Coded data generation or conversion – Analog to or from digital conversion – Differential encoder and/or decoder
Patent
1993-11-09
1995-03-07
Young, Brian K.
Coded data generation or conversion
Analog to or from digital conversion
Differential encoder and/or decoder
341144, H03M 300
Patent
active
053962443
ABSTRACT:
A digital-to-analog converter comprises a sigma-delta modulator for generating a 1-bit digital signal (D3) modulated synchronously with a clock signal (NF.sub.S) in response to a digital input signal (D2). This modulator is followed by an asynchronous analog sigma-delta modulator for generating a bivalent asynchronously modulated signal (D4) in response to the synchronously modulated digital signal (D3). The information in the digital signal (D3) from the sigma-delta modulator resides in signal transitions which can appear exclusively at discrete instants defined by the clock signal. The information in the asynchronously modulated signal (D4) from the asynchronous sigma-delta modulator is contained in an analog variation of the duty cycle. This means that the signal transitions of the asynchronously modulated signal (D4) are not tied to a fixed pattern of discrete instants but that all the intervening instants are also available. As a result of the freedom of the positions of the signal transitions, the frequency spectrum of the asynchronously modulated signal (D4) has a substantially smaller width than the frequency spectrum of the synchronously modulated digital signal (D3) from the sigma-delta modulator. This enables an interface to a further signal processing device to be simplified.
REFERENCES:
patent: 5245345 (1993-09-01), Kohdaka et al.
Naus et al., "A CMOS Stereo 16-Bit D/A Converter for Digital Audio", IEEE Journal of Solid-State Circuits, vol. SC-22, No. 3, Jun. 1987, pp. 390-395.
Kikkert et al., "Asynchronous Delta Sigma Modulation", Proceedings of the IREE of Australia, vol. 36, Apr. 1975, pp. 83-88.
Franzblau Bernard
U.S. Philips Corporation
Young Brian K.
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