Digital compandor

Details Digital compandor Digital compandor

1980-12-18

1982-10-19

Miller, C. D.

Communications: electrical

Audible indication

Percussion-type sound producer

364582, 364606, 340347AD, H03K 1324

Patent

active

043553044

ABSTRACT:
A compressing system for digital modulated signals comprises an analog-to-digital converter for obtaining a digital modulated signal by digitally modulating an analog signal; a first variable gain circuit provided at the output side of the analog-to-digital converter; and a first gain control circuit for equivalently performing level-compression of the analog conversion level of the input digital modulated signal of the first gain control circuit within a predetermined level range by use of a first control signal and the first variable gain circuit. The first gain control circuit comprises an expected signal generating circuit having an analog conversion level z.sub.n which satisfies the equation ##EQU1## (N is an arbitrary natural number, and a.sub.O through a.sub.N are zero or an arbitrary number) where y.sub.n designates the analog conversion level of a digital modulated signal or the differential signal of the digital modulated signal at a time nT obtained from either the input side or output side of said first variable gain circuit (T indicates the sampling period of the digital modulated signal) and a.sub.i designates the coefficient used for the weighting, a variable reference level generator which generates a reference level, and a comparator which supplies the first control signal as output by comparing the reference level thus generated with the analog conversion level z.sub.n of the above expected signal. The expanding system comprises a second variable gain circuit supplied with the digital modulated signal obtained and transmitted from the first gain control circuit, which varies the analog conversion level of the input digital modulated signal according to a second control signal; a second gain control circuit for equivalently performing level-expansion of the analog conversion level of the input digital modulated signal of the second gain control circuit by the same quantity as the above level-compression within a predetermined level range by use of the second variable gain circuit and performing an opposite operation as that performed by the first gain control circuit with respect to the digital modulated signal obtained from either the input side or the output side of the second variable gain circuit, and a digital-to-analog converter for converting the output digital modulated signal of the second variable gain circuit into an analog signal.

REFERENCES:
patent: 3906487 (1975-09-01), Siems
patent: 4023019 (1977-05-01), Leibowitz
patent: 4276604 (1981-06-01), Kitamura
"NTG-Fachtagung Signalverarbeitung" Erlangen 1973 Tagungsband, pp. 354-361.
Noll, "Zurich Seminar Proceedings" 1974, pp. B3(1)-B3(6).
Markel, "Linear Prediction of Speech" Springer-Verlag 1976, pp. 5-12.

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