Love Wave Tunable Filter With Wider Frequency Tuning Range
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Solution Overview
Problem
Existing tunable filters using surface acoustic wave resonators have narrow frequency variable width and complex manufacturing processes, leading to increased costs and poor resonant characteristics in wide frequency regions.
Innovation Solution
A tunable filter utilizing Love waves with a LiNbO3 substrate, incorporating inductance for band extension and variable capacitance, and an IDT electrode made of Pt film, which reduces leakage and enhances filter steepness and frequency variable width.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If variable capacitors are connected to serial and parallel arm resonators to achieve frequency tuning, then frequency variability is improved, but the frequency variable width becomes narrow
Solution Approach 1:
The patent introduces inductances with variable inductance values that can be dynamically adjusted alongside the variable capacitors. This dynamic adjustment of both capacitance and inductance allows the filter to achieve a wider frequency variable width while maintaining frequency variability, resolving the contradiction between these two parameters.
Solution Approach 2:
The patent changes the electrical parameters of the system by introducing variable inductances in addition to variable capacitors. By adjusting both capacitive and inductive parameters, the system achieves broader frequency tuning range without compromising frequency variability, effectively resolving the parameter conflict.
2Reliability
If Cu electrode is embedded in groove on piezoelectric substrate to use Love waves, then resonant characteristics are improved, but manufacturing process becomes complicated and costs increase
Solution Approach 1:
The patent extracts the groove structure from the design, eliminating the need to embed Cu electrodes in grooves. Instead, it uses a flat piezoelectric substrate with surface-mounted electrodes, which maintains Love wave resonant characteristics while significantly simplifying the manufacturing process and reducing costs.
Solution Approach 2:
The patent replaces the complex embedded electrode structure with a simpler, cheaper surface-mounted electrode configuration. This substitution maintains the essential Love wave functionality while using less complex, more cost-effective manufacturing methods.
3Reliability
If Cu electrode is embedded in groove to use Love waves, then resonant characteristics are improved, but stop-band width becomes narrow and filter characteristic deteriorates near anti-resonant frequency
Solution Approach 1:
By removing the groove structure and using surface-mounted electrodes on a flat substrate, the patent achieves both narrow stop-band and improved filter characteristics near anti-resonant frequencies while maintaining Love wave resonant characteristics. This structural extraction resolves the contradiction between resonant quality and stop-band performance.
4Loss of energy
If Pt film is used for IDT electrode with optimized thickness and Euler angles, then leakage is reduced and filter steepness is enhanced, but manufacturing precision requirements increase
Solution Approach 1:
The patent optimizes specific parameters including Pt film thickness (set at 0.04λ) and Euler angles (θ=128°, φ=0°, ψ=0°) to minimize leakage loss. By precisely defining these parameters, the patent achieves low energy loss while providing clear manufacturing specifications that balance precision requirements with achievable manufacturing capabilities.
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 solution achieves low-loss, steep filter characteristics and widens the frequency variable range by using Love waves and optimizing the Pt film thickness and Euler angles, reducing manufacturing complexity and costs.
Implementation Method 1
the tunable filter uses Love waves
Implementation Method 2
a piezoelectric resonator, an inductance for band extension connected to the piezoelectric resonator
Data Source
AI summary
A tunable filter using Love waves includes an inductance for band extension connected to each of piezoelectric resonators, variable capacitances are connected to the piezoelectric resonator, the piezoelectric resonators each include a LiNbO3 substrate and an IDT electrode, and a pass band and an attenuation region are positioned in a frequency region on a lower frequency side relative to a value obtained by a calculation in which an acoustic velocity of a low-velocity transversal wave propagating in the LiNbO3 substrate is divided by a wave length defined by a period of the IDT electrode.