Understanding Laplace Transform's Spectrum of Damped Sinusoids

In summary, the Laplace transform pair consists of the Heaviside step function and its spectrum of damped sinusoids. The spectrum is weighted towards low frequencies, following the relationship of 1/abs(s) going to zero as abs(s) goes to infinity. This is expected for an excitation that begins but is never turned off. The spectrum of damped sinusoids comes from mapping s to jω and the amplitude of each component sinusoid being inversely proportional to its frequency.
  • #1
muzialis
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Hi All,

in a previous post on the physical meaning of Laplace's Transform I found the following statement
" The fundamental Laplace transform pair is H(t), the Heaviside step function, and 1/s, its spectrum of damped sinusoids. Note that the spectrum is weighted towards low frequencies (1/abs(s) goes to zero as abs(s) goes to infinity), as one would expect for an excitation that begins but is never turned off".
I am struggling to understand where the spectrum of damped sinusoids comes from, I found this interesting.
Can anybody maybe help?
Thanks a lot
 
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  • #2
muzialis said:
I am struggling to understand where the spectrum of damped sinusoids comes from, I found this interesting.
I interpret it thus:

Bear in mind that to relate a Laplace transform back to the frequency (sinusoid wave) domain, we map s → jω.

So 1/s → |1/ω| in magnitude, meaning amplitude of each component sinusoid is inversely proportional to its frequency.

Beyond this, I can't say much more.
 
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1. What is a damped sinusoid in relation to Laplace transforms?

A damped sinusoid is a type of signal that is characterized by a sinusoidal shape with a decrease in amplitude over time. In Laplace transforms, damped sinusoids are used to represent signals that decrease in amplitude over time, such as signals in a damped harmonic oscillator system.

2. How is the Laplace transform used to analyze the spectrum of damped sinusoids?

The Laplace transform is a mathematical tool that is used to convert a function in the time domain to its equivalent representation in the frequency domain. By applying the Laplace transform to a damped sinusoid, we can analyze its spectrum and determine the frequency components present in the signal.

3. What is the significance of the poles in the spectrum of damped sinusoids?

The poles in the spectrum of damped sinusoids represent the frequencies at which the signal has its maximum amplitude. These frequencies are also known as the resonant frequencies of the system.

4. How does the damping factor affect the spectrum of damped sinusoids?

The damping factor is a parameter that determines the rate at which the amplitude of the damped sinusoid decreases over time. A higher damping factor results in a faster decrease in amplitude and a wider spread of poles in the frequency domain.

5. Can the Laplace transform be used to analyze non-linear damped sinusoids?

Yes, the Laplace transform can be used to analyze non-linear damped sinusoids. However, the analysis becomes more complex as the non-linearities in the system can result in a more complicated spectrum with additional frequency components.

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