Doherty Amplifier TIP Cells for Adjustable Alpha at High PAPR
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Solution Overview
Problem
Conventional Doherty amplifiers have a constant alpha factor, which is not beneficial across different modulation schemes used in cellular telephone systems and other wireless transmission systems, leading to poorer power added efficiency (PAE) at high peak-to-average power ratios.
Innovation Solution
A Doherty amplifier circuit with a tunable impedance and phase (TIP) circuit is introduced, allowing for an adjustable alpha factor by replacing the conventional quarter wave transmission line impedance inverter, maintaining the phase of the carrier amplifier at 90° with minimal phase variation, and enabling adjustment of the impedance ZINV to optimize PAE for various modulation schemes and power levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a constant alpha factor is used in conventional Doherty amplifiers, then the circuit structure is simple, but power added efficiency deteriorates at high peak-to-average power ratios
Solution Approach 1:
The patent applies the dynamics principle by making the alpha factor adjustable rather than constant. The impedance inverter is replaced with a tunable impedance and phase circuit that can dynamically adjust the alpha factor based on the modulation scheme and power level requirements, thereby improving power added efficiency across different operating conditions while managing circuit complexity through controlled tunability.
2Loss of energy
If a fixed Doherty amplifier is used for all modulation schemes, then the device complexity is low, but power added efficiency deteriorates across different peak-to-average power ratios
Solution Approach 1:
The patent applies the parameter changes principle by enabling adjustment of the alpha factor parameter to match different modulation schemes. The tunable impedance and phase circuit allows the alpha factor to be optimized for specific peak-to-average power ratios associated with different modulation schemes, thereby improving power added efficiency across diverse wireless communication standards while maintaining a relatively simple base circuit architecture.
Data Source
AI summary
A Doherty amplifier circuit having a tunable impedance and phase (“TIP”) circuit to provide an adjustable alpha factor, which allows for a selection of power added efficiency (PAE) curves that are useful for applications having different modulations or to meet other criteria. Embodiments include a Doherty amplifier having a TIP circuit that provides for tunability of the impedance ZINV (resulting in an adjustable alpha factor) while maintaining the phase of the output of the carrier amplifier at 90° (for a selected polarity)±a low phase variation. Embodiments of the TIP circuit include one or more series-connected TIP cells comprising at least one TIP circuit combined with a tunable phase adjustment circuit. In operation, when the impedance of a TIP cell is adjusted, adjustments within the cell are also made to provide a phase shift correction back towards 90° (at the selected polarity).