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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Which method to choose to get linear phase response zero group delay low-pass filter?

Background: I do time-dependent simulations of physical systems. Like this: http://journals.aps.org/prb/abstract/10.1103/PhysRevB.91.115431 During the simulation, observables are recorded and later ...
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30 views

Short lowpass filter that also extrapolates lines

I'm looking for a short lowpass filter that also extrapolates lines, [0 1 2 3] --> 4, so I need (correct me) $H([\ 0\ \ 0.25\ \ 0.5\ ]) \approx [ 1\ \ 2\ \ 0 ]$ . How close can one get to this with 2 ...
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25 views

MATLAB fvtool: Setting the passband ripple below 0dB for a FIR Filter

I'm new to using filter tools in MATLAB and I'm having a bit of difficulty. I'm designing a lowpass FIR filter and I'm trying to keep the passband ripple below 0dB in the magnitude response. So far, ...
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2answers
53 views

How do I find the phase response of a filter from the filter equation?

I am new to this forum. I have been teaching myself DSP for the last two years, so my experience and knowledge has a long way to go. I am trying to find the phase response of a specific filter that I ...
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38 views

Is there a set formula for calculating FIR coefficients (for a LPF ir 96 taps)?

I need to calculate a series of coefficients for several FIR filters having 96 taps is there a standard or set formula for calculating these, it is a low pass filter.
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58 views

how to design LPH and HPF from APF

I came across a concept that says we can design LPH and HPF from APF when the transfer function of the two APFs given as $$\begin{align}A_0(z)&=1\\ A_1(z)&=\frac{-a+z^{-1}}{1-az^{-1}}\\\\ ...
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31 views

Low Pass Filter - pixel correlation

I am trying to understand low pass filters for image processing, I came across an article that stated that low pass filters effect noise more than the real data due to that the image Noise always ...
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62 views

Why Butterworth filter always starts my signal from from zero mark (amplitude)?

I am trying to filter my force signal using Butterworth low pass filter. so this is the signal, I have to filter (noise frequency is around 33 Hz). So when I use Butterworth filter with following ...
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125 views

How do I smooth this noisy signal?

I have a numerical solution to a problem in mechanics. I am computing the force applied to an object as a function of its deformation and in the problem, there is an instability, due to which the ...
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13 views

Digital low-pass filters: why not just zero out the dft? [duplicate]

Say I want to LP-filter $s[n]$. This is done by $s*\ell[n]$ where $\ell$ is some fancy low-pass filter. What I kind of don't get is why we can't just transform the signal obtaining $S[k]$ and then ...
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32 views

Choosing minimum sampling frequency of a filtered signal

I have a time series of acceleration sampled at 1000Hz to capture random impacts on a structure. The ringing of the structure (not of interest) produces noise which a 50Hz filter seems to eliminate ...
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24 views

Transform one-pole cascaded system into a biquadratic section

I have two cascaded one-pole sections with the same coefficient b for both sections. $$ y_A[n]=x_A[n]+b\cdot(y_A[n−1]−x_A[n])\\ y_B[n]=y_A[n]+b\cdot(y_B[n−1]−y_A[n]) $$ The final output of the system ...
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43 views

Cascaded one-pole sections and relationship to time constant

I have implemented a typical one-pole lowpass filter to smooth out some control signals. The form of the filter is: $$ y1 = x0 + b1\centerdot(y1 - x0) $$ x0 is the current input sample. y1 is the past ...
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1answer
60 views

calculating the stop-band edge frequency of a low-pass FIR

I have three information about a low-pass FIR filter. pass-band edge frequency pass-band ripple stop-band ripple I want to get the **stop-band edge frequency ** I've been googling for the ...
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2answers
92 views

Integration of square wave

trying to program an integrator. My input is a square wave and my expected output should be a triangle wave. However, whenever I pass it through my low pass filter algorithm (just a 2nd order ...
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1answer
47 views

Why is the output of the LPF half that of the real/imaginary part of the complex envelope?

The passband signal $\ u_p(t) = I_{[−1,1]}(t) \cos 400πt $ is passed through an LPF as $\ u_p(t) \cos(401\pi t).$ The question is to find the output. The example does the following: If we let $\ u_1 ...
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57 views

Why is my filtered signal offset from 0?

I have some random noise which is recorded from an accelerometer. This particular axis has been preprocessed by decomposing the data into frames which are then detrended to ...
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1answer
46 views

Relation between poles and cut off frequency of a filter

I noticed that for a low pass Butterworth filter, as the cut off frequency reduces, the poles get closer to the unit circle. Is it applicable to all filters and why is this so? As the normalized cut ...
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357 views

Smoothed Square Wave

new here and probably pretty unexperienced compared to the rest of you. This should be simple enough but just wanted some clarification. I'm trying to model an analog square wave oscillator with C. ...
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72 views

Interpolation based on sinc function

I implemented an interpolation method in C++ based on this equation ...
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2answers
117 views

How to Actually Use FFT to implement Low Pass Filter

have searched high and low for a practical guide to implement a simple 50Hz low pass filter on a signal.I understand the theory but its the practical but that's missing. If I was using MATLAB it would ...
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266 views

Digital low pass filter vs Kalman filter

I have experience with the design of FIR, IIR digital filters. I also know about the Kalman filter, but I am not skilled at using them. Consider the case of a low frequency signal from discrete ...
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187 views

Complex low pass filters

I am searching for documentation on the behaviour of complex low pass filters, and their application in telecommunications. Thank you
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what is magnitude responce at ω = π/2M for freqz function [duplicate]

what is magnitude responce at ω = π/2M.Code Given is ...
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43 views
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27 views

distributed low-pass filter frequency range

Suppose that signal's frequency ranges from 0 to some very high frequencies. One builds a low-pass filter which needs to be based on distributed element analysis because lumped-element analysis is ...
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77 views

Frequency response of a rolling linear regression

I am looking for a way to characterise the frequency response of the slope from a linear regression. We are exploring the effect of window length of the regression to the magnitude of the slope of the ...
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5answers
140 views

filter coefficients to know high pass and low pass filter

Looked on few questions already there in dsp.stackexchange and couldn't get the direct answer. Basically I have a kernel of a gaussian separable filter. ...
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39 views

Change of group delay scale in matlab

I have a question concerning the conversion of a matlab plot group delay scale. The book Digital Filters for Everyone, 3rd edition, by Rusty Allred has a matlab plot of group delay in samples vs. ...
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1answer
20 views

Transform a continuous time differential equation of a Low Pass Filter to discrete time

Assuming I have a linear differential equation of first order low pass filter: $$RC*y(t)'+y(t) = x(t) $$ And Assuming i know now that the input x(t) is being sampled at a rate of $T_s$ how can now ...
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1answer
66 views

Lag in financial trading vs Group Delay in signal processing

I'm a newbie to Signal Processing - and so I'm providing a "background" and a "question" section separately. Background: Suppose I have a linear filter (w.r.t. given as $\theta_{t+1} = \theta_t ...
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1answer
20 views

Denoising approach for a combination of several ADC voltage channles

I have 2 ADC channels of constant voltage measurement with small amount of high frequency noise only and no low frequency oscillations. The final signal should be the simple sum of those and denoised ...
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1answer
72 views

Possible to implement simple IIR filter with greater than 6 db/octave slope?

I am using the following IIR code as a low-pass filter in a software project, and it works great. However, I would like the slope of the filter to be much steeper as the one here seems to be very ...
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60 views

Implementation of a cascaded IIR filter

I am attempting to implement a cascaded IIR filter in MATLAB. I used fdatool to design the filter and exported it as an object, Hd. In my script, I import a log file of data I captured and store my ...
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208 views

Why are ideal filters not particularly useful/ hard to do?

Why is a LPF ideal filter: a) Not useful? b) Hard to make? I was asked to make a Low pass filter (simulink block) that will take an input of a cutoff frequency, and for a signal with a frequency ...
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1answer
58 views

Transfer function, amplitude response and difference equation for a filter

I've found a paper with a filter described in terms of transfer function, amplitude response and difference equation: transfer function of the second-order low-pass filter: $$ H(z) = ...
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2answers
243 views

Find Stopband Edge Frequency

I tried to find the stopband edge frequency.I know that the signal amplitude falls to -3 dB below the passband edge frequency.I examine a lot of DSP books so i don't any information about how to ...
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1answer
94 views

FFT “Brick Wall” Low Pass Filter Not Smoothing Output

I'll try to be as brief as possible. I have very limited signal processing experience. I have a data set that consists of essentially a big old sine function (with deviations from ideality), and lots ...
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1answer
69 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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1answer
80 views

Minimum Energy Delay Property

I have 4 systems which are represented in z domain like this: Where I know the poles and zeros. Then I compute Partial Energy Sequence of impulse response of all these system using this formula: ...
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1answer
92 views

What is the low-pass filter that gives minimal transient response?

As title says, what is the low-pass filter that gives minimal transient response? By minimal transient response, I mean minimal settling time with reference to very tiny amount of divergence of ...
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67 views

FIR Filter matlab command

i'm trying to understand the fir1 filter but i still don't get it. For example here i got an audio signal that i consider noise, i'm passing it through a low pass filter. ...
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19 views

Calculating the network function of a filter

Given a system, that behaves as a 1st order filter with network function $H(s)$. We input: $$v_1 (t)=1+3\cos(10^4 t)$$ And we obtain as output: $$v_2(t)=1+1.5\cos \left(10^4 t ...
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220 views

Which anti aliasing filter algorithm for efficient audio resampling?

I'm building a real-time audio resampler (think pitch bend) that needs to have a several different performance vs quality configuration options. I understand that I'll need to apply a low-pass filter ...
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63 views

Convert low pass continuous time filter design to bandpass, discrete time

I am trying to convert the continuous time transfer function of a second order lowpass Butterworth filter is given by: To a bandpass fourth order bandpass digital filter, I first apply the mapping ...
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52 views

transient response of simple digitalized RC low-pass filter

In http://en.wikipedia.org/wiki/Bilinear_transform#Example, digital version of simple RC low-pass filter is presented: $$\frac{1 + z^{-1}}{(1 + 2RC / T) + (1 - 2RC / T) z^{-1}}$$ where $T$ is ...
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48 views

How many different filters are needed for in an iterated filter bank?

I'm trying to implement an iterated filter bank as described in the Subband coding chapter of the Really Friendly Guide to Wavelets. However, the text seems to suggest that The advantage of this ...
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144 views

low pass filter with minimal ringing

I am trying to filter out some square wave signal to within a limited band (1/4 or 1/8 of the original), I realized that there's a lot of ringing in the wave when I use my filter (elliptical), I also ...
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435 views

FIR filter coefficients from frequency responses

I have frequency responses of FIR filter of order 13 from obtained 50 frequency samples. How can I get FIR filter coefficients of order 13? For example, in MATLAB a lot of possible ways I tried ; I ...
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91 views

extrapolate turning points for a sine weighted moving average?

On a stationary signal a sine-weighted moving average is calculated (SWMA: the coefficient vector looks like the first (>0) part of a sinusoid). The SWMA looks like this: very smooth: The future is ...