An eight channel interference cancellation system

This paper describes the design and performance of an eight channel interference cancellation unit (ICU) operating in the 150 - 175 MHz frequency band. The system is able to actively cancel eight arbitrarily spaced interfering signals by up to 40 dB. It has an excellent ability to cancel closely spaced interfering signals exhibited by the fact that the signal of interest (SOI) is attenuated by only 3 dB when the interfering signal is 250 Hz away. When all eight active cancelling channels are operating, a SINAD of at least 22 dB is achieved when each SOI has an input power level of -110 dBm. The ICU is now in production and being installed in US Coast Guard sites as part of the Rescue 21 program.