ABSTRACT Filters based on using single-phase, unidirectional transducers (SPUDT) consisting of λ/4 and wider electrodes are presented. The design variants exploit the significant difference between the reflectivity of short-circuited λ/4 electrodes and that of floating wide electrodes on 128° lithium niobate (LiNbO3). The surface acoustic wave (SAW) devices operating at 2.45 GHz have critical dimensions of about 0.3--0.4 μm, accessible to standard optical lithography. When matched, the fabricated SPUDT filters exhibit minimum insertion losses of 5.5--7.9 dB together with 3 dB passbands of 89--102 MHz. The majority of the insertion loss can be attributed to the attenuation on free surface and inside the grating, and to the resistivity of the electrodes.
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