SAW 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 integrated on the piezoelectric substrate; the plurality of coupling capacitors are connected in series at the input port and between the output port; the resonator is connected in parallel between the connection node of the coupling capacitor and the ground potential. Coupling capacitors and resonators are connected in series or parallel to form a surface acoustic wave filter to complete the transmission of specific frequency signals and realize the filter function. By connecting multiple coupling capacitors in series in the filter, the problem of high loss caused by multiple resonators in series in conventional filters is solved. The coupling capacitors are easier to prepare, the process difficulty is reduced, and the coupling capacitors are more than conventionally composed of interdigitated electrodes and reflective grids. The size of the resonator is small, and the miniaturization of the device can be realized by using it.

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,...

AI Technical Summary

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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