Adaptive duplexer implemented using single-path and multipath feedforward techniques with BST phase shifters

T. O'Sullivan, R.A. York, B. Noren, P.M. Asbeck
2005 IEEE transactions on microwave theory and techniques  
As the complexity of modern modulation schemes increases, the noise levels inserted in the receive band by the transmitter are also increased. In this paper, a technique to enhance the isolation of a surface acoustic wave duplexer is introduced, which reduces the noise levels in the receive band of the system. Feedforward techniques are used to create an adaptive null in the receive band, which can be targeted at any channel across the band. This null has been shown to give an improved
more » ... of 20 dB for the duplexer over a 2-MHz bandwidth. This feedforward system is implemented using a barium strontium titanate phase shifter to enable tunability of the enhancement null. Multipath feedforward techniques are also used to create extra nulls in the receive band and, hence, further improve isolation. Index Terms-Adaptive duplexers, feedforward cancellation, multipath feedforward systems. 0018-9480/$20.00 © 2005 IEEE Robert A. York (S'85-M'89-SM'99) received the B.S. degree in electrical engineering from the University of New Hampshire, Durham, in 1987, and the M.S. and Ph.D. degrees in electrical engineering from Cornell University, Ithaca, NY, in 1989 and 1991, respectively. He is currently a Professor of electrical and computer engineering at the University of California at Santa Barbara (UCSB), where his group is currently involved with the design and fabrication of novel microwave and millimeter-wave circuits, high-power microwave and millimeter-wave amplifiers using spatial combining and wide-bandgap semiconductor devices, and application of ferroelectric materials to microwave and millimeter-wave circuits and systems. Dr.
doi:10.1109/tmtt.2004.839900 fatcat:2456noespjaoxge53z2ffhc7x4