# Questions tagged [lowpass-filter]

A low-pass filter is an electronic filter that passes low-frequency signals but attenuates signals with frequencies higher than the cutoff frequency.

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### Gaussian filter as a low pass filter

Can anyone explain me how is a Gaussian filter a low pass filter? It may be a simple thing but I just can't seem to wrap my head around it. Also while applying a low pass filter for bandlimiting (to ...
1answer
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### Determine filter given transfer function [closed]

I am given $$H(z) = 1 + \frac{\alpha}{1-\alpha z^{-1}}$$ where alpha is between $0$ and $1$. This is apparently is a low-pass filter with cutoff frequency $f_c$. How can I see that? And how can I ...
1answer
395 views

### Consider an ideal low pass filter $H(\omega)$, and the input to this filter is the periodic square wave $x(t)$. Find the output $y(t)$

The solution to the problem is $$y(t) = 5 + \frac{20}{\pi} \sin(\pi t) + \frac{20}{3\pi} \sin(3 \pi t)$$ and to get that the solution says to find the Fourier series expansion of $x(t)$ and I am ...
1answer
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### Digital Lowpass Filters, basic questions

Forgive the newbie questions, I'm just starting out and wanted some basic information. I have a signal coming from a digital gyro, most of the useful information is below 90hz but I am seeing ...
0answers
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### Low pass image filter

I have feature in my camera that indicates "Low Frequency Flat Field correction" and I want to evaluate its impact on the image. How can I do this? Currently I can only take pictures of a uniform ...
0answers
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### Applying Jake's remez exchange algorithm for filter design

I have found C implementation for remez exchange algorithm(https://github.com/janovetz/remez-exchange/blob/master/remez.c) and I want to use this to implement a generic prototype lowpass filter. ...
1answer
927 views

### Upsampling before performing pulse shaping

I know what an upsampler does. We insert L-1 zeros between the samples. As a result, it creates spectral repetitions. What if we have a symbol impulse stream and then we apply a Root Raised Cosine ...
1answer
34 views

### Overview of regression methods between the data

I am trying to find different approaches (classic and modern) in order to find a regression function between data (in time domain) with high-frequency noise. Consider the result of this code (in ...
1answer
111 views

### Apply LTI filter to incoming signal stream [duplicate]

Typically, when I want to filter a signal with an LTI filter (in this case a low-pass filter), I just convolve the signal with the filter. However, what do I do if I have a stream of data that I want ...
1answer
832 views

### Lowpass Lanczos filter

I am new to Lanczos filters and trying to figure out how they can be used to generate a zero-phase lowpass filter with good time-domain properties. This example shows how to implement such a filter in ...
0answers
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### Design of a Butterworth lowpass filter in MATLAB

I'm using the Signal Processing Toolbox in MATLAB to design a Butterworth low-pass filter. I'm told that my filter has been giving some unexpected results. In particular, when the values from this ...
1answer
2k views

### Removing low frequencies from a signal

I am trying to remove low frequencies from a signal and intuitively I chose the high-pass filter, more specifically - a Butterworth filter, Order 4 (because I am not sure how to choose properly the ...
0answers
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### What is the reason for this 'linear “error”'

Here's MIM (Magnitude Invariance Method) thesis (press the "View PDF" to get the theis with MATLAB code in hands) and here's a plot showing the issue I'm trying to solve: Magnitude responses for one ...
1answer
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### Lowpass : What is wrong with average filtering?

The question is : What is wrong with averaging as low pass filter ? The details : I want to lowpass filter a signal to downsample it. The constraints are : I have no RAM available and I work in ...
1answer
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### Downconverting real signal to IQ baseband

Despite reading various answers on this site and on other sites I am still confused about how to convert a real-valued signal back down to its original IQ baseband values. Note I am still a beginner ...
3answers
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1answer
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### ifft doesn't recreate original signal

I want to convert given signal into frequency domain and do some calculation and then convert that signal into time domain. Here is the code which I am trying out ...
2answers
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### How to apply low-pass filter to an I/Q signal to get baseband signal?

Can anyone help me with the demodulation technique of a modulated signal? I mixed it with I/Q signal. But I am very confused about low-pass filtering. I am trying to apply a low-pass filter, but I am ...
3answers
158 views

### Odd problem with really long sinc filters

I'm trying to build a "perfect" low-pass filter as an exercise to test that I've understood some basics in signal processing. I've computed the required length of a sinc function such that at either ...