# Questions tagged [interpolation]

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

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### Transmitting data with QPSK using an SDR

My question assumes that I want to transmit some data using QPSK using and SDR. The SDR will be fed with IQ data and this will transmitted at a sample rate Fs and be up converted to a carrier ...
1 vote
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### LTE PSS Channel Estimation for coarse SSS Equalization

In LTE the Primary Synchronisation Signal (PSS) can be detected by taking a correlation with the known 3 zadoff chu sequences (roots: 25,29,34). Once the peak has been detected the receiver knows ...
117 views

### Estimating spectrum with regularly missing samples from data

Suppose: $$s(t) = \sin(2\pi{f_0}t)$$ Suppose I'm sampling the signal with a sample frequency $f_s >2f_0$ . However, every $M$ samples there is a dead-time of $L$ samples. Traditionally, the (...
1 vote
88 views

### On FFT, interpolating signal vs extending signal in time

When we interpolate, then FFT the output will have more bins. When we extend the signal in time, Then FFT output will have more bins too but: Interpolation increases max bin frequency but time ...
1 vote
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### Frequency spectrum of interpolated sine

When interpolating a sine wave in Python, it seems I get a lot of additional frequencies closely around the fundamental. Why is that the case? I would have expected a more or less similar spectrum, ...
114 views

### what degree of accuracy does quadratic interpolation add to fft cross-correlation?

I am not a dsp engineer, so I might be missing some obvious background, but I've been doing my best to educate myself. Let me know if there's more info needed. I am using an fft cross-correlation ...
74 views

### Real time variable speed audio playback with interpolation

I'm trying to correctly implement the real-time variable speed playback of my buffer, to achieve the pitch shifting. I don't need to stretch to preserve the original length. Buffer is calculated with ...
55 views

### How can I use interpolation to align audio [duplicate]

I notice that when I connect two audio clips, there is a jump at the junction. How do I use interpolation to connect these two pieces of audio? Thanks for the answers, I've got an answer from my ...
1 vote
105 views

### Averaging a Signal with a delayed version of itself

I am working on a problem that requires interpolating between two music files. One music file is very similar to a delayed version of the other. I would like the 'average' of the two signals to sound ...
80 views

### Sample rate change using Lagrange interpolator

I'm trying to understand how to make Sample rate change by a non integer factor say $K=1.0012$ In real hardware I will be using cubic polynomial but for now I have chosen a linear interpolator. I have ...
1 vote
42 views

### Correct OFDM oversampling method

I need to oversample my OFDM signal, however I have issues understanding which OFDM oversampling method is the recommended one. First method : Before taking the IFFT, the OFDM subcarriers are padded ...
1 vote
41 views

### DSP library for Software Defined Radio

Can anyone recommend a good C library for SDR? To be more specific I just need a function in C to compute coefficients for CIC compensation filter (I need to do it in real time, so Matlab is not an ...
74 views

### How can the DCT be used for bandlimited interpolation?

I know the discrete cosine transform (DCT) is used for compression, but can anyone give an example of how to use it for bandlimited interpolation? One way might be zero-padding in the DCT domain and ...
830 views

### Why does interpolation with zeros introduce frequency artifacts?

Consider the original signal (just a sine) and the same signal interpolated with zeros: The Fourier transform of them: In this example I inserted only one zero between the samples, as if I sampled ...
87 views

### Upsampled signal values

My question is: after upsampling a signal, does the output signal contain the original signal values? The diagrams I saw so far (on wikipedia and different forums) have always shown the original ...
80 views

### Resampling in time

I have a huge dataset, way too much to be loaded into memory. I need to downsample the data to a new rate. Normally, this would consist of upsampling by N, applying FIR LPF, then decimating by M to ...
1 vote
76 views

### Multiple questions about how to implement practical resampling

I am learning resampling theory, and for the time being I am specifically interested in downsampling. I have a textbook that is not a dsp textbook but has a section on resampling. The way they put it, ...
1 vote
59 views

### How should I interpolate on a triangle mesh?

I have a triangular mesh (generated from a Lidar point cloud). On this mesh I do point measurements using two instruments. One records M amplitudes of frequencies in the visible range and the other ...
74 views

### Does the combined pointsample+bilinear upscaling algorithm have a name?

I have been performing digital image upscaling of pixel art in one of my hobby projects, and the two simplest upscaling algorithms are point sampling or bilinear upscaling. Point sampling exhibits ...
149 views

### Are there ways to reduce the smearing of zero-padding interpolated data?

Are there ways to reduce the smearing / spectral leakage of zero-padding interpolated data? I learned that, given a small collection of samples, one can increase the frequency resolution of an FFT ...
1 vote
140 views

### Reconstructing an undersampled signal by cutting off at the signal's maximum frequency

Assume a (continuous) band-limited signal $f$, that is, a signal for which $F(s) = 0$ for all $\lvert s \rvert > p / 2$. If the signal is sampled with frequency $p$, we can reconstruct it by ...
1 vote
118 views

### Accurate frequency estimation with closely-spaced tones

I have a MIPs-limited DSP platform where I am taking an FFT of a streaming audio signal at regular intervals. I need to find the top 4 amplitude peaks and their corresponding frequency for every frame....
102 views

### Extract diagonal area from image

I have a gray scale image of fibres in different orientations. My goal is to mark the area where the fibres have a specific angle and neglect the rest. In the future it should be an automated process ...
1 vote
136 views

### Spline interpolation of a binary mask

I have the following binary mask (If it helps you can assume that every it is always 1px wide). I want to travel from one given point to another (from start to end in this case). You are given the ...
1 vote
645 views

### Zero padding versus zero stuffing

Let's say I want to increase the sampling rate of my signal, $f_t$, from a sampling frequency $f_s$ to some multiple $Mf_s$. One way to do this is to add zeros between the samples of $f_t$. This ...
1 vote
348 views

### Interpolation to create equally spaced value using Python

I am working on a project in which I am required to use Interpolation to create equally spaced position values as the position samples are not equally spaced due to varying train speed. So, the total ...
284 views

### Applying Kaiser Window to sinc interpolation

I am trying to apply the kaiser window during sinc interpolation. The following is my sinc interpolation code: ...
142 views

### 16 point Sinc Interpolation Kernel

I have a signal that is sampled at Fs and wish to apply a "16-point Sinc interpolation kernel". However, I am not sure what the 16-point refers to. Does it refer to having a kernel that is ...
1 vote
194 views

### Multirate Control System Transfer Functions

I'm interested in oversampling the inputs to a digital controller to increase the SNR of the input process variable signal. I've read on this site and in articles like the one below that it is not ...
1 vote
320 views

### How to interpolate the peak amplitude of an fft output?

I want to find the peak amplitude of an audio signal in a given frequency area. My problem is that if the signal has a strong resonating frequency between 2 fft bins, then both bins are way below the ...
766 views

### Odd artifacts after sinc interpolation

I am trying to upsample a signal using sinc interpolation. I have written a way to do this in python. ...
1 vote
73 views

### Guided bilinear interpolation: is it a known algorithm?

I have a function that's sampled relatively coarsely along one direction, $x$, and much more finely along another, $y$. Sampling grid is regular. I need to interpolate between all these samples, with ...
781 views

### Basics of interpolation: is filter or upsample first?

I am studying interpolation filters. I'm under the impression that when talking about interpolating a signal, we filter and then upsample the signal. BUT In an article, Interpolation (Digital Filter ...
334 views

### Interpolate & sample period GNU Radio

I've a little question regarding interpolation in GNU Radio: I'd like to do an interpolation (by a factor of 2) and be able to change the sampling period of the samples interpolated but im having a ...
477 views

### Fractional Frequency Shifting a Discrete Signal in the Frequency Domain

In our current hardware-based signal processing pipeline, we have a time-domain signal $x[n]$ that we want to frequency shift by $f_0$. To do this, we multiply the signal by a complex exponential in ...
595 views

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### Performing Sample-Rate Conversion on Subchunks of an Audio Signal

I have implemented sample-rate conversion (SRC) from scratch in my hobby music player, and it worked fine. However, originally, the music player loaded entire audio files into memory and performed the ...
1 vote
517 views

### Symbol Timing Recovery with Fractional Sample per Second

I'm trying to write symbol timing recovery loop and taking help from "Digital Communications A Discrete-Time Approach" by Miachel Rice. MATLAB communication toolbox has also implemented the ...