Questions tagged [filters]

In signal processing, a filter is a device or process that transforms a signal by selectively choosing specific frequencies and leaving others with appropriate gain or as it is.

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Convolution Theorem: Hamming Window on a Time Series and Fourier Domain

If we have a set of time series data, y, consisting of 100 data points. One can apply a N (odd) Hamming window as a weighted moving average to decrease the noise. Say, if we choose 7 point Hamming ...
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18 views

Moving noise floor spectrum after decimation

Currently I am working in a spectrometer with a stage of decimation previous the fft. In particular I am decimating with a factor of 16 in two stages of 4 each one. I attach a diagram of the model (I'...
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35 views

What is matched filter in QPSK signal?

Consider we have received a QPSK signal. We than make I (In phase) and Q (quadrature component) which I understand is nothing but multiplying the received signal by the cos(2*pi*f) and -sin(2*pi*f) ...
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How Do Particle Filters Get Velocity When Tracking with Pos Measurements

I am new to particle filtering. I can see when particle filters are used with Ensemble Kalman's, the velocity of the states are taken care of by the Kalman. When tracking using particle filters ...
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26 views

Measuring group delay through a linear phase filter

I'm having a difficult time wrapping my head around a phase/ group delay problem and it corresponding to where you start sampling so I built up a system to test some of these issues. The system passes ...
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1answer
71 views

ARMA model vs. Linear Filter

ARMA Model $$y_t = \sum_{k=1}^p a_{k}y_{t-k} + \sum_{k=0}^q b_{k}\epsilon_{t-k}$$ where $b_0$ is usually 1 and $y_t$ is observable. General Linear Filter $$x_t = \sum_{k=1}^p a_{k}x_{t-k} + \sum_{...
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Difference Between a 1st Order SG Filter And a Least Squares Moving Average

I have been studying SG filters and i recently found another filter which seem to be commonly used in financial data smoothing which is the least-squares moving average, this filter is also called ...
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30 views

Calculating the number of MACs in a system

I want to calculate the number of MACs. I am looking for the method. How would I do it if I know the domain equations from a biquadratic digital filter. I have already calculated the Z domain ...
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1answer
17 views

Is there a hypothetical situation where once can use Wiener filter prior Matched filter to get better result?

Is there a hypothetical situation where once can use Wiener filter prior Matched filter to get better result? Mostly I am looking for an example or a situation where both the filters are required as ...
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Filter interferce within an image using fouire transform in matlab

I am currently reading Fundamentals of Digital Image Processing : A practical approach with Matlab and on page 129 They demonstrate a way to filter an image with strip kinda of noise. Now ...
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1answer
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Is there a noise cancellation technique for over-lapping spectra?

I understand Wiener filter is used to reduce noise, Gaussian noise as well, once we give the noise characteristic. One may derive the filter coefficient in adaptive way as well But can it remove noise ...
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drawing a line from where the tires meet the ground

I followed these steps to write a program in Matlab to detect the edge of the wheels where they meet the ground. Step 1. read the image Step 2. k-means segmentation Step 3. Dynamic binarization ...
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29 views

Re-mixing high and low pass filtered audio has interference in the shared transition band?

Disclaimer: this feels like something that should be obvious from an intro class, but for some reason I can't find anything around this. I'm working on an algorithm that takes a signal, let's call it ...
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72 views

What is the difference between y[n] and y(k) (using square brackets)?

Can I modify y[n] = αy[n-1] + x[n] the same way I would do it with y(k) --> Y(z)? I need H(z), but I don't know what is the difference between using (k), and (n). I often encountered [k] notation, ...
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Notch filtering minimizing artifacts in signal

I have to notch filter the following signal As you can see it is a signal with really high amplitude.And this causes me a lot of problems. I've designed a bandstop filter (46-55 Hz).The MATLAB code ...
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Butterworth cutoff frequency normalization

The issue: I am trying to reproduce the step detection technique as described in this paper. You can see the proposed step detection in the image below. The first part of this technique is to use a ...
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3answers
73 views

How to determine if an IIR filter is causal or non-causal?

It may sound impractical, as only causal system are passively realizable, but what I am facing is a general statement made regarding recursive digital filters: for them to be stable, the poles should ...
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Apodization in the Fourier (frequency) domain on discrete experimental data

Let us assume we had time domain signal as a raw data R (Window 1) and we wish to perform the deconvolution process on R using another set of raw data G (window 2). This is accomplished dividing FT of ...
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Is there a filter to deal with spectral leakage?

Consider we know that our medium is dispersive and we are transmitting/expecting a signal around 10kHz at receiver, as we do not get only 10 kHz, the input has a sligh spread as well. Due to ...
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How to adjust coefficients of a digital biquad filter to different sample rates?

I have the filter coefficients given by specifications of an algorithm. It says that these coefficients are calculated for an sample rate of 48kHz. How can I calculate the coefficients for different ...
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1answer
36 views

Can we band pass filter QPSK signal?

Consider we have QPSK signal with carrier frequency 10kHz. Generally, we demodulate or use matched filter on the the QPSK signal and recover the transmitted bit or the symbols. If the QPSk signal is ...
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42 views

Notch filters: why is $H(e^{j0}) = H(e^{j\pi})$ required?

I'm studying for the final exams and many example exercises require to design fir notch filters of length 5, given some passband and some stopband frequencies. You'...
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What is prewhitening filter mode?

In this paper, the following prewhitening filter is described: $$ C(z) = \sum_{k=0}^n c_{k}z^{-k} $$ where $n$ and $c_k$ are known. The paper also describes the values $C(\lambda_{k})$, with $\...
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Is a LTI filter completely characterized by its frequency response

I know that we use the frequency response to determine the properties gain and phase delay of a filter. However, I was wondering if this is enough for a complet characterization of the the filter for ...
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SIne and Cosine Filter

Im new in programming. Someone who is skilled in mathematics has given me this formula, but I do not know how to use it. He told me this is the code of the program and you do not need anything else. ...
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1answer
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Peak Detection on ECG signal

I've been working on a ECG signal collected during exercise through my chest mount heart rate monitor. My goal is to accurately detect the location of the R-wave; R-wave is the narrow peak similar to ...
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Finding the differences(using features, not subtraction) in order to find differences in signals

I have a question. Let’s say I have two signals (discretely represented as arrays), $S_1$ and $S_2$ as shown below. $S_1$ has a similar form to $S_2$. If the signals are subtracted, $S_2-S_1$, they ...
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Bank Filter over a 1D signal

I would like to apply a filter bank decomposition over a time series signal. If I am correct, it is necessary to take a low pass and a high pass filter, and then convolve them with the time series. ...
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2answers
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Definition of difference between compression and filtering

I'd like to explain the motivation. It sounds like a neuroscience topic but I am after the strict Signal Processing POV. (I don't come from a Signal Processing background). Interested to learn ...
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Given a filter (coefficients) how can I make it minimum phase?

Consider we have a low pass FIR filter (or other type of filter) that means the filter coefficients are given. Now we want to have the same (or almost) frequency response but a minimum phase filter. ...
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Automatic Rf filter testing using python code

I am assigned to test the RF filter automatically using python code( Instrument control using GPIB protocol). Since I am new to coding, I don't have any idea about how to proceed. It would be great if ...
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Understanding the magnitude of frequency response filterbank based on elliptic filters

I've implemented a 10-channels filterbank with octave-scaled second-order elliptic filters using the Python's library scipy.signal. Here is the magnitude of the frequency response: Can someone ...
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Is the zero part of a RRC filter generated signal sent?

When you use a RRC filter you add extra symbols at the end of your generated data because of the delay of the filter. When the data passes through the filter it gets up-sampled and the delay is ...
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z-transform and DTFT properties

I actually do not understand what to do with the third property of the impulse response g[n] and how it has to be determined. Thanks in advance!
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What happens when the frequencies of the signal does not lie within the reconstruction filter passband?

Assume we have an analog signal that has frequency components between 40Hz and 50Hz and 0 otherwise. If we sampled this signal with 100Hz sampling frequency then passed to DAC with the same sampling ...
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1answer
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Equalisation of FFT spectra

The image shows the frequency spectra of a signal recorded using a SDR. The SDR is of DirectDownSampling type and has some compensation in the signal chain to compensate for the DC spike which would ...
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Setting the measurement noise covariance matrix for sensors with different variances

I'm implementing a kalman filter that fuses data from 2 different sensors. Both sensors provide the same data (a 3d position measurement), but the variances for each sensor are different (i.e. one is ...
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remove \ minimize first side lobe ringing artifacts due to data truncation

I have a truncated data set that I need to transform, for example: ...
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Fusing like data from multiple sensors using kalman filter

I'm new to kalman filters and filtering, and I'm working on a personal project where I have multiple readings all providing the same data (3d position in space, provided via computer vision algorithms)...
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Filter design for decimation of 1.1 kHz sensor sample rate to 100 Hz processing rate

Suppose, you have a signal source which is sampled by 1100 Hz and is "somehow" band limited to either 235 or 440 Hz. In my application, that's the ST IIS3DHHC accelerometer. There is an appnote for ...
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2answers
37 views

What do the 1D filters represent when using imfilter?

I am reading the source code of an algorithm that is used to process an image. While reading this source code (and others), I've found lines of code of the form ...
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29 views

Reducing hardware demands for an adaptive and complex-coefficient FIR filter

I want to implement a complex-coefficient FIR filter with adaptive coefficients in hardware (FPGA). The inputs to this filter are the I and Q channel as separate wires. The outputs are the filtered I ...
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1answer
42 views

Distort voice to hide talker identity as much as possible

I need to develop an app which makes speech recognition. Because I need to be able to constantly improve the recognition capability, I would like to train the engine with real recordings and match the ...
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1answer
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duration for a signal after filtering [duplicate]

I have a signal $s(t)$ of duration $T$. This signal doesn't have a limited bandwidth. To solve this problem, I filter it with a pulse shaping filter (raised cosine filter). My question: Does ...
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1answer
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Cascade filter realization equivalence? [closed]

Given $$H(z) = \frac{11 +4.6z^{-1} -26z^{-2}-3.75z^{-3}}{1-z^{-1}-8.75z^{-2}}$$ I'd like to know whether this realization: Is equivalent to this one? In short, is the direct form realization ...
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2answers
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Filtering Surge Signals

I am working on a matlab program which needs me to detect the pattern of surges in a signal and then remove them. I tried out various filters like median, hampel, butterworth etc. but couldn't get an ...
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1answer
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Plotting phase delay from first principles giving different result from phasedelay() function. Why?

I have a length 10 Finite Impulse response as shown below, and I am trying to find the phase delay of this FIR. $$h[n]=\begin{cases}0.1,& 0\le n \lt 10\\ 0,&\textrm{otherwise}\end{cases}$$ I ...
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In the Sampling Theorem, why are the image frequencies at n*fc not a problem?

In this example I have been working through, we first look at the situation when fs > 2fc and then the situation when it isn't: In the example, the frequency responses of a sampled sinusoid at fc = 5 ...
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27 views

Correctly interpret Butterworth filter frequencies

I am using the butter function from the signal package in R to filter my data. The data is Fourier-transformed (complex numbers) - and I want to filter out specific frequencies (I have a 256Hz ...
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1answer
54 views

FIR filter not eliminating out of band noise?

I have a simple FIR filter that should eliminate all lower frequencies: ...