I would like to use antenna diversity with Si446x transceiver. I use 2 wire antenna with different polarization (one vertical and one horizontal). Also, i know that these 2 antennas must be lambda/4 far each other, but i have a doubt.

This distance (lambda/4) is between the 2 antenna connection points with the PCB or between the 2 middle points of the wire antennas?

Thanks!

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For the possible best diversity gain it is even better if you could ensure lambda/2 distance between the antennas.

This distance should be measured between the main radiators of antennas. This could be the mid-point of the monopole-type antenna part perpendicular to the GND plane.

Correct Answer

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Thanks for the reply.

Ok for Lambda/2, but if the device must be as small as possible, for me it is better use lambda/4 as distance.

Excuse me but I don't understand your second opinion.

I have to find the points that are the perpendicular points of each antenna on the GND plane, and the difference between these 2 Points must be lambda/4 (or lambda/2)?

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1. OK - understood the space limitations that drive the selected distance between the antennas. It is recommended to maximize it as much as you can until lambda/2. Lambda/4 is the min recommended distance.

2. You have to find the main radiator parts of the antennas, and then the distance between them should be kept as lambda/4...lambda/2. For a monopole-type antenna, the main radiator part is the one which is perpendicular to the GND plane.

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1. So, i can choose a value between lambda/4 and lambda/2, but if it is closer to lambda/2 it is better.

2. Ok.. ad example, in the picture, this distance that must be closer lambda/4 is the distance D.. is it right?

Approximately. However, this figure doesn't differ much from the previous one. The red points can slightly move closer to each other as shown in the previous figure and thus D can be a bit shorter.

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Ok, i repost the figure previous one and I zoom the interested zone.

## antenna diversity design with Si446x

Hello everyone!

I have a little problem and i ask help.

I would like to use antenna diversity with Si446x transceiver. I use 2 wire antenna with different polarization (one vertical and one horizontal). Also, i know that these 2 antennas must be lambda/4 far each other, but i have a doubt.

This distance (lambda/4) is between the 2 antenna connection points with the PCB or between the 2 middle points of the wire antennas?

Thanks!

For the possible best diversity gain it is even better if you could ensure lambda/2 distance between the antennas.

This distance should be measured between the main radiators of antennas. This could be the mid-point of the monopole-type antenna part perpendicular to the GND plane.

Thanks for the reply.

Ok for Lambda/2, but if the device must be as small as possible, for me it is better use lambda/4 as distance.

Excuse me but I don't understand your second opinion.

I have to find the points that are the perpendicular points of each antenna on the GND plane, and the difference between these 2 Points must be lambda/4 (or lambda/2)?

1. OK - understood the space limitations that drive the selected distance between the antennas. It is recommended to maximize it as much as you can until lambda/2. Lambda/4 is the min recommended distance.

2. You have to find the main radiator parts of the antennas, and then the distance between them should be kept as lambda/4...lambda/2. For a monopole-type antenna, the main radiator part is the one which is perpendicular to the GND plane.

1. So, i can choose a value between lambda/4 and lambda/2, but if it is closer to lambda/2 it is better.

2. Ok.. ad example, in the picture, this distance that must be closer lambda/4 is the distance D.. is it right?

Ok, i understand... thanks!

But, last question, if i wanted to use wire PCB antennas, the distance D that i have to respect, is it the following,right?

Ok, i repost the figure previous one and I zoom the interested zone.

Now i think taht it is correct.