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Piezoelectric filter, method for improving out-of-band rejection of piezoelectric filter, multiplexer, and communication device

An out-of-band suppression and filter technology, applied in the fields of piezoelectric filters and their out-of-band suppression improvement, multiplexers, and communication equipment, can solve the problem of reducing the radio frequency performance of BAW technology, affecting the suppression characteristics of low-frequency filters, and filter suppression. Deterioration and other problems to achieve the effect of suppressing or eliminating the pseudo-pass-band phenomenon and improving the out-of-band suppression performance

Pending Publication Date: 2020-11-10
ROFS MICROSYST TIANJIN CO LTD
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Problems solved by technology

But when the frequency of BAW is extended to 800MHz or even lower, because of the unique sandwich structure of BAW structure, strong high-order spurious resonance will be generated near 3 times the basic resonance frequency, which will affect the low-frequency filter in the high-order spurious resonance area. Inhibition characteristics, thus reducing the RF performance of BAW technology in low-frequency filtering devices, limiting its application range
How to degrade filter suppression caused by high-order spurious resonance problems in BAW applications at low frequencies has become an urgent problem for design engineers

Method used

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  • Piezoelectric filter, method for improving out-of-band rejection of piezoelectric filter, multiplexer, and communication device
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  • Piezoelectric filter, method for improving out-of-band rejection of piezoelectric filter, multiplexer, and communication device

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Embodiment Construction

[0053] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0054] Figure 1(a) is the electrical symbol of the BAW resonator, and Figure 1(b) is the equivalent circuit of the BAW resonator. Without considering the loss term, the electrical model of the BAW resonator simplifies to L m , C m and C 0 formed resonant circuit. which consists of a static capacitor C connected between the input and output ports 0 , and one with C 0 Parallel resonant branch, resonant branch by L m and C m in series. According to the resonance condition, there are two resonance frequency points in the resonance circuit: one is f when the impedance value of the resonance circuit reaches the minimum value s , put f s Defined as the series resonant frequency, or resonant frequency, of the resonator; the other is the f when the impedance of the resonant circuit reaches its minimum value p , put f p Defined as the resonator's paral...

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Abstract

The invention discloses a method for improving out-of-band rejection of a piezoelectric filter, the piezoelectric filter is of a trapezoidal structure, the trapezoidal structure of each order comprises a series resonator and a parallel resonator, and the method comprises the following steps: adjusting the thickness of one or more of the series resonator and the parallel resonator in the trapezoidal structure of at least one order, and / or adjusting the thickness of one or more of the series resonator and the parallel resonator in the trapezoidal structure of at least one order; and adjusting materials of all series resonators and / or parallel resonators, so that the anti-resonance frequency corresponding to the high-order parasitic resonance of the parallel resonators in the trapezoidal structure is greater than the resonance frequency corresponding to the high-order parasitic resonance of the series resonators, or the difference value between the anti-resonance frequency and the resonance frequency is less than a set value. According to the technical scheme of the invention, the thickness of layers in the resonators is adjusted, so that high-order parasitic resonance positions of the parallel resonators is moved from a position far lower than the high-order parasitic resonance positions of the series resonators to a position equivalent to or even higher than the high-order parasitic resonance position of the series resonators, thereby suppressing or eliminating the pseudo passband phenomenon of the high-order parasitic resonance region. Therefore, the out-of-band rejection performance of the filter is improved.

Description

technical field [0001] The invention relates to the technical field of filters, in particular to a piezoelectric filter and its method for improving out-of-band suppression, a multiplexer, and communication equipment. Background technique [0002] In recent years, the mobile communication industry has flourished, and 5G has gradually entered people's lives. Mobile communication terminals represented by mobile phones have become an indispensable communication tool in people's daily life. With the increasingly crowded spectrum resources, the data throughput and power consumption requirements of the terminal are getting higher and higher, which brings great challenges to the design of the RF front-end circuit. [0003] At present, the small-sized filter devices that can meet the needs of communication terminals are mainly piezoelectric filters. The resonators that make up such filters mainly include: FBAR (Film Bulk Acoustic Resonator, thin film bulk acoustic resonator), SMR (S...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H03H9/02H03H9/205
CPCH03H9/02086H03H9/205
Inventor 郑云卓庞慰
Owner ROFS MICROSYST TIANJIN CO LTD
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