Amplifiers – With amplifier bypass means
Patent
1975-10-29
1977-06-28
Mullins, James B.
Amplifiers
With amplifier bypass means
328155, 328167, H03F 100
Patent
active
040328570
ABSTRACT:
A distortion measurement system for measuring distortion as low as 0.002% includes an ultra low distortion oscillator having a relatively fast response which is achieved by switching the time constant of the control loops of the oscillator during settling. The analyzer section included in the distortion system has a unique notch filter which provides low distortion. This is achieved by adding together two 90.degree. all pass phase shifters. In addition, automatic tuning is provided by two feedback control loops; one is responsive to out-of-phase signals which controls the RC filter circuits of the phase shifters and the other responds to the in-phase signals which controls the output summing junction of the notch filter. Finally, a feedforward type of simultaneous tuning is accomplished by ganging the oscillator frequency adjustment with the analyzer.
REFERENCES:
patent: 2450818 (1948-10-01), Vermillion
patent: 3375451 (1968-03-01), Borelli et al.
patent: 3548296 (1970-12-01), Sundstrom
patent: 3743957 (1973-07-01), Feistei
patent: 3755749 (1973-08-01), Van Ryswyk et al.
patent: 3911776 (1975-10-01), Beigel
Althouse et al.; "Two Interference Nullers," Radio-Electronics, Aug. 1967, pp. 38-41.
Tow, "A Step-by-Step Active-Filter Design," IEEE Spectrum, Dec. 1969, pp. 64-68.
Comer et al.; "Inductorless Bandpass Characteristics Using All-Pass Networks," IEEE Transactions On Circuit Theory, Dec. 1968, pp. 501-503.
Mullins James B.
Sound Technology, Inc.
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