Filter

Abstract

The invention relates to the technical field of filtering, in particular to a filter, which comprises a series-parallel resonator circuit. The series-parallel resonator circuit comprises a plurality of series resonators and a plurality of parallel resonators, and an annular bulge is arranged on the surface of an upper electrode of at least one series resonator and / or at least one parallel resonator. The annular bulge has a limited width, and the depth of a transmission zero point of the filter is adjusted according to the limited width. The annular projection has a limited height, and the position of the transmission zero point of the filter is adjusted according to the limited height. According to the technical scheme, by changing the structure of the filter and increasing additional resonance generated by the annular protrusions, an additional transmission zero point is formed outside a band, and compared with the prior art, the filter does not need to increase the filter stage number or move the zero point of the specific frequency outside the band, and deterioration of other performance cannot be caused.

Description

technical field [0001] The present invention relates to the technical field of filtering, in particular to a filter. Background technique [0002] The performance of filters, duplexers and multiplexers in the front end of radio frequency communication has higher and higher requirements. With the increase of frequency bands, the demand for out-of-band suppression is becoming more and more stringent; at the same time, adjacent-band suppression has always been a One of the most important indicators of the filter, so the requirements for roll-off are getting higher and higher. It can be seen that in the design of the filter, the improvement of out-of-band rejection (for the far band) and roll-off (for the adjacent band) is one of the ultimate goals. [0003] At present, in the existing technology, the improvement of out-of-band suppression is generally achieved by increasing the number of stages or by moving the position of the out-of-band transmission zero point, but this meth...

AI Technical Summary

Problems solved by technology

[0003] At present, in the existing technology, the improvement of out-of-band suppression is generally achieved by increasing the number of stages or by moving the position of the out-of-band transmission zero point, but this method will bring about problems such as insertion loss deterioration and other frequency suppression deterioration; for roll-off The improvement is generally achieved by using a smaller electromechanical coupling coefficient and an additional resonator, but this method will reduce the bandwidth and increase the area of ​​the resonator, which will lead to the deterioration of the insertion loss and the increase of the chip size.

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