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# Questions tagged [frequency-response]

Frequency response is the quantitative measure of the output spectrum of a system or device in response to a stimulus, and is used to characterize the dynamics of the system.

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0answers
216 views

### Digital control: Exercise solution

Can you help me (show me how) to solve the following exercise? For the process with transfer function $G(s)=e^{-2s}/(s+1)$ design a digital controller with sampling time $T_{s} = 1$ that meets the ...
2answers
445 views

### How to detect the maximum resolvable spatial frequency of camera?

I am trying to calculate the minimum line pixel width that can be distinguished from noise as shown in the camera test chart in Figure 1 where the thinner lines on the left are getting more and more ...
0answers
6k views

### 1/3 octave spectra from fft

I have got a signal in frequency domain. This is a frequency response function from software, so I can do nothing about it and have to leave it in frequency domain. I want to transfer the data to 1/3 ...
0answers
284 views

### Hints and helps to implement an accurate wavelet packet transfrom

I want to implement a Time-Freqency analysis by wavelet packets. I don't know what level and sampling rate should I use. I've tried different value for level(3,4,5,6,). but I couldn't get an accurate ...
0answers
57 views

### DTFT and Eigenvalues in frequency domain

Consider an LTI system with impulse response $h[k]$. Does the frequency response $H(e^{j\Omega})$ equal the eigenvalue corresponding to an eigensignal of frequency $\Omega$? So if I convolve an ...
0answers
88 views

### Find a LTI system such that $\mathcal{T}\{\frac{\sin t}{t}\} = \frac{\sin 2t}{t}$

Let $$x(t) = \frac{\sin t}{t} \qquad\text{and}\qquad y(t) = \frac{\sin 2t}{t}$$ Is it possible to find a LTI system such that $\mathcal{T}\{x(t)\} = y(t)$? If not, what's the reason for ...
1answer
302 views

### Is it right to talk about dynamic range on frequency domain?

I'm comparing three frequency response's plots from simulations and experiments and I observed that two of them look like clamped to a DC component, where the max dB value is i.e. 100 and the min is ...
0answers
698 views

### real refractive index from Kramers Kronig relation

I have a measurement of the complex part of the refractive index $k$ (where the refractive index is $m = n + i\,k$) measured at a nonlinear grid of wavelengths or frequencies that span several orders ...
0answers
50 views

### Pure Imaginary Poles (Why is it problematic?)

Consider the LCCDE : \begin{equation} \sum_{k=0}^{N}\alpha_{k}\frac{d^{k}f(t)}{dt^{k}}=\sum_{m=0}^{M}\beta_{m}\frac{d^{k}g(t)}{dt^{k}} \end{equation} Taking the Fourier transform on both sides, we get ...
0answers
30 views

### The effect of time increment $\Delta t$, frequency resolution $\Delta f$ and Gibbs phenomenon on the amplitude of the signal in the frequency domain?

Experiment: Vibration analysis (i.e.: major concern is on transfer function or frequency response). The input is an impulse (imagine as a knocking effect or knocking force), defined as a half sine ...
0answers
52 views

### The impulse response of a LTI discrete system is $h[n]=\big(\frac{1}{3}\big)^n u[n]$. Find the response of this system to the input $x[n]= e^{jnπ/4}$

Hi I'm trying to solve the problem when studying for an upcoming test. The given solution is $1.2503 e^{jnπ/4 -0.2991}$, and is found by computing $H(Ω)$ and evaluating this at $Ω=π/4$. when I try ...
1answer
115 views

### Why does this transfer function estimation not work? System identification

Goal: I have an unknow dynmical system $G(s)$ and I want to find it from measurement data, output $y(t)$ and input $u(t)$. The data is frequency responses. Method: I begun first with creating the ...
0answers
68 views

### identifying overshoots in given state space system with step inputs

Suppose I have the following state space system: $$\dot{x}(t) = Ax(t) + Bu, \quad y(t) = Lx(t), \quad x(0) = x_0$$ where $A$, $B$ and $L$ are real matrices, $u$ is a constant real vector (so that ...
0answers
42 views

### How to eliminate audio device transfer function from recording?

I'm working on a project which requires analysis of filter transfer function of vocal tract. The vocal tract is excited by a source signal that is a frequency sweep. The source signal is provided ...
0answers
505 views

### How to filter signals with non-uniform sampling rate?

I have a digital signal that was made from analog one by staggering sampling rate: $\tau_i = \begin{cases}\tau_{even}& \text{if } i = 2n\\ \tau_{odd} & \text{if } i = 2n+1\end{cases}$ And I ...
0answers
971 views

### Matlab's invfreqs won't fit at low frequencies

I'm wondering of anyone can explain why invfreqs() is unable to fit a polynomial to the data in the image below. The red line is the measured frequency response of an analog system. I should mention ...
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 ...
0answers
22 views

### SPL dB to voltage conversion misunderstanding

base on these links: https://electronics.stackexchange.com/questions/96205/how-to-convert-volts-to-db-spl https://electronics.stackexchange.com/questions/302833/convert-digital-and-analog-values-to-...
0answers
85 views

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703 views

### How to implement a time-varying filter?

I'm working on a 10-second sound, sampled at 44.1 khz. I want to do filtering, and have a desired EQ (equalization) curve that varies over time, as suggested here (here $f0=250\ Hz$) How to ...
0answers
3k views

### How to compute transfer function (Frequency Response Function) from experimental data

I have a set of data, in the freqeuncy domain, corresponding to a structural test. I have amplitude, phase and frequency for both the measured output and the input signal (accelerations are measured ...
0answers
63 views

### Comparing vibration frequencies

I have two iron pipes, one bent and cracked, and one whole. On one end Ive attached a vibration motor (200hz) and on the other end Ive attached a vibration sensor. I do a fft and then get out the ...
0answers
199 views

### Poles and zeros from FRF

How can I determine the poles and zeros of a system given its frequency Response? I can understand how one can find the Frequency response from poles and zeros of a system. Is it possible to do it ...
0answers
290 views

### Solving linear system and find impulse response

I have this linear system that is defined by the differential equation $$y''(t) + 4y'(t) + 5y(t) = 2x(t) + 3x'(t)$$ with x(t) the input and y(t) the output. I'm asked to find two things:...
0answers
134 views