A novel switchable SAW Duplexer for band 28

Band 28 has wide bandwidth of 45MHz and narrow duplex gap of 10MHz in 700MHz band, and since digital terrestrial TV channels in some countries are overlapped with lower frequency range of the uplink band, two types of duplexer which have slightly shifted passbands need to be used. This paper describes a novel switchable SAW duplexer which can cover both bands in one duplexer. By using a filter design technique with unique switching circuit, and wideband and low temperature drift SAW resonator technology, high performance such as 2.6/3.0dB insertion loss and 55dB isolation have been achieved, in addition to more than 13/16dB near point attenuation only 5/8MHz apart from the passband edge. The developed switchable duplexer can lead the reduction of 40% in mounting area on RF front-end circuit of mobile terminals.