Flash ADC Rectification for High-Speed Low-BER DSP Receivers
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Solution Overview
Problem
Conventional DSP-based serial receivers face challenges in achieving low bit error rate (BER) at high speeds while maintaining low power and area requirements, due to the exponential increase in power and area with ADC resolution and the limitations of traditional ADC types such as flash, pipeline, and successive approximation register (SAR) architectures.
Innovation Solution
The integration of calibration and error detection/correction features, such as distributed offset calibration and redundant comparators, along with low BER rectification, which reduces the number of comparators needed in a flash ADC, allowing for higher clock frequencies and improved ADC performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a traditional N-bit flash ADC is used to achieve low BER, then measurement precision is improved, but power and area increase exponentially with resolution
Solution Approach 1:
The ADC conversion process is segmented into two distinct phases: a coarse conversion phase that determines the most significant bit, and a fine conversion phase that determines the remaining bits. This segmentation allows the system to use fewer comparators in the fine conversion stage, thereby reducing power consumption while maintaining the required measurement precision for low BER performance.
Solution Approach 2:
The coarse conversion is performed as a preliminary action before the fine conversion. By determining the most significant bit first, the system prepares the signal in advance, allowing the subsequent fine conversion to operate on a reduced signal range. This preliminary action enables the fine conversion stage to use fewer comparators, reducing overall power consumption while maintaining precision.
2Measurement precision
If a traditional N-bit flash ADC is used to achieve low BER, then measurement precision is improved, but area increases exponentially with resolution
Solution Approach 1:
The ADC architecture is divided into two conversion stages: coarse conversion and fine conversion. The coarse stage handles the most significant bit with a simple comparator, while the fine stage handles the remaining bits with a reduced set of comparators. This segmentation dramatically reduces the total number of comparators needed, thereby reducing the ADC area while maintaining the precision required for low BER performance.
Solution Approach 2:
The coarse conversion serves as a preliminary action that determines the most significant bit before the fine conversion begins. This preliminary determination allows the fine conversion stage to operate on a reduced signal range, requiring fewer comparators and thus reducing the overall ADC area while preserving the measurement precision needed for low BER.
3Use of energy by stationary object
If pipeline or SAR ADCs are used to reduce power and area, then power and area are reduced, but they cannot achieve low BER at high speed
Solution Approach 1:
The conversion process is segmented into two rapid stages: coarse conversion and fine conversion. Both stages operate in a time-interleaved manner, allowing the ADC to achieve high conversion speeds. The segmentation enables the use of simpler, lower-power comparators in the fine stage while maintaining the high speed and low BER performance through the overall architecture.
Solution Approach 2:
The ADC employs periodic time-interleaved operation where the coarse and fine conversions alternate in a regular pattern. This periodic action allows the system to maintain high conversion speeds by keeping both conversion paths active and synchronized, achieving both high speed performance and low BER while consuming less power than a traditional flash ADC.
4Speed
If multiple interleaved ADCs are used to achieve low BER at high speed, then speed and BER are improved, but power and area increase
Solution Approach 1:
Instead of using multiple full-resolution interleaved ADCs, the system segments the conversion into coarse and fine stages within a single ADC structure. This segmentation allows the system to achieve high conversion speeds with a single ADC, avoiding the need for multiple interleaved converters and thereby reducing power consumption while maintaining high speed and low BER performance.
Data Source
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AI summary
Methods and apparatuses are described for a DSP receiver with an analog-to-digital converter (ADC) having high speed, low BER performance with low power and area requirements. Speed is increased for multi-path ADC configurations by resolving a conventional bottleneck. ADC performance is improved by integrating calibration and error detection and correction, such as distributed offset calibration and redundant comparators. Power and area requirements are dramatically reduced by using low BER rectification to nearly halve the number of comparators in a conventional high speed, low BER flash ADC.