Switchable RF Power Amplifier Matching for Back-Off Efficiency
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Solution Overview
Problem
Power amplifiers in cellular handsets are inefficient at reduced output power levels, leading to wasted battery power and reduced talk time due to low DC-to-RF conversion efficiency.
Innovation Solution
A switchable power amplifier circuitry with a power amplification section and matching network that can operate in high power and low power modes, using complementary control signals and a switchable inductor to adjust impedance, optimizing DC-to-RF conversion efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the power amplifier operates at maximum output power, then DC-to-RF conversion efficiency is optimized, but the amplifier cannot meet the practical requirement of operating at various back-off power levels with maintained efficiency
Solution Approach 1:
The power amplifier is divided into multiple parallel amplifier paths (first and second output stage power amplifiers) that can be independently controlled. Each path is optimized for different power levels, allowing the system to segment the operating range and maintain high efficiency across various back-off conditions by activating only the necessary paths.
Solution Approach 2:
The matching network incorporates switchable inductors that dynamically adjust the output impedance based on the operating mode. The circuit transitions between different impedance configurations (first matching network for high power, second matching network for low power) to optimize efficiency at each operating point, making the amplifier adaptive rather than static.
2Loss of energy
If the power amplifier is designed for high efficiency at maximum power, then efficiency is improved, but power consumption increases and talk time is reduced when operating at back-off levels
Solution Approach 1:
The circuit changes key operating parameters (impedance, amplifier activation state) based on the required output power level. By detecting the operating mode and adjusting the matching network accordingly, the amplifier maintains optimal DC-to-RF conversion efficiency whether operating at high or low power, directly reducing wasted battery power and extending talk time.
3Device complexity
If a single matching network is used for the power amplifier, then device complexity is reduced, but DC-to-RF conversion efficiency cannot be optimized for both high power and low power modes
Solution Approach 1:
The matching network is designed as a universal structure that can perform multiple functions by switching between different inductor configurations. The same matching network topology serves both high-power and low-power modes, achieving multi-functionality without requiring completely separate matching networks for each mode, thus balancing complexity and efficiency.
Data Source
AI summary
Embodiments of circuits, apparatuses, and systems for a switchable radio frequency (RF) power amplifier are disclosed. Some embodiments include a matching network configured to alternatively provide a first load impedance or second load impedance based at least in part on an amplification mode of a power amplification section. Other embodiments may be described and claimed.