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question on electrical length in basic patch antenna

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Alex329

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Hi,

I am designing a basic patch antenna. Therefore, in the patch antenna we must use a microstrip transmission line. When I calculate the dimensions of that microstrip transmission line, should I use the electrical length of 180 degree for the best results or less that 180 degree? Because when I use 180 degrees it gives me dimensions of microstrip equal to L=106mm and W=7.7mm. For my design, the length of 106mm is too much because I would like to have the substrate dimensions of around 120mmx120mm or less. How to know the best electrical length that I should use in that case(90 degree, 45 degree....)?

Thank you
 

Romansh

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If you are talking about the feed of the antenna and it is not part of the matching network, then the length doesn't matter as long as it is 50Ohm TL.
 

Alex329

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If you are talking about the feed of the antenna and it is not part of the matching network, then the length doesn't matter as long as it is 50Ohm TL.

What do you mean by if " it is not part of the matching network" ? It's an antenna like this one "https://www.researchgate.net/figure/276353525_fig6_Figure-26-Microstrip-patch-antenna-with-inset-fed". In this case do we consider it as a part of the matching network?
 

Romansh

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Well, if you noticed there are different types of feeding shown on these pictures. Usually, once the TL becomes 50 Ohm the lengths is not critical. Anyway, you need to simulate in 3D the whole structure.
 

vfone

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Because in the real life at high frequencies there are no ideal transmission lines, the microstrip TL that feeds the antenna SHOULD be part of the antenna impedance match.
I mean, you design the circuit PCB layout, draw the microstrip line that feeds the antenna (with whatever length), and AFTER that design/tune the antenna impedance matching network.
 
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