Abstract: This paper presents an effective noise cancellation circuit in acoustic, which is designed, simulated, and measured. The feedforward earphone is with high performance of noise suppression. The main structure consists of a controller, a notch filter, a high-pass filter, a microphone, and a speaker. The noise detection microphones pick up sounds and divide them into human voice and low-frequency noise. After passing through the gain-controlled filters, the embedded filtered-X least mean-square (FxLMS) algorithm will generate anti-noise signals with 180° phase difference to ambient noise. Consequently, these anti-noise signals will be transformed from digital formats to analog format, and thereby transformed to acoustic signal by the speakers. The generated acoustic signal will cancel the ambient noise, leading to a quiet zone. According to the measured results, it is indicated that a 15-dB noise reduction is achieved.
Keywords: Active noise cancellation, low-frequency noise, feed forward type, feedback type.
1. I. T. Ardekani and W. H. Abdulla, “Active noise control in three dimensions,” IEEE Trans. Control Syst. Technol., 2014. (Accepted)
2. D. C. Chang and F. T. Chu, “Feedforward active noise control with a new variable tap-length and step-size filtered-X LMS algorithm,” IEEE Trans. Audio, Speech, Lang. Process., vol. 22, no. 2, pp. 542-555, Feb. 2014.
3. D. C. Chang and F. T. Chu, “A new variable tap-length and step-size FxLMS algorithm” IEEE Signal Process. Lett., vol. 22, no. 2, pp. 542-555, Feb. 2014.
4. M. Guldenschuh and R. D. Callafon, “Detection of secondary-path irregularities in active noise control headphones,” IEEE Trans. Audio, Speech, Lang. Process., vol. 22, no. 7, pp. 1148-1157, July 2014.
5. S. Ahmed, M. T. Akhtar, and X. Zhang, “Online acoustic feedback mitigation with improved noise-reduction performance in active noise control systems,” IET Signal Processing, vol. 7, Iss. 6, pp. 505-514, Aug. 2013.
Abstract: Carbon Nanotube Field Effect Transistor (CNFET) is a promising new technology that overcomes several limitations of traditional silicon integrated circuit technology. In recent years, the potential of CNFET for analog circuit applications has been explored. This paper proposes a novel four quadrant analog multiplier design using CNFETs. The simulation based on CNFET technology shows that the proposed multiplier has better features than CMOS Multiplier. Multiplier-divider circuits is using in digital signal processing base on neural networks and communications (amplifiers with variable gain, modulators, detectors and,…).In Most of CMOS analog circuit, transistors are only in triode or saturate regions; till now both regions not used. In this one kind of current mode multiplier- divider circuits is intrudused.it is very simple, has low die area and wide range in low voltage. All tough this circuit has no sense to temperature variation and varying parameters.
Keywords: CNT, Analog signal processing, current- mode operation, multiplier, reconﬁgurable circuits.
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