Questions tagged [filter-design]

Fiter design is the process of designing a filter.

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3answers
3k views

how to make CIC compensation filter

I gotta wrap my head around to design CIC compensation filter I'm studying by referring these materials: Altera, "Understanding CIC compensation filters Hardware Efficient FIR Compensation Filter ...
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1answer
192 views

coded filter vs fdatool : inconsistency in the results for same parameters

I tried creating a filter in 2 different ways in Matlab and I obtain different results: one filter is stable, whereas the other one is unstable. Coded filter ...
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2answers
1k views

Understanding Arrangement of second order sections

When splitting higher order recursive filters into more convenient 2nd order sections (biquads), in matlab, we usually use zp2sos to convert. In document, there's a ...
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1answer
270 views

digital butterworth filter design error

I am trying to design a digital butterworth filter for the given specifications.. code is posted below.. rp=3; rs=15; FS=1; wp=0.5*pi; ws=0.75*pi; pwp=2*FS*tan(wp/2); pws=2*FS*tan(ws/2); [n,wn]=...
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4answers
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Audio EQ Cookbook without frequency warping

The famous http://www.musicdsp.org/files/Audio-EQ-Cookbook.txt offers a set of [real] biquad filter calculation formulas that generally work fine. However, when filter's frequency approaches Nyquist ...
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1answer
280 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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5answers
2k views

What's the Q factor of a digital filter's pole?

For the analog S-plane, the Q factor depends on the angle of the complex pole $p$ from the horizontal axis, $\theta = \arg p$: damping factor $\zeta = \frac{1}{2Q}$, and $\zeta = \cos(\theta)$, and $\...
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0answers
150 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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1answer
2k views

Pole/Zero Placement for Filter

I'm attempting to design a FIR high pass filter than keeps signals above 200Hz and rejects signals below 60Hz with a sampling frequency of 500 samples/sec. This is my first time attempting this and I'...
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1answer
264 views

How do I take the real part of this bandpass filter system's output?

I'm stuck on a final step in this problem. Essentially, there are the two systems above, which we'll call System 1 (Fig. 4.26, with ideal lowpass $H(jw)$) and System 2 (with $H_1(jw)$). The question ...
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1answer
126 views

Identify the system from input and output

I am using Excel. If I have an input and an output, and I know that a recursive band-pass filter produced the output, how can I can find the coefficients of that filter?
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2answers
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Filter design / Analysis apps

There are a plethora of tools, both commercial and free, which I have found online for designing filters. The ones I have tried (so far) prompt for frequency response, number of steps (for FIR), then ...
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0answers
38 views

Which values do I use to filter a specific frequency with an RLC circuit? [closed]

I have a RLC circuit with transformation $$H(s) = \frac{R}{Ls+\frac{1}{Cs}+R}$$ and I know that by setting $s=j\omega$ I can obtain the frequency response of this system. What I don't understand is ...
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1answer
5k views

What is the Roll-Off factor of a Root Raised Cosine Filter?

When designing a root raised cosine filter on Matlab, there is an option to set its "roll-off factor". What does this mean? I have been looking around for a while but I can't seem to find a clear ...
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2answers
9k 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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1answer
129 views

Why bother impluse invariance, bilinear transform?

Now that we can operate in the frequency domain by way of FFT. We can implement ideal lowpass, highpass and bandpass digital filters. then why there many textbooks talk about designing digital ...
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2answers
1k views

multiplications per second for FIR filter

In my filter the fs=300MHz. and no. of coefficients is 31. I have following queries. (1) what will be the number of multiplications per second? (2) can multiplication be done in one clock cycle? (3) ...
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1answer
131 views

FIR filter design

I am designing an FIR filter.my specs are fs=300MHz, Fc=45MHz, Fs=75MHz, passband gain=3dB , stopband attn=>40dB. what parameters I values of a have to provide in firpm for the minimum order filter ...
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2answers
198 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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1answer
162 views

How to periodically estimate states of a LTI if the output is measured irregularly?

How can I periodically estimate the states of a discrete linear time-invariant system in the form $$\dot{\vec{x}}=\textbf{A}\vec{x}+\textbf{B}\vec{u}$$ $$\vec{y}=\textbf{C}\vec{x}+\textbf{D}\vec{u} $$...
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1answer
74 views

High Speed Digital Signal Processors [closed]

Can anybody suggest me the highest speed DSPs available in the market now. Also, what would be the best for a filer design application a DSP or an FPGA?
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3answers
25k views

Group delay of the FIR filter

For an FIR filter, with symmetrical tap values $h[N-1-n]=h[n]$, why is the group delay $\frac{N-1}{2} T$ (where $N$ is the number of taps of the FIR filter and $T$ is the sampling time)? Why is ...
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2answers
1k views

direct Frequency domain FIR filtering vs Overlap-add method

I'm trying to do bandpass filtering of a EEG signal samples at 250Hz and benchmarking the following 4 methods of FIR filtering for different filter orders. The length of the signal is 15000 samples. ...
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2answers
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why the number of filter coefficients in FIR filter has to be an odd number?

I calculated the order of the FIR filter to be 31(N). so, the number of coefficients has to be 32 (N+1). so, I have to increase it to 33 to make it an odd number. Why the number of filter ...
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1answer
187 views

Accumulator with decay?

I am using an accumulator in the form of X + [Y-1], X plus the unit delay of the output. Is there an accumulator that follows this form, but will fall to 0 over time, similar to a differentiator?
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3answers
738 views

Picking out a signal that appears to be noise inside a large signal

I have a signal from a photodiode sensor that has two types of noise. One type of noise is ambient light white noise that gets introduced just from the surrounding environemnt. The other type of noise ...
2
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1answer
752 views

Creating a digital filter, from Laplace to $\mathcal Z$-transform (zero order hold) to code?

I'm trying to create a digital filter in code(C) but any language is fine. Now I've got an analogue filter that I have represented by an equation in the Laplace domain and I want to try and implement ...
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1answer
1k views

Implementing digital filter by padding with zeros

I am making a 9th order digital bandpass filter with lower and upper corners of 200 kHz and 40 MHz respectively. I am using this filter to filter a 1D time domain signal which is 64k samples long ...
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2answers
2k views

Reconstruct FIR frequency response from the coefficients

There is a lot of tools for designing FIR filters. Using one such tool I have designed a filter that satisfies my needs. It's coefficients are as follows: ...
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1answer
2k 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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1answer
2k views

Real and Imaginary Frequency Responses of a single complex pole

I'm filtering a real signal with a single complex pole with a complex coefficient (a_re [real part] and a_im [imaginary part]), I also have a gain coefficient but I'm gonna leave it out for the sake ...
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0answers
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Using Python with scipy.signal firwin, how do I know how many taps/coefficients should be used?

I need to alter an FIR filter which I know very little about. I have a signal which need to be altered, and looking at a Python script used for this task, I see that it uses Scipy's signal library, ...
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1answer
942 views

Slepian or DPSS window

I am planning to use Slepian or DPSS window in my application where I want central lobe to be concentrated and also have low bandwidth: http://en.wikipedia.org/wiki/Window_function#...
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3answers
191 views

How to filter noise from continuous path in image

Problem statement In the dataset above, you can notice a continuous path and then a noise-band at around 320-400 on the x-axis. I want to be able to apply a filter that amplifies the continuous path ...
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1answer
253 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} \;\; |\mathbf{u}|<|...
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1answer
645 views

Design and implementation of causal band-pass filter for biosignals - what to consider? [closed]

I currently work in a project of clinical software (C#) which deals with clinical biosignals, specifically EMG and other low-frequency signals (load-cells, goniometers, and other biomechanical ...
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1answer
124 views

Approximate a System Frequency Response with a Filter in MATLAB

suppose I know the frequency response of a (linear) model approximating a real physical system but only at a specific frequency $f_0$ (so basically I have a complex number whose module is the ...
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4answers
15k views

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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0answers
119 views

Any way to compensate for fractional delay filter's weakness between taps?

A little background: I have an FPGA (running at 200MHz) that I am creating multipath events using buffers, all of that works. I take RF, mix down to IF, sample, make adjustments, out the DAC, and ...
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2answers
2k views

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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1answer
146 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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1answer
367 views

Best way to inverse Hilbert on FPGA?

I have a real signal that is being sampled via ADC and passed to a Xilinx V6 FPGA. I then do a Hilbert transform on it using the FIR compiler core and get the complex signal (I and Q) to tweak the ...
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3answers
142 views

Why are recursives methods useful for FIR filter design?

As I understand it, FIR filtering is a linear process. That mean for me that the whole filtering process will have a fully predictable behavior. So, could someone explain why a universal ...
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1answer
893 views

Confusion about result of FIR All-pass filter design

I try to design a FIR All-pass filter with random phase in the frequency domain. I am a bit confused by my result and am not sure if the reason is a programming error or a misconception about ...
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1answer
63 views

Is there a way to break an analog sound signal up and send it through two radio chips at double the data rate of one?

Here is a radio chip for audio that sends at a CD-level data rate. Could you sample an analog signal (for instance from a guitar pick-up or microphone) in such a way that you could transmit using two ...
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1answer
69 views

Applying Discrete Filters

I have an exercise in DSP. I learnt about discrete filter but I don't know how to apply it to produce an output from an input signal. Please guide me to do this: Assume fundamental sample time is 1 ...
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2answers
26k 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 ...
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2answers
1k views

FIR-Decimation and Low-pass filter (taps vs number of input points vs number of decimation stages)

I am new to digital filters and trying to understand parameters behind them. Scenario I am trying to get DC value from signals sampled at 100kHz sampling rate. such high frequency is used due to ...
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1answer
732 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 bounded,...
2
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1answer
148 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 $\...