a second multiplier coupled to said second signal and a second local reference signal and having as {HEAD ~ an output} a fourth signal, said {TAIL ~ second local reference signal phase} offset from said first local reference signal by 90 degrees, 
a second multiplier coupled to said second signal and a second local reference signal and having as { HEAD ~ an output } a fourth signal , said { TAIL ~ second local reference signal phase } offset from said first local reference signal by 90 degrees ,
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH