NFC antenna connection to ground midway through loop

by PineapplePerson   Last Updated August 13, 2019 21:25 PM - source

I'm designing a PCB etched NFC antenna. I'm confused about a design element I've seen in several production boards. I haven't seen this element explicitly discussed in any app notes or design guides. Top of board, 4? loop antenna on perimeter

Bottom of board, loop connection to ground shown

On many of these nfc readers, there's a connection to ground on one of the loops in the antenna. On the pictured board, the next-to-outermost loop has a ground connection. What is this? In antenna design calculators basic loops are always implied, and I'm hoping to use these calculators to assist in my design. How will this ground connection affect my calculations for the matching circuit, etc?

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