Questions tagged [highpass-filter]
A high-pass filter is a device that passes high frequencies and attenuates frequencies lower than its cutoff frequency.
140
questions
0
votes
0
answers
42
views
High Pass Filter for Image using C++ and Python
I was assigned to optimize the HPF using C++. Fyi, the original image is 512x512.
By getting the .dat file that is produced by using Python script, I applied a 5x5 HPF on it with 2 zero-pad with ...
1
vote
1
answer
53
views
How to detect and distinguish oscillations in a signal?
I would like to detect oscillations in a signal $s$ and determine the nature of the oscillations, i.e. whether they are high-frequency oscillations or not.
Edit : An example of $s$ is given below :
...
- 15
0
votes
1
answer
56
views
How can the detail coefficients in discrete wavelet transform (DWT) be downsampled?
This question is asked with reference to this paragraph
For the high-pass filter, the frequency content lies in the range $\frac{F_s}{4} \rightarrow \frac{F_s}{2}$. There is no content in the range $...
- 1
0
votes
0
answers
53
views
Why is there coherence below the cutoff frequency of two high-pass filtered signals?
I record surface EMG signals from two muscles at 1500 Hz. The following preprocessing steps are performed using basic MATLAB commands.
First, I decimate both signals to 500 Hz (Lowpass filtering ...
- 1
0
votes
1
answer
108
views
How to apply Butterworth high pass filter in the frequency domain?
I have a time series of measurements which I want to high pass with Butterworth filter.
Python scipy package has a built in function for Butterworth filter (signal.butter) and I know how to apply it ...
- 3
1
vote
1
answer
122
views
Implementing basic high pass filter using difference equation
For the following signal, I am trying to remove the gradual positive drift but retain the spikes using a high pass filter.
I am aware that I can use implement a high pass filter using difference ...
- 111
0
votes
1
answer
35
views
strange waveform after highness FIR filter
I was trying to apply FIR filter on the ECG signal: a bandstop for 45-55 Hz for noise removal and a highpass filter for moving baseline wander. But after that, the ECG signal show strange waveform at ...
- 3
1
vote
1
answer
41
views
analog filter magnitude flatness problem
I have designed an analog filter that includes a high pass filter with a cut-off frequency of 5 Hz and a notch filter with a cut-off frequency of 50 Hz.
I want to sample the output signal of the ...
- 11
0
votes
2
answers
93
views
IIR Filter Stability
I have designed an inverse IIR high pass filter by inverting its transfer function B(z)/A(z) to A(z)/B(z). However, the inverse filter has a pole at z=-1.
Is this filter considered stable (marginally ...
0
votes
0
answers
82
views
How to enhance thermogram image in grayscale?
I'm trying to do some image processing to improve the image below but I'm having some trouble. I already tried to do histogram equalization followed by laplace sharpening, I tried to implement a ...
1
vote
2
answers
209
views
Differences in transforming a sinc FIR filter from lowpass to highpass using spectral inversion and spectral reversal
I have designed a lowpass sinc 1023 tap FIR filter with a Blackman window and this works fine.
I understand there are then two ways to transform this lowpass filter to a highpass one.
One is spectral ...
- 113
0
votes
1
answer
43
views
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 ...
- 1
0
votes
2
answers
320
views
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 ...
- 299
0
votes
2
answers
1k
views
How to implement a high pass filter digitally to remove the dc offset from sensor data
I'm trying to implement a high pass filter on sensor data to remove the dc offset. I'm aware I can subtract the mean of the data but I'm looking for a frequency domain approach. I've used the matlab's ...
0
votes
1
answer
1k
views
RC high pass filter differential equation
I have the question to derive:
$$RC \frac{dy(t)}{dt} + y(t) = RC \frac{dx(t)}{dt}$$
which describes a high pass filter or $CR$ circuit with $x(t)$ the input and $y(t)$ the output.
I am really ...
1
vote
0
answers
57
views
High pass biquad cascade transposed direct form II low frequency accuracy
I'm quite new to DSP and I'm trying to implement high pass biquad cascade in transposed direct form II. Currently my implementation has very poor accuracy at cutoff frequencies that are less than 5kHz ...
- 11
1
vote
1
answer
84
views
Highpass filter design that is better than the Moving Difference filter
The question is actually from the problem set 1.3 of the "Wavelets and Filter Banks" book (authors Nguyen/Strang).
Problem 4: Invent a Highpass filter K with 3 or 4 taps (coefficients) that ...
- 167
2
votes
1
answer
1k
views
Low frequency (1Hz) High pass filter
I am trying to get a useable wave from a pulse oximeter, but there is a pesky DC bias that keeps changing every now and then, so I cannot simply subtract the DC bias from it and get useable results ...
0
votes
0
answers
81
views
Bandpass filter vs sequential high and lowpass filter in Matlab: weird difference
I am trying to bandpass a neural signal acquired at 20kHz between 0.5 and 100 Hz. I have tried to do it in two ways. The first way is to sequentially highpass and lowpass the signal and the second one ...
7
votes
3
answers
703
views
Is there an adjective describing a filter with kernel that has zero mean?
A linear filter with a kernel that has zero mean could be thought of as a "DC-rejecting" filter. Is there a better or more commonly used adjective for such a filter?
- 173
0
votes
1
answer
101
views
Why use both a high pass and a low pass filter in a Butterworth implementation for noise reduction?
I am a new to audio processing . I want to develop an application that reduces audio noise using a Butterworth filter. I found some existing code doing this, but I still do not understand the use of ...
3
votes
1
answer
79
views
The magnitude spectrum of a sharpening filter
I'm trying to derive an expression for the magnitude spectrum of the following sharpening filter.
$$
g(m,n) = \delta(m,n)+\lambda (\delta(m,n) - h(m,n))
$$
where $\lambda$ is some positive constant ...
0
votes
1
answer
145
views
Simulate butterworth filter with initial condition of state vector in R
I'm working in R with the packages signal and control (don't know wether these are even the best for my use case).
I have a high ...
- 101
5
votes
1
answer
1k
views
Is the Laplacian Filter an High Pass Filter (HPF)?
Is this kernel name as mean difference kernel or Laplacian filter?
Is mean difference just a method?
- 53
1
vote
1
answer
143
views
Downsampling after a highpass filter
Question: The following sentence is not clear to me (especially why down-shift occurs). Could someone explain it please?
On the other hand, downsampling the output of the highpass filter down-shifts ...
- 325
0
votes
1
answer
74
views
High pass filter not attenuating signal at start of input
I have implemented digital high pass filter with below specs:
Sampling frequency = 5333 Hz
Cutoff frequency = 10 Hz
Order = 3
We are facing problem like below:
As ...
0
votes
1
answer
125
views
What is the purpose of the recurrence relation in low and high pass (audio) filters?
Newbie here. I'm familiar with time and frequency domains from math. I think I understand what low and high pass filters do, sonically. But digging into an implementation of ...
- 103
0
votes
1
answer
451
views
Remove audio signal component under certain frequency in python
I want to remove all signal components under 10KHz in one audio file. Below is my code
...
0
votes
0
answers
41
views
Problem with implementing DC offset for streaming data
I am new to the DSP world. I'm trying to run a raw input signal through a LPF, remove any DC offset, amplify the signal, and then decode the signal. The problem with my code seems to be the ...
- 1
2
votes
1
answer
1k
views
Are high pass/low pass filters FIR filters?
I am trying to understand the basic categories of DSP filters, and it seems that the two main groups are FIR and IIR, however I'm not sure how to categorize high pass, low pass, band pass, and band ...
- 45
1
vote
1
answer
112
views
Highpass filter square wave
Generated a 1kHz square wave in Audacity and normalized it to 0dB (fs = 44100Hz):
Added a 24dB/oct high pass filter (std Audacity plug-in), cutoff frequency set to 100Hz. Result:
Zoomed version:
...
- 617
3
votes
2
answers
2k
views
3 dB cut-off frequency of first-order IIR high-pass filter
As descipbed in this great answer (thank you Matt L.), the suggested exact formula was very precise.
I need a first order high-pass with similar precision.
EDIT: (clarification)
The low-pass filter ...
- 63
2
votes
2
answers
387
views
Calculating the 3dB frequency of an nth order low pass filter and nth order high pass filter
I am using the 6th order high pass filter in the C code. And the cut-off frequency selected for it is 150 Hz and the sampling frequency being used is 32000Hz. Now, I want to calculate the 3 dB ...
- 49
1
vote
0
answers
24
views
Correct way to build a basic filter bank (ie. for simple multiband audio processing)?
I need to build a filter bank for multiband processing. Last time I tried I was just starting at coding/DSP so I failed and didn't get a flat spectrum out of it. I just want to know the basic ...
- 429
0
votes
2
answers
1k
views
Ideal high pass filter for discrete signal
there. I currently get stuck on a question. I was asking to find an inverse discrete-time Fourier transform for the ideal high pass filter.
Here is the question
It is getting more confused after I ...
- 3
0
votes
0
answers
33
views
Adjusting coefficients of a LP and HP filter for a new sampling rate
I am pretty new to DSP and try to undertand some concepts and the relations between them.
I currently learning about the Pan-Tompkins algorithm and trying to recreate it in Matlab (Pan–Tompkins ...
- 1
-1
votes
1
answer
71
views
Correct signal analysis flow (Wind Turbine vibration)?
I have vibration data from WT (gearbox) sampled at 25.6 kHz. From a previous post I received a lot of good recommendation.
What I am trying to do:
Find early stage bearing faults by using an ...
- 159
0
votes
1
answer
520
views
FIR Filter - Low Pass Filter coefficients to High Pass filter coefficients
I need to convert this 12 Tap Low Pass Filter to a High Pass Filter.
The coefficients of the Low Pass Filter are as follows:
...
1
vote
2
answers
189
views
Envelope analyis basic question
I have a vibration signal sampled at 25.6 kHz, and I want to perform Envelope Analysis on it.
"Vibration-Based Condition Monitoring of Wind Turbines" by T. Barszcz has the following figure:
I ...
- 159
-1
votes
1
answer
25
views
New magnitude frequency after apply highpass butterworth filter
I want to use high pass filter to filter frequency less than 100Hz. I use this code in python.
...
0
votes
0
answers
97
views
FFT response for noisy signal, averaging the response and
I try to analyze a system's state with acceleration sensors by measuring the frequencies and amplitudes.
Since a cheap sensor is used, I have a noisy signal in the beginning (up to 40Hz - see below). ...
- 1
2
votes
2
answers
198
views
Why is my signal attenuated after applying a HighPass-filter?
I am new to DSP, but I've been attempting apply a butterworth high-pass filter on a 1D array (Values peeking at 300~) to eliminate any noise, yet when applying a high pass filter, I'm ending up with ...
- 41
2
votes
1
answer
2k
views
Applying a 2D band pass filter (Butterworth ?) to an array with NaNs
I am trying to filter out the low frequencies of an array looking like this :
For now, I am taking transects of this array and applying a 1D - butterworth band pass filter :
...
- 153
1
vote
2
answers
286
views
How to visualize high-pass filtered images?
When I try visualizing a high-pass filtered image, all I see is gray, similar to the middle subfigure in the attached figure from a related paper. The authors claim they normalize the image to have ...
- 165
2
votes
0
answers
49
views
Check work: Expression for 3dB bandwidth for frequency response of high - pass filter having just one pole
The input output relationship is given:
$y[n]=ay[n-1]+bx[n]$
$-1<a<0$
I applied z-transform to get the transfer function :
$$H(z)=\frac{b}{1-az^{-1}}$$
Since $-1<a<0$, the maximum ...
- 199
0
votes
1
answer
351
views
Biquad high-pass filter not working as expected
I'm trying to implement a high-pass filter using the the coefficients described in RBJ's well-known EQ cookbook (see https://www.w3.org/TR/audio-eq-cookbook/).
However, when I run white noise through ...
0
votes
1
answer
79
views
Attenuate the low frequencies in a speech wave
I am designing an FIR filter to attenuate the frequencies below 300Hz. I designed the filter using the ...
- 3
0
votes
1
answer
3k
views
Poles and zeros map, High pass filter
Given the following poles and zeros map I have to identify qualitatively, which filter type is represented (Low-Pass, High-Pass, ...). In the solution it says, that this is a high pass filter.
...
- 3
3
votes
2
answers
335
views
What impact have different types of border-handling on high pass or low pass filtering?
When high or low pass filters are being applied to an (grayscale) image, the borders need to be handled separately. They could be filled with 0's or 255's (b/w), repeat the nearest pixel value, or ...
- 131
1
vote
1
answer
109
views
FIR filter not eliminating out of band noise?
I have a simple FIR filter that should eliminate all lower frequencies:
...
