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patrick0621

Q about 2.4 GHz Patch performance and impedance

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I have just build the GP Patch antenna to the exact specs on the site and used the roof flashing for the plates, when i checked the input impedance it wasnt 50 ohms. At 1.2 GHz it was 29ohms and at 2.4 GHz it was slightly lower but with a higer capacitive impedance. The antenna actually worked at 1.2 GHz much better than for the listed 2.4 GHz. Testing was done on an antenna analyzer piece of equipment used in the electrical engineering department of the university i attend.

Has anyone had any problems matching the impedance on the patch antennas they have build?

Thanks

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The antenna actually worked at 1.2 GHz much better than for the listed 2.4 GHz. Testing was done on an antenna analyzer piece of equipment used in the electrical engineering department of the university i attend.

If the network analyzer shows it has better performance at 1.2GHz then something is wrong with the antenna, analyzer, or setup.

As a sanity check, compare its 2.4GHz RF gain with a standard dipole antenna with known gain. This is a easy measurement to make. Keep in mind that nearby objects, including your own fleshy body, will affect the measurements. So, be careful of such things during your tests; With microwave RF, everything matters.

Below is a screenshot of what I mean. I used a A/V Tx for the signal source (located about 10 feet away). The plot shows the GPP's gain relative to a 2.4GHz 3dBi ducky. It was a challenge to take the photo, since just getting anywhere near the instrument caused the gain to drop several dB. I had to use zoom and lay close to the floor, a few feet away from the SA.

The snapshot is merely to show that you should see more gain from the GPP than from a typical dipole or 1/2 wave vert whip. I did not have the patience (read: not enough free time) to squeeze out every drop of gain during the measurement setup to show the maximum additional gain. That fact that it shows it as being higher was enough for this example.

post-2-1208552653_thumb.jpg

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