I'm about to design a system with a build in bluetooth module enclose in a box covered by a survival blanket. (little satellite model)

According to Wikipedia, the survival blanket is made of PET (mostly plastic) and a thin metallic sheet.

I'll using a HC-05 bluetooth module, since it's very cheap, I not 100% sure of it's capacity to acquire signals through the metallic sheet.

Do you think it going to work fine? Or should I build a small antenna extension outside the enclose box?

Since I have almost no knowledge about antenna design, I don't know how to build such a low cost antenna.

  • 1
    \$\begingroup\$ ...and a thin metallic sheet That is very likely going to block any RF signals from getting in and out. If there is a possibility to leave at least one side of the Bluetooth module uncovered by the blanket it might work though. I would not go into making an external antenna etc. as this is a specialist area and bound to give you troubles sooner or later. Better solve this at a more fundamental level so not covering the BT module from all sides. \$\endgroup\$ Sep 18 '17 at 12:09
  • \$\begingroup\$ Place the full module on the outside by extending the serial cables? Also, it's cheap enough for you to test this out. \$\endgroup\$
    – Passerby
    Sep 19 '17 at 3:22

If the foil blanket is far enough from the antenna (a few wavelengths) it is likely that the radio signal will be attenuated by 10dB to 30dB. A similar problem has been studied for window glass with thin metallic coatings, for example see figure 8 in https://www.diva-portal.org/smash/get/diva2:882367/FULLTEXT01.pdf

If the foil blanket is closer to the antenna than one wavelength there may be interference and the attenuation could be significantly worse than 30dB.

The metal coating on the plastic is very thin and the best scenario for sending radio through the blanket is likely to be if the foil blanket is one centimetre or less from the antenna. But this may not meet the thermal insulation requirements.

Bluetooth operates at 2400MHz, the same as 802.11b/g/n, so a 2400MHz WiFi antenna will also work for Bluetooth and the antenna may be placed outside the foil blanket if you can purchase a HC-05 module with u.fl antenna connector.


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