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