ACTIVE BROADBAND PIEZOELECTRIC FILTER Russian patent published in 2002 - IPC

FIELD: radio electronics; main-selection filters for communication equipment. SUBSTANCE: filter has two structurally identical sections 1, 2 each incorporating first resistor 3 whose first lead is connected to filter input; first and second operational amplifiers 4, 5 with negative resistive feedback circuits, inverting inputs of these amplifiers being interconnected. Noninverting input of first operational amplifier 4 is connected through second resistor 8 to output of second operational amplifier 5 and through first capacitor 9, to second lead of first resistor 3 that functions as section output; at the same time it is connected through parallel-connected first piezoelectric cavity 10 and second capacitor 11 to common bus. Noninverting input of second operational amplifier 5 is connected through third capacitor 12 to output of first operational amplifier 4 and through third resistor 13, to common bus. Algebraic adder 14 has first and second inputs and output that functions as filter output. Outputs of first and second sections 1, 2 are connected to first and second inputs 15, 16 of algebraic adder 14, respectively. Each filter section incorporates in addition second piezoelectric cavity 18 for connecting second lead of first resistor 3 to common bus. EFFECT: enhanced filter selectivity. 1 dwg