RMS Detector Offset Calibration for Weak Signal Measurement
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Solution Overview
Problem
The direct current (DC) offset of Room Mean Square (RMS) detector circuits limits the dynamic range of measurable signals, making it difficult to accurately measure weak signals due to comparable RMS values and DC offsets.
Innovation Solution
A method involving determining offset calibrations for differential pairs within the RMS detector circuit, including first and second offset calibrations for individual differential pairs and a third offset calibration for the common mode, using a comparator to compare currents and control back gate biases.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the DC offset of the RMS detector is reduced to improve weak signal measurement, then the measurement precision improves, but the device complexity increases due to the need for multiple differential pairs and calibration circuits
Solution Approach 1:
The RMS detector is divided into multiple independent differential pairs (first, second, third differential pairs), each responsible for specific signal ranges or functions. This segmentation allows each pair to be optimized independently, reducing the DC offset impact on weak signals while maintaining overall detector functionality through modular architecture
Solution Approach 2:
A calibration circuit acts as an intermediary component that measures and compensates for DC offsets in each differential pair. This intermediary system enables the main detector to achieve high precision by separating the offset measurement function from the signal detection function, resolving the contradiction between precision and complexity
2Adaptability or versatility
If multiple differential pairs are used to reduce DC offset impact, then the dynamic range improves, but the device complexity increases
Solution Approach 1:
The detector employs multiple differential pairs segmented into different functional groups: first differential pairs for strong signal detection, second differential pairs for offset calibration, and third differential pairs for weak signal measurement. This segmentation enables the system to adapt to different signal strengths without requiring a single complex circuit design
Solution Approach 2:
The system dynamically switches between different differential pairs based on signal strength. The controller activates appropriate differential pairs according to the input signal level, enabling the detector to adapt its configuration in real-time. This dynamic operation expands the effective dynamic range while avoiding the complexity of having all pairs active simultaneously
3Measurement precision
If offset calibration is performed during signal measurement, then the measurement precision improves, but the productivity decreases due to additional calibration time
Solution Approach 1:
Offset calibration is performed periodically rather than continuously. The controller switches between calibration mode and measurement mode, activating calibration circuits only at scheduled intervals. This periodic action maintains measurement precision through regular offset compensation while minimizing the time spent on calibration, thus preserving productivity
Solution Approach 2:
Offset calibration is performed in advance before actual signal measurement begins. The system completes the calibration sequence during an initial setup phase, establishing accurate offset values that are then used during subsequent measurement operations. This preliminary action ensures high precision during measurement without requiring continuous calibration overhead
Data Source
AI summary
Offset calibration for signal rms measurement is provided. A method includes determining a first offset calibration of a first differential pair of a circuit. The first differential pair comprises a first transistor and a second transistor. The method also includes determining a second offset calibration of a second differential pair of the circuit. The second differential pair comprises a third transistor and a fourth transistor. Further, the method includes, based on the first offset calibration and the second offset calibration, determining a third offset calibration of a common mode.