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Antenna gain with MIMO

Hi guys,

I have a doubt about antenna gains as specified in the datasheets. Let's take the AP-315 as an example. The datasheet says the following:

AP-315/IAP-315: Four integrated dual-band downtilt omni-directional antennas for 4x4 MIMO with peak antenna gain of 3.6dBi in 2.4 GHz and 6.0dBi in 5 GHz.
- Combining the patterns of each of the antennas of the MIMO radios, the peak gain of the e ective per-antenna pattern is 3.1dBi in 2.4 GHz and 3.8dBi in 5 GHz.

What's the meaning of the second sentence? If a take 5 GHz, what value shall I consider for doing calculations about power, 6 dBi or 3.8 dBi?

Regards,
Julián

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Aruba

Re: Antenna gain with MIMO

Julian,

The first set of numbers provide the peak across all (4 or 2) antennas for each band/radio (AP-315 has 4 radio chains and antennas for 5GHz and 2 chains and antennas for 2.4GHz).

Traditionally, peak EIRP would be calculated by adding the peak antenna gain to the max conducted power and multiply this by the number of radio chains (equivalent to adding 6dB for a 4x4 radio, or 3dB for a 2x2 radio). This is ok if the conducted power is the same for all radio chains (typically true) and if the peaks for all patterns line up perfectly (in a 3D space). That is generally not the case, and in reality the peak EIRP is significantly lower.

This is why we're also specifying the peak of the combined/averaged patterns for both radios. That is the result of combining the patterns in 3D, and determining the peak of that combined/averaged pattern.

That is the more meaningful number when determining peak EIRP.

/Onno

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Highlighted
MVP Expert

Re: Antenna gain with MIMO

Hi,

 

No ideas?

 

Regards,

Julián

Highlighted
Aruba

Re: Antenna gain with MIMO

Julian,

The first set of numbers provide the peak across all (4 or 2) antennas for each band/radio (AP-315 has 4 radio chains and antennas for 5GHz and 2 chains and antennas for 2.4GHz).

Traditionally, peak EIRP would be calculated by adding the peak antenna gain to the max conducted power and multiply this by the number of radio chains (equivalent to adding 6dB for a 4x4 radio, or 3dB for a 2x2 radio). This is ok if the conducted power is the same for all radio chains (typically true) and if the peaks for all patterns line up perfectly (in a 3D space). That is generally not the case, and in reality the peak EIRP is significantly lower.

This is why we're also specifying the peak of the combined/averaged patterns for both radios. That is the result of combining the patterns in 3D, and determining the peak of that combined/averaged pattern.

That is the more meaningful number when determining peak EIRP.

/Onno

View solution in original post

Highlighted
MVP Expert

Re: Antenna gain with MIMO

Hi Onno,

Great explanation, thanks for clearing up my doubt.

Regards,
Julián
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