| 摘要 |
RD-21541 HIGH-ORDER, PLURAL-BIT-QUANTIZATION SIGMA-DELTA MODULATORS USING SINGLE-BIT DIGITAL-TO-ANALOG CONVERSION FEEDBACK A high-order sigma-delta modulator has a single feedback loop including a linear network and a quantizer, which quantizer comprises a plural-bit analog-to-digital converter, a digital comparator and a single-bit digital-to-analog converter. The linear network comprises a cascade of integrators, a second-order resonator, a cascade of second-order resonators or a cascade of second-order resonators with an additional integrator. The loop behaves much the same as a conventional single-feedback-loop, onebit sigma-delta modulator, inasfar as the feedback signal is concerned. However, a plural-bit preliminary output signal is available, so the truncation error can be determined. The truncation error is cancelled in the ultimate output signal from the high-order sigma-delta modulator, using additional digital circuitry having the a transfer function analogous to the overall transfer function for input signal of the cascade connection of the linear network, pluralbit analog-to-digital converter in the quantizer, and any scaling circuitry therein or thereafter.
|
