ASK Receiver Offset Compensation for Accurate PWM Demodulation
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Solution Overview
Problem
Existing inter-chip data communication systems face challenges in accurately recovering PWM signals due to offset voltages between amplifier inputs, especially under temperature changes and start-up/standby conditions, which affects demodulation accuracy and requires manual calibration or additional components.
Innovation Solution
A self-calibration technique using a dynamic analog approach for offset compensation in ASK receivers, integrated within CMOS technology, that dynamically adjusts for offset drifts without external components, enabling automatic and accurate calibration during start-up, operation, and standby phases without increasing power consumption or area occupation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If manual calibration or additional components are used to compensate for offset voltages, then demodulation accuracy is improved, but device complexity and manufacturing cost increase
Solution Approach 1:
The receiver circuit automatically compensates for offset voltages through self-calibration during normal operation without requiring external calibration equipment or manual adjustment. The circuit uses its own operational signals to generate compensation voltages that cancel out the offset effects, making the system self-calibrating and eliminating the need for additional calibration components.
Solution Approach 2:
The circuit dynamically adjusts compensation parameters (compensation voltages) based on detected offset conditions. By changing the compensation voltage parameters in response to measured offset voltages, the system maintains accurate demodulation across varying operating conditions without requiring complex fixed compensation circuits.
2Measurement precision
If additional offset compensation components are added, then offset compensation capability is improved, but area occupation increases
Solution Approach 1:
The offset compensation function is merged with the existing amplifier and demodulation circuitry. The compensation voltages are generated and applied within the same circuit block that performs the main signal processing, eliminating the need for separate compensation components and reducing overall circuit area while maintaining compensation capability.
3Adaptability or versatility
If dynamic offset compensation is implemented, then adaptability to temperature changes is improved, but power consumption increases
Solution Approach 1:
The circuit continuously monitors the offset voltage through feedback from the amplifier inputs and automatically adjusts the compensation voltages in real-time. This feedback mechanism enables the system to adapt to temperature drift and other environmental changes dynamically, maintaining accurate demodulation without requiring excessive power for active compensation components.
Data Source
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AI summary
A receiver circuit for use, for instance, in interchip data communication in the automotive sector comprises an envelope detector (M1, M2, RL1, CED) configured to receive (RX1) an on-off keying, OOK signal modulated over a RF carrier. A differential stage (121, 122, RL2) has a first input (VA) coupled to the envelope detector (M1, M2, RL1, CED) and a second input (VB) configured to receive a reference signal. A comparator (16) is coupled (14) to first (C) and second (D) output nodes of the differential stage (121, 122, RL2) produces a PWM-modulated signal (PWMOUT) having on and off times. Offset compensation circuitry comprises a first switch (S1,Φ1) to short-circuit the input to the envelope detector (M1, M2, RL1, CED), a storage capacitor (CH) coupled to the second input (VB) of the differential stage (121, 122, RL2) and a second switch (S1,Φ2) to feed back to the storage capacitor (CH) a signal (18) indicative of the difference between the first (C) and the second (D) output nodes of the differential stage (121, 122, RL2), and a third switch (S3,Φ1) to short-circuit the input to the comparator (16) . Logic circuitry (100) activates the offset compensation circuitry in a sequence of phases comprising a start-up phase (SUP) and at least one standby phase (STBY) wherein the first (S1,Φ1), second (S2,Φ2) and third (S3,Φ1) switches are made conductive in the absence of the PWM-modulated signal (PWMOUT), and a working phase (WP) alternating with the start-up phase (SUP) or the at least one standby phase (STBY) in the presence of the PWM-modulated signal (PWMOUT) wherein the first (S1,Φ1), second (S2,Φ2) and third (S3,Φ1) switches are made conductive during off times (T2) of the PWM-modulated signal (PWMOUT).