Kevin M Gaukel, RF Engineer with EMR Corporation will present at NUG@NAB2006.

RF Isolators in High Definition Radio Applications with Co-located Analog Radio Signal

Abstract:

With the addition of the digital overlay sidebands over existing co-located analog FM signals, one needs to protect the digital signal from the co-located analog signal. Standard cavity combining is not practical due to the extremely narrow bandwidth and tight selectivity specifications, and hybrid coupling has unacceptably high insertion loss. The solution that has been in wide use is to place a ferrite circulator between the digital-carrier transmitter and the antenna to ensure some level of isolation between the analog and digital signal without selectivity issues. This presentation will describe the problem, the remedy, and the limitations of this remedy with respect to isolator power handling, frequency drift, and antenna isolation.