Questions tagged [highpass-filter]

A high-pass filter is a device that passes high frequencies and attenuates frequencies lower than its cutoff frequency.

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What is the physical interpretation of Lowpass/Highpass filtering?

In Image/Signal processing context we have seen/we know that if there are say 4 samples and if we take an average of those 4 samples, then we say that the result sample is a low pass filtered output ...
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Is a high-passed signal the same as a signal minus a low-passed signal?

My question is, if I want to high-pass a signal, is it the same as low-passing a signal and subtracting it from the signal? Is it theoretically the same? Is it practically the same? I have searched (...
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Filtering of streaming audio

Given something like 103 data points ($N=103$), a DFT will give back 103 frequency values. Then to do something like filtering the high frequencies involves setting the high frequency values from the ...
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Is it correct to subtract a low-pass filtered signal from the original signal and use the result as a "high-pass"?

I am having a hard time trying to find documentation to implement band-pass or high-pass filter with python/scipy/numpy. I can easily create and apply a low-pass filter, though, so I ask: Would it ...
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complementary IIR filters

I would like a pair of complementary IIR filters (lowpass/highpass). By complementary, I mean, when the output from the two filters is summed, the original signal is recovered. I thought I could build ...
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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?
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Filter size vs. FFT size and Overlap add

First of all I would like to say that : I'm new to DSP and in a "learning curve" hence the "basicness" of my questions. I've read as many posts/articles as possible on the ...
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1answer
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How is the lowpass to bandpass transformation derived?

I'm using a lowpass to bandpass filter transformation: $$ s \leftarrow Q \left( \frac{s}{\omega_0} + \frac{\omega_0}{s} \right) $$ Based on the wiki article: http://en.wikipedia.org/wiki/...
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Is the Sobel filter a high pass filter, and if not, what is the difference between them?

I am an artist with an interest in signal processing. I realize that maybe this question very basic, but the web banner on the frontpage says "anyone can ask", so I assume that means beginners too. ...
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Designing High Pass Filter to Remove DC Offset from a Signal

I want to design a high pass filter (f0*S/1+f0*S) in order to remove the dc offset from a signal ? (i.e. how to choose the frequency f0). Thanks, Hacene Ps : the filter is for MATLAB implementation, ...
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An Intuitive Way to Understand the Sharpen Convolution Filter in Image Processing

Can someone explain sharpen in a non-technical way. So, I don't mean that you need to multiply every pixel with 5 and subtract it with the pixel left, under, above and right.
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How to Classify a Kernel as Low Pass Filter (LPF) or High Pass Filter (HPF)? How to Transform an LPF Kernel into HPF Kernel?

The filter impulse response is [1/9 1/9 1/9;1/9 1/9 1/9;1/9 1/9 1/9]. how do i determine whether it is an Low pass filter or a high pass filter. If this is a low pass filter how do i convert it to a ...
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Understanding the attenuation of a signal

I have been told that the signal in the graph below was obtained by passing a seismogram through a high-pass filter to obtain the high frequency-small amplitude waves common in tremors far from the ...
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How to Classify Image Filter as Low Pass Filter (LPF) or High Pass Filter (HPF)?

I am currently reading on the topics of image filtering and convolution kernels. While the process of convolution is clear to me, I do not understand, how one arrives at the statement, that a certain ...
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Analyzing movement of fringes

I have taken a series of images of a fringe pattern at regular time intervals. This fringes are generated by shining a laser beam onto the CCD camera. The laser goes through a lot of optics, which is ...
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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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Negative values from High Pass filtering

I come from Fluid Mechanics domain so pardon me for asking a naive and fundamental question. I am trying to perform high pass filtering on a set of positive real numbers (~Energy) using FFT. However,...
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3answers
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LPF and HPF Confusion - Rectangular and Circular Cut-Offs

Interpreting some homework, I'm a little confused on what it's asking for. I'm asked to filter in the frequency domain (easy enough, just a fft2 and ifft2 when I'm done) a 256x256 8bit grayscale tiff ...
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Why is Prewitt filter High Pass

Prewitt filters are popular filters in image processing for edge detection http://en.wikipedia.org/wiki/Prewitt_operator Can anyone give a proof on why Perwitt and other edge detecting filters are ...
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High / Low Pass Filters from Zero

I everyone, I'm a computer scientist but not from the signal processing community. I want to implement a real time digital low pass filter (to begin with) for a sound processing application. I've ...
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Removal of noise from vibration recordings

Problem I am analyzing accelerometer recordings that are contaminated by 'spikes' caused by issues in the digital circuitry. The spikes are problematic, because I wish to determine the peak-amplitude ...
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1answer
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Should I Use a High Pass Filter (HPF) or Low Pass Filter (LPF) to Enhance the Features for Image Splicing Detection?

I'm recently learning image splicing detection. I've already known image splicing can bring some abrupt changes to an image,which generate the sharp edges.And sharp edges correspond to high frequency. ...
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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?
3
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1answer
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Anybody with experience with online double integration of acceleration?

I've found good literature for offline proccesses, and I've gotten good results. However, when it comes to online applications, I've found nothing good. Applying any filter without a linear phase ...
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1answer
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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 ...
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Why is the frequency response different based on the amplitude of the impulse I feed into the filter?

I am working on a 2-pole IIR high-pass filter. The filter is fixed point and it is causing me some issues. I believe I'm just misunderstanding something. I am implementing everything in Octave for ...
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How do I design a speed-efficient high-pass filter to replace slow polynomial filter? [closed]

I have the recorded membrane potential of a neuron, and I want to get a more even baseline by removing certain slow changes from the signal (see figure). The best way to achieve this thus far has been ...
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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 ...
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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 ...
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What is the name of these simple filter algorithms?

I found some snippets of code on the internet that are really simple signal filters. Unfortunately there wasn't much info to back it up. Using Google I've found similar code, but none of it backed up ...
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Mathematical Proof of Complementary Filter?

Having found some unofficial sources on Complementary Filter (Thousand Thoughts Sensor Fusion and The Balance Filter by Shane Colton), I wish to work out its rigorous mathematical proof. The ...
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Filter design - Rules of thumb regarding ratio of sampling and stop/pass frequency

The issue: I have a signal in the time domain sampled at 51.2KHz. I want to apply a highpass filter with a pass frequency of 20 Hz. The problem: Using Matlab to do that, the design of the filter ...
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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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1answer
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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 ...
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1answer
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How to convert a low-pass Gaussian filter to a high pass filter

I have the following code for a applying a Gaussian filter to an image. From what I understand this is a low pass filter. Now I have to convert this into a high-pass filter, and from what we were told ...
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2answers
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Applying a high-pass filter on constant signal

I recently implemented a Butterworth high-pass filter (2nd order). Everything seems to work fine, except that I have a question when applying such a filter to a constant signal. As there are no high-...
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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 ...
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2answers
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How to Design a Pre-emphasis filter knowing the gain, a zero and a pole?

I am simulating an FM radio signal in order to use it as a waveform in passive radar; for this purpose I'm following an article: Analysis and Emulation of FM Radio Signals for Passive Radar In a ...
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1answer
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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 ...
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1answer
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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 : ...
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1answer
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Are there DC removal techniques that do not introduce a filtering transient?

I have an application in which I need to remove DC components from a sampled signal in real time (basically the same constraints of ECG, but it has nothing to do with the brain). My measured signal in ...
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1answer
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Designing high-pass filters using impulse invariance

One of the main disadvantages of realizing digital filters using impulse invariance is aliasing. According to the Nyquist sampling criterion, in order for the frequency response of the digital filter ...
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Real-time FIR filtering on time domain

My previous question wasn't clear. So I thought it'll be good idea to repost with more details. I've designed a 100th order windowed highpass FIR filter with 3Hz cutoff frequency for my ADC datas ...
2
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1answer
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is any filter whose impulse response has a discontinuity in the first derivative fundamentally high-pass?

a triangular (bartlett) window has a kink (discontinuity in first derivative). thinking in the continuous (not discrete) case, my intuition is that the fourier transform of any window with a kink ...
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1answer
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How to determine the parameter of a Complementary Filter?

I know that the Complementary Filter has the functions of both LPF and HPF. But I think my understanding on the principal behind it is still unclear. I am quite new on digital signal processing, and ...
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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 ...
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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 ...
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2answers
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highpass filter design in Matlab

I hope to design 1st order highpass filter from transfer function. In the example of 1st order lowpass filter, I first get the coefficients of numerator and denominator in the variable 'b' and 'a'. In ...
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1answer
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Difference equation with complex zero

Let's assume I have the following transfer function: $$ H(z)=\frac{z-\left(\frac{1}{\sqrt{2}}+i \cdot \frac{1}{\sqrt{2}}\right)}{z} $$ It looks like a first order highpass-filter with a complex zero ...
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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 ...