Excavating
Patent
1979-12-28
1981-11-17
Malzahn, David H.
Excavating
364481, 324 57DE, H04B 346
Patent
active
043015360
ABSTRACT:
Accurate and reliable measurement results are obtained in a test system (FIG. 1) employing digital data acquisition units (121) when measuring frequency response or envelope delay distortion of a network or communication facility (105) by employing a unique test signal (21-tone) including a plurality of tones, each tone having amplitude, frequency, phase component values determined and assigned in accordance with prescribed criteria. The phase component values are determined in accordance with a relationship dependent on the number of tones in the test signal, and in one example, are initially assigned on a random, one-to-one basis to the tones. In a specific embodiment, a test signal is utilized having 21 tones. Further problems arising from nonlinearities on the facility under evaluation (105) are minimized by transmitting the 21-tone test signal a plurality of times and by reassigning the phase component values to the tones each time the test signal is transmitted. In a specific example, the phase component values are reassigned to the tones in counterclockwise, circular fashion after each transmission of the test signal until each tone has taken on each phase component value. Once measurements, i.e., data records, of the transmitted test signal have been obtained, they are utilized to obtain a spectrum, and in turn, the frequency components of the spectrum are employed to obtain the desired measurement of frequency response or envelope delay distortion.
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Favin David L.
Lynn Peter F.
Snyder Paul J.
Bell Telephone Laboratories Incorporated
Malzahn David H.
Stafford Thomas
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