Optical Scanning Acoustic Microscopy (OSAM) is a non-contacting method of investigating the properties and hidden faults of solid materials. This thesis presents an ultra-fast data acquisition system (DAQ) which samples and digitises the output signal of OSAM. The author's work includes the design of the clock source and the sampler, and integration of the whole system. The clock source is a unique pulse generator based on a 2.624GHz PLL with a Quadrature VCO (QVCO), which is able to generate 4 clock signals in accurate quadrature phase difference. The pulse generator used the 4-phase clocks to provide control pulses to the sampler. The pulses were carefully aligned to the clock edges by digital logic, so that jitters were reduced as much as possible. The required short time delay for the sampler was also provided by the pulse generator, and this was implemented by a smartly-controlled switch box which re-shuffles the 4-phase clocks. The presented sampler is a novel 10.496GSample/s Sub-Sampling Sample-and-Hold Amplifier (SHA). The SHA sampled the input, and transformed its spectrum down to a low-frequency range so that it can be digitised. Charge-domain sampling strategy and double differential switches were both developed in this circuit to significantly improve the sampling speed. The periodicity of the system input was exploited in repetitive sampling to reduce the noise. These designed modules were integrated into a DAQ for a 2x8 sensor array. A pseudo-parallel scanning strategy was presented to minimise the power consumption, and a current-based buffer was applied to deliver the control pulses into the array. The DAQ was implemented on-chip in a low-cost 0.35um standard CMOS process. The measurement results showed that the DAQ successfully achieved a sampling rate more than 10GS/s, with a maximum output resolution of approximately 6 bits.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:514725 |
| Date | January 2009 |
| Creators | Dong, Peiliang |
| Publisher | University of Nottingham |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
| Source | http://eprints.nottingham.ac.uk/10667/ |
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