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106 IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 53, NO. 1, JANUARY 2005 Adaptive Duplexer Implemented Using Single-Path
 

Summary: 106 IEEE TRANSACTIONS ON MICROWAVE THEORY AND TECHNIQUES, VOL. 53, NO. 1, JANUARY 2005
Adaptive Duplexer Implemented Using Single-Path
and Multipath Feedforward Techniques
With BST Phase Shifters
Tomás O'Sullivan, Student Member, IEEE, Robert A. York, Senior Member, IEEE, Bud Noren, and
Peter M. Asbeck, Fellow, IEEE
Abstract--As the complexity of modern modulation schemes in-
creases, the noise levels inserted in the receive band by the trans-
mitter 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. Feedfor-
ward 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 isolation 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,

  

Source: Asbeck, Peter M. - Department of Electrical and Computer Engineering, University of California at San Diego
York, Robert A. - Department of Electrical and Computer Engineering, University of California at Santa Barbara

 

Collections: Engineering