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I want to use a blank PCB (no copper) as a panel of an enclosure because it seems to be the cheapest way (Seeedstudio et al.) to have custom holes and cutouts.

I wonder if antennas placed behind such a material can work (ordinary FR-4, just without copper) and what the attenuation is? I am thinking of 2.4 and 1.5 GHz.

The only resources I could find deal with frequency limits when the FR-4 PCB is actually carrying the signals.

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    \$\begingroup\$ It depends on alot of things. If they are in the near-field, they could detune your antenna, especially if it is electrically small. In the far-field there will be some attenuation, depending upon thickness, but it probably won't be material. \$\endgroup\$
    – MikeP
    Commented Jul 17, 2019 at 20:08

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FR-4 is non-conductive material with a dielectric constant of 4.2 - 4.8 (varies with frequency and manufacturer) and relative permeability of 1, (see Wikipedia page for FR-4). With such characteristics, I expect it to cause reflections (far-field) and detuning of antenna (near-field). The FR-4 causes a discontinuity in the RF link, since its characteristics differ from characteristics of free space (air or vacuum).

But with a finite thickness, the effect might not be too dramatic. 2.4 GHz has a wavelength of 125 mm, which is much more than the thickness of FR-4 (I assume you would be using something like 1.6 mm thickness). But the transmission through the FR-4 is also dependent on other dimensions than the thickness (how much of the Fresnel zone the FR-4 is blocking). So, if you enclose the antenna from all sides, Fresnel zone will definitely be blocked.

Unfortunately I couldn't find any research from which you could directly interpret the effects of FR-4 to the RF link. Many antennas have a polymer cover, which is also a lossy material. Plastics seem to have a bit lower dielectric constant than FR-4, but maybe they can be the starting point for estimating the performance of FR-4.

I hope you try it, and share your research here. I'd be interested in reading the results.

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