# Tag Info

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### Significance of energy and power signals in real world

I mostly agree with @PeterK.'s answer; in practical terms, all signals are energy signals. However, a signal's energy does have important practical significance. Producing a signal of a given energy ...
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### What are the units of the product of two signals?

If the multiplier takes two voltages as input and returns a voltage as output, then there is necessarily a constant involved, with units of [1/V]. Take for example, AD633 (which was the first search ...

### Significance of energy and power signals in real world

An energy signal is defined as one with a finite energy: $$E = \int_{-\infty}^{\infty} \left|s(t)\right|^2 dt \lt \infty$$ A power signal is defined as one with a finite power or energy per unit ...
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### Is the Dirac delta (impulse) signal a power signal or an energy signal?

[Added a reference on Schwartz's impossibility theorem for products of distribution] The continuous Dirac delta $\delta$ is not considered a true function or signal, but a distribution. From its ...

### How can I get the power of a specific frequency band after FFT?

To get the total power across bins, sum the power in each bin. Also you need to compensate for your window loss if you want an accurate result. For a rectangular window, the power in each DFT bin is ...

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### Why the "20" in calculating db ratio?

According to this source, the sound power received by an aperture is proportional to the pressure squared, i.e.: $$P = \frac{A p^2}{\rho c} \cos \theta,$$ where: $P$ is the received power $A$ is ...

### What are the units of the product of two signals?

In addition to Juancho's answer for the general mixer, I would like to give an example for a more simpler frequency mixer most commonly used in communication systems to shift the frequency spectrum of ...
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### Does the RMS value of a signal yields its root-power?

Given that RMS means Root Mean Square the answer is rather obvious: it's a root power quantity. The RMS of a signal has the same units that the signal itself. Saying that "RMS is proportional to ...
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### What's the meaning of negative frequencies after taking the FFT in practice?

negative frequencies don't exist in practice, and this is just a mathematical representation? I'd say it's exactly the the opposite. Signals with only positive frequencies do not exist in nature and ...
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### Definition of average power?

The first definition works for deterministic as well as for random signals. For random signals we define the autocorrelation by $$R_x(\tau)=E\{x^*(t)x(t+\tau)\}\tag{1}$$ where $E\{\cdot\}$ is the ...

### How to determine the power of a finite signal?

First of all, note that your formula for signal power is only valid for real-valued $x(t)$ that satisfy $x(t)=0$ for $t<0$. A more general formula is P_x=\lim_{T\to\infty}\frac{1}{2T}\int_{-T}^{...