Multiplexed Signal Conditioning for Multi-Sensor A/D Conversion
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing signal conditioning methods for AC sensor signals, such as LVDTs and resolvers, are costly, large, and power-intensive due to the use of separate anti-aliasing filters and demodulators for each signal, and introduce errors from inherent variations between circuits.
Innovation Solution
A signal conditioning circuit that time-shares anti-aliasing filters and A/D converters using multiplexers, allowing multiple sensors to share a single A/D converter, reducing size, cost, and power consumption, and using digital processing to calculate vector magnitudes and angles.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate anti-aliasing filters and demodulators are used for each AC sensor signal, then signal processing accuracy is maintained, but circuit size, cost, and power consumption increase
Solution Approach 1:
The patent combines multiple separate anti-aliasing filters into a single shared filter that processes multiple sensor signals sequentially through time-division multiplexing. This merging approach reduces the total number of filter components, thereby decreasing circuit size while maintaining signal processing accuracy through careful timing and switching control.
Solution Approach 2:
The patent implements a universal anti-aliasing filter and demodulator that can handle multiple different sensor signals by switching between them in time-division manner. This multi-functional design allows a single circuit to perform the work of multiple dedicated circuits, reducing overall device complexity while preserving measurement precision for each sensor channel.
2Measurement precision
If separate anti-aliasing filters and demodulators are used for each AC sensor signal, then signal processing accuracy is maintained, but power consumption increases
Solution Approach 1:
The patent merges multiple power-consuming filter and demodulator circuits into a single shared resource that is activated sequentially for each sensor channel. This consolidation dramatically reduces total power consumption since the same hardware is reused across multiple channels rather than being simultaneously active for each channel.
Solution Approach 2:
The patent employs periodic time-division multiplexing where the shared anti-aliasing filter and demodulator are activated in periodic cycles for each sensor channel. This periodic activation ensures that power is consumed only when needed for each channel rather than continuously, maintaining measurement precision while reducing overall power consumption.
3Ease of manufacture
If separate circuits are used for each sensor signal, then signal processing is simplified, but inherent variations between circuits introduce errors
Solution Approach 1:
The patent merges the filter and demodulator functions into a single shared circuit that processes all sensor signals. This eliminates the problem of circuit-to-circuit variations because there is only one filter and one demodulator, ensuring that all signals undergo identical processing and introducing no additional errors from component mismatches.
Solution Approach 2:
The patent ensures homogeneous signal processing by routing all sensor signals through the same anti-aliasing filter and demodulator circuitry. This homogeneity guarantees that all channels experience identical gain, phase, and frequency response characteristics, eliminating errors that would arise from inherent variations between separate circuits.
Data Source
AI summary
A signal conditioning circuit time share multiplexes anti-aliasing filters and an A/D converter. A plurality of first tier multiplexers each time share multiplex one of a plurality of antialiasing filters between a plurality of AC or baseband input signals from a plurality of sensors. A second tier multiplexer selects its inputs from the outputs of the first tier multiplexers. The output of the second tier multiplexer feeds a high speed A/D converter. Thus, the A/D converter is time share multiplexed by the second tier multiplexer. In this manner, a plurality of sensors can share a single A/D converter. After allowing a settling time for the multiplexers and antialiasing filters, a plurality of samples of the input signals are taken, such as for one period. The samples of each AC input signal are multiplied by a sine vector and a cosine vector. The product vectors are then each averaged and the root mean square of the two averages yields the magnitude of the input signal. Mechanical angle of the input signal can be determined based upon the sign of the sine and cosine product vector averages.