A fully silicon integrated SAW programmable transversal filter with programming/read-out circuitry

A new fully silicon integrated SAW programmable transversal filter (PTF) with active piezoelectric junction FET detectors in a layered configuration of ZnO-SiO₂-Si is presented. The active detectors are located at the SiO₂-Si interface, resulting in a propagation path free of wave-disturbing metal strips. The filter consists of 32 analog controllable active taps, and has two tracks of active detectors. The sum of the signals of the upper track is subtracted from the sum of the signals of the lower track by a differential transimpedance amplifier. The SAW is generated via an interdigital transducer (IDT), having a pitch of 48 μm, giving a filter center frequency of 60 MHz. The detectors have a pitch of 240 μm, resulting in an intertap delay D=96 ns. The time-bandwidth product amounts to 16. The integrated filter features a low-noise readout amplifier and accurate bias control circuitry with a simple reference signal