# Two patch antennas gain

1. ## Two patch antennas gain

Hello all,

I have a question regarding two patch antenna array. does the distance between the patches varies the gain? (they are separated with at least lambda/2 so neglect coupling)
I think that it does not, since the far field is composed of two elements:
1. Element pattern - does not change
2. Array factor - does not change at the max since it is depend only on the number of elements.

Thanks

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2. ## Re: Two patch antennas gain

Originally Posted by chenfire
I have a question regarding two patch antenna array. does the distance between the patches varies the gain?
Yes, because the combined pattern will create side lobes as distance increases.

I created a little testcase for you:
- 2.4 GHz patch antennas with 40mm edge length
- Spacing varied from 20mm to 200mm

You can see that gain at 60mm spacing is better than gain at 100m or 200mm spacing, because of less power going to the side lobes.

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3. ## Re: Two patch antennas gain

This is a result of a simulation. I am looking for a mathematical explanation for this phenomena.

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4. ## Re: Two patch antennas gain

Originally Posted by chenfire
I am looking for a mathematical explanation for this phenomena.
Just calculate the resulting pattern from two simulataneous radiators at some offset. There is interference depending on direction, and different for different offsets. You will see the resulting side lobes that vary with distance, which mean a loss of energy in the main lobe.

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