Browse Prior Art Database

Time Notch Filtering System

IP.com Disclosure Number: IPCOM000092360D
Original Publication Date: 1967-Dec-01
Included in the Prior Art Database: 2005-Mar-05
Document File: 2 page(s) / 34K

Publishing Venue

IBM

Related People

Rarich, WB: AUTHOR [+3]

Abstract

The detection and, particularly, the spectral pattern recognition of a weak broad-band signal presents a problem when random-frequency, white noise originating in the environment and in the receiver amplifier system obscures the signal.

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Time Notch Filtering System

The detection and, particularly, the spectral pattern recognition of a weak broad-band signal presents a problem when random-frequency, white noise originating in the environment and in the receiver amplifier system obscures the signal.

For samples which are short in time compared to the reciprocal of the effective bandwidth of the detection system, the time truncated white noise varies as the product of four times the duration of the sample and the square of the bandwidth. The power of a signal pulse synchronized with the sampling time varies as the square of the bandwidth alone. Untruncated white noise varies as twice the bandwidth.

Thus the signal-to-noise ratio can be improved by reduction of the duration of the sample. In decibel terms, the improvement in a time sampled signal detection system can be expressed as equal to 10 log, base 10, times the reciprocal of twice the product of the bandwidth and the sample duration.

This principle can be carried into effect in apparatus in which a source 10 radiates a signal to an antenna. The received signal A is applied to the input of wideband preamplifier 12, the output B of which includes a large component of white noise. A sample of this output is gated by time-notch switch 14, under the control of a synchronizing signal path 16, at the time that the signal is expected at the output of 12. The resulting signal sample C, which is applied to utilization device 18, has a sensitivity improv...