Electrical Engineering Stack Exchange
Electrical Engineering Stack Exchange

Questions tagged [spectrum]

90 questions
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Can I turn Radio waves into light?

Wikipedia says that the frequency of light is 300 THz. I've made a radio waves transmitter that transmits about 100 MHz. If I increase the frequency of the transmitter to 300 THz, will the antenna produce spark or light ? Can I do this circuit…
Michael George
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Do different frequencies have different capabilities?

I read that google was planning on purchasing a spectrum from the Fcc and they were going to use it to transfer data. I was wondering if the value of the frequency affects the data that is being transfered (ex. Higher the frequency the more data you…
Coder404
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LEDs with highly stable spectrums

We've noticed that off-the-shelf LEDs exhibit some change in the shape (and sometimes peak) of their spectrum as the amount of current flowing through them changes. For example, a UV LED we tested showed the following change in the shape of it's…
mark
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Measuring signal with of nanosecond pulse width with a spectrum analyser?

I'm looking to measure the signal width of electronic signals (device under test, DUT). The problem is that these signals have a quite short pulse width which would require me to use a GHz oscilloscope which I don't have (and can not afford at the…
ulix
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If I buy a spectrum analyser, how do I do an EMI test?

Maybe when I have the cash to buy one, I will. But my question is more related to how to use one once I've got it. I assume I'll need some kind of antenna to receive the EMI. Are there general rules for self-testing? (Before sending it off for…
Thomas O
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What could be generating this waveform in an EMC Compliance test?

We are having trouble with a CISPR-11 (EN55011) Radiated Emissions Class B compliance test in one of our solutions. The troubling part of it is basically an industrial motherboard (with a commercial SSD and commercial RAM) within a well grounded…
Javier Cambiasso
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How Is Intensity of Blue Light Measured?

As a hobby project and to help solve issues getting up early in the morning (specially given that it's winter and the sun isn't up until long after I am) I'm trying to find a bright blue light that I can put on a dimmer. I've read that the eye (even…
azoundria
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How to calculate total power from spectrum?

I'm trying to measure total power(dBm) from the following spectrum, the spectrum is 5MHz wide, the peak power from the spectrum is about -40 dBm, I have an array of spectrum points(Power vs Frequency), now my question is how do I calculate total…
SanVEE
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LED lighting with incandescent spectrum?

Is there any reason why they don't produce LED lights with a spectrum closely matching that of an incandescent bulb. Incandescent bulbs produce a nice warm light, while LEDs (even warm white ones) produce a kind of harsh light. I think it should be…
Rocketmagnet
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Why Johnson's noise is not uniform when plotted in log mode?

I have a 2 resistors of 1000 k each , I have connected them in series and biased one end with +9 V and other end with +9 V. The output is taken from connection point of two resistors and I have given that to amplifier with Gain 20000 then to…
Manjunathdm
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Sampling frequency required to detect peaks

I am processing a signal in the digital domain and I have to detect "peaks" in it, e.g. by finding local maxima formed by three consecutive values. (More sophisticated criteria could be used like setting a minimum peak height or peak width.) If I…
Yves Daoust
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How to compare brightness of different color LEDs (not RGB)?

I wonder - let's assume one would build some user interface using green, yellow and red or just any other available colored LED (not RGB LED) - what would be the proper (aka best) way to compare the brightness of LEDs in order to choose "equally…
t0bias
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How can I reproduce ambient EM fields inside a Faraday enclosure?

I am part of a research team looking at the possible effects of EM fields on psychological function. The experiment calls for participants to perform a series of tests while inside a Faraday tent that blocks most of the radio spectrum. We'd like to…
PsiProf
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Cool White LED bulbs: Are they "full-spectrum"?

I don't have much knowledge on LED lights and find the technology quite fascinating (yes, I know, it is not that new!) I have read that in order to create "white" light, LEDs actually need to emit light from all spectrums. My question(s): How do…
Phil
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Help interpreting strange spectrum

I am sampling a sinusoidal signal with an oscilloscope and viewing its spectrum using the FFT mode. The signal in time domain is this: and I am getting this spectrum: The peak above the red line is clearly the 30 kHz sine signal but, what are all…
user171780
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