June 27, 2017
GPS inside the DPH153-AT Femtocell
Inside the Femtocell lurks a GPS chip.
Ultimately, the chip is a SiRF GSC3f/LPx.
In older model femtocells this is inside of a RoyalTek REB-1315LPNX module.
In newer model femtocells the SiRF chip is mounted directly on the PCB.
Interestingly, the SiRF GSC3f/LPx chip that is the heart of the GPS unit,
itself contains an ARM processor (an ARM7TDMI running at 50 Mhz)
with 1Mbit of SRAM and 4Mbits of flash. It can run on 2.85 volts or 1.2 volts.
As near as I can tell, the GPS section of the board runs on 3.3 volts and
some kind of local regulation is done, but this is not yet clear to me.
New model Femtocells
This is what I have, and here are photos. The critical GPS circuitry is inside
of a shielded container, the lid of which can easily be popped off.
The odd ceramic looking thing mounted on the left side of the PCB is
the internal GPS antenna. Note that a connector for an external antenna is
also provided at the top of the PCB.
Old model Femtocells
If you have an old model Femtocell, it will contain a
pretty yellow RoyalTek REB-1315LPNX module,
inside of which is hidden a SiRF GSC3f/LPx chip.
When the yellow "lid" is pryed off the Royaltek module,
the SiRF chip inside is revealed.
Have any comments? Questions?
Drop me a line!
Tom's electronics pages / tom@mmto.org