Narrow band stop filters using piezoelectric crystals - have fourth order circuits to produce accurate frequency characteristics

摘要

A number of improved bandstop filter circuits uses piezoelectric crystals and fourth order circuits to produce accurate frequency characteristics with a narrowly defined highly damped band. These are of bridged T circuit formation with a parallel and aerial resonant circuit in the series element, and the dual of this in the parallel element. The circuit consists of a series element and of two parallel resonant circuits (C22, L22) in parallel with a series resonant pair (2L11 C11/2), and the parallel element of a series resonant pair (L21/2, 2C21) with a piezoelectric crystal incorporated in it. Several more elaborate networks band on this and their frequency characteristics are also described.