Dual-path digital filtering for ADC step response overshoot
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Solution Overview
Problem
Current digital filters in analog-to-digital conversion systems for power delivery networks in portable devices suffer from non-monotonic responses and overshoot when dealing with step inputs, which are undesirable, and filters without overshoot often have non-linear phase and high passband droop, making them unsuitable for many applications.
Innovation Solution
The implementation of a dual-path filtering system that includes a zero-overshoot monotonic step response filter and a frequency-selective filter, allowing for selection or combination of filtered signals to generate an output digital signal, thereby addressing the limitations of existing filters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a digital filter with low passband ripple and sharp transition band is used, then filtering performance is improved, but overshoot occurs in the step response
Solution Approach 1:
The patent divides the filtering function into two separate paths: one dedicated to monotonic step response (avoiding overshoot) and another dedicated to frequency selectivity (sharp transition band). Each path is optimized for its specific function, and the outputs are combined to achieve both goals simultaneously.
Solution Approach 2:
Different parts of the filtering system are given different characteristics: the first filter path is designed with monotonic step response characteristics to eliminate overshoot, while the second filter path is designed with sharp transition band characteristics for frequency selectivity. Each path has localized optimization for its specific purpose.
2Object-generated harmful factors
If a filter without overshoot is used, then step response monotonicity is improved, but passband droop increases and transition band becomes gradual
Solution Approach 1:
The patent merges the outputs of two separate filter paths: one that provides monotonic step response and another that provides sharp transition band. By combining these paths through addition or selection, the final output achieves both monotonicity and sharp frequency selectivity that neither path could achieve alone.
Solution Approach 2:
The dual-path filtering system performs multiple functions simultaneously: it provides both monotonic step response and sharp frequency selectivity in a single filtering stage, making the system universally applicable to applications requiring both characteristics without needing separate filtering stages.
3Manufacturing precision
If a filter with sharp transition band is used, then frequency selectivity is improved, but phase linearity deteriorates
Solution Approach 1:
The patent segments the filtering function so that frequency selectivity is handled by one path while monotonic step response is handled by another path. This segmentation allows each path to be optimized for its specific function without compromising the other, and the combination preserves both characteristics including phase linearity.
Data Source
AI summary
An analog-to-digital conversion system may include an analog-to-digital converter configured to convert an analog input signal into an equivalent digital input signal, a first filtering path configured to filter the equivalent digital input signal to generate a first filtered digital signal, wherein the first filtering path comprises a zero-overshoot monotonic step response filter, a second filtering path configured to filter the equivalent digital input signal to generate a second filtered digital signal, wherein the second filtering path comprises a frequency-selective filter; and a mixer configured to either: (i) select between the first filtered digital signal and the second filtered digital signal in order to generate an output digital signal; or (ii) combine selected proportions of each of the first filtered digital signal and the second filtered digital signal in order to generate the output digital signal.