Intermodulation distortion test

Details Intermodulation distortion test Intermodulation distortion test

1979-12-28

1981-06-16

Brigance, Gerald L.

Electricity: measuring and testing

Measuring, testing, or sensing electricity, per se

Frequency of cyclic current or voltage

328162, 324 57N, H04M 326

Patent

active

042739705

ABSTRACT:
Errors in test results are minimized in a test system (FIG. 1) employing digital data acquisition units (121) when measuring intermodulation distortion of a voice frequency communication facility (105) by employing a unique 3-tone test signal. To this end, the three tones have predetermined amplitude, frequency and phase relationships to obtain a test signal having a desired optimum probability density function which is substantially Gaussian. Additionally, circuit noise components are eliminated from the test results by obtaining a measure of noise with a single tone test signal and subtracting it out from the three tone test results. In a specific embodiment, a measure of the power spectrum resulting from the three tone signal and the power spectrum of the single tone signal are obtained, combined and utilized to obtain measurements of second and third order intermodulation distortion products compensated for noise.

REFERENCES:
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Telephony, Nov. 18, 1974, "Breakthrough in Automatic Transmission Measurement", pp. 27-37.
Bell System Technical Reference, Pub. 41008, Oct. 1971, "Analog Parameters Affecting Voiceband Data Transmission-Description of Parameters", pp. 16-24.
Bell System Technical Reference, Pub. 41009, Jan. 1972, "Transmission Parameters Affecting Voiceband Data Transmission-Measuring Techniques", p. 12.
Bell System Technical Reference, Pub. 41009, May 1975, "Transmission Parameters Affecting Voiceband Data Transmission-Measuring Techniques", pp. 17-19.

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