LINC Transmitter Bridge Circuit for Combiner-Free RF Efficiency
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Solution Overview
Problem
Conventional LINC transmitters suffer from efficiency losses due to combiner inefficiencies, and while Asymmetric Multilevel Outphasing (AMO) transmitters offer higher efficiency, they still have relatively low overall efficiency, necessitating an RF transmitter with improved efficiency.
Innovation Solution
The implementation of restoration and cancellation circuits, including inductor-capacitor (LC) circuits and a bridge circuit, which provide a common mode impedance lower than differential impedance, increasing peak efficiency and reducing power consumption by controlling harmonic content and impedance variation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional LINC transmitter uses a combiner to combine signals from multiple power amplifiers, then the transmitter can achieve high efficiency through parallel power amplification, but the combiner introduces efficiency losses and increases device complexity
Solution Approach 1:
The patent extracts and eliminates the combiner component from the transmitter architecture. Instead of using multiple power amplifiers with a combiner, the invention uses a single power amplifier that directly generates the desired output signal, removing the source of combiner losses and simplifying the overall device structure while maintaining high efficiency
Solution Approach 2:
The patent segments the signal processing function from the power amplification function. By using a single power amplifier that receives pre-processed signals (with envelope and phase information already separated), the system achieves efficient amplification without requiring multiple amplifiers and their associated combining hardware
2Loss of energy
If an Asymmetric Multilevel Outphasing (AMO) transmitter is used to improve efficiency, then power consumption is reduced through intelligent power switching, but the overall efficiency remains relatively low compared to ideal systems
Solution Approach 1:
The patent changes the operating parameters of the power amplifier by optimizing the impedance matching network to provide different impedance values at different signal power levels. This allows the single power amplifier to operate efficiently across a wide dynamic range without requiring multiple amplifiers or complex power switching, thereby improving overall efficiency while avoiding the complexity of AMO systems
3Power
If power amplifiers operate at high power levels to increase output, then the transmitter achieves higher signal strength, but efficiency losses increase due to impedance variation and harmonic distortion
Solution Approach 1:
The patent implements a dynamic impedance matching network that automatically adjusts the impedance presented to the power amplifier based on the instantaneous signal power level. At high power levels, the network optimizes the impedance to maximize power transfer and efficiency, while at low power levels it maintains proper matching conditions. This dynamic adaptation allows the transmitter to maintain high efficiency across the entire power range without the losses associated with static impedance matching
Data Source
AI summary
A radio frequency (RF) transmitter is provided. The RF transmitter includes first and second drivers that are configured to receive first and second sets of complementary RF signals. Restoration circuits are coupled to the first and second drivers, and a bridge circuit is coupled to the first and second restoration circuits. By having the restoration circuits and the bridge circuit, a common mode impedance and a differential impedance can be provided, where the common mode impedance is lower than the differential impedance.