Digitally Scalable Transformer Combining for RF Power Back-Off
Solution Overview
Problem
CMOS power amplifiers face inefficiencies at back-off power levels due to power dissipation in non-active transformer sections, reducing their effectiveness in applications requiring high efficiency and battery life, such as WiFi, WiMAX, and LTE.
Innovation Solution
A digitally configurable transformer with strategically placed switches that dynamically enable or disable power amplifier sections to maintain efficiency across a wide range of power levels, avoiding power dissipation in inactive sections by using tri-stating or grounding to achieve power back-off without reducing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If transformer combining is used to increase output power, then peak power is improved, but efficiency at back-off power levels deteriorates
Solution Approach 1:
The transformer is divided into multiple independently controllable sections, each corresponding to a power amplifier section. This segmentation allows individual sections to be enabled or disabled based on the required output power level, preventing power dissipation in inactive sections while maintaining efficient operation at back-off power levels.
Solution Approach 2:
The transformer configuration is made dynamically reconfigurable through digitally controllable switches that can change the transformer's topology in real-time. This dynamic reconfiguration allows the system to adapt the transformer structure to match the active power amplifier sections, optimizing both peak power output and back-off efficiency by eliminating unnecessary electromagnetic coupling in inactive sections.
2Loss of energy
If power amplifier sections are disabled to reduce power consumption, then energy loss is reduced, but electromagnetic relationships within the transformer are disrupted
Solution Approach 1:
The transformer configuration is made dynamically reconfigurable through digitally controllable switches that can change the transformer's topology in real-time. This dynamic reconfiguration allows the system to adapt the transformer structure to match the active power amplifier sections, optimizing both peak power output and back-off efficiency by eliminating unnecessary electromagnetic coupling in inactive sections.
Solution Approach 2:
The system changes the electrical parameters of the transformer by reconfiguring the switch states to alter the effective turns ratio and coupling relationships. This parameter change allows the transformer to maintain proper impedance matching and electromagnetic relationships even when the number of active power amplifier sections changes, ensuring reliable operation across different power levels.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution achieves high average efficiency and extended battery life by maintaining efficient power combining at various power levels, including back-off, through the use of switches that manage electromagnetic relationships within the transformer, reducing unwanted power loss and maintaining matching network integrity.
Implementation Method 1
a first inductor of the primary winding is adjacent to a first inductor of the secondary winding such that a first electromagnetic field couples the first inductor of the primary winding to the first inductor of the secondary winding
Data Source
AI summary
A digitally configurable transformer that performs switched transformer combining is disclosed. The flexible transformer includes switches that are dynamically configurable to efficiently combine RF power from power amplifier cores to achieve different power levels. The disclosed transformer is efficient at a broad range of power levels, leading to high power output efficiency. The transformer may be part of any power amplifier design that uses the transformer for power combining.