1,837 research outputs found
Error Compensation in Pipeline and Converters
This thesis provides an improved calibration and compensation scheme for pipeline Analog-to-Digital Converters (ADCs). This new scheme utilizes the intermediate stage outputs in a pipeline to characterize error mechanisms in the architecture. The goal of this compensation scheme is to increase the dynamic range of the ADC. The pipeline architecture is described in general, and tailored to the 1.5 bitslstage topology. Dominant error mechanisms are defined and characterized for an arbitrary stage in the pipeline. These error mechanisms are modeled with basis functions. The traditional calibration scheme is modified and used to iteratively calculate the error characteristics. The information from calibration is used to compensate the ADC. The calibration and compensation scheme is demonstrated both in simulation and using a custom hardware pipeline ADC. A 10-bit 5 MHz ADC was designed and fabricated in 0.5 pm CMOS to serve as the demonstration platform. The scheme was successful in showing improvements in dynamic range while using intermediate stage outputs to efficiently model errors in a pipeline stage. An application of the technique on the real converter showed an average of 8.6 dB improvement in SFDR in the full Nyquist band of the ADC. The average improvement in SINAD and ENOB are 3.2 dB and 0.53 bits respectively
Neutron spectrometer for fast nuclear reactors
In this paper we describe the development and first tests of a neutron
spectrometer designed for high flux environments, such as the ones found in
fast nuclear reactors. The spectrometer is based on the conversion of neutrons
impinging on Li into and whose total energy comprises the
initial neutron energy and the reaction -value. The LiF layer is
sandwiched between two CVD diamond detectors, which measure the two reaction
products in coincidence. The spectrometer was calibrated at two neutron
energies in well known thermal and 3 MeV neutron fluxes. The measured neutron
detection efficiency varies from 4.2 to 3.5 for
thermal and 3 MeV neutrons, respectively. These values are in agreement with
Geant4 simulations and close to simple estimates based on the knowledge of the
Li(n,) cross section. The energy resolution of the spectrometer
was found to be better than 100 keV when using 5 m cables between the detector
and the preamplifiers.Comment: submitted to NI
Distributed Quantization for Sparse Time Sequences
Analog signals processed in digital hardware are quantized into a discrete
bit-constrained representation. Quantization is typically carried out using
analog-to-digital converters (ADCs), operating in a serial scalar manner. In
some applications, a set of analog signals are acquired individually and
processed jointly. Such setups are referred to as distributed quantization. In
this work, we propose a distributed quantization scheme for representing a set
of sparse time sequences acquired using conventional scalar ADCs. Our approach
utilizes tools from secure group testing theory to exploit the sparse nature of
the acquired analog signals, obtaining a compact and accurate representation
while operating in a distributed fashion. We then show how our technique can be
implemented when the quantized signals are transmitted over a multi-hop
communication network providing a low-complexity network policy for routing and
signal recovery. Our numerical evaluations demonstrate that the proposed scheme
notably outperforms conventional methods based on the combination of
quantization and compressed sensing tools
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