ADC Gain Compensation in Decimation Filters for Stable Output
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Solution Overview
Problem
Conventional analog-to-digital conversion circuits with automatic gain control experience unstable outputs due to the response time of the decimation filter when the amplification factor of the variable gain amplifier is changed, limiting the speed at which the amplification factor can be varied.
Innovation Solution
Incorporating a weight change unit in the decimation filter that weights the PDM signal by the reciprocal of the amplification factor of the variable gain amplifier, along with a digital filter and a gain controller to stabilize the amplification factor changes, allowing faster variations without inducing unstable outputs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the amplification factor of the variable gain amplifier is changed to achieve high dynamic range, then the adaptability is improved, but the output stability deteriorates due to the response time of the decimation filter
Solution Approach 1:
The weight change unit pre-adjusts the PDM signal weights by multiplying by the reciprocal of the amplification factor before the decimation filter processes the signal. This preliminary weighting action compensates for the amplification factor change, ensuring that the decimation filter receives a pre-compensated signal that maintains output stability even during rapid gain changes.
Solution Approach 2:
The patent changes the weight parameter of the PDM signal in the weight change unit based on the amplification factor. By dynamically adjusting the weight parameter to be the reciprocal of the amplification factor, the system compensates for gain changes and maintains stable output despite rapid variations in amplification factor.
2Productivity
If the amplification factor is changed rapidly to improve response speed, then the productivity is improved, but the output becomes unstable due to decimation filter response time limitations
Solution Approach 1:
The weight change unit performs preliminary compensation on the PDM signal by applying weight multiplication with the reciprocal of the amplification factor before the signal enters the decimation filter. This advance preparation allows the system to respond rapidly to amplification factor changes without causing output instability, effectively decoupling the response speed from the decimation filter's inherent response time limitation.
3Stability of the object's composition
If the decimation filter response time is reduced to improve stability during gain changes, then the time is improved, but the device complexity increases
Solution Approach 1:
The weight change unit acts as an intermediary component between the variable gain amplifier and the decimation filter. By introducing this intermediate stage that applies weight multiplication, the system achieves rapid stability response without modifying the decimation filter's internal structure or reducing its response time, thus avoiding increased filter complexity.
Data Source
AI summary
An analog-to-digital conversion circuit includes: a variable gain amplifier; a delta-sigma modulator that modulates an output of the variable gain amplifier to a pulse density modulation (PDM) signal; and a decimation filter that downsamples the PDM signal to output a first digital signal that is converted into a multi-bit digital signal. The decimation filter includes: a weight change unit that converts the PDM signal into a second digital signal that is weighted by multiplying a weight of the PDM signal by a reciprocal of an amplification factor of the variable gain amplifier; and a first digital filter that receives the second digital signal as an input, and outputs the first digital signal.