Questions tagged [discrete-signals]

A discrete signal or discrete-time signal is a time series consisting of a sequence of quantities.

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34 views

Is the Schroeder Allpass implementation in Freeverb incorrect?

I've been looking into the venerable Freeverb and I see that CCRMA state that it uses 4 Shroeder Allpass filters in series, but when I look at the source code I see: ...
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2answers
54 views

Can we use Gardner timing error detector for multi level QAM or OFDM systems?

Sampling frequency offset (SFO) between the transmitter and the receiver in any system causes a gradually increasing timing error which is seen as an increasing phase rotation (function of time). In ...
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Frequency response of discrete time system involving interpolation and resampling

I am working on a problem towards calculating frequency response of discrete time system(does interpolation followed by resampling) which looks like: x(n) is fed to linear interpolator(h(t) = ...
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1answer
30 views

Mixed - Discrete and Continuous system Laplace domain stability - Effect of Sampler and DAC

I have a system whose the plant transfer function is continuous and the compensation is discrete. I have an ADC which allows to measure the output of the system and a DAC which allows to control the ...
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21 views

Random variation of Bit Error Rate (BER) with increasing SNR for QAM 64 System

I am simulating a communication system with a transmitter and a receiver, where the transmitting signal is in QAM 64 format. The transmitter is connected to the receiver (back to back) and at the ...
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1answer
49 views

Why is z (and not ω) the variable of interest for discrete time systems?

A continuous time domain system is well described by the Laplace transform. It allows to express any continuous signal x(t) as the integral sum of weighted complex and exponentially growing/decaying ...
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1answer
54 views

One Sided Waveforms in Discrete Time and Frequency?

Consider a discrete time waveform $x[n]$ with $n \in [0...N-1]$ that is zero for all samples $n > N/2$ and non-zero elsewhere. Is there a waveform such that its Discrete Fourier Transform $X[k]$ ...
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1answer
37 views

Ideal Allpass filter

Is it possible to implement an ideal allpass filter in Matlab? The filter response should be like this: Note: the photo is imaginary (I did it using paint).
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1answer
34 views

Identify out signal from in signal and impulse response

Hi there I am studying a course in signal processing and systems. I was given an excecise which I am having a great deal of trouble solving. I am allowed to solved using matlab, but for top marks I ...
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1answer
34 views

How can I add complex WGN to a complex damped signal for a specified SNR?

I want to add complex wgn to a signal for a specified SNR. I have been using the following lines: ...
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3answers
106 views

Some signals whose Fourier transform are a particular rotation of its self

Let $N\in \mathbb{N}$. I am looking for a non-zero scalar $\lambda$ and a nonzero vector $$f=(f(0),f(1),\cdots,f(N-1)) \in \mathbb{C}^N$$ satisfying the following equations for $l=0,\cdots,N-1$: $$\...
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1answer
50 views

Apply FFT to positive spiky signal

I have a signal that looks like this It has regularly occurring peaks 50 units apart, and offset from 0 by approximately 20. I thought I could apply the DTFT to this signal and extract the period (...
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53 views

How to compute convolution using the Discrete Hartley Transform

It's easy to compute the Discrete Hartley Transform of a 1D signal: ...
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1answer
89 views

1ppm Sampling clock offset in Matlab

How to emulate a sampling clock offset (between the transmitter and the receiver) of 1 part per million (SCO=1ppm) in Matlab? Theoretically, I can upsample the signal by a factor of 1,000,001 (one ...
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1answer
53 views

Compare two Fourier transforms of two signals by calculating the coherence

My overall aim is to compare the edges of two images by comparing their Fourier Transforms (FFT) and to calculate one number as a key performance indicator that describes how much they are similar to ...
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29 views

fft result with the number of integer multiples of fs

With the cosine signal fc=3Hz and the fs=13Hz as below, fc=3; fs=13; Ts=1/fs; N=101*13; % 101 times of fs n=0:N-1; x=cos(2*pi*fc*n*Ts); and then fft with the ...
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2answers
36 views

Discrete Fourier transform with negative frequencies

In the standard definition of Discrete Fourier transform, as in Wikipedia, only positive frequencies exist. I want zero frequency to be at the center of the spectrum. In such a case, how should I ...
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1answer
26 views

A discrete time signal $x[n]$ is defined in terms of unit impulse function.Express the signal $x[n]$ in terms of step signal

A discrete time signal $x[n]$ is defined in terms of unit impulse function as follow $$x[n]= 1-\sum_{r=3}^\infty \delta[n-1-r]$$ If $x[n]$ is expressed in terms of unit step function as $x[n]=u[an-b]$ ...
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$Z$-transform of a multilinear function/ consecutive multplication of $k$ signals $y_1(n), \ldots, y_k(n)$

How should one go about calculating the $Z$-transform of a signal that is the multiplication of $k$ signals (i.e. a multilinear function with regards to signals $y_1(n) \ldots y_k(n)$ ? Namely, $\...
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I/Q Imbalance Correction using S.W. Ellingson Algorithm

Correcting I/Q phase and amplitude imbalance using S.W. Ellingson method. https://www.faculty.ece.vt.edu/swe/argus/iqbal.pdf -- S.W. Ellingson Algorithm When I try to use the set of equations to ...
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1answer
51 views

Discrete implementation of the PI controller

I have been implementing discrete PI controller in the incremental (velocity) form in C++. I have been looking for the anti-windup mechanism. One idea which I have can be described by following ...
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58 views

Problems discretizing a notch filter - Chebyshev Type I

I'm trying to implement and discretize a notch filter (Chebyshev type I) these specifications: Ws = 2pi[2000 2500]; Wp = 2pi[1000 7000]; Rp = 0.5; Rs = 40; But when I try to use discretization methods,...
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36 views

How can I define x(t) in terms of n?(matlab)

I have a signal x[n], that is sum of two sinusoidal signals. $x(t)=sin(2𝜋100t)+0.7cos(2𝜋500t)$ ...
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11 views

How to figure out frequency weightings on acceleration data using ISO 2631?

I'm trying to convert the raw acceleration data into frequency weighted acceleration data. According to ISO 2631: The acceleration signal may be analyzed and reported as either constant bandwidth or ...
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1answer
116 views

Is there mathematical relationship between the FFT and DCT transforms

I need to model the relationship between the DCT and DFT transforms (If it exists). I mean real signal $x \to y = \textrm{DCT}(x) \to z = \textrm{DFT}(y)$, so I need to get the relationship between ...
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1answer
46 views

If we take Z-transform of a signal & find its ROC. How to use this ROC? There are ∞ signals in ROC, suppose we choose any signal what to do with it?

If we take Z-transform of a signal & find its ROC. How to use this ROC? There are infinite signals in ROC, suppose we choose any signal from ROC, what to do with it?
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1answer
53 views

RF-Chain Signal Delay for Sensor Switching

Lets have a RF-chain as above with system bandwith from HP corner to the green line say 1 MHz. The signal accumulates delay as it passes through this analog chain, and due to it being non-liner filter ...
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1answer
25 views

Is there a difference measure that is insensitive to shifts?

I'm trying to figure out a difference measure that is relatively insensitive to time shifts. I have tried DTW (dynamic time warping.) This is the result: The signals on the left are clearly more ...
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21 views

How to determine STFT parameters as a function of desired resolution

None of the Q&As I've seen thus far have given a clear answer to what seems like a simple question: assuming I know the CenterFrequency, ...
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1answer
22 views

DTFT of $(-1)^{n}\frac{\sin((7\pi / 8 )n )}{\pi n}$

The DTFT without $(-1)^{n}$ is relatively easy but with $(-1)^{n}$ I am not sure how it would be solved. I hope anyone can help
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35 views

I tried two approaches and gained the different conclusions of judging the stability of the transfer function of the system

We want to judge whether the system is stable or not. Given the below transfer function. $$ H\left( z \right) =\frac{\left( 1+2 z^{-1} \right) }{\left( 2+z^{-1} \right) } $$ $$ H\left( z \right) ...
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1answer
75 views

How to take into account phase differences when doing Fourier Transform?

I apologize if the title seems very vague, I don't really know how to put it a different way. From what I understand, the Fourier transform is essentially just doing a dot product between multiple ...
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30 views

What is the unit of the color axis on a Matlab spectrogram, and bandpower?

I am new to signal processing, but successfully made a spectrogram with Matlab. It is nice and working, showing the expected output on the graph, but I just cannot understand what the numbers mean on ...
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2answers
74 views

What is phase shift?

I'm reading about when a $H(z)$ system is min phase or max phase, and I get when a system is a min phase or max phase depending on the location of the zeroes. But I don't get at all the phase shift ...
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1answer
31 views

How to add complex WGN to complex damped exponential and compute SNR?

I am new to the Signal processing domain, So my question might sound basic. I am trying to reproduce the results from the paper Decimative subspace-based parameter estimation techniques by Geert ...
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1answer
54 views

Why is $x[n]=\sin(\frac{12\pi n}{5})-\sin(\frac{2\pi n}{5})=0$

I was trying to find the period of $\sin(\frac{12\pi n}{5})-\sin(\frac{2\pi n}{5})$, each of the sinusoids has a period of 5 however their difference has a period of 1. It turned out that they're ...
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15 views

Log in MFCC vectors incorrect according to Source-Filter Theory

In the MFCC vectors computation given many in places and here we apply log after we average with the mel bands. However, the source-filter theory says that the source frequency is modified by the ...
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3answers
108 views

On what it means for a system to be minimum phase

From my undestanding I get that when a system's poles and zeros are all inside the unit circle then it means that it's minimum phase. But I don't get how the location of zeros and poles are related to ...
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1answer
30 views

Find response of discrete time LTI system given input and impulse response

For this question the guide says to use $Y(e^{j\omega}) = H(e^{j\omega}) X(e^{j\omega})$. I have been able to find the discrete time Fourier transform of the impulse function as $$H(e^{j\omega}) = \...
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59 views

Let a LTI system be causal and stable with the transfer function being… show that

if the system is an IIR LTI causal and stable one, and the transfer function is \[H(z)=\sum_{n=0}^{\infty}h[n]z{^{n}}= \frac{G}{1 -\sum_{k=1}^{p}a_kz{^{-k}}}\] show that the cepstrum of this system ...
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1answer
45 views

What does frequency weighting an acceleration signal mean? And How do I frequency weight the raw acceleration data collected?

Disclaimer: I have very little knowledge in signal processing. I'm trying to calculate a Whole Body Vibration(WBV) measure called Vibration Dose value(VDV). $$VDV = \left(\int_{0}^{T}a(t)^4\,dt\right)^...
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42 views

Frequency response of chirp signal changes when extracting burst from repeating chirp waveform

I hope i can make myself clear enough, even though i might not be familiar with the right terms. Using GNU Radio, i created a chirp signal with a sawtooth signal source into a frequency mod block, as ...
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0answers
48 views

Short Time Fourier Transform has different frequencies than Fourier Transform?

The reason we do the STFT is so that we can analyse for short segments of time how much of the components in the frequencies of the FT are present. However, it may be possible that completely ...
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2answers
57 views

Periodicity of complex exponential in continuous and discrete time (Eq 1.51, Signals and Systems by Oppenheim & Wilsky)

Hi All: This is very basic but I've always wondered about it and now I see it in print in a textbook so I may as well ask. In Signals and Systems on page 26, it says $$e^{j(\omega_0 + 2\pi)n} = e^{j2\...
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104 views

Is there a Python method to calculate moving RMS of a signal? How to calculate the moving RMS using the discrete signal formula? [closed]

I'm trying to calculate a moving RMS of an acceleration signal. One of the answers in the post, shows the formula for calculating moving RMS for discrete signal. The formula they suggest: I have a ...
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1answer
62 views

Frequency response of a long signal

I am trying to get the frequency response of a system, so, in theory I would need to do: H = fft(y)./fft(x); I have measured the system with a long stepped sine ...
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2answers
60 views

Best temperature compensation equation?

I'm looking for the correct temperature compensation equation to use on our project. We are measuring the output of a detector who's signal is very sensitive to temperature drift. Any external ...
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1answer
34 views

How to compute dBFS from rms-values if the samples exceed 32bits

For a first approach on audio-sampling I'm currently working with the raspberry pi's pcm pins and MEMS-microphones, using the ALSA library. A problem arises when I want to calculate dBFS from a buffer'...
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1answer
59 views

Output power of a signal passing through an IIR filter

suppose I have the following discrete time signal $x\left(n\right)=0.7\sin\left(2\pi \times 623\:nT\right)$ where $N=4000$ and $T=\frac{1}{f_s}$, where $f_s=40$ kHz I pass this signal through a simple ...
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1answer
33 views

Time scaled version of discrete time signals

I have a confusion regarding time scaling of discrete time signals. Let u[n] be the discrete time unit step signal(or sequence) Now if i plot u[n/3] i know there will be two zeros added between each ...

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