Predictive A/D Converter Topology Without Post Filters
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Solution Overview
Problem
Existing A/D converters require additional post filters and circuitry to manage quantization noise, leading to increased circuit size and power consumption, especially when dealing with capacitive charge output elements.
Innovation Solution
The A/D converter design includes a prediction filter with an integrator, imperfect differentiator, and delay devices to generate a predicted value, which is fed back to the adder, eliminating the need for post filters and using a capacitance adder to reduce impedance conversion and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If noise shaping is performed using a ΔΣ modulator with an integrator, then quantization noise is shifted to high-frequency region, but the circuit size increases due to the need for steep post filters
Solution Approach 1:
The patent extracts and removes the integrator from the noise shaping path, using only an imperfect differentiator instead. This eliminates the need for steep post filters while still achieving quantization noise suppression through the differentiator's inherent frequency response characteristics.
Solution Approach 2:
The patent changes the approach from integrating (low-pass filtering) to differentiating (high-pass filtering), fundamentally altering the noise shaping mechanism. The imperfect differentiator's transfer function naturally attenuates low-frequency quantization noise without requiring additional filtering stages.
2Adaptability or versatility
If a hybrid modulator is used to increase input voltage range through Δ modulation, then the input range is extended, but a post filter is still necessary which increases circuit size
Solution Approach 1:
The patent removes the post filter component from the hybrid modulator configuration, achieving a self-contained system where the imperfect differentiator provides both noise shaping and sufficient output filtering, eliminating the need for additional post filter circuitry.
3Use of energy by stationary object
If a capacitance adder is used to reduce impedance conversion circuitry, then power consumption is reduced, but the adder must handle both analog signal and predicted value directly
Solution Approach 1:
The capacitance adder is designed to perform multiple functions: it acts as both the adder for combining the analog input signal and predicted value, and simultaneously serves as the integrator for the imperfect differentiator circuit. This multi-functionality reduces the need for separate impedance conversion circuitry while maintaining low power consumption.
Data Source
AI summary
An A/D converter includes an adder that calculates a difference between an analog input signal and a predicted value, a quantizer that quantizes the difference output from the adder to convert the analog input signal to a digital signal, a prediction filter that generates a predicted value from the digital signal output from the quantizer, and a D/A converter that converts the predicted value from a digital signal to an analog signal and output the predicted value to the adder. The predicted value before being subjected to conversion to the analog signal by the D/A converter defines and functions as an A/D converted output of the analog input signal input to the adder.