Outphasing Class-E Amplifier With Asymmetrical Shunt Tuning
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Solution Overview
Problem
Conventional power amplifiers face inefficiencies and limitations in achieving maximum power output and maximum efficiency simultaneously, particularly in class E operation, where frequency increases lead to dramatic power output diminishment and non-benign impedances affect waveform control, resulting in bandwidth and power limitations.
Innovation Solution
A method involving two broad-banded, parallel-tuned Class-E power amplifiers combined through a lossless half-wave transmission line combiner with asymmetrical drain inductors, outphasing to induce amplitude modulation, and filtering to enhance efficiency and minimize dissipation across power settings, allowing for high-frequency bandwidth and benign impedance operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If conventional class E power amplifier operation is used, then maximum power output can be achieved, but efficiency deteriorates and thermal dissipation increases
Solution Approach 1:
The power amplifier is divided into two separate class E power amplifiers that operate in parallel, each handling a portion of the signal. This segmentation allows independent optimization of each amplifier's operating conditions, enabling both high power output and high efficiency by distributing the power handling across multiple stages rather than requiring a single amplifier to operate at maximum power continuously.
Solution Approach 2:
The system dynamically adjusts the operating state of the two parallel power amplifiers based on the required output power level. By controlling the amplitude and phase of the input signals to each amplifier, the system can adaptively optimize efficiency across different power output conditions, maintaining near 100% efficiency even when operating below maximum power output.
2Speed
If frequency is increased in class E operation, then bandwidth capability is improved, but power output diminishes dramatically
Solution Approach 1:
By splitting the power amplification function across two parallel class E amplifiers, the system can maintain higher power output at increased frequencies. Each amplifier operates at a frequency optimized for its performance, and their combined output achieves the desired bandwidth capability without the dramatic power loss that would occur in a single amplifier operating at the same high frequency.
Solution Approach 2:
The outputs of two parallel class E power amplifiers are combined to achieve the desired power output and bandwidth performance. This merging of multiple amplifier outputs allows the system to leverage the frequency response characteristics of individual amplifiers while achieving cumulative power output that would be unattainable by a single amplifier at the same frequency.
3Loss of energy
If asymmetrical drain inductors are used for efficiency optimization, then efficiency at high power output is improved, but device complexity increases
Solution Approach 1:
Asymmetrical drain inductors are intentionally used in the parallel class E power amplifier configuration to optimize efficiency at high power output. The asymmetry allows each amplifier to have tailored impedance matching and resonant conditions that maximize efficiency. While this increases circuit complexity compared to symmetrical designs, the efficiency gains at high power output levels justify the additional complexity by reducing energy loss and thermal dissipation.
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
This approach enables efficient power amplification with near 100% efficiency without sacrificing maximum power output, reducing thermal dissipation, and expanding frequency bandwidth, while maintaining acceptable efficiency throughout the outphasing process.
Implementation Method 1
a lossless half-wave transmission line combiner with asymmetrical drain inductors, outphasing to induce amplitude modulation
Implementation Method 2
wherein at 180 degrees of outphasing, each quarterwave transmission line in the combiner reflects all incident power
Implementation Method 3
filtering the amplitude modulated signal
Data Source
AI summary
A method, device and system is disclosed for high efficiency power amplification of a signal over a broad range of output power. Two broad-banded, parallel-tuned class E power amplifiers are combined through a lossless half wave transmission line combiner and configured to operate in an outphased arrangement to permit amplitude modulation. Asymmetrical shunt tuned switches are tuned for efficient amplitude modulation while asymmetrical drain inductors provide enhanced efficiency at outphased conditions over that of a symmetrical circuit. The drain source inductors and transmission components are tuned for maximum efficiency at full power output and for minimum dissipation a zero power output. At zero degrees outphasing, the circuit operates as a conventional Class-E power amplifier. However, at 180 degrees outphasing, each quarterwave line in the combiner reflects back all incident power, permitting the circuit to operate as an unloaded resonant switching circuit.