Grid Digitizer Signal Sampling with Hadamard ADC Averaging
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Solution Overview
Problem
Existing digitizer sensors face challenges in enhancing dynamic range and resolution without increasing Integrated Circuit (IC) real estate and Analog to Digital Conversion (ADC) power consumption.
Innovation Solution
A novel averaging ADC approach using a Hadamard Matrix to simultaneously sample summations of signals from multiple sensing channels, dynamically selecting the number of ADCs and sensing lines to mitigate common interference signals, while reducing the number of bits required for ADCs and power consumption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of ADCs and sensing lines is increased to improve dynamic range and resolution, then measurement precision is improved, but IC real estate and power consumption increase
Solution Approach 1:
Multiple sensing lines are combined through Hadamard matrix multiplication to form composite signals that are then sampled by fewer ADCs. This merging approach allows the system to achieve the measurement precision of multiple independent ADCs while using fewer physical ADC components, thereby reducing IC real estate while maintaining resolution.
Solution Approach 2:
The same set of ADCs is used to sample multiple different signal combinations by reconfiguring the Hadamard matrix connections. This multi-functional use of ADCs allows them to effectively perform the work of multiple dedicated ADCs, improving measurement precision without proportionally increasing the number of ADC components and their associated power consumption.
2Measurement precision
If the number of ADCs is increased to improve dynamic range and resolution, then measurement precision is improved, but power consumption increases
Solution Approach 1:
Signal paths from multiple sensing lines are merged through Hadamard matrix multiplication before reaching the ADCs. This combining approach allows fewer ADCs to capture the information that would otherwise require more ADCs, directly reducing the total power consumption while maintaining the dynamic range and resolution benefits.
Solution Approach 2:
The ADCs are configured to serve multiple sensing lines by changing the Hadamard matrix connections between different scan cycles. This universal usage means the same physical ADC components handle the workload of multiple ADCs, reducing total power consumption while achieving improved dynamic range through the combined signal processing.
3Productivity
If all sensing lines are sampled simultaneously to improve measurement speed, then productivity is improved, but interference from common signals increases
Solution Approach 1:
Different groups of sensing lines are assigned different Hadamard matrix connection patterns, creating local variations in how signals are combined. This local differentiation allows simultaneous sampling of multiple lines while enabling the system to distinguish and mitigate common interference signals that appear identically across all lines, as the Hadamard decoding can identify and remove such correlated interference.
Data Source
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AI summary
Signals from a plurality of sensing lines of a grid based digitizer sensor based is combined based on matrix multiplication with a Hadamard Matrix. The combining provides a plurality of signal combinations. Each of the plurality of signal combinations is sampled with a different Analog to Digital Converters (ADC) in a group of ADCs. The sampling is performed simultaneously. The sampled outputs from the group of ADCs are post processed including multiplying an inverse of the Hadamard Matrix with the sampled outputs from the group of ADCs. The presence of an object interacting with the grid based digitizer sensor is detected based on the post processing.