Transversely coupled resonator type surface acoustic wave filter and longitudinally coupled resonator type surface acoustic wave filter

摘要

A transversely coupled surface acoustic wave filter (1) includes a surface acoustic wave substrate (2) having opposing first (2a) and second (2b) end surfaces, and first and second interdigital transducers (3,4) provided on the surface acoustic wave substrate. The first and second interdigital transducers (3,4) define first and second surface acoustic wave resonators which use a wave including a shear horizontal wave as its main component. The first and second surface acoustic wave resonators are connected to define a transversally coupled resonator filter. The filter preferably has a relative dielectric constant E = ε^s₁₁/ε₀ in the range of about 0 to about 3000 and the electromechanical coupling coefficient K is such that K²·ε^s₁₁/ε₀ is in the range of about 0 to about 250. Also, the aperture length y is preferably within the range of: 0.945 + 5.49 × exp(-E/366) ≥ y ≥ 2.46 × exp(-E/219).