Oversampled digital-to-analog converter for multilevel data transmission
AssigneePairgain Technologies, Inc.
InventorsHenry Samueli, Ralph H. Brackert
Life of this patent
Estimating the term…
Abstract
A digital-to-analog converter (DAC) is disclosed which uses an oversampled modulation technique followed by an analog lowpass filter to generate an output waveform with four precisely controlled amplitude levels for 2B1Q data transmission applications. The DAC accepts a 2-bit input word at the baud rate and generates one of four possible analog output amplitudes having relative ratios of +3, +1, -1, and -3.
Claims16
Digital to analog converter apparatus responsive to a multibit data input word for producing a multilevel analog output, said apparatus comprising:
- cyclic binary counter means for counting at a clock frequency f.sub.clk ;
- generator logic means responsive to said counter means for producing during each counter means cycle multiple primitive binary waveforms, each such waveform defining a different DC component;
- select logic means responsive to said data input word for selecting one of said multiple primitive binary waveforms;
- and
- low pass filter means for producing an analog output level related to the DC component of said selected binary waveform.
Apparatus capable of producing L different analog output levels, each representative of a differently configured m bit data input word where L=2.sup.m, said apparatus comprising:
- primitive waveform generator means for concurrently generating L different primitive binary waveforms, each such waveform having a different DC component;
- select logic means responsive to each of a sequence of m bit data input words for selecting at least one of said primitive binary waveforms;
- and
- output means responsive to said selected primitive binary waveforms for producing an analog output level related to the DC component thereof.
A method of producing L different analog output levels, where L is an integer greater than 1, each representative of a differently configured data input word comprised of m bits where m is an integer greater than 1 and where L=2.sup.m, said method comprising:
- concurrently generating L different primitive binary waveforms, each such waveform having a different DC component;
- selecting at least one of said primitive binary waveforms in response to each data input word;
- and
- producing an analog output level related to the DC component of the selected primitive binary waveform.
Dependencies are inferred from the claim text.