Ultra-wideband longitudinally coupled-resonator filters on lithium niobate using periodically slotted SiO2 as an acoustic coupler

Abstract

This paper discusses the applicability of periodically slotted SiO2 as a coupler for ultra-wideband longitudinally coupled-resonator filters. It is shown that a −3 dB fractional bandwidth of more than 31% can be achieved by using lower-order three resonance modes. It is also shown that a periodically slotted SiO2 structure can also control the frequency dispersion of wave propagation along the surface, and transverse modes are suppressed well for one particular mode under a proper setting. Then the piston design is applied for the remaining two modes, and the spurious-free and flat-passband triple-mode filter is synthesized.