Two step demodulation synchronous detector

摘要

In a synchronous detector a first local signal from a first local signal generator is frequency divided by a frequency divider to obtain a second local signal. The polarity of the first local signal is inverted by a polarity inverter in synchronization with the second local signal, and the output of the polarity inverter is used to synchronously detect the output of an AC amplifier by a first synchronous detector. The synchronous detected output is synchronously detected by the second local signal in a second synchronous detector, the detected output of which is averaged by a filter.