Building Blocks for Sampling and Digitization in High-speed Communication Systems

[摘要] The performance of high speed communication systems crucially depends on the quality and precision of sampling and digitization. Low phase noise oscillators are essential in high data rate communication to ensure data accuracy. The ring VCO is gaining importance in ultra-scaled CMOS technologies because of its efficiency in silicon area. High-speed analog-to-digital converters are used as analog frontends of DSP-based receivers. Power efficient ADCs are required to reduce the energy cost per bit for GHz-rate communication systems.This thesis first presents a novel self-filtering scheme to break the typical tradeoff between noise and power, enabling a ring oscillator to approach the phase noise performance of an LC-VCO. The new scheme only incurs a small extra cost in power consumption and does not require any extra reference or control circuitry. The prototype N-path filter enhanced VCO (NPFRVCO) achieves a measured phase noise of -110dBc/Hz at a 1MHz offset frequency for an oscillation frequency of 1.0GHz. This is more than a 10dB improvement over a comparable fabricated prototype structure without N-path filtering.A new traveling wave pipeline ADC is also proposed that simultaneously achieves the maximum sampling rate and high efficiency. The scheme exploits the delay of on-chip transmission lines to implement a pipeline, and thereby avoids the use of power hungry track-and-hold or MDAC stages. High sampling rates are achieved without using time interleaving, thus no interleaving calibration is needed, making the system design far simpler. This fast energy-efficient ADC architecture will facilitate and improve communication applications. The transmission line is implemented with differential symmetric inductors. This differential structure not only benefits from the mutual inductance, but is also more realistic for integration since it saves silicon area. The prototype is measured at 4.0GS/s and 6.0GS/s sampling clock rate. SNDR of 21.35dB and 18.8dB is measured, respectively. The prototype consumes 38.2mW, and occupies 0.65mm2.

[发布机构] University of Michigan

[效力级别] N-path filter

[关键词] High speed communication systems;N-path filter;traveling-wave ADC;low phase noise ring vco;Electrical Engineering;Engineering;Electrical Engineering