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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Basic question about Bandpass and lowpass filter using Python

I have a signal that is the sum of 3 signals that has just passed through a transmission channel. I need to put filters to this signal (bandpass and lowpass) and then apply demodulation and get one of ...
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64 views

GNU Radio Low Pass Filter doesn't work as expected with different transition widths

I'm new to GNU Radio and signal processing. I don't know if the following is a simple question, but I have been scratching my head about it. I created a simple flow graph with a random source (0-3) ...
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Choosing a good low pass filter in the wavelet scattering transform

What's the impact of a specific filter $\phi$ when building the wavelet scattering transform? I mean, if I compute the MFCC choosing different windows, (Hamming, Blackman, etc.), the behaviour ...
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Pressure signal

I have got an raw file which has pressure and time and temperature format and after coding I have got the plots but my main task is to analyse the data and understanding the influence of Bessel and ...
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111 views

Frequency response of an ideal low pass filter

I have an ideal low pass filter having unity gain and cutoff frequency 100Hz. If I provide an input having single frequency component at 100Hz(E.g.- cos(200pi t), will the low pass filter block the ...
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19 views

Find the output signal in a Low Pass Filter for a given cutoff frequency range

I have a scenario where ๐‘ฅ(๐‘ก)=2โ‹…sin150๐œ‹t +sin250๐œ‹t and g(t)=๐‘ฅ(๐‘ก)sin250๐œ‹ . The signal g(t) is passed as input through an ideal lowpass filter with cutoff frequency(fc)= 300๐œ‹ and passband gain= 3....
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Find the band pass signal for a given low pass range and cutoff frequency?

We know the fact that a bandpass signal is defined for real values. But for a typical scenario where we have a signal in the lowpass range:say : ๐‘ฅ๐ฟ(๐‘ก)=๐‘—๐‘‹0 sinc(Bt) and the transformation of the ...
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Signal filtering with physical limitations and estimated STD

I have a prediction mechanism that predicts some signal value. Generally the prediction look like this: The are some ranges of systematic error and I cannot do anything with this. But in many points ...
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34 views

Why the received SNR increases with bandwidth?

I am performing the following simulation: Complex chirp signal with bandwidth [-B, B] is transmitted through a multipath channel which has $N$ taps all being complex Gaussian variables (i.e., ...
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39 views

Requirements on Signal Spectrum for Fractionally Spaced Equalization

I'm constructing an ultrasonic communication system and I am struggling with the correct parameters for my receiver. In baseband, my channel input signal $x(t)$ has infinite bandwidth, since I use a ...
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73 views

Difference equation from a transfer function of a low pass filter

I need to get the difference equation from this transfer function: $H(z) = g \frac{1+a_1}{1+a_1z^-1}$ My math skills are too many years old, but I remember I need to get the Y(output) on one side and ...
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RT 60 from Impulse response

I have already the impulse response of an acoustic environment in the form of a series of signals over 300 samples. I have tried the procedure given in this platform - i.e. low pass filtering, Hilbert ...
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Why is my low pass filter decreasing the amplitude when using the inverse DTFT?

Goal: I'm trying to model a waveform in the time-domain for pattern recognition. My plan: Convert signal to frequency domain using FFT Reduce harmonics to hopefully isolate residual data, and make it ...
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What is the transfer function of the filtfilt?

I designed a Parks McClellan filter to design a lowpass filter. First, I created the order of the filter with firpmord(). Then I designed the filter with firpm() and created the impulse response. I ...
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52 views

Why an does an integrate-and-dump stage in a CIC filter provide the same functionality as the integrator and comb in series?

I have a hard time understanding why the combination of integrator and comb (integrate-and-dump) is the same as a separate integrator and comb in series like in this picture: Please explain why these ...
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My beat detection algorithm via a low pass filter is bad. Looking for tips for improvement with good trade-off between complexity and accuracy

In spring, I built a beat detection algorithm in Rust. It works for very simple songs but the problem is that I have to adjust the parameters of the algorithm manually for each genre and sometimes for ...
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Do we use calculator in radians or degree while calculating prewarping analog frequency in Bilinear Transformation?

Say $\omega_s=1.96\;,\omega_p=0.785$ For bilinear transformation-: $\Omega_p=2/T*tan(\omega_p/2)$ $\Omega_s=2/T*tan(\omega_s/2)$ Should I put my calculator in radian mode or degree mode. I believe it ...
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198 views

Do we guess the cut off frequency when passband edge frequency and stop band edge frequency are given? FIR Filter design-LOW PASS FILTER

Say passband edge frequency=0.25 $\pi$ Stopband edge frequency=0.35 $\pi$ What is the cut off frequency? Do we average these 2 frequencies and write the answer or what is the procedure to find cut off ...
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How to identify low pass, bandpass, band reject, high pass filter etc from given $|H(e^{j\omega})|$?

1) How is this a low pass filter? $0.99 \leq |H(e^{j\omega})|\leq1.01 {\rm\ for\ } 0\leq|\omega|\leq0.19\pi$ $|H(e^{j\omega}\;)|\leq0.01{\rm\ for\ } 0.21\pi\leq|\omega|\leq\pi$ 2) What kind of filter ...
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112 views

Butterworth Filter Transfer Function

Butterworth Filter frequency response is given as: $$H_a(j\Omega)=\frac{1}{\sqrt{{1+\left(\frac{\Omega}{\Omega_c}\right)^{2N}}}}\quad \text{where $N$ is the order of the filter}$$ and for the transfer ...
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Writing the specifications of digital filter, am I correct?

Design the FIR filter using suitable window for the specifications-: $0.899\leq |H (e^{j\omega}\;)|\leq1\;for\; |\omega| \leq0.2\pi$ $\; |H(e^{j\omega}\;)| \leq 0.01, \text{ for } \; 0.4\pi\leq \...
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Design an FIR linear phase lowpass filter using windows to meet the following specifications. What is given in the question? How to start solving it?

What is given in this question? I have not seen a single solution of these types of filter design problems in the internet. So I am confused, how do I proceed solving these problems. Can you guide me ...
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How to read the filter IIR design numericals specifications?

First of all I want to let you know about notations that I am using-: $\alpha_p$=attenuation factor of passband(in dB) $\alpha_s$=attenuation factor of stopband (in dB) $A_p$=Gain at passband edge ...
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Frequency response of a moving average filter/box car

I have designed a simple filter for an embedded system handling magnetic field data. The incoming sample rate is 128Hz from the sensor and we have output data rates of 1Hz, 16Hz, 32Hz & 128Hz So ...
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How to calculate analog cutoff frequency to design a digital filter?

$\Omega_c$=cutoff analog frequency In this example, what is going to be value of $\Omega_c$? Some teachers in youtube are teaching this method-: Is this method correct? If I use this formula, then ...
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Role of oversampling within resampling / pitch modification

I'm working on a pitch modification plugin involving resampling, and want the quality to be as high as possible. I currently use windowed sinc interpolation and lowpass filter where required. I ...
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Processing accelerometer and gyroscope data

I'm working on an instrumented headform to measure linear and rotation acceleration of the on impact, for which I'm using ADXL377 accelerometer and ICM-20649 angular rate sensor. What kind of ...
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88 views

How to calculate the total time delay of a first order linear filter on a signal?

I have a non-periodic signal. I apply a first order linear IIR filter on it. The filter will introduce phase shift to the signal that will appear as a total time delay. Is there a formula I can use to ...
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Invertible low-pass (Butterworth) filter in python (scipy)?

Question Is there an invertible low-pass filter built into scipy.signal (or other python package)? If so, what is it? If not, why not (is there something ...
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convolving an LTI with filters

I just started learning signal processing and one of the very first topics I begun with is convolution. I want to learn signal processing practically, therefore I opted to work with circuits(also a ...
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Question about impulse response of an ideal lowpass filter

Consider an ideal lowpass filter with a cutoff frequency of $\omega_c$. Following shows its impulse response: $$h[n] = \frac{1}{\pi n}\sin(\omega_cn)$$ Also, some references shows $h[n]$ as: $$h[n] = \...
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Low Pass Filtering, Welch's Method, ENBW

I am working on using Welch's method (https://www.osti.gov/servlets/purl/5688766/) to estimate a Power Spectral Density (PSD). This algorithm involves scaling a set of averaged FFTs by the equivalent ...
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Cut-off frequency for Low-pass filters in Arctangent Demodulation

According to literature, the arctan-demodulation method commonly used in Radio-frequency radar systems is the one shown below: Is there a rule of thumb regarding the cut-off frequency of these Low-...
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Amplitude / gain of difference of 2 known FIR low-pass filters

Given a discretely sampled sinusoidal signal (frequency $1/40$), and 2 Simple Moving Averages (SMA), better known as FIR low-pass filters of order e.g. $10$ and $21$, it can easily be calculated what ...
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Ideally Lowpass-filtered White Gaussian Noise: question about a derivation of variance and covariance

Consider white gaussian noise $\omega(t)$ that has passed through and ideal lowpass filter with bandwidth $B$. This filter has the impulse response $$h(t) = 2B\text{sinc}(2Bt)$$ Sampling the filter ...
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How do I add poles to this Biquad Filter for more rolloff

I now want a filter that has less of the frequencies to be cutoff. I would like a filter with 36, 48 or more decibels of rolloff Code ...
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How to find the minimum order for a low pass filter with different gain levels

I have the following for a filter with passbands having different gain levels, in this case I set the order arbitrarily to 100. Is there a way to find the minimum order that still satisfies the ...
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Verifying the result from lowpass filter

I have a event record from acceleration censer. I'm trying to remove gravity from the event record by low/high pass filter as following site shows. https://developer.android.com/reference/android/...
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135 views

Why is the ideal low pass filter not achievable?

I find myself to be quite confused by some concepts of DFT. Suppose I have some spectrum-normalized signal (which I simply receive without any prior information) $$A\cos\left(0.5n\right)\ +\ B\cos\...
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How do I make a two pole filter with resonance

I want a 40 dB/decade roll-off two-pole filter with resonance that does not peak when the cut off frequency is changed. I also want resonance to remain at a constant volume unless it is updated. @...
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Bio-signal discontinuity after FIR filtering

I'm filtering respiration signal. I have a signal of duration equal to 10 minutes, so I decided to divided it into period of 10 s. I filtered each epoch with FIR filter, but I have discontinuities ...
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LPF in the stage of IQ demodulator is it a analgor filter or digital filter?

I recently designed the LPF of the IQ demodulator using the Butterworth LPF refering to https://dspillustrations.com/pages/posts/misc/baseband-up-and-downconversion-and-iq-modulation.html. But I have ...
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How to choose median filter width?

In my signal processing pipeline, I normally expect data sampled at 100Hz, on which I then apply a median filter of width 10. My question is: How should I change the width for data sampled at ...
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Digital Audio Amplifiers

Can anyone tell me why a filter that blocks DC signal in an Amplifier would have a cutoff frequency of 4 Hz . Why would someone choose a frequency as low as 4Hz to filter out DC content before ...
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Get the transfer function when using the "designfilt" command in MATLAB

To put things into perspective, I initially had these four graphs in MATLAB, whose data were sampled with a rate of 10 samples/sec :- I wanted to remove some of the spikes on the blue graphs, so I ...
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Should we use a digital low pass or high pass filter to remove sensor bias?

Consider a continuous signal oversampled at, say $2 \;kHz$, and then system digital low pass filtered to a $100\;Hz$ frequency which is the control loop frequency. It is known that there is some bias ...
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Following a smoothing filter of a biological signal

)Following a smoothing filter of a biological signal. y[n] = Ay[n โˆ’ 1] + Bx[n โˆ’ 2] Please find the transfer function in the z-domain and find the impulse response function of this filter.
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Digital lowpass filter causing aliasing

I'm writing a biquad filter program in C++, using the RBJ Cookbook as the source for the formulas. https://www.w3.org/TR/audio-eq-cookbook/ The lowpass filter that I've made seems to half work. The ...
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Where do RBJ's analog shelving filters come from?

In RBJ's Audio EQ Cookbook, the analog prototype for a low shelf filter is given as such: $$H(s)=A\cdot\frac{s^2+\left(\frac{\sqrt{A}}{Q}\right)\cdot s + A}{A\cdot s^2 + \left(\frac{\sqrt{A}}{Q}\right)...
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Designing digital low pass filter with low pass-band group delay

I'm interested in specifying a digital low pass filter with low (and near constant) pass band group delay. I tried python's spicy.signal.minimum_phase to transform ...

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