Transmission line analog to digital converter
AssigneeThe Aerospace Corporation
InventorJohn R. Scarpulla
Life of this patent
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Abstract
A transmission line analog-to-digital converter uses an unterminated transmission line driven by a current source to generate a stair-step waveform having equal time step periods for measuring the conversion time as a digital output value of an analog input. The converter has the advantages of simplicity, accuracy, high speed, low transistor count, and low power consumption. Fast successive approximation converters can be used for improved speed and accuracy of digital conversion of analog signals.
Claims19
A converter for converting an input analog signal into a digital value, the converter comprising,
- a sample and hold circuit for sampling and holding the input analog signal and for providing a sampled analog signal,
- a comparator for comparing the sampled analog signal to a stair-step signal during a stair-stepping period and for generating a quantization signal at the end of the stair-stepping period when the sampled analog signal is equal to the stair-step signal,
- a transmission line for generating the stair-step signal by reflections from opposing near and far ends of the transmission line, each step of the stair-step signal having a step period, the stair-step signal generated during the stair-stepping period,
- a current source for driving the transmission line for generating the reflections, and
- a logic circuit for receiving the quantization signal and for time measuring the stair-stepping period as the digital value.
A converter for converting an analog input into a digital value, the converter comprising,
- a sample and hold circuit for sampling and holding the input analog signal and for providing a sampled analog signal,
- comparators for comparing the sampled analog signal to far and near stair-step signals during a stair-stepping period and for generating respective quantization signals,
- a transmission line for generating the far and near stair-step signals by reflections from opposing near and far ends of the transmission line, each step of the stair-step signals having a step period, the stair-step signals generated during the stair-stepping period,
- a current source for driving the transmission line for generating the reflections, and
- a logic circuit for time measuring the stair-stepping period as the digital value.
A converter for converting an analog input into a digital value, the converter comprising,
- a sample and hold circuit for sampling and holding the input analog signal and for providing a sampled analog signal,
- comparators for comparing the sampled analog signal to far and near stair-step signals during stair-stepping periods and for generating respective quantization signals,
- a transmission line for generating the far and near stair-step signals by reflections from opposing near and far ends of the transmission line, each step of the stair-step signals having a step period, the stair-step signals generated during the respective stair-stepping periods,
- a current source for driving the transmission line for generating the reflections, and
- a logic circuit for time measuring the stair-stepping periods as a digital value of the sampled analog input and for providing the digital value.
A converter for converting an analog input into a digital value, the converter comprising,
- a sample and hold circuit for sampling and holding the input analog signal and for providing a sampled analog signal,
- a residual circuit for generating and sampling a residual,
- a multiplexer for selecting the sampled analog signal or the residual as a multiplexed analog signal,
- near and far comparators for respectively comparing the multiplexed analog signal to far and near stair-step signals during a significant stair-stepping period and a residual stair-stepping period and for generating respective near and far quantization signals, the residual being a difference between sampled analog signal and one of the near or far stair-stepping signal at either the near and far quantization signals,
- a transmission line for generating the far and near stair-step signals by reflections from opposing near and far ends of the transmission line, each step of the stair-step signals having a step period, the significant and residual stair-step signals generated during the respective significant and residual stair-stepping periods,
- a current source for driving the transmission line for generating the reflections, and
- a logic circuit for time measuring the significant and residual stair-stepping periods as the digital value.
Dependencies are inferred from the claim text.