# Search results

1. ### How to calculate pulse energy?

The pulse laser is converted by photo detector(PD) into electrical current. And we can see output voltage of photo detector by using oscilloscope. Now we get voltage function detected by PD. Now I need to calculate energy of pulse. But I don't know how I do it.. Is there any formula I can use??
2. ### What is the maximum or Nyquist frequency of a Gaussian signal?

How cna I choose Fs high enough when no upper frequency limit?? Is there any criterion in signal processing??
3. ### What is the maximum or Nyquist frequency of a Gaussian signal?

I can't understand why max freq is 5Ghz. Do you mean that value corresponding freq lower at about 5Ghz is close to 0???
4. ### How to write BB codes in this forum?

Hello. I want to show like this not I tried [PYTHON], [Python], [ CODE](Python), etc. But They weren't run. How can I display my programming language?
5. ### Python Output of sympy.fourier_transform

I run sympy.fourier_transform. from sympy import fourier_transform, exp,symbols from sympy.abc import x, k a=fourier_transform(exp(-x**2), x, k) s=symbols('s') Ori=(s)*exp(-(x**2)/(s**2)) FT=fourier_transform(Ori,x,k) a.subs({k:1}).evalf()...
6. ### What is the maximum or Nyquist frequency of a Gaussian signal?

Hello. I'm studying Fourier analysis. If we look at attached graph where Gaussian functions are transformed by Fourier analysis, we can find Gaussian functions in frequency domain have maximum value at 0 hertz. So I confused what is the Nyquist frequency at Gaussian signal. I need to know...
7. ### Energy calculation by using Parseval's theorm

Sorry to my expression. I didn't know how to write LATEX letter. When x(t) represent voltage, E = ## \int x(t)^2 \, dx ## = ## \int X(f)^2 \, df ## by definition of Parsevals' theorm, But when x(t) represent power, I wonder if E = ## \int x(t) \, dx ## = ## \int X(f) \, df ## or not. X(f)...
8. ### LaTeX I want to use LaTeX, How can I do that?

## \left( \frac a b \right) ## Thank you. I got it!!
9. ### LaTeX I want to use LaTeX, How can I do that?

Could you kindly give me specific detail?? I can't find proper information about LaTeX in the link you said.
10. ### LaTeX I want to use LaTeX, How can I do that?

I want to write LaTeX. So I write e.g) '\left( \frac a b \right)' . But it looks just back space bar not mathematical equation. Does there need to install TeX program if I want to type LaTeX in Physics Forums???
11. ### Energy calculation by using Parseval's theorm

Then, in Parseval's theorm, E= integral x(t) square dt = integral X(f) square df. But if x(t) represent 'power integral x(t) dt'= energy as you said. I wonder when x(t) represent power, if 'integral x(t) dt' = 'integral X(f) df' or not.
12. ### Energy calculation by using Parseval's theorm

Homework Statement In Parseval's theorm, energy equals integral x(t) squre when x(t) represents voltage. I wonder if x(t) represernts power, then does integral x(t) dt equal energy?? Because 'power multiplied time' means energy. Homework Equations The Attempt at a Solution
13. ### Fourier transform of a power signal or a voltage signal

Homework Statement By using fourier transform, I want to calculate power of signal. I confuse that f(x) in attached equation represents voltage or power. Is that possible when f(x) means power to use fourier transform. Homework Equations The Attempt at a Solution
14. ### Parseval's theorm

you mentioned it doesn't matter that signal x(t) represents voltage or power. But I can't understand if x(t) represent power, this equation doesn't make sense as I think. In my opinion, How can power^2 be just power?? Unit of dimension is not same as I know.
15. ### RF pulse detection with Power Detectors

I have a Gaussian like shaped pulse waveform. It has 0.3ns pulse width, and it means 1.45Ghz half-band width in my calculation. If signal has 13dBm then what is output voltage from power detector? Is this enough information to calculate output or not? It's ok if I could get approximate value.
16. ### Definition of isolation and pulse response time for a 3-way power splitter

Thank you. I absolutely understand about pulse response time. But I still have two question. 1.What does isolation between output ports 1 and 2 mean? Is ratio of isolation between port 1 and port 2? Would you kindly explain me isolation 1-2?? I know isolation mean -10log(Pout/Pin). But I...
17. ### Definition of isolation and pulse response time for a 3-way power splitter

Thank you for your answer. But I have three questions. 1.What does isolation 1-2 in the data sheet??? I can't catch meaning of number(1-2). 2.What happen if isolation becomes higher or lower?? 3.Does fast response on falling edge mean small number of fall time? If I want to get low power...
18. ### Parseval's theorm

Homework Statement In parseval's theorm, what is type of x(t)?? I mean.. is this voltage wave? or power wave? Homework Equations The Attempt at a Solution
19. ### Definition of isolation and pulse response time for a 3-way power splitter

I will use 3 way power splitter and power detector. 1. This is power splitter data sheet. In this data sheet, there are different isolation values. What does it mean?? Also in that point, I wonder definition of isolation at power splitter. 2. This is power detector data sheet. In this data...
20. ### RF pulse detection with Power Detectors

I'm studying how to catch pulse width without oscilloscope. Unknown pulse is from Q-switched laser which has a symmetric Gaussian-like shape. If a pulse is sinusoidal wave form, the problem becomes quite simple. I can find exact frequency because Fourier transform of sinusoidal wave form has...
21. ### RF pulse detection with Power Detectors

How can I use power detectors for RF pulse detection? RF pulse has a symmetric Gaussian-like shape. Is the output of power detectors continuous line or point?