Questions tagged [bandpass]
A band-pass filter is a device that passes frequencies within a certain range and rejects (attenuates) frequencies outside that range.
300 questions
27
votes
5
answers
4k
views
When is aliasing a good thing?
In Hamming's book, The Art of Doing Science and Engineering, he relates the following story:
A group at Naval Postgraduate School was modulating a very high
frequency signal down to where they ...
- 4,907
18
votes
2
answers
32k
views
How do I manually plot the frequency response of a bandpass Butterworth filter in MATLAB without freqz function?
I have code like below that applies a bandpass filter onto a signal. I am quite a noob at DSP and I want to understand what is going on behind the scenes before I proceed.
To do this, I want to know ...
- 283
14
votes
2
answers
2k
views
What bandpass filter design will yield the shortest impulse response?
Designing a simple 2nd order IIR bandpass Buterworth filter with a centre frequency of 500 Hz and a 1 octave bandwidth gives me the following frequency response ...
Now, if I take the impulse ...
- 1,513
10
votes
3
answers
7k
views
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 ...
- 1,097
10
votes
2
answers
2k
views
Understanding a Bainter Circuit (chebychev filter)
As part of a class in Signal Processing, I am building a 3rd order Chebychev band reject filter. We implement this by using three cascading Bainter circuits. Although not part of the class, I have a ...
- 285
8
votes
3
answers
3k
views
What is the ideal FIR length, given a specific pulse length?
I am trying to ascertain what the 'ideal' FIR filter length should be, given the pulse length $T_p$ of a windowed sinusoid in noise that I seek to filter.
As parameters into an FIR filter that I ...
- 9,897
7
votes
3
answers
925
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?
- 193
7
votes
1
answer
14k
views
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/...
- 916
7
votes
2
answers
1k
views
How do I apply a Chebishev filter?
I read a paper about a brain-computer interface. In this paper the authors reported "each signal has been filtered with an 8-order band-pass Chebishev Type I filter which cut-off frequencies are 0.1 ...
- 175
7
votes
1
answer
6k
views
How to test digital filters?
First the question(s):
How should I write unit tests for a digital filter (band-pass/band-stop) in software? What should I be testing? Is there any sort of canonical test suite for filtering?
How to ...
- 1,097
6
votes
2
answers
2k
views
Frequency Domain Filtering
Can you create a zero phase IIR filter by transforming its impulse response into frequency domain and only taking the magnitude of that frequency repsone?
I have seen this in an open source project ...
- 407
6
votes
2
answers
11k
views
Bandpass filters with python for low frequencies
I have a signal, sampled at 1 kHz, that I would like to analyze in third octave bands. For that purpose I defined Butterworth filters with proportional bandwidth. This works well for higher ...
- 223
6
votes
2
answers
3k
views
What is the right way to extract particular frequency phase information from FFT?
Signals acquisition:
Two proximity sensors are positioned Orthogonal to each other. These would be measuring the vibrations of a rotating shaft.
Problem:
Each of these 2 signals has two dominant ...
- 115
5
votes
2
answers
5k
views
Which order to perform downsampling and filtering?
I have EEG data recorded with 128Hz sampling rate.
As my goal is to reduce the amount of data (and maybe noise), I want to downsample the data to 64Hz (I am only interested in range 0.5 - 30Hz).
I ...
- 239
5
votes
4
answers
379
views
Bandpass Stationary Stochastic Process
I was following this interesting post by a new user Rubem Pacelli and got stuck at Proakis' referenced definition (see Section 4-1-4 starting on page 159 here). The math, all repeated further below, ...
- 55k
5
votes
2
answers
4k
views
How can I break a filter down into second order sections?
This is a follow-up question of How do I apply a Chebishev filter? I designed a filter in Scipy:
...
- 175
5
votes
1
answer
1k
views
Derivation of the lowpass to bandpass transformation
I have a basic question.
The "well known" lowpass to bandpass transformation is
$$
s \longmapsto \frac{\bar{s}^2 + \omega_1\omega_2}{\bar{s}(\omega_1 - \omega_2)},
$$
which gives a bandpass ...
- 153
5
votes
2
answers
10k
views
Low pass vs band pass filter
I've been reading some EEG papers where the authors use a bandpass filter at, say, 1Hz and 30Hz. I've also seen some accelerometer papers where they bandpass at 0.5Hz and 10Hz
What is the difference ...
- 315
5
votes
2
answers
3k
views
How to determine if a filter is bandpass/stopband from its pole-zero diagram in z-domain
How can we determine if a filter is bandpass or stopband, just by looking at its pole-zero diagram in z-domain?
For exmaple, if we have a system with third-order pole at the origin and a zero on the ...
- 467
4
votes
3
answers
2k
views
Filter odd or even harmonics with notch or inverse notch filter
I have a signal containing a 200Hz sine wave and it's odd and even harmonics (no other frequencies or disturbing signals are contained).
What I'm looking for is a kind of filter which is able to ...
- 53
4
votes
3
answers
2k
views
Matlab `filtfilt` provides excessive transient
I observed that filtfilt suffers from an undesired behavior when I provide IIR bandpass filters having steep transition bands. Specifically, the output signal exhibits excessive transient response; ...
- 41
4
votes
2
answers
3k
views
Energy in baseband and bandpass signal
Is there any difference in energy content of baseband and bandpass signals? When we see their representation in frequency domain, it looks like a bandpass signal has double the energy content compared ...
- 41
4
votes
1
answer
448
views
Problems with implementation of a band-stop filter on an MCU (dsPIC) using fixed-point arithmetic
I'm trying to implement a band-stop (notch) filter on a microcontroller dsPIC33EP64GS506 to filter out a $100\textrm{ Hz}$ component from an input signal. The ...
- 173
4
votes
1
answer
1k
views
Bandpass general equation to difference equation
I know this is a very basic question and I am coming out from a quarter of DSP. I want to create a function in Java which can taken in two parameters, either ...
- 143
4
votes
3
answers
3k
views
What is the underlying concept behind Bandpass sampling?
Can you suggest me some books/webpages on Bandpass sampling?
I undestand that if the signal is restricted between $f_L$ and $f_H$, then the minimum bandwidth required is $2(f_H - f_L)$. But say the ...
4
votes
1
answer
3k
views
In What Way Is the Difference of Gaussian (DoG) More Tunable than the Laplacian of Gaussian (LoG)?
I was reading through this post "What is the difference between Difference of Gaussian, Laplace of Gaussian, and Mexican Hat wavelet?" and noted in Chris Luengo's answer that he mentioned that the ...
4
votes
1
answer
2k
views
Online filter for EEG
My goal is to build a real-time filter for EEG data. The data are being recorded in 512Hz and I wish to filter it (in a real-time, from 0.5Hz to 30Hz in the most optimal way).
Unfortunately I'm not ...
- 265
4
votes
1
answer
307
views
basic bandpass filter
I am attempting to implement a basic bandpass filter but the center frequency of my filter seems to be irrelevant as I can change it all I want but it has no effect on the filter.
where am I going ...
- 43
4
votes
2
answers
84
views
Is there any solution for this bandpass feedback overload problem (besides increasing sample rate)?
I have been working on a physical modeling string (eg. guitar/piano) synthesizer which is nearing completion. It is based on a modal array of resonant bandpasses, where each bandpass is set by Q and ...
- 543
4
votes
3
answers
2k
views
All-pass filters to remedy group delay
I would like to sum a filterbank made of bandpass butterworth filters to reconstruct an audio signal. Given group delays for each channel shown in the following plot . . .
How would I go about ...
- 1,513
3
votes
2
answers
2k
views
Numerically Stable IIR filter
I am making an IIR Filter and I am running into problems with stability with higher orders. The values go off to infinity as soon as it starts.
So far, I've been using MATLAB to generate my filters ...
- 33
3
votes
2
answers
773
views
SOS-matrices' order does not correspond to given parameter when designing bandpass with scipy.signal.butter
I do not understand why this scipy operation:
...
3
votes
1
answer
4k
views
filtfilt giving unexpected results
I am trying to filter EEG signals using butterworth filter and filtfilt. I have gone through a lot of documentation and these 2 commands seem sufficient for filtering. However, the results are bizarre....
- 31
3
votes
2
answers
628
views
Given two low-pass digital IIR filters, find bandpass coefficients
In the case of FIR filters it is easy to get a band-pass filter by subtracting the coefficients of two low-pass filter filters or by convolving a high-pass and a low-pass filter:
...
- 133
3
votes
4
answers
1k
views
The reasons for filter explosion
Assume signal $x$, sampled at $f_s = 44100\; \mathrm{Hz}$. I tried to filter it using the Butterworth bandpass filter ( $30\; \mathrm{Hz} - 70\; \mathrm{Hz}$) of order $8$. However, as a result I get ...
- 33
3
votes
2
answers
801
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
3
votes
2
answers
1k
views
Why does a higher sampling frequency mess up my bandpass filter?
I was designing a bandpass filter in python using some of the scipy.signal modules.
I am plotting the frequency response of my filter to verify that my desired frequency is in the passband. However, ...
- 175
3
votes
2
answers
3k
views
what does the order of filter mean?
Recently, I read a paper. In it, it said "a $32^{nd}$ order 100MHz bandpass filter". So, how the filter was designed? Does it mean this filter have 32 taps?
- 155
3
votes
1
answer
2k
views
Bandpass filter to get EEG frequency bands?
I'm doing a project with an EEG to detect driver drowsiness and learned about EEG frequency bands (alpha, beta, gamma...).
As the frequency bands are simple frequency ranges, I wonder if I can use ...
- 239
3
votes
5
answers
4k
views
How to design a narrow band pass filter without DSP toolbox
I've two signals X and Y. These are proximity sensors reading measuring vibrations of a rotating shaft. Now I want to plot orbit plots for these signals. I can plot unfiltered orbits with just X and Y....
- 115
3
votes
1
answer
781
views
Advice on designing a digital filter that doesn't have phase-sensitive edge artifacts?
I'm pretty well versed in statistics, but not really digital signal filtering. I have a data scenario where I expected to be able to pretty easily filter out some noise (human pulse) that's at a known ...
- 219
3
votes
1
answer
705
views
Detecting fundamental zero crossing point
I am looking for ideas from the more experienced members on algorithms for determining the fundamental zero crossing point of a 50 or 60 Hz signal. The fundamental zero crossing point is then used as ...
3
votes
1
answer
4k
views
How to implement bandpass filter on complex valued signal?
I am using Scipy to implement bandpass filter but it assumes that positive normalized frequency is passed but I & Q samples range from [Fc-Fs/2,Fc+Fs/2] where Fs is sampling frequency & Fc is ...
- 47
3
votes
2
answers
1k
views
Filtering Frequency Bands Out of a Signal
Let's say I have a 2 second data set taken at 220Hz sample rate and I would like to filter out the frequency bands associated with the EEG Spectrum:
$$\begin{align}
\Delta:& [1,3]\text{ Hz}\\
\...
3
votes
2
answers
16k
views
Bandpass Filter Implementation in C
I've been googling for a while and came across the audio cookbook and Bjorn's blog explaining it further Link Here.
Background info: I've modified the rtl-sdr open source code to tune to a VOR ...
- 33
3
votes
1
answer
256
views
Is it possible to design a band-pass filter with fewer taps than a series HPF + LPF?
I am digitally filtering a signal that is streaming live. The goal is to reduce the filter delay as much as possible while maintaining the quality of some measurements based on the filtered signal. ...
- 221
3
votes
2
answers
1k
views
change the frequency component of a spectrum in an audio file
I am working on an audio dynamic range compressor using Matlab.
After calculating the FFT of the audio file, I use several bandpass filters to amplify specific bands separately.
What I want to do then ...
- 71
3
votes
4
answers
8k
views
what does the statement "band limited signal of 5 KHz" mean
A band limited signal of $5$ kHz is observed at the output node whose sampling frequency is $600$ kHz. What is the minimum order of the filter?
Does it mean:
a signal that is from $0$ to $5$ kHz on ...
- 31
3
votes
2
answers
345
views
Multiple filters or not?
I'm processing audio signal sampled at 44.1 kHz. After some other processing, I need to filter the signal between ~5-50 Hz. Achieving this for a signal with such a high sampling frequency appears to ...
- 33
3
votes
1
answer
159
views
Feature Selection by Filtering
so there is this paper I'm reading and trying to understand fully: Towards Practical Identification of HF RFID Devices
http://dl.acm.org/citation.cfm?id=2240276.2240278
I don't want to link the PDF ...
- 31