QUESTION

Question

Hello,

we design devices with a cellular MIMO LTE system, a dual-band Wifi system, Bluetooth and GPS. We have M2.5 screws and nuts in the corners of the enclosure and PCB. The size of the printed circuit board is 133x78 mm. Is it possible to use SR4L049-L and SR4L049-R antennas on the PCB? Which of the three combinations is suitable for best performance? Because only the SR4L049-L antenna is in the stock everywhere, can only this type of the antenna be used, or is it better to have a pair of SR4L049-L and SR4L049-R? Or do you have any recommendations on how to solve the position of MIMO LTE antennas with fixing screws? Smaller holes on the PCB are not mandatory. We will use the R&S ZNLE device to tune the antennas.

Variant A:

Variant B:

Variant C:

Nut in enclosure:

Regards

Peter

Answer 1

Hi Viteka32,

Thanks for your question. The screws will have little effect as long as they are not electrically connected to the ground plane. -L and -R are mirror images and have identical performance, so you can use either or both. Both -L and -R should be placed as close to the corner as possible for optimum performance

In terms of placement, it depends on whether you have it configured for dual antenna or Diversity, ideal placement for both shown below:

Hope this helps.

Thanks

Steve

Comments

Hi,
thanks for answer.

The metal screw is not connected to the ground plane. Do you have any recommended for the distance from the screw? Antenova recommends 3 mm from the plastic enclosure.

Regards.

Peter

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Hi Peter,

Screws should be as far away as possible. It depends on the size of the head and the length of the screw, but as a general rule of thumb at least 10mm away. I've passed your details on to your regional representative who can assist you with detailed response tailored to your specific requirements.

Man Thanks

Steve

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Hi Steve,

We have a routed PCB layout. It is possible to have the following layout of LTE antennas?  We will use a network analyzer for impedance tuning. In the corners are anchor holes from the box for M2x10mm screws.

Regards.

Peter

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Hi Peter.

-L should be fitted in the left-hand corner with copper on the right-hand side, -R should fitted in right-hand corner with copper on the left-hand side. Please also avoid sharp 90 degree turns in the feed.

Many Thanks

Steve