A full duplex Front End Module for WiFi 802.11.n applications

This paper describes a complete FEM (front end module) that provides a true full duplex operation, transmit in the 2.4 GHz band while receive in the 5-6 GHz band or vise-versa. This allows superior data rates (2 to 3 times faster) compared to traditional half-duplex systems. The FEM is built from one IC on a 4times6 mm LTCC substrate package. The e-mode PHEMT IC integrates dual low noise amplifiers, dual switches, and dual power amplifiers, power detector and control logic. The LTCC provides a package base and buried antenna diplexer, LNA post filters, and PA pre-filters. The receive 2.4/5-6 GHz channels provide less than 3.8 dB total noise figure at 10 dB gain and 10 mA. In the 802.11g 2.4 GHz transmit mode the FEM provides 17 dBm linear power under 54 Mbps OFDM, at -25 EVM, while drawing only 136 mA of peak current. In the 802.11a 5-6 GHz transmit mode the FEM provides over 17 dBm linear power out under 54 Mbps OFDM, at -24 EVM while drawing 150 mA of peak current. The FEM has integrated all CMOS compatible control functions for power down and duplex mode select. This is the only know or published full duplex FEM at this performance level known for 802.11abgn applications.