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Microwave frequencies emitter circuit

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unclejed613

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you will need an antenna that has as flat a response as possible... one of the best wideband and easiest to make antenna designs is a planar disk dipole. the diameter of each disk should be 1/4 wavelength at the lowest frequency, and the distance between the edges of the disks at the feedpoint determines the highest usable frequency, so the closer the better. disk antennas can be made from pieces of metal, or etched onto circuit board material
 

Nayldev

New Member
Thanks for the precision.

Is it this type of antenna?
88ABb08.jpg


Do I need this antenna for emission, reception, or both?
And where do I take the input or output signal?
 

unclejed613

Well-Known Member
Most Helpful Member
yes, but for 1-6Ghz u can use disks of 2.8 inches (7cm) with a feedpoint spacing between disk edges of less than 1/8 inch (3.2mm or so)

since you are testing absorption characteristics you will need a glass or low loss plastic tank with the transmit antenna on one side and the receive antenna on the other side.... each antenna being a disk dipole. it's probably best to feed the antennas with RG-214 teflon cable, and instead of running the cable across the surface of one of the disks, to feed the cable in at a 90deg angle, either sideways of from the rear side of the antenna
 
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unclejed613

Well-Known Member
Most Helpful Member
And do these dimensions also work under 1GHz?
for under 1Ghz, increase the diameter of the disks accordingly but keep the same spacing at the feedpoint.
 

Dick Cappels

Active Member
Thanks for the links!

I searched "ADF4351 evaluation board", and yes they say it generates frequency from 35MHz to 4300MHz, but I don't understand how to use it.
How to set the frequency and how do we use the output signal? Do I connect it directly to the antenna?
Do I need an Arduino? Or is there a simple way to use it?

Be careful. Wherever you live you are probably only allowed to connect a signal generator to an antenna if you are licensed by your government. In some countries you cannot connect anything to an antenna without a license (The UK comes to mind).
 

Nayldev

New Member
Be careful. Wherever you live you are probably only allowed to connect a signal generator to an antenna if you are licensed by your government. In some countries you cannot connect anything to an antenna without a license (The UK comes to mind)
I was planning to confine the system in a box that has aluminum foil on the walls
 

unclejed613

Well-Known Member
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I was planning to confine the system in a box that has aluminum foil on the walls
you will want that, but also have some RF absorptive material inside of that... or make your container so that no two shielding surfaces are parallel. one of the things about microwaves is that the wavelengths are smaller than the box you are putting your apparatus into, and so you will get standing waves in the box when the distances between two opposite walls are multiples of a quarter wavelength.. this will give a lot of cancellations and reinforcements at various frequencies that can obscure the absorption curves you are looking for.
 
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