A new reference-spur cancelation technique is presented for supply-regulated ring-oscillator-based integer-N phaselocked loops (PLLs). A passive RC filter is used to implement a feed-forward (FF) spur-coupling path to perform spur cancelation at the PLL control signal. The proposed technique achieves a simulated spur cancelation of about 22 dB at the first spur harmonic. The simulated postcancelation spur value is -79 dBc for an oscillator gain of 0.1 GHz/V and -46 dBc for an oscillator gain of 6 GHz/V. Spur cancelation is also robust against large process, voltage, and temperature variations in the gain and bandwidth of the FF path. A 1-GHz integerN PLL prototype in a 65-nm CMOS process has a measured cancelation of 19.5 and 13 dB at the first and the second spur harmonic, respectively, with 320 μW of total power consumption. The PLL prototype has an oscillator gain of 1.5 GHz/V, which results in a postcancelation spur of -53 dBc. The proposed zero-power technique is suitable for low-power PLLs as it achieves a large spur cancelation without requiring any additional power consumption or calibration.
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A Transparent Membrane for Active Noise Cancelation
A method for active noise cancelation that uses an optically transparent membrane is described. The membrane consists of a prestretched hydrophobic elastomer, attached to a rigid frame and sandwiched between two hydrogels swollen with an aqueous solution of salt. The elastomer functions as a dielectric, and the hydrogel functions as an ionic conductor. When the two hydrogels are subjected to a sinusoidal voltage, the membrane generates sound. A linear model for the reflection, transmission, and generation of sound by the membrane in an impedance tube is presented and validated. Active noise cancelation is demonstrated using the linear model and feedforward control. Compared to passive sound absorption, the sound transmission loss across the membrane is improved with active control from an average value of 7 dB to an average value of 16 dB. The transparent membrane may be used to cancel noises through a window, while maintaining its transparency.
more » « less- NSF-PAR ID:
- 10064433
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Functional Materials
- Volume:
- 28
- Issue:
- 29
- ISSN:
- 1616-301X
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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