Input Termination Circuit for Wideband Doherty Amplifier Linearity
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Solution Overview
Problem
Existing amplifiers, particularly Doherty amplifiers, face challenges in achieving high power efficiency and linearity, especially in wideband RF applications, due to poor control over input power distribution and non-linearity issues arising from parameter differences between amplifiers.
Innovation Solution
The implementation of an input termination circuit that reflects a frequency-dependent portion of the input signal back towards the amplifier input, utilizing nonlinear and controllable impedances to optimize power distribution and linearity, particularly in multi-way Doherty amplifiers, by adjusting impedance in response to input voltages, currents, and frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If Doherty amplifiers are used to achieve high power efficiency, then power efficiency is improved, but linearity deteriorates
Solution Approach 1:
An input termination circuit is introduced as an intermediary component between the signal source and the amplifiers. This circuit includes impedance transformation means and reflection means that work together to control the distribution of input power to multiple amplifiers, thereby improving linearity while preserving the high efficiency architecture of Doherty amplifiers.
Solution Approach 2:
The input termination circuit dynamically adjusts impedance parameters based on the operating state. The impedance transformation means changes the input impedance seen by the signal source, and the reflection means adjusts the amount of signal reflected back to the amplifier input, thereby optimizing power distribution across different power levels to improve linearity.
2Power
If amplifier power is increased for high power applications, then output power is improved, but linearity deteriorates
Solution Approach 1:
The amplifier system is divided into multiple parallel amplifiers (carrier amplifier and peaking amplifiers) that operate at different power levels. The input termination circuit segments the input power distribution among these amplifiers, with the reflection means directing appropriate portions of power to each amplifier based on the overall power level, thereby maintaining linearity across the full power range.
Solution Approach 2:
The input termination circuit provides dynamic control over power distribution. As the overall amplifier output power changes, the impedance transformation and reflection mechanisms adjust in real-time to optimize the power split among amplifiers, ensuring linear operation at both low and high power levels.
3Power
If multiple amplifiers are used in parallel for high power output, then output power is improved, but linearity deteriorates due to parameter differences
Solution Approach 1:
The input termination circuit implements a feedback mechanism where the impedance transformation means senses the operating conditions and the reflection means adjusts the signal distribution accordingly. This feedback loop compensates for parameter differences between amplifiers by dynamically adjusting the power split, thereby maintaining linearity across all amplifiers even when they have manufacturing variations.
4Device complexity
If conventional input power distribution is used, then device complexity is minimized, but linearity deteriorates at frequency edges
Solution Approach 1:
An input termination circuit is introduced as an intermediary component between the signal source and the amplifiers. This circuit includes impedance transformation means and reflection means that work together to control the distribution of input power to multiple amplifiers, thereby improving linearity while preserving the high efficiency architecture of Doherty amplifiers.
Solution Approach 2:
The input termination circuit dynamically adjusts impedance parameters based on the operating state. The impedance transformation means changes the input impedance seen by the signal source, and the reflection means adjusts the amount of signal reflected back to the amplifier input, thereby optimizing power distribution across different power levels to improve linearity.
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 enhances the linearity and efficiency of amplifiers by providing improved control over input power distribution, especially at frequency edges, and maintains high power efficiency across a wide frequency band.
Implementation Method 1
an input termination circuit coupled to a input of the second amplifier, the input termination circuit configured to reflect a frequency dependent portion of an input signal back toward an input of the amplifier device
Data Source
AI summary
The embodiments described herein provide wideband highly asymmetrical power efficient amplifier device that include a compact input power distribution network with input termination circuit. The input termination circuit is configured to provide control of the power distribution at the amplifier input. In one embodiment, the input termination circuit is configured to generate and reflect a frequency dependent portion of an input signal back toward the amplifier device inputs. This input reflection controls the input power distribution and shape of time domain input signal in a way that can affect amplifier device efficiency and linearity.