GHz low-loss filters on LiTaO3 operating at higher harmonics

The authors developed a miniature low-loss SAW (surface acoustic wave) filter for gigahertz frequencies using the leaky surface wave on 36° rotated YX-LiTaO₃. The filter operates at spatial harmonics, and therefore is suited for mass production using a standard single-layer lift-off process with 0.8-μm photolithography and the authors, standard photoresist technique. To achieve low insertion loss the authors used a three-transducer configuration with group-type unidirectional transducers that are electrically matched by a new, simplified phasing and matching network requiring only one circuit element, which is integrated into the package. The filter operates at 1.85 GHz and has an insertion loss of 9.4 dB, a 3-dB-bandwidth of 16 MHz, and 35-dB sidelobe suppression