A Notch Filter Instrument for Measuring ELF (Extremely Low Frequency) MSK (Minimum Shift Keying) Signals.
Abstract
This report presents a notch filter technique for measuring extremely low frequency (ELF) signals in the presence of other higher-level, low frequency voltages, specifically 60 Hz and harmonics, on public utility systems. The report also describes the design, development, and operation of a special-purpose notch filter instrument that allows the practical realization of this measurement technique. The instrument, called the Notch Box III, is compact (2.75 x 10 x 9 in.), lightweight (less than 4 lb), and battery operated for complete electrical isolation and portability of its electronic circuitry. It features input buffering and selectable attenuation, input overload warning, a narrow-band 60 Hz notch filter with greater than 80 dB of attenuation, a Chebyshev low-pass filter providing sharp roll-off above 100 Hz, output signal buffering, and battery charge status indication. The Notch Box III can operate 150 hours on a single battery charge. Keywords: Extremely low frequency; Interference mitigation; Active filter; Notch filter; Interference measurement; Noise measurement; Instrumentation.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 1988
- Accession Number
- ADA193324
Entities
People
- J. R. Gauger
- R. G. Drexler
Organizations
- IIT Research Institute