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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Difference between DWT based reconstruction and MRA components

I recently learnt basics of wavelet transform and multi-resolution analysis. I'm analyzing a signal with 14,000 data points. I wish to extract low-frequency features of this signal, and for that, I'm ...
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s to z domain transformation

I have $2^{nd}$ order bessel filter transfer function. I want to model this analog bessel filter in FPGA. For this I need its digital or discrete form. I am trying to get digital filter's coefficients ...
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Step response of IIR lowpass filter using GNU octave

Some years ago, I had a little tool in FORTRAN and GNUplot output, which was able to plot the step response of an IIR lowpass filter, starting which the location of the poles. Now, this tool is lost ...
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Flatten noise floor of spectrum by reference/dark measurement

I'm currently stuck with a problem and would appreciate any input or guidance in this regard. Background information In a laser experiment, an amplitude signal in volts and a position signal are ...
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Best Methods for Interpolating Short Non-Periodic Bandlimited Signals

I need advice on interpolating a very short (N < 10) discrete, bandlimited signal that is sampled above the Nyquist rate. I understand that technically finite length signals have infinite bandwidth,...
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Downconversion and CFO estimation after package detection

I'm currently working on generating a function to simulate a passband transmission. In my simulation, I assume that the received signal is twice of my transmitted signal (without adding any noise and ...
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Implementing a Butterworth low-pass filter in Python without knowing the order

I am relatively inexperienced with respect to lowpass filters, but I am trying to replicate parts of this paper, which deals with the processing of 3D accelerometer and 3D gyroscope data, both from ...
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25Hz low-pass FIR filter for 96kHz high-quality audio

I am evaluating how to implement 25Hz low-pass / 25Hz high-pass filter with flat phase response (i.e. FIR). Apparently straightforward FIR filter would require insane number of taps (>8192) which ...
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Low pass Thiran filter difference equation in Python

I'm attempting to build a time domain low-pass Thiran filter (in Python if that is relevant) based on the original article: https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=1083363&tag=...
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Software based energy meter

I have been implementing a software energy meter. In other words my software has to integrate immediate electrical power over time. The immediate electrical power is calculated based on following ...
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Why does the frequency sampling method for FIR filter design operate in this manner?

I'm studying FIR filter design and it's time for the frequency sampling method, my teacher said that to use this method you need to follow the following steps: Sample the periodic frequency response ...
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1 vote
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Signal recovery is based on the development of the Shannon sampling theorem?

One of the earliest extensions of this theorem was stated by Shannon himself in his 1949 paper, which says that if $x(t)$ and its first $(M - 1)$ derivatives are available, then uniformly spaced ...
103 views

White noise vs low-pass filters

It seems common that people assume white (aka Gaussian) additive noise. Yet it is also common to use low-pass filters to remove noise. But white noise shows up equally on all frequency bands. So it ...
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Determine the transfer function for the Butterworth bandpass filter? (At the Transfer Function Factoring and Sp Substitution stage) The Parameter $$a_{pass} = - 1dB$$ $$a_{stop} = - 20dB$$ $$f_{pass1} ... 3 votes 2 answers 443 views First order filters in Direct Form I (RBJ Cookbook) I've implemented second order biquad filters using the famous RBJ Cookbook. I also want to implement first order lowpass and highpass filters. I was hoping to use the same code, so I need to define ... 0 votes 1 answer 49 views Minimum amount of data needed for low pass filter on real time sensor data I need to apply a low pass filter up to a period of 10 hours to my data. My sensor has a sampling rate of 1 sample every 5 minutes. I need to know how much data I at least need to have to be allowed ... • 1 0 votes 1 answer 67 views Calculating stopband cut-off frequency and stopband attenuation for FIR lowpass window filter I am aiming to create a digital windowing FIR filter on MATLAB and have been given specs such as a: sampling frequency of 360Hz maximum filter order of 5 cut-off frequency of 98Hz/ 1.710rad/sample (... 0 votes 1 answer 59 views Lowpass Filter to Average sinusoid signal How to get an average of a sinusoidal signal? The frequency of a signal is 50 Hz and could have harmonics, i.e. high THD. I tried to use exponential moving average with low cut-off frequency (about 1.... 0 votes 1 answer 274 views Difference between simple 1st order low-pass filter equations While reading about 1st order low pass discrete implementations I found out, the following 2 equations achieve similar results, but apparently not identical, but I thought they had the same origin. ... • 167 1 vote 1 answer 248 views Why is there a phasor in the transfer function of an ideal LPF? I'm learning about Low Pass Filters. My professor said the following is the transfer function of an ideal LPF:$$H_{LPF}(f) = G\Pi\left(\frac{f}{2B_{pass}}\right) e^{-j2\pi ft_0}$$However, i don't ... • 11 0 votes 1 answer 45 views Quasi-static-detector operation principle Im currently working on a project to get navigation information of a robot from Data-Fusion through different IMUs. First step is to make a calibration and I picked a method where I need to detect ... 3 votes 2 answers 764 views Confusion on when a filter is considered band-pass As part of an assignment, I was given a filter with a specific set of poles and zeros, namely poles at 0.51 \pm 0.68i and zeroes at 1.5 and −0.7. This part of the assignment is titled as "... • 139 0 votes 0 answers 57 views Matlab FDAtool. Generating integer filter coefficients without gain I use the FDAtool package to work with digital filters. I have always worked with coefficients in float format. I noticed that FDAtool always makes the b coefficients as integers. It also always adds ... • 105 2 votes 1 answer 252 views group delay of Bessel filters Wikipedia states that Bessel filters have a group delay within passband of 1/\omega_0. While the inverse relationship to knee frequency makes sense, it ignores the effect the filter order has on the ... • 366 0 votes 0 answers 48 views I'm struggling to understand the FIR Filter and its application I'm new to GNU Radio, and I was watching this video However, I didn't quite understand the purpose of the FIR Filter. I know what decimation or downsampling is because I have the book "Digital ... • 15 4 votes 1 answer 73 views Ratio of aliased to desired energy of a sampled signal In this article "Sampling: What Nyquist Didn't Say, and What to Do About It" from Wescott, the author shows in Figure 6, the plot of the frequency spectrum of a signal which goes through a ... 4 votes 1 answer 239 views Applying Lowpass filter on a signal in time domain gives ringing artifacts - how to get rid of them EDITED AND UPDATED: My signal is an impulse response. In the following figure: The frequency spectrum of the impulse response (original signal) is shown by blue line. The original signal is ... 2 votes 0 answers 54 views Trying to understand scipy.signal.kaiserord I am trying to understand scipy.signal.kaiserord example. The example says We will use the Kaiser window method to design a lowpass FIR filter for a signal that is sampled at 1000 Hz. We want at ... • 131 0 votes 1 answer 90 views Theory behind transfer function transforms of the type H(s) \rightarrow H(f(s)) My brother wanted me to derive a high-pass version of a Butterworth low-pass filter. I found that the transform H \left( s \right) \rightarrow H \left( j - j s \right) does the thing, but I can't ... 1 vote 1 answer 311 views How to design low pass filter for this case From control systems perspective, I have two subsystems that are connected in a cascade structure. An outer loop represents a joystick that provides position that runs at 1kHz and an inner loop ... • 357 3 votes 2 answers 240 views Demodulation + LPF gives derivative of modulated signal I'm new in this community and I hope it is the right place to post my question. Unfortunately, signal processing and electronics in general are not my fields, so I'm sorry if the question is trivial. ... • 133 10 votes 2 answers 1k views What is the name of a low-pass filter that tracks rate of change? When applying a low-pass filter to a constantly changing signal, there will be a lag between the actual value and the filtered value. For example, if f(x) = x, the ... • 878 0 votes 0 answers 186 views Type 1 Chebyshev 3rd Order Lowpass Filter I'm trying to implement a 3rd order Type 1 Chebyshev digital lowpass filter in C++. I've been having a lot of problems and I'm not sure why. I can plot the transfer function in MATLAB and see that it ... 0 votes 1 answer 105 views Lowpass filter to downsample data I have some data that is sampled at a certain rate (16384Hz). I am only interested in the 10-30Hz region, so I want to downsample the data. My idea to do this goes as follows: I apply some kind of ... 1 vote 0 answers 209 views Is lock-in amplifier a correct approach? I have a noisy signal which is the voltage output from a photodetector circuit. I have researched about extracting signals, and found that lock-in amplifiers are one of the main approaches for the ... • 21 1 vote 1 answer 364 views Lock-in Amplifier: How to improve the output of lock in amplifier? I tried to extract a pure signal from the noisy signal using a lock-in amplifier with the help of python code. The output is from a photodetector circuit. These are the reference signal, expected ... • 21 2 votes 1 answer 205 views Low-pass filtering a clipped signal In order to downsample a signal sampled at 48KHz, I implemented an anti-aliasing filter. An Elliptic LPF with a cutoff at 16KHz and order of 10. Everything looks OK until the input to this filter is a ... • 23 2 votes 1 answer 128 views In the RMS bandwidth equation, why do we have the energy of the signal in the denominator? In the following equation:$$B_{\rm rms}^2 = \frac{\displaystyle\int_{-\infty}^\infty f^2\lvert G(f)\rvert^2df}{\displaystyle\int_{-\infty}^\infty \lvert G(f)\rvert^2df}. It is not clear why do we ...
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I want to mention upfront that I'm not very experienced in this field. I have a signal $u(k)$ that I get from a black box simulation (sampled irregularly). The signal looks like this: The blue signal ...
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Low-pass Filter with constant phase response

I would like to design (e.g. in GNU-radio) a low-pass filter where up to the cut-off frequency the phase-response is constant (I do not mean a "linear-phase response"). The rationale is to ...
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Applying filters in the frequency domain

I have data in the frequency domain. How can I apply the low pass filter such that it still removes the high frequency information?
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Demonstrating linear filters on daily weather data

I have daily temperature data from some place on Earth. Apparently, the sampling frequency f_s = 1/day. I would like to use these data to demonstrate (visually) the use of low-pass, high-pass, and ...
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What are the tradeoffs between shifting a lowpass FIR filter vs using a bandpass FIR filter?

Is there a difference between shifting a lowpass FIR filter to an arbitrary frequency offset versus creating an equivalent bandpass filter, such that the passband and cutoff frequencies are identical? ...
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Which audio smoothing algorithm has the lowest latency?

I am working on an audio smoothing project. My inputs are from a record scratching MIDI controller, and I am trying to produce a smooth output (the raw data creates noisy audio). I'm using a simple ...
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Relation between discrete wavelet transform and filter banks

I have approached wavelet transformation from a projection perspective. Specifically, we can show for a certain class of functions (in the continuous setting) that they can be written in terms of a ...
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How to measure aliasing?

Aliasing is bad, and we want good filters when downsampling. While what qualifies as aliasing is well-defined mathematically, and we can manually design filters with various tradeoffs, how do we ...
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NUFFT/FFT interpretation

I know this has been covered thousands of times on the internet, but I'm still struggling with it. My end goal is to cancel out the noise in an Inertial Measurement Unit chip readings so I can double-...
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Why does the discrete bode plot look like the following and if possible explain the black vertical line at the end for an averaging filter

Why in the attached image for a simple 3 point moving average that has been converted into a TF (z domain) is there a wired dip? It seems that when I change the sampling time, the dip shifts to the ...
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Let's say I have a discrete-time signal $y[n]$ that is passed through an Ideal Lowpass Filter (impulse response $h[n]$) to get $y_1[n]$. The filter has cutoff frequencies at $\pm \pi/N$ rad. Now this \$...