Envelope Tracking Control for Smooth Transmitter Power Transitions
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Solution Overview
Problem
Conventional envelope tracking transmitters experience spectral anomalies and power discontinuities due to step-wise gain adjustment in the ET signal path before the APC loop stabilizes, leading to unwanted spectral distortion during power transitions.
Innovation Solution
A transmitter design that incorporates a function block with a lookup table and calibration routine, guided by the APC loop's gain and bias signals, to synchronize and adjust the envelope tracking signal path, eliminating the need for interim scaling and ensuring smooth power transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If step-wise gain adjustment is applied to the ET signal path before the APC loop stabilizes, then power management efficiency is improved, but spectral anomalies and distortion occur
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing gain adjustment values in a lookup table during a calibration routine. The APC loop characteristics are measured and used to pre-determine the correct gain adjustments for the ET path, eliminating the need for real-time calculations and preventing spectral anomalies during actual operation.
Solution Approach 2:
The patent uses feedback by implementing a calibration routine that measures the actual APC loop response and uses this information to adjust the lookup table values. The system continuously monitors the interaction between the APC loop and ET path, and refines the gain adjustment strategy based on observed performance, thereby eliminating spectral distortion.
2Power
If gain scaling is applied in the ET signal path during power transitions, then power amplifier efficiency is improved, but power discontinuities occur
Solution Approach 1:
The calibration routine performs preliminary measurements of the APC loop response to predetermined test signals. Based on these measurements, the lookup table is pre-configured with gain values that ensure continuous power delivery during transitions, preventing power discontinuities while maintaining amplifier efficiency.
Solution Approach 2:
The patent changes the parameter of gain adjustment from fixed step-wise values to dynamically calculated values based on APC loop feedback. The lookup table stores pre-calculated gain factors that are applied to the ET signal path, ensuring smooth power transitions without discontinuities while maintaining optimal amplifier efficiency.
3Speed
If lookup table with pre-calculated values is used for envelope shaping, then processing speed is improved, but spectral distortion occurs without proper calibration
Solution Approach 1:
The patent performs preliminary calibration by measuring the actual APC loop response to test signals and using this information to pre-fill the lookup table with corrected gain values. This preliminary action ensures that the fast lookup table access does not produce spectral distortion, combining speed with accuracy.
Solution Approach 2:
The calibration routine uses feedback from the APC loop to adjust the lookup table values. The system measures the actual response and refines the pre-calculated values accordingly, ensuring that the fast processing provided by the lookup table does not result in spectral distortion during normal operation.
Data Source
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AI summary
A system and method for controlling envelope tracking in a transmitter with closed loop power control, including up-converting and pre-amplifying a baseband signal to a pre-amplified RF signal, amplifying the pre-amplified RF signal, converting the envelope of the baseband signal into a shaped envelope signal, adjusting the gain of the pre-amplified RF signal, and adjusting the shape of the envelope signal in response to changes in the gain of the pre-amplified RF signal.