Cellular-handset design is evolving toward higher integration and the use of more "plug-and-play" modules. In support of that trend, the AFEM-7731 front-end module (FEM) from the Wireless Semiconductor Division of Agilent Technologies (San Jose, CA) houses two vital cellular-handset components, the duplexer and the transmit power amplifier (PA), within a single package. Designed for code-division-multiple-access (CDMA) 1900 Personal Communications Services (PCS) and dual-band cellular handsets, the compact module provides the critical input and output matching to the PA as well as the impedance matching between duplexer and amplifier for ease of installation in handset designs.
The AFEM-7731 blends two of the company's key technologies. The duplexer, which is designed for transmit frequencies of 1850 to 1910 MHz and receive frequencies of 1930 to 1990 MHz, is fabricated with film-bulk-acoustic-resonator (FBAR) technology while the transmit amplifier, which delivers +24.5 dBm linear output power from a +3.4-VDC supply, stems from a GaAs enhancement-mode pseudomorphic high-electron-mobility-transistor (E-pHEMT) process highly regarded for its characteristic high power-added efficiency (PAE).
The duplexer's layout (see figure) provides high isolation, with receive noise blocking of 44 dB and transmit signal suppression of 54 dB. The duplexer's insertion loss is 2.2 dB in the receive band and 1.8 dB in the transmit band. The PA, which is designed to operate from a single positive voltage supply of +3.2 to +4.2 VDC, draws only 380 mA current. With fixed and dynamic bias control, the PA provides PAE of 40 percent. The FEM is supplied in a surface-mount-technology (SMT) package measuring 5.0 × 8.0 × 1.3 mm.