{HEAD ~ The first sub path} extracts the second order intermodulation component from {TAIL ~ the path} tuning signal of the main path 
{ HEAD ~ The first sub path } extracts the second order intermodulation component from { TAIL ~ the path } tuning signal of the main path
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH