A new tunable RF front-end for advanced 4G handsets

With rapid expansion of the wireless communications application, a large number of frequency bands have been installed in mobile phone handsets and RF paths in the front-end circuit have been increasing, which leads to more complicated circuit configuration. Authors have developed the novel devices and modules to solve those issues. The solution includes a tunable duplexer which consists of a wideband circulator and SAW-based tunable filters for TX and RX, and a tunable low RX noise power amplifier. Those devices are fabricated for the operation in the low frequency band of 699–960MHz whose fractional bandwidth is 31.5%. Experimental results show 40dB isolation of the tunable duplexer and 10dB noise level improvement of the tunable low RX noise PA, which achieves a target value of RX band noise suppression. This module shows promising possibility of a simple RF front-end of advanced mobile phone handsets.