Synchronization using the RF backplane
Introduction
The eRTM modules have been designed to deliver high quality clocks and
RF signals to the RF backplane to be used by AMCs and RTMs. A clock (or
carrier) signal doesn't transport information by definition, therefore
unsynchronized AMCs require a side channel to perform synchronization.
Notably, the RF backplane doesn't provide a deterministic data channel
to provide PPS and time-code information to the AMCs. The only
communication channel from eRTMs to the AMCs is thorugh a LVDS SPI
connection, which requires an MCH-RTM equipped with an FPGA. Moreover,
the FPGA must re-route the data to the front MCH and then to the AMC
backplane. This solution has been discarded due to unnecessary
complexity.
The proposed solution
The proposed solution is to modulate the clocks distributed by the RF backplane.