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Low-Cutoff, High-Pass Digital Filtering of Neural SignalsThe figure depicts the major functional blocks of a system, now undergoing development, for conditioning neural signals acquired by electrodes implanted in a brain. The overall functions to be performed by this system can be summarized as preamplification, multiplexing, digitization, and high-pass filtering. Other systems under development for recording neural signals typically contain resistor-capacitor analog low-pass filters characterized by cutoff frequencies in the vicinity of 100 Hz. In the application for which this system is being developed, there is a requirement for a cutoff frequency of 5 Hz. Because the resistors needed to obtain such a low cutoff frequency would be impractically large, it was decided to perform low-pass filtering by use of digital rather than analog circuitry. In addition, it was decided to timemultiplex the digitized signals from the multiple input channels into a single stream of data in a single output channel. The signal in each input channel is first processed by a preamplifier having a voltage gain of approximately 50. Embedded in each preamplifier is a low-pass anti-aliasing filter having a cutoff frequency of approximately 10 kHz. The anti-aliasing filters make it possible to couple the outputs of the preamplifiers to the input ports of a multiplexer. The output of the multiplexer is a single stream of time-multiplexed samples of analog signals. This stream is processed by a main differential amplifier, the output of which is sent to an analog-to-digital converter (ADC). The output of the ADC is sent to a digital signal processor (DSP).
Document ID
20110020527
Acquisition Source
Jet Propulsion Laboratory
Document Type
Other - NASA Tech Brief
External Source(s)
http://www.techbriefs.com/component/content/1571?task=view
Authors
Mojarradi,Mohammad (California Inst. of Tech. Pasadena, CA, United States)
Johnson, Travis (California Inst. of Tech. Pasadena, CA, United States)
Ortiz, Monico (California Inst. of Tech. Pasadena, CA, United States)
Cunningham, Thomas (California Inst. of Tech. Pasadena, CA, United States)
Andersen, Richard (California Inst. of Tech. Pasadena, CA, United States)
Date Acquired
August 25, 2013
Publication Date
September 1, 2004
Publication Information
Publication: NASA Tech Briefs, September 2004
Subject Category
Man/System Technology And Life Support
Report/Patent Number
NPO-30841
Distribution Limits
Public
Copyright
Public Use Permitted.

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IDRelationTitle20110020517Collected WorksNASA Tech Briefs, September 2004
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