The PCB for this Steam Link has a grid of squares near the antenna. It also has pads for what I guess is either testing or adding 0ohm resisters.

antenna & grid of pads

What is the purpose of this feature, and why are there pads on it?

An album with a picture of the full PCB can be found here, if that's helpful.


You're right, this is a ground plane, but as the antenna to the right is a PIFA, its characteristics are most influential on the antenna impedance and its radiation pattern.

This looks like a way to be flexible about antenna matching:

If after design some parameters of the board change (e.g. PCB substrate \$\varepsilon\$), or its surroundings (e.g. battery in other place, player's hand closer to antenna than originally planned), then your antenna doesn't work like designed anymore.

You'd need to "pieces" of capacitance and/or inductance to it. These small squares basically allow the factory really really late in the production process to re-tune the antenna.

So, that's a smart move to have a perfect-as-possible antenna without having to constantly respin the board just because you need a tiny shift in your Smith chart.

Instead, you just add a 0 Ω resistor and a cap (or multiple) until you found a good way of making your antenna work as desired.

  • \$\begingroup\$ thats a lot of flexibility \$\endgroup\$ – BeB00 Dec 5 '18 at 22:04
  • \$\begingroup\$ well, it's easy to just have these pads, and unpopulated pads don't cost a thing. \$\endgroup\$ – Marcus Müller Dec 5 '18 at 22:05
  • \$\begingroup\$ THis variation of a 3D inverted F patch with 3 floating pads near 5 inductively coupled ground squares. is replicated with two orthogonal antenna and slotted strip near the corner. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Dec 5 '18 at 22:26
  • \$\begingroup\$ Note the 3 floating pads have a coplaner impedance with the surrounding coplanar ground squares and are no where near the feed line for impedance matching. \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Dec 5 '18 at 22:50
  • 2
    \$\begingroup\$ I see Ethertronics won awards in the last year and had over 4 yrs of dozens of smart antenna patents released in 2018 from beam steering to proximity compensation to fuzzy noisy spectral antenna tuning. and were just bought by AVX/Kyocera. My guess this asymmetrical antenna design uses floating coplanar pads to reduce ground effects and then beam steers with the strongest orthogonal antenna and uses slotted radiator to prevent sharp nulls in between There are 4 antennae on this board of 2 identical types. two black mobile patches on left side and two orthogonal of which 1 is shown. V-Nice! \$\endgroup\$ – Tony Stewart Sunnyskyguy EE75 Dec 5 '18 at 23:34

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