Questions tagged [filter-design]

Fiter design is the process of designing a filter.

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Behaviour of difference equation does not match that of its z-domain transfer function

I have obtained the following z-domain transfer function: $\frac{Y(z)}{U(z)}=\frac{3.3641×10^{-7}×z^{6}+1.5584×10^{-5}×z^{5}+6.7263×10^{-5}×z^{4}+ 5.5016×10^{-5}×z^{3}+8.525×10^{-6}×z^{2}+1.2303×10^{-...
2 votes
1 answer
161 views

What order of FIR filter is equivalent to an IIR filter for same design specifications and to get same magnitude response

I have to design a bandpass filter with passband frequency [300Hz 500Hz] and sampling frequency is 16kHz.The stopband attenuation required is 60dB.I have used butterworth filter in MATLAB to design ...
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1 vote
1 answer
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Filter IIR, 1/3 Octave Corner with 2 Octave BW

I'm trying to design a new filter with IIR to filter out specific bands. Basically it's a bandpass filter with 2 Octave or 3 Octave bandwidth but the filter order should be equal to 1/3 Octave filter. ...
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1 answer
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How to derive filter design (with parameters) from existing FIR weights

I made a thing which involves a FIR filter, and in that process I cobbled together some random numbers for the convolution which I figured would work the way I wanted. Now I want to be able to take ...
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How can I correlate two noisy voices in order to enhance their result?

I have an array of two microphones, spaced out, which continuously transmits audio input to a central processing unit. There is a slight delay between them, which is sometimes variable because they ...
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83 views

Parallel connected FIR filters type III

I am currently studying dsp and I have a question: Let us assume multiple FIR filters with generalized linear phase of Type III and real IRs $h_1[n], h_2[n], ..., h_k[n],$ interconnected in parallel. ...
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15 views

Savitzky-Golay: which property preserves peak shape?

I found this excellent thread on Savitzky-Golay filters that explained almost everything I wanted to know: Savitzky–Golay filter vs. IIR or FIR linear filter There is 1 thing that I didn’t find: Which ...
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4 votes
3 answers
296 views

Convert Sample Rate of IIR Filter Coefficients

I have IIR filter coefficients and zeroes, poles for that filters. But all filters are generated with 192kHz sample rate. I have no other info about filter properties such as Fc or filter type or Q. ...
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1 answer
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What does frequency filtering actually practically mean?

I've got an electronics circuit which was filtering between a Passive HPF stage (1uF and 330K) and an Active LPF stage (4.7uF and 10K). As you can see it was filtering between 0.48Hz and 3.38Hz, and ...
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2 answers
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How to Find Elliptic IIR Filter Order?

Can anyone explain to me how to use this equation to find the Order? Let's say $$\Omega_p/\Omega_s =0.509$$ and $$e/\delta = 0.00349$$ How can I find the Order? I'm so lost i don't know how to use ...
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1 answer
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Trying to implement a digital A frequency filter (continuation)

Following this post some user advised that the filter developed there should be broken down into first and second-order sections and cascaded. In a paper i found the same thing is told: So i made ...
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Can a filter be fit to explain a response?

I'm trying to classify a stimulus-response relationship and would like to fit a filter that best explains the response. I don't really work in DSP so there may be some vocabulary I'm missing, but ...
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2 answers
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Matlab IIR stopband filter attenuates my sinusoid input with frequency in the passband

I'm a DSP newbie trying to get into the field. Despite being able to use some of the MATLAB tools, I'm still not completely solid on some intuition of the frequency domain. I've implemented a biquad ...
2 votes
3 answers
109 views

Why the sum of filter coefficients of an FIR filter does not add to 1?

In MATLAB, I have generated an FIR low pass and high pass filter of order 16. The code is as follows: ...
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3 votes
1 answer
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Selective Discrete Time Derivative Filter

I have hit a problem which could be probably solved via discrete time derivative filter able to calculate the derivative of two specific harmonics of the input signal (namely frequencies: $f_1 = 100\,\...
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1 answer
68 views

digital Butterworth high pass filter

I am trying to high-pass filter a signal using a Butterworth filter, but I am getting the following results : As in the picture, there is no signal decay. python code: ...
2 votes
2 answers
75 views

Why is ARMA preferred instead of AR?

ARMA basically is an AR model which considers past inputs to the filter as well. But what is the benefit of taking past inputs to the filter if we are considering real-time processes which are all ...
1 vote
2 answers
136 views

LPF design with pole/zero placement at rejection at specified freq

I am about to design a low-pass filter with a zero/pole placement method in such a way that rejected frequencies are placed at $500\,\text{Hz}$ and their multiples. Are there any simple instructions ...
3 votes
0 answers
32 views

Given the following signalling elements design the optimum receiver?

Given the following signaling elements, \begin{align} g_1(t) &= A \quad \text{for} \quad -T/4 < t \leq 0 \\ g_2(t) &= A \quad \text{for} \quad 0 < t \leq T/4 \\ g_3(t) &= A \quad \...
2 votes
3 answers
89 views

FIR-filter output gain

Lately, I've been doing some FIR-filter simulations as a part of a programmatic circuit design course. One task was to use different constants $b_i$ for the multiplying stage of the filter and see how ...
7 votes
1 answer
255 views

Levinson's algorithm and QR decomposition for complex least-squares FIR design

I'm studying Mathias's thesis Algorithms for the Constrained Design of Digital Filters with Arbitrary Magnitude and Phase Response. In section 2.1.2 the complex LS approximation problem is defined by ...
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1 vote
4 answers
138 views

Half power frequencies is -6dB or -3dB

I have to design a 1024 order band pass filter in matlab. The pass band frequencies are [376 480] and fs=16kHz.It was written in documentation of MATLAB that "the cutoff frequency is the ...
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1 answer
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Frequency response of a bandpass filter in MATLAB

I want to see the frequency response of 1024 order bandpass filter in MATLAB. The sampling frequency is 16kHz and the pass band frequency is [376Hz 480Hz]. I have implemented the bandpass filter using ...
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1 vote
1 answer
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What is this similar-but-not-quite-windowed-sinc impulse response?

While implementing/studying brickwall low pass filters for digital audio, I decided to run a unit impulse through FabFilter's Pro-Q 3 brickwall low pass filter to see what the resulting impulse ...
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2 votes
1 answer
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Filter Design - Quantifying the Tradeoffs

Background I've been given the task of designing a filter. The problem is constrained in terms of filter order, and as such, the specs initially conceived for the filter seem challenging, and we think ...
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5 votes
1 answer
262 views

Filter design with constrained impulse response

What I want I wish to design an LPF, preferably an FIR, but also open to IIR. My constraints: I care about phase non-linearity. Thus if I use an IIR, I need a filter similar to a Bessel filter. My ...
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When is perfect analytic filtering (discrete) suboptimal?

Defined as "negative DFT bins zero", when are such filters suboptimal for AM/FM extraction or related filtering? This answer reads, [nulling] also has the worst performance compared to ...
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Using kalman filter in R for sine wave frequency estimation

I'm pretty new to Kalman filtering techniques, and have a problem that I'm trying to solve. Imagine in a lake I have a splash generator that sends out sine waves across the lake. At various places ...
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Converting a SISO LTI System to a MIMO LTI System

I have a SIMO IIR filter represented as a state space system. I'm wondering if there is a canonical way of converting a IIR filter into a MIMO system, so I can calculate $N$ terms as input at once and ...
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3 votes
1 answer
267 views

How to get scipy remez to give matlab firpm answer?

If I run this in matlab: h = firpm(100,[0 0.1 0.2 1],[0 0 1 1]) and this in scipy: h = remez(100,[0, 0.05, 0.1, 0.5],[0, 1]) I ...
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Efficient CIC Decimation Filter in C

Does anyone have advice on efficient CIC Decimation filter implementation. I designed a basic 4th order CIC filter with a 64 decimation ratio in C (below). I am currently testing this on a Sharc SC589 ...
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I just computed an DFT and FFT of a sinc function, but when I visualise them the results are strangely different? what am I missing

The idea here is to improve a Sinc function by manipulating its Fourier transform. As you can see, the tophat has ripples in the bands of interest and I want to eliminate them by smoothing them with a ...
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1 answer
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Matching outputs of FIR filters based on time domain convolution method and overlap-save method

I'm trying to match(to the best extent possible) the outputs of FIR filter based on Frequency domain overlap-save method and time domain convolution method resp. I was able to get most of the output ...
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2 answers
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Problem with transforming a tophat to obtain a sinc?

I have observed that the Fourier transform of a tophat function is a Sinc-like function with higher peak sidelobes than an actual Sinc. However, the Fourier transform of a Sinc is a tophat-like ...
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1 vote
2 answers
115 views

Constraints on number of taps in a FIR filter vs. FFT length

I want to implement a FIR highpass filter for acoustic signals. I generate the FIR using Python's SciPy code: ...
4 votes
1 answer
350 views

Unwanted periodicity in data

my signal consists of data points that represent the (vibration signal) energy measured during process cycles of a machine. Due to the hydraulic power units emptying and filling again, some ...
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3 votes
3 answers
181 views

Time-varying Notch Filter in C

I have a digital notch filter (band-stop) implemented in C. It works very well. The issue is that varying the filter coefficients in order to track a noise signal that varies in frequency results in a ...
2 votes
2 answers
87 views

Bilinear transform for a system in zero-pole-gain form

MATLAB's bilinear performs the following steps for a system in zero-pole-gain form If fp is present, it prewarps: ...
1 vote
1 answer
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Sampling frequency in bilinear transform when designing butterworth filter

I'm trying to design digital Butterworth filter from scratch. First I use butterap to design an analog prototype to get zeros, poles and gain ...
0 votes
1 answer
44 views

Why does applying fir filter in R (gsignal package) increase the magnitude of all values?

I am new to signal processing and I am sure this is a very rudimentary question. However I have done various searches and I cannot find an explanation (possibly because my knowledge is insufficient to ...
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2 votes
3 answers
492 views

What is the relationship among digital filter cutoff frequency, signal frequency and filter settling time?

I have some general observations but I am asking if anyone can summarize more conclusively: (1) Filter settles slower if the ratio between signal frequency and filter cutoff frequency is smaller; (2) ...
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1 vote
1 answer
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how to design the $\text{sinc}(\cdot)$ filter for OFDM oversampled system

We usually zero-padding into the moulated data of OFDM before performing IFFT operation to make the design of anti aliasing filters easier ( the cut off can be less sharp) hence save cost. That ...
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Analytical derivation of convolution and multiplication implement of time-domain signal

I have a system model as shown in figure 1. I want to change the model to a new schematic as in figure 2. How to analytically derive the filter $H_2$ if all parameters are known? I guess that we will ...
2 votes
1 answer
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How to design digital Butterworth filter and return its zeros, poles and gain

I'm implementing digital Butterworth filter and encounter some numerical problem when filter order is high using direct form, so I wonder how to design the digital Butterworth filter and return its ...
0 votes
1 answer
61 views

MATLAB polystab function: It doesn't seem to be doing anything!

I've been attempting to stabilise an unstable filter (unfortunately, I cannot redesign the filter in a way that it is more stable and that is NOT an option). It is derived from an approximation of ...
2 votes
3 answers
107 views

FIR filter phase response at fs/2

I am currently building a FIR filter based on frequency sweeping data (0 Hz to Fs/2), i.e., transfer curve in frequency with the sampling rate of Fs. The phase response is shown in the following ...
1 vote
1 answer
54 views

Problems designing a notch filter based on allpass in MATLAB

I have to design a notch filter based on an allpass but when I plot the resulting filter in MATLAB it does not fit my specification. I'll provide you with some background. The filter has the following ...
1 vote
1 answer
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Matlab Filter Designer "Filter Information" shows wrong order

I want to design a low pass filter using the Filter Designer tool of Matlab. The filter order should be 10. I chose the Blackman window method and specified the order of the filter. However, "...
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2 votes
1 answer
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A problem on FIR filter design given a difference equation

Given the following difference equation: \begin{equation} y(n)=2x(n-2)+3x(n-5) \end{equation} describing the structure of an FIR filter, design the direct form of one. What is the order of the filter? ...
3 votes
1 answer
271 views

Filter type selection for signal envelope detection

Working on a signal envelope detection code in Matlab in which an RF signal envelope is to be created. The flow is such that filtering is performed according to the detected presence of a signal in a ...
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