Piezoelectric Thin-Film Filter Layout for Harmonic Suppression
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Solution Overview
Problem
Piezoelectric thin film resonators in wireless communication devices generate harmonics due to non-linearity, which existing methods such as dividing the resonator or shielding wiring lines fail to effectively reduce.
Innovation Solution
A filter design incorporating two piezoelectric thin film resonators with identical crystal orientation and interconnected upper electrodes but non-connected lower electrodes, mounted on substrates with a ground pattern that does not overlap with the resonators' resonance or connection regions, reducing floating capacitance and harmonics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If the piezoelectric thin film resonator is divided to reduce harmonics, then the non-linearity is reduced, but harmonics cannot be reduced effectively
Solution Approach 1:
The piezoelectric thin film resonator is divided into multiple resonators (first and second resonators) with identical crystal orientation. Each resonator includes piezoelectric films and electrodes arranged in series, creating separate resonance regions that can be independently controlled while maintaining overall harmonic reduction functionality
Solution Approach 2:
The invention introduces a new spatial dimension by mounting the first substrate containing the divided resonators onto a second substrate with a ground pattern. This creates a three-dimensional structure where the ground pattern on the second substrate provides shielding and capacitance control without interfering with the resonance regions of the divided resonators on the first substrate
2Reliability
If the ground pattern overlaps with the resonance or connection regions, then grounding is improved, but floating capacitance increases causing harmonics
Solution Approach 1:
The ground pattern is extracted from the resonance and connection regions by positioning it only in non-overlapping areas on the second substrate. This separates the grounding function from the resonant regions, allowing effective grounding without introducing harmful floating capacitance that would generate harmonics
Solution Approach 2:
The second substrate acts as an intermediary between the ground pattern and the first substrate containing the resonators. This intermediate layer allows the ground pattern to provide grounding functionality while maintaining spatial separation from the resonance regions, thus avoiding direct capacitive coupling that would create harmonics
3Power
If large electric power is input to the piezoelectric thin film resonator, then output signal is improved, but harmonics are generated due to non-linearity
Solution Approach 1:
The resonator is segmented into multiple identical crystal orientation sections (first and second resonators) connected in series. This segmentation allows the device to handle larger input power by distributing the electrical stress across multiple sections, reducing the non-linear effects in each individual section while maintaining high output signal capability
Solution Approach 2:
The invention changes the crystal orientation parameter of the piezoelectric films in the divided resonators to be identical, rather than using different orientations. This parameter uniformity across segmented sections reduces non-linear effects when large power is applied, allowing high output signal without generating harmful harmonics
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
This configuration significantly reduces secondary distortion and harmonics, improving high-frequency characteristics and impedance while maintaining compact size.
Implementation Method 1
each of the first piezoelectric thin film resonator and the second piezoelectric thin film resonator including a piezoelectric film
Implementation Method 2
To inhibit the electromagnetic coupling between wiring lines interconnecting the piezoelectric thin film resonators
Data Source
AI summary
A filter includes: a first substrate; first and second piezoelectric thin film resonators located on the first substrate, each of the resonators including first and second electrodes facing each other across a piezoelectric film, a crystal orientation from the first electrode to the second electrode of the piezoelectric film being the same between the resonators, the first electrodes of the resonators connecting to each other in a connection region between resonance regions where the first and second electrodes face each other across the piezoelectric film, the second electrodes of the resonators failing to connect to each other, and an area of the resonance region being approximately the same between the resonators, a second substrate mounting the first substrate across an air gap; and a ground pattern located on the second substrate and not overlapping with the first electrode located in the resonance regions and the connection region.