A DDS Synthesizer with Digital Time Domain Interpolator

A DDS type circuit structure for producing numericallyprogrammable square wave clock signal is presented. The high speed D/Aconverter needed in conventional DDS systems is replaced by an\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document} $$N$$ \end{document} tap delay line time domain interpolator thateffectively increases the sampling rate by a factor of\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document} $$N$$ \end{document}. Thus the circuit can be used up to full clock rate withoutimage filtering. A prototype IC with clock frequency of 30 MHz, 5 bitinterpolator and SFDR of −40 dBc up to 10 MHz and −33 dBcup to 15 MHz has been designed and tested.