There is a circuit schematic associated with this printed circuit board. Some of the pads in the center section are connected together and some are not. Some are connected to the center ground plane and some are not. Note also that the three ground planes (top, mid and bot.) are isolated from each other. And note also that the center pin of the SMA connector is connected to a few of the terminals on both the IN and OUT sides. This is best observed by looking at the back side of the PCB (where the QR Code is located) using a magnifying glass to see the traces.
Attached to this messages a 2-page PDF that includes some images of the PCB and shows how some of the pads are inter-connected. See page-2.
I hope you find this helpful.
AE5CZ
