THz Radiation, Antennas: Need background knowledge

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Discussion Overview

The discussion centers around the use of small molecular antennas, specifically carbon nanotubes (CNTs), to produce terahertz (THz) signals for monitoring biological activity. Participants explore foundational knowledge in antenna design, THz radiation, and related fields such as chemistry and electrical engineering, while expressing concerns about the complexity and depth of the required background knowledge.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant seeks references to build a solid foundation in topics related to THz radiation, antenna design, and spectroscopy.
  • Another participant questions the focus on THz frequencies, suggesting that existing systems operate effectively in the MHz to GHz range.
  • Concerns are raised about the feasibility of using CNTs for THz signal generation, including issues related to THz noise in biological systems and the power output of CNT antennas.
  • Some participants suggest that a deeper understanding of antenna theory and additional study may be necessary to tackle the proposed project.
  • There is a discussion about the potential for antennas to transmit in the near-infrared/IR region, with one participant clarifying that lasers or light-emitting diodes serve that function.
  • References to specific antenna theory books, such as those by Kraus and Balanis, are mentioned as useful resources for foundational knowledge.
  • One participant shares an unrelated application of harmonic radar for tracking insects, indicating a different context for antenna use.

Areas of Agreement / Disagreement

Participants express a range of views on the complexity of the topic, with some suggesting that extensive study is required, while others emphasize the need for foundational knowledge in antenna theory. There is no consensus on the feasibility of using CNTs for THz applications or the necessary background knowledge required.

Contextual Notes

Participants acknowledge the challenges associated with THz radiation, including the need for new devices and techniques for its generation and manipulation, as well as the potential limitations of CNTs in producing sufficient signals.

pretysmitty
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I want to use small molecular - preferably CNT - "antennas" to produce THz signals to monitor activity in biological systems. After some googling, I've been reading things like "absorption spectra", "energy bands", "spectroscopy", as well as a bunch of antenna-science related jargon... I need some references that will give me a solid foundation in these topics so that I can read literature with a bit more fluency. These subject seem to span from chemistry to electrical engineering/EM physics.

Not sure where to begin; I'm concerned I'll pick a book that's too broad and waste time on background reading.
 
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Whoops. I'm a senior electrical engineering major. The most I know about optics/radiation is from Physics II and Gen Chem. Would prefer a primer on the basics of antenna design and physics/chem related to background topics for THz Radiation. I'm not sure how much quantum/Physical Electronics knowledge I need, but I recognize some stuff such as energy gaps, use of eV units, current density etc (please excuse my ignorance... it's been a while since physical electronics).

The references you suggested seem to assume a working knowledge of antennas, EM radiation etc.

Should I just pick up a general Engineering Physics Book and brush up on optics and radiation? Or are there any more specific primers you suggest?

Thanks for the input
 
pretysmitty said:
I want to use small molecular - preferably CNT - "antennas" to produce THz signals to monitor activity in biological systems.
Can you say more about why you are focusing on THz frequencies? What will be your signal generators (the antenna just couples the radiation to the far field)? There are lots of existing systems that monitor biological activity and transmit the information in the MHz to GHz region. Dealing with THz frequencies brings in lots of difficult issues...
 
One can easily (via AAV virus) attach small CNT "antennas" to neurons. The electrical impulse of the neuron should drive the nanocircuit and resonate the CNT antenna. Triangulation can then be performed to identify the precise location of the CNT.I've read that the size CNT's I need cannot produce sub-THz signals. I've also read that the THz band is naturally favored by CNTs. Also, even if a small enough CNT could produce a sub-THz signal, the wavelength would be too large to identify the precise location. Obviously, there are lots of questionable components to this idea. The biggest issues I can identify from a layman's perspective are
(1) the amount of THz noise generated by biological systems - will it drown out the CNT antenna? and
(2) the power of a signal generated by a CNT antenna: is the mV (generated by the neuron) input enough to overpower the surrounding noise? and
(3) what is the minimal bandwidth of a CNT antenna? Ideally they need a bandwidth of 1Hz (likely unfeasible)
 
Wow. That sounds to me like years of study to prepare yourself for that. More than a couple of references, I would say an additional degree.
 
pretysmitty said:
One can easily (via AAV virus) attach small CNT "antennas" to neurons. The electrical impulse of the neuron should drive the nanocircuit and resonate the CNT antenna.
That's not how antennas work. You need an oscillator or at least a very sharp transient to get the antenna to transmit any energy. Do you know the bandwidth of the electrical activity in neurons and the gaps? I'd guess it's in the kHz region or less.
pretysmitty said:
(1) the amount of THz noise generated by biological systems - will it drown out the CNT antenna?
Do you know what THz is? What in biological systems would generate THz radiation? Bioluminescence?
pretysmitty said:
(3) what is the minimal bandwidth of a CNT antenna? Ideally they need a bandwidth of 1Hz (likely unfeasible)
It would be good if you would do some reading about basic antenna theory. Antennas resonate when their physical dimensions are around the wavelength of the transmitted or received radiation. Look for Kraus or other good antenna books in your university library to get you started.
 
I see. I will definitely read the Kraus book. Also heard that Balanis is a good one.
Is it possible for an antenna to transmit in the near-infrared/IR region?
 
pretysmitty said:
Is it possible for an antenna to transmit in the near-infrared/IR region?

a transmitter/antenna for near/IR is a laser or light emitting diode
 
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  • #10
Gonna add “optics” to the list of stuff to read up on
 
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  • #11
anorlunda said:
Wow. That sounds to me like years of study to prepare yourself for that. More than a couple of references, I would say an additional degree.

I second this. It looks about as in-depth as something you'd do in the course of getting a doctorate. But that's just my uneducated guess, as I don't have a doctorate.

Also, this wiki quote doesn't make this task sound any easier.

Terahertz radiation occupies a middle ground between microwaves and infrared light waves known as the “terahertz gap”, where technology for its generation and manipulation is in its infancy.
... the generation and modulation of coherent electromagnetic signals in this frequency range ceases to be possible by the conventional electronic devices used to generate radio waves and microwaves, requiring the development of new devices and techniques.
 
  • #12
pretysmitty said:
waste time on background reading.
Beware of instant gratification - but I doubt that you would apply that philosophy to your specialty. You will surely have done a load of background reading there.
To know what it is that you actually need to know, you will need a fair bit of background knowledge; that's why professionals are needed in their field. Knowledge is a bit like advertising. If you actually knew which part is 'wasted' then you could save a lot pf time and money. Lack of knowledge could expose you to the baseless enthusiasm of equipment salesmen.
anorlunda said:
I would say an additional degree.
Yep.
Sounds to me that you need a TEAM for this exercise but I guess that could be hard to arrange.
 
  • #13
I don't know about THz frequencies but we use Harmonic Radar for tracking insects. The part on the insect is a passive reflector which re-radiates the incoming radar at a harmonic frequency.

https://newzealandecology.org/nzje/2027.pdf

Cheers
 
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