SAW band rejection filters for mobile digital television

Mobile DTV requires novel filter solutions to prevent coupling between cellular transmitter and DTV receiver in a cellular telephone. Emphasis is placed on wide transmission bandwidths up to 50% with low loss and wide and deep rejection bands. We show that SAW band reject filters provide an adequate solution for the mobile DTV requirements. The design methodology using classical LC filters as starting point is outlined. Two exemplary designs are presented in measurement. Insertion attenuation of the SAW-filters alone is extremely low, the main source of loss is identified as external inductances of the band rejection network. Low-cost devices are available in packages as small as 1.4 mm times 1.1 mm.