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