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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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Using a Passive 1st Order RC filter to Extract DC Component

I am trying to extract the DC component out of a PWM signal produced by the MCU using a LPF. I understand that 1st order RC filter is looked upon as being amateurish because the gain in the passband ...
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10 views

give me a two signal which is graphicaly varify low pass signal has linear phase [on hold]

give me two signals using MATLAB, and graphically verify that if the low pass the filter has a linear phase, there is no phase distortion in filter output; Otherwise, the filter output has phase ...
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2answers
53 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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36 views

Filter to remove high frequencies in R

I'm having a problem with a signal, I need to leave only the low frequencies so smooth as possible, because then this signal will be the input of a neural network, so I need to reduce complexity. The ...
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1answer
33 views

4-phase FIR LPF in MATLAB

I'm trying to create a low pass FIR filter using the coefficients I found in ITU 1770-3 on page 18. This is the last piece of the puzzle for an audio loudness metering algorithm I'm working on. I'm ...
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204 views

Savitzky–Golay filter vs. IIR or FIR linear filter

A traditional IIR / FIR filter (lowpass to remove the high freq oscillations), e.g. moving average, or a Savitzky-Golay filter can all be useful to smoothen a signal, such as an envelope signal: ...
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1answer
37 views

Time-domain LPF not showing expected behavior

I am trying to implement a simple first-order Butterworth Low-Pass filter in Python. I have some code that makes use of scipy.signal.butter and scipy.signal.filtfilt. It works fine, but I wanted to ...
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42 views

Difference between 2D image resampling and 1D signal resampling

I implemented a rational resampler for 2D bitmap images by the following steps: Zero-stuff to interpolate Low-pass filter to remove high frequencies introduced by zero-stuffing Low-pass filter to ...
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1answer
31 views

Parallel Cascaded FIR Filters

I have a relatively simple question. I know if you connect multiple LTI systems in parallel, overall system's frequency response is the sum of each LTI system's frequency response. Therefore, what ...
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27 views

Make an envelope smoother but keep the sharp attack

I have a signal x for which I would like the envelope. I have taken the Hilbert transform (like in this question): ...
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1answer
90 views

Detecting fundamental zero crossing point

I am looking for ideas from the more experienced members on algorithms for determining the fundamental zero crossing point of a 50 or 60 Hz signal. The fundamental zero crossing point is then used as ...
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3answers
50 views

How to Classify Image Filter as Low Pass Filter (LPF) or High Pass Filter (HPF)?

I am currently reading on the topics of image filtering and convolution kernels. While the process of convolution is clear to me, I do not understand, how one arrives at the statement, that a certain ...
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1answer
59 views

signal reconstruction [closed]

I'm new to DSP so the question might seem a little bit stupid: When using a low pass filter (say Butterworth filter) with Python, I came across an algorithm with which I can reconstruct my signal ...
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1answer
65 views

digital IIR filter delay and oversampling

Can oversampling decrease the delay of digital IIR filter? Imagine there is some digital signal going into processor that applies low pass filter.Lets say its 1 KHz sample rate and the filter is ...
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1answer
50 views

Problem with 1st order Massberg LPF [duplicate]

I'm trying to implement this filter in title by following the book "Designing Audio Effect Plug-Ins in C++" By Will Pirkle Problem I'm facing is the magnitude response error when comparing against ...
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2answers
54 views

Initialize Hi Pass Filter

I want to remove the DC from a ADC, so I designed a two-pole, 1 Hz high-pass Butterworth filter for a signal sampled at 10kHz. The filter coefficients are: ...
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0answers
81 views

Issue with the Massberg Analog-Matched Low Pass Filter

Implemented the filter mentioned in title using Octave and couple sources Vicanek and Zeitlin (LPF.cpp). Got filter working otherwise but, ... when tested the responses against 'analog model' of the ...
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1answer
45 views

Simple question about Sinc()

Suppose I use the ideal lowpass filter eq to attempt creating a IIR filter using it : $$ h[n] = \frac{\sin(\omega_c \, n)}{\pi \, n}, \qquad -\infty < n < \infty $$ Obviously, I can't really (...
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1answer
60 views

How can I determine the order of filter?

This is my first study about signal analysing. I'm very confused about filter order. My problem is how can I know whether its 12-th order, or 2nd order like the book says so? I already knew that slope ...
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1answer
106 views

How to filter out those outliers

I'm struggling to filter some data from an accelerometer. I need to do it in python (and not just on the device collecting the data) to fix the data I have, so that I can build some classification ...
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2answers
40 views

How do you initialize the output of a second-order-section filter?

I've got a 4 stage second-order-section filter. When I turn this filter on, it assumes it is starting from zero and takes forever to converge on the actual signal. For example, let's say I have a ...
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1answer
32 views

CCDE processing vs. Scilab function

I have used Scilab functions to produce a low-pass filter for an audio signal and the coefficients for the associated constant coefficient difference equation (CCDE). I then produced filtered signals ...
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3answers
58 views

Usefulness of Practical filter ouptput

If a practical filter can't remove all unwanted frequency components like ideal filter, does that mean unwanted frequency component are still present after filtering? how can we use such distorted ...
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38 views

Objectively determine the best filter to preserve peak value and width of the signal

what should be the process to determine the correct filter to smooth a force signal (impact) where the peak value (or peak values) of that force and the impulse (physics) will be used for further ...
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1answer
129 views

Frequency analysis to determine low-pass cut off frequency

I collected some data for a practical application, where the signal represents force data obtained from an impact of a punch against a force plate attached to a quasi-rigid rig (it moves once the ...
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1answer
41 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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1answer
115 views

Do you recognize this filter?

I'm trying to decipher the uncommented source code of SoundBox which is a little music tracker written in javascript. There is an included synthesizer, which applies a filter on the output samples. I'...
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2answers
66 views

High/Low Pass Filters from Zero

I everyone, I'm a computer scientist but not from the signal processing community. I want to implement a real time digital low pass filter (to begin with) for a sound processing application. I've ...
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0answers
139 views

How to design a low pass sinc filter given a time constant?

How can you derive the cut-off frequency $f_c$ for a given time constant $\tau$, in order to be able to design the low pass sinc filter: $\mathrm{filter} = 2f_c \mathrm{sinc}(2f_cx)$ The formula for ...
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42 views

LC Low Pass Filter Design

I am attempting to design a low-pass filter for a subwoofer, as the audio amplifier that is connected to it does not filter any of the sound coming in, and it is getting pumped full of high frequency ...
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37 views

How to combine filters' effects?

My question is about the use of many filters on a sound signal. I found the following transfer functions for the high cut, the low cut and the pass band filter : H = K / (1 - x^2 + j.x/Q) H = K / (1 -...
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2answers
61 views

Gaussian pyramid: why needs the image to be downsampled

In the context of a gaussian pyramid, why is the image downsampled separately although the numbers of pixels are decreased through smoothing already? In my understanding, the number of pixels will ...
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1answer
70 views

How to decompose raw acceleration signals into gravity and dynamic acceleration?

I have a data from $3$-axis $50$ Hz accelerometer, acceleration over each of $3$-axis: $acc_X,\ acc_y,\ acc_z$. I want to decompose acceleration into gravity and movement components. First ...
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1answer
154 views

How to design a lowpass filter using Hamming window and sinc function

I have these three equations and have a noisy voice signal. I have to design a low pass filter of length N=1000 using hamming window technique. I have selected its cutoff frequecny 0.25 (normalized). \...
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63 views

Low/High cut filter : how does it work?

I have a question about the low-cut and high-cut filter on an equalizer. Let's say, for example, that I'm using a 15 band equalizer with the following central frequencies: 25, 40, 63, 100, 160, 250, ...
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20 views

Two zeroes at $z^2+2z+1=0 \iff z=-1$ corresponds to a double damping at the Nyquist frequency?

If a transfer functoin has two zeroes at $z^2+2z+1=0 \iff z=-1$, then this corresponds to a double damping at the Nyquist frequency? Is this standard knowledge?
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2answers
115 views

How to Classify a Kernel as Low Pass Filter (LPF) or High Pass Filter (HPF)? How to Transform an LPF Kernel into HPF Kernel?

The filter impulse response is [1/9 1/9 1/9;1/9 1/9 1/9;1/9 1/9 1/9]. how do i determine whether it is an Low pass filter or a high pass filter. If this is a low pass filter how do i convert it to a ...
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74 views

Estimating frequency when there's little isolation between signal and noise frequencies

Say I have a signal which is guaranteed to have a frequency between 110-120 Hz but is corrupted by interference signals that're very close to this frequency range. For example, let the interference ...
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1answer
1k views

Apply Low pass Butterworth filter in Python

I want to use a low pass Butterworth filter on my data but on applying the filter I don't get the intended signal. Here is the dummy code: Signal A: ...
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72 views

Discontinuities in digital down conversion (frequency translation and LPF) of a continuous data stream in Python?

I have to process large data files containing a BPSK, biphase-L encoded signal with 72 kHz carrier frequency (expected), 18 kHz baud rate. The sampling rate (fs) is 648 kHz, chosen to be an integer ...
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2answers
118 views

Short length windowed sinc filter

I have a 50-60Hz signal being sampled at a frequency of 25 kHz & I'm trying to filter all frequencies beyond 70 Hz with a reasonable steep transition band (approx 4 Hz) & good attenuation (~40+...
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1answer
34 views

Help generating coefficients for basic FIR LPF

I'm trying to generate coefficients for a FIR low pass filter to be used in an FPGA. I'm using python (scipy.signal) to attempt to do this, but am having trouble getting coefficients in a usable form....
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1answer
27 views

What does “ripple limit cutoff” mean?

So I'm reading the datasheet for MAX98357A. It's an audio amplifier that receives digital signal using I²S bus and has integrated digital low-pass filters of the IIR and FIR types. In addition to ...
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1answer
81 views

How to properly filter a BPSK demodulated signal?

I am new to this field and yesterday I began a project for BPSK modulation. So this is what i did: $\ x(t) = 0 $ or$\ 1 $ binary data $\ Fs = 15 $ sampling frequency kHz $\ Fc = 10 $ carrier ...
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1answer
124 views

Condition for modelling noise as white noise

I am reading a book on Communication System by Simon Haykin. In the topic of white noise there is a paragraph "We may state that as long as the bandwidth of noise process at input of a system is ...
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2answers
114 views

should I apply low-pass filter when calculating central derivative?

Let us say that we have a discrete signal $I_n$, $n=0, 1, 2, ...$. According to Nyquist theorem the maximum frequency for such discretization is $f_{max} = 0.5$. Now imagine that I want to calculate ...
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1answer
83 views

AM demodulation from a real RF signal

I'm capturing an RF signal transmitted at 433.8MHz, with a bandwidth of about 50KHz. My goal is to be able to save it as a .wav file. I'm using an RTL-SDR dongle and a software named HDSDR, where I ...
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1answer
50 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
79 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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935 views

AM Modulator-Demodulator in Python

I am trying to make a AM modem using Python Numpy and Matplotlib. I am successful in generating the AM Signal but I cannot demodulate it using a lowpass filter function that I made. The demodulation ...