Novel 1-chip FBAR filter for wireless handsets

Thin film bulk acoustic resonators, or FBARs, are surely a technical breakthrough for the miniaturization of RF filters and for the integration with other RF components. However, there are few problems of limitation in the size reduction and the difficulties in monolithic integration, because FBARs and auxiliary circuits are still manufactured separately and assembled using wire bonding process. Therefore, we establish for the first time a novel monolithic 1-chip transmit (Tx) filter that can be achieved with a minimum size of 1 mm × 1 mm × 0.8 mm using a suspended membrane FBAR, a integrated inductor, and wafer level packaging (WLP) for 1900 MHz PCS handsets. The 1-chip filter has an insertion loss less than 2.86 dB in the pass band (1850–1910 MHz) of US PCS Handsets. Attenuation characteristics is measured to show excellent performance at over 35 dB in Rx band (1930–1990 MHz) and over 25 dB in the below 1800 MHz range.