Wednesday, August 20, 2014
Because applying DC to these piezoelectric devices causes electromigration, and therefore the filter destruction. Manufacturers warns about applying DC to the filters, but manufacturers have been ignoring this for decades.
A transceiver with this problem can be easily repaired by just replacing all the damaged filters, and to prevent this problem to appear again, a pair of DC blocking capacitors must be inserted at the filter input/output pins. In fact some manufacturers have modified their PCB in latest revisions to add these capacitors. But are these capacitors enough to keep DC out of the filters?