US 7,023,371 B2 · Method and apparatus for an image canceling digital-to-analog converter (DAC)

Abstract

A method and apparatus for an image canceling digital-to-analog converter is disclosed. Up-sampling and noise shaping is used to produce a stream of digital sample values at a relatively higher sampling rate than the sampling rate of the digitized input samples, each higher sampling rate sample having fewer bits than the original samples. The higher sampling rate stream is then distributed for sequential conversion by multiple digital-to-analog converters each operating at a lower sampling rate. The outputs of the converters are then combined to form a combined output signal. Most spectral images normally observed in a standard or conventional DAC are attenuated in the combined output signal of an embodiment in accordance with the present invention. Any spectral images that remain are further from the signal of interest, permitting the use of lower cost filtering.

Claims27

Dependent claims

An image canceling digital-to-analog converter (DAC) comprising:

an up-sampler for receiving a first stream of digital values at a first sample rate, the first stream of digital values representative of a first signal, each of the digital values comprising a first number of bits, the up-sampler producing, at a second sample rate, a second stream of digital values based upon the first stream of digital values;
a clock source producing a plurality of clock signals substantially equally spaced in time;
a plurality of digital-to-analog converters, each of the plurality of digital-to-analog converters periodically accepting, under control of one of the plurality of clock signals, a digital value from the second stream of digital values, the outputs from the plurality of digital-to-analog converters forming a plurality of analog output signals;
a combiner adapted to combine the plurality of analog output signals to form a combined output signal;
and
a noise shaper for adjusting selected digital values of the second stream of digital values in order to minimize spectral images in the combined output signal.

3 more elements

Dependencies are inferred from the claim text.

Method and apparatus for an image canceling digital-to-analog converter (DAC)

Life of this patent

Method and apparatus for an image canceling digital-to-analog converter (DAC)

Life of this patent

Abstract

Claims27