Author Topic: ceramic antenna?  (Read 1769 times)

sluramod

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ceramic antenna?
« on: March 25, 2016, 01:58:32 PM »
Hello,

I would like to put moteino outdoors in a sealed plastic enclosure. I'm clueless about antenna designs, and was wondering if somebody can help.

I found this antenna: http://www.vishay.com/docs/45208/vj5601m915mxbsr.pdf which is ceramic and small. Do you think it might work?

Thank you,
Alex

TomWS

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Re: ceramic antenna?
« Reply #1 on: March 25, 2016, 02:27:42 PM »
Hello,

I would like to put moteino outdoors in a sealed plastic enclosure. I'm clueless about antenna designs, and was wondering if somebody can help.

I found this antenna: http://www.vishay.com/docs/45208/vj5601m915mxbsr.pdf which is ceramic and small. Do you think it might work?

Thank you,
Alex
Here's another one to check out: http://www.mouser.com/ProductDetail/Yageo/ANT1204LL05R0915A
This is smaller and has a higher gain.  I just included this in a design, mostly to test, but hoping to keep an inside unit smaller.

The difficulty with these antennae is the amount of clear space and ground plane you need on your PCB.  The net result, if you want max performance, might be an antenna that takes more volume overall.  Most of my outdoor motes use a single 1/4Wave dipole (AKA straight wire) with a small hole in the enclosure sealed with silicone.  You'll get good gain and, unless it's mounted where the landscaper likes to chew it up with the weed whipper, they last longer than any mote I've had.  It's also a lot cheaper!

Tom

john4444

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Re: ceramic antenna?
« Reply #2 on: March 25, 2016, 02:32:35 PM »
Hi Alix,
I almost missed Tom's reply.
+1 for all his comments.
I also noticed on the datasheet that you may need additional components to make it work properly.

Were you going to add another PC-board with this antenna on it?

John
John AE5HQ

sluramod

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Re: ceramic antenna?
« Reply #3 on: March 25, 2016, 08:46:48 PM »
I was thinking just making another pcb just for the antenna. From what I understand antenna from my original post requires 40mm x 40mm pcb, the other one is 40mm x 75mm.

I noticed there is a new board with trace antenna in the works: https://lowpowerlab.com/blog/2016/02/01/moteinomega-with-trace-antenna/ so maybe I'll just wait.

Alex

TomWS

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Re: ceramic antenna?
« Reply #4 on: March 26, 2016, 04:39:59 PM »
Hi Alix,
I almost missed Tom's reply.
+1 for all his comments.
I also noticed on the datasheet that you may need additional components to make it work properly.

Were you going to add another PC-board with this antenna on it?

John
I think the additional components are the matching network that may already be on the RFM69 board.  Assuming you don't totally detune the antenna with your layout then you may not need these. 

Suffice it to say, ANY implementation in an enclosure smaller than the ideal is going to affect performance.  The good news is that the RFM69 has a lot of 'room' to spare in this department and, as long as you're not trying to get 100s of meters of range, it just may be good enough, especially since it's ceramic.

Tom