Envelope Tracking Amplifier Timing Alignment With Envelope Shaping
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Solution Overview
Problem
Inaccurate timing alignment between RF and envelope paths in radiofrequency power amplifiers leads to distortion, manifesting as degradation in adjacent channel power ratio (ACPR) and error vector magnitude (EVM), particularly problematic in low power applications due to high power consumption and cost associated with complex calibration routines and hardware.
Innovation Solution
An envelope tracking transmitter with an envelope shaping module that adjusts the relative timing alignment between RF and envelope paths using a delay block and a processor to iteratively search for an optimal envelope shaping function, reducing distortion and power consumption by minimizing sensitivity to timing misalignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If complex calibration routines and hardware are used to achieve accurate timing alignment, then distortion is reduced, but power consumption and cost increase significantly
Solution Approach 1:
The patent changes the parameter of envelope shaping function to reduce sensitivity to timing misalignment. By optimizing the envelope shaping parameters, the system achieves acceptable performance without requiring complex calibration hardware or procedures, thereby reducing power consumption while maintaining manufacturing precision requirements.
2Manufacturing precision
If complex calibration routines and hardware are used to achieve accurate timing alignment, then distortion is reduced, but device complexity increases
Solution Approach 1:
The patent modifies the envelope shaping function parameters to make the system less sensitive to timing alignment errors. This approach eliminates the need for complex calibration hardware and routines, directly reducing device complexity while maintaining acceptable manufacturing precision for timing alignment.
3Manufacturing precision
If timing alignment is made more robust through envelope shaping, then sensitivity to delay variations increases, but distortion decreases
Solution Approach 1:
The patent optimizes the envelope shaping function parameters to achieve a balance where distortion is reduced while maintaining reasonable tolerance to delay variations. By carefully selecting the shaping parameters, the system improves manufacturing precision regarding distortion without excessively compromising adaptability to timing variations.
Data Source
AI summary
In one embodiment a transmitter is disclosed. The transmitter comprises an envelope tracking amplifier circuit comprising a power amplifier; a radiofrequency path configured to couple a radiofrequency component of an input signal to an input of the power amplifier; an envelope path configured to modulate a supply voltage of the power amplifier with an envelope signal, the envelope path comprising an envelope shaping module configured to shape an envelope of the input signal using an envelope shaping function to obtain the envelope signal; and a delay block configured to vary the relative timing alignment of the radiofrequency path and the envelope path; storage for an indication of the envelope shaping function to be used by the envelope shaping module; and a processor operable to, iteratively search for a value of a first parameter of a generic envelope shaping function, by applying a test signal to the envelope tracking amplifier circuit and controlling the delay block over a sweep of the relative timing alignments between the radiofrequency path and the envelope path; determining an average measure of distortion of output of the envelope tracking amplifier circuit for the sweep of relative timing alignments; comparing the average measure of distortion of output of the envelope tracking amplifier circuit with an average measure of distortion of the output of the envelope tracking amplifier circuit for a previous iteration; and selecting for the envelope shaping function the value of the first parameter from the previous iteration if the average measure of distortion of the output of the envelope tracking amplifier circuit for the previous iteration is lower than the average measure of distortion of the output of the envelope tracking amplifier circuit determined; and storing an indication of the envelope shaping function with the selected value for the first parameter in the storage.