0.5 V Digitally-Tunable Filters for Biomedical Applications Exploiting Segmented Duty-Cycled Resistors
In this paper, we present the design and the experimental validation of a biquad filter for biomedical applications that takes advantage of segmented duty-cycled resistors to allow for digital tuning over a wide range of the cutoff frequency (<inline-formula> <tex-math notation="LaTeX&...
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| Main Authors: | , , |
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| Format: | Article |
| Language: | English |
| Published: |
IEEE
2025-01-01
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| Series: | IEEE Access |
| Subjects: | |
| Online Access: | https://ieeexplore.ieee.org/document/10849568/ |
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| Summary: | In this paper, we present the design and the experimental validation of a biquad filter for biomedical applications that takes advantage of segmented duty-cycled resistors to allow for digital tuning over a wide range of the cutoff frequency (<inline-formula> <tex-math notation="LaTeX">$f_{0}$ </tex-math></inline-formula>), quality factor (Q), and gain (K). Additionally, we report on the experimental findings for an 8th-order band pass filter that was created to extract the epilepsy biomarker, related to the fast ripple band (250 Hz–500 Hz). The results of measurements on a prototype chip, implemented in a commercial 130 nm CMOS technology with a supply voltage of 0.5 V and a power consumption of 120 nW, confirm that the <inline-formula> <tex-math notation="LaTeX">$f_{0}$ </tex-math></inline-formula> of the proposed biquad filter can be digitally tuned from 15 Hz up to 517 Hz, whereas the Q can be tuned from 0.7 up to 13. A comparison against the state of the art has shown that the proposed biquad filter exhibits the lowest area, with the highest Q, and can be tuned at the lowest <inline-formula> <tex-math notation="LaTeX">$f_{0}$ </tex-math></inline-formula>. It also exhibits the unique feature to allow for independent tunability of <inline-formula> <tex-math notation="LaTeX">$f_{0}$ </tex-math></inline-formula>, Q, and K by varying the duty-cycle of digital control signals. The 8th-order filter, implemented with 4 cascaded instances of the proposed biquad filter, guarantees an attenuation higher than 30 dB at <inline-formula> <tex-math notation="LaTeX">$f_{0}$ </tex-math></inline-formula>/2 and 2f0 with a power consumption of 480 nW, and an area footprint of 0.152 mm2, thus satisfying the requirements to extract the epilepsy biomarker in closed-loop deep brain stimulation systems. |
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| ISSN: | 2169-3536 |