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Patch antenna ground plane effect on radiation pattern

Patch antenna ground plane effect on radiation pattern

Patch antenna ground plane effect on radiation pattern

I used to work for a company that made electronics with GPS patch antennas in them. I currently work for a different company that makes electronics with GPS patch antennas in them. I am not an RF engineer.

I understand that a patch antenna has a radiation pattern similar to the following picture (from Wikipedia) when the patch antenna is centered over the ground plane.

It's not feasible to center the antenna in the devices I worked on, so we'd kind of shove the antenna in the corner of the PCB.

At my previous company, the RF engineers told me that the antenna pattern would be pulled in the direction of the closest ground plane edge. Thus, if I put my antenna at the "top" of my PCB, the pattern would be pulled "up". Since they were the RF engineers and I'm not, I took their word for it.

At my current company, the RF engineer (singular) tells me that the antenna pattern will be pulled in the opposite direction, that is, toward the larger ground plane area. So if I put my antenna at the "top" of the PCB, the pattern is pulled "down". His explanation basically amounts to "I'm an RF engineer and you're not, so take my word for it."

I'm looking for some actual documentary evidence that will corroborate one version or the other, so that I'm not relying on hearsay. I've found plenty of stuff online that describes the relationship between ground plane size vs. gain, but nothing about ground plane asymmetry and its effects on directivity. Does anybody know of any articles that might describe this?

RE: Patch antenna ground plane effect on radiation pattern

What size ground plane are you mounting it on and how close to the edge. In general the companies that sell GPS antennas suggest a ground plane minimum size. If the ground plane is too small, the antenna shifts frequency, and that'll kill your sensitivity much more than the patterns going askew.
At GPS, the wavelength is 11.8"/1.575ghz= 7.5". It's good to have 1 wavelength ground plane size, but half wave can work though the antenna can start to detune a bit. My company purchased a GPS antenna from a commercial source, it wasn't centered in Frequency when I tested it, even with a nice ground plane. So mounting that in a corner could really hurt it.

If you have a CCA 6" square, you could probably put it right in the corner and have a little degradation, but it wouldn't be horrific. Test it for real life answers.

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