Surface acoustic wave filter

Abstract

The invention discloses a surface acoustic wave filter. The surface acoustic wave filter comprises a piezoelectric substrate, a plurality of resonators, and a plurality of coupling capacitors, wherein the resonators and the coupling capacitors are integrated on the piezoelectric substrate; the coupling capacitors are connected in series between the input port and the output port; the resonator is connected in parallel between a connection node of the coupling capacitor and a ground potential; and the coupling capacitor and the resonator are connected in series, in parallel and the like to form the surface acoustic wave filter, transmission of specific frequency signals is completed, and the function of the filter is achieved. Herein, a plurality of coupling capacitors are connected in series in the filter, so that the problem of high loss caused by series connection of a plurality of resonators in a conventional filter is solved; the coupling capacitors are relatively easy to prepare, the process difficulty is reduced, the size of the coupling capacitors is smaller than that of conventional resonators formed by interdigital electrodes and reflecting gratings, and miniaturization is facilitated.

Description

technical field [0001] Embodiments of the present invention relate to the technical field of band-pass filters, in particular to a surface acoustic wave filter. Background technique [0002] As a frequency selective device, SAW filters are widely used in mobile communication terminals. The surface acoustic wave filter includes a resonator. The resonator is an interdigitated electrode structure made on a piezoelectric substrate. The resonators are connected in series or in parallel to form a surface acoustic wave filter to complete the filter function. [0003] However, the existing filters use a multi-stage series-parallel structure to increase out-of-band suppression. The cumulative loss of the series resonator is not conducive to meeting the low loss requirements. The resonant frequency of the series resonator is usually higher than that of the parallel resonator. Therefore, for high frequency filters Products, the series resonator electrode line width is extremely small,...

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Problems solved by technology

[0003] However, the existing filters use a multi-stage series-parallel structure to increase out-of-band suppression. The cumulative loss of the series resonator is not conducive to meeting the low loss requirements. The resonant frequency of the series resonator is usually higher than that of the parallel resonator. Therefore, for high frequency filters Products, the series resonator electrode line width is extremely small, the process is more difficult, and the resonator needs a static capacitance value in order to meet the design requirements, requiring a large chip area, which is not conducive to device miniaturization

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