Variable Filter Power Control for EDGE Power Amplifiers
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Solution Overview
Problem
The EDGE system's 8-phase key shifting modulation scheme causes amplitude variation challenges in power amplifiers, requiring linearity and efficient DC to RF conversion, while existing GSM power control systems distort signals due to high feedback loop bandwidth, necessitating a more efficient and economic solution for RF output power control in mobile handset terminals.
Innovation Solution
A radio frequency output power control system with a power amplifier, variable filter, and envelope detection unit that receives a filtered power control signal and trigger signal, allowing for efficient power control and linearization of the power amplifier, enabling consistent performance in both GSM and EDGE modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If a feedback control system with high loop bandwidth is used to meet power ramping requirements, then the rise time requirement is satisfied, but the amplitude modulation is eliminated and the signal is distorted
Solution Approach 1:
The patent extracts the amplitude modulation information from the feedback loop by using envelope detection to separately monitor the RF output power. This allows the feedback control to adjust power without interfering with the AM modulation, thus meeting rise time requirements while preserving signal integrity.
Solution Approach 2:
The patent introduces an envelope detector as an intermediary element that monitors the RF output power and provides separate control signals. This mediator allows the system to control power ramping independently from the AM modulation, preventing signal distortion while achieving fast rise times.
2Reliability
If the Power Amplifier is designed to operate in linear mode for EDGE, then the amplitude variation is handled correctly, but the peak efficiency in GSM mode is reduced
Solution Approach 1:
The patent implements dynamic operation modes for the Power Amplifier, switching between linear mode for EDGE and non-linear mode for GSM. This dynamic adaptation allows the PA to maintain linearity when needed for EDGE while achieving peak efficiency in GSM mode, optimizing both performance and energy consumption.
Solution Approach 2:
The patent changes the operating parameters of the Power Amplifier based on the communication mode. By adjusting the PA's operation point and feedback characteristics dynamically, the system achieves optimal linearity for EDGE and optimal efficiency for GSM, resolving the contradiction between these two requirements.
3Ease of operation
If the existing GSM power control system is used for EDGE, then the power control mechanism is available, but the amplitude modulation is eliminated due to high loop bandwidth
Solution Approach 1:
The patent segments the power control function into separate components: the existing GSM feedback loop handles overall power control, while a new envelope detection path handles AM modulation preservation. This segmentation allows both functions to operate simultaneously without interfering with each other, maintaining signal integrity while providing power control.
Data Source
AI summary
A radio frequency output power control system is disclosed for use in communication systems that use a modulation scheme having a non-constant amplitude envelope. The system includes a power amplifier having a radio frequency input node for receiving a radio frequency input signal, a power control node for receiving a filtered power control signal, and an output for providing an amplified output signal. The system also includes a variable filter that receives a power control signal at a power control input and a receives a trigger signal at a trigger input, and provides a filtered power control signal to the power control node of the power amplifier responsive to the power control signal and the trigger signal.