Performance Analysis of Adaptive Wideband Duplexer

Adaptive duplexing eliminates the need for multiple switched duplexers in multiband systems. The technique is based on combining a low isolation device and an active double loop cancelling scheme. A duplexer provides attenuation to the main Tx signals entering the receiver and Tx noise corrupting the receiver band. The solution is tested on a direct conversion receiver and uses an adaptive onedimensional search algorithm. The delays in the double loop cancellation paths are shown to constrain the achievable cancellation bandwidth. When overall cancellation was -60dB it was possible at to achieve a 7MHz cancellation bandwidth.