understanding the physics of coupling in a aparture coupled patch antenna

Thread Starter

yef smith

Joined Aug 2, 2020
333
Hello, i have read the following article and i have a basic missunderstanding regarding imagining the physics of coupling in such case.
i know from coupler that as two lines here are closer then we have stronger coupling.
so in this case we need to tranfer the maximal amount of energy from the line to the patch.

in the article they dont specify
1.the role of the substrate height
2.the role of substrate permitivity
3.the role of the width and legth of the slot for the coupling.
they only say ,we get good coupling for measures of such and such without getting into the reasons of why?

Why the coupling is increasing or decreasing from each case?

https://www.ijettjournal.org/volume-2/issue1/ijettjournal-V2I1P206.pdf
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Delta Prime

Joined Nov 15, 2019
1,326
Hello there :)
An an excerpt of a discussion about the basic operating principles of the aperture coupled antenna's.Microstrip antenna technology,has gone through some recent developments related to aperture coupled microstrip antennas
many possible variations in patch shape, aperture shape, feed line type, radomes, etc.
extension to aperture coupled microstrip line couplers, waveguide transitions, dielectric resonators, etc.
independent selection of antenna and feed substrate materials.
two-layer construction shields radiating aperture from feed network.
I hope it helps.
 

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Thread Starter

yef smith

Joined Aug 2, 2020
333
Hello Delta prime,I have seen this article before.
the heart of it is the list bellow.
basicly it says for each parameter GOOD ,BAD.
There is no logic regarding for example why thicker substrate results in wider bandwidth?
why thinnerfeed lines couple better?
could you please shown me the reasoning behind those two claims?
Thanks.

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Delta Prime

Joined Nov 15, 2019
1,326
Hello there :)
could you please shown me the reasoning behind those two claims?
It would be my pleasure.
I will point you in the right direction.
To design a Microstrip Patch Antenna
You need.
1)Type of substrate.
2)Shape of patch.
3) Dimension of patch
4) Feeding technique
5)Resonant frequency
6)Substrate thickness

A nylon fabric is a substrate considered among medium dielectric constant with dielectric constant 3.6. Work has been done to demonstrate the antenna fabricated using nylon fabrics.antenna resonates at 989 MHz it result in return loss of -35.42dB, directivity of 6.72dB, Gain of 6.11dB.
With the use of Duroid 6010 which is counted among the higher dielectric constant substrate i.e.10.7 used in phased array 1×4 at 1.35 GHz .
It showed optimized results .
Now If that got your attention then you're going to love this.
 

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Thread Starter

yef smith

Joined Aug 2, 2020
333
Hello Delta prime, the formulas in the article have been used to design a basic pin fed patch antenna which has very low BW.
Bellow you can see the result of the first first step.
e_r=2.2 f=10ghz h=0.787 substrate.
if i got correctly your idea ,the next step i assume is to try and build an aparture coupled microstrip antenna.

but in the POZAR structure we have two layers of dilectric with different dielectric constant.
what is the logic for choosing the dielctric constants ?
I am looking for a reason behind why exactly those dielectric constants will give us good coupling?
Thanks.

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Delta Prime

Joined Nov 15, 2019
1,326
Hello there :)
what is the logic for choosing the dielctric constants ?
I am looking for a reason behind why exactly those dielectric constants will give us good coupling?
It is application specific that is the reason behind why exactly those dielectric constants will give you good coupling it's a matter of price, efficiency & size.
Minimum size is achieved by using foam substrate but it is costlier & losses are higher in it even the efficiency is much less than other dielectric material. Maximum efficiency is achieved in roger 4350 but the size & price are the issues in it. an optimal solution is FR-4 substrate but application dependent that is...I would use fr-4 for consumer application but cannot be used for aerospace.
And that is for naturally occurring materials wait until you get into meta materials "man-made" research institutions, are developing patch antennas that will blow your mind.
IEEE Transactions on Antennas and Propagation, vol. 56, no. 6, pp. 1648–1655, 2008
D. M. Pozar, “A reciprocity method of analysis for printed slot and slot coupled microstrip antennas”, IEEE Trans. Antennas and Propagation, vol. AP-34, pp. 1439-1446, December 1986.
D. M. Pozar, “Analysis of an Infinite Array of Aperture Coupled Microstrip Patches”, IEEE Trans. Antennas and Propagation, Vol. AP-37, pp. 418-425, April 1989
 

Thread Starter

yef smith

Joined Aug 2, 2020
333
Hello Delta prime,from slot theory i know that the feed need to be quurter wave long from the slot to get constructive interference.
but in fact this is not the case in real simulation.
is there a way by looking at the fields that we can see the we dont have yet constractive interference?


Also ,Is there a way by looking at the field of the aparture fed patch antenna that i can see with my own eye that
for example
1. i need to decrease the substrate of the patch
2.i need to increase the length of the slot
3.i need to move the location of the slot.
is there a way by looking at the field so i could get to these conclutions ?

If you want i could show you the fields from my simulation so you can tell me how to interpret them for the purposes above.
 
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Delta Prime

Joined Nov 15, 2019
1,326
Hello there :)
If you want i could show you the fields from my simulation so you can tell me how to interpret them for the purposes above.
I just wanted to hit this thread, not marry it!
Just kidding. Go ahead show me the fields from your simulation & everything else pertinent to the topic at hand.
 

Thread Starter

yef smith

Joined Aug 2, 2020
333
Hello delta prime ,the photo bellow shows the gap coupled cut plane structure.
By the slot theory the feed line needs to be quarter wave long to make the wave going from the feed to have constructive interference with the slot wave.
but in reality i just sweep on both of their length to get the maxinaml amount.
Is there a way to see in the currents bellow if we need to increase the feeder size t get the constructive interference?
Thanks.


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