Yeah, it’s to isolate the modem and I think it’s done the same way in Librem 5. Both phones also have a killswitch that lets you power off the modem. As far as I know other phones instead have the modem built into the SoC and there is some isolation too, but I don’t really know how that works and I guess it’s done by the chip’s manufacturer (but I’m not sure).
Like the Librem 5, the PinePhone uses separate cellular baseband and Wi-Fi/Bluetooth chips. Together with the hardware kill switches, this results in larger printed circuit boards (PCBs) and less energy efficiency compared to the mass-produced Android phone that has an integrated System on a Chip, such as the Snapdragon, Helio or Exynos. The PinePhone is thinner at 9.2 mm than the Librem 5 which is 15.5 mm thick because the PinePhone solders its wireless communication chips to the PCB whereas the Librem 5 places the cellular baseband and Wi-Fi/Bluetooth on two removable M.2 cards.[1][18][19]
Yeah, it’s to isolate the modem and I think it’s done the same way in Librem 5. Both phones also have a killswitch that lets you power off the modem. As far as I know other phones instead have the modem built into the SoC and there is some isolation too, but I don’t really know how that works and I guess it’s done by the chip’s manufacturer (but I’m not sure).
https://en.wikipedia.org/wiki/PinePhone