ET Modulator Load Current Sensing for Open-Loop Predistortion
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Solution Overview
Problem
Existing wireless transmitter systems face inefficiencies due to variations in power amplifier impedance, leading to non-linearity and frequency response degradation in envelope tracking modulators, which are exacerbated by the need for feedback loops and error amplifiers that consume power and increase complexity.
Innovation Solution
The system reconfigures the switching regulator in the envelope tracking modulator to operate as a linear regulator during calibration, allowing for direct measurement of load current and impedance, eliminating the need for feedback loops and error amplifiers, and enabling predistortion for improved frequency response and non-linearity compensation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a feedback loop and error amplifier are added to compensate for power amplifier impedance variations, then frequency response and non-linearity are improved, but power consumption increases and device complexity increases
Solution Approach 1:
The patent extracts and removes the feedback loop and error amplifier components from the envelope tracking modulator. By eliminating these components, the system achieves impedance compensation through an alternative method that does not require continuous feedback, thereby reducing device complexity while maintaining frequency response quality through predistortion techniques.
Solution Approach 2:
The patent applies predistortion to the envelope signal before it reaches the power amplifier. By pre-compensating for the known impedance variations in advance, the system eliminates the need for feedback loops and error amplifiers, thus improving frequency response while reducing device complexity and power consumption.
2Reliability
If a feedback loop and error amplifier are added to compensate for power amplifier impedance variations, then frequency response and non-linearity are improved, but power consumption increases
Solution Approach 1:
The patent removes the error amplifier and feedback loop components that consume significant power. By replacing the feedback-based compensation method with predistortion, the system eliminates the continuous power consumption associated with these active components while maintaining frequency response performance.
Solution Approach 2:
By applying predistortion in advance to the envelope signal, the system compensates for impedance variations without requiring continuous feedback and error amplification. This preliminary action eliminates the need for power-consuming feedback components, thereby reducing overall power consumption while maintaining frequency response quality.
3Productivity
If thin oxide is chosen for switching transistors to allow high switching frequency, then productivity is improved, but reliability decreases due to voltage rating limitations
Solution Approach 1:
The patent segments the transistor structure by combining thin-oxide switching transistors (for high-frequency operation) with thick-oxide cascode transistors (for voltage protection). This segmentation allows each transistor type to operate in its optimal regime, achieving both high switching frequency and high voltage rating capability.
Solution Approach 2:
The patent creates a composite transistor structure using cascode configuration that combines thin-oxide and thick-oxide transistors. This composite structure leverages the high-frequency characteristics of thin-oxide transistors while the thick-oxide cascode transistors provide voltage rating protection, achieving both high productivity and reliability.
Data Source
Figure 1A~1B
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AI summary
An apparatus and method for sensing load current of an envelope tracking (ET) modulator enables load impedance of a power amplifier to be measured. Impairments associated with the load impedance characteristic can be suppressed by calibration and predistortion instead of by feedback (as done in the prior art). The ET modulator provides a switching regulator that can be reconfigured as a linear regulator for the purpose of sensing the load current. This allows the ET modulator to be operated open-loop, thereby eliminating the power consumption overhead resulting from utilization of a loop filter and error amplifier (used in the prior art) and achieving a higher overall efficiency.