Design of Rx filter for WCDMA direct-conversion front-end using FBAR technology

We present an Rx filter based on thin film bulk acoustic resonator (FBAR) technology for the wide-band code division multiple access (WCDMA) direct-conversion front-end applications. The filter, which consists of two lattice sections and one ladder section, provides deep rejection at stop-band, particularly at transmitter band (1920-1980 MHz), and steep roll-off at pass-band edges. The typical broadband rejection is better than 60 dB. The simulated result is compared with the up-to-date SAW filter, and demonstrates the excellent characteristics of the new FBAR filter. The small size, low in-band insertion loss, sharp roll-off, high stop-band rejection, good temperature stability, and compatibility with semiconductor processing make this FBAR filter an ideal choice for WCDMA Rx filter applications