panel antenna; learn by destroying; Kenneth, what is the frequency?

OK, I didn't destroy this panel antenna. I managed to rip off the radome and should be able to glue (RTV) it back together.

The patches measure 70.5mm x 61mm. They are spaced center to center by

122mm. The first matching network measures 25mm x 13.5mm. The second matching network measures18mm x 8mm.

I have a manufacturer's datasheet of sorts that based on overall dimension lets me narrow down the frequency range to two bands. However, it might be more entertaining not to give the two choices first.

Reply to
miso
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How thick is the G10/FR4 PCB material? How high off the ground plane? Are the screws in the center of each patch grounded? Any traces on the back side of the PCB?

I use hot melt glue to hold things together. Very easy to remove with a heat gun.

Do I get a prize?

Actually, I'm having problems finding a calculator suitable for a patch antenna with the center grounded and edge fed. It's easy with just edge fed:

but not with the center ground.

Reply to
Jeff Liebermann

Oh, you really want me to destroy it. I was hoping someone could tell by the spacing of the elements. Your reward is you get to be uber geek of alt.internet.wireless. I could leave my voice on your answering machine, which is the stock prize for "Wait Wait Don't Tell Me.'

Here is another clue:

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Exterior dimensions are in the 250mm x 250mm category, so there are only two possibilities.

Everything is a short at DC. That is, across the N connector, you read a short. However, I think the design is such that the back of the case is a ground plane. The PCB sits about 6mm above this ground plane on foam. Lifting up the edge of the PCB makes it appear to me that it is one sided. I would venture a guess that the center of each rectangle is returned to ground. So that would make this microstrip?

Reply to
miso

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this were a patch antenna, then the dimensions given come out to be

1.9G rather than the 2.5 I was hoping for. Well, a good $5 education if that is the case. i suppose as a project you could do a wifi design by replacing the PCB, but cheaper to buy an antenna.
Reply to
miso

Ummm.... no. An ohms-guesser will tell you if the center studs are grounded. A ruler will give you the PCB thickness.

Nope. That's just to get the 4 patches in phase so that the signals combine to reinforce each other, rather than cancel and produce some bizarre pattern. It's the size of the patch that's important.

I prefer cash, loose women, or old HP LED calculators. I collect all of these.

Made in Israel. Nice. Yeah, it's probably one of those.

Bingo. Then the studs are grounded as that's the only path I can see to ground.

It is.

Ok. That complicates things a bit. Two different dielectric constants. G10/FR4 is about 5.5. Open cell polystyrene foam is about

1.05. You didn't bother to supply the board thickness but I'll get 1/16" or 2mm. So, most of the dielectric is in the foam. I can't tell if the 6mm foating height is from to top or bottom of the PCB, so I'll guess(tm) that it's the bottom because it's easier to measure. I'm not sure how to calculate the combined dielectric constant so I'll just guess(tm) that it's about 1.4 with a spacing of 2+6=8mm. Note that the dielectric constant has a HUGE effect on the resonant frequency and should really be calculated rather than guessed.

Plugging the patch dimensions and dielectric constant into the calculator at:

I get 1.85Ghz. I guess it's a PCS cell phone or DECT 6 phone antenna.

Sorta. There would need to be a ground under the transmission lines and power divider in order for this to be a PCB microstrip. However, it can still be a microstrip with a composite dielectric (G10 and foam) with an 8mm spacing. There's a calculator somewhere for doing composite dielectic microstrips that I'm too lazy to find right now. (Translation: This is YOUR problem so you do the work).

Send the gratuities to the address below.

Reply to
Jeff Liebermann

The PCB is 0.8mm. I suppose I could lift the PCB and change the size of the rectangles with a nibbler to work at 2400, but the matching network I assume are stubs related to wavelength. They would be hard to change.

Still worth $5 for the entertainment.

Reply to
miso

Now you tell me.

Nope. You'll destroy it. Use it on you cell phone.

See:

I still want my prize.

Reply to
Jeff Liebermann

Prize? What shall I say on your answering machine?

Reply to
miso

Pix or it didn't happen.

berk

Reply to
berk

Cash:

Old photo of part of my HP calculator collection:

This is a family newsgroup. No photos of my loose women collection.

Reply to
Jeff Liebermann

Your bank, checking, and credit card account numbers, passwords, and sufficient identification detail to take everything.

Reply to
Jeff Liebermann

Yeah, I have a HP35, 11 (somewhere, that was the little credit card) and hp28. The HP28 still gets some action, though every time I replace the batteries I groan about the 3 N cells required, when they are sold in packs of two.

Reply to
miso

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