QUESTION

Question

I am considering using a Grandis SR42I010 ISM antenna in a design with a GND plane of 90mm x 25mm located above a metal (zinc) casting. I can provide a separation of approximately 10mm from the metal. What effect is the metal likely to have on the overall performance of the antenna? Is there anything I can do to optimize performance?

Answer 1

Hi Mark,

10mm is not that much for separation between the antenna and the metal object.  We typically recommend 15 to 20mm.  To optimize the performance the ground plane should be 115mm by 35mm. I would recommend cutting away some of the metal underneath the antenna out of the zinc casting to increase the distance between the antenna and the casting.

Best regards,

Geoff S.

Comments

Hi Geoff,

I understand your recommendation for a larger separation and increased ground plane. I will look into increasing the separation. I cannot remove metal but could possibly make the board taller so that the antenna is not directly above the underlying metal. I cannot make the board wider but might be able to extend the size to around 130mm x 25mm. I assume it is the total ground plane area that is important.

Mark

---

Hi Mark,

The length of the board is more important than the width when it comes to operation in the sub 1GHz band.
Separating the antenna from the metal even by 5mm will make a large difference in antenna performance.  I would not place the antenna any closer than that.

Best regards,

Geoff S.