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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876 views

How does sampling rate affect discrete filters?

I am just starting to learn discrete filters and I could use some help. I understand continuous signals and filters. I am trying to understand the math behind discrete filtering. For example in the ...
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157 views

Multiply filter kernel by sine

1)Suppose that we have low-pass filter with cf equal to 0.1. How frequency response would look like if I multiply filter kernel by sine with frequency say 0.3? How this is related to converting low-...
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547 views

Calculate cutoff frequency of filtered data

I am processing data which was put through a low pass filter at some point. Looking at the FFT, I can see that it is less than the Nyquist rate. I am trying to filter another set of data so that the ...
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35 views

Statistics of the output of a high bitrate signal filtered through a narrow band low pass filter

I was wondering what would be the statistics of the output of the filtering of an extremely wideband signal (e.g. 10 Gbps random data stream) through a narrowband low-pass filter (e.g. 10 MHz LP). I ...
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134 views

Recovery of Bandlimited Signals after Companding and Low Pass Filter

Let $\Omega > 0$ and denote by $\mathcal{B}_\Omega$ the subspace of $L^2(\Bbb R)$ consisting of signals that are bandlimited to $(-\Omega, \Omega)$. Denote $\mathcal{L}_{\Omega} : L^2(\Bbb R) \...
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549 views

Building a Low-Pass FFT filter for a noisy current pulse signal

I have some (well lots) of data signals which are measurements of current pulses. The current pulses are the result of spark breakdowns (20 kV + 700 pF capacitor so quite energetic) and my problem is ...
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2k views

How do decide which order my butterworth filter should have?

I have a signal that was recorded with around 300 samples in a second. Now I want to run a low pass and a high pass butterworth filter over it. The frequency for the high pass filter is around 0.05 Hz ...
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2answers
289 views

Filter for Reducing Background Noise in Image

I have images where there is a lot of "black" background (few shades of black). (In many images at least half the pixels are background). I need to get interest points from the image, but because the ...
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3answers
6k views

What is the intuition of “averaging is a low pass filter”?

As I know, the shape of a low pass filter in time and frequency are as follow: But how averaging work like a normal function in time domain? Is there any intuition in it?
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5answers
196 views

Amplitude reduction of Simple Moving Average on sinusoid

When a -causal/non-centered- simple moving average filter (arithmetic mean) with length $n$, is applied to a sinusoidal curve with period $p$, and the resulting curve is compared to the original input ...
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1answer
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once again,confusion between phase and group delay [duplicate]

Despite,reading up on this I'm unable to find crystal clear clarity on the differences b/w phase and grpdelay functions and interpretation of grpdelay's output. I have designed a low pass butterworth ...
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117 views

Why does sampling frequency affect the filter results?

I have a big issue, basically my goal is to create a low-pass butterworth filter around 0-35Hz with a sampling frequency of 5000Hz. My Matlab code is ...
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826 views

Poles and zeros map

Given the following map of poles and zeros for some $H^L(s)$: How can I understand from the map that the given Transfer function is LPF? Hence the poles are located at the hight frequencies it should ...
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4answers
94 views

Can I use IIR or FIR to get a sliding mean?

My output signal shall be computed by (meta code): o = 0 # or some arbitrary initial value for i in input: o = (o * 99 + i) / 100 print o I call this a "...
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2answers
112 views

Optimizing Two Parallel IIR Filter Sweeps

Got an audio related question here; So I have two IIR low pass filters that work in parallel to do a filter sweep. Basically: ...
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2answers
481 views

my Butterworth lowpass formulas do not agree with Fisher webpage

I want to implement Butterworth low-pass filter. Thanks to this question, I have found out that the filter coefficients can be generated using Tony Fisher web-site or using his code. But the problem ...
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821 views

How to set the frequency cut-off for a low pass RC filter?

How do I set the frequency for a low pass filter illustrated below?
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675 views

Types of Filters

Which filters response is maximally flat at origin? It seems to me that both High Pass Filter and Band Pass Filter have maximum flat response at origin, although it is almost zero in case of Bandpass ...
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1answer
3k views

Realisation of a passive RC low pass filter

I have an unusual low-pass filter problem that I would like to realise with a passive RC network (Note 1). It's easy enough to find prototype filters for passive RLC networks, or for the various ...
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4k views

How to determine the window size and weights in Weighted Moving Average (WMA), given desired cut-off frequency?

I am trying to smooth my discrete-time data points using the method of WMA. Currently, I am using n as the window size and the weight array, ...
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81 views

Why notches in sinc filter response

Below response shows sinc1,sinc2 and sinc3 filter response. I understand that notches in the frequency response happens at the output data rate of the sigma-delta ADC. But I am not able to figure out ...
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Designing ideal lowpass filter in the form of FIR

How to design a ideal lowpass filter by cutoff frequency of π/4 in the form of FIR filter by 64 samples using matlab?
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2answers
237 views

How do Anti-Aliasing Filters filter the signal?

I have programmed a anti-aliasing filter that uses the fourier-transformation and makes a perfect cutoff on my desired cutoff frequency for downsampling without aliasing. I have read about other ...
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3answers
461 views

Low-Pass Filtering on Small Chunks of Audio

I've got a script (Python) that chops 44.1 kHz realtime audio into 10 ms chunks, processes each chunk, and stitches the chunks back together with no added artifacts. I'm trying to create a low-pass ...
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1answer
165 views

Why does my low pass filter diverge below 7000 Hz?

I'm trying to create a LPF, using language JAVA. My first aim is to understand how filters design is working and the second one is to create a "home made" equalizer with "home made" filters. To help ...
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1answer
222 views

Compensate for FIR filter attenuation

Is there a simple way to compensate for the reduction in amplitude of a low pass filter of a noisy sine wave signal that has been smoothed using a FIR filter so that the amplitude of the smoothed sine ...
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1answer
560 views

how to understand frequncy response and lowpass filter?

I am troubled with understanding freqency response. In lecture, my teacher talked about $H(f)$, which i know means that the response depend on frequency, $f$. But when I read text book, it uses a ...
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1answer
381 views

Is ideal LPF a LTI system? And is it time invariant?

Ideal filter time-domain impulse response is $$h(t) = 2B \operatorname{sinc}(2Bt)$$ It is not causal nor BIBO stable. Is it time invariant? And how can i prove it?
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209 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 ...
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1answer
495 views

Low-pass filtering bounces when signal doesn't start at 0

Say I have an array representing a signal, going from 30 to -30 in 1000 increments, with a little bit of noise on those values. If I apply any king of low pass filtering (Besset, Butterworth, Savitsky-...
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2k views

Interpolation based on sinc function

I implemented an interpolation method in C++ based on this equation ...
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1answer
495 views

Is it necessary to taper two ends before fft a time series?

I saw in some codes people always taper the ends of a signal using a cosine taper. Is that necessary and why?
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517 views

Why we need distances in Ideal LPF?

Here I have a MATLAB code for Ideal Low pass filtering an Image. In the below code they have used D=sqrt(U.^2+V.^2); which finds some distances. Then this distance ...
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2answers
68 views

Pre-Warping is not working on bilinear transform

New here and I just wanna ask the question of what happens when your pre warping doesnt work on your bilinear transform? I am assuming my isnt working as part of my research I have read that the ...
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What is the cut-off frequency for this low pass filter? [closed]

I don't have any background in analog lowpass filters; and I am curious how can i decode this circuit.
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64 views

How does this represent a low-pass filter?

I am faced with the following code snippet to get an understanding of a F0 estimation algorithm (DIO). Have a quick look below: ...
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56 views

Ideal low-pass filter in the Frequency Domain

I try to create a low-pass filter to apply it for an image. $$H(U, V)=1 \text{, if }D(U,V) ≤ D_0 \text{, and } 0 \text{ otherwise}$$ and $D(U, V) = \sqrt{U^2 + V^2}$ ...
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37 views

Low pass filter with different non linear phases [closed]

I want to design low pass filters with different non linear phases. Means the magnitude response of all low pass filters will be same but having different non linear phases.
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38 views

Why exactly is the Guassian filter a low-pass filter?

In image processing, a Guassian filter is used to blur an image. A low-pass filter is a filter that attenuates the high frequencies, preserving only smooth variations in the provided image. Is a ...
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159 views

Low pass to low pass transformation coefficient?

I am unable to solve this question, 10.10 from GATE IN 2004 (a previous year question paper for an exam targeted at engineering graduates in India.) So I tried to solve the 10.10 by considering the ...
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2answers
136 views

Cascading a filter with itself to form a higher-order filter?

I've been given an audio signal with some high frequency noise. The professor gave me the system function of a lowpass filter that gives me control over the cutoff frequency: $$H(z)=\frac{1-\alpha}{2}...
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344 views

How to smoothen signal with missing values before differentiation?

I want to differentiate a noisy signal with many, randomly located, missing data values. Which smoothing techniques should be applied before differentiating the signal? I have a velocity signal at ...
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1answer
227 views

Instantaneous velocity and displacement from acceleration signal using a proper filtering method

first I need to mention I'm new to signal processing. here is the situation: I have an acceleration time-series derived from an accelerometer I wanted to imply a filtering method like high pass ...
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2answers
135 views

Can I combine an IIR (an EWMA) with a maximum?

I'd like to have a exponentially weighted moving average (EWMA) which is raised to the value of the input signal whenever this is higher than the filter output. This taking of the maximum shall take ...
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1answer
381 views

FIR filter design with flat passband but equi-ripple stop-band

I am looking for a lowpass FIR filter with flat passband but equi-ripple stopband. In other words, it likes Chebyshev_filter Type II except that it is FIR instead of IIR. Linear-phase is preferred. ...
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4answers
152 views

What happens, when an unlimited bandpass-signal gets mixed?

In theoretical books there's always a bandpass-limited signal being mixed, that's been low-pass filtered beforehand. But what happens, if the RF-signal from the antenna isn't band- or lowpass-...
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446 views

How to design a FIR low pass filter and force a subset of filter coefficients to 0?

I'm looking into interpolating a signal by 2x and came into this matlab function interp: interp Interpolation — increase sampling rate by integer factor ...
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1answer
97 views

Does a filter need to completely attenuate high frequencies to be considered low-pass?

I'm looking at a system with a frequency response that is: $$H(e^{j\omega})=\tfrac{1}{4}(2\cos(\omega)+\cos(2\omega)+2)$$ I think the magnitude of this system looks like this (not sure what is the ...
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1answer
2k views

Cancel Drift after numerical integration

I am trying to integrate angular acceleration obtained from a set of accelerometers positioned specifically at opposite corners of a cube, based on the paper EcoIMU: A Dual Triaxial-Accelerometer ...
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Bandwidth of lowpass filter?

This article here on the Window method for FIR filter design speaks of the total normalized bandwidth of the lowpass filter in $\textrm{Hz}$ (counting both negative and positive frequencies) What ...

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