24

Can I do this circuit practically o_O? Is there any transistor or IC that can oscillate 300 THz? Can I find an inductance (coil) of 0.0025 pH and capacitor of 1 pF? Not quite, no, and no. But this is an area of active research: The Truth About Terahertz. The basic principle of the tuned LC radio emitter is resonance. The techniques for producing high ...


16

300THz transmitter? (the band between infra red and microwaves) - with a lot of technology and know how perhaps. See http://www.rpi.edu/terahertz/about_us.html 300THz transistor/IC - no. Use discrete inductors and capacitors at these frequencies? No. At very high frequencies conventional capacitors and inductors are replaced by other devices (see resonant ...


16

None of the above. All you want is Deep Red (650nm) and Deep (Royal) Blue (450nm). You do NOT want Full Spectrum, UV, IR, Far Red, Only White or anything besides Deep Red and Deep Blue. Red White and Blue is always a safe bet. Red and Blue come way before white. White (aka Full Spectrum) is more like supplemental. I do some consulting work regarding ...


13

The amount of data which you can transmit is generally determined more by the bandwidth which you are allocated than by the actual frequencies of the band. However, allocations at higher frequencies tend to be larger than allocations at lower ones. An allocation up in the GHz range might be 50 MHz wide; while the comparably sized range from 50-100 MHz is ...


8

gbulmer puts you on the right track. For the most part, "White" LEDs are nothing more than a single color LED with a phosphor on them. The phosphor takes roughly half of the light from the LED and converts it to a second frequency of light. The two frequencies of light combine in our eyes and look to be some variation of white. A power LED I have emits ...


7

It may be possible, but I don't know of practical devices that work in this fashion. If you search likely terms you'll find some work, but more along the lines of physics experiments than electronics. Transistors tend to stop amplifying at under 100GHz even for really good SiGe IC transistors. In the reverse direction, there are (sort-of) practical light ...


7

To extend horta's answer, you might want to have a look at the CREE guide to LED color mixing. As previously said, the two colors (blue and yellow) mix to create a white. This is shown below on the CIE 1931 color space: The mixed color (white) will be on a line between the two components (blue and yellow). The ratio of the intensities of blue:yellow ...


6

This answer has been edited to correct a formula and update to a more exact answer that doesn't require thinking about the antennas (credit to @tomnexus for jarring my brain in the right direction). A H field of 42 dB µA/m = 126 µA/m (in real numbers) and, given the impedance of free space is about 377 ohms, you can take the µA/m, square it and multiply by ...


6

For a band limited power spectral density \$S(f)\$ to obtain the total power all you need to do is integrate over the spectrum. In measured data the power is measured in discrete frequency steps, so despite the fact that it may show that the measurement is in dBm it is actually in dBm/Hz. The first step is to convert your power measurement into a linear ...


6

I feel for you. Been there done that. I design LED grow lights for Horticulture Research at the University of Florida. LEDs are so much more complex than one would think. So much so I am currently writing a paper titled "Understanding LEDs" There are blue LEDs and there are Royal Blue LEDs. Blue is typically around 475nm Royal Blue is typically around ...


6

The multitude of spurious frequencies in your FF transform are reflections of undersampled higher harmonics of your signal. These are aliases, as you rightfully noted. See this EDN article for better explanations. You are not using any cut-off filters on your signal, so all harmonics above the Nyquist frequency are "folded" back into the main frequency ...


5

An electro-optic modulator does what I believe you are asking about. Here's an extract from the wiki: - Electro-optic modulator (EOM) is an optical device in which a signal-controlled element exhibiting the electro-optic effect is used to modulate a beam of light. The modulation may be imposed on the phase, frequency, amplitude, or polarization of ...


5

You don't tell us anything in your profile about your level of experience or education, so I'll give a very generic answer. The best tool to start with would be a spectrum analyzer, which can tell you what frequency the system operates on, and also allows you to learn something about the overall patterns of activity, and can offer clues about the modulation ...


5

Maybe you remember the sine and cosine product formulas from high school? Replace \$a\$ and \$b\$ with \$1000t\$ and \$3000t\$ and you get a sum of new frequencies. This is also the concept used in superheterodyne radio receivers.


5

Accurately reproducing ambient EM fields inside a Faraday tent is going to be very difficult. I know you say you don't need perfection, but using a couple of antennas is probably going to be way off. An alternative and likely much easier method would be to have two tents, one a Faraday tent and the other similar looking but not - you could cover both in ...


4

We did not invent trigonometric ratios. They were already there, and we simply discovered them. I hope you aren't proposing a world where trig didn't actually work. I have no answer for that. What you will find is that all of these observations and methods are interrelated. Every time you learn of a new method, you will find parts of other methods being ...


4

If you know how to add two cosines, you can use the identity $$\cos(\alpha)\times\cos(\beta) = \frac{1}{2}\left[\cos(\alpha + \beta) + \cos(\alpha − \beta)\right]$$


3

Do you have any hands-on experience with a spectrum analyzer ? If not then maybe you should as it will give you a better understanding of the effect of changing the RBW and VBW. Ad 1) Indeed the VBW setting can be used to filter out noise and "smooth" the graph. The information is not so much "wasted" but "averaged". Most spectrum analyzers also have an ...


3

Hmm, Well there are non-linear crystals whereby you can mix "light" of different wavelengths. Search for OPA's (optical parametric amplifiers). But you have to start with light... a laser. I guess in principle you could start with 100MHz and double up to 300THz, but that's a lot of doubling :^) If I stretched your question a bit, and asked how to turn ...


3

After some research, i found that the wireless data communication over TV spectrum is made possible through the IEEE 802.22 (Super-Wifi) technology which is a Wireless Regional Area Network (WRAN) standard. It uses the white space available in the TV frequency spectrum. The interference with TV channels are prevented by means of Cognitive Radio (CR) ...


3

In principle, if your input signal is strictly band-limited, and has no content above some frequency F, then it can be perfectly reconstructed from samples taken at sampling frequency fs, if fs > 2 F. This is the Nyquist-Shannon limit. If you can perfectly reconstruct the signal, you ought to be able to find some way to perfectly identify the peaks. In ...


3

Those sidelobes are the result of the limited resolution of the data from the DSO, along with the fact that the sampling in the DSO is not precisely synchronized to the DDS output waveform, which results in a tiny amount of apparent (not actual) amplitude modulation of the actual waveform. If you oversample and apply a proper sin(x)/x reconstruction filter ...


3

You won't be able to separate the light frequencies with just an optical sensor no matter how much processing you do on the output. From your question it appears you want to build an optical spectrometer. The below is one way: There are also methods involving micromirror (DLP) technology. The idea is to optically spread out the light frequencies into a ...


3

Yours is a far better question than it may seem on first reading. The Fourier transform of a sine/cosine is a pair of Dirac's delta \$\delta\$ functions at \$\pm f_c\$. Dirac's delta function can be thought as the continuous frequency equivalent of the discrete frequency coefficients of the Fourier series expansion. The reason we mix them up in EE is ...


3

Yes, but only for killing viruses in the near vicinity. Not to use it when live people, animals are nearby. Also it would accelerate ageing of colours, plastics, wood,...Not a very clever solution, but if desperately needed could be a way to go.


3

It is useful to think of observable (real-valued) waves as the sum of two complex waves: it doesn't require a nonlinear operation to drop the imaginary part, like \$\cos x=\Re(e^{ix})\$ does. it doesn't require an (arbitrary) definition whether an observed sine wave has increasing or decreasing phase (because \$\sin x=-\sin -x\$). it explains mixing ...


2

This is too long for a comment. I also needed the extra space. Feel free to comment anything. The thing you are really asking is if the calculation is made with T/8 or T/4 or T/2. The thing is, the signal has a period of T/2, so that's the value you need to use. Now, we also need to take into account the time interval where the signal is 0. To do that, we ...


2

This is one of the reasons why (digital sampling + FFT) != spectrum analyzer. The true anwser is the spectrum analyzer. While the DSO + FFT is fine for large scale trends it can't give you detailed answers. For example looking at the plot I would guess that it is a 8 bit - 10 bit digitizer. The SA (Spectrum Analyzer) is an almost ideal low noise ...


2

For the values of ω=100 to ω=300, |H(ω)| is a straight line and you have x = ω = 100, y = |H(100)| = 16 x = ω = 300, y = |H(300)| = 24 So, solve the equation y = kx + c with the aforementioned values: 24 = k300 + c and 16 = k100 + c And you get k = 4/100 and c = 12. So, |H(150)| = (4/100) × 150 + 12 = 18 |H(200)| = (...


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