A 3.8 mm × 3.8 mm × 1.37 mm hermetic FBAR duplexer for 800 MHz handsets with wafer-scale packaging

We describe the design and measured performance of a 3.8 mm × 3.8 mm × 1.37 mm antenna duplexer for the 800 MHz cellular band (Tx: 824-849 MHz, Rx: 869-894 MHz) for cellular handsets based on FBAR (film bulk acoustic resonator) technology. The FBARs are fabricated in a silicon-based IC process technology and are hermetically sealed in a wafer-level packaging process. Two dice, Tx and Rx, are attached to a 4-level printed circuit board, ball-bonded, and encapsulated in plastic to form the final product. Average Tx insertion loss is 1.25 dB, average Rx insertion loss is 1.75 dB. Minimum rejection is 55/45 dB in the Tx/Rx hands, guaranteed isolation is >55/46 dB.