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# Slotted microstrip patch antenna array

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#### mburakbaran

##### Member level 2
Hi everone,

Firstly, I'm new in antenna design.

I'm trying to design 2x2 square microstrip patch antenna array with HFSS 12.1.2. W=L is about 28mm.

I'm opening 10mmx1mm slots to each square in order to realize some kind of a circular polarization (Balanis). Each Slot are opened on the diagon of the square.

Operating frequency is 2.45 Ghz. I'm using FR4 which is 1.6mm. I'll feed the circuit from middle of the substrat with a via.

In order to match circuit, I'd like to know each square's input impedance.

For a simple square, I'm using the formula of 90*epsilon_r^2/(epsilon_r-1)*(L/W)^2 from the book of Stuttzman where L=W since it's a square.

1. But what about after opening the slots? The impedance must change, right? If so, how can i calculate it? Or basically, how can i simulate any antenna's input impedance? Z(1,1) shows something but, there is the transmission line, too. How can i learn antenna's impedance only?

2. I got about 2.2 dB from a single patch (FR4 is very lossy, 0.02 tangent loss). What should I expect for 2x2 array? Also, directivity is 7.3dB.

3. For circular polarization check, I must look at RE_x, RE_y vs frequency, and expect at most 3dB difference right?

4. For radiation boundary, I'm going up from the substrate about lambda/4, and going down lambda/10 from the substrate. And leaving some portion from the sides of the substrate too. Am I doing right, cause if I dont do it so, Totalgain drops.

Thank you very much all.

hi dear
u write many thing here but u did not talk about u problem

I beg your pardon, but cant you see that there're several questions (which I also gave numbers) in the text I wrote?

hi dear
u write many thing here but u did not talk about u problem

For question 3 about the CP check, i was told to check the axial ratio vs frequency, if it is below 3 dB then you got CP. Any comments?

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