Doherty Amplifier Input Splitting for Higher Gain and Efficiency
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Solution Overview
Problem
Conventional Doherty-type power amplifiers face challenges with reduced gain levels and difficulty in linearization, especially in asymmetrical and enhanced asymmetrical designs, which limits their suitability for linear modulation systems and narrows their frequency bandwidth.
Innovation Solution
The proposed solution involves a Doherty amplifier arrangement with a main and auxiliary amplifier path, where the signal preparation unit develops input signals based on a transition threshold, asymmetrically dividing the input signal between the main and auxiliary amplifiers, and biasing the auxiliary amplifier below its turn-on voltage to optimize power division and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a conventional Doherty-type amplifier uses a simple power splitting structure to divide input signal between main and auxiliary amplifiers, then the amplifier achieves high efficiency, but the gain level is reduced
Solution Approach 1:
The patent applies asymmetry by using unequal power division ratios between main and auxiliary amplifiers, and by employing amplifiers with different power handling capabilities. The auxiliary amplifier is sized smaller than the main amplifier, and the power splitter distributes power unevenly to optimize overall gain while maintaining efficiency benefits of the Doherty architecture.
Solution Approach 2:
The patent implements dynamic operation by using variable power division ratios that change with input signal level. The auxiliary amplifier is dynamically activated at different power levels, and the power distribution between main and auxiliary paths is continuously adjusted to maintain optimal gain and efficiency across the operating range.
2Loss of energy
If an asymmetrical Doherty amplifier divides input signal in a pre-set ratio, then the amplifier operates efficiently at specific power levels, but linearity is degraded making linearization difficult
Solution Approach 1:
The patent applies preliminary action through pre-distortion techniques that anticipate and compensate for non-linearities before they occur. The system预先 adjusts the input signal characteristics to counteract the expected distortion from asymmetrical power division, thereby improving linearity while maintaining the efficiency benefits of the asymmetrical Doherty configuration.
3Power
If the auxiliary amplifier is biased at standard operating voltage, then the amplifier provides consistent gain, but power consumption increases and efficiency decreases
Solution Approach 1:
The patent implements dynamic biasing where the auxiliary amplifier operates at different bias points depending on the signal level. At low power levels, the auxiliary amplifier is biased below cutoff to minimize power consumption. As signal level increases, the bias is adjusted to activate the auxiliary amplifier and provide additional gain, optimizing the trade-off between gain consistency and power consumption across the operating range.
Data Source
AI summary
An amplifier having a Doherty-type architecture and a method for operation thereof are provided. The amplifier comprises a main amplifier path comprising a main amplifier, an auxiliary amplifier path comprising an auxiliary amplifier, and an signal preparation unit configured to develop a main amplifier input signal for the main amplifier path and an auxiliary amplifier input signal for the auxiliary amplifier path based on an amplifier input that is to be amplified and a transition threshold associated with the amplifier input. By driving the main and auxiliary amplifiers as a function of the transition threshold, the gain of the Doherty-type amplifier may be increased.