Transformer Outphasing Power Combiner for PA Isolation and Efficiency
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Solution Overview
Problem
Conventional outphasing power combiners face challenges in achieving high power efficiency and linearity, leading to power loss and interference between power amplifiers, which affects the spectral and power efficiency of RF signals in wireless communication systems.
Innovation Solution
An outphasing power combiner design that utilizes a transformer and load impedance matching, along with a ripple detector, to combine amplified constant-envelope signals without a dummy load, ensuring impedance matching and minimizing interference between power amplifiers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If an isolating power combiner (Wilkinson combiner) is used, then power loss occurs in a dummy load due to different phases of amplified constant-envelope signals, but if a non-isolating (low-loss) power combiner is used, then power amplifiers interfere with each other reducing linearity
Solution Approach 1:
The patent introduces a coupling network as an intermediary component between the power amplifiers and the power combiner. This coupling network mediates the interaction between amplifiers, providing isolation when needed while allowing efficient power combining, thus resolving the contradiction between power loss and linearity maintenance
2Loss of information
If variable-envelope signals are used for communication, then spectral efficiency is improved, but power efficiency deteriorates compared to constant-envelope signals
Solution Approach 1:
The patent segments the variable-envelope signal into multiple constant-envelope signals with different phases. By processing these segmented signals through separate power amplifiers and then combining them using the outphasing power combiner, the system achieves both spectral efficiency (by maintaining variable envelope information) and power efficiency (by using constant-envelope amplification)
Solution Approach 2:
The patent changes the parameter representation of the signal from direct variable-envelope form to a segmented constant-envelope form with phase variations. This parameter transformation allows the use of efficient constant-envelope power amplifiers while preserving the spectral efficiency benefits of variable-envelope modulation through the phase relationships in the segmented signals
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 enhances power efficiency, reduces battery size in portable devices, and improves linearity, enabling higher data rates and spectral efficiency for wireless communication standards like 802.11 Wireless LAN, cellular LTE, and 5G.
Implementation Method 1
the power combiner includes a transformer
Implementation Method 2
the ripple detector is configured to detect one or more ripples in the combined RF signal
Data Source
AI summary
The outphasing power combiner circuit includes a transformer having a primary coil coupled to a first power amplifier (PA) and a second PA, and a secondary coil. The secondary coil supplies a current to an antenna based on a first direction of a first phase of a first amplified constant-envelope signal in the primary coil with respect to a second phase of a second amplified constant-envelope signal in the primary coil. The outphasing power combiner circuit further includes load impedance coupled between a median point of the primary coil and ground. The load impedance dissipates the current based on a second direction of the first phase of the first amplified constant-envelope signal in the primary coil with respect to the second phase of the second amplified constant-envelope signal in the primary coil, which results in improved power efficiency.