A Synthesis Methodology for Impedance Control through Aperture Width in DMS Filters

This work presents a synthesis and design methodology that enables precise control of the impedance condition in Double-Mode SAW (DMS) filters through the aperture width W. The proposed framework allows the designer to target a specific input/output impedance without the need for external matching networks. The aperture W is identified as the key parameter governing both the static capacitance and the transducer impedance, providing a direct means to tune the matching condition to any desired value. As a practical demonstration, two DMS filters were synthesized and fabricated with target impedances of 50 Ω and 377 Ω, respectively. The experimental results confirm the accuracy of the proposed method and its capability to precisely control the impedance condition through the aperture W, achieving the desired matching with minimal insertion loss.