PWM Receiver Offset Cancellation Through Digital Self-Calibration
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Solution Overview
Problem
Existing receiver circuits face challenges with manual calibration processes that are time-consuming and costly, and require additional calibration due to component aging and temperature variations, necessitating an automatic and on-demand calibration solution to maintain performance.
Innovation Solution
A receiver circuit design incorporating a first and second resistor string, transistors, and switches that allow for automatic calibration by measuring voltage differences and adjusting the DC operating point through a calibration process involving the opening and closing of switches to minimize offset, enabling real-time compensation for temperature changes and component aging.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If manual calibration processes are used to remove offset, then offset cancellation is achieved, but the process is time-consuming and costly
Solution Approach 1:
The receiver circuit performs automatic calibration without external intervention by using its own internal components (resistor strings, transistors, switches) to measure and correct offset errors. The system self-adjusts the DC operating point by controlling switches to connect/disconnect calibration circuits based on detected offset conditions.
Solution Approach 2:
The calibration process dynamically adjusts electrical parameters (voltage levels, resistance connections) by controlling switch states to modify the DC operating point. The system changes circuit configuration parameters to compensate for offset errors and maintain optimal receiver performance.
2Measurement precision
If manual calibration is performed at manufacturing, then initial offset is corrected, but additional calibration is needed due to component aging and temperature variation
Solution Approach 1:
The receiver circuit continuously monitors its own performance and automatically recalibrates when needed by controlling switches to adjust the DC operating point, eliminating the need for external calibration interventions throughout the device lifecycle.
Solution Approach 2:
The calibration system transitions from static manual calibration to dynamic automatic calibration, where the circuit continuously adapts to changing conditions (temperature, aging) by real-time switch control and DC operating point adjustment based on detected offset errors.
3Power
If high gain amplifier is used to amplify voltage difference, then signal amplification is improved, but offset errors are magnified causing demodulation errors
Solution Approach 1:
The calibration circuit performs preliminary offset correction by adjusting the DC operating point before the high-gain amplifier processes the signal. Switches are controlled to connect calibration circuits that counteract offset errors, ensuring the amplifier receives a corrected voltage difference and preventing error magnification.
Data Source
AI summary
A method for calibrating the DC operating point of a PWM receiver circuit is disclosed. The PWM receiving circuit includes an envelope detector having a first resistor string, and includes a bias circuit having a second resistor string and a plurality of switches. The second resistor string is coupled between a supply voltage and a reference voltage and functions as a voltage divider. Each switch, when closed, accesses a second voltage at a node of the second resistor string connected to the closed switch. To perform the calibration process, the plurality of switches is closed one at a time, and the second voltage is compared with a first voltage at a first node of the first resistor string. The switch that, when closed, produces the smallest difference between the first voltage and the second voltage remains closed after the calibration process, and is used for demodulating the PWM signal.