Bulk Acoustic Wave Resonator Bias Structure for Frequency Stability
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Solution Overview
Problem
Conventional filters used in mobile communications, such as micro-strip, cavity, dielectric, and IPD filters, fail to meet the requirements of small in-band ripple, large out-of-band rejection, and good rectangularity due to their large size and poor performance characteristics.
Innovation Solution
A bulk acoustic wave resonator with a base substrate, first and second electrodes, and a piezoelectric layer, incorporating bias resistance layers and electric isolation layers made of high resistivity materials, and mirror structures to enhance frequency control and reduce signal loss.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional filters (micro-strip, cavity, dielectric, IPD) are used, then the device can be manufactured with existing technology, but the filter performance (out-of-band rejection, rectangularity, in-band ripple) is insufficient
Solution Approach 1:
The patent replaces conventional electrical filter structures (micro-strip, cavity, dielectric, IPD) with a bulk acoustic wave resonator system that uses mechanical acoustic waves for filtering. The resonator converts electrical signals to acoustic waves and back, utilizing the mechanical vibration properties of the piezoelectric material to achieve superior filtering performance with better out-of-band rejection and rectangularity.
2Loss of energy
If acoustic wave reflectors are added to confine acoustic waves, then insertion loss is reduced, but device complexity increases
Solution Approach 1:
The patent extracts the acoustic wave confinement function from complex external reflector structures and integrates it directly into the resonator device through the piezoelectric material layer and electrode configuration. The acoustic wave is naturally confined within the piezoelectric material due to the impedance mismatch at the interfaces, eliminating the need for additional external reflector components.
3Ease of manufacture
If the resonator uses a simple sandwich structure, then manufacturing is easier, but frequency control and temperature stability are insufficient
Solution Approach 1:
The patent utilizes the piezoelectric effect to change the mechanical and electrical parameters of the resonator in response to applied voltage. By applying a direct current bias voltage to the piezoelectric material, the resonant frequency can be tuned and stabilized against temperature variations, achieving precise frequency control while maintaining the simplicity of the sandwich structure.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The resonator achieves improved frequency control and reduced insertion loss by confining acoustic waves within the resonator structure, maintaining stable resonant frequencies despite temperature changes through direct current bias voltage adjustments.
Implementation Method 1
a radio frequency signal enters into the resonator from an electrode at one end of the resonator, then is converted into an acoustic wave signal of mechanical vibration at an interface of the piezoelectric material and the metal electrode through an inverse piezoelectric effect
Implementation Method 2
the acoustic wave signal is transmitted to the electrode at the other end of the resonator, and is converted into the radio frequency signal at the interface of the metal electrode and the piezoelectric material through a piezoelectric effect
Implementation Method 3
In order to reduce the insertion loss during the filtering process, it is necessary to limit the acoustic wave signal as much as possible inside the piezoelectric material, to prevent the acoustic wave signal from spreading out
Data Source
AI summary
A bulk acoustic wave resonator, a method for manufacturing the same and an electronic device are provided, and belong to the field of communication technology. The bulk acoustic wave resonator includes: a base substrate, a first electrode, a piezoelectric layer, and a second electrode. The bulk acoustic wave resonator further includes: a first bias resistance layer on a side of the first electrode close to the base substrate, and a first electric isolation layer between the first bias resistance layer and the first electrode; the first bias resistance layer is made of a material with a high resistivity; and/or a second bias resistance layer on a side of the second electrode away from the base substrate, and a second electric isolation layer between the second bias resistance layer and the second electrode; and the second bias resistance layer is made of a material with a high resistivity.