Optical Encoder Phase Shifter Circuit for Signal Phase Calibration
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Solution Overview
Problem
Existing incremental optical encoders face issues with phase deviations between incremental signals and index signals, leading to inaccurate position determination due to spatial deviations and imperfect phase offsets.
Innovation Solution
A phase shifter circuit with cascaded resistor strings and amplifiers is employed to calibrate phase deviations by selecting appropriate switches and adjusting gain to correct phase shifts and attenuations, using a combination of switching and sub-switching devices to align incremental and index signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If components of the optical encoder are arranged with spatial deviation, then the index signal can be generated, but the index signal has phase deviation from incremental AB signals
Solution Approach 1:
The patent changes the electrical parameter (phase shift) to compensate for the mechanical parameter (spatial deviation). By adjusting the phase shift amount through resistor string selection, the system compensates for spatial arrangement errors without requiring perfect mechanical alignment.
Solution Approach 2:
The patent replaces the mechanical alignment system with an electrical phase shift system. Instead of relying on precise physical positioning of components, the system uses electrical signals and phase shifting to achieve accurate position determination.
2Measurement precision
If the CHA and CHB signals are generated without phase calibration, then the circuit is simple, but the phase offset is not exactly 90 degrees
Solution Approach 1:
The patent makes the phase shift amount adjustable rather than fixed. By allowing dynamic selection of different phase shift amounts through switchable resistor strings, the system can adapt to different spatial deviations while maintaining a manageable circuit structure.
Solution Approach 2:
The patent divides the phase adjustment into discrete segments using multiple resistor strings with different phase shift amounts. This segmentation allows the system to achieve precise phase calibration through combination of discrete phase shift steps rather than requiring continuous adjustment.
3Measurement precision
If multiple resistor strings with different phase shift amounts are used, then phase deviation can be calibrated, but the device complexity increases
Solution Approach 1:
The patent designs the resistor strings to be identical in structure but different in phase shift characteristics. This universal design approach allows the same circuit topology to serve multiple phase calibration needs, reducing design complexity while maintaining calibration accuracy.
Solution Approach 2:
The patent changes only the essential parameter (phase shift amount) while keeping the resistor string structure identical. This approach allows precise phase calibration through parameter variation rather than structural modification, simplifying the overall device design.
Data Source
AI summary
There is provided a phase shifter circuit of an optical encoder. The phase shifter circuit receives a first signal, a second signal, a third signal and a fourth signal sequentially having a 90-degree phase shift, and includes a first cascaded resistor string, a second cascaded resistor string, a third cascaded resistor string and a fourth cascaded resistor string. The first, second, third and fourth cascaded resistor strings respectively delay the first, third, second and fourth signals by selecting a switch connected at a tap-out node of the first, second, third and fourth cascaded resistor strings to correct phase deviations between incremental signals and an index signal and/or between incremental signals.