Question About High Frequency Antennas

[Padawan]

I have an idea on how to create a capacitor with as much capacitance, or as little capacitance as I want.

 

This means I could possibly make an antenna that could go up to whatever frequency I want.

 

But, I want to know, if I increase the frequency of my antenna by using an ultra low capacitance capacitor, if the frequency is high enough will I suffer from progressive loss in efficiency?

 

Will the resistance of a high frequency current, the electrical impedance apply in this case?

 

My professor said that they have problems with microwave ovens, and their frequencies are in the Mhz region.

 

But I have heard of infrared antennas existing and being used in commercial applications.

 

So I'm wondering if I can make an antenna that will get me to the frequency I want(which is much higher than the visible spectrum).

 

Please post a response if you guys have anything knowledge concerning this field, thanks!

[YT2095]

well you may indeed be able to build a TRF front end and even get a good range of frequencies with it, but you`ll have to either Match your antenna or have some way of adjusting it`s length, else the SWR will be out and you`ll get reflected power back into your set and do electrical damage.

 

a Nice way to do it is to make an Active antenna using a Varactor for matching

[Klaynos]

IR you can do ok I believe, microwave is quite achievable.... THz, is HARD!

[YT2095]

a simple parametric amplifier should do the job quite nicely as well I reckon

[John Cuthber]

"But I have heard of infrared antennas existing and being used in commercial applications."

IR transmission and reception are easy, an IR antenna in the usual sense of the word would be news to me.

 

"My professor said that they have problems with microwave ovens, and their frequencies are in the Mhz region. "

GHz last time I looked.

 

THz is damned hard, IR, as far as I know, isn't possible. A visible frequency antenna is even more obscure yet and then I see "So I'm wondering if I can make an antenna that will get me to the frequency I want(which is much higher than the visible spectrum)."

 

Unless I have really missed something I don't see this happening. Typically antennae are about the same size as the wavelength of the radiation you are using. Just physically building something on the submicron scale is tricky. If you want to go, say 10 times further up the scale than visible light you need to build stuff that's just 70nm across. Not impossible, but hardly a home experiment, more like the cutting edge of chip making.

Then the difficult question, how do you drive it?

[YT2095]

Driving it`s the easy part! getting it Frequency stabilised is the Fun part

 

you`ll need a PLL and and VCO that`s capable of those frequencies (by at least half F), then a good freq to voltage converter and then Doubler.

 

as I said Load of Fun!

 

I think I`d just pay for a matched gunn diode and be happy with that, there`s no way I would afford all the rest of the stuff on a "Hunch".

 

 

btw, are we talking about Tx or Rx here, I gather it`s Tx were on about?

[John Cuthber]

I suspect that what we are talking about isn't Tx or Rx, but BS.

 

Incidentally, in the spirit of YT2095's idea, I should point out that if you can't get a frequency doubler, then a trebler or higher multiplier would work equally well.

[Mr Skeptic]

An antenna for EM higher than visible light? Seems to me like that would call for a molecule or atom-sized antenna. At higher frequencies the capacitance of the antenna itself would become a problem (as it is in computer chip wires at high frequencies). Why would you want a high EM antenna when you could easily use a photodetector at those frequencies?