MRI: Acquisition of High Speed Mixed Signal Test Equipment

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EIA 02-15753Collins, OliverUniversity of Notre DameMRI: Acquisition of High Speed Mixed Signal Test Equipment This proposal, studying quadrature and Sigma Delta modulation/demodulation, supports communications/signal processing research for experimental validation using simulators. Experimental verification of new ideas in Sigma Delta digital-to-analog and analog-to-digital conversion will be explored. Sigma Delta modulation allows an intrinsically linear two level quantizer to reproduce a high resolution signal by shifting the quantization noise away from the signal band for removal by filtering. The Sigma Delta modulator tries to find the optimal sequence of +1's and -1's such that, after filtering, the squared Euclidean distance between this sequence of +1's and -1's and a given, identically filtered, discrete-time, unity-amplitude-limited sequence filtering is minimized. The research aims to show that Sigma Delta modulation constitutes a crude optimization algorithm and that practicable techniques solve this optimization problem well enough to improve dynamic range beyond the current state-of-the-art. The PI claims that the substantial improvement will almost certainly expose the inherent nonidealities of even single bit quantizers. Because of the bit-to-bit interactions produced by reflections from imperfect impedance matches at its output, even single bit D to A generates noise and spurious signals. The equipment requested, three pieces of high speed, mixed signal test: a data generator, a network analyzer, and a signal analyzer, will allow investigation of these effects and permit the design of better single- and multiple-bit quantizers. The data generator will be used as a stimulus source in a wavelength division multiplexing project; the superior range of the network analyzer will contribute to a microwave remote sensing project. Improvement in analog-to-digital and digital-to-analog bandwidth and dynamic range is expected. The devices are important whenever digital computation must be interfaced to physical world (e.g., getting the analog signal radiated by an antenna). Since the digital revolution depends on these conversions, the interface is critical to send and store information. Improved performance and reduced complexity in manufacturing systems that depend on these conversions, such as personal CD players, cellular telephones, high definition TV, computer modems, deep communication systems would benefit us all. Moreover, in addition to supporting research, the equipment will support enhanced projects in three undergraduate courses and contribute to make the students attractive to industry for both hiring and mentoring the required design projects.