US 4,306,222 AGranted

(b+a)-Bit D/A converter with b-bit auxiliary D/A converter

AssigneeU.S. Philips Corporation

InventorsJohannes B. H. Peek, Wolfgang F. G. Mecklenbrauker, Theodoor A. C. M. Claasen, Nicolaas Van Hurck

Life of this patent

Estimating the term…

Loading patent…

Abstract

A digital-to-analog converter is described for converting (b+a)-bit code words into an analog signal by means of a b-bit auxiliary digital-to-analog converter. In order to reduce the quantizing noise introduced by the indispensible quantizing of the (b+a)-bit code words for obtaining the b-bit code words these (a+b)-bit code words are applied to an integrating network which has its output connected to an amplitude-limiting device which brings the integrated signal in the signal range of the auxiliary-D/A converter. The output signal of the amplitude-limiting device is now quantized and this quantizing signal is applied to the auxiliary D/A converter which produces analog output signal samples which are applied to, possibly, an analog output filter through a cascade arrangement of an amplitude-restorer and a difference network. The (b+a)-bit code words are assumed to occur with a frequency which is higher than the Nyquist sampling frequency associated with the analog signal represented by these (b+a)-bit code words.

Claims9

Dependent claims

A digital-to-analog converter for converting a digital signal, formed by a sequence of code-words, each having b+a bits, into an analog signal, characterized in that this digital-to-analog converter comprises:

a converter input for receiving the digital signal;
a converter output;
means for integration and amplitude-limiting for producing a digital auxiliary signal which is an amplitude-limited version of the integrated digital signal applied to said means;
first coupling means for coupling the input of the integration and amplitude-limiting means to a converter input;
quantizing means connected to said integration and amplitude-limiting means for limiting the word length of the code words of the digital auxiliary signal for the generation of a quantizing means output signal formed by a sequence of code-words, each having b-bits;
difference and amplitude-restoration means;
second coupling means for coupling the input of the difference and amplitude-restoration means to the output of quantizing means;
third coupling means for coupling the output of the difference and amplitude-restoration means to the converter output;
a b-bit auxiliary digital-to-analog converter included in the circuit formed by the second coupling means, the difference and amplitude-restoration means and the third coupling means.

6 more elements

Dependencies are inferred from the claim text.