Pilot recovery and polarity detection system

摘要

A polarity detection circuit for an FPLL demodulated signal including a small DC pilot recovers the DC pilot by determining the DC levels of the demodulated output signals both with and without the DC pilot. A zero carrier condition is created for determining the DC level of the output signal without the DC pilot. The two DC levels are subtracted and limited and the polarity of the recovered DC pilot is used to control the operation of a polarity inverter to assure that the output signal has a desired polarity.