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Cascaded Frequency-Response Synthesis for Enhanced Side-Lobe Rejection and 3-dB Bandwidth Sharpening in Surface Acoustic Wave Filters |
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PP: 1159-1181 |
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doi:10.18576/amis/200503
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Author(s) |
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Haitham Issa,
Hani Attar,
Jafar Ababneh,
Zakaria Che Muda,
Ismail A. M. Elhaty,
Eman Salah Abass,
Ramy M. Bahy,
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Abstract |
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| This paper presents a cascaded frequency-response approach for enhancing side-lobe rejection and sharpening the 3-dB bandwidth of surface acoustic wave (SAW) filters. The method is applied to a uniformly apodized rectangular-window SAW filter composed of a 7-electrode input interdigital transducer (IDT) and a 40-electrode output IDT. The individual IDT responses are first modeled using the delta-function approximation and simulated in MATLAB. The baseline transfer response is then iteratively cascaded by repeated multiplication with the output-IDT response, generating a sequence of composite responses up to 50 cascade orders. For each cascade order, the center frequency, peak response level, insertion-loss magnitude, side-lobe rejection, and 3-dB bandwidth are extracted and analyzed. The simulated results show that the center frequency remains nearly constant at approximately 162 MHz after the first cascade, while the side-lobe rejection increases almost linearly with cascade order. Specifically, the side-lobe rejection improves from 8.24 dB for the baseline response to 575.8 dB after 50 cascades. In contrast, the 3-dB bandwidth decreases nonlinearly from 8.70 MHz to 0.549 MHz over the same range. A linear regression model is developed for predicting side-lobe rejection, while Gaussian, polynomial, and power-law models are evaluated for bandwidth prediction. The extracted models provide compact design equations for estimating the cascade order required to satisfy a target side-lobe rejection or bandwidth. The results also reveal a significant trade-off between selectivity improvement and insertion-loss degradation, as the peak response level decreases from approximately -11.31 dB to -305.50 dB after 50 cascades. The proposed method therefore provides an ideal frequency-response synthesis and design-screening framework that can contribute to process innovation and product innovation in high-selectivity RF and SAW-filter components. By supporting improved frequency selectivity and reliable front-end filtering for modern communication and sensing systems, the approach is relevant to the development of resilient infrastructure and broader infrastructural development in advanced wireless technologies. The method also provides a computationally efficient route for early-stage design evaluation that may support future manufacturing innovation, although practical realization requires dynamic-range-aware design, physical cascading analysis, and validation using higher-order acoustic models or measurements. These contributions align the work with United Nations Sustainable Development Goal 9, Industry, Innovation and Infrastructure. |
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