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For all practical purposes, you may assume the dimension given is measured from the edge of the PCB. Fig 15 says it all.
1) I did not see a 7mm in 7.3.1. Is this number from another section? In any case, the take away from this section is that the near field
of the antenna extends up to 4mm from it. This implies that any enclosure (metallic or plastic) must be at least above 4mm in theory.
2) For non-metallic (plastics), the recommendation is at least 5mm. For metallic enclosure, the recommendation is at least 8mm.
For example, the inner wall for a plastic enclosure must be at least 5mm from any of the edges of the module. This especially so for the three
edges along the antenna.
Do not also forget that there must also be ground clearance underneath the antenna. I hope this clears up a bit.
Thanks for your advice.
Sorry, I wrote a wrong number. Not 7mm, it is 4mm.
The customer asked, if the clearance is 4.2mm (<5), will it have a significant impact?
I can't say for sure what is the impact as these figures are rule-of-thumb or best practices. The only way is to build and measure a prototype. It also depends what is the end product. Categorically, I can say that it should not be a significant impact.
I don't really understand your question but let me just elaborate on the picture above.
The picture depicts a view from the top of the module. The red part is the metallic shield over the circuitry. The green part
is the area of which the antenna is printed. The blue part is the dimension of the area, for any number of PCB layers below
the module, to be cleared of electrical trace. For example, can you imagine a power supply line being routed (on any layer)
below the antenna? The performance will be affected. This is the main reason why some clearance is always recommended
around the antenna location.
Thank you for helping me sort out the problem.
>For example, can you imagine a power supply line being routed (on any layer) below the antenna?
>The performance will be affected.
If I imagine a power supply line being routed below the red part.
Will the performance be affected?
I think the red part is the module, is not the antenna.
Add customer's question
As in §7.3.2 and §7.3.3 of AN96841,
Is there any reference material that shows how efficiency or VSWRor directivity or gain varies depending
on the distance between a non-metal or metal and an antenna?
They checked AN91445.
Even if it is not this module(CYBT-343026-01), the experiment and examination data by other antennas may be used.
Ideally, it would be appreciated if there was data when the distance was changed, such as 2mm / 3mm / 4mm / 5mm ...
You may lay PCB traces under the red portion. Do minimize though and I would still avoid any clock signals.
We do not have any of those antenna performance data as these data are measured by customers and they
don't share with us. From the datasheet of the module 343026, you may refer to Table 6 for the antenna
specification. You may refer to AN91445 on meandered line antenna for a more detailed treatment.