Abstract
With the rapid advancement of 5G and Wi-Fi 6E systems, there is a growing demand for flexible, low-power, and tunable radio frequency (RF) components. Traditional tunable filters, often based on rigid substrates or high-voltage tuning mechanisms, lack the flexibility and energy efficiency required for next-generation wearable and portable communication devices. To address this gap, this paper presents the design, fabrication, and characterization of a three-state flexible tunable bandpass filter based on organic electrochemical transistors (OECTs). The filter is fabricated on a PET substrate using a screen-printing process, with OECTs integrated into the resonator structure to enable low-voltage electrical tuning. Experimental results demonstrate that the filter achieves three distinct tuning states within the frequency range of 4.37–5.45 GHz, covering both 5G NR n79 and Wi-Fi 6E bands. Key performance metrics include an insertion loss of 1.65–1.87 dB, return loss close to 20 dB, and an ON/OFF ratio exceeding 103, all achieved with only a 1.3 V bias voltage. The filter also maintains stable performance under mechanical bending, confirming its suitability for flexible electronics. This work highlights the potential of OECT-based tuning for next-generation flexible RF systems, offering a compelling combination of low-voltage operation, low loss, high tunability, and scalable fabrication.
Data availability
All data generated or analyzed during this study are included in this manuscript. Additional data related to this paper are available from the corresponding author upon reasonable request.
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Acknowledgements
This work was financially supported by the Liaoning Technical University (Grant No. 21-1039).
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W. Y. conceived the idea, revised, and finalized the manuscript. L.W. designed the experiments, prepared the OECT and Filter, performed measurements, analyzed the data, and wrote the manuscript draft. J.W. and L. T helped with part of the experiment and data analysis, as well as figures preparation. E.J.W.L-K. revised the final manuscript. All authors reviewed the manuscript.
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Yang, W., Wu, L., Wei, J. et al. A low-voltage three-state flexible tunable bandpass filter using organic electrochemical transistors for 5G NR n79 and Wi-Fi 6E applications. npj Flex Electron (2026). https://doi.org/10.1038/s41528-026-00548-2
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DOI: https://doi.org/10.1038/s41528-026-00548-2
