Stub Filter Residue Generation for ADC Blocker Tolerance
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Solution Overview
Problem
Continuous-time analog-to-digital converters (ADCs) face limited blocker tolerance due to large out-of-band signals, which can overload the system and degrade performance, restricting their application in high-speed and high-performance scenarios.
Innovation Solution
Incorporating stub filters in the ADC system to attenuate blockers before quantization, allowing for improved blocker tolerance by modifying the analog input and generating a filtered signal that reduces aliasing and power dissipation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If continuous-time residue generation is used to achieve high sampling rates, then speed is improved, but blocker tolerance deteriorates due to large out-of-band signals overloading the system
Solution Approach 1:
The patent applies preliminary filtering action by placing stub filters before the quantizer to pre-attenuate out-of-band blockers. This preliminary action prevents large blockers from reaching the quantizer and causing overload, thereby improving blocker tolerance while maintaining the high sampling rate capability of continuous-time residue generation
Solution Approach 2:
The stub filters serve as intermediary elements between the analog input and the quantizer. These filters mediate the signal path by selectively attenuating blocker frequencies before they can interfere with the quantization process, resolving the contradiction between high-speed operation and blocker tolerance
2Reliability
If stub filters are added to attenuate blockers before quantization, then blocker tolerance is improved, but device complexity increases
Solution Approach 1:
The patent changes the electrical parameters of existing transmission line structures by transforming portions of the feedforward path into stub filters. This parameter transformation allows the same physical structures to serve dual purposes: maintaining signal paths while providing filtering functionality, thereby improving blocker tolerance without proportionally increasing device complexity
Solution Approach 2:
The stub filters are designed to perform multiple functions: they attenuate blockers, maintain impedance matching, and preserve the high-speed signal path. By making the filter structures multi-functional, the patent reduces the need for additional dedicated components, thereby limiting the increase in device complexity while achieving improved blocker tolerance
3Device complexity
If blocking signals are not attenuated, then system operation is simple, but power dissipation increases due to overload conditions
Solution Approach 1:
The stub filters apply preliminary anti-action by pre-attenuating blockers before they can cause overload conditions. This prevents the harmful effect of large signal amplitudes that would lead to excessive power dissipation in subsequent stages, while maintaining simple system operation through passive filtering
Data Source
AI summary
Residue generation systems for use in continuous-time and hybrid ADCs are disclosed. An example residue generation system includes at least one stub filter, configured to generate a modified analog input based on an analog input, and a quantizer, configured to generate a digital input to a feedforward DAC based on the modified analog input generated by the filter. The feedforward DAC is configured to generate a feedforward path analog output based on the digital input generated by the quantizer, and the system may further be configured to generate a residue signal based on the feedforward path analog output. Providing one or more stub filters that filter the analog input before it is quantized by the quantizer advantageously allows blockers to be attenuated before they are sampled and aliased by the quantizer.