SAW Filter Signal Wiring Skin Depth Optimization
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Solution Overview
Problem
Conventional SAW filters experience increased signal propagation loss due to the thickness of signal wiring, which has not been effectively minimized in existing designs.
Innovation Solution
The SAW filter design incorporates signal wiring with a thickness not less than the calculated skin depth (d = 2.0×10^-4f×σ), ensuring low propagation loss by concentrating current on the surface and minimizing exponential decay, with optimal thickness ranging from 1.0 to 1.2 times the skin depth to balance propagation efficiency and surface roughness.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If signal wiring thickness is increased, then propagation loss is reduced, but manufacturing precision and surface roughness control become more difficult
Solution Approach 1:
The patent applies parameter changes by establishing a specific thickness range for signal wiring (0.5-2.0 μm) based on skin depth calculations. This quantitative parameter specification resolves the contradiction by providing an optimal thickness range that minimizes propagation loss while remaining manufacturable, rather than simply increasing thickness indefinitely.
Solution Approach 2:
The patent substitutes mechanical intuition (thicker is better for reducing loss) with electromagnetic theory (skin depth effect). By replacing the mechanical approach of simply increasing thickness with the electromagnetic principle of skin depth, the patent achieves optimal loss reduction at specific thickness values rather than continuously increasing thickness.
2Manufacturing precision
If signal wiring thickness is decreased, then manufacturing precision is improved, but propagation loss increases
Solution Approach 1:
The patent establishes a minimum thickness threshold (0.5 μm) based on skin depth calculations, preventing excessive thinning while maintaining manufacturability. This parameter specification resolves the contradiction by defining both upper and lower bounds that balance manufacturing precision with propagation loss requirements.
Solution Approach 2:
The patent replaces mechanical precision improvement (making wiring thinner and more controllable) with electromagnetic optimization (using skin depth theory to determine optimal thickness). This substitution shows that electromagnetic principles, not mechanical precision alone, should guide the thickness determination.
3Loss of energy
If signal wiring thickness is optimized based on skin depth, then propagation loss is minimized, but device complexity increases due to calculation requirements
Solution Approach 1:
The patent transforms the complex skin depth calculation into a practical design guideline by specifying a concrete thickness range (0.5-2.0 μm). This parameter specification simplifies the design process by providing ready-to-use values derived from skin depth theory, eliminating the need for complex calculations in routine design while maintaining optimization benefits.
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 approach results in excellent transmission characteristics for SAW filters by reducing propagation loss and maximizing the effect of skin depth, while minimizing the impact of surface roughness, thereby enhancing the overall performance of SAW filters and duplexers.
Implementation Method 1
The thickness of the signal wiring is not less than a skin depth 'd' (μm) calculated by Formula (1), thereby the signal wiring has low propagation loss of signals passing through the signal wiring
Data Source
AI summary
A SAW filter includes a piezoelectric body, an IDT electrode on the piezoelectric body, and signal wiring electrically connected to the IDT electrode. The signal wiring has a thickness not less than a skin depth specified based on the frequency of a signal passing through the signal wiring and the electrical conductivity of the signal wiring. As a result, the signal wiring has low propagation loss of the signal passing through it, so that the SAW filter has excellent transmission characteristics.