Electronics > RF, Microwave, Ham Radio

cheap THz experiments?

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coppercone2:
So I was trying to think of something fun and new for the next year, and I was wondering about diode detectors.

I bought castable 3d-printer resin recently, which would allow me to pour any shape I want, within reason. I see there are no problems making fancy geometry rings and such on youtube.

This makes me believe I can cast waveguide or antenna parts out of silver. Yes, somewhat expensive, but not as expensive as THz electronics. Combined with the silver-on-ceramic PCB methods that I discovered recently, it seems plausible to make some kind of circuit, i.e. a detector coupled to a horn in order to try to pick up THz emissions from a silicon carbide glo-bar source.

I also noticed that most diodes (i.e. conventional diode), is actually very small, for instance ceramic zener diodes, if you crack them open, they have something like a grain of sand sandwiched between two copper cylinders. If I was careful on some lapping media I could make that diode shorter. I believe I read that even normal diodes have a rather wide bandwidth, thats not including 'shortened' diodes, or really small diodes (i.e. 0402 or smaller).

Does anyone have any inspiration for this line of projects? If I cast the right size cavity and horn could I correctly position a modified diode to make a reasonable THz detector?

I am tired of being bared from this electromagnetic region because of financial reasons. I think I can make a glo-bar and I think I can make a cavity/antenna, I just need to know about the detector element in the system  :rant:

Thermal Imager/Optics forum version of thread
https://www.eevblog.com/forum/thermal-imaging/mmwaves-optical-methods/msg3929741/#msg3929741

cdev:
I am also interested in this. I have access to a back yard. I think that outdoor environments have an advantage of being fairly free of reflections. One possibility is building a robotic platform to rotate an antenna in 6DOF. and then receive the signals a bit of a distance away and detect and record the RF signal strength, and perhaps a video of the view along the antenna's primary signal axis. (showing what direction it was pointing in)

This would be extremely useful in developing antennas.

You can also use satellites as signal sources with known locations.

coppercone2:
Yeah, I am pretty confident it can be made. I think someones post somewhere on this site said common diode had like response to 90GHz or something. But I can't find it.

If you can cast it you don't need a multi-axis cnc machine to make the horn feed or anything like that, and its small enough so you can make it out of solid silver for not too much cost. Vacuum casting would be the best. The geometry of horn feeds is obnoxious.

Any candidates for misused diodes or transistors as detector elements? A simple power detector would be the most logical first step I think.

Joel_Dunsmore:
not to rain on anyone's parade (PS, THz don't go through rain much either), but THz is really a challenge.  I've been doing a lot of work in the D-band (110-170 GHz) and some up to 330 GHZ, and everything is hard, and fraught with trouble.  You don't need to be outdoors for antenna testing as far-field is something like 10 cm, even for a large phased array.  And you don't have to worry about re-reflections as free path loss is something like 73 dB per meter at 110 GHz.  The thing that kills anything operating at these frequencies is shunt capacitance.  The capacitance for a corner freq of 110 GHz is on the order of 30 femto-farads (0.03 pF) so smallness is definitely your friend. 

0culus:

--- Quote from: Joel_Dunsmore on December 31, 2021, 04:23:13 am ---not to rain on anyone's parade (PS, THz don't go through rain much either), but THz is really a challenge.  I've been doing a lot of work in the D-band (110-170 GHz) and some up to 330 GHZ, and everything is hard, and fraught with trouble.  You don't need to be outdoors for antenna testing as far-field is something like 10 cm, even for a large phased array.  And you don't have to worry about re-reflections as free path loss is something like 73 dB per meter at 110 GHz.  The thing that kills anything operating at these frequencies is shunt capacitance.  The capacitance for a corner freq of 110 GHz is on the order of 30 femto-farads (0.03 pF) so smallness is definitely your friend.

--- End quote ---

What sort of equipment are you using for your work up there? If you can't share exact setups that's fine, but I'm curious what's on your bench, so to speak.

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