Coupled model analysis of SAW floating electrode type unidirectional transducers

Area of Science:

• Acoustics
• Solid-state Physics
• Electrical Engineering

Background:

• Floating electrode unidirectional transducers (FEUDTs) are crucial for signal processing applications.
• Understanding the performance of FEUDTs requires detailed analysis of their electromagnetic and acoustic coupling.
• Internal reflections within FEUDTs significantly influence device performance.

Purpose of the Study:

• To analyze the performance of single-phase unidirectional transducers using coupled-mode theory.
• To analytically derive key parameters governing the coupling-mode equation for FEUDTs.
• To investigate the impact of asymmetric electrode structures on transducer characteristics.

Main Methods:

• Coupled-mode theory was employed to analyze transducer performance.
• Extended Legendre polynomial expansions and perturbation analysis were used to derive coupling and transduction coefficients.
• Closed-form solutions of the coupled-mode equation were used to calculate frequency responses and field distributions.
• Experimental validation was performed on devices fabricated on LiNbO(3) substrates.

Main Results:

• Analytical derivation of four independent parameters: self and mutual coupling coefficients, transduction coefficient, and static capacitance.
• Calculation of radiation admittance, insertion loss, and surface acoustic wave (SAW) field distributions.
• Clarification of the shift effect on reflection and transduction centers due to asymmetric electrode design.
• Comparison of theoretical predictions with experimental results for fabricated devices.

Conclusions:

• The coupled-mode theory provides an effective framework for analyzing FEUDT performance.
• The derived analytical solutions accurately predict device behavior, including the effects of electrode asymmetry.
• Experimental validation confirms the theoretical model's accuracy, supporting the design of advanced SAW devices.