SAW FILTER

摘要

The filter comprises at least one acoustic track formed on a piezoelectric substrate. At least one SAW input transducer and at least one SAW output transducer are arranged in each track. Each track has a RSPUDT structure and thus a distributed excitation. The excitation function comprises sources arranged in a main lobe and a tail function comprising at least one tail lobe. A fine and precise approximation to the desired continuous excitation function is obtained by decreasing the excitation strength in the tail function by a factor of at least 2. The exitation strength may be varied by connecting tail-lobe sub-transducers of a first track and a second track in series or in parallel. A capacitor may be circuited in series between main lobe and tail lobe sub-transducers.