Signal Processing Enhanced DACs for Wideband Communication Systems

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The relentless progress of communication system technology toward increased bandwidth and decreased unit cost has been enabled by increasingly sophisticated digital signal processing made possible by the perpetuation of Moore's Law. Nevertheless, communication systems based on digital signal processing inevitably require certain high-performance analog circuit blocks, and the accuracy required of these blocks will increase as communication standards continue to evolve. Unfortunately, in perpetuating Moore's Law integrated circuit (IC) technology trade-offs are necessary that favor digital circuitry over analog circuitry; high-performance analog circuits are increasingly difficult to implement as IC technology is scaled. Thus, there is a fundamental disconnect between the requirements of present and future high-performance communications and the evolution of the semiconductor electronics industry.This research addresses an important aspect of this problem by developing digital signal processing enhancement techniques that enable high-resolution, high-bandwidth digital-to-analog converters (DACs) which are critical components in wideband communication transmitters. Presently, such DACs are limited by component mismatches inevitably introduced during IC fabrication and by other non-ideal circuit effects that introduce nonlinear transient distortion. The goal of the research is to develop digital signal processing algorithms that mitigate these problems. The research consists of four tightly-coupled components: 1) the development of an ultra-efficient dynamic element matching (DEM) technique for eliminating harmonic distortion caused by component mismatches, 2) the development of an adaptive noise cancellation technique that augments the DEM to reduce SNR degradation caused by component mismatches, 3) the development of an interpolation technique to mitigate the nonlinear transient problem, and 4) the development of a CMOS integrated circuit prototype with record-setting performance as a proof-of-principle and to provide feedback with which to guide the theoretical work.