# Questions tagged [interpolation]

Interpolation is a method of constructing new data points within the range of a discrete set of known data points.

274 questions
Filter by
Sorted by
Tagged with
412 views

### DTFT reconstruction

I have a sampled DTFT. If we assume that there isn't aliasing in time domain, what is the best way to reconstruct DTFT from its equidistant samples? I though about Dirichlet interpolation. Do you know ...
101 views

### Regressing/interpolating between quasi-periodic sinusoids

This is a cross-post (on recommendation) from CV. My problem is very simple. I currently intend on using Kriging (Gaussian process regression) to perform regression between the trajectories marked ...
4k views

### Can you decimate / downsample a signal in frequency domain just like you can interpolate / upsample it?

To interpolate a signal I can just zero pad it in the frequency domain. If I want to decimate the signal, can I just discard some part of the frequency domain? So in MATLAB this works: ...
2k views

### Algorithm for 1d spline interpolation suitable for 8 bit microcontroler

What is a concise, fast, down to earth algorithm for doing (or closely approximating) spline interpolation on a 1d continuous stream of data? (Edit1: The paragraph below equates to saying "the ...
994 views

### Designing a half band FIR filter with Scilab

I'm trying to design a half band interpolation filter using Scilab's eqfir function, which uses Remez's algorithm internally: ...
990 views

### Why many DACs uses series of half band filters for interpolation instead of single one?

And why, according to some sources, these filters have different number of taps (the last is the shortest one)? Does it really reduce a cost of computation?
167 views

### White noise gain of uniform spline interpolation

Uniform spline interpolation is fully defined by its continuous-domain impulse response. I noticed that the integral of the square of the impulse response over its support gives the average ...
429 views

### How do I design a speed-efficient high-pass filter to replace slow polynomial filter? [closed]

I have the recorded membrane potential of a neuron, and I want to get a more even baseline by removing certain slow changes from the signal (see figure). The best way to achieve this thus far has been ...
2k views

### Interpolation of magnitude of discrete Fourier transform (DFT)

For example for peak frequency finding, it seems valid to use band-limited interpolation methods on the complex DFT bins, or separately on their real and imaginary parts and to calculate the ...
641 views

I have trouble accepting the merits of zero padding in the frequency domain to give more points in FFT. Wonder if anyone else has similar thoughts. The mathematical 'proof'for the validity of zero ...
2k views

### Resampling an audio signal

I am trying to resample an audio signal in my application. It will be between 48kHz and 96kHz audio (both upsampling and downsampling). Looking at the Wikipedia page for resampling I see there are ...
2k views

### DFT Frequency domain analysis and interpolation

I have a 2 part question, one may be related to why I'm not understanding the other. A while back, I remember some professor saying that for the $N$ point DFT frequency domain, the values for $k$ ...
541 views

### Signal values we will 'miss' between sampling instances during sampling of band limited signals

According to the Nyquist–Shannon sampling theorem, any continuous time signal with a bandwidth $B$ smaller than Nyquist frequency $f_N=f_s/2$ (with $f_s$ the sampling frequency), which is sampled at ...
571 views

### Interpolate DFT Coefficient of a Frequency That Is Not in the DFT Bin

I'm using the Jacobsen interpolation to get a more precise frequency of my signal. To get the corresponding DFT coefficient I'm doing: $$X_{f} = \sum_{n=0}^{N}{x_{n} e^{-2\pi ifn}}$$ Where $x_{n}$ ...
3k views

### Upsampling/Interpolation and Downsampling/Decimation

I am having trouble figuring out exactly what is happening the process of downsampling/upsampling and the output in the example given below: So the 100Hz sine wave is sampled at 2000Hz resulting in a ...
261 views

### Philosophy of perfect inter-sample interpolation

How would you define perfect (inter-sample) interpolation, and is it possible? To quote Armifinn's prior answer: "I guess the most important result is that for signals with bandwidth limitation, ...
1k views

### Mathematical justification for zero padding?

This question asks what's the point of zero padding. The accepted answer is certainly very insightful, but I don't understand a big chunk of it: Zero padding allows one to use a longer FFT, which ...
2k views

### Whittaker-Shannon ($\mathrm{sinc}$) interpolation for a finite number of samples

Given an infinite number of samples $(N)$, a higher (or lower) number of samples $(cN)$ can be derived using sinc interpolation followed by sampling. How can this be applied to finite length signals? ...
166 views

### Accurate Image Resizing

I need to resize an image using bilinear interpolation and create an image pyramid. I will detect corners at the different levels of the pyramid and scale the pixel co-ordinates so that they are ...
292 views

### Why does Fourier zero-fill interpolation pad the middle frequencies?

In this: http://dspguru.com/dsp/howtos/how-to-interpolate-in-time-domain-by-zero-padding-in-frequency-domain the author says that we can interpolate a signal by zero-padding the middle frequencies in ...
233 views

### Inter-point interpolation using FIR filter

Suppose I have discrete noisy signal $X = (0.096, -0.0632, 0.351, 0.531, 0.360, 0.006, -0.320)$ sampled at discrete time points $T = (1, 2, 3, 4, 5, 6, 7)$. Filtering (zero-padded) $X$ with ...
200 views

2k views

### Sampling Theorem illustration

Can someone please explain the illustration (figure 1.19) at the bottom of this image? It looks like there are four sampling points but I don't understand what the different curves represent. Actually ...
417 views

### Chosing polyphase interpolation coefficients

I'm writing code for a 3x polyphase interpolator using a total of 9 coefficients. This is organized as 3 parallel FIR branches with 3-taps each that are summed at the 3x sampling rate. The problem I ...
30 views

### How to reduce polynomial?

I have some 4 polynomials like this. these equation is made by polyfit() from MATLAB tool. ...
151 views

### Unexpected Result When Using Sinc Interpolation

blue is how I tried to sinc interpolate. why would something like this happen?
1k views

### Sinc Interpolation Using DFT (FFT)

Lets say I want to double the number of points in an array f. I had the idea to do this: F=fft(f);N=length(f); FF=[F(1:N/2) zeros(1,N) F(N/2+1:N)]; f=ifft(FF); ...
68 views

### What is the Concept of MATLAB Function Polynomial Interpolation?

I am curious about MATLAB function. Can you tell me why does not it do good approach to using of MATLAB function except for speed reason? Is there any other reason to using polynomial utility?