SURFACE ACOUSTIC WAVE APPARATUS

摘要

An improvement of a surface acoustic wave apparatus in the phase difference balance in a balance-input terminal or a balance terminal to suppress a spurious in a pass band. This apparatus has a piezoelectric board, an input IDT and an output IDT each comprising at least one IDT or more. When the cross width of the electrode finger of the input IDT or the output IDT is X, the output IDT or the input IDT has two split IDTs each having an electrode finger the cross width of which is about x/2. The electrodes of electrode fingers of each of the two split IDTs are led out of the two split IDTs and so disposed that the phase of the signal in the two outputs or inputs connected to the pair of balance terminals are different by 180º. The two split IDTs are series-connected with a solid common electrode having an electrode width twice or more larger than the pitch of the electrode fingers of the two split IDTs. The common electrode is connected to the ground potential.