The filtered signal is squared to provide a squared signal alternating at the frequency fm between {HEAD ~ values} related to {TAIL ~ sin2 fx} and cos2 fx 
related to
The filtered signal is squared to provide a squared signal alternating at the frequency fm between { HEAD ~ values } related to { TAIL ~ sin2 fx } and cos2 fx
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD REL REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH