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What ANTENNA do you recommend???

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Advanced Member level 4
Jan 19, 2006
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I want to design an antenna at 915MHz on PCB (x-y plane). I want it to be omni-directional in the x-y plane.

This is a good ampplication note on small antenna
**broken link removed**

I suggest using a circular patch antenna shorted in the center to make the TM_010 mode dominant for the coverage you require. This is a simple and planar antenna.


How do you feed it? With a microstrip?

Do you have a simple drawing?

Yes you can simply feed it with a microstrip feed. You may need to use capacitive coupling to match to the impedance. I dont have a drawing but it is a very simple structure...just a circular patch shorted in the center. You can also just use a regular square patch antenna shorted in the center to create the same pattern. By shorting the center of the rectangular or circular patch antenna you are forcing the field to be zero in the center and max at the edges, thus providing you with the pattern you want. You can also look at a paper by Lai, Leong, and Itoh on a dual-mode antenna which was presented at last years asia pacfic had the pattern you are looking for.

Isn't a Yagi very seems like he/she wants a omni-directional antenna.

I have example for you


Plasma, your antenna is printed in the x-z plane and has omni directional in the x-y plane.

Savedadogs, thanks for referring me to a paper. I'm working on getting it, though it's difficult because it was presented at a conference in China, just like you said.

A. Lai, KMKH Leong, and T. Itoh
Dual-mode compact microstrip antenna based on fundamental backward wave
Asia Pacific Microwave Conference

You are also correct in that I'm looking for an omni-directional antenna.

I'm going to simulate an antenna based in the circular structure you described previously.

The results are below. The first plot is an x-y slice at theta = 90 degrees (E phi plane). I used a pcb thickness of 1.6mm. The radiation pattern isn't really what I'm looking for. Maybe I don't understand your description of the fixed antenna. I know that if you use an antenna that is fixed off the pcb by 7 to 10 mm then you can get an omni directional pattern, but that isn't a simple pcb printed antenna. Is that what you are talking about?

I got the paper. Hopefully the author doesn't mind.


try changing the scale of your graph to log and also change the range to maybe 40dB.


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