Difference between DC/AC coupling (Antennas)

The bolometer absorber temperature is measured by thermometry.In summary, the conversation discusses an image sensor that uses micro-bowtie antennas for capturing and converting THz e.m. waves. The paper mentions two types of bowtie antennas, one directly connected to the detector and the other coupled via capacitance. The latter could provide circular polarization and a cleaner physical layout. The authors also refer to a US patent that describes a similar detector without the use of dipoles.
  • #1
marco1235
Good evening everyone!
Given that I have no experience in antenna physics or related areas, I'm studying a paper for a project I will be involved. It is an image sensor for THz e.m. waves and exploits micro-bowtie antennas to "capture" the signal and convert it through a standard CMOS imager.
Now, some clever guys developed a sensor where at each pixel they engraved 2 bowtie antennas; one orthogonal to the other (like a cross) and in two different planes within a special substrate.
According to what they wrote in the paper:

For one polarization of the THz impinging radiation, the incident wave directly excites the longer bowtie antenna named “DC (direct coupling) Antenna”. For the crossed polarization, radiation is coupled via a lower stack level antenna: “CC (capacitive coupling antenna)”.

I didn't find any explanation for this thing so I'm a little bit puzzled. If someone has familiarity with antenna-related stuff, please, I need you. ;)

Enjoy your day! Bye
 
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  • #2
marco1235 said:
Good evening everyone!
Given that I have no experience in antenna physics or related areas, I'm studying a paper for a project I will be involved. It is an image sensor for THz e.m. waves and exploits micro-bowtie antennas to "capture" the signal and convert it through a standard CMOS imager.
Now, some clever guys developed a sensor where at each pixel they engraved 2 bowtie antennas; one orthogonal to the other (like a cross) and in two different planes within a special substrate.
According to what they wrote in the paper:

For one polarization of the THz impinging radiation, the incident wave directly excites the longer bowtie antenna named “DC (direct coupling) Antenna”. For the crossed polarization, radiation is coupled via a lower stack level antenna: “CC (capacitive coupling antenna)”.

I didn't find any explanation for this thing so I'm a little bit puzzled. If someone has familiarity with antenna-related stuff, please, I need you. ;)

Enjoy your day! Bye
It sounds as if the bow tie called DC is connected to the detector directly whilst the other one is coupled via some capacitance existing in the arrangement. This might be a cleaner physical layout than connecting both directly. The capacitive coupling might also be used to introduce some phase shift, which will be needed if it is desired to obtain circular polarisation.
 
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  • #3
Mmm..very interesting..thank you so much. You helped me in understanding a little bit. For the DC coupling so far so good. For the other one, what do you mean that it could be a cleaner layout solution and that a phase shift could provide circular polarization? I don't see that thing of phase shift that you have in mind..
In any case thank you a lot. I really appreciate.
 
  • #4
I wonder if you could give a few more clues?
A link to the paper would be great, but assuming that is not possible, the names of the authors and full title would help us to search for references.
 
  • #5
marco1235 said:
Mmm..very interesting..thank you so much. You helped me in understanding a little bit. For the DC coupling so far so good. For the other one, what do you mean that it could be a cleaner layout solution and that a phase shift could provide circular polarization? I don't see that thing of phase shift that you have in mind..
In any case thank you a lot. I really appreciate.
Regarding a cleaner layout. If you try to connect two bow ties together, it is very crowded and the effect on performance is unknown. On the other hand, if If one of the bow ties is just positioned nearby and coupled via capacitance, that is easy to do.
Regarding phase shift. Suppose the DC bow tie is vertical, so it responds to vertical polarisation. Now suppose the other is horizontal - it responds to horizontal polarisation. But I imagine you would like something which responds to linear polarisation at any angle. If you connect the two bow ties together, it now responds to polarisation at 45 degrees. But if you give one of them a 90 degree phase shift, it gives circular polarisation and the array responds to any plane of linear polarisation.
 
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  • #6
Merlin3189 said:
I wonder if you could give a few more clues?
A link to the paper would be great, but assuming that is not possible, the names of the authors and full title would help us to search for references.

This is a link to the paper, but unfortunately it is not readable unless you have access to SPIE library:
http://doi:10.1117/12.974970
 
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  • #7
@Merlin3189 here also is a snapshot from the article. Hope it could help!
 

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  • #8
Very hard to work out the various layers.
 
  • #9
  • #10
Tom.G said:
See US Patent 8,513,606
This seems to describe a detector having a resistive bolometer film above a reflector but with no dipoles.
 

1. What is the difference between DC and AC coupling?

DC coupling refers to a method of connecting two electronic components or circuits without using any components like capacitors or transformers. This allows for the transmission of direct current (DC) signals. On the other hand, AC coupling involves the use of a capacitor to block DC signals and only allow for the transmission of alternating current (AC) signals.

2. How do DC and AC coupling affect antennas?

In antenna systems, DC coupling is commonly used for low frequency signals, while AC coupling is used for high frequency signals. This is because AC signals can easily pass through capacitors, while DC signals are blocked. Therefore, an antenna system may use a combination of DC and AC coupling to filter out unwanted frequencies and amplify desired frequencies.

3. Which type of coupling is more commonly used in antenna systems?

AC coupling is more commonly used in antenna systems as it allows for the transmission of high frequency signals without distortion. DC coupling is more suitable for low frequency signals and may cause distortion at higher frequencies.

4. What are the advantages of using DC coupling in antenna systems?

DC coupling allows for the transmission of a wide range of frequencies without the need for additional components. It also provides a more direct connection between components, resulting in less signal loss. Additionally, DC coupling is more suitable for low power applications as it does not require the use of amplifiers.

5. Are there any disadvantages to using AC coupling in antenna systems?

One disadvantage of using AC coupling is that it may introduce phase shifts and distortions in the signal, especially at lower frequencies. This can affect the accuracy and quality of the received signal. Additionally, AC coupling requires the use of additional components, which can increase cost and complexity of the antenna system.

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