Parallel Oversampling DAC Architecture for High-Rate Resolution
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Solution Overview
Problem
Conventional digital-to-analog converters face limitations in high-resolution conversion at very high sampling rates due to issues like quantization noise, sampling jitter, thermal noise, and component mismatches, which restrict their instantaneous bandwidth and resolution.
Innovation Solution
The proposed solution involves a discrete-time noise-shaping/quantization circuit with multiple parallel processing paths, a multiplexer, a multi-bit-to-variable-level signal converter, and an analog bandpass filter, which operates at a subsampling rate lower than the input signal sampling rate, allowing for improved noise frequency response and higher resolution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional DACs operate at very high sampling rates, then instantaneous bandwidth is improved, but resolution and conversion accuracy deteriorate due to quantization noise, sampling jitter, and thermal noise
Solution Approach 1:
The patent divides the high-rate digital input signal into multiple parallel lower-rate processing paths using a demultiplexer. Each path processes a subset of the signal at a reduced sampling rate, which reduces quantization noise and thermal noise effects. The parallel paths are then recombined to reconstruct the full-rate output signal, achieving high instantaneous bandwidth while maintaining high conversion resolution.
Solution Approach 2:
The patent introduces an intermediate parallel processing stage with multiple demultiplexed paths that operate at subsampling rates. This intermediary structure allows noise reduction in each parallel path while maintaining the overall high sampling rate capability through recombination, effectively decoupling the bandwidth and resolution requirements.
2Measurement precision
If conventional DACs increase conversion resolution, then accuracy is improved, but instantaneous bandwidth is limited by the Nyquist criterion and component mismatches
Solution Approach 1:
The patent segments the high-bandwidth signal conversion task into multiple parallel lower-bandwidth conversion paths. Each parallel converter operates at a reduced sampling rate, allowing higher resolution conversion without being limited by the Nyquist criterion at the full sampling rate. The parallel outputs are recombined to achieve the full instantaneous bandwidth with high resolution.
Solution Approach 2:
The patent transitions from a single-dimensional high-rate conversion approach to a multi-dimensional parallel processing architecture. By adding the dimension of parallel processing paths, the system achieves both high instantaneous bandwidth (through the number of parallel paths) and high conversion resolution (through lower individual path rates), effectively trading structural complexity for performance in both dimensions.
3Measurement precision
If conventional DACs use fine granularity quantization, then resolution is improved, but quantization noise and rounding errors increase
Solution Approach 1:
The patent segments the quantization process into multiple parallel coarse quantization paths, each operating at a lower sampling rate. This segmentation reduces the quantization noise burden on each individual path while maintaining fine effective resolution through the parallel combination. The demultiplexer distributes the input signal to parallel quantizers that each handle a portion of the signal with reduced quantization noise.
4Speed
If conventional DACs operate at high sampling rates, then bandwidth is improved, but sampling jitter and timing errors increase
Solution Approach 1:
The patent segments the high-rate sampling operation into multiple parallel lower-rate sampling paths. Each parallel path operates at a reduced sampling rate, which reduces sampling jitter and timing errors in each individual path. The demultiplexer and subsequent recombination structure maintains the overall high instantaneous bandwidth while improving timing accuracy through the parallel lower-rate operation.
Data Source
AI summary
Provided are, among other things, systems, apparatuses, methods and techniques for converting a discrete-time quantized signal into a continuous-time, continuously variable signal. An exemplary converter preferably includes: (1) multiple oversampling converters, each processing a different frequency band, operated in parallel; (2) multirate (i.e., polyphase) delta-sigma modulators (preferably second-order or higher); (3) multi-bit quantizers; (4) multi-bit-to-variable-level signal converters, such as resistor ladder networks or current source networks; (5) adaptive nonlinear, bit-mapping to compensate for mismatches in the multi-bit-to-variable-level signal converters (e.g., by mimicking such mismatches and then shifting the resulting noise to a frequently range where it will be filtered out by a corresponding bandpass (reconstruction) filter); (6) multi-band (e.g., programmable noise-transfer-function response) bandpass delta-sigma modulators; and/or (7) a digital pre-distortion linearizer (DPL) for canceling noise and distortion introduced by an analog signal bandpass (reconstruction) filter bank.