The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Jun. 21, 1994
Filed:
Jan. 15, 1993
Robert C Ledzius, Austin, TX (US);
James S Irwin, Paige, TX (US);
Motorola, Inc., Schaumburg, IL (US);
Abstract
A sigma-delta digital-to-analog converter (DAC) (40) receives oversampled input data representative of an analog signal. The data may be optionally interpolated to a higher rate in a interpolator (41). A noise-shaping sigma-delta modulator (42) is connected to the output of the interpolator (41). The output of the modulator (42) is provided to a finite impulse response (FIR) filter (43). The FIR filter (43) has a frequency response characteristic which reduces the shaped noise and aliased components. This noise has a tendency to intermodulate back into the DAC's passband. The FIR filter (43) uses a series of flip-flops (81, 82, 83) functioning as delay elements with well-controlled timing edges. The outputs of the flip-flops (81, 82, 83) control current sources (91, 92, 93) weighted according to corresponding filter coefficients. The outputs of the current sources (91, 92, 93) are then summed in a summing device such as an amplifier (101).