is a piece-wise constant "function" $Sig: t \mapsto s$, i.e. the signal at time $t$ equals to some subset $s \subset U$. One can see $Sig(t)$ as a stochastic process. ...
69 views

### Minimum time delay that can be estimated between two sensors

Consider a 1-dimensional toy problem. I have two sensors at different points along the $x$-axis. Somewhere away from the sensors, a disturbance is created which travels towards the sensors, first ...
817 views

### Sinc interpolation formula for signal reconstruction in frequency domain from bipolar samples

As per the title, I was wondering if there was a $\operatorname{sinc}$ based interoplation formula for reconstructing a signal in the frequency domain which has been sampled with respect the bipolar ...
500 views

### Interpolating on the borders of differently-resolved images

I'm creating a three-dimensional model of the earth based on SRTM height data. The data set is pretty huge, so only a small fraction of the data is available at any given time. The height data is ...
161 views

### understanding discrete wavelets

I was reading section 4.3.3 from chapter 4 of "A Wavelet Tour of Signal Processing", "...Let $\bar{f}(t)$ be a continuous time signal defined over $[0,1]$. Let $f[n]$ be the discrete signal obtained ...
45 views

### FFT of white noise with different sampling rate

I have a question on how I should interpret the white noise power level (noise floor) obtain from FFT for different hardware sampling rates. I realized if I sample the same noise at different rates (...
56 views

### Problem with 1st order PLL update equation

The output of a communication channel is given by: $x(t) = \sum_n{a_n}h(t-nT)$, where $\{a_n\}$ are BPSK symbols, $h(t)$ is the channel response, and $T$ is the symbol period. If there is an ...
85 views

### Intuitively, why is the comb function the sampling function?

The comb function can be used to sample a continuous signal. The comb function is defined as follows $$C_T(t) = \sum_{k=-\infty}^{\infty} \delta(t - kT)$$ where $\delta$ is the Dirac function, ...
114 views

### How do I 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 ) ...
54 views

### How can I extract the 2 polyphase components of a signal after sampling at the half of sampling rate

Suppose I have a continuous signal x(t), which was sampled using sampling function s(t) whose sampling rate is Ts.How can I sample the continuous signal by Ts/2 instead of Ts in order to get two ...
218 views

### Noise PSD and sampling rate relation

Let's consider generating samples of a random process like white Gaussian noise (AWGN). Let's assume I am generating $N$ samples of AWGN with variance $\sigma ^2$ in MATLAB by using randn() funtion i....
46 views

### Hardware selection for acquiring signal in digital form

I want to it clear that I am a mechanical engineer and so my knowledge on electronics and signal processing is limited. I am working in a hydrophone system. My job is to find the position of an ...
1k 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. I'...
81 views

### Why does filtering the same discrete dataset while choosing different sampling rates yield different results?

If I have a two-dimensional discrete dataset (one space, one time), and I create subsets of this dataset by "sampling" (although the original dataset isn't continuous) it at different rates, should I ...
654 views

### Fast DSP with in-chip ADCs

I'm looking for a DSP, around 500MHz, with an in-chip ADC (preferably 2 but 1 will suffice) that samples around 20MSPS. Does any such DSP exist or do I have to use external ADCs?
132 views

### Upsampling Methods for Computed-Tomography

I have two sets of data of given Field of view, one of them only covers a subset of the FOV of the other. I therefore want to upsample the one with the larger FOV to combine it with the other one. So ...
127 views

### Instantaneous Frequency variation

I am looking for a method to calculate the instantaneous pitch variation within a speech signal for time-warping application. Sample by sample frequency variation knowledge within a frame will give ...
115 views

### Voice sample prediction scheme

I have some telephone voice audio with occasional "blips" in the audio. The blips appear to come from an IP link buried in the PSTN (this is a conceptual explanation, so don't worry about things like ...
39 views

### Lagrange Vs Sinc interpolation

I was wondering what is the practical difference between Lagrange Interpolation using Farrow Structure and Sinc Interpolation? Both require pre-computation of time offset coefficients using a lookup ...
44 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 ...
25 views

### Find integral of DTFT after sampling (Graph of CTFT given)

So for the first question: If this is sampled at 10kHz, then the amplitude is scaled by 10000. In the DTFT, the frequency 3.5kHz gets mapped to 3.5/10* 2pi=0.7pi. So this point lies outside the range ...
39 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 ...
25 views

### Continuous-time RNN and Shannon sampling theorem

The most-used discrete-time RNN equations used in Deep Learning these days are those of Elman: I have seen two very different continuous-time version of these, with different justifications. The most ...
91 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 ...
74 views

### Why is my resampled signal cutoff when resampling with a windowed FIR filter in MATLAB?

I have an exercise to write a function which upsamples or downsamples a signal by a factor of F (integer) using a FIR filter windowed with a Kaiser window function. Exercise I had last week included ...
146 views

### How to obtain the steady state response of the sampled periodic signal data?

Below the green plot Vin is 5Hz sine voltage signal from a function generator output sampled at 12kHz sampling rate: The blue plot Vout is the processed/filtered data by using the following code in ...
71 views

### Proving Nyquist Sampling theorem for strictly bandlimited signals

I understand that the Nyquist sampling theorem dictates that the minimum sampling frequency, $f_s$, be s.t. $f_s > 2B$, where $B$, is the bandwidth of the signal. I have read the explanation for ...
85 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 "...
259 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 ...
116 views

### How to sample a transfer function (angular spectrum) in the frequency domain?

I am having this problem in Fourier optics, where I am using the Angular spectrum method (a lti filter) to calculate the electric field at the required plane given ...
111 views

### Matching two signals with small time drift

I have two time-domain signals sampled at 100 Hz that were measured using two different oscillators and therefore have a time drift between them. I have two synchronization points, one at the start ...
129 views

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 ...
118 views

### dsPIC33E ADC to FFT help

I am sampling an audio range signal with a bandwidth of 3100Hz and then applying a FFT using the DSP library example from Microchip to determine the most dominant frequency of the signal. On the last ...
17 views

### artifact identification in irregular-samped data

There is a dataset combined by different datasets a,b,c,d,e. The time intervals are irregular(i1, i2, i3:intervals between a and b, b and c...), but the sampling rate SR in every single dataset is the ...
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### What kind of signal reppresents this Power Spectral Density?

I'm sampling 8 bioelectric signals with a embedded board which use an 8-channels ADC (AD7175-8). My sampling rate for every single channel is about 6250 Hz. When move the analysis in the frequency ...
218 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 ...
2k 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 ...
32 views

### Signal view from two different receivers (of the same model)

I have two SDRs hooked up to two different computers, both radios tuned to the same frequency. They sample at 2Msps. What I would like to do is start up both (at 'about the same time'), and, after ...
82 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 ...
134 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 ...
195 views

### What is advantage of Logarithmic Sampling?

Logarithmic Fourier Transformation This paper starts off in the abstract saying that the given audio signal is sampled logarithmically. We also know that the human ear has a sort of a filter bank ...
103 views

### Can picking an inappropriate roll-off frequency for a digital filter just alias the roll-off value?

I believe a related question is asked here, but my question deals more with what filter is realized if one fails to consider design parameters relative to sampling rate. In designing an IIR filter we ...
39 views

### Number of trials to judge performance of Compressive Sensing recovery algorithms

I'm trying to get a conclusive numerical value for Mean Squared Error (MSE) as the performance metric of a few CS sparse recovery algorithms. To do this, I vary the number of measurements ($M$) taken ...
125 views

### DAC output SFDR and Harmonics does not meet at particular decimal frequencies

We are using a current output DAC to perform waveform generation in the band of $20\textrm{ MHz}$ to $500\textrm{ MHz}$ and sampling at $1.2\textrm{ GHz}$. SFDR and harmonics suppression requirement ...
45 views

### DWT initialization from nonuniform samples

Let $D\subset\mathbb R$ be compact, let $f:\mathbb R\to\mathbb R$ be a contintinuous function with support $D$. Let $\phi(x)$ be a well-defined scaling function, in the sense that it generates a ...
8k 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 ...
427 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 ...
210 views

### 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 ...
My instrument performs measurements at non-equal time intervals, i.e. non-uniform sampling. Apart from this, I usually oversample (by a factor of $n$) for reasons related to filter design, and ...