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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How to test the FIR filter in C++?

I am almost done with design and implementation of my first FIR filter using C++. Its a Sinc-Windowed FIR filter designed for a cut off frequency of 100 Hz with sampling rate of 500, with a filter ...
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74 views

IIR low pass filter: floating point and fixed point

I have implemented an IIR low pass filter in direct form 2, the input to the filter is a unit impulse $\delta[n]$. I have calculated the output of the filter for the mentioned input using the ...
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43 views

Why should the cut off frequency and the transition bandwidth (BW) be expressed as a fraction of sampling rate?

I came across this confusion in Chapter 16,"Book - The Scientist and Engineers guide to DSP" and Topic is "Windowed Sinc-Filters". I am doing some calculations for designing the sinc filter and came ...
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24 views

How to concatenate IIR filter (Butterworth) with a Matlab function and evaluate the integral

I have a function of $j\Omega$ and $v$ (velocity), i.e.: $$A(j\Omega,v)=\frac{(j\Omega)^2}{p + \frac{j\Omega}{v}}$$ where $p$ is the pole. I want know how $A(j\Omega,v)$ modify its behavior, when I ...
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Can someone please explain or describe me the behaviour of equation 2 in my question, relevant to filter response (Sinc Interpolation)

At present, I am learning the theory of operation of resampling for bandlimited periodic discrete signals using sinc interpolation.I am developing a design flow and having difficulty in understanding ...
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49 views

Periodic Signal Fourier Transform

If I have a signal x(t) as follow x(t)=$\sum\limits_{k=-∞}^∞ R_{T}(t-2kT)$ $R_{T}(t) = \begin{cases}1 ;&[\dfrac{-T}{2},\dfrac{T}{2}] \\ 0; & \text{otherwise} \end{cases}$ ...
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39 views

Output of a band pass filter

Signal x(t) = | cos(2πft)|, f != 0 is the input of an ideal band-pass filter with bandwidth B = 3f/2. How can i Find the ...
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62 views

Question regarding filter implementation - Audio EQ Cookbook

Some of you may know the infamous Audio EQ Cookbook. You can take a look here. We tried to implement the functions there to achieve a implementation for a Lowpassfilter. However, when we try to ...
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63 views

How to produce a high-pass filter from a low-pass one?

I already have a low-pass filter and want to remove the DC offset of a signal with a high-pass one. I guess you can subtract a low-pass filtered signal from the original signal and the result is a ...
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51 views

Selecting the Low Pass FIR Filter, Decimation, DSP

I'm studying DSP, but I have weakness about it. I was reading this: http://www.eetimes.com/document.asp?doc_id=1275556 But, I don't know how select the Low Pass Filter. I am assuming that this ...
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Using bilinear method while filtering a signal - Matlab

i have to current signal in matlab: Fs = 8000; T = 1/Fs; N=512; t = (0:N-1)*T; ...
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Calculating Savitsky-Golay filter coefficients - normalization

using the matrix equations found on Wikipedia i wrote some Python code to compute the Savitsky-Golay coefficients for m data-points, using a polynomial of degree k, here it is: ...
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59 views

up down sampling and low-pass filters

I am trying to figure out what seems very trivial thing about down sampling and up sampling. The problem that I am facing is how to find the effects of up sample on a signal followed by a filter ...
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21 views

Sampling: how to determine a “good” sampling rate based on a given filter

I assume that the sampling rate is w_s = 2w_max if we have an ideal low-pass filter that nulls frequencies whose absolute value is higher than that of w_max. Therefore, that the only reason for ...
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41 views

filter design for ECG

I would like to ask how to design a digital filter to remove $50$ Hz interference on an ECG signal. Do I need to use notch filter? Thanks.
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35 views

Why do we use Hilbert Transform in discrete time domain?

I have few questions regarding hilbert transform, Questions are as follows: 1)What are the benifits of using hilbert transform hardware and software point of view? 2)Cannot we use any other digital ...
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76 views

Digital low-pass filters; best practice application

I have time domain strain gauge data from a structure which is subjected to low frequency, random loading. The signal / noise ratio is pretty good, but I would like to try to improve on it as much as ...
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47 views

Is it possible from 1 order cascading low pass filters to make a butterworth filter

Today I have heard, that is "impossible" to make low pass butterworth filter from cascading 1 order low pass filters(RC). I am trying to discover is that true, but I can find little to none ...
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35 views

How can you intutively figure what the impulse response will behave like?

I was trying to understand convolution from this book and came across this figure: Here, the input signal is a combination of a sine wave and a ramp. In fig a, the input signal is convolved with a ...
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how could i fill missing data?

i tried a forecasting method and i want to check if it is correct or not and why? my study is about evaluating mutual funds for two kind of them it is a comparative study and i wan to use gcc index ...
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82 views

moving average filter vs up sampled low pass filter

I'm experimenting on different low pass filters in matlab. I've considered a vector x=[1 0 1 0] ; an up sampled low pass filter by a factor of two. And the frequency response turned out to be And in ...
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138 views

FIR vs IIR filter

In my filter design, FIR gives order 14 and IIR gives order 8 or 4. so what are the disadvantages of IIR design?
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53 views

Time-averaging as a low-pass filter?

I run into the following filter that is supposed to do some type of time averaging of $x$ $$y[n]=G\cdot y[n-1]+(1-G)\cdot\dfrac{x[n]-x[n-1]}{T} $$ where $$G=e^{-2\pi c T} $$ $T$ is a time ...
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56 views

How to pad a windowed sinc filter in the frequency domain

I'm creating windowed sinc filters to apply them to certain signals that I'm dealing with. To design the filters, I'm using the approach described in the book "The Scientist and Engineer's Guide to ...
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14 views

Optimal estimation of the static points obtained using kalman filtering?

I have used kalman filtering in the field of image processing. Now I would like to use kalman filtering to have a better estimate of the static points observed by a moving object. Given Data: My ...
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Discrete algorithm for low pass filter

I am working on a position controller for a marine vessel. I have an measurement signal containing the y-position of the vessel that consists of both low frequency (<.1 rad/s) and high frequency ...
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85 views

Appying a Filter Several Times on Data

I have data from an experiment and apply a lowpass filter (digital Butterworth filter, in Matlab). My question ist what happens if I apply the same filter e. g. 2 times on the data? What is ...
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50 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 ...
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72 views

correct for shift from butterworth filter?

I have implemented a python butterworth filter but it seems to shift the data a lot, the x location of my data is very important to me for my analysis. Is there a way to correct for this shift ...
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53 views

How to calculate the time delay of a signal by a first-order filter

lets assume following signal $$x=a_1 \sin(2\pi f_1 t) + a_2 \sin(2\pi f_2 t).$$ This is passed through a simple single-pole filter with cut-off frequency $f_c$. How is $x$ delayed by the filter (peak ...
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318 views

Audio signal processing

I am trying to code audio signal processing software in java. Purpose: It will use audio signal processing library to filter out noise from the raw PCM based input (.wav) of heartbeat recording. ...
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75 views

Low pass filter to maintain edge information

I am looking for a kernel acting as a low pass filter that satisfies these conditions: $$K(-\mathbf{u})=K(\mathbf{u}) \tag{1}$$ $$K(\mathbf{u}) \ge K(\mathbf{v}), \;\; \text{if} \;\; ...
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Simulation and theory of first-order low pass filter

I am trying to teach myself some signal processing and control theory. I'm currently working through THIS tutorial. I've started an ipython notebook to keep my notes in. Unfortunately, something is ...
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Low-pass vs median filter delay

I need to design a filter to reduce noise from accelerometer readings and use this data to a control system. One of the problems of a simple low-pass filter (like a single pole IIR filter) is the ...
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63 views

Designing the filtering for a time domain data acquisition application

I want to filter sensor signals for a data acquisition application on an ATmega microcontroller. The interesting parts of the signal are in the range 0-5Hz, and I'd like to leave these mostly ...
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164 views

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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73 views

Understanding IIR , Low Pass, High Pass, Chebyshev, Elliptic Filter? [closed]

I see these terms everyday in every lecture, I do read stuff from wikipedia, follow lecture notes, study solved exercises. All in all I do have a rough idea about these, I know a little from ...
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124 views

How to filter uniform noise in a microcontroller?

By uniform noise I mean a band of a fixed width, no spikes, etc. This has to be one of the simplest examples. I'm looking for the appropriate theoretical approach as much as something relatively ...
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87 views

First-order low pass filter with bounded derivative

Given a function $x(t)$ and a first order low-pass filter $\frac{dy}{dt} = \frac{1}{\alpha} (x(t) - y(t))$, is there a way to choose $\alpha$ analytically such that the derivative of $y(t)$ is ...
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82 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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1answer
56 views

What is a low-pass filter for a sequence of tuples?

I am currently reading SEGMENTATION AND RECOGNITION OF SYMBOLS WITHIN HANDWRITTEN MATHEMATICAL EXPRESSIONS. There is one sentence I don't understand: The preprocessing stage is subdivided into ...
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139 views

Implementations of Low-Pass Filter

I should say which of the filters from the following image implements an ideal low-pass filter with cutoff frequency $\frac{\pi}{4}$. In the picture, Sa is a zero insertion filter, which inserts a ...
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113 views

Audio distortion while implementing a low-pass filter

I attempted to implement a real-time audio filtering in a callback function using the simplest moving-average filter with coefficients [0.5 0.5] : ...
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1answer
109 views

How to remove historical values from exponential filter

Suppose I have two time series $A:=[0,0,0,4,5,6]$ and $B:=[1,2,3,4,5,6]$. I implement the following filter (with initial value at the first element): $$ f(t) = f(t-1) + \alpha*(f(t)-f(t-1))$$ with ...
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47 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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259 views

Difference between Equiripple & Least Squares design for FIR digital filters

For an efficient and optimized digital FIR filter design, there are two methods available broadly, Equiripple filter design & Least Squares filter design. A general method for designing a filter ...
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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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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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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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Filtering discrete data

Is is possible to use a digital filter (eg. Butterworth) for smoothing sensor data that is sampled at a non-constant rate? The time between two consecutive samples is between 12 to 40 ms.