Dual-Rate Signal Envelope Tracking for Clipping Prevention
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Solution Overview
Problem
Existing signal envelope detection methods in digital signal processing, particularly in Class G amplifier circuits and Dynamic Range Enhancement, face challenges in accurately detecting increases in signal amplitude due to propagation delays, leading to potential signal clipping and inefficiencies in power management.
Innovation Solution
An envelope detection circuit that monitors both the original digital signal at a first sample rate and its interpolated version at a higher sample rate, using absolute value circuitry and an envelope tracker with attack and decay characteristics to provide a more accurate and timely indication of signal envelope changes, thereby reducing the risk of signal clipping and improving power management.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the envelope detector monitors the signal at a point upstream of the amplifier components to enable fast voltage increase, then the response time is improved, but the signal envelope detection accuracy deteriorates due to propagation delays
Solution Approach 1:
The patent applies preliminary action by monitoring the digital signal envelope upstream of the interpolator and DAC, where the signal is available earlier. The envelope detector identifies signal increases before they reach the amplifier stages, allowing the power supply voltage to be increased in advance to prevent clipping, thus resolving the timing accuracy issue caused by propagation delays.
Solution Approach 2:
The patent uses the digital signal itself as an intermediary to detect envelope changes. By monitoring the digital signal envelope upstream and using it to control the power supply voltage, the system avoids the propagation delay issues associated with monitoring analog signals downstream. The digital envelope information serves as a mediator that triggers voltage adjustment before the actual signal reaches the amplifier stages.
2Reliability
If the power supply voltage is increased in advance to prevent signal clipping, then the reliability is improved, but the energy consumption increases
Solution Approach 1:
The patent applies dynamics by making the power supply voltage adjustable and responsive to the actual signal envelope levels. The voltage is increased only when and where needed (when signal increases are detected upstream) and can be reduced when signal levels are low, allowing the system to maintain reliability by preventing clipping while optimizing energy consumption by avoiding sustained high voltage operation.
Solution Approach 2:
The system uses feedback by continuously monitoring the digital signal envelope and using this information to control the power supply voltage. The envelope detector provides feedback about signal levels, which triggers voltage adjustments only when necessary to prevent clipping, thereby maintaining reliability while minimizing energy consumption by avoiding unnecessary high voltage states.
Data Source
AI summary
Methods and apparatus for detection and tracking of a signal envelope. The circuit comprises absolute value circuitry configured to receive data samples and output a first value corresponding to the magnitude of said data samples. An envelope tracker maintains an envelope output value and compares the first value to the current envelope output value and modifies the envelope output value based on said comparison to provide the envelope output value with predetermined attack and decay characteristics. The absolute value circuitry has a first input for receiving a first digital signal at a first sample rate and a second input for receiving an interpolated version of the first digital signal at a second sample rate which is higher than the first sample rate and outputs the first value based on the magnitudes of the samples received at the first input and the samples received at the second input. Using the first digital signal provides an early indication of any increases in signal envelope whereas the second digital signal can allow a more accurate estimation.