convolution

  1. H

    I What type of convolution integral is this?

    Convolution has the form (f\star g)(t) = \int_{-\infty}^{\infty}f(\tau)g(t-\tau)d\tau However, I for my own purposes I have invented a similar but different type of "convolution" which has the form (f\star g)(t) = \int_0^{\infty}f(\tau)g(t/\tau)d\tau So instead of shifting the function g(t)...
  2. A

    Trying to intuit the unit impulse response

    1. Homework Statement Hi there, I've been trying to gain some intuition on how the convolution sum works, but as I dig deeper I am realizing that there is an issue with my intuition of signals and systems, in particular the unit impulse response. My issue is trying to understand how a unit...
  3. jsg94

    Determine impulse response given input and output signals

    1. Homework Statement Hello everyone, In the following problem I have to find the unknown impulse response g1(t) given the input and output signals, as shown below: (the answer is already there, at the moment I am trying to understand how to get there). 2. Homework Equations I have...
  4. G

    General solution for the heat equation of a 1-D circle

    1. Homework Statement Modify the initial conditions (for the diffusion equation of a circle) to have the initial conditions ## g(\theta)= \sum_{n=-\infty}^{\infty}d_{n}e^{2\pi in\theta} ## Using the method of Green's functions, and ## S(\theta,t)= \frac{1}{\sqrt{4\pi...
  5. redtree

    I Independence of variables in Convolution

    Given a convolution: \begin{equation} \begin{split} g(x) * h(x) &\doteq \int_{-\infty}^{\infty} g(z) h(x-z) dz \end{split} \end{equation} Do ##z## and ##x## have to be independent? For example, can one set ##x=z+y## such that: \begin{equation} \begin{split} \int_{-\infty}^{\infty} g(z)...
  6. Q

    Mathematica Mathematica: Convolution Integral

    Hi all! I'm new to Mathematica. I have written a code for performing a convolution integral (as follows) but it seems to be giving out error messages: My code is: a[x_?NumericQ] := PDF[NormalDistribution[40, 2], x] b[k_?NumericQ, x_?NumericQ] := 0.0026*Sin[1.27*k/x]^2 c[k_?NumericQ...
  7. G

    Laplace transform of derivative of convolution

    Prelude Consider the convolution h(t) of two function f(t) and g(t): $$h(t) = f(t) \ast g(t)=\int_0^t f(t-\tau) g(\tau) d \tau$$ then we know that by the properties of convolution $$\frac{d h(t)}{d t} = \frac{d f(t)}{d t} \ast g(t) = f(t) \ast \frac{d g(t)}{d t}$$ Intermezzo We also know that...
  8. kaniello

    I Convolution integral

    Dear "General Math" Community, my goal is to calculate the following integral $$\mathcal{I} = \int_{-\infty }^{+\infty }\frac{f\left ( \mathbf{\vec{x}} \right )}{\left | \mathbf{\vec{c}}- \mathbf{\vec{x}} \right |}d^{3}x $$ in the particular case in which f\left ( \mathbf{\vec{x}} \right...
  9. R

    Convolution of two Sinc functions

    1. Homework Statement Calculate the convolution of ##sinc(at)## and ##sinc(bt),## where ##a## and ##b## are positive real numbers and ##a>b.## 2. Homework Equations Convolution integral 3. The Attempt at a Solution The fact that ##a>b## tells us that the graph of ##sinc(at)## is ##a-b##...
  10. Summer95

    The Dirac Delta Function

    1. Homework Statement Differential equation: ##Ay''+By'+Cy=f(t)## with ##y_{0}=y'_{0}=0## Write the solution as a convolution (##a \neq b##). Let ##f(t)= n## for ##t_{0} < t < t_{0}+\frac{1}{n}##. Find y and then let ##n \rightarrow \infty##. Then solve the differential equation with...
  11. R

    Convolution Calculation (piecewise function)

    1. Homework Statement Compute the convolution ##(f*h)(t)## where $$f(t) = \left\{\begin{matrix}1, \ \ for \ \ |t|<1 \\ 0, \ \ \ \ otherwise \end{matrix}\right.$$ and $$h(t) = \left\{\begin{matrix}2|t|-1, \ \ for \ \ |t|<1/2 \\ 0, \ \ \ \ otherwise \end{matrix}\right.$$ 2. Homework...
  12. R

    Convolution and Transfer Function

    1. Homework Statement The impulse response ##h(t)## of a linear time invariant system is real valued. Where * denotes the complex conjugate, the transfer function satisfies: $$H(- \nu) = H^* (- \nu)$$ Use this result to show that for such a system, given the input ##f(t)= \sin(2 \pi \nu...
  13. R

    Convolution Integral Properties

    1. Homework Statement Either by using the properties of convolution or directly from the definition, show that: If $$F(t)=\int^t_{-\infty} f (\tau) d \tau$$ then $$(F * g) (t) = \int^t_{-\infty} (f * g) (\tau) d \tau$$ 2. Homework Equations The convolution of ##f## with ##g## is given...
  14. J

    Is there a mistake in my calculation or in my reasoning?

    1. Homework Statement y'' + 3y' + 2y = r(t), r(t) = u(t - 1) - u(t - 2), y(0) = y'(0) = 0. I need to solve this by convolution, which I know is commutative. The problem is that my calculation gives (f * g) =/= (g * f). Could someone please tell me where my mistake is? 2. Homework...
  15. E

    Fourier Transform and Convolution

    Considering two functions of ##t##, ##f\left(t\right) = e^{3t}## and ##g\left(t\right) = e^{7t}##, which are to be convolved analytically will result to ##f\left(t\right) \ast g\left(t\right) = \frac{1}{4}\left(e^{7t} - e^{3t}\right)##. According to a Convolution Theorem, the convolution of two...
  16. Italo Campoli

    Inverse Laplace Transform of a fractional F(s)

    1. Homework Statement Having a little trouble solving this fractional inverse Laplace were the den. is a irreducible repeated factor 2. The attempt at a solution tryed at first with partial fractions but that didnt got me anywhere, i know i could use tables at the 2nd fraction i got...
  17. wirefree

    Integration by sketching

    I greatly appreciate this chance to submit a query. I have the following integral: $$\int_{1}^t 2sin(t-\tau)e^{-2(t-1)} d\tau$$ and it has been suggested to me that if I sketch the two constituent functions and multiply them, I can read the answer off the paper. So here are my sketches: go...
  18. E

    Step Validity with the Fourier Transform of Convolution

    A convolution can be expressed in terms of Fourier Transform as thus, ##\mathcal{F}\left\{f \ast g\right\} = \mathcal{F}\left\{f\right\} \cdot \mathcal{F}\left\{g\right\}##. Considering this equation: ##g\left(x, y\right) = h\left(x, y\right) \ast f\left(x, y\right)## Are these steps valid...
  19. T

    Use convolution integral to find step response of a system

    1. Homework Statement An electrical network has the unit-impulse response :h(t)=3t⋅e-4t .If a unit voltage step is applied to the network, use the convolution integral to work out the value of the output after 0.25 seconds. 2. Homework Equations Convolution integral: y(t)=f(t)*h(t) Unit step...
  20. Th3HoopMan

    Correlation between Iterative Methods and Convolution Codes

    Hey guys so I have this Calc 3 project and the end is throwing me for a loop. I've done the encoding part, and i've coded the standard iterative methods, but I don't see how the two correlate so I can use the iterative methods to decode a "y stream" with the inputs specified...
  21. E

    Convolution Dirac impulse and periodic signal

    Hi ☺️ i have to do a convolution with a periodic signal and a dirac impulse: x(t)=sen(πt)(u(t)−u(t−2)) h(t)=u(t−1)−u(t−3) The first is a periodic graph that intersect axis x in points 0 , 1 and 2 (ecc) The se ing is a rectangle ( Dirac impulse ) that intersect AxiS x in points 1 and 3. For...
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